Rachel Turn

All Publications

• A genome-wide, CRISPR-based screen reveals new requirements for translation initiation and ubiquitination in driving adipogenic fate change. Genes & development Turn, R. E., Hilgendorf, K. I., Johnson, C. T., Han, K., Aziz-Zanjani, M. O., Swails Bollinger, S., Domizi, P., Cheng, R., Rabiee, A., Zhu, Y., Jiang, Z., Asthana, A., Demeter, J., Svensson, K. J., Bassik, M. C., Jackson, P. K. 2025

  Abstract

  In response to excess nutrients, white adipose tissue expands by both generating new adipocytes and upregulating lipogenesis in existing adipocytes. Here, we performed a genome-wide functional CRISPR screen to identify regulators of adipogenesis in the mouse 3T3-L1 preadipocyte model. In this pooled screening strategy, we used FACS to isolate populations based on lipid content, gating for fluorescence intensity of lipophilic fluorescent BODIPY dye. Additionally, we categorized whether the gene functions primarily during mitotic clonal expansion, lipogenesis, or both. We found that translation initiation and ubiquitin-dependent protein stability regulators drive both adipogenic fate change and lipogenesis. We further supported these findings with proteomics, demonstrating that essential changes in protein reprogramming can drive or inhibit 3T3-L1 adipogenesis independent of transcription. Furthermore, we demonstrated that specific branches of the hypusination pathway, a conserved regulator of translation initiation, are critical for translating adipogenic inducers of mitotic clonal expansion and that the neddylation/ubiquitin pathway modulates insulin sensitivity during lipogenesis.

  View details for DOI 10.1101/gad.352779.125

  View details for PubMedID 40675820

• Synchronized temporal-spatial analysis via microscopy and phosphoproteomics (STAMP) of quiescence. Science advances Azizzanjani, M. O., Turn, R. E., Asthana, A., Linde-Garelli, K. Y., Xu, L. A., Labrie, L. E., Mobedi, M., Jackson, P. K. 2025; 11 (17): eadt9712

  Abstract

  Coordinated cell cycle regulation is essential for homeostasis, with most cells in the body residing in quiescence (G0). Many pathologies arise due to disruptions in tissue-specific G0, yet little is known about the temporal-spatial mechanisms that establish G0 and its signaling hub, primary cilia. Mechanistic insight is limited by asynchronous model systems and failure to connect context-specific, transient mechanisms to function. To address this gap, we developed STAMP (synchronized temporal-spatial analysis via microscopy and phosphoproteomics) to track changes in cellular landscape occurring throughout G0 transition and ciliogenesis. We synchronized ciliogenesis and G0 transition in two cell models and combined microscopy with phosphoproteomics to order signals for further targeted analyses. We propose that STAMP is broadly applicable for studying temporal-spatial signaling in many biological contexts. The findings revealed through STAMP provide critical insight into healthy cellular functions often disrupted in pathologies, paving the way for targeted therapeutics.

  View details for DOI 10.1126/sciadv.adt9712

  View details for PubMedID 40279433

• Metabolic STAMP for deciphering GPCR-regulated insulin secretion by pancreatic β cells bioRxiv Aziz-Zanjani, M., Turn, R. E., Hang, Y., Asthana, A., LaBrie, L., Mobedi, M., Xu, L. A., Kim, S. K., Jackson, P. K. 2025

  View details for DOI 10.1101/2025.10.03.680349

• Antibody characterization is critical to enhance reproducibility in biomedical research. eLife Kahn, R. A., Virk, H., Laflamme, C., Houston, D. W., Polinski, N. K., Meijers, R., Levey, A. I., Saper, C. B., Errington, T. M., Turn, R. E., Bandrowski, A., Trimmer, J. S., Rego, M., Freedman, L. P., Ferrara, F., Bradbury, A. R., Cable, H., Longworth, S. 2024; 13

  Abstract

  Antibodies are used in many areas of biomedical and clinical research, but many of these antibodies have not been adequately characterized, which casts doubt on the results reported in many scientific papers. This problem is compounded by a lack of suitable control experiments in many studies. In this article we review the history of the 'antibody characterization crisis', and we document efforts and initiatives to address the problem, notably for antibodies that target human proteins. We also present recommendations for a range of stakeholders - researchers, universities, journals, antibody vendors and repositories, scientific societies and funders - to increase the reproducibility of studies that rely on antibodies.

