Ganes C Sen

Lerner Research Institute, Cleveland, Ohio, United States

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Publications (233)1280.09 Total impact

  • Volker Fensterl · Saurabh Chattopadhyay · Ganes C. Sen ·

    11/2015; 2(1). DOI:10.1146/annurev-virology-100114-055249
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    ABSTRACT: Mammalian Toll-like receptors (TLR) recognize microbial products and elicit transient immune responses that protect the infected host from disease. TLR4-which signals from both plasma and endosomal membranes-is activated by bacterial lipopolysaccharides (LPS) and induces many cytokine genes, the prolonged expression of which causes septic shock in mice. We report here that the expression of some TLR4-induced genes in myeloid cells requires the protein kinase activity of the epidermal growth factor receptor (EGFR). EGFR inhibition affects TLR4-induced responses differently depending on the target gene. The induction of interferon-β (IFN-β) and IFN-inducible genes is strongly inhibited, whereas TNF-α induction is enhanced. Inhibition is specific to the IFN-regulatory factor (IRF)-driven genes because EGFR is required for IRF activation downstream of TLR-as is IRF co-activator β-catenin-through the PI3 kinase/AKT pathway. Administration of an EGFR inhibitor to mice protects them from LPS-induced septic shock and death by selectively blocking the IFN branch of TLR4 signaling. These results demonstrate a selective regulation of TLR4 signaling by EGFR and highlight the potential use of EGFR inhibitors to treat septic shock syndrome. © 2015 The Authors.
    EMBO Reports 09/2015; DOI:10.15252/embr.201540337 · 9.06 Impact Factor
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    ABSTRACT: The murine double-stranded RNA-binding protein RAX and the human homolog PACT were originally characterized as activators of protein kinase R (PKR). Mice deficient in RAX show reproductive and developmental defects, including reduced body size, craniofacial defects and anterior pituitary hypoplasia. As these defects are not observed in PKR-deficient mice, the phenotype has been attributed to PKR-independent activities of RAX. Here we further investigated the involvement of PKR in the physiological function of RAX, by generating rax(-/-) mice deficient in PKR, or carrying a kinase-inactive mutant of PKR (K271R) or an unphosphorylatable mutant of the PKR substrate eIF2α (S51A). Ablating PKR expression rescued the developmental and reproductive deficiencies in rax(-/-) mice. Generating rax(-/-) mice with a kinase-inactive mutant of PKR resulted in similar rescue, confirming that the rax(-/-) defects are PKR dependent; specifically that the kinase activity of PKR was required for these defects. Moreover, generating rax(-/-) mice that were heterozygous for an unphosphorylatable mutant eIF2α provides partial rescue of the rax(-/-) defect, consistent with mutation of one copy of the Eif2s1 gene. These observations were further investigated in vitro by reducing RAX expression in anterior pituitary cells, resulting in increased PKR activity and induction of the PKR-regulated cyclin-dependent kinase inhibitor p21(WAF1/CIP1) . These results demonstrate that PKR kinase activity is required for onset of the rax(-/-) phenotype, implying an unexpected function for RAX as a negative regulator of PKR in the context of postnatal anterior pituitary tissue, and identify a critical role for the regulation of PKR activity for normal development. This article is protected by copyright. All rights reserved.
