CLASS II ANTIGEN PRESENTATION VIA CHAPERONE MEDIATED AUTOPHAGY

描述（由申请人提供）：源自外源和自身抗原的肽在 MHC II 类分子的背景下呈递，以供 CD4 T 细胞识别。 II 类分子穿过细胞的内体网络，从外源抗原以及内源细胞表面和内体蛋白获取肽。令人惊讶的是，来自细胞质抗原的表位也由 II 类分子呈递。该提案的总体目标是了解调节 II 类细胞质 Ag 呈递的机制，并确定调节对自身和肿瘤 Ag 免疫的新方法。随着肿瘤和病毒对 I 类呈递的颠覆，探索细胞质 Ag 呈递的新途径仍然很重要。针对 II 类呈递的特定细胞质 Ag 提供了一种独特的方法来促进免疫识别并克服此类免疫逃避。目前的提案重点关注选择性途径，伴侣介导的自噬（CMA），它促进 II 类细胞质抗原的呈递。我们提出，在 CMA 过程中，细胞质伴侣选择性地靶向细胞质抗原进行蛋白水解。然后，所得肽可陪伴膜转运蛋白 LAMP-2A 易位至内体网络中进行 II 类呈递。建议开展研究来明确伴侣、HSC70 和 HSP90 在指导细胞质抗原加工和易位到细胞器中进行 II 类呈递方面的重要性。 LAMP-2 基因的多种亚型在 B 细胞和黑色素瘤中表达，可能通过自噬调节 II 类细胞质抗原呈递。拟开展研究以阐明各个 LAMP-2 同工型在 II 类呈递途径中的作用。该项目将为 CMA 的分子事件和重要辅助因子提供重要见解，从而促进 II 类接触细胞质抗原进行免疫识别。值得注意的是，肿瘤细胞中的自噬途径通常上调，以促进肿瘤生长和存活。细胞自噬途径的这种变化可能会增强肿瘤抗原的识别。该项目的研究将探讨不同自噬途径在黑色素瘤细胞质抗原呈递中的重要性。这项工作也与我们对自身抗原的自身免疫和耐受诱导的理解相关。利用 CMA 途径的选择性也可能为疫苗开发新方法提供机会。 公共健康相关性：这项工作与我们对免疫系统如何区分自身分子和外来分子的一般理解相关。该项目对癌症具有重要意义，因为肿瘤中的自噬通常上调，这可以用来促进肿瘤细胞的免疫识别。这些研究对于理解自身免疫也可能很重要，并带来疫苗开发的新方法。

DESCRIPTION (provided by applicant): Peptides derived from foreign and self antigens are presented in the context of MHC class II molecules for recognition by CD4+ T cells. Class II molecules transit the endosomal network of cells, acquiring peptides from exogenous antigens as well as endogenous cell surface and endosomal proteins. Surprisingly, epitopes from cytoplasmic antigens also are presented by class II molecules. The overall goal of this proposal is to understand the mechanisms regulating class II cytoplasmic Ag presentation, and to identify new means to modulate immunity to self and tumor Ags. With subversion of class I presentation by tumors and viruses, exploiting novel pathways for cytoplasmic Ag presentation remains important. Targeting specific cytoplasmic Ags for class II presentation offers a unique approach to promote immune recognition and overcome such immune evasion. The current proposal focuses on a selective pathway, chaperone mediated autophagy (CMA) which facilitates class II cytoplasmic antigen presentation. We propose that cytoplasmic antigens are selectively targeted by cytosolic chaperones for proteolysis during CMA. The resulting peptides may then be chaperoned to a membrane transporter, LAMP-2A for translocation into the endosomal network for class II presentation. Studies are proposed to define the importance of chaperones, HSC70 and HSP90 in guiding cytoplasmic antigens for processing and translocation into organelles for class II presentation. Multiple isoforms of the LAMP-2 gene are expressed in B cells and melanomas, potentially regulating class II cytoplasmic antigen presentation by autophagy. Studies are proposed to elucidate the role of individual LAMP- 2 isoforms in class II presentation pathways. This project will offer critical insights into the molecular events and essential co-factors for CMA which faciliate class II access to cytoplasmic antigens for immune recognition. Notably, autophagy pathways are often up-regulated in tumor cells to promote tumor growth and survivial. Such changes in cellular autophagy pathways may enhance tumor antigen recognition. Studies in this project will examine the importance of distinct autophagy pathways in cytoplasmic antigen presentation by melanomas. This work also has relevance to our understanding of autoimmunity to self antigens and tolerance induction. Exploiting the selectivity of the CMA pathway may also offer opportunities for novel approaches to vaccine development. PUBLIC HEALTH RELEVANCE: This work has relevance to our general understanding of how the immune system distinguishes self and foreign molecules. The project has implications for cancer as autophagy is often up-regulated in tumors, and this could be exploited to promote immune recognition of tumor cells. These studies may also be important in understanding autoimmunty, and lead to new approaches for vaccine development.