  View details for DOI 10.7554/eLife.100211

  View details for PubMedID 39140332

• SARS-CoV-2 replication in airway epithelia requires motile cilia and microvillar reprogramming. Cell Wu, C., Lidsky, P. V., Xiao, Y., Cheng, R., Lee, I. T., Nakayama, T., Jiang, S., He, W., Demeter, J., Knight, M. G., Turn, R. E., Rojas-Hernandez, L. S., Ye, C., Chiem, K., Shon, J., Martinez-Sobrido, L., Bertozzi, C. R., Nolan, G. P., Nayak, J. V., Milla, C., Andino, R., Jackson, P. K. 2022

  Abstract

  How SARS-CoV-2 penetrates the airway barrier of mucus and periciliary mucins to infect nasal epithelium remains unclear. Using primary nasal epithelial organoid cultures, we found that the virus attaches to motile cilia via the ACE2 receptor. SARS-CoV-2 traverses the mucus layer, using motile cilia as tracks to access the cell body. Depleting cilia blocks infection for SARS-CoV-2 and other respiratory viruses. SARS-CoV-2 progeny attach to airway microvilli 24h post-infection and trigger formation of apically extended and highly branched microvilli that organize viral egress from the microvilli back into the mucus layer, supporting a model of virus dispersion throughout airway tissue via mucociliary transport. Phosphoproteomics and kinase inhibition reveal that microvillar remodeling is regulated by p21-activated kinases (PAK). Importantly, Omicron variants bind with higher affinity to motile cilia and show accelerated viral entry. Our work suggests that motile cilia, microvilli, and mucociliary-dependent mucus flow are critical for efficient virus replication in nasal epithelia.

  View details for DOI 10.1016/j.cell.2022.11.030

  View details for PubMedID 36580912

• Phylogenetic profiling and cellular analyses of ARL16 reveal roles in traffic of IFT140 and INPP5E. Molecular biology of the cell Dewees, S. I., Vargova, R., Hardin, K. R., Turn, R. E., Devi, S., Linnert, J., Wolfrum, U., Caspary, T., Elias, M., Kahn, R. A. 2022: mbcE21100509T

  Abstract

  The ARF family of regulatory GTPases is ancient, with 16 members predicted to have been present in the last eukaryotic common ancestor. Our phylogenetic profiling of paralogs in diverse species identified four family members whose presence correlates with that of a cilium/flagellum: ARL3, ARL6, ARL13, and ARL16. No prior evidence links ARL16 to cilia or other cell functions, despite its presence throughout eukaryotes. Deletion of ARL16 in MEFs results in decreased ciliogenesis yet increased ciliary length. We also found Arl16 KO in MEFs to alter ciliary protein content, including loss of ARL13B, ARL3, INPP5E, and the IFT-A core component IFT140. Instead, both INPP5E and IFT140 accumulate at the Golgi in Arl16 KO lines, while other IFT proteins do not, suggesting a specific defect in traffic from Golgi to cilia. We propose that ARL16 regulates a Golgi-cilia traffic pathway and is required specifically in the export of IFT140 and INPP5E from the Golgi.

  View details for DOI 10.1091/mbc.E21-10-0509-T

  View details for PubMedID 35196065

• Roles for ELMOD2 and Rootletin in ciliogenesis. Molecular biology of the cell Turn, R. E., Linnert, J., Gigante, E. D., Wolfrum, U., Caspary, T., Kahn, R. A. 2021; 32 (8): 800-822