    FEBS Journal 09/2015; DOI:10.1111/febs.13533 · 4.00 Impact Factor
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    ABSTRACT: Innate immunity is the first line of defense against microbial insult. The transcription factor, IRF3, is needed by mammalian cells to mount innate immune responses against many microbes, especially viruses. IRF3 remains inactive in the cytoplasm of uninfected cells; upon virus infection, it gets phosphorylated and then translocates to the nucleus, where it binds to the promoters of antiviral genes and induces their expression. Such genes include type I interferons (IFNs) as well as Interferon Stimulated Genes (ISGs). IRF3-/- cells support enhanced replication of many viruses and therefore, the corresponding mice are highly susceptible to viral pathogenesis. Here, we provide evidence for an unexpected pro-microbial role of IRF3: the replication of the protozoan parasite, Toxoplasma gondii, was significantly impaired in IRF3-/- cells. In exploring whether the transcriptional activity of IRF3 was important for its pro-parasitic function, we found that ISGs induced by parasite-activated IRF3 were indeed essential, whereas type I interferons were not important. To delineate the signaling pathway that activates IRF3 in response to parasite infection, we used genetically modified human and mouse cells. The pro-parasitic signaling pathway, which we termed PISA (Parasite-IRF3 Signaling Activation), activated IRF3 without any involvement of the Toll-like receptor or RIG-I-like receptor pathways, thereby ruling out a role of parasite-derived RNA species in activating PISA. Instead, PISA needed the presence of cGAS, STING, TBK1 and IRF3, indicating the necessity of DNA-triggered signaling. To evaluate the physiological significance of our in vitro findings, IRF3-/- mice were challenged with parasite infection and their morbidity and mortality were measured. Unlike WT mice, the IRF3-/- mice did not support replication of the parasite and were resistant to pathogenesis caused by it. Our results revealed a new paradigm in which the antiviral host factor, IRF3, plays a cell-intrinsic pro-parasitic role.
    PLoS Pathogens 03/2015; 11(3):e1004779. DOI:10.1371/journal.ppat.1004779 · 7.56 Impact Factor
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    ABSTRACT: Epidermal growth factor receptor ( EGFR) overexpression plays an important oncogenic role in cancer. Regular EGFR protein levels are increased in cancer cells and the receptor then becomes constitutively active. However, downstream signals generated by constitutively activated EGFR are unknown. Here we report that the overexpressed EGFR oscillates between two distinct and mutually exclusive modes of signalling. Constitutive or non-canonical EGFR signalling activates the transcription factor IRF3 leading to expression of IFI27, IFIT1 and TRAIL. Ligand-mediated activation of EGFR switches off IRF3-dependent transcription, activates canonical extracellular signal-regulated kinase (ERK) and Akt signals, and confers sensitivity to chemotherapy and virus-induced cell death. Mechanistically, the distinct downstream signals result from a switch of EGFR-associated proteins. EGFR constitutively complexes with IRF3 and TBK1 leading to TBK1 and IRF3 phosphorylation. Addition of epidermal growth factor dissociates TBK1, IRF3 and EGFR leading to a loss of IRF3 activity, Shc- EGFR association and ERK activation. Finally, we provide evidence for non-canonical EGFR signalling in glioblastoma.
    Nature Communications 12/2014; 5. DOI:10.1038/ncomms6811 · 11.47 Impact Factor
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    Volker Fensterl · Ganes C Sen ·
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    ABSTRACT: A major component of the protective antiviral host defense is contributed by the intracellular actions of the proteins encoded by interferon-stimulated genes (ISG); amongst these are the Interferon-induced proteins with tetratricopeptide repeats (IFIT), consisting of four members in human and three in mouse. IFIT proteins do not have any known enzyme activity; instead, they inhibit virus replication by binding and regulating the functions of cellular and viral proteins and RNAs. Although all IFITs are comprised of multiple copies of the degenerate tetratricopeptide repeats, their distinct tertiary structures enable them to bind different partners and affect host-virus interactions differently. The recent use of Ifit knock-out mouse models has revealed novel antiviral functions of these proteins and new insights into the specificities of ISG actions. This article focuses on human and murine IFIT1 and IFIT2 by reviewing their mechanisms of action, their critical roles in protecting mice from viral pathogenesis and viral strategies to evade IFIT action. Copyright © 2014, American Society for Microbiology. All Rights Reserved.
    Journal of Virology 11/2014; 89(5). DOI:10.1128/JVI.02744-14 · 4.44 Impact Factor
  • Saurabh Chattopadhyay · Ganes C. Sen ·
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    ABSTRACT: There is a wealth of knowledge about how different Ser/Thr protein kinases participate in Toll-like receptor (TLR) signaling. In many cases, we know the identities of the Ser/Thr residues of various components of the TLR-signaling pathways that are phosphorylated, the functional consequences of the phosphorylation and the responsible protein kinases. In contrast, the analysis of Tyr-phosphorylation of TLRs and their signaling proteins is currently incomplete, because several existing analyses are not systematic or they do not rely on robust experimental data. Nevertheless, it is clear that many TLRs require, for signaling, ligand-dependent phosphorylation of specific Tyr residues in their cytoplasmic domains; the list includes TLR2, TLR3, TLR4, TLR5, TLR8 and TLR9. In this article, we discuss the current status of knowledge on the effect of Tyr-phosphorylation of TLRs and their signaling proteins on their biochemical and biological functions, the possible identities of the relevant protein tyrosine kinases (PTKs) and the nature of regulations of PTK-mediated activation of TLR signaling pathways.
