Role of PACS-1 in HIV-1 Immunoevasion

描述（由申请人提供）：该项目的长期目标是了解HIV-1 Net如何破坏细胞蛋白质运输和信号转导机制，以反击宿主细胞的抗病毒反应。宿主细胞有一个双臂反应来对抗病毒：免疫监视和细胞凋亡。HIV-1主要使用单一基因Nef来阻断这种反应的多个方面。例如，Nef诱导MHC-I下调、细胞凋亡阻断和胸腺中T细胞发育的破坏。Nef如何在抗病毒反应的反击中发挥如此多的不同作用仍不清楚。我们已经确定了HIV-1 Nef用于下调MHC-I的潜在膜运输/信号传导途径。我们确定Nef和细胞运输蛋白PACS-1联合收割机篡夺PI3 K依赖性、ARF6控制的内吞途径，下调细胞表面MHC-I至trans-Golgi网络。这一发现表明，PACS-1/Nef控制的PI3K激活可能对MHC-I的下调以及实施整个系列的HIV-1 Nef的反击措施很重要。我们的初步数据表明，一种新的信号通路是实现这一目标的关键，但关于这一通路的许多信息仍然未知。我们已经发现，当HIV-1 Nef海盗PACS-1靶向TGN时，该途径开始，使Nef能够招募Src家族激酶（SFK）;随后，该复合物结合并激活PI3K。PI3K然后激活ARF6以下调MHC-I至TGN。该途径还激活PAK 2，PAK 2阻断细胞凋亡，似乎是HIV-1阻止T细胞成熟所必需的。我们的中心假设是PACS-1/Nef-SFK-PI3K通路允许Nef阻碍宿主的抗病毒反应。目标1将确定HIV-1 Nef如何篡夺PACS-1分选途径在TGN招募SFK。目标2将确定HIV-1 Nef如何破坏SFK以激活PI3K，并将测试PACS-1/Nef-SFK-PI3K轴是否协调不同细胞库中宿主抗病毒反应的反击。目的3将确定HIV-1 Nef如何通过ARF6控制的内吞途径下调MHC-I至TGN。阐明Nef诱导的信号通路如何被HIV-1使用将更好地理解HIV-1发病机制的生化基础，并将确定对抗这种致命病毒的新靶点。

DESCRIPTION (provided by applicant): The long-term goal of this project is to understand how HIV-1 Net pirates the cellular protein trafficking and signal transduction machinery to counterattack the host cell antiviral response. Host cells have a two-armed response to combat viruses: immune surveillance and apoptosis. HIV-1 uses primarily a single gene, Nef, to block the multiple aspects of this response. For example, Nef induces MHC-I downregulation, a block of apoptosis, and disruption of T-cell development in the thymus. How Nef plays so many different roles in the counterattack of the antiviral response remains unclear. We have identified the underlying membrane trafficking/signaling pathway used by HIV-1 Nef to downregulate MHC-I. We determined that Nef and the cellular trafficking protein PACS-1 combine to usurp a PI3K-dependent, ARF6-controlled endocytic pathway to downreg ulate cell-surface MHC-I to the trans-Golgi network. This discovery suggests that the PACS- 1/Nef controlled activation of PI3K may be important for downregulation of MHC-I and also for implementing the entire array of HIV-1 Nef's counterattack measures. Our preliminary data suggests a novel signaling pathway is the key to this implementation, but much about this pathway remains unknown. We have found that this pathway begins when HIV-1 Nef pirates PACS-1 to target to the TGN, enabling Nef to recruit a Src family kinase (SFK); subsequently, this complex binds to and activates PI3K. PI3K then activates ARF6 to downregulate MHC-I to the TGN. This pathway also activates PAK2, which blocks apoptosis and appears to be required for HIV-1 to arrest T-cell maturation. Our central hypothesis is that this PACS-1/Nef-SFK-PI3K pathway allows Nef to thwart the host's antiviral response. Aim 1 will determine how HIV-1 Nef usurps the PACS-1 sorting pathway to recruit SFKs at the TGN. Aim 2 will determine how HIV-1 Nef subverts SFKs to activate PI3K and will test if the PACS-1/Nef-SFK-PI3K axis coordinates the counterattack of the host antiviral response in different cellular reservoirs. Aim 3 will determine how HIV-1 Nef pirates the ARF6- controlled endocytic pathway to downregulate MHC-I to the TGN. Elucidating how this Nef-induced signaling pathway is used by HIV-1 will provide better understanding of the biochemical basis underlying HIV-1 pathogenesis and will identify new targets to combat this deadly virus.