  Abstract

  ELMOD2 is a GTPase-activating protein with uniquely broad specificity for ARF family GTPases. We previously showed that it acts with ARL2 in mitochondrial fusion and microtubule stability and with ARF6 during cytokinesis. Mouse embryonic fibroblasts deleted for ELMOD2 also displayed changes in cilia-related processes including increased ciliation, multiciliation, ciliary morphology, ciliary signaling, centrin accumulation inside cilia, and loss of rootlets at centrosomes with loss of centrosome cohesion. Increasing ARL2 activity or overexpressing Rootletin reversed these defects, revealing close functional links between the three proteins. This was further supported by the findings that deletion of Rootletin yielded similar phenotypes, which were rescued upon increasing ARL2 activity but not ELMOD2 overexpression. Thus, we propose that ARL2, ELMOD2, and Rootletin all act in a common pathway that suppresses spurious ciliation and maintains centrosome cohesion. Screening a number of markers of steps in the ciliation pathway supports a model in which ELMOD2, Rootletin, and ARL2 act downstream of TTBK2 and upstream of CP110 to prevent spurious release of CP110 and to regulate ciliary vesicle docking. These data thus provide evidence supporting roles for ELMOD2, Rootletin, and ARL2 in the regulation of ciliary licensing.

  View details for DOI 10.1091/mbc.E20-10-0635

  View details for PubMedID 33596093

  View details for PubMedCentralID PMC8108518

• The ARF GAPs ELMOD1 and ELMOD3 act at the Golgi and Cilia to Regulate Ciliogenesis and Ciliary Protein Traffic. Molecular biology of the cell Turn, R. E., Hu, Y., Dewees, S. I., Devi, N., East, M. P., Hardin, K. R., Khatib, T., Linnert, J., Wolfrum, U., Lim, M. J., Casanova, J. E., Caspary, T., Kahn, R. A. 2021: mbcE21090443

  Abstract

  ELMODs are a family of three mammalian paralogs that display GTPase activating protein (GAP) activity towards a uniquely broad array of ADP-ribosylation factor (ARF) family GTPases that includes ARF-like (ARL) proteins. ELMODs are ubiquitously expressed in mammalian tissues, highly conserved across eukaryotes, and ancient in origin, being present in the last eukaryotic common ancestor. We described functions of ELMOD2 in immortalized mouse embryonic fibroblasts (MEFs) in the regulation of cell division, microtubules, ciliogenesis, and mitochondrial fusion. Here, using similar strategies with the paralogs ELMOD1 and ELMOD3, we identify novel functions and locations of these cell regulators and compare them to those of ELMOD2, allowing determination of functional redundancy among the family members. We found strong similarities in phenotypes resulting from deletion of either Elmod1 or Elmod3 and marked differences from those arising in Elmod2 deletion lines. Deletion of either Elmod1 or Elmod3 results in the decreased ability of cells to form primary cilia, loss of a subset of proteins from cilia, and accumulation of some ciliary proteins at the Golgi, predicted to result from compromised traffic from the Golgi to cilia. These phenotypes are reversed upon activating mutant expression of either ARL3 or ARL16, linking their roles to ELMOD1/3 actions.

  View details for DOI 10.1091/mbc.E21-09-0443

  View details for PubMedID 34818063

• The ARF GAP ELMOD2 acts with different GTPases to regulate centrosomal microtubule nucleation and cytokinesis. Molecular biology of the cell Turn, R. E., East, M. P., Prekeris, R., Kahn, R. A. 2020; 31 (18): 2070-2091

  Abstract

  ELMOD2 is a ∼32 kDa protein first purified by its GTPase-activating protein (GAP) activity toward ARL2 and later shown to have uniquely broad specificity toward ARF family GTPases in in vitro assays. To begin the task of defining its functions in cells, we deleted ELMOD2 in immortalized mouse embryonic fibroblasts and discovered a number of cellular defects, which are reversed upon expression of ELMOD2-myc. We show that these defects, resulting from the loss of ELMOD2, are linked to two different pathways and two different GTPases: with ARL2 and TBCD to support microtubule nucleation from centrosomes and with ARF6 in cytokinesis. These data highlight key aspects of signaling by ARF family GAPs that contribute to previously underappreciated sources of complexity, including GAPs acting from multiple sites in cells, working with multiple GTPases, and contributing to the spatial and temporal control of regulatory GTPases by serving as both GAPs and effectors.

