As a graduate student and short-term postdoctoral fellow at the University of Toronto I studied genetic networks that regulate cell viability in the nematode worm Caenorhabditis elegans (C. elegans) and in the single-celled eukaryotes S. cerevisiae and S. pombe, respectively. As a postdoctoral fellow, I demonstrated that the small molecule erastin inhibits the membrane cystine/glutamate transporter system xc-, depletes the cell of glutathione and activates a novel iron-dependent, oxidative cell death pathway termed ferroptosis. Currently a major goal of my lab is to understand the interaction between intracellular metabolism and cell death. Our research program integrates techniques and model systems including small molecule and proteomic screening, biochemical analysis of protein function and model organism genetics.

Academic Appointments

Professional Education

  • B.Sc., Laurentian University, Behavioral Neuroscience (2000)
  • Ph.D., University of Toronto, Molecular and Medical Genetics (2007)

Current Research and Scholarly Interests

My lab is interested in the relationship between cell death and metabolism. Using techniques drawn from many disciplines my laboratory is investigating how perturbation of intracellular metabolic networks can result in novel forms of cell death, such as ferroptosis. We are interested in applying this knowledge to find new ways to treat diseases characterized by insufficient (e.g. cancer) or excessive (e.g. neurodegeneration) cell death.

2023-24 Courses

Stanford Advisees

Graduate and Fellowship Programs

All Publications

  • Quick tips for interpreting cell death experiments. Nature cell biology Dixon, S. J., Lee, M. J. 2023

    View details for DOI 10.1038/s41556-023-01288-5

    View details for PubMedID 37985871

    View details for PubMedCentralID 3656927

  • Lipid Quality Control and Ferroptosis: From Concept to Mechanism. Annual review of biochemistry Li, Z., Lange, M., Dixon, S. J., Olzmann, J. A. 2023


    Cellular quality control systems sense and mediate homeostatic responses to prevent the buildup of aberrant macromolecules, which arise from errors during biosynthesis, damage by environmental insults, or imbalances in enzymatic and metabolic activity. Lipids are structurally diverse macromolecules that have many important cellular functions, ranging from structural roles in membranes to functions as signaling and energy-storage molecules. As with other macromolecules, lipids can be damaged (e.g., oxidized), and cells require quality control systems to ensure that nonfunctional and potentially toxic lipids do not accumulate. Ferroptosis is a form of cell death that results from the failure of lipid quality control and the consequent accumulation of oxidatively damaged phospholipids. In this review, we describe a framework for lipid quality control, using ferroptosis as an illustrative example to highlight concepts related to lipid damage, membrane remodeling, and suppression or detoxification of lipid damage via preemptive and damage-repair lipid quality control pathways. Expected final online publication date for the Annual Review of Biochemistry , Volume 93 is June 2024. Please see for revised estimates.

    View details for DOI 10.1146/annurev-biochem-052521-033527

    View details for PubMedID 37963395

  • Sensitization of cancer cells to ferroptosis coincident with cell cycle arrest. Cell chemical biology Rodencal, J., Kim, N., He, A., Li, V. L., Lange, M., He, J., Tarangelo, A., Schafer, Z. T., Olzmann, J. A., Long, J. Z., Sage, J., Dixon, S. J. 2023


    Ferroptosis is a non-apoptotic form of cell death that can be triggered by inhibiting the system xc- cystine/glutamate antiporter or the phospholipid hydroperoxidase glutathione peroxidase 4 (GPX4). We have investigated how cell cycle arrest caused by stabilization of p53 or inhibition of cyclin-dependent kinase 4/6 (CDK4/6) impacts ferroptosis sensitivity. Here, we show that cell cycle arrest can enhance sensitivity to ferroptosis induced by covalent GPX4 inhibitors (GPX4i) but not system xc- inhibitors. Greater sensitivity to GPX4i is associated with increased levels of oxidizable polyunsaturated fatty acid-containing phospholipids (PUFA-PLs). Higher PUFA-PL abundance upon cell cycle arrest involves reduced expression of membrane-bound O-acyltransferase domain-containing 1 (MBOAT1) and epithelial membrane protein 2 (EMP2). A candidate orally bioavailable GPX4 inhibitor increases lipid peroxidation and shrinks tumor volumes when combined with a CDK4/6 inhibitor. Thus, cell cycle arrest may make certain cancer cells more susceptible to ferroptosis in vivo.

    View details for DOI 10.1016/j.chembiol.2023.10.011

    View details for PubMedID 37963466

  • CDKN2A DELETION REMODELS LIPID METABOLISM TO PRIME GLIOBLASTOMA FOR FERROPTOSIS Minami, J., Morrow, D., Bayley, N., Fernandez, E., Salinas, J., Tse, C., Zhu, H., Su, B., Sammarco, A., Liau, L., Graeber, T., Williams, K., Cloughesy, T., Dixon, S., Bensinger, S., Nathanson, D. OXFORD UNIV PRESS INC. 2023
  • Death-seq identifies regulators of cell death and senolytic therapies. Cell metabolism Colville, A., Liu, J. Y., Rodriguez-Mateo, C., Thomas, S., Ishak, H. D., Zhou, R., Klein, J. D., Morgens, D. W., Goshayeshi, A., Salvi, J. S., Yao, D., Spees, K., Dixon, S. J., Liu, C., Rhee, J. W., Lai, C., Wu, J. C., Bassik, M. C., Rando, T. A. 2023


    Selectively ablating damaged cells is an evolving therapeutic approach for age-related disease. Current methods for genome-wide screens to identify genes whose deletion might promote the death of damaged or senescent cells are generally underpowered because of the short timescales of cell death as well as the difficulty of scaling non-dividing cells. Here, we establish "Death-seq," a positive-selection CRISPR screen optimized to identify enhancers and mechanisms of cell death. Our screens identified synergistic enhancers of cell death induced by the known senolytic ABT-263. The screen also identified inducers of cell death and senescent cell clearance in models of age-related diseases by a related compound, ABT-199, which alone is not senolytic but exhibits less toxicity than ABT-263. Death-seq enables the systematic screening of cell death pathways to uncover molecular mechanisms of regulated cell death subroutines and identifies drug targets for the treatment of diverse pathological states such as senescence, cancer, and fibrosis.

    View details for DOI 10.1016/j.cmet.2023.08.008

    View details for PubMedID 37699398

  • Author Correction: Lipid droplets and peroxisomes are co-regulated to drive lifespan extension in response to mono-unsaturated fatty acids. Nature cell biology Papsdorf, K., Miklas, J. W., Hosseini, A., Cabruja, M., Morrow, C. S., Savini, M., Yu, Y., Silva-García, C. G., Haseley, N. R., Murphy, L. M., Yao, P., de Launoit, E., Dixon, S. J., Snyder, M. P., Wang, M. C., Mair, W. B., Brunet, A. 2023

    View details for DOI 10.1038/s41556-023-01220-x

    View details for PubMedID 37567997

  • Protocol for detection of ferroptosis in cultured cells. STAR protocols Murray, M. B., Leak, L. B., Lee, W. C., Dixon, S. J. 2023; 4 (3): 102457


    Mammalian cells can die by apoptosis or by one of several non-apoptotic mechanisms, such as ferroptosis. Here, we present a protocol to distinguish ferroptosis from other cell death mechanisms in cultured cells. We describe steps for seeding cells, administering mechanism-specific cell death inducers and inhibitors, and measuring cell death and viability. We then detail the use of molecular markers to verify mechanisms of cell death. This protocol can be used to identify and distinguish ferroptosis in 2D and 3D cultures. For complete details on the use and execution of this protocol, please refer to Ko, et al. (2019),1 Magtanong, et al. (2022),2 and Armenta, et al. (2022).3.

    View details for DOI 10.1016/j.xpro.2023.102457

    View details for PubMedID 37556320

  • A Cell Cycle-Dependent Ferroptosis Sensitivity Switch Governed by EMP2. bioRxiv : the preprint server for biology Rodencal, J., Kim, N., Li, V. L., He, A., Lange, M., He, J., Tarangelo, A., Schafer, Z. T., Olzmann, J. A., Sage, J., Long, J. Z., Dixon, S. J. 2023


    Ferroptosis is a non-apoptotic form of cell death characterized by iron-dependent lipid peroxidation. Ferroptosis can be induced by system xc- cystine/glutamate antiporter inhibition or by direct inhibition of the phospholipid hydroperoxidase glutathione peroxidase 4 (GPX4). The regulation of ferroptosis in response to system xc- inhibition versus direct GPX4 inhibition may be distinct. Here, we show that cell cycle arrest enhances sensitivity to ferroptosis triggered by GPX4 inhibition but not system xc- inhibition. Arrested cells have increased levels of oxidizable polyunsaturated fatty acid-containing phospholipids, which drives sensitivity to GPX4 inhibition. Epithelial membrane protein 2 (EMP2) expression is reduced upon cell cycle arrest and is sufficient to enhance ferroptosis in response to direct GPX4 inhibition. An orally bioavailable GPX4 inhibitor increased markers of ferroptotic lipid peroxidation in vivo in combination with a cell cycle arresting agent. Thus, responses to different ferroptosis-inducing stimuli can be regulated by cell cycle state.

    View details for DOI 10.1101/2023.07.19.549715

    View details for PubMedID 37502927

    View details for PubMedCentralID PMC10370086

  • Regulation of ferroptosis by lipid metabolism. Trends in cell biology Pope, L. E., Dixon, S. J. 2023


    Ferroptosis is an iron-dependent lethal mechanism that can be activated in disease and is a proposed target for cancer therapy. Ferroptosis is defined by the overwhelming accumulation of membrane lipid peroxides. Ferroptotic lipid peroxidation is initiated on internal membranes and then appears at the plasma membrane, triggering lethal ion imbalances and membrane permeabilization. Sensitivity to ferroptosis is governed by the levels of peroxidizable polyunsaturated lipids and associated lipid metabolic enzymes. A different network of enzymes and endogenous metabolites restrains lipid peroxidation by interfering with the initiation or propagation of this process. This emerging understanding is informing new approaches to treat disease by modulating lipid metabolism to enhance or inhibit ferroptosis.

    View details for DOI 10.1016/j.tcb.2023.05.003

    View details for PubMedID 37407304

  • CDKN2A deletion remodels lipid metabolism to prime glioblastoma for ferroptosis. Cancer cell Minami, J. K., Morrow, D., Bayley, N. A., Fernandez, E. G., Salinas, J. J., Tse, C., Zhu, H., Su, B., Plawat, R., Jones, A., Sammarco, A., Liau, L. M., Graeber, T. G., Williams, K. J., Cloughesy, T. F., Dixon, S. J., Bensinger, S. J., Nathanson, D. A. 2023


    Malignant tumors exhibit heterogeneous metabolic reprogramming, hindering the identification of translatable vulnerabilities for metabolism-targeted therapy. How molecular alterations in tumors promote metabolic diversity and distinct targetable dependencies remains poorly defined. Here we create a resource consisting of lipidomic, transcriptomic, and genomic data from 156 molecularly diverse glioblastoma (GBM) tumors and derivative models. Through integrated analysis of the GBM lipidome with molecular datasets, we identify CDKN2A deletion remodels the GBM lipidome, notably redistributing oxidizable polyunsaturated fatty acids into distinct lipid compartments. Consequently, CDKN2A-deleted GBMs display higher lipid peroxidation, selectively priming tumors for ferroptosis. Together, this study presents a molecular and lipidomic resource of clinical and preclinical GBM specimens, which we leverage to detect a therapeutically exploitable link between a recurring molecular lesion and altered lipid metabolism in GBM.

    View details for DOI 10.1016/j.ccell.2023.05.001

    View details for PubMedID 37236196

  • Identification of structurally diverse FSP1 inhibitors that sensitize cancer cells to ferroptosis. Cell chemical biology Hendricks, J. M., Doubravsky, C. E., Wehri, E., Li, Z., Roberts, M. A., Deol, K. K., Lange, M., Lasheras-Otero, I., Momper, J. D., Dixon, S. J., Bersuker, K., Schaletzky, J., Olzmann, J. A. 2023


    Ferroptosis is a regulated form of cell death associated with the iron-dependent accumulation of phospholipid hydroperoxides. Inducing ferroptosis is a promising approach to treat therapy-resistant cancer. Ferroptosis suppressor protein 1 (FSP1) promotes ferroptosis resistance in cancer by generating the antioxidant form of coenzyme Q10 (CoQ). Despite the important role of FSP1, few molecular tools exist that target the CoQ-FSP1 pathway. Through a series of chemical screens, we identify several structurally diverse FSP1 inhibitors. The most potent of these compounds, ferroptosis sensitizer 1 (FSEN1), is an uncompetitive inhibitor that acts selectively through on-target inhibition of FSP1 to sensitize cancer cells to ferroptosis. Furthermore, a synthetic lethality screen reveals that FSEN1 synergizes with endoperoxide-containing ferroptosis inducers, including dihydroartemisinin, to trigger ferroptosis. These results provide new tools that catalyze the exploration of FSP1 as a therapeutic target and highlight the value of combinatorial therapeutic regimes targeting FSP1 and additional ferroptosis defense pathways.

