Endogenous MHC class II antigen processing via autophagy

描述（由申请人提供）：肿瘤细胞使用两个蛋白水解区室来降解不正确合成的和其他受损的蛋白质、蛋白酶体和溶酶体。当肽分别通过MHC I类和MHC II类呈现时，免疫系统监测这两个系统的降解产物。Th1 CD4+ T细胞识别MHC II类，CD8+ T细胞识别MHC I类，将导致感染细胞和恶性细胞的破坏。我们最近描述了致癌爱泼斯坦巴尔病毒（EBNA1）的核抗原1在自噬后获得MHC II类递呈。我们现在在这个应用中提出三个目的来研究抗原的自噬传递是否构成内源性MHC II类抗原加工的一般途径。1. 在I型和II型干扰素免疫激活以及病毒感染期间和之后，人体组织中自噬水平和与MHC II类负载区重叠的分析。我们将定量评估有免疫激活和没有免疫激活的不同人体组织中的自噬水平，并解决自噬体和MHC II类装载囊泡之间的重叠。2. 病毒和肿瘤抗原自噬途径致MHC II类表现的特点。我们将研究其他病毒和肿瘤抗原是否遵循MHC II类呈递的自噬途径，CD4+ T细胞在内源性加工后能够识别这些抗原。我们将构建EBNA1缺失突变体，并分析其自噬后进入内源性MHC II类抗原加工的能力。该分析将揭示该降解路径的目标底物的结构域。3. 靶向内源性抗原的自噬降解和MHC II类递呈。我们将把已知的CD4+ T细胞抗原靶向自噬体，通过延长其半衰期来改善MHC II类递呈，因为长寿命蛋白主要通过自噬处理。此外，我们将瞄准伴侣蛋白介导的信号肽自噬和LC3/Atg8蛋白的巨噬，LC3/Atg8蛋白在附着于自噬体内膜后在溶酶体中被部分降解。这些研究将使我们更好地了解肿瘤是如何被免疫系统检测到的，以及我们如何增强对癌症的免疫反应。

DESCRIPTION (provided by applicant): Tumor cells use two proteolytic compartments to degrade incorrectly synthesized and other damaged proteins, proteasomes and lysosomes. The immune system then monitors the degradation products of these two systems when the peptides are presented via MHC class I and II, respectively. Recognition of MHC class II by Th1 CD4+ T cells and MHC class I by cytolytic CD8+ T cells will result in the destruction of infected and malignant cell. We have recently described that the nuclear antigen 1 of the oncogenic Epstein Barr virus (EBNA1) gains access to MHC class II presentation after autophagy. We now propose in this application to investigate in three aims if autophagic delivery of antigens constitutes a general pathway of endogenous MHC class II antigen processing. 1. Analysis of autophagy levels and overlap with MHC class II loading compartments in human tissues, during steady state and after immune activation by type I and II Interferons as well as viral infections. We will quantitatively assess the autophagy level in different human tissues with and without immune activation and address the overlap between autophagosomes and MHC class II loading vesicles. 2. Characteristics of viral and tumor antigens following an autophagic route to MHC class II presentation. We will investigate if other viral and tumor antigens, for which CD4+ T cell recognition after endogenous processing was demonstrated, follow the autophagic route for MHC class II presentation. We will construct deletion mutants of EBNA1 and analyze their capacity to access endogenous MHC class II antigen processing after autophagy. This analysis will reveal domains that target substrates for this degradation path. 3. Targeting of endogenous antigens for autophagic degradation and MHC class II presentation. We will target known CD4+ T cell antigens to autophagosomes for improved MHC class II presentation by extending their half-lifes, since long-lived proteins are primarily processed via autophagy. In addition, we will target for chaperone mediated autophagy with signal peptides and for macroautophagy with the LC3/Atg8 protein, which gets partially degraded in lysosomes after attachment to the inner autophagosome membrane. These studies will allow us to understand better how tumors can be detected by the immune system and how we can enhance immune responses to cancer.