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的多肽的呈递 转化为T淋巴细胞。这些多肽必须与细胞表面1类结合。 主要组织相容性复合体(MHC)重链被识别 淋巴细胞。1类MHC重链、轻链的组装 称为β2-微球蛋白(β2-m)和多肽进入 异三聚体，完整的I类MHC分子存在于内质中 网状结构(ER)。在1类组装过程中，内质网驻留蛋白，如 钙网蛋白，与抗原处理相关的转运体(TAP)， Tapasin与无肽类1重链/β2-m相互作用。这个 这项研究的长期目标是了解其机制和 免疫反应在多肽负荷和免疫调节水平的调节 1类MHC分子的组装。中描述的前三项研究 该赠款提案将定义每个ER的不同角色 蛋白质在多肽负载前保留1类和将 探索它们与第一类分子相互作用的本质。 具体地说，这些研究将1)确定1)类的重要性 重链糖基化与钙网蛋白的α3结构域 与1，2类的关联)确定钙网织蛋白在内质网中的作用 通过使用过度表达、低表达、 或不表达钙调蛋白，以及3)确定是否TAP， 钙调蛋白或Tapasin负责多肽诱导的释放 来自急诊室留存的1级。组件的装配和表面表达 第一类分子被几种病毒蛋白阻断。了解以下内容 1类组装中病毒干扰的机制可以揭示一个很大的 讨论抗原呈递的正常过程。其中一个例子是 这样的病毒蛋白就是腺病毒E3-19K蛋白，它的强度很弱 与免疫球蛋白超基因家族的成员同源，因此可能 有一种尚未被发现的细胞同源基因。E3-19K是否会取代 多肽或任何正常的内质网蛋白，分子伴侣1类(Calnexin， 钙网蛋白、TAP或TAPASIN)是未知的。为了解决这些问题， 这项提案的最终目标是确定1级重型 与E3-19K结合的链是被肽占据的，如果它们已经丢失 与急诊室监护人联系在一起。总而言之，这些研究将产生新的 对抗原呈递的调节的见解将是有帮助的 在未来设计合理的临床治疗方法 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.