Honors & Awards

  • K99/R00 Pathway to Independence Award, National Institutes of Health (2021)
  • Merck Fellow, Damon Runyon Cancer Research Foundation (2017)
  • Harry & Samuel Mann Outstanding Graduate Student Award, Cornell University (2015)

Professional Education

  • Doctor of Philosophy, Cornell University (2016)
  • Bachelor of Science, Peking University (2016)

Stanford Advisors


  • Shaogeng Tang, Peter S. Kim. "United States Patent 16/861,058 Methods related to a structure of high-affinity human PD-1/PD-L2 complex", Leland Stanford Junior University, Chan Zuckerberg Biohub Inc, Mar 25, 2021

All Publications

  • Human sperm TMEM95 binds eggs and facilitates membrane fusion. Proceedings of the National Academy of Sciences of the United States of America Tang, S., Lu, Y., Skinner, W. M., Sanyal, M., Lishko, P. V., Ikawa, M., Kim, P. S. 2022; 119 (40): e2207805119


    Tmem95 encodes a sperm acrosomal membrane protein, whose knockout has a male-specific sterility phenotype in mice. Tmem95 knockout murine sperm can bind to, but do not fuse with, eggs. How TMEM95 plays a role in membrane fusion of sperm and eggs has remained elusive. Here, we utilize a sperm penetration assay as a model system to investigate the function of human TMEM95. We show that human TMEM95 binds to hamster egg membranes, providing evidence for a TMEM95 receptor on eggs. Using X-ray crystallography, we reveal an evolutionarily conserved, positively charged region of TMEM95 as a putative receptor-binding surface. Amino acid substitutions within this region of TMEM95 ablate egg-binding activity. We identify monoclonal antibodies against TMEM95 that reduce the number of human sperm fused with hamster eggs in sperm penetration assays. Strikingly, these antibodies do not block binding of sperm to eggs. Taken together, these results provide strong evidence for a specific, receptor-mediated interaction of sperm TMEM95 with eggs and suggest that this interaction may have a role in facilitating membrane fusion during fertilization.

    View details for DOI 10.1073/pnas.2207805119

    View details for PubMedID 36161911

  • A high-affinity human PD-1/PD-L2 complex informs avenues for small-molecule immune checkpoint drug discovery. Proceedings of the National Academy of Sciences of the United States of America Tang, S. n., Kim, P. S. 2019


    Immune checkpoint blockade of programmed death-1 (PD-1) by monoclonal antibody drugs has delivered breakthroughs in the treatment of cancer. Nonetheless, small-molecule PD-1 inhibitors could lead to increases in treatment efficacy, safety, and global access. While the ligand-binding surface of apo-PD-1 is relatively flat, it harbors a striking pocket in the murine PD-1/PD-L2 structure. An analogous pocket in human PD-1 may serve as a small-molecule drug target, but the structure of the human complex is unknown. Because the CC' and FG loops in murine PD-1 adopt new conformations upon binding PD-L2, we hypothesized that mutations in these two loops could be coupled to pocket formation and alter PD-1's affinity for PD-L2. Here, we conducted deep mutational scanning in these loops and used yeast surface display to select for enhanced PD-L2 binding. A PD-1 variant with three substitutions binds PD-L2 with an affinity two orders of magnitude higher than that of the wild-type protein, permitting crystallization of the complex. We determined the X-ray crystal structures of the human triple-mutant PD-1/PD-L2 complex and the apo triple-mutant PD-1 variant at 2.0 Å and 1.2 Å resolution, respectively. Binding of PD-L2 is accompanied by formation of a prominent pocket in human PD-1, as well as substantial conformational changes in the CC' and FG loops. The structure of the apo triple-mutant PD-1 shows that the CC' loop adopts the ligand-bound conformation, providing support for allostery between the loop and pocket. This human PD-1/PD-L2 structure provide critical insights for the design and discovery of small-molecule PD-1 inhibitors.

