Mechanisms of beta2-microglubin in Autoimmune Diabetes

β2-微球蛋白在自身免疫性糖尿病中的作用机制

• 批准号: 7070052
• 负责人: STANLEY G NATHENSON
• 金额: $ 31.81万
• 依托单位: ALBERT EINSTEIN COLLEGE OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-09-02 至 2008-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7070052
• 关键词: MHC class I antigen; T cell receptor; X ray crystallography; autoantigens; autoimmune disorder; diabetes mellitus; electrospray ionization mass spectrometry; major histocompatibility complex; matrix assisted laser desorption ionization; protein denaturation; protein isoforms; protein structure; surface plasmon resonance; thermodynamics

DESCRIPTION (provided by applicant): Autoimmune diabetes in both humans and nonobese diabetic (NOD) mice results from T cell-mediated autoimmune destruction of insulin-producing pancreatic beta cells. Both class I major histocompatibility complex (MHC)-restricted and class II MHC-restricted T cells are involved. However, T cell receptors (TCRs) restricted to recognition of autoantigenic peptides presented by the trimeric class I molecule, consisting of MHC heavy chain, beta2-microglobulin (beta2m), and peptide, are absolutely required for the initiation of disease in the NOD mouse. Autoimmune diabetes is a polygenic disease, with particular MHC haplotypes providing the primary genetic component of susceptibility in both humans and NOD mice. Recently, (beta2m) was identified as a diabetes susceptibility gene in NOD mice, the first such gene to be identified that maps outside of the MHC region, lying within the Idd13 locus on Chromosome 2. Two beta2m alleles are widespread throughout the common laboratory mouse strains. When the a2ma allele found in NOD mice is replaced by the a2mb allele, development of diabetes is prevented. The amino acid sequence difference between these two allelic proteins resides in a single exchange of Asp ("a" isoform) for Ala ("b" isoform) at position 85. A number of previous serological and T cell recognition studies, using a variety of MHC allelic products and a2m proteins from different species, have suggested significant conformational flexibility of the class I molecule dependent on the particular beta2m present in the complex. Based on these findings, it can be hypothesized that class I MHC molecules containing beta2ma might exhibit an altered conformation as compared to those containing beta2mb. Such changes could exert effects on both selection of autoreactive T cells and presentation of autoantigenic peptides. The overall goal of this proposal is to test this hypothesis by systematically examining the structural, biochemical, and biological properties of disease-relevant MHC-peptide complexes containing the two beta2m isoforms. Four Specific Aims are proposed: (1) Structural, thermodynamic, and dynamic characterization of the isolated allelic beta2m proteins, using X-ray diffraction analysis, chemical and thermal denaturation, and amide proton exchange; (2) Similar characterization of the diabetes-related MHC/peptide complexes, including measurements of beta2m and peptide exchange rates; (3) Structural, biochemical, and dynamic characterization of the diabetes-related TCR/MHC-peptide complexes containing the two isoforms Of beta2m, using X ray diffraction analysis, amide proton exchange, and surface plasmon resonance; and (4) Cellular analysis of T Cell recognition and TCR dwell time using MHC-peptide complexes containing the two different beta2m isoforms. Completion of the proposed Aims should allow identification of the molecular and atomic determinants that result in beta2m-dependent susceptibility or protection against disease.

描述（由申请人提供）：人类和非肥胖糖尿病（NOD）小鼠的自身免疫性糖尿病是由于T细胞介导的自身免疫性销毁胰岛素产生的胰腺β细胞。 I类主要的组织相容性复合物（MHC）限制性和II类MHC限制的T细胞都涉及。然而，限制了由三聚体I类分子呈现的自身抗原肽的T细胞受体（TCR），由MHC重链，Beta2-微球蛋白（BETA2M）和肽组成，是NOD小鼠疾病启动疾病的绝对必需的。自身免疫性糖尿病是一种多基因疾病，特定的MHC单倍型可提供人和NOD小鼠易感性的主要遗传成分。最近，（beta2m）被确定为NOD小鼠中的糖尿病敏感性基因，这是第一个被鉴定出的基因，即MHC区域以外的地图，位于MHC区域以外的MAP，位于2染色体上的IDD13基因座内。两个BetA2M等位基因在整个普通实验室小鼠菌株中广泛存在。当在NOD小鼠中发现的A2MA等位基因被A2MB等位基因取代时，可以防止糖尿病的发育。 The amino acid sequence difference between these two allelic proteins resides in a single exchange of Asp ("a" isoform) for Ala ("b" isoform) at position 85. A number of previous serological and T cell recognition studies, using a variety of MHC allelic products and a2m proteins from different species, have suggested significant conformational flexibility of the class I molecule dependent on the particular beta2m present in the complex.基于这些发现，可以假设与含有beta2mb的I类MHC分子可能显示出改变的构象。这种变化可能对自身反应性T细胞的选择和自身抗原肽的呈现产生影响。该提案的总体目标是通过系统地检查含有两个β2M同工型的疾病相关的MHC肽复合物的结构，生化和生物学特性来检验这一假设。提出了四个具体目的：（1）使用X射线衍射分析，化学和热变性以及酰胺质子交换，分离的等位基因beta2m蛋白的结构，热力学和动态表征； （2）与糖尿病相关的MHC/肽复合物的相似表征，包括测量BetA2M和肽汇率； （3）使用X射线衍射分析，酰胺质子质子交换和表面等离子体共振，糖尿病相关的TCR/MHC肽络合物的结构，生化和动态表征； （4）使用包含两个不同beta2m同工型的MHC肽复合物对T细胞识别和TCR停留时间的细胞分析。所提出的目标的完成应允许识别导致β2M依赖性敏感性或对疾病的保护的分子和原子决定因素。