Amotz Ziv-Av

Stanford Medicine, Stanford, California, United States

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Publications (7)35.37 Total impact

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    ABSTRACT: Hepatitis C virus (HCV) enters its target cell via clathrin-mediated endocytosis. AP2-associated protein kinase-1 (AAK1) and cyclin G-associated kinase (GAK) are host kinases that regulate clathrin adaptor proteins (APs)-mediated trafficking in the endocytic and secretory pathways. We previously reported that AAK1 and GAK regulate HCV assembly by stimulating binding of the μ subunit of AP-2, AP2M1, to HCV core. We also discovered that AAK1 and GAK inhibitors, including approved anticancer drugs, sunitinib and erlotinib, could block HCV assembly. Here, we hypothesized that AAK1 and GAK regulate HCV entry independently of their effect on HCV assembly. Indeed, silencing AAK1 and GAK expression inhibited entry of pseudoparticles and cell culture grown HCV and internalization of Dil-labeled HCV particles with no effect on HCV attachment or RNA replication. AAK1 or GAK depletion impaired epidermal growth factor (EGF)-mediated enhanced HCV entry and endocytosis of EGF receptor (EGFR), a HCV entry co-factor and erlotinib's cancer target. Moreover, either RNA interference-mediated depletion of AP2M1 or NUMB, the substrates of AAK1 and/or GAK, or overexpression of their phosphorylation-site mutants inhibited HCV entry. Last, in addition to their effect on assembly, sunitinib and erlotinib inhibited HCV entry at a postbinding step, their combination was synergistic, and their antiviral effect was reversed by either AAK1 or GAK overexpression. Together, these results validate AAK1 and GAK as critical regulators of HCV entry that function in part by activating EGFR, AP2M1, and NUMB, and as the molecular targets underlying the antiviral effect of sunitinib and erlotinib (in addition to EGFR), respectively. Understanding the host pathways hijacked by HCV is critical for developing host-centered anti-HCV approaches. Entry represents a potential target for antiviral strategies; however, no FDA-approved HCV entry inhibitors are currently available. We reported that two host kinases, AAK1 and GAK, regulate HCV assembly. Here, we provide evidence that AAK1 and GAK regulate HCV entry independently of their role in HCV assembly and define the mechanisms underlying AAK1- and GAK-mediated HCV entry. By regulating temporally distinct steps in the HCV lifecycle, AAK1 and GAK represent "master regulators" of HCV infection and potential targets for antiviral strategies. Indeed, approved anticancer drugs that potently inhibit AAK1 or GAK, inhibit HCV entry in addition to assembly. These results contribute to understanding the mechanisms of HCV entry and reveal attractive host targets for antiviral strategies as well as approved candidate inhibitors of these targets, with potential implications to other viruses that hijack clathrin-mediated pathways. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
    Journal of Virology 02/2015; DOI:10.1128/JVI.02705-14 · 4.65 Impact Factor
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    ABSTRACT: MicroRNAs (miRNAs) have emerged as potential cancer therapeutics; however, their clinical use is hindered by lack of effective delivery mechanisms to tumor sites. Mesenchymal stem cells (MSCs) have been shown to migrate to experimental glioma and to exert anti-tumor effects by delivering cytotoxic compounds. Here, we examined the ability of MSCs derived from bone marrow, adipose tissue, placenta and umbilical cord to deliver synthetic miRNA mimics to glioma cells and glioma stem cells (GSCs). We examined the delivery of miR-124 and miR-145 mimics as glioma cells and GSCs express very low levels of these miRNAs. Using fluorescently labeled miRNA mimics and in situ hybridization, we demonstrated that all the MSCs examined delivered miR-124 and miR-145 mimics to co-cultured glioma cells and GSCs via gap junction- dependent and independent processes. The delivered miR-124 and miR-145 mimics significantly decreased the luciferase activity of their respected reporter target genes, SCP-1 and Sox2, and decreased the migration of glioma cells and the self-renewal of GSCs. Moreover, MSCs delivered Cy3-miR-124 mimic to glioma xenografts when administered intracranially. These results suggest that MSCs can deliver synthetic exogenous miRNA mimics to glioma cells and GSCs and may provide an efficient route of therapeutic miRNA delivery in vivo.
    Oncotarget 02/2013; 4(2):346-61. · 6.63 Impact Factor
  • Rina Barouch-Bentov, Amotz Ziv-Av