    View details for DOI 10.1073/pnas.1916916116

    View details for PubMedID 31727844

  • ESCRT-III activation by parallel action of ESCRT-I/II and ESCRT-0/Bro1 during MVB biogenesis ELIFE Tang, S., Buchkovich, N. J., Henne, W. M., Banjade, S., Kim, Y. J., Emr, S. D. 2016; 5


    The endosomal sorting complexes required for transport (ESCRT) pathway facilitates multiple fundamental membrane remodeling events. Previously, we determined X-ray crystal structures of ESCRT-III subunit Snf7, the yeast CHMP4 ortholog, in its active and polymeric state (Tang et al., 2015). However, how ESCRT-III activation is coordinated by the upstream ESCRT components at endosomes remains unclear. Here, we provide a molecular explanation for the functional divergence of structurally similar ESCRT-III subunits. We characterize novel mutations in ESCRT-III Snf7 that trigger activation, and identify a novel role of Bro1, the yeast ALIX ortholog, in Snf7 assembly. We show that upstream ESCRTs regulate Snf7 activation at both its N-terminal core domain and the C-terminus α6 helix through two parallel ubiquitin-dependent pathways: the ESCRT-I-ESCRT-II-Vps20 pathway and the ESCRT-0-Bro1 pathway. We therefore provide an enhanced understanding for the activation of the spatially unique ESCRT-III-mediated membrane remodeling.

    View details for DOI 10.7554/eLife.15507

    View details for Web of Science ID 000376391800001

    View details for PubMedID 27074665

    View details for PubMedCentralID PMC4865371

  • Structural basis for activation, assembly and membrane binding of ESCRT-III Snf7 filaments ELIFE Tang, S., Henne, W. M., Borbat, P. P., Buchkovich, N. J., Freed, J. H., Mao, Y., Fromme, J. C., Emr, S. D. 2015; 4


    The endosomal sorting complexes required for transport (ESCRTs) constitute hetero-oligomeric machines that catalyze multiple topologically similar membrane-remodeling processes. Although ESCRT-III subunits polymerize into spirals, how individual ESCRT-III subunits are activated and assembled together into a membrane-deforming filament remains unknown. Here, we determine X-ray crystal structures of the most abundant ESCRT-III subunit Snf7 in its active conformation. Using pulsed dipolar electron spin resonance spectroscopy (PDS), we show that Snf7 activation requires a prominent conformational rearrangement to expose protein-membrane and protein-protein interfaces. This promotes the assembly of Snf7 arrays with ~30 Å periodicity into a membrane-sculpting filament. Using a combination of biochemical and genetic approaches, both in vitro and in vivo, we demonstrate that mutations on these protein interfaces halt Snf7 assembly and block ESCRT function. The architecture of the activated and membrane-bound Snf7 polymer provides crucial insights into the spatially unique ESCRT-III-mediated membrane remodeling.

    View details for DOI 10.7554/eLife.12548

    View details for Web of Science ID 000374007500001

    View details for PubMedID 26670543

    View details for PubMedCentralID PMC4720517

  • A structural blueprint for interleukin-21 signal modulation. Cell reports Abhiraman, G. C., Bruun, T. U., Caveney, N. A., Su, L. L., Saxton, R. A., Yin, Q., Tang, S., Davis, M. M., Jude, K. M., Garcia, K. C. 2023; 42 (6): 112657


    Interleukin-21 (IL-21) plays a critical role in generating immunological memory by promoting the germinal center reaction, yet clinical use of IL-21 remains challenging because of its pleiotropy and association with autoimmune disease. To better understand the structural basis of IL-21 signaling, we determine the structure of the IL-21-IL-21R-γc ternary signaling complex by X-ray crystallography and a structure of a dimer of trimeric complexes using cryo-electron microscopy. Guided by the structure, we design analogs of IL-21 by introducing substitutions to the IL-21-γc interface. These IL-21 analogs act as partial agonists that modulate downstream activation of pS6, pSTAT3, and pSTAT1. These analogs exhibit differential activity on T and B cell subsets and modulate antibody production in human tonsil organoids. These results clarify the structural basis of IL-21 signaling and offer a potential strategy for tunable manipulation of humoral immunity.