    View details for DOI 10.1016/j.chembiol.2023.04.007

    View details for PubMedID 37178691

  • Lipid droplets and peroxisomes are co-regulated to drive lifespan extension in response to mono-unsaturated fatty acids. Nature cell biology Papsdorf, K., Miklas, J. W., Hosseini, A., Cabruja, M., Morrow, C. S., Savini, M., Yu, Y., Silva-Garcia, C. G., Haseley, N. R., Murphy, L. M., Yao, P., de Launoit, E., Dixon, S. J., Snyder, M. P., Wang, M. C., Mair, W. B., Brunet, A. 2023


    Dietary mono-unsaturated fatty acids (MUFAs) are linked to longevity in several species. But the mechanisms by which MUFAs extend lifespan remain unclear. Here we show that an organelle network involving lipid droplets and peroxisomes is critical for MUFA-induced longevity in Caenorhabditis elegans. MUFAs upregulate the number of lipid droplets in fat storage tissues. Increased lipid droplet number is necessary for MUFA-induced longevity and predicts remaining lifespan. Lipidomics datasets reveal that MUFAs also modify the ratio of membrane lipids and ether lipids-a signature associated with decreased lipid oxidation. In agreement with this, MUFAs decrease lipid oxidation in middle-aged individuals. Intriguingly, MUFAs upregulate not only lipid droplet number but also peroxisome number. A targeted screen identifies genes involved in the co-regulation of lipid droplets and peroxisomes, and reveals that induction of both organelles is optimal for longevity. Our study uncovers an organelle network involved in lipid homeostasis and lifespan regulation, opening new avenues for interventions to delay aging.

    View details for DOI 10.1038/s41556-023-01136-6

    View details for PubMedID 37127715

  • Apoptotic cell death in disease-Current understanding of the NCCD 2023. Cell death and differentiation Vitale, I., Pietrocola, F., Guilbaud, E., Aaronson, S. A., Abrams, J. M., Adam, D., Agostini, M., Agostinis, P., Alnemri, E. S., Altucci, L., Amelio, I., Andrews, D. W., Aqeilan, R. I., Arama, E., Baehrecke, E. H., Balachandran, S., Bano, D., Barlev, N. A., Bartek, J., Bazan, N. G., Becker, C., Bernassola, F., Bertrand, M. J., Bianchi, M. E., Blagosklonny, M. V., Blander, J. M., Blandino, G., Blomgren, K., Borner, C., Bortner, C. D., Bove, P., Boya, P., Brenner, C., Broz, P., Brunner, T., Damgaard, R. B., Calin, G. A., Campanella, M., Candi, E., Carbone, M., Carmona-Gutierrez, D., Cecconi, F., Chan, F. K., Chen, G., Chen, Q., Chen, Y. H., Cheng, E. H., Chipuk, J. E., Cidlowski, J. A., Ciechanover, A., Ciliberto, G., Conrad, M., Cubillos-Ruiz, J. R., Czabotar, P. E., D'Angiolella, V., Daugaard, M., Dawson, T. M., Dawson, V. L., De Maria, R., De Strooper, B., Debatin, K., Deberardinis, R. J., Degterev, A., Del Sal, G., Deshmukh, M., Di Virgilio, F., Diederich, M., Dixon, S. J., Dynlacht, B. D., El-Deiry, W. S., Elrod, J. W., Engeland, K., Fimia, G. M., Galassi, C., Ganini, C., Garcia-Saez, A. J., Garg, A. D., Garrido, C., Gavathiotis, E., Gerlic, M., Ghosh, S., Green, D. R., Greene, L. A., Gronemeyer, H., Hacker, G., Hajnoczky, G., Hardwick, J. M., Haupt, Y., He, S., Heery, D. M., Hengartner, M. O., Hetz, C., Hildeman, D. A., Ichijo, H., Inoue, S., Jaattela, M., Janic, A., Joseph, B., Jost, P. J., Kanneganti, T., Karin, M., Kashkar, H., Kaufmann, T., Kelly, G. L., Kepp, O., Kimchi, A., Kitsis, R. N., Klionsky, D. J., Kluck, R., Krysko, D. V., Kulms, D., Kumar, S., Lavandero, S., Lavrik, I. N., Lemasters, J. J., Liccardi, G., Linkermann, A., Lipton, S. A., Lockshin, R. A., Lopez-Otin, C., Luedde, T., MacFarlane, M., Madeo, F., Malorni, W., Manic, G., Mantovani, R., Marchi, S., Marine, J., Martin, S. J., Martinou, J., Mastroberardino, P. G., Medema, J. P., Mehlen, P., Meier, P., Melino, G., Melino, S., Miao, E. A., Moll, U. M., Munoz-Pinedo, C., Murphy, D. J., Niklison-Chirou, M. V., Novelli, F., Nunez, G., Oberst, A., Ofengeim, D., Opferman, J. T., Oren, M., Pagano, M., Panaretakis, T., Pasparakis, M., Penninger, J. M., Pentimalli, F., Pereira, D. M., Pervaiz, S., Peter, M. E., Pinton, P., Porta, G., Prehn, J. H., Puthalakath, H., Rabinovich, G. A., Rajalingam, K., Ravichandran, K. S., Rehm, M., Ricci, J., Rizzuto, R., Robinson, N., Rodrigues, C. M., Rotblat, B., Rothlin, C. V., Rubinsztein, D. C., Rudel, T., Rufini, A., Ryan, K. M., Sarosiek, K. A., Sawa, A., Sayan, E., Schroder, K., Scorrano, L., Sesti, F., Shao, F., Shi, Y., Sica, G. S., Silke, J., Simon, H., Sistigu, A., Stephanou, A., Stockwell, B. R., Strapazzon, F., Strasser, A., Sun, L., Sun, E., Sun, Q., Szabadkai, G., Tait, S. W., Tang, D., Tavernarakis, N., Troy, C. M., Turk, B., Urbano, N., Vandenabeele, P., Vanden Berghe, T., Vander Heiden, M. G., Vanderluit, J. L., Verkhratsky, A., Villunger, A., von Karstedt, S., Voss, A. K., Vousden, K. H., Vucic, D., Vuri, D., Wagner, E. F., Walczak, H., Wallach, D., Wang, R., Wang, Y., Weber, A., Wood, W., Yamazaki, T., Yang, H., Zakeri, Z., Zawacka-Pankau, J. E., Zhang, L., Zhang, H., Zhivotovsky, B., Zhou, W., Piacentini, M., Kroemer, G., Galluzzi, L. 2023


    Apoptosis is a form of regulated cell death (RCD) that involves proteases of the caspase family. Pharmacological and genetic strategies that experimentally inhibit or delay apoptosis in mammalian systems have elucidated the key contribution of this process not only to (post-)embryonic development and adult tissue homeostasis, but also to the etiology of multiple human disorders. Consistent with this notion, while defects in the molecular machinery for apoptotic cell death impair organismal development and promote oncogenesis, the unwarranted activation of apoptosis promotes cell loss and tissue damage in the context of various neurological, cardiovascular, renal, hepatic, infectious, neoplastic and inflammatory conditions. Here, the Nomenclature Committee on Cell Death (NCCD) gathered to critically summarize anabundant pre-clinical literature mechanistically linking the core apoptotic apparatus to organismal homeostasis in the context of disease.

    View details for DOI 10.1038/s41418-023-01153-w

    View details for PubMedID 37100955

  • Ferroptosis: A flexible constellation of related biochemical mechanisms. Molecular cell Dixon, S. J., Pratt, D. A. 2023


    It is common to think about and depict biological processes as being governed by fixed pathways with specific components interconnected by concrete positive and negative interactions. However, these models may fail to effectively capture the regulation of cell biological processes that are driven by chemical mechanisms that do not rely absolutely on specific metabolites or proteins. Here, we discuss how ferroptosis, a non-apoptotic cell death mechanism with emerging links to disease, may be best understood as a highly flexible mechanism that can be executed and regulated by many functionally related metabolites and proteins. The inherent plasticity of ferroptosis has implications for how to define and study this mechanism in healthy and diseased cells and organisms.

    View details for DOI 10.1016/j.molcel.2023.03.005

    View details for PubMedID 36977413

  • Ferroptotic mechanisms and therapeutic targeting of iron metabolism and lipid peroxidation in the kidney. Nature reviews. Nephrology Bayır, H., Dixon, S. J., Tyurina, Y. Y., Kellum, J. A., Kagan, V. E. 2023


    Ferroptosis is a mechanism of regulated necrotic cell death characterized by iron-dependent, lipid peroxidation-driven membrane destruction that can be inhibited by glutathione peroxidase 4. Morphologically, it is characterized by cellular, organelle and cytoplasmic swelling and the loss of plasma membrane integrity, with the release of intracellular components. Ferroptosis is triggered in cells with dysregulated iron and thiol redox metabolism, whereby the initial robust but selective accumulation of hydroperoxy polyunsaturated fatty acid-containing phospholipids is further propagated through enzymatic and non-enzymatic secondary mechanisms, leading to formation of oxidatively truncated electrophilic species and their adducts with proteins. Thus, ferroptosis is dependent on the convergence of iron, thiol and lipid metabolic pathways. The kidney is particularly susceptible to redox imbalance. A growing body of evidence has linked ferroptosis to acute kidney injury in the context of diverse stimuli, such as ischaemia-reperfusion, sepsis or toxins, and to chronic kidney disease, suggesting that ferroptosis may represent a novel therapeutic target for kidney disease. However, further work is needed to address gaps in our understanding of the triggers, execution and spreading mechanisms of ferroptosis.

    View details for DOI 10.1038/s41581-023-00689-x

    View details for PubMedID 36922653

    View details for PubMedCentralID 6534278

  • Surveying the landscape of emerging and understudied cell death mechanisms. Biochimica et biophysica acta. Molecular cell research Leak, L., Dixon, S. J. 2023: 119432


    Cell death can be a highly regulated process. A large and growing number of mammalian cell death mechanisms have been described over the past few decades. Major pathways with established roles in normal or disease biology include apoptosis, necroptosis, pyroptosis and ferroptosis. However, additional non-apoptotic cell death mechanisms with unique morphological, genetic, and biochemical features have also been described. These mechanisms may play highly specialized physiological roles or only become activated in response to specific lethal stimuli or conditions. Understanding the nature of these emerging and understudied mechanisms may provide new insight into cell death biology and suggest new treatments for diseases such as cancer and neurodegeneration.

    View details for DOI 10.1016/j.bbamcr.2023.119432

    View details for PubMedID 36690038

  • Discovering new molecular mechanisms of cell death Dixon, S. ELSEVIER. 2023: S713
  • A Tale of Two Lipids: Lipid Unsaturation Commands Ferroptosis Sensitivity. Proteomics Rodencal, J., Dixon, S. J. 2022: e2100308


    Membrane lipids play important roles in the regulation of cell fate, including the execution of ferroptosis. Ferroptosis is a non-apoptotic cell death mechanism defined by iron-dependent membrane lipid peroxidation. Phospholipids containing polyunsaturated fatty acids (PUFAs) are highly vulnerable to peroxidation and are essential for ferroptosis execution. By contrast, the incorporation of less oxidizable monounsaturated fatty acids (MUFAs) in membrane phospholipids protects cells from ferroptosis. The enzymes and pathways that govern PUFA and MUFA metabolism therefore play a critical role in determining cellular sensitivity to ferroptosis. Here, we review three lipid metabolic processes fatty acid biosynthesis, ether lipid biosynthesis, and phospholipid remodeling-that govern ferroptosis sensitivity by regulating the balance of PUFAs and MUFAs in membrane phospholipids. This article is protected by copyright. All rights reserved.

    View details for DOI 10.1002/pmic.202100308

    View details for PubMedID 36398995

  • Oxaliplatin disrupts nucleolar function through biophysical disintegration. Cell reports Schmidt, H. B., Jaafar, Z. A., Wulff, B. E., Rodencal, J. J., Hong, K., Aziz-Zanjani, M. O., Jackson, P. K., Leonetti, M. D., Dixon, S. J., Rohatgi, R., Brandman, O. 2022; 41 (6): 111629


    Platinum (Pt) compounds such as oxaliplatin are among the most commonly prescribed anti-cancer drugs. Despite their considerable clinical impact, the molecular basis of platinum cytotoxicity and cancer specificity remain unclear. Here we show that oxaliplatin, a backbone for the treatment of colorectal cancer, causes liquid-liquid demixing of nucleoli at clinically relevant concentrations. Our data suggest that this biophysical defect leads to cell-cycle arrest, shutdown of Pol I-mediated transcription, and ultimately cell death. We propose that instead of targeting a single molecule, oxaliplatin preferentially partitions into nucleoli, where it modifies nucleolar RNA and proteins. This mechanism provides a general approach for drugging the increasing number of cellular processes linked to biomolecular condensates.

    View details for DOI 10.1016/j.celrep.2022.111629

    View details for PubMedID 36351392

  • Ferroptosis inhibition by lysosome-dependent catabolism of extracellular protein. Cell chemical biology Armenta, D. A., Laqtom, N. N., Alchemy, G., Dong, W., Morrow, D., Poltorack, C. D., Nathanson, D. A., Abu-Remalieh, M., Dixon, S. J. 2022


    Cancer cells need a steady supply of nutrients to evade cell death and proliferate. Depriving cancer cells of the amino acid cystine can trigger the non-apoptotic cell death process of ferroptosis. Here, we report that cancer cells can evade cystine deprivation-induced ferroptosis by uptake and catabolism of the cysteine-rich extracellular protein albumin. This protective mechanism is enhanced by mTORC1 inhibition and involves albumin degradation in the lysosome, predominantly by cathepsin B (CTSB). CTSB-dependent albumin breakdown followed by export of cystine from the lysosome via the transporter cystinosin fuels the synthesis of glutathione, which suppresses lethal lipid peroxidation. When cancer cells are grown under non-adherent conditions as spheroids, mTORC1 pathway activity is reduced, and albumin supplementation alone affords considerable protection against ferroptosis. These results identify the catabolism of extracellular protein within the lysosome as a mechanism that can inhibit ferroptosis in cancer cells.

