ER PROTEINS EFFECT ON CLASS I MHC ASSEMBLY

细胞免疫系统对病毒和肿瘤的防御依赖于 来自病毒或肿瘤特异性蛋白质的肽的呈递 到T淋巴细胞。这些肽必须与细胞表面1类结合 主要组织相容性复合体（MHC）重链被 淋巴细胞1类MHC重链、轻链和轻链的组装 称为β 2-微球蛋白（β 2-m）和肽进入 异源三聚体，完整的I类MHC分子存在于内质网中， 网织膜（ER）。在第1类装配期间，ER驻留蛋白如 钙网蛋白，与抗原加工相关的转运蛋白（TAP）， 和tapasin与无肽的1类重链/β 2-m相互作用。的 这项研究的长期目标是了解机制， 在肽负载水平上调节免疫应答， 1类MHC分子的组装。前三项研究描述在 本拨款建议书将界定每个应急反应的单独作用 在肽加载之前保持1类蛋白质，并且将 探索它们与第一类分子相互作用的本质。 具体来说，这些研究将1）确定类1的重要性 钙网蛋白的重链糖基化和α 3结构域 与类1，2）定义钙网蛋白在ER中的作用 通过使用过表达，低表达， 或不表达钙调蛋白，以及3）确定TAP， 钙调蛋白或塔帕辛负责肽诱导的释放 1级急诊室滞留。的装配和曲面表达式 1类分子被几种病毒蛋白阻断。知识 1类装配中的病毒干扰机制可以揭示一个很大的 处理抗原呈递的正常过程。的一个示例 这样的病毒蛋白是腺病毒E3 - 19K蛋白，其弱表达， 与免疫球蛋白超基因家族的成员同源，因此可能 有一种尚未发现的细胞同源物E3 - 19K是否取代 肽或任何正常的ER蛋白， 钙网蛋白、TAP或塔帕辛）是未知的。为了解决这些问题， 本提案的最终目的是确定1级重型 与E3 - 19K结合的链被肽占据，如果它们失去了 与ER伴侣的关系。总之，这些研究将产生新的 了解抗原呈递的调节，将有助于 在未来设计合理的临床治疗方法时， 癌症和病毒性疾病。

The cellular immune system defense against viruses and tumors depends on the presentation of peptides derived from viral or tumor-specific proteins to T lymphocytes. These peptides must be bound by cell-surface class 1 major histocompatibility complex (MHC) heavy chains to be recognized by lymphocytes. Assembly of the class 1 MHC heavy chains, a light chain called beta 2-microglobulin (beta 2-m) and peptide into the heterotrimeric, complete class I MHC molecule occurs in the endoplasmic reticulum(ER). During class 1 assembly, ER resident proteins such as calreticulin, the transporter associated with antigen processing (TAP), and tapasin interact with peptide-free class 1 heavy chain/beta 2-m. The long-term goals of this study are to understand the mechanism and regulation of the immune response at the level of peptide loading and assembly of the class 1 MHC molecule. The first three studies described in this grant proposal will define the separate roles of each of these ER proteins in the retention of class 1 prior to peptide loading and will probe the nature of their molecular interactions with class 1. Specifically, these studies will 1) determine the importance of class 1 heavy chain glycosylation and the alpha 3 domain for calreticulin association with class 1, 2) define the role of calreticulin in the ER retention of class 1 by the use of cells that over-express, under-express, or do not express calrecticulin, and 3) determine whether TAP, calrecticulin, or tapasin is responsible for the peptide-induced release of class 1 from ER retention. The assembly and surface expression of the class 1 molecule is blocked by several viral proteins. Knowledge of the mechanisms of viral interference in class 1 assembly can reveal a great deal about the normal processes of antigen presentation. One example of such a viral protein is the adenovirus E3-19K protein, which is weakly homologous to members of the immunoglobulin supergene family and so may have an as yet undiscovered cellular homologue. Whether E3-19K displaces peptide or any of the normal ER proteins that chaperone class 1 (calnexin, calreticulin, TAP, or tapasin) is not known. To resolve these issues, the final aim of this proposal is to determine whether the class 1 heavy chains that bind to E3-19K are peptide-occupied and if they have lost association with ER chaperones. In summary, these studies will yield new insights into the regulation of antigen presentation and will be helpful in the future design of rational approaches for clinical treatment of cancer and viral diseases.