    View details for DOI 10.1016/j.celrep.2023.112657

    View details for PubMedID 37339051

  • Mitochondrial uncouplers impair human sperm motility without altering ATP content. Biology of reproduction Skinner, W. M., Petersen, N. T., Unger, B., Tang, S., Tabarsi, E., Lamm, J., Jalalian, L., Smith, J., Bertholet, A. M., Xu, K., Kirichok, Y., Lishko, P. V. 2023


    In human spermatozoa, the electrochemical potentials across the mitochondrial and plasma membranes are related to sperm functionality and fertility, but the exact role of each potential has yet to be clarified. Impairing sperm mitochondrial function has been considered as an approach to creating male or unisex contraceptives, but it has yet to be shown whether this approach would ultimately block the ability of sperm to reach or fertilize an egg. To investigate whether the mitochondrial and plasma membrane potentials are necessary for sperm fertility, human sperm were treated with two small-molecule mitochondrial uncouplers (Niclosamide Ethanolamine and BAM15) that depolarize membranes by inducing passive proton flow, and evaluated the effects on a variety of sperm physiological processes. BAM15 specifically uncoupled human sperm mitochondria while Niclosamide Ethanolamine induced proton current in the plasma membrane in addition to depolarizing the mitochondria. Additionally, both compounds significantly decreased sperm progressive motility with Niclosamide Ethanolamine having a more robust effect. However, these uncouplers did not reduce sperm ATP content or impair other physiological processes, suggesting that human sperm can rely on glycolysis for ATP production if mitochondria are impaired. Thus, systemically delivered contraceptives that target sperm mitochondria to reduce their ATP production would likely need to be paired with sperm-specific glycolysis inhibitors. However, since Niclosamide Ethanolamine impairs sperm motility through an ATP-independent mechanism, and Niclosamide is FDA-approved and not absorbed through mucosal membranes, it could be a useful ingredient in on-demand, vaginally-applied contraceptives.

    View details for DOI 10.1093/biolre/ioad064

    View details for PubMedID 37294625

  • Efficient evolution of human antibodies from general protein language models. Nature biotechnology Hie, B. L., Shanker, V. R., Xu, D., Bruun, T. U., Weidenbacher, P. A., Tang, S., Wu, W., Pak, J. E., Kim, P. S. 2023


    Natural evolution must explore a vast landscape of possible sequences for desirable yet rare mutations, suggesting that learning from natural evolutionary strategies could guide artificial evolution. Here we report that general protein language models can efficiently evolve human antibodies by suggesting mutations that are evolutionarily plausible, despite providing the model with no information about the target antigen, binding specificity or protein structure. We performed language-model-guided affinity maturation of seven antibodies, screening 20 or fewer variants of each antibody across only two rounds of laboratory evolution, and improved the binding affinities of four clinically relevant, highly mature antibodies up to sevenfold and three unmatured antibodies up to 160-fold, with many designs also demonstrating favorable thermostability and viral neutralization activity against Ebola and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pseudoviruses. The same models that improve antibody binding also guide efficient evolution across diverse protein families and selection pressures, including antibiotic resistance and enzyme activity, suggesting that these results generalize to many settings.

    View details for DOI 10.1038/s41587-023-01763-2

    View details for PubMedID 37095349

    View details for PubMedCentralID 4410700

  • A ferritin-based COVID-19 nanoparticle vaccine that elicits robust, durable, broad-spectrum neutralizing antisera in non-human primates. Nature communications Weidenbacher, P. A., Sanyal, M., Friedland, N., Tang, S., Arunachalam, P. S., Hu, M., Kumru, O. S., Morris, M. K., Fontenot, J., Shirreff, L., Do, J., Cheng, Y. C., Vasudevan, G., Feinberg, M. B., Villinger, F. J., Hanson, C., Joshi, S. B., Volkin, D. B., Pulendran, B., Kim, P. S. 2023; 14 (1): 2149


    While the rapid development of COVID-19 vaccines has been a scientific triumph, the need remains for a globally available vaccine that provides longer-lasting immunity against present and future SARS-CoV-2 variants of concern (VOCs). Here, we describe DCFHP, a ferritin-based, protein-nanoparticle vaccine candidate that, when formulated with aluminum hydroxide as the sole adjuvant (DCFHP-alum), elicits potent and durable neutralizing antisera in non-human primates against known VOCs, including Omicron BQ.1, as well as against SARS-CoV-1. Following a booster ~one year after the initial immunization, DCFHP-alum elicits a robust anamnestic response. To enable global accessibility, we generated a cell line that can enable production of thousands of vaccine doses per liter of cell culture and show that DCFHP-alum maintains potency for at least 14 days at temperatures exceeding standard room temperature. DCFHP-alum has potential as a once-yearly (or less frequent) booster vaccine, and as a primary vaccine for pediatric use including in infants.

