Quality Control of MHC Class I Restricted Antigen Processing

项目摘要 MHC I类限制性抗原加工对于产生CD 8 + T细胞应答至关重要。它必须发挥作用 正确的病原体的有效免疫识别，畸变可导致自身免疫。的 本提案的总体目标是了解调节I类MHC的质量控制过程- 在细胞质中翻译的常规抗原的限制性抗原加工，以及外源性抗原的限制性抗原加工。 由交叉呈递细胞内化的抗原。后一个过程的特征特别差，然而， 它对于引发CD 8 + T细胞应答是必需的。我们希望了解这两个不同的 加工机制驱动基本上相同的MHC-I肽复合物库的组装。一 内质网（ER）中一个关键的质量控制过程仍然不清楚， UDP-葡萄糖糖蛋白转移酶（UGT 1），它产生正确的 单葡糖基化聚糖结构，其允许MHC-I分子维持与MHC-I分子的相互作用。 肽装载复合物（PLC）通过凝集素伴侣钙网蛋白，促进tapasin介导的 肽交换这促进了细胞表达MHC-I与高表达肽的复合物。 亲和力我们将检验MHC-I肽结合域的结构灵活性 作为UGT 1的识别信号。第二种成分存在于内质网和内吞细胞中， 这条通路的另一个重要组成部分是Tapasin同系物TAPBPR。TAPBPR在体外可诱导MHC-I的肽交换 分子外的PLC，它也已被证明与UGT 1相互作用。第二个主要目标是 为了确定TAPBPR是否介导完整细胞中MHC I类分子的肽交换， 这是否可以发生在ER和交叉呈递细胞的吞噬体中，以及是否在 无论是这些细胞内区室，TAPBPR与UGT 1的同时相互作用集中在 UGT 1对与低亲和力肽相关的MHC-I分子的酶促活性， 它们交换最佳肽。最终的目标是确定如何交叉呈递完整的抗原 遇到蛋白酶体，这是必不可少的常规MHC-I抗原加工和交叉， 演示文稿.我们有证据表明，这种相互作用发生在近端，可能在内部， 交叉呈递细胞的吞噬体。调节这种相互作用的机制既在细胞中， 生物和生化水平进行研究。

Project Summary MHC class I-restricted antigen processing is essential for making CD8+ T cell responses. It must function correctly for effective immune recognition of pathogens, and aberrations can lead to autoimmunity. The overall aim of this proposal is to understand the quality control processes regulating MHC class I- restricted antigen processing of conventional antigens, translated in the cytosol, and of exogenous antigens internalized by cross-presenting cells. The latter process is particularly poorly characterized, yet it is essential for priming CD8+ T cell responses. We wish to understand how these two different processing mechanisms drive the assembly of essentially the same pool of MHC-I peptide complexes. A critical quality control process in the endoplasmic reticulum (ER) that remains ill understood is the action of the enzyme UDP-glucose glycoprotein transferase (UGT1), which produces the correct monoglucosylated glycan structure that allows MHC-I molecules to maintain an interaction with the Peptide Loading Complex (PLC) via the lectin chaperone calreticulin, facilitating tapasin-mediated peptide exchange. This promotes the expression by the cell of complexes of MHC-I with peptides of high affinity. We will test the hypothesis that structural flexibility in the MHC-I peptide binding domain serves as a recognition signal for UGT1. A second component, which is found in both the ER and the endocytic pathway, is the tapasin homologue TAPBPR. In vitro, TAPBPR can induce peptide exchange by MHC-I molecules outside of the PLC, and it has also been shown to interact with UGT1. A second major goal is to determine whether TAPBPR mediates peptide exchange by MHC class I molecules in intact cells, whether this can occur both in the ER and the phagosomes of cross-presenting cells, and whether in either of these intracellular compartments the simultaneous interaction of TAPBPR with UGT1 focuses the enzymatic activity of UGT1 onto MHC-I molecules associated with low affinity peptides, facilitating their exchange for optimal peptides. The final goal is to determine how cross-presented intact antigens encounter proteasomes, which are essential for both conventional MHC-I antigen processing and cross- presentation. We have evidence that this interaction occurs proximal to, and probably within, phagosomes of cross-presenting cells. The mechanisms that regulate this interaction at both the cell biological and biochemical level will be investigated.