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    ABSTRACT: Background: Novel therapies are urgently needed against hepatitis C virus (HCV) infection. HCV assembly is poorly understood and is currently not being targeted pharmacologically. We identified a conserved heretofore unrecognized YXXΦ motif (Φ is a bulky hydrophobic residue) within the HCV core (capsid) protein. This motif is homologous to sorting signals within host cargo proteins known to mediate binding of AP2M1, the μ subunit of clathrin adaptor protein complex 2, and intracellular trafficking. We hypothesized that core binds AP2M1, that this interaction is essential for infectious HCV production, and can be disrupted pharmacologically. Methods: Novel microfluidics affinity analysis, protein-fragment complementation assays, and co-immunoprecipitations were used to study core-AP2M1 binding in vitro, in cells, and in the context of HCV infection, respectively. Infectivity assays were combined with RNAi, genetic, dominant interfering, and pharmacological approaches for probing functional relevance of core-AP2M1 binding to the HCV life cycle. Quantitative confocal immunofluorescence analysis was used for studying the effect of disrupting this interaction on core's subcellular localization. Results: Core's YXXΦ motif mediates AP2M1 binding. Either YXXΦ core mutations, silencing AP2M1 expression or overepressing a dominant negative AP2M1 mutant dramatically inhibit intracellular and extracellular infectivity, consistent with a defect in HCV assembly. Core's YXXΦ motif mediates recruitment of AP2M1 to assembly sites on lipid droplets. Moreover, the observed defect in assembly following disruption of core-AP2M1 binding correlates with accumulation of core on lipid droplets and reduced core colocalization with the E2 (envelope) protein and markers of trans-Golgi network, the presumed site of HCV egress. AAK1 and GAK, serine/threonine kinases known to stimulate AP2M1 binding to host cargo proteins, regulate core-AP2M1 binding and are essential for HCV assembly. Last, approved anti-cancer drugs that inhibit AAK1 or GAK not only disrupt core-AP2M1 binding, but also significantly inhibit HCV assembly and infectious viral production. Conclusion: These results validate viral-host interactions essential for HCV assembly and yield compounds for pharmaceutical development.
    IDWeek 2012 Meeting of the Infectious Diseases Society of America; 10/2012
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    ABSTRACT: Novel therapies are urgently needed against hepatitis C virus infection (HCV), a major global health problem. The current model of infectious virus production suggests that HCV virions are assembled on or near the surface of lipid droplets, acquire their envelope at the ER, and egress through the secretory pathway. The mechanisms of HCV assembly and particularly the role of viral-host protein-protein interactions in mediating this process are, however, poorly understood. We identified a conserved heretofore unrecognized YXXΦ motif (Φ is a bulky hydrophobic residue) within the core protein. This motif is homologous to sorting signals within host cargo proteins known to mediate binding of AP2M1, the μ subunit of clathrin adaptor protein complex 2 (AP-2), and intracellular trafficking. Using microfluidics affinity analysis, protein-fragment complementation assays, and co-immunoprecipitations in infected cells, we show that this motif mediates core binding to AP2M1. YXXΦ mutations, silencing AP2M1 expression or overexpressing a dominant negative AP2M1 mutant had no effect on HCV RNA replication, however, they dramatically inhibited intra- and extracellular infectivity, consistent with a defect in viral assembly. Quantitative confocal immunofluorescence analysis revealed that core's YXXΦ motif mediates recruitment of AP2M1 to lipid droplets and that the observed defect in HCV assembly following disruption of core-AP2M1 binding correlates with accumulation of core on lipid droplets, reduced core colocalization with E2 and reduced core localization to trans-Golgi network (TGN), the presumed site of viral particles maturation. Furthermore, AAK1 and GAK, serine/threonine kinases known to stimulate binding of AP2M1 to host cargo proteins, regulate core-AP2M1 binding and are essential for HCV assembly. Last, approved anti-cancer drugs that inhibit AAK1 or GAK not only disrupt core-AP2M1 binding, but also significantly inhibit HCV assembly and infectious virus production. These results validate viral-host interactions essential for HCV assembly and yield compounds for pharmaceutical development.
    PLoS Pathogens 08/2012; 8(8):e1002845. DOI:10.1371/journal.ppat.1002845 · 8.06 Impact Factor