    View details for DOI 10.1016/j.chembiol.2022.10.006

    View details for PubMedID 36306785

  • Ether lipid deficiency disrupts lipid homeostasis leading to ferroptosis sensitivity. PLoS genetics Perez, M. A., Clostio, A. J., Houston, I. R., Ruiz, J., Magtanong, L., Dixon, S. J., Watts, J. L. 2022; 18 (9): e1010436


    Ferroptosis is an iron-dependent form of regulated cell death associated with uncontrolled membrane lipid peroxidation and destruction. Previously, we showed that dietary dihomo-gamma-linolenic acid (DGLA; 20: 3(n-6)) triggers ferroptosis in the germ cells of the model organism, Caenorhabditis elegans. We also demonstrated that ether lipid-deficient mutant strains are sensitive to DGLA-induced ferroptosis, suggesting a protective role for ether lipids. The vinyl ether bond unique to plasmalogen lipids has been hypothesized to function as an antioxidant, but this has not been tested in animal models. In this study, we used C. elegans mutants to test the hypothesis that the vinyl ether bond in plasmalogens acts as an antioxidant to protect against germ cell ferroptosis as well as to protect from whole-body tert-butyl hydroperoxide (TBHP)-induced oxidative stress. We found no role for plasmalogens in either process. Instead, we demonstrate that ether lipid-deficiency disrupts lipid homeostasis in C. elegans, leading to altered ratios of saturated and monounsaturated fatty acid (MUFA) content in cellular membranes. We demonstrate that ferroptosis sensitivity in both wild type and ether-lipid deficient mutants can be rescued in several ways that change the relative abundance of saturated fats, MUFAs and specific polyunsaturated fatty acids (PUFAs). Specifically, we reduced ferroptosis sensitivity by (1) using mutant strains unable to synthesize DGLA, (2) using a strain carrying a gain-of-function mutation in the transcriptional mediator MDT-15, or (3) by dietary supplementation of MUFAs. Furthermore, our studies reveal important differences in how dietary lipids influence germ cell ferroptosis versus whole-body peroxide-induced oxidative stress. These studies highlight a potentially beneficial role for endogenous and dietary MUFAs in the prevention of ferroptosis.

    View details for DOI 10.1371/journal.pgen.1010436

    View details for PubMedID 36178986

  • Context-dependent regulation of ferroptosis sensitivity. Cell chemical biology Magtanong, L., Mueller, G. D., Williams, K. J., Billmann, M., Chan, K., Armenta, D. A., Moffat, J., Boone, C., Myers, C. L., Olzmann, J. A., Bensinger, S. J., Dixon, S. J. 2022


    Ferroptosis is an important mediator of pathophysiological cell death and an emerging target for cancer therapy. Whether ferroptosis sensitivity is governed by a single regulatory mechanism is unclear. Here, based on the integration of 24 published chemical genetic screens combined with targeted follow-up experimentation, we find that the genetic regulation of ferroptosis sensitivity is highly variable and context-dependent. For example, the lipid metabolic gene acyl-coenzyme A (CoA) synthetase long chain family member 4 (ACSL4) appears far more essential for ferroptosis triggered by direct inhibition of the lipid hydroperoxidase glutathione peroxidase 4 (GPX4) than by cystine deprivation. Despite this, distinct pro-ferroptotic stimuli converge upon a common lethal effector mechanism: accumulation of lipid peroxides at the plasma membrane. These results indicate that distinct genetic mechanisms regulate ferroptosis sensitivity, with implications for the initiation and analysis of this process invivo.

    View details for DOI 10.1016/j.chembiol.2022.06.004

    View details for PubMedID 35809566

  • Ribosome stalling during selenoprotein translation exposes a ferroptosis vulnerability. Nature chemical biology Li, Z., Ferguson, L., Deol, K. K., Roberts, M. A., Magtanong, L., Hendricks, J. M., Mousa, G. A., Kilinc, S., Schaefer, K., Wells, J. A., Bassik, M. C., Goga, A., Dixon, S. J., Ingolia, N. T., Olzmann, J. A. 2022


    The selenoprotein glutathione peroxidase 4 (GPX4) prevents ferroptosis by converting lipid peroxides into nontoxic lipid alcohols. GPX4 has emerged as a promising therapeutic target for cancer treatment, but some cancer cells are resistant to ferroptosis triggered by GPX4 inhibition. Using a chemical-genetic screen, we identify LRP8 (also known as ApoER2) as a ferroptosis resistance factor that is upregulated in cancer. Loss of LRP8 decreases cellular selenium levels and the expression of a subset of selenoproteins. Counter to the canonical hierarchical selenoprotein regulatory program, GPX4 levels are strongly reduced due to impaired translation. Mechanistically, low selenium levels result in ribosome stalling at the inefficiently decoded GPX4 selenocysteine UGA codon, leading to ribosome collisions, early translation termination and proteasomal clearance of the N-terminal GPX4 fragment. These findings reveal rewiring of the selenoprotein hierarchy in cancer cells and identify ribosome stalling and collisions during GPX4 translation as ferroptosis vulnerabilities in cancer.

    View details for DOI 10.1038/s41589-022-01033-3

    View details for PubMedID 35637349

  • Ferroptosis Regulation by the NGLY1/NFE2L1 Pathway. FASEB journal : official publication of the Federation of American Societies for Experimental Biology Murray, M., Forcina, G., Pope, L., Dong, W., Abu-Remaileh, M., Bertozzi, C., Dixon, S. 2022; 36 Suppl 1


    Cells are equipped with various mechanisms to maintain cell viability upon exposure to stress. The Cap 'n' Collar (CNC) family includes five vertebrate stress-responsive transcription factors. The CNC member nuclear factor erythroid 2 like 2 (NFE2L2) is considered the master regulator of the cellular oxidative stress response. Fellow CNC member nuclear erythroid 2 like 1 (NFE2L1) is better known for its role in responding to proteasome dysfunction. We hypothesized that NFE2L1 also responds to oxidative stress. We demonstrate that genetic disruption of NFE2L1 sensitizes cancer cells to death by a non-apoptotic, oxidative form of cell death termed ferroptosis. We also show that genetic disruption of N-glycanase 1 (NGLY1), which catalyzes NFE2L1 deglycosylation and sequence editing, sensitizes cancer cells to ferroptosis through an NFE2L1-dependent mechanism. Expression of a sequence-edited NFE2L1 mutant, which mimics NGLY1-processed NFE2L1, rescues cellular resistance to ferroptosis in NFE2L1 gene-disrupted cells. Finally, we provide evidence that the ferroptosis protection conferred by NFE2L1 is mediated by the expression of glutathione peroxidase 4 (GPX4). All together, our results highlight the role of NFE2L1 in ferroptosis resistance and implicate NFE2L1 and NGLY1 as potential targets for cancer therapy.

    View details for DOI 10.1096/fasebj.2022.36.S1.R2814

    View details for PubMedID 35560739

  • A Novel Cell Death Mechanism Involving the Sphingosine-to-Glycerophospholipid Pathway. FASEB journal : official publication of the Federation of American Societies for Experimental Biology Leak, L., Dixon, S. 2022; 36 Suppl 1


    Apoptosis is the most well-studied form of cell death, but there exist other cell death pathways that also have roles in normal physiology and disease. It is unclear what other forms of cell death remain to be discovered and how these pathways could inform our understanding of cell and molecular biology. Caspase-independent lethal 56 (CIL56) is a compound that kills cells via a novel cell death mechanism. We conducted a genome-wide CRISPR screen to identify novel regulators of this death pathway. From the screen, we identified trans-2-enoyl-CoA reductase (TECR) as a key regulator of CIL56-induced death. TECR is localized to the endoplasmic reticulum and is required for very long-chain fatty acid (VLCFA) synthesis. When the gene encoding TECR is disrupted, cells become resistant to CIL56-induced death. We find that VLCFA synthesis is dispensable for CIL56-induced death. On the contrary, TECR has a non-canonical role in the conversion of sphingosine to palmitate in the sphingosine-to-glycerophospholipid pathway. Through chemical complementation analyses, we find that this pathway is important for death induction by CIL56. It remains unclear how this pathway could be acting to execute cell death. It is known that palmitate produced in the endoplasmic reticulum can be incorporated into ceramide species, which have long been associated with cell death. Preliminary lipidomic analyses reveal a dramatic increase in palmitoyl-ceramide upon CIL56 treatment. We are investigating the role of this species in CIL56-induced cell death to further characterize the mechanism of death and its importance.

    View details for DOI 10.1096/fasebj.2022.36.S1.R2783

    View details for PubMedID 35556625

  • The Role of Palmitoyltransferase ZDHHC5 in Regulating RAS Function. FASEB journal : official publication of the Federation of American Societies for Experimental Biology Ritho, J., Dixon, S. 2022; 36 Suppl 1


    More than 90% of pancreatic ductal adenocarcinoma (PDAC), the most common type of pancreatic cancer, harbor an activating KRAS mutation which consequently alters its downstream signaling pathways. S-palmitoylation is a dynamic post-translational modification that has been implicated in maintaining the altered function of key oncogenes important in cancer progression. S-palmitoylation is catalyzed by a large family of 23 zinc finger DHHC-type (ZDHHC) palmitoyl S-acyltransferases. Our understanding of how specific ZDHHC enzymes regulate tumor progression remains limited. Analysis of data available in TCGA indicates that high levels of ZDHHC5 correlates with a poor survival in pancreatic cancer patients. Notably, we observed in published proximity-dependent biotin labeling studies that the palmitoyltransferase ZDHHC5 is consistently identified as a novel Ras interactor. Accordingly, we hypothesize that ZDHHC5 may modulate the function of Ras in cancer cells. We find that genetic disruption of ZDHHC5 causes loss of Ras activity and membrane localization, consequently decreasing the MAPK pathway in pancreatic cancer cell lines. Biochemical characterization of ZDHHC5-dependent regulation of Ras function in pancreatic cancer will provide more information on how to target it and create a therapeutic window that will help to prevent pancreatic cancer progression.

    View details for DOI 10.1096/fasebj.2022.36.S1.R3894

    View details for PubMedID 35554284

  • The Role of Monounsaturated Fatty Acids in Ferroptosis. FASEB journal : official publication of the Federation of American Societies for Experimental Biology Pope, L. E., Dixon, S. 2022; 36 Suppl 1


    Exogenous monounsaturated fatty acids (MUFAs) such as oleate (18:1 n-9) protect cells from ferroptotic cell death, contributing to cancer cells' metastatic potential in vivo. Understanding how MUFAs prevent ferroptosis is critical for developing new anti-cancer therapeutics that target this non-apoptotic cell death process. A diversity of MUFAs with varying chain lengths and double bond positions are synthesized in human cells and found in human diets. It is presently unclear which MUFAs can inhibit ferroptosis, and whether all those that are protective act through the same mechanism. To investigate, we have screened a library of structurally distinct MUFA species for their ability to inhibit ferroptosis under various conditions. We find that protection against ferroptosis is MUFA structure-specific, with only certain species being able to protect from ferroptosis. Further investigation indicates that, in response to a pro-ferroptotic stimulus, protective MUFAs can inhibit the formation of toxic lipid reactive oxygen species while non-protective MUFAs are unable to do so. Interestingly, some non-protective MUFAs nonetheless appear to enter the cells and become activated. Thus, we posit that enzymes necessary for MUFA-mediated ferroptosis protection specifically activate and incorporate only certain protective MUFAs into membrane phospholipids. Further characterization of the MUFA metabolic pathway will inform endeavors to synthesize potent ferroptosis inducers that overcome the protective nature of MUFAs in ferroptosis in vivo.

    View details for DOI 10.1096/fasebj.2022.36.S1.0R871

    View details for PubMedID 35554336

  • Lipid Metabolism and Ferroptosis. FASEB journal : official publication of the Federation of American Societies for Experimental Biology Dixon, S. 2022; 36 Suppl 1


    Ferroptosis is an oxidative, iron-dependent form of non-apoptotic cell death that contributes to several forms of pathology and may be exploitable for cancer therapy. Ferroptosis can be induced using small molecule inhibitors of the plasma membrane cystine/glutamate antiporter system xc - or the glutathione-dependent lipid hydroperoxidase glutathione peroxidase 4 (GPX4). The execution of ferroptosis requires membrane lipid peroxidation, but specific lipids and lipid metabolic enzymes that are involved in this process are only partly characterized. How ferroptosis sensitivity relates to other fundamental cellular processes such as the cell cycle is also unclear. We find that inhibition of the Rb-E2F cell cycle pathway causes downregulation of specific lipid metabolic enzymes, leading to an increase in polyunsaturated phospholipid abundance. In turn, this metabolic alteration specifically enhances ferroptosis sensitivity. Drugs that inhibit Rb-E2F pathway function synergize with a ferroptosis-inducing small molecule to arrest tumor growth in vivo. These results suggest that ferroptosis sensitivity may be linked to cell cycle progression through specific alterations in membrane phospholipid composition.

    View details for DOI 10.1096/fasebj.2022.36.S1.0I209

    View details for PubMedID 35553505

  • Nucleotide biosynthesis links glutathione metabolism to ferroptosis sensitivity. Life science alliance Tarangelo, A., Rodencal, J., Kim, J. T., Magtanong, L., Long, J. Z., Dixon, S. J. 1800; 5 (4)


    Nucleotide synthesis is a metabolically demanding process essential for DNA replication and other processes in the cell. Several anticancer drugs that inhibit nucleotide metabolism induce apoptosis. How inhibition of nucleotide metabolism impacts non-apoptotic cell death is less clear. Here, we report that inhibition of nucleotide metabolism by the p53 pathway is sufficient to suppress the non-apoptotic cell death process of ferroptosis. Mechanistically, stabilization of wild-type p53 and induction of the p53 target gene CDKN1A (p21) leads to decreased expression of the ribonucleotide reductase (RNR) subunits RRM1 and RRM2 RNR is the rate-limiting enzyme of de novo nucleotide synthesis that reduces ribonucleotides to deoxyribonucleotides in a glutathione-dependent manner. Direct inhibition of RNR results in conservation of intracellular glutathione, limiting the accumulation of toxic lipid peroxides and preventing the onset of ferroptosis in response to cystine deprivation. These results support a mechanism linking p53-dependent regulation of nucleotide metabolism to non-apoptotic cell death.

