Molecular mechanisms of HLA-DM mediated peptide exchange

HLA-DM介导的肽交换的分子机制

• 批准号: 8882582
• 负责人: Hao Wu
• 金额: $ 43.34万
• 依托单位: DANA-FARBER CANCER INST
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-08-01 至 2017-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8882582
• 关键词: Affect; Affinity; Animal Model; Antigen Presentation; Antigen Presentation Pathway; Antigens; Autoantigens; Autoimmune Diseases; Autoimmune Process; Autoimmunity; Binding; CD4 Positive T Lymphocytes; CLIP peptide; Cell surface; Complex; Crystallization; DR1 gene; Data; Development; Disease; Disease susceptibility; Dissociation; Enzymes; Event; Excision; Genetic Polymorphism; Goals; HLA-DQ6; HLA-DQ8 antigen; HLA-DR Antigens; Half-Life; Health; Histocompatibility Antigens Class II; Human; Influenza; Insulin-Dependent Diabetes Mellitus; Life; Link; MHC Class II Genes; Major Histocompatibility Complex; Measurement; Measures; Mediating; Modeling; Molecular; Motion; Multiple Sclerosis; Mutation; Pathogenesis; Peptides; Phenylalanine; Play; Positioning Attribute; Predisposition; Process; Production; Property; Proteins; Resolution; Rheumatoid Arthritis; Role; Series; Side; Site; Specificity; Staphylococcus aureus; Structural Models; Structure; Surface Plasmon Resonance; T-Lymphocyte; Techniques; Testing; Tryptophan; Tyrosine; base; hazard; hemagglutinin (306-318); insight; invariant chain; novel; novel strategies; prevent; sortase; tool

DESCRIPTION (provided by applicant): The Major Histocompatibility Complex (MHC) represents the most important susceptibility locus for many common human autoimmune diseases, including type 1 diabetes, rheumatoid arthritis and multiple sclerosis, indicating that antigen presentation to CD4 T cells represents an important step in their pathogenesis. HLA-DM (DM) plays a central role in the MHC class II (MHCII) antigen presentation pathway: it induces dissociation of the invariant chain-derived CLIP peptide and edits the peptide repertoire, favoring presentation of high-affinity peptides. The central goals of this project are to define th mechanism of DM action at a structural level and to advance our understanding of self-antigen presentation in autoimmune diseases. Preliminary studies have shown that the interaction of DM and HLA-DR (DR) molecules is controlled by the occupancy state of the DR peptide binding groove. We found that DM cannot bind to DR proteins when the peptide binding groove is fully occupied by peptides. Rather, DM binds to an unstable transition state of DR proteins in which the peptide N-terminus has partially dissociated from the groove. We utilized this insight to develop a strategy for crystallization of the complex of DM bound to DR1. Aim 1 Since submission of the original proposal, we have been able to determine the crystal structure of the DR1-DM complex at a resolution of 2.6Å. The structure suggests a novel mechanism for rapid selection of high-affinity peptides (also referred to as 'editing'). In the DM-bound state, three D residues have moved into a critical part of the groove (P1 pocket and P2 site), rendering it initially inaccessible to peptides. Peptides need to compete for access to these sites, and this energetic barrier drives selection of peptides with the highest affinities. We have also recently developed a novel approach to measure rapid binding of peptides to empty DR1-DM complexes. This technique will now be used to define critical mechanistic steps in editing of the peptide repertoire by DM. Aim 2 is based on novel observations from the DR1-DM structure. HLA-DQ8 (DQ8) confers susceptibility to type 1 diabetes while HLA-DQ6 (DQ6) induces dominant protection. The DR1-DM structure shows that a substantial number of residues located at the DR1-DM interface are polymorphic in DQ8 and DQ6. Furthermore, preliminary data show substantial differences in the peptide binding properties of DQ8 and DQ6. We will use a series of functional approaches to dissect the impact of these DQ polymorphisms on peptide presentation by DQ8 and DQ6. Also, the novel strategy that enabled crystallization of the DR1-DM complex will be used for crystallization trials of a DQ-DM complex. We anticipate that these studies will have a significant impact on our understanding of DM function and MHCII antigen presentation in autoimmune diseases.

描述（由申请人提供）：主要组织相容性复合物（MHC）代表了许多常见人类自身免疫性疾病（包括1型糖尿病、类风湿性关节炎和多发性硬化症）的最重要易感性位点，表明抗原呈递至CD 4 T细胞代表了其发病机制中的重要步骤。HLA-DM（DM）在MHC II类（MHCII）抗原呈递途径中起着核心作用：它诱导恒定链衍生的CLIP肽的解离并编辑肽库，有利于高亲和力肽的呈递。该项目的中心目标是在结构水平上确定DM作用的机制，并促进我们对自身免疫性疾病中自身抗原呈递的理解。初步研究表明，DM与HLA-DR（DR）分子的相互作用受DR肽结合沟的占据状态控制。我们发现，当肽结合沟被肽完全占据时，DM不能与DR蛋白结合。相反，DM结合到DR蛋白的不稳定过渡状态，其中肽N-末端已部分从沟解离。我们利用这一洞察力，开发了一种策略，结合DR 1的DM复合物的结晶。目的1自提交原始提案以来，我们已经能够以2.6 μ m的分辨率确定DR 1-DM复合物的晶体结构。该结构表明了快速选择高亲和力肽的新机制（也称为“编辑”）。在DM结合状态下，三个D残基已经移动到沟的关键部分（P1口袋和P2位点），使其最初无法接近肽。肽需要竞争进入这些位点，这种能量屏障驱动选择具有最高亲和力的肽。我们最近还开发了一种新的方法来测量肽与空DR 1-DM复合物的快速结合。该技术现在将用于定义DM编辑肽库的关键机制步骤。目的2是基于对DR 1-DM结构的新观察。HLA-DQ 8（DQ 8）赋予1型糖尿病的易感性，而HLA-DQ 6（DQ 6）诱导显性保护作用。DR 1-DM结构表明，在DQ 8和DQ 6中，位于DR 1-DM界面处的大量残基是多态的。此外，初步数据显示DQ 8和DQ 6的肽结合性质存在显著差异。我们将使用一系列的功能方法来剖析这些DQ多态性对DQ 8和DQ 6的肽呈递的影响。此外，能够使DR 1-DM复合物结晶的新策略将用于DQ-DM复合物的结晶试验。我们预期这些研究将对我们理解自身免疫性疾病中DM功能和MHCII抗原呈递产生重大影响。