    View details for DOI 10.1038/s41467-023-37417-9

    View details for PubMedID 37069151

    View details for PubMedCentralID 9225255

  • Structure-guided stabilization improves the ability of the HIV-1 gp41 hydrophobic pocket to elicit neutralizing antibodies. The Journal of biological chemistry Bruun, T. J., Tang, S., Erwin, G., Deis, L., Fernandez, D., Kim, P. 2023: 103062


    The hydrophobic pocket found in the N-heptad repeat (NHR) region of HIV-1 gp41 is a highly conserved epitope that is the target of various HIV-1 neutralizing monoclonal antibodies. Although the high conservation of the pocket makes it an attractive vaccine candidate, it has been challenging to elicit potent anti-NHR antibodies via immunization. Here, we solved a high-resolution structure of the NHR mimetic IQN17, and, consistent with previous ligand-bound gp41 pocket structures, we observed remarkable conformational plasticity of the pocket. The high malleability of this pocket led us to test whether we could improve the immunogenicity of the gp41 pocket by stabilizing its conformation. We show that the addition of five amino acids at the C-terminus of IQN17, to generate IQN22, introduces a stabilizing salt bridge at the base of the peptide that rigidifies the pocket. Mice immunized with IQN22 elicited higher avidity antibodies against the gp41 pocket and a more potent, albeit still weak, neutralizing response against HIV-1 compared to IQN17. Stabilized epitope-focused immunogens could serve as the basis for future HIV-1 fusion-inhibiting vaccines.

    View details for DOI 10.1016/j.jbc.2023.103062

    View details for PubMedID 36841484

  • 1700029I15Rik orchestrates the biosynthesis of acrosomal membrane proteins required for sperm-egg interaction. Proceedings of the National Academy of Sciences of the United States of America Lu, Y., Shimada, K., Tang, S., Zhang, J., Ogawa, Y., Noda, T., Shibuya, H., Ikawa, M. 2023; 120 (8): e2207263120


    Sperm acrosomal membrane proteins, such as Izumo sperm-egg fusion 1 (IZUMO1) and sperm acrosome-associated 6 (SPACA6), play essential roles in mammalian gamete binding or fusion. How their biosynthesis is regulated during spermiogenesis has largely remained elusive. Here, we show that 1700029I15Rik knockout male mice are severely subfertile and their spermatozoa do not fuse with eggs. 1700029I15Rik is a type-II transmembrane protein expressed in early round spermatids but not in mature spermatozoa. It interacts with proteins involved in N-linked glycosylation, disulfide isomerization, and endoplasmic reticulum (ER)-Golgi trafficking, suggesting a potential role in nascent protein processing. The ablation of 1700029I15Rik destabilizes non-catalytic subunits of the oligosaccharyltransferase (OST) complex that are pivotal for N-glycosylation. The knockout testes exhibit normal expression of sperm plasma membrane proteins, but decreased abundance of multiple acrosomal membrane proteins involved in fertilization. The knockout sperm show upregulated chaperones related to ER-associated degradation (ERAD) and elevated protein ubiquitination; strikingly, SPACA6 becomes undetectable. Our results support for a specific, 1700029I15Rik-mediated pathway underpinning the biosynthesis of acrosomal membrane proteins during spermiogenesis.

    View details for DOI 10.1073/pnas.2207263120

    View details for PubMedID 36787362

  • A ferritin-based COVID-19 nanoparticle vaccine that elicits robust, durable, broad-spectrum neutralizing antisera in non-human primates. bioRxiv : the preprint server for biology Weidenbacher, P. A., Sanyal, M., Friedland, N., Tang, S., Arunachalam, P. S., Hu, M., Kumru, O. S., Morris, M. K., Fontenot, J., Shirreff, L., Do, J., Cheng, Y. C., Vasudevan, G., Feinberg, M. B., Villinger, F. J., Hanson, C., Joshi, S. B., Volkin, D. B., Pulendran, B., Kim, P. S. 2022