    View details for DOI 10.26508/lsa.202101157

    View details for PubMedID 35074928

  • Copper-induced cell death. Science (New York, N.Y.) Kahlson, M. A., Dixon, S. J. 2022; 375 (6586): 1231-1232


    Excess copper causes mitochondrial protein aggregation and triggers a distinct form of cell death.

    View details for DOI 10.1126/science.abo3959

    View details for PubMedID 35298241

  • Ferroptosis regulation by the NGLY1/NFE2L1 pathway. Proceedings of the National Academy of Sciences of the United States of America Forcina, G. C., Pope, L., Murray, M., Dong, W., Abu-Remaileh, M., Bertozzi, C. R., Dixon, S. J. 2022; 119 (11): e2118646119


    SignificanceFerroptosis is an oxidative form of cell death whose biochemical regulation remains incompletely understood. Cap'n'collar (CNC) transcription factors including nuclear factor erythroid-2-related factor 1 (NFE2L1/NRF1) and NFE2L2/NRF2 can both regulate oxidative stress pathways but are each regulated in a distinct manner, and whether these two transcription factors can regulate ferroptosis independent of one another is unclear. We find that NFE2L1 can promote ferroptosis resistance, independent of NFE2L2, by maintaining the expression of glutathione peroxidase 4 (GPX4), a key protein that prevents lethal lipid peroxidation. NFE2L2 can also promote ferroptosis resistance but does so through a distinct mechanism that appears independent of GPX4 protein expression. These results suggest that NFE2L1 and NFE2L2 independently regulate ferroptosis.

    View details for DOI 10.1073/pnas.2118646119

    View details for PubMedID 35271393

  • SU086, an inhibitor of HSP90, impairs glycolysis and represents a treatment strategy for advanced prostate cancer. Cell reports. Medicine Rice, M. A., Kumar, V., Tailor, D., Garcia-Marques, F. J., Hsu, E., Liu, S., Bermudez, A., Kanchustambham, V., Shankar, V., Inde, Z., Alabi, B. R., Muruganantham, A., Shen, M., Pandrala, M., Nolley, R., Aslan, M., Ghoochani, A., Agarwal, A., Buckup, M., Kumar, M., Going, C. C., Peehl, D. M., Dixon, S. J., Zare, R. N., Brooks, J. D., Pitteri, S. J., Malhotra, S. V., Stoyanova, T. 2022; 3 (2): 100502


    Among men, prostate cancer is the second leading cause of cancer-associated mortality, with advanced disease remaining a major clinical challenge. We describe a small molecule, SU086, as a therapeutic strategy for advanced prostate cancer. We demonstrate that SU086 inhibits the growth of prostate cancer cells invitro, cell-line and patient-derived xenografts invivo, and exvivo prostate cancer patient specimens. Furthermore, SU086 in combination with standard of care second-generation anti-androgen therapies displays increased impairment of prostate cancer cell and tumor growth invitro and invivo. Cellular thermal shift assay reveals that SU086 binds to heat shock protein 90 (HSP90) and leads to a decrease in HSP90 levels. Proteomic profiling demonstrates that SU086 binds to and decreases HSP90. Metabolomic profiling reveals that SU086 leads to perturbation of glycolysis. Our study identifies SU086 as a treatment for advanced prostate cancer as a single agent or when combined with second-generation anti-androgens.

    View details for DOI 10.1016/j.xcrm.2021.100502

    View details for PubMedID 35243415

  • Characterization of a small molecule inhibitor of disulfide reductases that induces oxidative stress and lethality in lung cancer cells. Cell reports Johnson, F. D., Ferrarone, J., Liu, A., Brandstadter, C., Munuganti, R., Farnsworth, D. A., Lu, D., Luu, J., Sihota, T., Jansen, S., Nagelberg, A., Shi, R., Forcina, G. C., Zhang, X., Cheng, G. S., Spencer Miko, S. E., de Rappard-Yuswack, G., Sorensen, P. H., Dixon, S. J., Guha, U., Becker, K., Djaballah, H., Somwar, R., Varmus, H., Morin, G. B., Lockwood, W. W. 2022; 38 (6): 110343


    Phenotype-based screening can identify small molecules that elicit a desired cellular response, but additional approaches are required to characterize their targets and mechanisms of action. Here, we show that a compound termed LCS3, which selectively impairs the growth of human lung adenocarcinoma (LUAD) cells, induces oxidative stress. To identify the target that mediates this effect, we use thermal proteome profiling (TPP) and uncover the disulfide reductases GSR and TXNRD1 as targets. We confirm through enzymatic assays that LCS3 inhibits disulfide reductase activity through a reversible, uncompetitive mechanism. Further, we demonstrate that LCS3-sensitive LUAD cells are sensitive to the synergistic inhibition of glutathione and thioredoxin pathways. Lastly, a genome-wide CRISPR knockout screen identifies NQO1 loss as a mechanism of LCS3 resistance. This work highlights the ability of TPP to uncover targets of small molecules identified by high-throughput screens and demonstrates the potential therapeutic utility of inhibiting disulfide reductases in LUAD.

    View details for DOI 10.1016/j.celrep.2022.110343

    View details for PubMedID 35139387

  • Excited to see you: New imaging approaches to detect ferrous iron invivo. Cell chemical biology Ritho, J., Dixon, S. J. 1800; 29 (1): 3-4


    Ferroptosis is an iron-dependent form of cell death implicated in cancer and neurodegenerative diseases. In this issue of Cell Chemical Biology, Shao etal. (2022) and Wang etal. (2022) describe imaging techniques to monitor ferrous iron levels and iron-dependent lipid peroxidation, two key determinants of ferroptosis sensitivity.

    View details for DOI 10.1016/j.chembiol.2021.12.012

    View details for PubMedID 35063066

  • Positive feedback amplifies ferroptosis. Nature cell biology Rodencal, J., Dixon, S. J. 1800; 24 (1): 4-5

    View details for DOI 10.1038/s41556-021-00824-5

    View details for PubMedID 35027732

  • Identifying a novel glycolytic inhibitor for treatment of aggressive prostate cancer. Stoyanova, T., Rice, M. A., Kumar, V., Tailor, D., Garcia-Marques, F., Bermudez, A., Kanchustambham, V., Shankar, V., Inde, Z., Pandrala, M., Nolley, R., Ghoochani, A., Liu, S., Aslan, M., Agarwal, A., Buckup, M., Hsu, E., Going, C. C., Peehl, D. M., Dixon, S. J., Zare, R. N., Brooks, J. D., Pitteri, S. J., Malhotra, S. V., Stoyanova, T. AMER ASSOC CANCER RESEARCH. 2021
  • Quantification of drug-induced fractional killing using high-throughput microscopy. STAR protocols Inde, Z., Rodencal, J., Dixon, S. J. 2021; 2 (1): 100300


    Anti-cancer drugs kill only a fraction of cells within a population at any given time. Here, we describe a protocol to quantify drug-induced fractional killing over time using high-throughput imaging. This protocol can be used to compare the effect of hundreds of conditions in parallel. We show how this protocol can be used to examine fractional killing in response to inhibitors of the mitogen-activated protein kinase pathway. For complete details on the use and execution of this protocol, please refer to Inde etal. (2020).

    View details for DOI 10.1016/j.xpro.2021.100300

    View details for PubMedID 33532743

  • A compendium of kinetic modulatory profiles identifies ferroptosis regulators. Nature chemical biology Conlon, M., Poltorack, C. D., Forcina, G. C., Armenta, D. A., Mallais, M., Perez, M. A., Wells, A., Kahanu, A., Magtanong, L., Watts, J. L., Pratt, D. A., Dixon, S. J. 2021


    Cell death can be executed by regulated apoptotic and nonapoptotic pathways, including the iron-dependent process of ferroptosis. Small molecules are essential tools for studying the regulation of cell death. Using time-lapse imaging and a library of 1,833 bioactive compounds, we assembled a large compendium of kinetic cell death modulatory profiles for inducers of apoptosis and ferroptosis. From this dataset we identify dozens of ferroptosis suppressors, including numerous compounds that appear to act via cryptic off-target antioxidant or iron chelating activities. We show that the FDA-approved drug bazedoxifene acts as a potent radical trapping antioxidant inhibitor of ferroptosis both in vitro and in vivo. ATP-competitive mechanistic target of rapamycin (mTOR) inhibitors, by contrast, are on-target ferroptosis inhibitors. Further investigation revealed both mTOR-dependent and mTOR-independent mechanisms that link amino acid metabolism to ferroptosis sensitivity. These results highlight kinetic modulatory profiling as a useful tool to investigate cell death regulation.

    View details for DOI 10.1038/s41589-021-00751-4

    View details for PubMedID 33686292

  • Understanding the Role of Cysteine in Ferroptosis: Progress & Paradoxes. The FEBS journal Poltorack, C. D., Dixon, S. J. 2021


    Cysteine is a conditionally essential amino acid that contributes to the synthesis of proteins and many important intracellular metabolites. Cysteine depletion can trigger iron-dependent non-apoptotic cell death-ferroptosis. Despite this, cysteine itself is normally maintained at relatively low levels within the cell, and many mechanisms that could act to buffer cysteine depletion do not appear to be especially effective or active, at least in cancer cells. How do we reconcile these seemingly paradoxical features? Here we describe the regulation of cysteine and contribution to ferroptosis and speculate about how the levels of this amino acid are controlled to govern non-apoptotic cell death.

    View details for DOI 10.1111/febs.15842

    View details for PubMedID 33773039

  • Foreword FERROPTOSIS: MECHANISM AND DISEASES Dixon, S. J., Florez, A. F., Alborzinia, H. 2021; 1301: V-VI
  • Ferroptosis occurs through an osmotic mechanism and propagates independently of cell rupture. Nature cell biology Riegman, M., Sagie, L., Galed, C., Levin, T., Steinberg, N., Dixon, S. J., Wiesner, U., Bradbury, M. S., Niethammer, P., Zaritsky, A., Overholtzer, M. 2020


    Ferroptosis is a regulated form of necrotic cell death that is caused by the accumulation of oxidized phospholipids, leading to membrane damage and cell lysis1,2. Although other types of necrotic death such as pyroptosis and necroptosis are mediated by active mechanisms of execution3-6, ferroptosis is thought to result from the accumulation of unrepaired cell damage1. Previous studies have suggested that ferroptosis has the ability to spread through cell populations in a wave-like manner, resulting in a distinct spatiotemporal pattern of cell death7,8. Here we investigate the mechanism of ferroptosis execution and discover that ferroptotic cell rupture is mediated by plasma membrane pores, similarly to cell lysis in pyroptosis and necroptosis3,4. We further find that intercellular propagation of death occurs following treatment with some ferroptosis-inducing agents, including erastin2,9 and C' dot nanoparticles8, but not upon direct inhibition of the ferroptosis-inhibiting enzyme glutathione peroxidase 4 (GPX4)10. Propagation of a ferroptosis-inducing signal occurs upstream of cell rupture and involves the spreading of a cell swelling effect through cell populations in a lipid peroxide- and iron-dependent manner.

    View details for DOI 10.1038/s41556-020-0565-1

    View details for PubMedID 32868903

  • Investigating Nonapoptotic Cell Death Using Chemical Biology Approaches. Cell chemical biology Armenta, D. A., Dixon, S. J. 2020


    Nonapoptotic cell death is important for human health and disease. Here, we show how various tools and techniques drawn from the chemical biology field have played a central role in the discovery and characterization of nonapoptotic cell death pathways. Focusing on the example of ferroptosis, we describe how phenotypic screening, chemoproteomics, chemical genetic analysis, and other methods enabled the elucidation of this pathway. Synthetic small-molecule inducers and inhibitors of ferroptosis identified in early studies have now been leveraged to identify an even broader set of compounds that affect ferroptosis and to validate new chemical methods and probes for various ferroptosis-associated processes. A number of limitations associated with specific chemical biology tools or techniques have also emerged and must be carefully considered. Nevertheless, the study of ferroptosis provides a roadmap for how chemical biology methods may be used to discover and characterize nonapoptotic cell death mechanisms.

    View details for DOI 10.1016/j.chembiol.2020.03.005

    View details for PubMedID 32220334

  • Systematic Identification of Regulators of Oxidative Stress Reveals Non-canonical Roles for Peroxisomal Import and the Pentose Phosphate Pathway. Cell reports Dubreuil, M. M., Morgens, D. W., Okumoto, K., Honsho, M., Contrepois, K., Lee-McMullen, B., Traber, G. M., Sood, R. S., Dixon, S. J., Snyder, M. P., Fujiki, Y., Bassik, M. C. 2020; 30 (5): 1417


    Reactive oxygen species (ROS) play critical roles inmetabolism and disease, yet a comprehensive analysis of the cellular response to oxidative stress is lacking. To systematically identify regulators ofoxidative stress, we conducted genome-wide Cas9/CRISPR and shRNA screens. This revealed a detailed picture of diverse pathways that control oxidative stress response, ranging from the TCA cycle and DNA repair machineries to iron transport, trafficking, and metabolism. Paradoxically, disrupting the pentose phosphate pathway (PPP) at the level of phosphogluconate dehydrogenase (PGD) protects cells against ROS. This dramatically alters metabolites in the PPP, consistent with rewiring of upper glycolysis to promote antioxidant production. In addition, disruption of peroxisomal import unexpectedly increases resistance to oxidative stress by altering the localization of catalase. Together, these studies provide insights into the roles of peroxisomal matrix import and the PPP in redox biology and represent a rich resource for understanding the cellular response to oxidative stress.

