Quality Control of MHC Class I Restricted Antigen Processing

项目摘要 MHC-I类限制性抗原的处理对于产生CD8 T细胞反应是必不可少的。它必须发挥作用 正确用于有效识别病原体的免疫，而异常可导致自身免疫。这个 这项建议的总体目标是了解管理MHC I类的质量控制程序- 在胞浆中翻译的常规抗原和外源抗原的限制性抗原加工 由交叉提呈细胞内化的抗原。后一种过程的特点尤其糟糕，但 它是启动CD8 T细胞反应所必需的。我们希望了解这两个不同之处 加工机制驱动基本上相同的MHC-I多肽复合体的组装。一个 内质网(ER)中的关键质量控制过程仍然不清楚的是 UDP-葡萄糖糖蛋白转移酶(UGT1)的活性，它能产生正确的 单糖化的多糖结构，允许MHC-I分子与MHC-I保持相互作用 通过凝集素伴侣钙网织蛋白的多肽负载复合体(PLC)，促进Tapasin介导 多肽交换。这促进了MHC-I与高密度脂蛋白多肽的复合体的细胞表达 亲和力。我们将检验这样的假设，即MHC-I肽结合域的结构灵活性是 作为UGT1的识别信号。第二种成分，在内质网和内质网中都有 途径，是TAPASIN的同源物TAPBPR。在体外，TAPBPR可通过MHC-I诱导多肽交换 在PLC之外的分子，它也被证明与UGT1相互作用。第二个主要目标是 为了确定TAPBPR是否通过MHC I类分子在完整细胞中介导肽交换， 这是否可以同时发生在内质网和交叉呈递细胞的吞噬小体中，以及是否在 TAPBPR与UGT1焦点的同时相互作用 UGT1对与低亲和力多肽相关的MHC-I分子的酶活性 它们用来交换最佳的多肽。最终目标是确定交叉呈现完整抗原的方式。 遇到蛋白酶体，它对传统的MHC-I抗原处理和交叉反应都是必不可少的 演示文稿。我们有证据表明，这种相互作用发生在附近，而且可能在内部， 交叉呈递细胞的吞噬小体。在两个细胞中调节这种相互作用的机制 将对生物和生化水平进行调查。

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.