The Vpu protein is a small membrane bound protein that has been shown to: a) down-modulate CD4 from the cell surface by shunting CD4 to the proteasome pathway; b) facilitate the release of virions from the infected cell; and c) have an ion channel activity. A major drawback in studying the role of Vpu in lentiviral pathogenesis has been lack of a vpu gene in simian immunodeficiency virus (SIV), which has been the most commonly used macaque model to study AIDS pathogenesis. As an alternative to the SIV/macaque model, chimeric simian-human immunodeficiency viruses (SHIVs) have been developed that contain the tat, rev, vpu, and env genes from HIV-1 in a genetic background of SIVmac239 and have been used to derive pathogenic variants that when inoculated into pig-tailed or rhesus macaques, cause high virus burdens, massive CD4+ T cell loss and AIDS, and death within 6 months to 1 year. Studies from our laboratory have indicated that the Vpu does play a role in the CD4+ T cell loss caused by these viruses. We have recently developed a Vpu/enhanced green fluorescent protein fusion protein reporter system (VpuEGFP) that mimics the intracellular transport, intracellular stability and CD4 down-regulation of Vpu protein within virus infected cells. In this proposed studies, we will use a recently developed VpuEGFP reporter system to: a) assess the role of the different Vpu domains on the retention of subtype B Vpu in the Golgi complex; b) to use site-directed mutagenesis to analyze the role of the structure-function relationships of the amino acids comprising the cytoplasmic domain of the subtype B Vpu; and c) to compare the biological properties with the divergent Vpu proteins from subtype C isolates of HIV-1. Finally, we will introduce Vpu proteins having altered biological properties in a molecular clone of SHIV to assess the role of the different biological properties of Vpu on CD4+ T cell loss caused by SHIV in pig-tailed macaques. The proposed studies will provide new information on the structure-function relationships of the different domain s of Vpu and the role of the different biological properties of Vpu on HIV-1 pathogenesis.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
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Special Emphasis Panel (ZRG1-AARR-1 (01))
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Sharma, Opendra K
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University of Kansas
Schools of Medicine
Kansas City
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Ruiz, Autumn; Schmitt, Kimberly; Culley, Nathan et al. (2013) Simian-Human immunodeficiency viruses expressing chimeric subtype B/C Vpu proteins demonstrate the importance of the amino terminal and transmembrane domains in the rate of CD4(+) T cell loss in macaques. Virology 435:395-405
Skasko, Mark; Wang, Yan; Tian, Ye et al. (2012) HIV-1 Vpu protein antagonizes innate restriction factor BST-2 via lipid-embedded helix-helix interactions. J Biol Chem 287:58-67
Schmitt, Kimberly; Guo, Kejun; Algaier, Malinda et al. (2011) Differential virus restriction patterns of rhesus macaque and human APOBEC3A: implications for lentivirus evolution. Virology 419:24-42
Ruiz, Autumn; Guatelli, John C; Stephens, Edward B (2010) The Vpu protein: new concepts in virus release and CD4 down-modulation. Curr HIV Res 8:240-52
Ruiz, Autumn; Hill, M Sarah; Schmitt, Kimberly et al. (2010) Membrane raft association of the Vpu protein of human immunodeficiency virus type 1 correlates with enhanced virus release. Virology 408:89-102
Schmitt, Kimberly; Hill, M Sarah; Liu, Zhenqian et al. (2010) Comparison of the replication and persistence of simian-human immunodeficiency viruses expressing Vif proteins with mutation of the SLQYLA or HCCH domains in macaques. Virology 404:187-203
Ruiz, Autumn; Lau, David; Mitchell, Richard S et al. (2010) BST-2 mediated restriction of simian-human immunodeficiency virus. Virology 406:312-21
Hill, M Sarah; Ruiz, Autumn; Schmitt, Kimberly et al. (2010) Identification of amino acids within the second alpha helical domain of the human immunodeficiency virus type 1 Vpu that are critical for preventing CD4 cell surface expression. Virology 397:104-12
Mitchell, Richard S; Katsura, Chris; Skasko, Mark A et al. (2009) Vpu antagonizes BST-2-mediated restriction of HIV-1 release via beta-TrCP and endo-lysosomal trafficking. PLoS Pathog 5:e1000450
Schmitt, Kimberly; Hill, M Sarah; Ruiz, Autumn et al. (2009) Mutations in the highly conserved SLQYLA motif of Vif in a simian-human immunodeficiency virus result in a less pathogenic virus and are associated with G-to-A mutations in the viral genome. Virology 383:362-72

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