    While the rapid development of COVID-19 vaccines has been a scientific triumph, the need remains for a globally available vaccine that provides longer-lasting immunity against present and future SARS-CoV-2 variants of concern (VOCs). Here, we describe DCFHP, a ferritin-based, protein-nanoparticle vaccine candidate that, when formulated with aluminum hydroxide as the sole adjuvant (DCFHP-alum), elicits potent and durable neutralizing antisera in non-human primates against known VOCs, including Omicron BQ.1, as well as against SARS-CoV-1. Following a booster ∼one year after the initial immunization, DCFHP-alum elicits a robust anamnestic response. To enable global accessibility, we generated a cell line that can enable production of thousands of vaccine doses per liter of cell culture and show that DCFHP-alum maintains potency for at least 14 days at temperatures exceeding standard room temperature. DCFHP-alum has potential as a once-yearly booster vaccine, and as a primary vaccine for pediatric use including in infants.

    View details for DOI 10.1101/2022.12.25.521784

    View details for PubMedID 36597527

    View details for PubMedCentralID PMC9810210

  • Designing epitope-focused vaccines via antigen reorientation. bioRxiv : the preprint server for biology Xu, D., Li, C., Utz, A., Weidenbacher, P. A., Tang, S., Sanyal, M., Pulendran, B., Kim, P. S. 2022


    A major challenge in vaccine development, especially against rapidly evolving viruses, is the ability to focus the immune response toward evolutionarily conserved antigenic regions to confer broad protection. For example, while many broadly neutralizing antibodies against influenza have been found to target the highly conserved stem region of hemagglutinin (HA-stem), the immune response to seasonal influenza vaccines is predominantly directed to the immunodominant but variable head region (HA-head), leading to narrow-spectrum efficacy. Here, we first introduce an approach to controlling antigen orientation based on the site-specific insertion of short stretches of aspartate residues (oligoD) that facilitates antigen-binding to alum adjuvants. We demonstrate the generalizability of this approach to antigens from the Ebola virus, SARS-CoV-2, and influenza and observe enhanced antibody responses following immunization in all cases. Next, we use this approach to reorient HA in an "upside down" configuration, which we envision increases HA-stem exposure, therefore also improving its immunogenicity compared to HA-head. When applied to HA of H2N2 A/Japan/305/1957, the reoriented H2 HA (reoH2HA) on alum induced a stem-directed antibody response that cross-reacted with both group 1 and 2 influenza A HAs. Our results demonstrate the possibility and benefits of antigen reorientation via oligoD insertion, which represents a generalizable immunofocusing approach readily applicable for designing epitope-focused vaccine candidates.GRAPHICAL ABSTRACT: Seasonal influenza vaccines induce a biased antibody response against the variable head of hemagglutinin, whereas conserved epitopes on the stem are a target for universal vaccines. Here we show that reorienting HA in an "upside-down" configuration sterically occludes the head and redirects the antibody response to the more exposed stem, thereby inducing broad cross-reactivity against hemagglutinins from diverse influenza strains.

    View details for DOI 10.1101/2022.12.20.521291

    View details for PubMedID 36597536

  • Simplified Purification of Glycoprotein-Modified Ferritin Nanoparticles for Vaccine Development. Biochemistry Weidenbacher, P., Musunuri, S., Powell, A. E., Tang, S., Do, J., Sanyal, M., Kim, P. S. 2022


    Ferritin-based, self-assembling protein nanoparticle vaccines are being developed against a range of viral pathogens, including SARS-CoV-2, influenza, HIV-1, and Epstein-Barr virus. However, purification of these nanoparticles is often laborious and requires customization for each potential nanoparticle vaccine. We propose that the simple insertion of a polyhistidine tag into exposed flexible loops on the ferritin surface (His-Fer) can mitigate the need for complex purifications and enable facile metal-chelate-based purification, thereby allowing for optimization of early stage vaccine candidates. Using sequence homology and computational modeling, we identify four sites that can accommodate insertion of a polyhistidine tag and demonstrate purification of both hemagglutinin-modified and SARS-CoV-2 spike-modified ferritins, highlighting the generality of the approach. A site at the 4-fold axis of symmetry enables optimal purification of both protein nanoparticles. We demonstrate improved purification through modulating the polyhistidine length and optimizing both the metal cation and the resin type. Finally, we show that purified His-Fer proteins remain multimeric and elicit robust immune responses similar to those of their wild-type counterparts. Collectively, this work provides a simplified purification scheme for ferritin-based vaccines.