    View details for DOI 10.1016/j.celrep.2020.01.013

    View details for PubMedID 32023459

  • Kinetic Heterogeneity of Cancer Cell Fractional Killing. Cell reports Inde, Z. n., Forcina, G. C., Denton, K. n., Dixon, S. J. 2020; 32 (1): 107845


    Lethal drugs can induce incomplete cell death in a population of cancer cells, a phenomenon referred to as fractional killing. Here, we show that high-throughput population-level time-lapse imaging can be used to quantify fractional killing in response to hundreds of different drug treatments in parallel. We find that stable intermediate levels of fractional killing are uncommon, with many drug treatments resulting in complete or near-complete eradication of all cells, if given enough time. The kinetics of fractional killing over time vary substantially as a function of drug, drug dose, and genetic background. At the molecular level, the antiapoptotic protein MCL1 is an important determinant of the kinetics of fractional killing in response to MAPK pathway inhibitors but not other lethal stimuli. These studies suggest that fractional killing is governed by diverse lethal stimulus-specific mechanisms.

    View details for DOI 10.1016/j.celrep.2020.107845

    View details for PubMedID 32640215

  • Reactivity-Based Probe of the Iron(II)-Dependent Interactome Identifies New Cellular Modulators of Ferroptosis. Journal of the American Chemical Society Chen, Y. C., Oses-Prieto, J. A., Pope, L. E., Burlingame, A. L., Dixon, S. J., Renslo, A. R. 2020


    Ferroptosis is an iron-dependent form of cell death resulting from loss or inhibition of cellular machinery that protects from the accumulation of lipid hydroperoxides. Ferroptosis likely serves a tumor suppressing function in normal cellular homeostasis, but certain cancers exploit and become highly dependent on specific nodes of the pathway, presumably to survive under conditions of increased oxidative stress and elevated labile ferrous iron levels. Here we introduce Ferroptosis Inducing Peroxide for Chemoproteomics-1 (FIPC-1), a reactivity-based probe that couples Fenton-type reaction with ferrous iron to subsequent protein labeling via concomitant carbon-centered radical generation. We show that FIPC-1 induces ferroptosis in susceptible cell types and labels cellular proteins in an iron-dependent fashion. Use of FIPC-1 in a quantitative chemoproteomics workflow reproducibly enriched protein targets in the thioredoxin, oxidoreductase, and protein disulfide isomerase (PDI) families, among others. In further interrogating the saturable targets of FIPC-1, we identified the PDI family member P4HB and the functionally uncharacterized protein NT5DC2, a member of the haloacid dehalogenase (HAD) superfamily, as previously unrecognized modulators of ferroptosis. Knockdown of these target genes sensitized cells to known ferroptosis inducers, while PACMA31, a previously reported inhibitor of P4HB, directly induced ferroptosis and was highly synergistic with erastin. Overall, this study introduces a new reactivity-based probe of the ferrous iron-dependent interactome and uncovers new targets for the therapeutic modulation of ferroptosis.

    View details for DOI 10.1021/jacs.0c06709

    View details for PubMedID 33124817

  • p53 deficiency triggers dysregulation of diverse cellular processes in physiological oxygen. The Journal of cell biology Valente, L. J., Tarangelo, A. n., Li, A. M., Naciri, M. n., Raj, N. n., Boutelle, A. M., Li, Y. n., Mello, S. S., Bieging-Rolett, K. n., DeBerardinis, R. J., Ye, J. n., Dixon, S. J., Attardi, L. D. 2020; 219 (11)


    The mechanisms by which TP53, the most frequently mutated gene in human cancer, suppresses tumorigenesis remain unclear. p53 modulates various cellular processes, such as apoptosis and proliferation, which has led to distinct cellular mechanisms being proposed for p53-mediated tumor suppression in different contexts. Here, we asked whether during tumor suppression p53 might instead regulate a wide range of cellular processes. Analysis of mouse and human oncogene-expressing wild-type and p53-deficient cells in physiological oxygen conditions revealed that p53 loss concurrently impacts numerous distinct cellular processes, including apoptosis, genome stabilization, DNA repair, metabolism, migration, and invasion. Notably, some phenotypes were uncovered only in physiological oxygen. Transcriptomic analysis in this setting highlighted underappreciated functions modulated by p53, including actin dynamics. Collectively, these results suggest that p53 simultaneously governs diverse cellular processes during transformation suppression, an aspect of p53 function that would provide a clear rationale for its frequent inactivation in human cancer.

    View details for DOI 10.1083/jcb.201908212

    View details for PubMedID 32886745

  • Dietary Lipids Induce Ferroptosis in Caenorhabditiselegans and Human Cancer Cells. Developmental cell Perez, M. A., Magtanong, L. n., Dixon, S. J., Watts, J. L. 2020


    Dietary lipids impact development, homeostasis, and disease, but links between specific dietary fats and cell fates are poorly understood. Ferroptosis is an iron-dependent form of nonapoptotic cell death associated with oxidized polyunsaturated phospholipids. Here, we show that dietary ingestion of the polyunsaturated fatty acid (PUFA) dihomogamma-linolenic acid (DGLA; 20:3n-6) can trigger germ-cell ferroptosis and sterility in the nematode Caenorhabditis elegans. Exogenous DGLA is also sufficient to induce ferroptosis in human cells, pinpointing this omega-6 PUFA as a conserved metabolic instigator of this lethal process. In both C. elegans and human cancer cells, ether-lipid synthesis protects against ferroptosis. These results establish C. elegans as a powerful animal model to study the induction and modulation of ferroptosis by dietary fats and indicate that endogenous ether lipids act to prevent this nonapoptotic cell fate.

    View details for DOI 10.1016/j.devcel.2020.06.019

    View details for PubMedID 32652074

  • Prominin2 Drives Ferroptosis Resistance by Stimulating Iron Export. Developmental cell Brown, C. W., Amante, J. J., Chhoy, P., Elaimy, A. L., Liu, H., Zhu, L. J., Baer, C. E., Dixon, S. J., Mercurio, A. M. 2019


    Ferroptosis, regulated cell death characterized by the iron-dependent accumulation of lethal lipid reactive oxygen species, contributes to tissue homeostasis and numerous pathologies, and it may be exploited for therapy. Cells differ in their sensitivity to ferroptosis, however, and a key challenge is to understand mechanisms that contribute to resistance. Using RNA-seq to identify genes that contribute to ferroptosis resistance, we discovered that pro-ferroptotic stimuli, including inhibition of the lipid hydroperoxidase GPX4 and detachment from the extracellular matrix, induce expression of prominin2, a pentaspanin protein implicated in regulation of lipid dynamics. Prominin2 facilitates ferroptosis resistance in mammary epithelial and breast carcinoma cells. Mechanistically, prominin2 promotes the formation of ferritin-containing multivesicular bodies (MVBs) and exosomes that transport iron out of the cell, inhibiting ferroptosis. These findings reveal that ferroptosis resistance can be driven by a prominin2-MVB-exosome-ferritin pathway and have broad implications for iron homeostasis, intracellular trafficking, and cancer.

    View details for DOI 10.1016/j.devcel.2019.10.007

    View details for PubMedID 31735663

  • The CoQ oxidoreductase FSP1 acts parallel to GPX4 to inhibit ferroptosis. Nature Bersuker, K., Hendricks, J., Li, Z., Magtanong, L., Ford, B., Tang, P. H., Roberts, M. A., Tong, B., Maimone, T. J., Zoncu, R., Bassik, M. C., Nomura, D. K., Dixon, S. J., Olzmann, J. A. 2019


    Ferroptosis is a form of regulated cell death that is caused by the iron-dependent peroxidation of lipids1,2. The glutathione-dependent lipid hydroperoxidase glutathione peroxidase 4 (GPX4) prevents ferroptosis by converting lipid hydroperoxides into non-toxic lipid alcohols3,4. Ferroptosis has been implicated in the cell death that underlies several degenerative conditions2, and induction of ferroptosis by inhibition of GPX4 has emerged as a therapeutic strategy to trigger cancer cell death5. However, sensitivity to GPX4 inhibitors varies greatly across cancer cell lines6, suggesting that additional factors govern resistance to ferroptosis. Here, using a synthetic lethal CRISPR-Cas9 screen, we identify ferroptosis suppressor protein 1 (FSP1) (previously known as apoptosis-inducing factor mitochondrial 2 (AIFM2)) as a potent ferroptosis resistance factor. Our data indicate that myristoylation recruits FSP1 to the plasma membrane where it functions as an oxidoreductase that reduces coenzyme Q10 (CoQ), generating a lipophilic radical-trapping antioxidant (RTA) that halts the propagation of lipid peroxides. We further find that FSP1 expression positively correlates with ferroptosis resistance across hundreds of cancer cell lines, and that FSP1 mediates resistance to ferroptosis in lung cancer cells in culture and in mouse tumor xenografts. Thus, our data identify FSP1 as a key component of a non-mitochondrial CoQ antioxidant system that acts in parallel to the canonical glutathione-based GPX4 pathway. These findings define a new ferroptosis suppression pathway and indicate that pharmacological inhibition of FSP1 may provide an effective strategy to sensitize cancer cells to ferroptosis-inducing chemotherapeutics.

    View details for DOI 10.1038/s41586-019-1705-2

    View details for PubMedID 31634900

  • A ZDHHC5-GOLGA7 Protein Acyltransferase Complex Promotes Nonapoptotic Cell Death. Cell chemical biology Ko, P., Woodrow, C., Dubreuil, M. M., Martin, B. R., Skouta, R., Bassik, M. C., Dixon, S. J. 2019


    Lethal small molecules are useful probes to discover and characterize novel cell death pathways and biochemical mechanisms. Here we report that the synthetic oxime-containing small molecule caspase-independent lethal 56 (CIL56) induces an unconventional form of nonapoptotic cell death distinct from necroptosis, ferroptosis, and other pathways. CIL56-induced cell death requires a catalytically active protein S-acyltransferase complex comprising the enzyme ZDHHC5 and an accessory subunit GOLGA7. The ZDHHC5-GOLGA7 complex is mutually stabilizing and localizes to the plasma membrane. CIL56 inhibits anterograde protein transport from the Golgi apparatus, which may be lethal in the context of ongoing ZDHHC5-GOLGA7 complex-dependent retrograde protein trafficking from the plasma membrane to internal sites. Other oxime-containing small molecules, structurally distinct from CIL56, may trigger cell death through the same pathway. These results define an unconventional form of nonapoptotic cell death regulated by protein S-acylation.

    View details for DOI 10.1016/j.chembiol.2019.09.014

    View details for PubMedID 31631010

  • GPX4 at the Crossroads of Lipid Homeostasis and Ferroptosis PROTEOMICS Forcina, G. C., Dixon, S. J. 2019; 19 (18)
  • Kinetic analysis identifies determinants of sensitivity to MEK inhibitor-induced cell death Inde, Z., Han, K., Bassik, M. C., Dixon, S. J. AMER ASSOC CANCER RESEARCH. 2019
  • GPX4 at the Crossroads of Lipid Homeostasis and Ferroptosis. Proteomics Forcina, G. C., Dixon, S. J. 2019: e1800311


    Oxygen is necessary for aerobic metabolism but can also contribute to the harmful oxidation of lipids and other macromolecules. Oxidation of cholesterol and of phospholipids containing polyunsaturated fatty acyl chains can lead to lipid peroxidation, membrane damage and cell death. Lipid hydroperoxides are key intermediates in the process of lipid peroxidation. The lipid hydroperoxidase glutathione peroxidase 4 (GPX4) converts lipid hydroperoxides to lipid alcohols, and this process prevents the iron (Fe2+ )-dependent formation of toxic lipid reactive oxygen species (ROS). Inhibition of GPX4 function leads to increased lipid ROS formation and lipid peroxidation, and can result in the induction of ferroptosis, an iron-dependent, non-apoptotic form of cell death. In this review we describe the formation of reactive lipid species, the function of GPX4 in preventing oxidative lipid damage, and the link between GPX4 dysfunction, lipid oxidation and the induction of ferroptosis. This article is protected by copyright. All rights reserved.

    View details for PubMedID 30888116

  • Ferroptosis and Brain Injury. Developmental neuroscience Magtanong, L., Dixon, S. J. 2019: 1–14


    Ferroptosis is a nonapoptotic form of cell death characterized by the iron-dependent accumulation of toxic lipid reactive oxygen species. Small-molecule screening and subsequent optimization have yielded potent and specific activators and inhibitors of this process. These compounds have been employed to dissect the lethal mechanism and implicate this process in pathological cell death events observed in many tissues, including the brain. Indeed, ferroptosis is emerging as an important mechanism of cell death during stroke, intracerebral hemorrhage, and other acute brain injuries, and may also play a role in certain degenerative brain disorders. Outstanding issues include the practical need to identify molecular markers of ferroptosis that can be used to detect and study this process in vivo, and the more basic problem of understanding the relationship between ferroptosis and other forms of cell death that can be triggered in the brain during injury.

