ESCRT-Related protein PTPN23 as a cofactor for HIV-1 Vpu

项目总结 人类免疫缺陷病毒操纵宿主细胞过程以促进病毒的合成 组分，必须适当地定位到亚细胞区域，以便病毒萌芽和释放。在……里面 除了所有逆转录病毒共有的结构Gag、Pol和Env多蛋白外，HIV-1还编码四种 “辅助”蛋白：VPU、Nef、Vif和Vpr，它们的功能是促进寄主的适应性和先天逃避 免疫反应。这些病毒辅助蛋白共同选择宿主降解和蛋白运输过程 通过作为分子适配器与目标宿主因子形成三元络合物，包括 由宿主“限制因子”和宿主贩运的组成部分提供的固有细胞免疫 机械设备。阐明宿主和病毒蛋白促进或抑制感染的机制可能 导致确定治疗干预的目标。 我们最近发现了一种新的HIV-1辅助因子，ESCRT相关蛋白PTPN23(HD-PTP)，它 似乎是VPU活动的辅助因子。PTPN23的瞬时敲除阻止了VPU的介导 降解BST-2，抑制病毒释放。有趣的是，PTPN23不仅是BST-2所需的 降解，但也用于表面下调的CD4。此外，我们之前(未发表的)研究 支持网状蛋白和网状蛋白接头AP-2在VPU介导的CD4表面下调中的作用。我们 假设VPU介导的CD4拮抗作用至少部分是由内吞作用和溶酶体介导的 不完全是通过类似ERAD的机制来解决退化问题。 在这里，我们建议确定PTPN23是否作为VPU介导的CD4降解的辅助因子，以及 阐明VPU与PTPN23相互作用的分子机制。我们还将验证PTPN23是否为 原代T细胞中VPU活性的辅助因子，以证明其在病毒感染环境中的适用性。我们会 进一步定义表面下调和/或ESCRT途径所需的其他组件 降解的CD_4。阐明VPU和ESCRT相关蛋白之间的分子相互作用将 确定治疗干预的目标；通过抑制VPU的抗免疫活动，我们将使感染的人变得敏感 细胞检测和免疫清除。

PROJECT SUMMARY The Human Immunodeficiency Virus manipulates host cellular processes to promote synthesis of viral components, which must be appropriately localized to subcellular domains for viral budding and release. In addition to the structural Gag, Pol and Env polyproteins common to all retroviruses, HIV-1 encodes four “accessory” proteins: Vpu, Nef, Vif and Vpr, which function to promote evasion of host adaptive and innate immune responses. These viral accessory proteins co-opt host degradative and protein-trafficking processes by functioning as molecular adaptors that form ternary complexes with targeted host factors, including the intrinsic cellular immunity provided by host “restriction factors”, and components of the host trafficking machinery. Elucidation of the mechanisms by which host and viral proteins can promote or inhibit infection may lead to the identification of targets for therapeutic intervention. We have recently identified a novel HIV-1 cofactor, ESCRT-associated protein, PTPN23 (HD-PTP), which appears to function as a cofactor for Vpu activities. Transient knockdown of PTPN23 prevented Vpu-mediated degradation of BST-2 and inhibited virus release. Interestingly, PTPN23 is not only for required for BST-2 degradation, but also for surface downregulation of CD4. Furthermore, our previous (unpublished) studies support a role for clathrin and clathrin adaptor AP-2 in Vpu-mediated surface downregulation of CD4. We hypothesize that Vpu-mediated antagonism of CD4 is mediated at least in part by endocytosis and lysosomal degradation rather than exclusively by ERAD-like mechanisms. Here, we propose to determine whether PTPN23 acts as a cofactor for Vpu-mediated degradation of CD4, and elucidate the molecular mechanisms by which Vpu interacts with PTPN23. We will also validate PTPN23 as a cofactor for Vpu activities in primary T-cells to demonstrate applicability in a viral infection setting. We will further define additional components of the ESCRT pathway necessary for surface downregulation and/or degradation CD4. Elucidating the molecular interactions between Vpu and ESCRT-associated proteins will define targets for therapeutic intervention; by inhibiting Vpu's anti-immune activities we will sensitize infected cells to detection and immune clearance.