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    ABSTRACT: Gliomas are characterized by increased infiltration into the surrounding normal brain tissue. We recently reported that RTVP-1 is highly expressed in gliomas and plays a role in the migration of these cells, however the regulation of RTVP-1 expression in these cells is not yet described. In this study we examined the role of PKC in the regulation of RTVP-1 expression and found that PMA and overexpression of PKCα and PKCε increased the expression of RTVP-1, whereas PKCδ exerted an opposite effect. Using the MatInspector software, we identified a SRF binding site on the RTVP-1 promoter. Chromatin immunoprecipitation (ChIP) assay revealed that SRF binds to the RTVP-1 promoter in U87 cells, and that this binding was significantly increased in response to serum addition. Moreover, silencing of SRF blocked the induction of RTVP-1 expression in response to serum. We found that overexpression of PKCα and PKCε increased the activity of the RTVP-1 promoter and the binding of SRF to the promoter. In contrast, overexpression of PKCδ blocked the increase in RTVP-1 expression in response to serum and the inhibitory effect of PKCδ was abrogated in cells expressing a SRFT160A mutant. SRF regulated the migration of glioma cells and its effect was partially mediated by RTVP-1. We conclude that RTVP-1 is a PKC-regulated gene and that this regulation is at least partly mediated by SRF. Moreover, RTVP-1 plays a role in the effect of SRF on glioma cell migration.
    Cellular Signalling 07/2011; 23(12):1936-43. DOI:10.1016/j.cellsig.2011.07.001 · 4.47 Impact Factor
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    ABSTRACT: Here, we report the cloning and characterization of RTVP-1b, a novel splice variant of human RTVP-1, which was isolated from the U87 glioma cell line. Sequence analysis revealed that RTVP-1b contains an additional 71 base exon between exons 2 and 3 that is missing in RTVP-1, leading to a frame-shift and a different putative protein. The deduced protein was 237 amino acids in length, sharing the N-terminal 141 amino acids with RTVP-1. RT-PCR analysis demonstrated that RTVP-1b was expressed in a wide range of tissues and that its expression was different from that of RTVP-1. In contrast, RTVP-1 and RTVP-1b showed similar patterns of expression in astrocytic tumors; highly expressed in glioblastomas as compared to normal brains, low-grade astrocytomas and anaplastic oligodendrogliomas. Overexpression of RTVP-1b increased glioma cell proliferation but did not affect cell migration. Our results suggest that RTVP-1b represents a potential prognostic marker and therapeutic target in gliomas.
    Biochemical and Biophysical Research Communications 11/2007; 362(3):612-8. DOI:10.1016/j.bbrc.2007.08.138 · 2.28 Impact Factor
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    ABSTRACT: In this study, we examined the expression and functions of related to testes-specific, vespid, and pathogenesis protein 1 (RTVP-1) in glioma cells. RTVP-1 was expressed in high levels in glioblastomas, whereas its expression in low-grade astrocytomas and normal brains was very low. Transfection of glioma cells with small interfering RNAs targeting RTVP-1 decreased cell proliferation in all the cell lines examined and induced cell apoptosis in some of them. Overexpression of RTVP-1 increased astrocyte and glioma cell proliferation and the anchorage-independent growth of the cells. In addition, overexpression of RTVP-1 rendered glioma cells more resistant to the apoptotic effect of tumor necrosis factor-related apoptosis-inducing ligand and serum deprivation. To delineate the molecular mechanisms involved in the survival effects of RTVP-1, we examined the expression and phosphorylation of various apoptosis-related proteins. We found that overexpression of RTVP-1 decreased the phosphorylation of c-Jun-NH2-kinase and increased the expression of Bcl2 and that the protective effect of RTVP-1 was partially mediated by Bcl2. Finally, we found that RTVP-1 regulated the invasion of glioma cells as was evident by their enhanced migration through Matrigel and by their increased invasion in a spheroid confrontation assay. The increased invasive potential of the RTVP-1 overexpressors was also shown by the increased activity of matrix metalloproteinase 2 in these cells. Our results suggest that the expression of RTVP-1 is correlated with the degree of malignancy of astrocytic tumors and that RTVP-1 is involved in the regulation of the growth, survival, and invasion of glioma cells. Collectively, these findings suggest that RTVP-1 is a potential therapeutic target in gliomas.
    Cancer Research 05/2006; 66(8):4139-48. DOI:10.1158/0008-5472.CAN-05-2851 · 9.28 Impact Factor

Publication Stats

68 Citations
35.37 Total Impact Points

Institutions

  • 2012–2015
    • Stanford Medicine
      • Division of Infectious Diseases and Geographic Medicine
      Stanford, California, United States
    • Stanford University
      • Department of Medicine
      Palo Alto, California, United States
  • 2013
    • Henry Ford Hospital
      • Department of Radiation Oncology
      Detroit, Michigan, United States
  • 2006–2011
    • Bar Ilan University
      • Faculty of Life Sciences
      Ramat Gan, Tel Aviv, Israel