    Cytokine & Growth Factor Reviews 10/2014; 25(5). DOI:10.1016/j.cytogfr.2014.06.002 · 5.36 Impact Factor
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    Jaime L Wetzel · Volker Fensterl · Ganes C Sen ·
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    ABSTRACT: Unlabelled: The type I/III interferon (IFN) system has major roles in regulating viral pathogenesis, usually ameliorating pathogenesis by impairing virus replication through the antiviral actions of one or more IFN-induced proteins. Ifit2 is one such protein which can be induced by IFN or virus infection, and it is responsible for protecting mice from neuropathogenesis caused by vesicular stomatitis virus. Here, we show that Ifit2 also protects mice from pathogenesis caused by the respirovirus Sendai virus (SeV). Mice lacking Ifit2 (Ifit2(-/-)) suffered severe weight loss and succumbed to intranasal infection with SeV strain 52 at a dose that killed only a few wild-type mice. Viral RNA was detectable only in lungs, and SeV titers were higher in Ifit2(-/-) mice than in wild-type mice. Similar infiltration of immune cells was found in the lungs of both mouse lines, corresponding to similar levels of many induced cytokines and chemokines. In contrast, IFN-β and IFN-λ3 expression were considerably higher in the lungs of Ifit2(-/-) mice. Surprisingly, type I IFN receptor knockout (IFNAR(-/-)) mice were less susceptible to SeV than Ifit2(-/-) mice, although their pulmonary virus titers were similarly high. To test the intriguing possibility that type I IFN action enhances pathogenesis in the context of elevated SeV replication in lungs, we generated Ifit2/IFNAR(-/-) double knockout mice. These mice were less susceptible to SeV than Ifit2(-/-) mice, although viral titers in their lungs were even higher. Our results indicate that high SeV replication in the lungs of infected Ifit2(-/-) mice cooperates with elevated IFN-β induction to cause disease. Importance: The IFN system is an innate defense against virus infections. It is triggered quickly in infected cells, which then secrete IFN. Via their cell surface receptors on surrounding cells, they induce transcription of numerous IFN-stimulated genes (ISG), which in turn protect these cells by inhibiting virus life cycles. Hence, IFNs are commonly considered beneficial during virus infections. Here, we report two key findings. First, lack of a single ISG in mice, Ifit2, resulted in high mortality after SeV infection of the respiratory tract, following higher virus loads and higher IFN production in Ifit2(-/-) lungs. Second, mortality of Ifit2(-/-) mice was reduced when mice also lacked the type I IFN receptor, while SeV loads in lungs still were high. This indicates that type I IFN exacerbates pathogenesis in the SeV model, and that limitation of both viral replication and IFN production is needed for effective prevention of disease.
    Journal of Virology 09/2014; 88(23). DOI:10.1128/JVI.02201-14 · 4.44 Impact Factor
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    Volker Fensterl · Jaime L Wetzel · Ganes C Sen ·
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    ABSTRACT: The interferon system provides the first line of host defense against virus infection. Mouse pathogenesis studies have revealed the importance of specific interferon-induced proteins in providing protection against specific viruses. We have previously reported that one such protein, Ifit2, protects neurons of the central nervous system from intranasal infection by the neurotropic rhabdovirus, vesicular stomatitis virus (VSV). Here, we demonstrate that Ifit2 protects the peripheral nervous system from VSV infection as well. In Ifit2-/- mice, VSV, injected subcutaneously into the footpad, entered the proximal lymph node, where it replicated and infected the nodal nerve endings. The infection spread to the sciatic nerve, the spinal cord, and the brain, causing paralysis. In contrast, in the wild-type mice, although VSV replicated equally well in the lymph node, infection of the sciatic nerve and the rest of the nervous system was impaired, thus preventing paralysis. Ifit2 protected only the nervous system from VSV infection; other tissues were well protected even in Ifit2-/- mice. These results indicate that Ifit2 is the interferon-induced protein that prevents VSV infection of neurons of both the peripheral and the central nervous systems, thus inhibiting the consequent neuropathy, but it is dispensable for protecting the cells of other tissues from VSV infection.