    View details for DOI 10.1021/acs.biochem.2c00241

    View details for PubMedID 35960597

  • Design principles of the ESCRT-III Vps24-Vps2 module. eLife Banjade, S., Shah, Y. H., Tang, S., Emr, S. D. 2021; 10


    ESCRT-III polymerization is required for all endosomal sorting complex required for transport (ESCRT)-dependent events in the cell. However, the relative contributions of the eight ESCRT-III subunits differ between each process. The minimal features of ESCRT-III proteins necessary for function and the role for the multiple ESCRT-III subunits remain unclear. To identify essential features of ESCRT-III subunits, we previously studied the polymerization mechanisms of two ESCRT-III subunits Snf7 and Vps24, identifying the association of the helix-4 region of Snf7 with the helix-1 region of Vps24 (Banjade et al., 2019a). Here, we find that mutations in the helix-1 region of another ESCRT-III subunit Vps2 can functionally replace Vps24 in Saccharomyces cerevisiae. Engineering and genetic selections revealed the required features of both subunits. Our data allow us to propose three minimal features required for ESCRT-III function - spiral formation, lateral association of the spirals through heteropolymerization, and binding to the AAA + ATPase Vps4 for dynamic remodeling.

    View details for DOI 10.7554/eLife.67709

    View details for PubMedID 34028356

  • A Single Immunization with Spike-Functionalized Ferritin Vaccines Elicits Neutralizing Antibody Responses against SARS-CoV-2 in Mice. ACS central science Powell, A. E., Zhang, K., Sanyal, M., Tang, S., Weidenbacher, P. A., Li, S., Pham, T. D., Pak, J. E., Chiu, W., Kim, P. S. 2021; 7 (1): 183–99


    The development of a safe and effective SARS-CoV-2 vaccine is a public health priority. We designed subunit vaccine candidates using self-assembling ferritin nanoparticles displaying one of two multimerized SARS-CoV-2 spikes: full-length ectodomain (S-Fer) or a C-terminal 70 amino-acid deletion (SDeltaC-Fer). Ferritin is an attractive nanoparticle platform for production of vaccines, and ferritin-based vaccines have been investigated in humans in two separate clinical trials. We confirmed proper folding and antigenicity of spike on the surface of ferritin by cryo-EM and binding to conformation-specific monoclonal antibodies. After a single immunization of mice with either of the two spike ferritin particles, a lentiviral SARS-CoV-2 pseudovirus assay revealed mean neutralizing antibody titers at least 2-fold greater than those in convalescent plasma from COVID-19 patients. Additionally, a single dose of SDeltaC-Fer elicited significantly higher neutralizing responses as compared to immunization with the spike receptor binding domain (RBD) monomer or spike ectodomain trimer alone. After a second dose, mice immunized with SDeltaC-Fer exhibited higher neutralizing titers than all other groups. Taken together, these results demonstrate that multivalent presentation of SARS-CoV-2 spike on ferritin can notably enhance elicitation of neutralizing antibodies, thus constituting a viable strategy for single-dose vaccination against COVID-19.

    View details for DOI 10.1021/acscentsci.0c01405

    View details for PubMedID 33527087

  • Genetic and Biochemical Analyses of Yeast ESCRT. Methods in molecular biology (Clifton, N.J.) Banjade, S. n., Tang, S. n., Emr, S. D. 2019; 1998: 105–16


    Budding yeast Saccharomyces cerevisiae is an ideal model organism to study membrane trafficking pathways. The ESCRT (endosomal sorting complexes required for transport) pathway was first identified in this organism. Upon recognition of endocytosed ubiquitinated membrane proteins at endosomes, ESCRTs assemble at these organelles to catalyze the biogenesis of multivesicular bodies (MVBs). Formation of MVBs leads to the trafficking of these membrane proteins to vacuoles for degradation. Here, we describe genetic and biochemical approaches to study ESCRT function. We outline in vivo endocytosis assays using two model cargoes in Saccharomyces cerevisiae and also describe an in vitro approach to analyze ESCRT-III polymerization on lipid monolayers.