    View details for PubMedID 30820017

  • A Genome-wide Haploid Genetic Screen Identifies Regulators of Glutathione Abundance and Ferroptosis Sensitivity. Cell reports Cao, J. Y., Poddar, A., Magtanong, L., Lumb, J. H., Mileur, T. R., Reid, M. A., Dovey, C. M., Wang, J., Locasale, J. W., Stone, E., Cole, S. P., Carette, J. E., Dixon, S. J. 2019; 26 (6): 1544


    The tripeptide glutathione suppresses the iron-dependent, non-apoptotic cell death process of ferroptosis. How glutathione abundance is regulated in the cell and how this regulation alters ferroptosis sensitivity is poorly understood. Using genome-wide human haploid genetic screening technology coupled to fluorescence-activated cell sorting (FACS), we directly identify genes that regulate intracellular glutathione abundance and characterize their role in ferroptosis regulation. Disruption of the ATP binding cassette (ABC)-family transporter multidrug resistance protein 1 (MRP1) prevents glutathione efflux from the cell and strongly inhibits ferroptosis. High levels of MRP1 expression decrease sensitivity to certain pro-apoptotic chemotherapeutic drugs, while collaterally sensitizing to all tested pro-ferroptotic agents. By contrast, disruption of KEAP1 and NAA38, leading to the stabilization of the transcription factor NRF2, increases glutathione levels but only weakly protects from ferroptosis. This is due in part to concomitant NRF2-mediated upregulation of MRP1. These results pinpoint glutathione efflux as an unanticipated regulator of ferroptosis sensitivity.

    View details for PubMedID 30726737

  • The Hallmarks of Ferroptosis ANNUAL REVIEW OF CANCER BIOLOGY, VOL 3 Dixon, S. J., Stockwell, B. R., Jacks, T., Sawyers, C. L. 2019; 3: 35–54
  • Lipid Metabolism and Ferroptosis FERROPTOSIS IN HEALTH AND DISEASE Tarangelo, A., Dixon, S. J., Tang, D. 2019: 1–26
  • Ferroptosis and Brain Injury Magtanong, L., Dixon, S. J. KARGER. 2019: 382–95

    View details for DOI 10.1159/000496922

    View details for Web of Science ID 000477586900002

  • Exogenous Monounsaturated Fatty Acids Promote a Ferroptosis-Resistant Cell State. Cell chemical biology Magtanong, L., Ko, P., To, M., Cao, J. Y., Forcina, G. C., Tarangelo, A., Ward, C. C., Cho, K., Patti, G. J., Nomura, D. K., Olzmann, J. A., Dixon, S. J. 2018


    The initiation and execution of cell death can be regulated by various lipids. How the levels of environmental (exogenous) lipids impact cell death sensitivity is not well understood. We find that exogenous monounsaturated fatty acids (MUFAs) potently inhibit the non-apoptotic, iron-dependent, oxidative cell death process of ferroptosis. This protective effect is associated with the suppression of lipid reactive oxygen species (ROS) accumulation at the plasma membrane and decreased levels of phospholipids containing oxidizable polyunsaturated fatty acids. Treatment with exogenous MUFAs reduces the sensitivity of plasma membrane lipids to oxidation over several hours. This effect requires MUFA activation by acyl-coenzyme A synthetase long-chain family member 3 (ACSL3) and is independent of lipid droplet formation. Exogenous MUFAs also protect cells from apoptotic lipotoxicity caused by the accumulation of saturated fatty acids, but in anACSL3-independent manner. Our work demonstrates that ACSL3-dependent MUFA activation promotes a ferroptosis-resistant cell state.

    View details for PubMedID 30686757

  • Protein palmitoylation and cancer. EMBO reports Ko, P., Dixon, S. J. 2018


    Protein S-palmitoylation is a reversible post-translational modification that alters the localization, stability, and function of hundreds of proteins in the cell. S-palmitoylation is essential for the function of both oncogenes (e.g., NRAS and EGFR) and tumor suppressors (e.g., SCRIB, melanocortin 1 receptor). In mammalian cells, the thioesterification of palmitate to internal cysteine residues is catalyzed by 23 Asp-His-His-Cys (DHHC)-family palmitoyl S-acyltransferases while the removal of palmitate is catalyzed by serine hydrolases, including acyl-protein thioesterases (APTs). These enzymes modulate the function of important oncogenes and tumor suppressors and often display altered expression patterns in cancer. Targeting S-palmitoylation or the enzymes responsible for palmitoylation dynamics may therefore represent a candidate therapeutic strategy for certain cancers.

    View details for PubMedID 30232163

  • The p53-p21 pathway inhibits ferroptosis during metabolic stress. Oncotarget Tarangelo, A., Dixon, S. 2018; 9 (37): 24572–73

    View details for PubMedID 29872487

  • Molecular mechanisms of cell death: recommendations of the Nomenclature Committee on Cell Death 2018 CELL DEATH AND DIFFERENTIATION Galluzzi, L., Vitale, I., Aaronson, S. A., Abrams, J. M., Adam, D., Agostinis, P., Alnemri, E. S., Altucci, L., Amelio, I., Andrews, D. W., Annicchiarico-Petruzzelli, M., Antonov, A. V., Arama, E., Baehrecke, E. H., Barlev, N. A., Bazan, N. G., Bernassola, F., Bertrand, M. M., Bianchi, K., Blagosklonny, M. V., Blomgren, K., Borner, C., Boya, P., Brenner, C., Campanella, M., Candi, E., Carmona-Gutierrez, D., Cecconi, F., Chan, F., Chandel, N. S., Cheng, E. H., Chipuk, J. E., Cidlowski, J. A., Ciechanover, A., Cohen, G. M., Conrad, M., Cubillos-Ruiz, J. R., Czabotar, P. E., D'Angiolella, V., Dawson, T. M., Dawson, V. L., De laurenzi, V., De Maria, R., Debatin, K., DeBerardinis, R. J., Deshmukh, M., Di Daniele, N., Di Virgilio, F., Dixit, V. M., Dixon, S. J., Duckett, C. S., Dynlacht, B. D., El-Deiry, W. S., Elrod, J. W., Fimia, G., Fulda, S., Garcia-Saez, A. J., Garg, A. D., Garrido, C., Gavathiotis, E., Golstein, P., Gottlieb, E., Green, D. R., Greene, L. A., Gronemeyer, H., Gross, A., Hajnoczky, G., Hardwick, J., Harris, I. S., Hengartner, M. O., Hetz, C., Ichijo, H., Jaattela, M., Joseph, B., Jost, P. J., Juin, P. P., Kaiser, W. J., Karin, M., Kaufmann, T., Kepp, O., Kimchi, A., Kitsis, R. N., Klionsky, D. J., Knight, R. A., Kumar, S., Lee, S. W., Lemasters, J. J., Levine, B., Linkermann, A., Lipton, S. A., Lockshin, R. A., Lopez-Otin, C., Lowe, S. W., Luedde, T., Lugli, E., MacFarlane, M., Madeo, F., Malewicz, M., Malorni, W., Manic, G., Marine, J., Martin, S. J., Martinou, J., Medema, J., Mehlen, P., Meier, P., Melino, S., Miao, E. A., Molkentin, J. D., Moll, U. M., Munoz-Pinedo, C., Nagata, S., Nunez, G., Oberst, A., Oren, M., Overholtzer, M., Pagano, M., Panaretakis, T., Pasparakis, M., Penninger, J. M., Pereira, D. M., Pervaiz, S., Peter, M. E., Piacentini, M., Pinton, P., Prehn, J. M., Puthalakath, H., Rabinovich, G. A., Rehm, M., Rizzuto, R., Rodrigues, C. P., Rubinsztein, D. C., Rudel, T., Ryan, K. M., Sayan, E., Scorrano, L., Shao, F., Shi, Y., Silke, J., Simon, H., Sistigu, A., Stockwell, B. R., Strasser, A., Szabadkai, G., Tait, S. G., Tang, D., Tavernarakis, N., Thorburn, A., Tsujimoto, Y., Turk, B., Vanden Berghe, T., Vandenabeele, P., Heiden, M., Villunger, A., Virgin, H. W., Vousden, K. H., Vucic, D., Wagner, E. F., Walczak, H., Wallach, D., Wang, Y., Wells, J. A., Wood, W., Yuan, J., Zakeri, Z., Zhivotovsky, B., Zitvogel, L., Melino, G., Kroemer, G. 2018; 25 (3): 486–541


    Over the past decade, the Nomenclature Committee on Cell Death (NCCD) has formulated guidelines for the definition and interpretation of cell death from morphological, biochemical, and functional perspectives. Since the field continues to expand and novel mechanisms that orchestrate multiple cell death pathways are unveiled, we propose an updated classification of cell death subroutines focusing on mechanistic and essential (as opposed to correlative and dispensable) aspects of the process. As we provide molecularly oriented definitions of terms including intrinsic apoptosis, extrinsic apoptosis, mitochondrial permeability transition (MPT)-driven necrosis, necroptosis, ferroptosis, pyroptosis, parthanatos, entotic cell death, NETotic cell death, lysosome-dependent cell death, autophagy-dependent cell death, immunogenic cell death, cellular senescence, and mitotic catastrophe, we discuss the utility of neologisms that refer to highly specialized instances of these processes. The mission of the NCCD is to provide a widely accepted nomenclature on cell death in support of the continued development of the field.

    View details for PubMedID 29362479

  • p53 Suppresses Metabolic Stress-Induced Ferroptosis in Cancer Cells CELL REPORTS Tarangelo, A., Magtanong, L., Bieging-Rolett, K. T., Li, Y., Ye, J., Attardi, L. D., Dixon, S. J. 2018; 22 (3): 569–75


    How cancer cells respond to nutrient deprivation remains poorly understood. In certain cancer cells, deprivation of cystine induces a non-apoptotic, iron-dependent form of cell death termed ferroptosis. Recent evidence suggests that ferroptosis sensitivity may be modulated by the stress-responsive transcription factor and canonical tumor suppressor protein p53. Using CRISPR/Cas9 genome editing, small-molecule probes, and high-resolution, time-lapse imaging, we find that stabilization of wild-type p53 delays the onset of ferroptosis in response to cystine deprivation. This delay requires the p53 transcriptional target CDKN1A (encoding p21) and is associated with both slower depletion of intracellular glutathione and a reduced accumulation of toxic lipid-reactive oxygen species (ROS). Thus, the p53-p21 axis may help cancer cells cope with metabolic stress induced by cystine deprivation by delaying the onset of non-apoptotic cell death.

    View details for PubMedID 29346757

  • MLKL Requires the Inositol Phosphate Code to Execute Necroptosis. Molecular cell Dovey, C. M., Diep, J. n., Clarke, B. P., Hale, A. T., McNamara, D. E., Guo, H. n., Brown, N. W., Cao, J. Y., Grace, C. R., Gough, P. J., Bertin, J. n., Dixon, S. J., Fiedler, D. n., Mocarski, E. S., Kaiser, W. J., Moldoveanu, T. n., York, J. D., Carette, J. E. 2018; 70 (5): 936–48.e7


    Necroptosis is an important form of lytic cell death triggered by injury and infection, but whether mixed lineage kinase domain-like (MLKL) is sufficient to execute this pathway is unknown. In a genetic selection for human cell mutants defective for MLKL-dependent necroptosis, we identified mutations in IPMK and ITPK1, which encode inositol phosphate (IP) kinases that regulate the IP code of soluble molecules. We show that IP kinases are essential for necroptosis triggered by death receptor activation, herpesvirus infection, or a pro-necrotic MLKL mutant. In IP kinase mutant cells, MLKL failed to oligomerize and localize to membranes despite proper receptor-interacting protein kinase-3 (RIPK3)-dependent phosphorylation. We demonstrate that necroptosis requires IP-specific kinase activity and that a highly phosphorylated product, but not a lowly phosphorylated precursor, potently displaces the MLKL auto-inhibitory brace region. These observations reveal control of MLKL-mediated necroptosis by a metabolite and identify a key molecular mechanism underlying regulated cell death.

    View details for PubMedID 29883610

  • The impact of non-genetic heterogeneity on cancer cell death CRITICAL REVIEWS IN BIOCHEMISTRY AND MOLECULAR BIOLOGY Inde, Z., Dixon, S. J. 2018; 53 (1): 99–114


    The goal of cancer chemotherapy is to induce homogeneous cell death within the population of targeted cancer cells. However, no two cells are exactly alike at the molecular level, and sensitivity to drug-induced cell death, therefore, varies within a population. Genetic alterations can contribute to this variability and lead to selection for drug resistant clones. However, there is a growing appreciation for the role of non-genetic variation in producing drug-tolerant cellular states that exhibit reduced sensitivity to cell death for extended periods of time, from hours to weeks. These cellular states may result from individual variation in epigenetics, gene expression, metabolism, and other processes that impact drug mechanism of action or the execution of cell death. Such population-level non-genetic heterogeneity may contribute to treatment failure and provide a cellular "substrate" for the emergence of genetic alterations that confer frank drug resistance.

    View details for PubMedID 29250983

  • Ferroptosis: A Regulated Cell Death Nexus Linking Metabolism, Redox Biology, and Disease CELL Stockwell, B. R., Angeli, J., Bayir, H., Bush, A. I., Conrad, M., Dixon, S. J., Fulda, S., Gascon, S., Hatzios, S. K., Kagan, V. E., Noel, K., Jiang, X., Linkermann, A., Murphy, M. E., Overholtzer, M., Oyagi, A., Pagnussat, G. C., Park, J., Ran, Q., Rosenfeld, C. S., Salnikow, K., Tang, D., Torti, F. M., Torti, S. V., Toyokuni, S., Woerpel, K. A., Zhang, D. D. 2017; 171 (2): 273–85


    Ferroptosis is a form of regulated cell death characterized by the iron-dependent accumulation of lipid hydroperoxides to lethal levels. Emerging evidence suggests that ferroptosis represents an ancient vulnerability caused by the incorporation of polyunsaturated fatty acids into cellular membranes, and cells have developed complex systems that exploit and defend against this vulnerability in different contexts. The sensitivity to ferroptosis is tightly linked to numerous biological processes, including amino acid, iron, and polyunsaturated fatty acid metabolism, and the biosynthesis of glutathione, phospholipids, NADPH, and coenzyme Q10. Ferroptosis has been implicated in the pathological cell death associated with degenerative diseases (i.e., Alzheimer's, Huntington's, and Parkinson's diseases), carcinogenesis, stroke, intracerebral hemorrhage, traumatic brain injury, ischemia-reperfusion injury, and kidney degeneration in mammals and is also implicated in heat stress in plants. Ferroptosis may also have a tumor-suppressor function that could be harnessed for cancer therapy. This Primer reviews the mechanisms underlying ferroptosis, highlights connections to other areas of biology and medicine, and recommends tools and guidelines for studying this emerging form of regulated cell death.