    Journal of Virology 07/2014; 88(18). DOI:10.1128/JVI.01341-14 · 4.44 Impact Factor
  • Ganes C Sen ·

    Journal of Interferon & Cytokine Research 06/2014; 34(6):413-414. DOI:10.1089/jir.2014.0062 · 2.00 Impact Factor
  • Saurabh Chattopadhyay · Ganes C Sen ·
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    ABSTRACT: Double-stranded (ds) RNA has diverse roles in host defense and disease prevention. dsRNA, produced by viral replication, elicits strong antiviral responses in host; similar protective responses can also be triggered by cellular dsRNA produced by necrotic, apoptotic, or otherwise stressed, uninfected cells. dsRNA is recognized in the cell by a large family of dsRNA-binding proteins, among which are the pattern recognition receptors (PRRs), toll-like receptor 3 (TLR3), and retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs). TLR3 signals from the endosomal membrane where it senses extracellular dsRNA that has been endocytosed, whereas RLRs signal from the cytoplasm using a mitochondrial adaptor protein. In this review, we will summarize the signaling pathways used by these 2 PRRs, which lead to the activation of specific transcription factors and the induction of many proinflammatory and antiviral genes. However, it is becoming increasingly clear that all host responses are not mediated by the products of these induced genes; signal-dependent post-translational modifications of existing proteins can also profoundly change cellular properties. We will discuss how Src activation by TLR3 changes cell migration, adhesion, and proliferation rates and how IRF-3 activation by RLR triggers a gene induction-independent pro-apoptotic pathway that provides strong antiviral protection.
    Journal of Interferon & Cytokine Research 06/2014; 34(6):427-436. DOI:10.1089/jir.2014.0034 · 2.00 Impact Factor
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    Saurabh Chattopadhyay · Ganes C Sen ·
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    ABSTRACT: Cellular interferon response to microbial infection is transient. In a recent paper in Immunity, Long et al. (2014) identify protein phosphatase 2A (PP2A) as a deactivator of phospho-interferon regulatory factor 3, the key transcription factor for interferon synthesis, thus providing one basis for the observed transiency.
    Molecular cell 04/2014; 54(2):210-1. DOI:10.1016/j.molcel.2014.04.008 · 14.02 Impact Factor
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    ABSTRACT: Angiotensin-converting enzyme (ACE) regulates normal blood pressure and fluid homeostasis through its action in the renin-angiotensin-system (RAS). Ace-/- mice are smaller in size, have low blood pressure and defective kidney structure and functions. All of these defects are cured by transgenic expression of somatic ACE (sACE) in vascular endothelial cells of Ace-/- mice. sACE is expressed on the surface of vascular endothelial cells and undergoes a natural cleavage secretion process to generate a soluble form in the body fluids. Both the tissue-bound and the soluble forms of ACE are enzymatically active, and generate the vasoactive octapeptide Angiotensin II (Ang II) with equal efficiency. To assess the relative physiological roles of the secreted and the cell-bound forms of ACE, we expressed, in the vascular endothelial cells of Ace-/- mice, the ectodomain of sACE, which corresponded to only the secreted form of ACE. Our results demonstrated that the secreted form of ACE could normalize kidney functions and RAS integrity, growth and development of Ace-/- mice, but not their blood pressure. This study clearly demonstrates that the secreted form of ACE cannot replace the tissue-bound ACE for maintaining normal blood pressure; a suitable balance between the tissue-bound and the soluble forms of ACE is essential for maintaining all physiological functions of ACE.