    View details for DOI 10.1007/978-1-4939-9492-2_8

    View details for PubMedID 31250297

  • Electrostatic lateral interactions drive ESCRT-III heteropolymer assembly. eLife Banjade, S. n., Tang, S. n., Shah, Y. H., Emr, S. D. 2019; 8


    Self-assembly of ESCRT-III complex is a critical step in all ESCRT-dependent events. ESCRT-III hetero-polymers adopt variable architectures, but the mechanisms of inter-subunit recognition in these hetero-polymers to create flexible architectures remain unclear. We demonstrate in vivo and in vitro that the Saccharomyces cerevisiae ESCRT-III subunit Snf7 uses a conserved acidic helix to recruit its partner Vps24. Charge-inversion mutations in this helix inhibit Snf7-Vps24 lateral interactions in the polymer, while rebalancing the charges rescues the functional defects. These data suggest that Snf7-Vps24 assembly occurs through electrostatic interactions on one surface, rather than through residue-to-residue specificity. We propose a model in which these cooperative electrostatic interactions in the polymer propagate to allow for specific inter-subunit recognition, while sliding of laterally interacting polymers enable changes in architecture at distinct stages of vesicle biogenesis. Our data suggest a mechanism by which interaction specificity and polymer flexibility can be coupled in membrane-remodeling heteropolymeric assemblies.

    View details for DOI 10.7554/eLife.46207

    View details for PubMedID 31246173

  • Cap-dependent translational control of oncolytic measles virus infection in malignant mesothelioma. Oncotarget Jacobson, B. A., Sadiq, A. A., Tang, S., Jay-Dixon, J., Patel, M. R., Drees, J., Sorenson, B. S., Russell, S. J., Kratzke, R. A. 2017; 8 (38): 63096-63109


    Malignant mesothelioma has a poor prognosis for which there remains an urgent need for successful treatment approaches. Infection with the Edmonston vaccine strain (MV-Edm) derivative of measles virus results in lysis of cancer cells and has been tested in clinical trials for numerous tumor types including mesothelioma. Many factors play a role in MV-Edm tumor cell selectivity and cytopathic activity while also sparing non-cancerous cells. The MV-Edm receptor CD46 (cluster of differentiation 46) was demonstrated to be significantly higher in mesothelioma cells than in control cells. In contrast, mesothelioma cells are not reliant upon the alternative MV-Edm receptor nectin-4 for entry. MV-Edm treatment of mesothelioma reduced cell viability and also invoked apoptotic cell death. Forced expression of eIF4E or translation stimulation following IGF-I (insulin-like growth factor 1) exposure strengthened the potency of measles virus oncolytic activity. It was also shown that repression of cap-dependent translation by treatment with agents [4EASO, 4EGI-1] that suppress host cell translation or by forcing cells to produce an activated repressor protein diminishes the strength of oncolytic viral efficacy.

    View details for DOI 10.18632/oncotarget.18656

    View details for PubMedID 28968974

    View details for PubMedCentralID PMC5609906

  • Vesicular stomatitis virus expressing interferon-beta is oncolytic and promotes antitumor immune responses in a syngeneic murine model of non-small cell lung cancer ONCOTARGET Patel, M. R., Jacobson, B. A., Ji, Y., Drees, J., Tang, S., Xiong, K., Wang, H., Prigge, J. E., Dash, A. S., Kratzke, A., Mesev, E., Etchison, R., Federspiel, M. J., Russell, S. J., Kratzke, R. A. 2015; 6 (32): 33165-33177


    Vesicular stomatitis virus (VSV) is a potent oncolytic virus for many tumors. VSV that produces interferon-β (VSV-IFNβ) is now in early clinical testing for solid tumors. Here, the preclinical activity of VSV and VSV-IFNβ against non-small cell lung cancer (NSCLC) is reported. NSCLC cell lines were treated in vitro with VSV expressing green fluorescence protein (VSV-GFP) and VSV-IFNβ. VSV-GFP and VSV-IFNβ were active against NSCLC cells. JAK/STAT inhibition with ruxolitinib re-sensitized resistant H838 cells to VSV-IFNβ mediated oncolysis. Intratumoral injections of VSV-GFP and VSV-IFNβ reduced tumor growth and weight in H2009 nude mouse xenografts (p < 0.01). A similar trend was observed in A549 xenografts. Syngeneic LM2 lung tumors grown in flanks of A/J mice were injected with VSV-IFNβ intratumorally. Treatment of LM2 tumors with VSV-IFNβ resulted in tumor regression, prolonged survival (p < 0.0001), and cure of 30% of mice. Intratumoral injection of VSV-IFNβ resulted in decreased tumor-infiltrating regulatory T cells (Treg) and increased CD8+ T cells. Tumor cell expression of PDL-1 was increased after VSV-IFNβ treatment. VSV-IFNβ has potent antitumor effects and promotes systemic antitumor immunity. These data support further clinical investigation of VSV-IFNβ for NSCLC.

