Viral Hijacking of Host Membrane Trafficking Pathways

描述(申请人提供)：宿主细胞表面有各种各样的免疫分子来检测和攻击外来颗粒，包括那些在病毒感染时引入的颗粒。反过来，病毒也发展出了同样令人印象深刻的方法来逃避宿主的防御，例如劫持细胞膜运输机器来下调宿主的固有和适应性免疫分子。例如，艾滋病毒将其主要受体CD4从细胞膜上移除，以避免干扰病毒的释放和传染性；它阻止MHC-I到达细胞表面，以逃避细胞毒性T细胞的免疫监视；它从细胞表面移除固有的宿主限制因子BST2(也称为tetherin)，以允许后代病毒粒子的有效释放。HIV VPu是一种跨膜蛋白，HIV Nef是一种外周膜蛋白，它们通过将靶蛋白与宿主蛋白运输机制的组成部分连接起来，从而通过错误定位和降解来灭活宿主防御蛋白来完成这些任务。这项建议的重点是建立Nef和VPU劫持宿主膜运输途径的机制，以下调细胞表面免疫分子的表达。我们的方法包括X射线结晶学和单粒子电子显微镜的结构测定。它以新颖的融合蛋白策略为特色，允许研究水溶液中膜介导的相互作用。它的特点是在分子和结构水平上对复合体进行细胞生物学和病毒学验证。我们的工作将极大地促进我们对细胞膜上各种宿主-病毒相互作用的理解，并确定新的抗病毒药物靶点。抑制这些靶点将使病毒无法对细胞膜进行调节，并有可能增强宿主免疫力，以更有效地控制艾滋病毒感染。此外，为我们的研究项目设计的实验系统将为研究宿主-病原体关系和膜蛋白相互作用提供有价值的新工具。

DESCRIPTION (provided by applicant): The host cell surface has a diverse repertoire of immune molecules to detect and attack foreign particles, including those introduced upon viral infections. Viruses, in turn, have developed an equally impressive arsenal of methods to evade host defenses, such as hijacking cellular membrane trafficking machinery to downregulate host innate and adaptive immune molecules. For example, HIV removes its primary receptor, CD4, from cellular membranes to avoid interference with viral release and infectivity; it prevents MHC-I from reaching the cell surface to evade immune surveillance by cytotoxic T cells; and it removes the innate host restriction factor BST2 (also known as tetherin) from the cell surface to allow for the efficient release of progeny virions. HIV Vpu, a transmembrane protein, and HIV Nef, a peripheral membrane protein, accomplish these tasks by linking targeted proteins to components of the host protein trafficking machinery, thereby inactivating host defense proteins through mislocalization and degradation. The focus of this proposal is to establish the mechanisms by which Nef and Vpu hijack host membrane trafficking pathways to down regulate the expression of immune molecules at the cell surface. Our approach includes structure determination by X-ray crystallography and single particle electron microscopy. It features novel fusion-protein strategies that allow the investigation of membrane-mediated interactions in aqueous solution. It features cell biologic and virologic validation of the complexes at both the molecular and structural levels. Our work will significantly advance our understanding of a diverse range of host-viral interactions at cellular membranes and identify new antiviral drug-targets. Inhibition of these targets would disable viral modulation of cellular membranes and potentially empower host immunity to more effectively control an HIV infection. Moreover, the experimental systems devised for our research project will provide valuable new tools for the studies of host-pathogen relationships and membrane protein interactions.