MHC-1 REGULATION BY VIRUS

描述（由申请方提供）：细胞毒性T淋巴细胞在MHCI蛋白背景下识别病毒肽是消除病毒感染细胞的关键事件。在细胞表面呈递肽之前，MHCI蛋白必须通过与肽装载复合物（PLC）的成员瞬时相互作用在内质网的内腔中经历严格的成熟过程。在从PLC解离后，肽结合的MHCI蛋白在分泌途径后通过高尔基体转运到表面。已知分泌途径涉及一系列在货物运输中具有专门功能的膜结合区室;然而，该途径的许多分子细节尚未阐明。为了解决MHCI生物合成沿着分泌途径的突出问题，我们将使用病毒免疫逃避蛋白作为生理途径的探针。病毒编码大量的免疫逃避蛋白，这些蛋白利用令人惊讶的多种生理途径来阻断抗原呈递，并且它们以极大的特异性和效力这样做。这些特性使得免疫逃避蛋白成为用于定义与MHCI功能特别相关的蛋白质质量控制的分子途径的高效探针。在这项研究中，我们将使用免疫逃避蛋白来探测i）错误折叠的MHCI蛋白如何被识别并从ER腔转移到胞质溶胶，ii）ER到高尔基体再循环的机制及其对MHC质量控制和启动ERAD的重要性，以及iii）赖氨酸与丝氨酸MHCI残基的泛素化对ERAD和质膜再循环的生理作用。拟议的实验将使用细胞生物学，生物化学和结构的方法，由汉森和弗里蒙特实验室的合作努力。

DESCRIPTION (provided by applicant): The recognition of viral peptides in the context of MHCI proteins by cytotoxic T lymphocytes is a key event for eliminating virus-infected cells. Prior to presenting peptides at the cell surface, MHCI proteins must undergo a stringent maturation process in the lumen of the endoplasmic reticulum by transiently interacting with members of the peptide loading complex (PLC). After dissociation from the PLC, peptide-bound MHCI proteins transit through the Golgi to the surface following the secretory pathway. The secretory pathway is known to involve a series of membrane bound compartments with specialized functions in cargo transport; however, many of the molecular details of this pathway have yet to be elucidated. To resolve outstanding questions of MHCI biosynthesis along the secretory pathway, we will use viral immune evasion proteins as probes for physiologic pathways. Viruses encode a plethora of immune evasion proteins that exploit a surprising diversity of physiologic pathways to block antigen presentation and they do so with great specificity and potency. These properties make immune evasion proteins highly effective probes for defining molecular pathways of protein quality control that are of particular relevance to MHCI function. In this grant, we will use immune evasion proteins to probe i) how misfolded MHCI proteins are identified and translocated from the ER lumen to the cytosol, ii) mechanisms of ER to Golgi recycling and their importance for MHC quality control and initiating ERAD, and iii) the physiologic role of ubiquitination of lysine vs. serine MHCI residues for ERAD and recycling from the plasma membrane. The proposed experiments will use cell biological, biochemical, and structural approaches employed by collaborative efforts of the Hansen and Fremont labs.