    View details for DOI 10.18632/oncotarget.5320

    View details for Web of Science ID 000363186600080

    View details for PubMedID 26431376

  • Triptolide and its prodrug minnelide suppress Hsp70 and inhibit in vivo growth in a xenograft model of mesothelioma. Genes & cancer Jacobson, B. A., Chen, E. Z., Tang, S., Belgum, H. S., McCauley, J. A., Evenson, K. A., Etchison, R. G., Jay-Dixon, J., Patel, M. R., Raza, A., Saluja, A. K., D'Cunha, J., Kratzke, R. A. 2015; 6 (3-4): 144-152


    Malignant mesothelioma is a devastating disease with a poor prognosis for which there is a clear need for more successful therapeutic approaches. Triptolide, a diterpenoid triepoxide, is a highly effective agent against several cancer types in animal models. Owing to triptolide's poor solubility in water, a water-soluble analog, minnelide, was synthesized. Minnelide is a prodrug of triptolide and is activated by exposure to phosphatases that are found in all body tissues, including blood. Mesothelioma cells were treated in vitro with minnelide or its parent compound, triptolide. Minnelide and triptolide were both found to significantly reduce mesothelioma cell viability and induce apoptosis. The level of Hsp70, a protein that promotes cancer cell survival, was measured in mesothelioma cells before and after treatment with triptolide. Hsp70 levels were decreased in a dose-dependent manner. In addition, triptolide sensitized cells to gemcitabine and pemetrexed as measured by cell viability. Mice bearing mesothelioma flank tumors were treated with daily injections (28 d) of minnelide or saline solution and xenograft tumor growth recorded. Mice displayed significantly reduced tumor burden. These findings support the clinical evaluation of minnelide therapy for mesothelioma.

    View details for PubMedID 26000097

  • Efficient assembly of oligomannosides using the hydrophobically assisted switching phase method ORGANIC & BIOMOLECULAR CHEMISTRY Meng, S., Tian, T., Han, D., Wang, L., Tang, S., Meng, X., Li, Z. 2015; 13 (24): 6711-6722


    The hydrophobically assisted switching phase (HASP) method was applied in the assembly of oligomannosides. A new mannosyl donor with high reactivity was selected after a series of optimization studies, which was suitable for the synthesis of oligomannosides via the HASP method. The practicability of the HASP method towards the synthesis of branched oligosaccharides was explored and two branched penta-mannosides were assembled efficiently.

    View details for DOI 10.1039/c5ob00730e

    View details for Web of Science ID 000355985800007

    View details for PubMedID 25967589

  • Essential N-Terminal Insertion Motif Anchors the ESCRT-III Filament during MVB Vesicle Formation DEVELOPMENTAL CELL Buchkovich, N. J., Henne, W. M., Tang, S., Emr, S. D. 2013; 27 (2): 201-214


    The endosomal sorting complexes required for transport (ESCRTs) have emerged as key cellular machinery that drive topologically unique membrane deformation and scission. Understanding how the ESCRT-III polymer interacts with membrane, promoting and/or stabilizing membrane deformation, is an important step in elucidating this sculpting mechanism. Using a combination of genetic and biochemical approaches, both in vivo and in vitro, we identify two essential modules required for ESCRT-III-membrane association: an electrostatic cluster and an N-terminal insertion motif. Mutating either module in yeast causes cargo sorting defects in the MVB pathway. We show that the essential N-terminal insertion motif provides a stable anchor for the ESCRT-III polymer. By replacing this N-terminal motif with well-characterized membrane insertion modules, we demonstrate that the N terminus of Snf7 has been tuned to maintain the topological constraints associated with ESCRT-III-filament-mediated membrane invagination and vesicle formation. Our results provide insights into the spatially unique, ESCRT-III-mediated membrane remodeling.

    View details for DOI 10.1016/j.devcel.2013.09.009

    View details for Web of Science ID 000326913900010

    View details for PubMedID 24139821