  View details for DOI 10.1091/mbc.E20-01-0012

  View details for PubMedID 32614697

  View details for PubMedCentralID PMC7543072

• ELMOD2 regulates mitochondrial fusion in a mitofusin-dependent manner, downstream of ARL2. Molecular biology of the cell Schiavon, C. R., Turn, R. E., Newman, L. E., Kahn, R. A. 2019; 30 (10): 1198-1213

  Abstract

  Mitochondria are essential and dynamic organelles undergoing constant fission and fusion. The primary players in mitochondrial morphology (MFN1/2, OPA1, DRP1) have been identified, but their mechanism(s) of regulation are still being elucidated. ARL2 is a regulatory GTPase that has previously been shown to play a role in the regulation of mitochondrial morphology. Here we demonstrate that ELMOD2, an ARL2 GTPase-activating protein (GAP), is necessary for ARL2 to promote mitochondrial elongation. We show that loss of ELMOD2 causes mitochondrial fragmentation and a lower rate of mitochondrial fusion, while ELMOD2 overexpression promotes mitochondrial tubulation and increases the rate of fusion in a mitofusin-dependent manner. We also show that a mutant of ELMOD2 lacking GAP activity is capable of promoting fusion, suggesting that ELMOD2 does not need GAP activity to influence mitochondrial morphology. Finally, we show that ELMOD2, ARL2, Mitofusins 1 and 2, Miros 1 and 2, and mitochondrial phospholipase D (mitoPLD) all localize to discrete, regularly spaced puncta along mitochondria. These results suggest that ELMOD2 is functioning as an effector downstream of ARL2 and upstream of the mitofusins to promote mitochondrial fusion. Our data provide insights into the pathway by which mitochondrial fusion is regulated in the cell.

  View details for DOI 10.1091/mbc.E18-12-0804

  View details for PubMedID 30865555

  View details for PubMedCentralID PMC6724520

• Meeting report-Small GTPases in membrane processes: FASEB summer research conference. Traffic (Copenhagen, Denmark) Turn, R. E., D'Souza, R. S., Wall, A. A. 2019; 20 (3): 259-262

  Abstract

  In September 2018, conference organizers Nava Segev (University of Illinois, Chicago) and Marino Zerial (MPI, Dresden) hosted the 5th FASEB Meeting in Small GTPases in Membrane Processes: Trafficking, Autophagy and Disease at the National Conference Center in Leesburg, Virginia. With over 100 attendees from across the globe sharing their varied expertise and interests, we came together with the common goal of gaining a better understanding of how small GTPases and their regulators act in both canonical and non-canonical pathways to conduct a diversity of essential cellular functions. A broad range of disciplines was covered in this meeting, including the study of biophysical and structural properties of these proteins, functional studies to get at the roles of these proteins in various cellular contexts (eg, ciliary function, mitophagy, cell motility, cell cycle, and development), and translational approaches to understand the greater implications of small GTPases and their regulators in multicellular systems and disease pathology. This meeting provided attendees with the opportunity to discuss pressing questions that are driving the study of small GTPases and to explore directions for the future. Of particular note, both formal talks and informal discussions very clearly highlighted the clinical importance of these proteins and pathways, the ways in which cutting edge imaging technologies are expanding our understanding of them, and the need to work better in groups to tackle the larger questions of how GTPases contribute to cellular homeostasis or dysfunction. In this meeting report, we focus upon these three themes, as they have the potential to help shape our future studies of both the biology of small GTPases and their roles in a wide array of fundamental cellular functions.