    View details for PubMedID 28985560

    View details for PubMedCentralID PMC5685180

  • Systematic Quantification of Population Cell Death Kinetics in Mammalian Cells. Cell systems Forcina, G. C., Conlon, M., Wells, A., Cao, J. Y., Dixon, S. J. 2017; 4 (6): 600-610.e6


    Cytotoxic compounds are important drugs and research tools. Here, we introduce a method, scalable time-lapse analysis of cell death kinetics (STACK), to quantify the kinetics of compound-induced cell death in mammalian cells at the population level. STACK uses live and dead cell markers, high-throughput time-lapse imaging, and mathematical modeling to determine the kinetics of population cell death over time. We used STACK to profile the effects of over 1,800 bioactive compounds on cell death in two human cancer cell lines, resulting in a large and freely available dataset. 79 potent lethal compounds common to both cell lines caused cell death with widely divergent kinetics. 13 compounds triggered cell death within hours, including the metallophore zinc pyrithione. Mechanistic studies demonstrated that this rapid onset lethal phenotype was caused in human cancer cells by metabolic disruption and ATP depletion. These results provide the first comprehensive survey of cell death kinetics and analysis of rapid-onset lethal compounds.

    View details for DOI 10.1016/j.cels.2017.05.002

    View details for PubMedID 28601558

    View details for PubMedCentralID PMC5509363

  • Ferroptosis: bug or feature? IMMUNOLOGICAL REVIEWS Dixon, S. J. 2017; 277 (1): 150-157


    Ferroptosis is an iron-dependent, oxidative form of non-apoptotic cell death. This form of cell death does not share morphological, biochemical, or genetic similarities with classic necrosis, necroptosis, parthanatos, or other forms of non-apoptotic cell death. Ferroptosis can be triggered by depleting the cell of the amino acid cysteine, or by inhibiting the phospholipid hydroperoxidase glutathione peroxidase 4 (GPX4). Why certain stimuli trigger ferroptosis instead of another form of cell death, and whether this process could be adaptive in vivo, are two major unanswered questions concerning this process. Emerging evidence and consideration of related non-apoptotic pathways suggest that ferroptosis could be an adaptive process, albeit one regulated and executed in a manner very different from apoptosis and other forms of cell death.

    View details for DOI 10.1111/imr.12533

    View details for Web of Science ID 000400377200011

    View details for PubMedID 28462529

  • Ferroptosis-like death in plant cells. Molecular & cellular oncology Conlon, M., Dixon, S. J. 2017; 4 (3): e1302906


    Ferroptosis is an iron-dependent, oxidative, non-apoptotic form of cell death initially described in mammalian cells. We recently reported that a ferroptosis-like cell death process can be triggered by heat shock in Arabidopsis thaliana. Thus, ferroptosis may be a form of cell death conserved between animals and plants.

    View details for DOI 10.1080/23723556.2017.1302906

    View details for PubMedID 28616580

    View details for PubMedCentralID PMC5462507

  • Heat stress induces ferroptosis-like cell death in plants. journal of cell biology Distéfano, A. M., Martin, M. V., Córdoba, J. P., Bellido, A. M., D'Ippólito, S., Colman, S. L., Soto, D., Roldán, J. A., Bartoli, C. G., Zabaleta, E. J., Fiol, D. F., Stockwell, B. R., Dixon, S. J., Pagnussat, G. C. 2017; 216 (2): 463-476


    In plants, regulated cell death (RCD) plays critical roles during development and is essential for plant-specific responses to abiotic and biotic stresses. Ferroptosis is an iron-dependent, oxidative, nonapoptotic form of cell death recently described in animal cells. In animal cells, this process can be triggered by depletion of glutathione (GSH) and accumulation of lipid reactive oxygen species (ROS). We investigated whether a similar process could be relevant to cell death in plants. Remarkably, heat shock (HS)-induced RCD, but not reproductive or vascular development, was found to involve a ferroptosis-like cell death process. In root cells, HS triggered an iron-dependent cell death pathway that was characterized by depletion of GSH and ascorbic acid and accumulation of cytosolic and lipid ROS. These results suggest a physiological role for this lethal pathway in response to heat stress in Arabidopsis thaliana The similarity of ferroptosis in animal cells and ferroptosis-like death in plants suggests that oxidative, iron-dependent cell death programs may be evolutionarily ancient.

    View details for DOI 10.1083/jcb.201605110

    View details for PubMedID 28100685

    View details for PubMedCentralID PMC5294777

  • Nanomedicine: An iron age for cancer therapy. Nature nanotechnology Tarangelo, A., Dixon, S. J. 2016; 11 (11): 921-922

    View details for DOI 10.1038/nnano.2016.199

    View details for PubMedID 27668797

  • Global survey of cell death mechanisms reveals metabolic regulation of ferroptosis NATURE CHEMICAL BIOLOGY Shimada, K., Skouta, R., Kaplan, A., Yang, W. S., Hayano, M., Dixon, S. J., Brown, L. M., Valenzuela, C. A., Wolpaw, A. J., Stockwell, B. R. 2016; 12 (7): 497-?


    Apoptosis is one type of programmed cell death. Increasingly, non-apoptotic cell death is recognized as being genetically controlled, or 'regulated'. However, the full extent and diversity of alternative cell death mechanisms remain uncharted. Here we surveyed the landscape of pharmacologically accessible cell death mechanisms. In an examination of 56 caspase-independent lethal compounds, modulatory profiling showed that 10 compounds induced three different types of regulated non-apoptotic cell death. Optimization of one of those ten resulted in the discovery of FIN56, a specific inducer of ferroptosis. Ferroptosis has been found to occur when the lipid-repair enzyme GPX4 is inhibited. FIN56 promoted degradation of GPX4. FIN56 also bound to and activated squalene synthase, an enzyme involved in isoprenoid biosynthesis, independent of GPX4 degradation. These discoveries show that dysregulation of lipid metabolism is associated with ferroptosis. This systematic approach is a means to discover and characterize novel cell death phenotypes.

    View details for DOI 10.1038/NCHEMBIO.2079

    View details for Web of Science ID 000378087500008

    View details for PubMedID 27159577

  • Mechanisms of ferroptosis CELLULAR AND MOLECULAR LIFE SCIENCES Cao, J. Y., Dixon, S. J. 2016; 73 (11-12): 2195-2209


    Ferroptosis is a non-apoptotic form of cell death that can be triggered by small molecules or conditions that inhibit glutathione biosynthesis or the glutathione-dependent antioxidant enzyme glutathione peroxidase 4 (GPX4). This lethal process is defined by the iron-dependent accumulation of lipid reactive oxygen species and depletion of plasma membrane polyunsaturated fatty acids. Cancer cells with high level RAS-RAF-MEK pathway activity or p53 expression may be sensitized to this process. Conversely, a number of small molecule inhibitors of ferroptosis have been identified, including ferrostatin-1 and liproxstatin-1, which can block pathological cell death events in brain, kidney and other tissues. Recent work has identified a number of genes required for ferroptosis, including those involved in lipid and amino acid metabolism. Outstanding questions include the relationship between ferroptosis and other forms of cell death, and whether activation or inhibition of ferroptosis can be exploited to achieve desirable therapeutic ends.

    View details for DOI 10.1007/s00018-016-2194-1

    View details for Web of Science ID 000377775800008

    View details for PubMedID 27048822

  • Emerging roles for lipids in non-apoptotic cell death. Cell death and differentiation Magtanong, L., Ko, P. J., Dixon, S. J. 2016


    Non-apoptotic regulated cell death (RCD) is essential to maintain organismal homeostasis and may be aberrantly activated during certain pathological states. Lipids are emerging as key components of several non-apoptotic RCD pathways. For example, a direct interaction between membrane phospholipids and the pore-forming protein mixed lineage kinase domain-like (MLKL) is needed for the execution of necroptosis, while the oxidative destruction of membrane polyunsaturated fatty acids (PUFAs), following the inactivation of glutathione peroxidase 4 (GPX4), is a requisite gateway to ferroptosis. Here, we review the roles of lipids in the initiation and execution of these and other forms of non-apoptotic cell death. We also consider new technologies that are allowing for the roles of lipids and lipid metabolism in RCD to be probed in increasingly sophisticated ways. In certain cases, this new knowledge may enable the development of therapies that target lipids and lipid metabolic processes to enhance or suppress specific non-apoptotic RCD pathways.Cell Death and Differentiation advance online publication, 11 March 2016; doi:10.1038/cdd.2016.25.

    View details for DOI 10.1038/cdd.2016.25

    View details for PubMedID 26967968

  • Connectivity Homology Enables Inter-Species Network Models of Synthetic Lethality PLOS COMPUTATIONAL BIOLOGY Jacunski, A., Dixon, S. J., Tatonetti, N. P. 2015; 11 (10)


    Synthetic lethality is a genetic interaction wherein two otherwise nonessential genes cause cellular inviability when knocked out simultaneously. Drugs can mimic genetic knock-out effects; therefore, our understanding of promiscuous drugs, polypharmacology-related adverse drug reactions, and multi-drug therapies, especially cancer combination therapy, may be informed by a deeper understanding of synthetic lethality. However, the colossal experimental burden in humans necessitates in silico methods to guide the identification of synthetic lethal pairs. Here, we present SINaTRA (Species-INdependent TRAnslation), a network-based methodology that discovers genome-wide synthetic lethality in translation between species. SINaTRA uses connectivity homology, defined as biological connectivity patterns that persist across species, to identify synthetic lethal pairs. Importantly, our approach does not rely on genetic homology or structural and functional similarity, and it significantly outperforms models utilizing these data. We validate SINaTRA by predicting synthetic lethality in S. pombe using S. cerevisiae data, then identify over one million putative human synthetic lethal pairs to guide experimental approaches. We highlight the translational applications of our algorithm for drug discovery by identifying clusters of genes significantly enriched for single- and multi-drug cancer therapies.

    View details for DOI 10.1371/journal.pcbi.1004506

    View details for Web of Science ID 000364399700046

    View details for PubMedID 26451775

  • Human Haploid Cell Genetics Reveals Roles for Lipid Metabolism Genes in Nonapoptotic Cell Death. ACS chemical biology Dixon, S. J., Winter, G. E., Musavi, L. S., Lee, E. D., Snijder, B., Rebsamen, M., Superti-Furga, G., Stockwell, B. R. 2015; 10 (7): 1604-9


    Little is known about the regulation of nonapoptotic cell death. Using massive insertional mutagenesis of haploid KBM7 cells we identified nine genes involved in small-molecule-induced nonapoptotic cell death, including mediators of fatty acid metabolism (ACSL4) and lipid remodeling (LPCAT3) in ferroptosis. One novel compound, CIL56, triggered cell death dependent upon the rate-limiting de novo lipid synthetic enzyme ACC1. These results provide insight into the genetic regulation of cell death and highlight the central role of lipid metabolism in nonapoptotic cell death.

    View details for DOI 10.1021/acschembio.5b00245

    View details for PubMedID 25965523

    View details for PubMedCentralID PMC4509420

  • Human Haploid Cell Genetics Reveals Roles for Lipid Metabolism Genes in Nonapoptotic Cell Death ACS CHEMICAL BIOLOGY Dixon, S. J., Winter, G. E., Musavi, L. S., Lee, E. D., Snijder, B., Rebsamen, M., Superti-Furga, G., Stockwell, B. R. 2015; 10 (7): 1604-1609


    Little is known about the regulation of nonapoptotic cell death. Using massive insertional mutagenesis of haploid KBM7 cells we identified nine genes involved in small-molecule-induced nonapoptotic cell death, including mediators of fatty acid metabolism (ACSL4) and lipid remodeling (LPCAT3) in ferroptosis. One novel compound, CIL56, triggered cell death dependent upon the rate-limiting de novo lipid synthetic enzyme ACC1. These results provide insight into the genetic regulation of cell death and highlight the central role of lipid metabolism in nonapoptotic cell death.

