Ubiquitin conjugation and direct MHC class I antigen presentation

说明(申请人提供)：免疫系统必须清除由于细胞内感染或致癌转化而患病的身体细胞。CD8+细胞毒性T细胞负责完成这一任务，必须能够区分健康细胞和患病细胞。主要的组织相容性复合体I类(MHC I类)分子存在于大多数有核细胞上，负责将抗原呈递到细胞表面，用于CD8+T细胞的检测。为了呈递抗原，MHC I类途径依赖于与短肽的结合，短肽是由降解的细胞蛋白产生的。当来源蛋白与疾病(如病毒蛋白或肿瘤相关蛋白)相关时 CD8+T细胞会识别多肽-MHC-I类复合体，并杀死细胞。由于多肽在这一反应中提供了最终的特异性，我们有兴趣了解这些多肽是如何产生的。我们的数据表明，合成后迅速降解的蛋白质(称为缺陷核糖体蛋白或水滴)负责有效地产生多肽供应。这项建议试图确定哪些细胞代谢途径被用来指导滴滴的快速降解，并确定在生理相关的环境中是否需要滴滴。我们关注的是泛素偶联途径，因为泛素偶联与蛋白质降解密切相关。这项建议的具体目的是确定哪些E3泛素连接酶是水滴抗原提呈所必需的，了解为什么泛素样分子Nedd8的结合对于水滴抗原提呈是必要的，以及识别和表征针对去泛素化酶(DUBS)的水滴抗原提呈的化学抑制剂。

DESCRIPTION (provided by applicant): The immune system must eliminate cells of the body that have become diseased as the result of intracellular infection or oncogenic transformation. CD8+ cytotoxic T cells are responsible for completing this task and must be able to distinguish healthy cells from diseased ones. Major Histocompatibility Complex Class I (MHC class I) molecules are present on most nucleated cells and are responsible for presenting antigen at the cell surface for CD8+ T cell inspection. In order to present antigen, the MHC class I pathway relies on binding to short peptides, created from degraded cellular proteins. When the source protein is associated with a disease (such as a viral protein or tumor associated protein) specific CD8+ T cells will recognize the peptide- MHC class I complex and kill the cell. Because the peptide provides the ultimate specificity in this reaction, we are interested in understanding how these peptides are created. Our data indicates that proteins which are rapidly degraded following their synthesis (termed Defective Ribosomal Proteins or DRiPs) are responsible for efficiently generating a supply of peptides. This proposal seeks to determine which cellular metabolic pathways are used to direct the rapid degradation of DRiPs and to determine if DRiPs are necessary in physiologically relevant settings. We are focusing on the ubiquitin conjugation pathway, as ubiquitin coupling is intimately associated with protein degradation. The Specific Aims of this proposal are to determine which E3 ubiquitin ligases are necessary for DRiP antigen presentation, understand why conjugation of the ubiquitin-like molecule Nedd8 is necessary for DRiP antigen presentation, and identify and characterize chemical inhibitors of DRiP antigen presentation that target de-ubiquitinating enzymes (DUBs).