  View details for DOI 10.1111/tra.12633

  View details for PubMedID 30666771

• The ARL2 GTPase regulates mitochondrial fusion from the intermembrane space. Cellular logistics Newman, L. E., Schiavon, C. R., Turn, R. E., Kahn, R. A. 2017; 7 (3): e1340104

  Abstract

  Mitochondria are essential, dynamic organelles that regularly undergo both fusion and fission in response to cellular conditions, though mechanisms of the regulation of their dynamics are incompletely understood. We provide evidence that increased activity of the small GTPase ARL2 is strongly correlated with an increase in fusion, while loss of ARL2 activity results in a decreased rate of mitochondrial fusion. Strikingly, expression of activated ARL2 can partially restore the loss of fusion resulting from deletion of either mitofusin 1 (MFN1) or mitofusin 2 (MFN2), but not deletion of both. We only observe the full effects of ARL2 on mitochondrial fusion when it is present in the intermembrane space (IMS), as constructs driven to the matrix or prevented from entering mitochondria are essentially inactive in promoting fusion. Thus, ARL2 is the first regulatory (small) GTPase shown to act inside mitochondria or in the fusion pathway. Finally, using high-resolution, structured illumination microscopy (SIM), we find that ARL2 and mitofusin immunoreactivities present as punctate staining along mitochondria that share a spatial convergence in fluorescence signals. Thus, we propose that ARL2 plays a regulatory role in mitochondrial fusion, acting from the IMS and requiring at least one of the mitofusins in their canonical role in fusion of the outer membranes.

  View details for DOI 10.1080/21592799.2017.1340104

  View details for PubMedID 28944094

  View details for PubMedCentralID PMC5602422

• Higher order signaling: ARL2 as regulator of both mitochondrial fusion and microtubule dynamics allows integration of 2 essential cell functions. Small GTPases Francis, J. W., Turn, R. E., Newman, L. E., Schiavon, C., Kahn, R. A. 2016; 7 (4): 188-196

  Abstract

  ARL2 is among the most highly conserved proteins, predicted to be present in the last eukaryotic common ancestor, and ubiquitously expressed. Genetic screens in multiple model organisms identified ARL2, and its cytosolic binding partner cofactor D (TBCD), as important in tubulin folding and microtubule dynamics. Both ARL2 and TBCD also localize to centrosomes, making it difficult to dissect these effects. A growing body of evidence also has found roles for ARL2 inside mitochondria, as a regulator of mitochondrial fusion. Other studies have revealed roles for ARL2, in concert with its closest paralog ARL3, in the traffic of farnesylated cargos between membranes and specifically to cilia and photoreceptor cells. Details of each of these signaling processes continue to emerge. We summarize those data here and speculate about the potential for cross-talk or coordination of cell regulation, termed higher order signaling, based upon the use of a common GTPase in disparate cell functions.

  View details for DOI 10.1080/21541248.2016.1211069

  View details for PubMedID 27400436

  View details for PubMedCentralID PMC5129891

• Autocrine selection of a GLP-1R G-protein biased agonist with potent antidiabetic effects. Nature communications Zhang, H., Sturchler, E., Zhu, J., Nieto, A., Cistrone, P. A., Xie, J., He, L., Yea, K., Jones, T., Turn, R., Di Stefano, P. S., Griffin, P. R., Dawson, P. E., McDonald, P. H., Lerner, R. A. 2015; 6: 8918

  Abstract

  Glucagon-like peptide-1 (GLP-1) receptor (GLP-1R) agonists have emerged as treatment options for type 2 diabetes mellitus (T2DM). GLP-1R signals through G-protein-dependent, and G-protein-independent pathways by engaging the scaffold protein β-arrestin; preferential signalling of ligands through one or the other of these branches is known as 'ligand bias'. Here we report the discovery of the potent and selective GLP-1R G-protein-biased agonist, P5. We identified P5 in a high-throughput autocrine-based screening of large combinatorial peptide libraries, and show that P5 promotes G-protein signalling comparable to GLP-1 and Exendin-4, but exhibited a significantly reduced β-arrestin response. Preclinical studies using different mouse models of T2DM demonstrate that P5 is a weak insulin secretagogue. Nevertheless, chronic treatment of diabetic mice with P5 increased adipogenesis, reduced adipose tissue inflammation as well as hepatic steatosis and was more effective at correcting hyperglycaemia and lowering haemoglobin A1c levels than Exendin-4, suggesting that GLP-1R G-protein-biased agonists may provide a novel therapeutic approach to T2DM.

  View details for DOI 10.1038/ncomms9918

  View details for PubMedID 26621478

  View details for PubMedCentralID PMC4686834