    View details for DOI 10.1021/acschembio.5b00245

    View details for Web of Science ID 000358395300004

    View details for PubMedCentralID PMC4509420

  • Pharmacological inhibition of cystine-glutamate exchange induces endoplasmic reticulum stress and ferroptosis ELIFE Dixon, S. J., Patel, D., Welsch, M., Skouta, R., Lee, E., Hayano, M., Thomas, A. G., Gleason, C., Tatonetti, N., Slusher, B. S., Stockwell, B. R. 2014; 3


    Exchange of extracellular cystine for intracellular glutamate by the antiporter system xc (-) is implicated in numerous pathologies. Pharmacological agents that inhibit system xc (-) activity with high potency have long been sought, but have remained elusive. In this study, we report that the small molecule erastin is a potent, selective inhibitor of system xc (-). RNA sequencing revealed that inhibition of cystine-glutamate exchange leads to activation of an ER stress response and upregulation of CHAC1, providing a pharmacodynamic marker for system xc (-) inhibition. We also found that the clinically approved anti-cancer drug sorafenib, but not other kinase inhibitors, inhibits system xc (-) function and can trigger ER stress and ferroptosis. In an analysis of hospital records and adverse event reports, we found that patients treated with sorafenib exhibited unique metabolic and phenotypic alterations compared to patients treated with other kinase-inhibiting drugs. Finally, using a genetic approach, we identified new genes dramatically upregulated in cells resistant to ferroptosis.DOI:

    View details for DOI 10.7554/eLife.02523

    View details for Web of Science ID 000336253000003

    View details for PubMedID 24844246

  • Ferrostatins Inhibit Oxidative Lipid Damage and Cell Death in Diverse Disease Models JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Skouta, R., Dixon, S. J., Wang, J., Dunn, D. E., Orman, M., Shimada, K., Rosenberg, P. A., Lo, D. C., Weinberg, J. M., Linkermann, A., Stockwell, B. R. 2014; 136 (12): 4551-4556


    Ferrostatin-1 (Fer-1) inhibits ferroptosis, a form of regulated, oxidative, nonapoptotic cell death. We found that Fer-1 inhibited cell death in cellular models of Huntington's disease (HD), periventricular leukomalacia (PVL), and kidney dysfunction; Fer-1 inhibited lipid peroxidation, but not mitochondrial reactive oxygen species formation or lysosomal membrane permeability. We developed a mechanistic model to explain the activity of Fer-1, which guided the development of ferrostatins with improved properties. These studies suggest numerous therapeutic uses for ferrostatins, and that lipid peroxidation mediates diverse disease phenotypes.

    View details for DOI 10.1021/ja411006a

    View details for Web of Science ID 000333551800021

    View details for PubMedID 24592866

  • The role of iron and reactive oxygen species in cell death NATURE CHEMICAL BIOLOGY Dixon, S. J., Stockwell, B. R. 2014; 10 (1): 9-17
  • Ferroptosis: An Iron-Dependent Form of Nonapoptotic Cell Death CELL Dixon, S. J., Lemberg, K. M., Lamprecht, M. R., Skouta, R., Zaitsev, E. M., Gleason, C. E., Patel, D. N., Bauer, A. J., Cantley, A. M., Yang, W. S., Morrison, B., Stockwell, B. R. 2012; 149 (5): 1060-1072


    Nonapoptotic forms of cell death may facilitate the selective elimination of some tumor cells or be activated in specific pathological states. The oncogenic RAS-selective lethal small molecule erastin triggers a unique iron-dependent form of nonapoptotic cell death that we term ferroptosis. Ferroptosis is dependent upon intracellular iron, but not other metals, and is morphologically, biochemically, and genetically distinct from apoptosis, necrosis, and autophagy. We identify the small molecule ferrostatin-1 as a potent inhibitor of ferroptosis in cancer cells and glutamate-induced cell death in organotypic rat brain slices, suggesting similarities between these two processes. Indeed, erastin, like glutamate, inhibits cystine uptake by the cystine/glutamate antiporter (system x(c)(-)), creating a void in the antioxidant defenses of the cell and ultimately leading to iron-dependent, oxidative death. Thus, activation of ferroptosis results in the nonapoptotic destruction of certain cancer cells, whereas inhibition of this process may protect organisms from neurodegeneration.

    View details for DOI 10.1016/j.cell.2012.03.042

    View details for Web of Science ID 000304453900012

    View details for PubMedID 22632970

  • DRUG DISCOVERY Engineering drug combinations NATURE CHEMICAL BIOLOGY Dixon, S. J., Stockwell, B. R. 2010; 6 (5): 318-319

    View details for DOI 10.1038/nchembio.353

    View details for Web of Science ID 000276823200007

    View details for PubMedID 20404820

  • Identifying druggable disease-modifying gene products CURRENT OPINION IN CHEMICAL BIOLOGY Dixon, S. J., Stockwell, B. R. 2009; 13 (5-6): 549-555


    Many disease genes encode proteins that are difficult to target directly using small molecule drugs. Improvements in libraries based on synthetic compounds, natural products, and other types of molecules may ultimately allow some challenging proteins to be successfully targeted; however, these developments alone are unlikely to be sufficient. A complementary strategy exploits the functional interconnectivity of intracellular networks to find druggable targets lying upstream, downstream, or in parallel to a disease-causing gene, where modulation can influence the disease process indirectly. These targets can be selected using prior knowledge of disease-associated pathways or identified using phenotypic chemical and genetic screens in model organisms and cells. These approaches should facilitate the identification of effective drug targets for many genetic disorders.

    View details for DOI 10.1016/j.cbpa.2009.08.003

    View details for Web of Science ID 000272984600008

    View details for PubMedID 19740696

  • An UNC-40 pathway directs postsynaptic membrane extension in Caenorhabditis elegans DEVELOPMENT Alexander, M., Chan, K. K., Byrne, A. B., Selman, G., Lee, T., Ono, J., Wong, E., Puckrin, R., Dixon, S. J., Roy, P. J. 2009; 136 (6): 911-922


    The postsynaptic membrane of the embryonic neuromuscular junction undergoes a dramatic expansion during later development to facilitate the depolarization of larger muscles. In C. elegans, the postsynaptic membrane resides at the termini of plasma membrane extensions called muscle arms. Membrane extension to the motor axons during larval development doubles the number of muscle arms, making them a tractable model to investigate both postsynaptic membrane expansion and guided membrane extension. To identify genes required for muscle arm extension, we performed a forward screen for mutants with fewer muscle arms. We isolated 23 mutations in 14 genes, including unc-40/Dcc, which encodes a transmembrane receptor that guides the migration of cells and extending axons in response to the secreted UNC-6/Netrin spatial cue. We discovered that UNC-40 is enriched at muscle arm termini and functions cell-autonomously to direct arm extension to the motor axons. Surprisingly, UNC-6 is dispensable for muscle arm extension, suggesting that UNC-40 relies on other spatial cues to direct arm extension. We provide the first evidence that the guanine-nucleotide exchange factor UNC-73/Trio, members of the WAVE actin-polymerization complex, and a homolog of the focal adhesion complex can function downstream of UNC-40 to direct membrane extension. Our work is the first to define a pathway for directed muscle membrane extension and illustrates that axon guidance components can play key roles in postsynaptic membrane expansion.

    View details for DOI 10.1242/dev.030759

    View details for Web of Science ID 000263558100005

    View details for PubMedID 19211675

  • Systematic Mapping of Genetic Interaction Networks ANNUAL REVIEW OF GENETICS Dixon, S. J., Costanzo, M., Baryshnikova, A., Andrews, B., Boone, C. 2009; 43: 601-625


    Genetic interactions influencing a phenotype of interest can be identified systematically using libraries of genetic tools that perturb biological systems in a defined manner. Systematic screens conducted in the yeast Saccharomyces cerevisiae have identified thousands of genetic interactions and provided insight into the global structure of biological networks. Techniques enabling systematic genetic interaction mapping have been extended to other single-celled organisms, the bacteria Escherichia coli and the yeast Schizosaccharomyces pombe, opening the way to comparative investigations of interaction networks. Genetic interaction screens in Caenorhabditis elegans, Drosophila melanogaster, and mammalian models are helping to improve our understanding of metazoan-specific signaling pathways. Together, our emerging knowledge of the genetic wiring diagrams of eukaryotic and prokaryotic cells is providing a new understanding of the relationship between genotype and phenotype.

    View details for DOI 10.1146/annurev.genet.39.073003.114751

    View details for Web of Science ID 000273580300024

    View details for PubMedID 19712041

  • Significant conservation of synthetic lethal genetic interaction networks between distantly related eukaryotes PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Dixon, S. J., Fedyshyn, Y., Koh, J. L., Prasad, T. S., Chahwan, C., Chua, G., Toufighi, K., Baryshnikova, A., Hayles, J., Hoe, K., Kim, D., Park, H., Myers, C. L., Pandey, A., Durocher, D., Andrews, B. J., Boone, C. 2008; 105 (43): 16653-16658


    Synthetic lethal genetic interaction networks define genes that work together to control essential functions and have been studied extensively in Saccharomyces cerevisiae using the synthetic genetic array (SGA) analysis technique (ScSGA). The extent to which synthetic lethal or other genetic interaction networks are conserved between species remains uncertain. To address this question, we compared literature-curated and experimentally derived genetic interaction networks for two distantly related yeasts, Schizosaccharomyces pombe and S. cerevisiae. We find that 23% of interactions in a novel, high-quality S. pombe literature-curated network are conserved in the existing S. cerevisiae network. Next, we developed a method, called S. pombe SGA analysis (SpSGA), enabling rapid, high-throughput isolation of genetic interactions in this species. Direct comparison by SpSGA and ScSGA of approximately 220 genes involved in DNA replication, the DNA damage response, chromatin remodeling, intracellular transport, and other processes revealed that approximately 29% of genetic interactions are common to both species, with the remainder exhibiting unique, species-specific patterns of genetic connectivity. We define a conserved yeast network (CYN) composed of 106 genes and 144 interactions and suggest that this network may help understand the shared biology of diverse eukaryotic species.

    View details for DOI 10.1073/pnas.0806261105

    View details for Web of Science ID 000260913500046

    View details for PubMedID 18931302

  • Insulin-like signaling negatively regulates muscle arm extension through DAF-12 in Caenorhabditis elegans DEVELOPMENTAL BIOLOGY Dixon, S. J., Alexander, M., Chan, K. K., Roy, P. J. 2008; 318 (1): 153-161


    The body wall muscles (BWMs) of nematodes are connected to motor axons by muscle membrane extensions called muscle arms. To better understand how muscle arm extension is regulated, we screened conserved receptor tyrosine kinases for muscle arm defects in Caenorhabditis elegans. We discovered that mutations in daf-2, which encodes the only insulin-like receptor tyrosine kinase, confer a supernumerary muscle arm (Sna) phenotype. The Sna phenotype of daf-2 mutants is suppressed by loss-of-function in the canonical downstream FOXO-family transcription factor DAF-16 in either the muscles or the intestine, demonstrating that insulin-like signaling can regulate muscle arm extension non-autonomously. Furthermore, supernumerary arm extension requires the B isoform of the down-stream DAF-12 nuclear hormone receptor, which lacks the DNA-binding domain, but retains the ligand-binding domain. daf-2 regulates many processes in C. elegans including entry into dauer, which is a diapause-like state that facilitates survival of harsh environmental conditions. We found that wild-type dauers are also Sna. Unlike other changes associated with dauer, however, the Sna phenotype of dauers persists in recovered adults. Finally, disruption of a TGF-beta pathway that regulates dauer formation in parallel to the insulin-like pathway also confers the Sna phenotype. We conclude that supernumerary muscle arms are a novel dauer-specific modification that may facilitate some aspect of dauer behavior.

    View details for DOI 10.1016/j.ydbio.2008.03.019

    View details for Web of Science ID 000256254200015

    View details for PubMedID 18436204

  • FGF negatively regulates muscle membrane extension in Caenorhabditis elegans DEVELOPMENT Dixon, S. J., Alexander, M., Fernandes, R., Ricker, N., Roy, P. J. 2006; 133 (7): 1263-1275


    Striated muscles from Drosophila and several vertebrates extend plasma membrane to facilitate the formation of the neuromuscular junction (NMJ) during development. However, the regulation of these membrane extensions is poorly understood. In C. elegans, the body wall muscles (BWMs) also have plasma membrane extensions called muscle arms that are guided to the motor axons where they form the postsynaptic element of the NMJ. To investigate the regulation of muscle membrane extension, we screened 871 genes by RNAi for ectopic muscle membrane extensions (EMEs) in C. elegans. We discovered that an FGF pathway, including let-756(FGF), egl-15(FGF receptor), sem-5(GRB2) and other genes negatively regulates plasma membrane extension from muscles. Although compromised FGF pathway activity results in EMEs, hyperactivity of the pathway disrupts larval muscle arm extension, a phenotype we call muscle arm extension defective or MAD. We show that expression of egl-15 and sem-5 in the BWMs are each necessary and sufficient to prevent EMEs. Furthermore, we demonstrate that let-756 expression from any one of several tissues can rescue the EMEs of let-756 mutants, suggesting that LET-756 does not guide muscle membrane extensions. Our screen also revealed that loss-of-function in laminin and integrin components results in both MADs and EMEs, the latter of which are suppressed by hyperactive FGF signaling. Our data are consistent with a model in which integrins and laminins are needed for directed muscle arm extension to the nerve cords, while FGF signaling provides a general mechanism to regulate muscle membrane extension.

    View details for DOI 10.1242/dev.02300

    View details for Web of Science ID 000236764100006

    View details for PubMedID 16495308

  • Muscle arm development in Caenorhabditis elegans DEVELOPMENT Dixon, S. J., Roy, P. J. 2005; 132 (13): 3079-3092


    In several types of animals, muscle cells use membrane extensions to contact motor axons during development. To better understand the process of membrane extension in muscle cells, we investigated the development of Caenorhabditis elegans muscle arms, which extend to motor axons and form the postsynaptic element of the neuromuscular junction. We found that muscle arm development is a highly regulated process: the number of muscle arms extended by each muscle, the shape of the muscle arms and the path taken by the muscle arms to reach the motor axons are largely stereotypical. We also investigated the role of several cytoskeletal components and regulators during arm development, and found that tropomyosin (LEV-11), the actin depolymerizing activity of ADF/cofilin (UNC-60B) and, surprisingly, myosin heavy chain B (UNC-54) are each required for muscle arm extension. This is the first evidence that UNC-54, which is found in thick filaments of sarcomeres, can also play a role in membrane extension. The muscle arm phenotypes produced when these genes are mutated support a 'two-phase' model that distinguishes passive muscle arm development in embryogenesis from active muscle arm extension during larval development.

    View details for DOI 10.1242/dev.01883

    View details for Web of Science ID 000231050700013

    View details for PubMedID 15930100