    PLoS ONE 01/2014; 9(1):e87484. DOI:10.1371/journal.pone.0087484 · 3.23 Impact Factor
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    ABSTRACT: Type I interferons (IFNα/β) limit viral dissemination prior to the emergence of adaptive immune responses through the concerted action of interferon stimulated genes (ISGs). Although IFNα/β induction by coronaviruses is modest, it effectively limits viral spread within the central nervous system (CNS) and protects from mortality. The protective roles of specific ISGs against the mouse hepatitis virus (MHV) members of coronaviruses are largely unknown. This study demonstrates a protective role of the ISG Ifit2 in encephalitis induced by the dual hepato- and neuro-tropic MHV-A59. Contrasting the mild encephalitis and 100% survival of infected wild-type (wt) mice, nearly 60% of MHV-A59 infected Ifit2-/- mice exhibited severe encephalitis and succumbed between 6-8 days post infection. Increased clinical disease in Ifit2-/- mice coincided with higher viral loads and enhanced viral spread throughout the CNS parenchyma. Ifit2-/- mice also expressed significantly reduced IFNα/β and downstream ISG mRNAs Ifit1, Isg15 and Pkr, while expression of proinflammatory cytokines and chemokines was only modestly affected in the CNS. Impaired IFNα/β induction in the absence of Ifit2 was confirmed by ex vivo mRNA analysis of microglia and macrophages, the prominent cell types producing IFNα/β following MHV CNS infection. Furthermore, both IFNα/β mRNA and protein production were significantly reduced in MHV infected Ifit2-/- relative to wt bone marrow derived macrophages. Collectively, the data implicate Ifit2 as a positive regulator of IFNα/β expression, rather than direct antiviral mediator, during MHV induced encephalitis.
    Journal of Virology 11/2013; 88(2). DOI:10.1128/JVI.02272-13 · 4.44 Impact Factor
  • Saurabh Chattopadhyay · Ying Zhang · Ganes C. Sen ·

    Annual Joint Conference of the International-Cytokine-Society and the; 09/2013
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    ABSTRACT: PKR is well characterized for its function in antiviral immunity. Using Toxoplasma gondii, we examined if PKR promotes resistance to disease caused by a non-viral pathogen. PKR(-/-) mice infected with T. gondii exhibited higher parasite load and worsened histopathology in the eye and brain compared to wild-type controls. Susceptibility to toxoplasmosis was not due to defective expression of IFN-γ, TNF-α, NOS2 or IL-6 in the retina and brain, differences in IL-10 expression in these organs or to impaired induction of T. gondii-reactive T cells. While macrophages/microglia with defective PKR signaling exhibited unimpaired anti-T. gondii activity in response to IFN-γ/TNF-α, these cells were unable to kill the parasite in response to CD40 stimulation. The TRAF6 binding site of CD40, but not the TRAF2,3 binding sites, was required for PKR phosphorylation in response to CD40 ligation in macrophages. TRAF6 co-immunoprecipitated with PKR upon CD40 ligation. TRAF6-PKR interaction appeared to be indirect, since TRAF6 co-immunoprecipitated with TRAF2 and TRAF2 co-immunoprecipitated with PKR, and deficiency of TRAF2 inhibited TRAF6-PKR co-immunoprecipitation as well as PKR phosphorylation induced by CD40 ligation. PKR was required for stimulation of autophagy, accumulation the autophagy molecule LC3 around the parasite, vacuole-lysosomal fusion and killing of T. gondii in CD40-activated macrophages and microglia. Thus, our findings identified PKR as a mediator of anti-microbial activity and promoter of protection against disease caused by a non-viral pathogen, revealed that PKR is activated by CD40 via TRAF6 and TRAF2, and positioned PKR as a link between CD40-TRAF signaling and stimulation of the autophagy pathway.
