MECHANISM AND CONSEQUENCES OF HLA-B 27 MISFOLDING

HLA-B27（B27）是一组直接参与脊柱关节病（SpAs）发病机制的主要组织相容性复合物I类蛋白，SpAs是影响轴向和外周关节的炎性关节炎性疾病。 虽然B27的作用是未知的，但B口袋，即所有B27亚型共有但该等位基因独特的肽结合沟区域，特别重要。 该区域显著影响肽的选择，导致B27可能呈递致关节炎肽的想法，尽管这仍然未经证实。 然而，我们的研究表明，B口袋也导致B27错误折叠。因此，我们假设B27可能不同于其他等位基因的方式是无关的肽结合特异性本身，了解这些差异可能有重要的后果，阐明SpAs的原因。 该提案旨在确定B27错误折叠的机制和后果。 在具体目标1中，我们将研究B口袋氨基酸、肽和β 2微球蛋白对B27折叠动力学和错误折叠的影响，以确定其机制。 在特定目标2中，我们将鉴定参与内质网（ER）中B27重链（HC）折叠的最早阶段的分子伴侣，并表征可能代表错误折叠中间体的高分子量HC复合物。 我们将确定分子伴侣过表达对折叠动力学和错误折叠的影响。 具体目标3将评估HLA-B27错误折叠的后果。 我们将测试的假设，一些错误折叠的高分子量HC逃脱ER和细胞表面上表达。 我们还将确定B27错误折叠信号是否导致NF-κ B激活和/或诱导伴侣蛋白合成的ER应激反应。 这些实验将表征B27和其他MHC I类等位基因之间的根本差异。 他们将深入了解这些差异的机制，它们如何与SpAs的发病机制相关，以及如何纠正它们。

HLA-B27 (B27) designates a group of major histocompatibility complex class I proteins directly involved in pathogenesis of spondyloarthropathies (SpAs), inflammatory arthritic diseases affecting both axial and peripheral joints. While the role of B27 is unknown, the B pocket, a region of the peptide binding groove common to all B27 subtypes yet unique to this allele, is particularly important. This region dramatically influences peptide selection, leading to the idea that B27 may present arthritogenic peptides, although this remains unproven. However, our studies indicate the B pocket also causes B27 to misfold. Thus, we hypothesize that B27 may differ from other alleles in ways that are unrelated to peptide binding specificity per se, and that understanding these differences may have important consequences for elucidating the cause of SpAs. This proposal is designed to determine the mechanism and consequences of B27 misfolding. In Specific Aim 1 we will examine the influence of B pocket amino acids, peptide, and beta2 microglobulin, on the folding kinetics and misfolding of B27 to determine the mechanism. In Specific Aim 2 we will identify molecular chaperones involved in the earliest stages of B27 heavy chain (HC) folding in the endoplasmic reticulum (ER), and characterize high molecular weight HC complexes that may represent misfolding intermediates. We will determine the influence of chaperone overexpression on folding kinetics and misfolding. Specific Aim 3 will assess consequences of HLA-B27 misfolding. We will test the hypothesis that some misfolded high molecular weight HC escape the ER and are expressed on the cell surface. We will also determine whether B27 misfolding signals an ER stress response resulting in NF-kappaB activation and/or induction of chaperone synthesis. These experiments will characterize fundamental differences between B27 and other MHC class I alleles. They will provide insights into the mechanisms responsible for these differences, how they may relate to the pathogenesis of SpAs, and how they may be corrected.