    PLoS Pathogens 08/2013; 9(8):e1003557. DOI:10.1371/journal.ppat.1003557 · 7.56 Impact Factor
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    ABSTRACT: The balance between the innate immunity of the host and the ability of a pathogen to evade it strongly influences pathogenesis and virulence. The two nonstructural (NS) proteins, NS1 and NS2, of respiratory syncytial virus (RSV) are critically required for RSV virulence. Together, they strongly suppress the type I interferon (IFN)-mediated in-nate immunity of the host cells by degrading or inhibiting multiple cellular factors required for either IFN induction or response pathways, including RIG-I, IRF3, IRF7, TBK1 and STAT2. Here, we provide evidence for the existence of a large and heterogeneous degradative complex assembled by the NS proteins, which we named "NS-degradasome" (NSD). The NSD is roughly ~300-750 kD in size, and its degradative activity was enhanced by the addition of purified mitochondria in vitro. Inside the cell, the majority of the NS proteins and the substrates of the NSD translocated to the mitochondria upon RSV infection. Genetic and pharmacological evidence shows that optimal suppression of in-nate immunity requires mitochondrial MAVS and mitochondrial motility. Together, we propose a novel paradigm in which the mitochondria, known to be important for the innate immune activation of the host, are also important for viral suppression of the innate immunity.
    Cell Research 07/2013; 23(23):1025-1042. DOI:10.1038/cr.2013.98 · 12.41 Impact Factor
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    Hyelim Cho · Bimmi Shrestha · Ganes C Sen · Michael S Diamond ·
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    ABSTRACT: Previous studies have demonstrated that type I interferon (IFN-I) restricts West Nile virus (WNV) replication and pathogenesis in peripheral and central nervous system (CNS) tissues. However, the in vivo role of specific antiviral genes that are induced by IFN-I against WNV infection remains less well characterized. Here, using Ifit2−/− mice, we defined the antiviral function of the interferon-stimulated gene (ISG) Ifit2 in limiting infection and disease in vivo by a virulent North American strain of WNV. Compared to congenic wild-type controls, Ifit2−/− mice showed enhanced WNV infection in a tissue-restricted manner, with preferential replication in the CNS of animals lacking Ifit2. Virological analysis of cultured macrophages, dendritic cells, fibroblasts, cerebellar granule cell neurons, and cortical neurons revealed cell type-specific antiviral functions of Ifit2 against WNV. In comparison, small effects of Ifit2 were observed on the induction or magnitude of innate or adaptive immune responses. Our results suggest that Ifit2 restricts WNV infection and pathogenesis in different tissues in a cell type-specific manner.
    Journal of Virology 06/2013; 87(15). DOI:10.1128/JVI.01097-13 · 4.44 Impact Factor
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    ABSTRACT: In Press. DOI and volume not yet received.
    Cell Research 04/2013; XXX(XXX):XXX. · 12.41 Impact Factor

Publication Stats

11k Citations
1,280.09 Total Impact Points


  • 1998-2015
    • Lerner Research Institute
      Cleveland, Ohio, United States
  • 1992-2014
    • Cleveland Clinic
      • • Department of Molecular Genetics
      • • Department of Molecular Biology
      Cleveland, Ohio, United States
  • 2011
    • Zhejiang University
      • School of Medicine
      Hangzhou, Zhejiang Sheng, China
  • 2000-2011
    • Case Western Reserve University
      • • School of Medicine
      • • Department of Biochemistry
      • • Department of Physiology and Biophysics
      Cleveland, Ohio, United States
  • 2010
    • University of Pittsburgh
      • Department of Immunology
      Pittsburgh, PA, United States
  • 2008
    • Comprehensive Cancer Centers of Nevada
      Las Vegas, Nevada, United States
  • 2006
    • Monash University (Australia)
      Melbourne, Victoria, Australia
  • 1996
    • Roche Institute of Molecular Biology
      Nutley, New Jersey, United States
  • 1995
    • Case Western Reserve University School of Medicine
      • Department of Biochemistry
      Cleveland, Ohio, United States
  • 1979-1989
    • Memorial Sloan-Kettering Cancer Center
      • Division of Molecular Biology
      New York City, New York, United States
  • 1983
    • Cornell University
      Ithaca, New York, United States
  • 1975-1979
    • Yale University
      • Department of Molecular Biophysics and Biochemistry
      New Haven, Connecticut, United States
  • 1978
    • University of New Haven
      New Haven, Connecticut, United States