Coincident Antigen Processing Pathways Feed M1 and M2 MHC Class II Conformers

一致抗原加工途径喂养 M1 和 M2 MHC II 类适形者

• 批准号: 10303345
• 负责人: James R Drake
• 金额: $ 24.45万
• 依托单位: ALBANY MEDICAL COLLEGE
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-06-07 至 2023-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10303345
• 关键词: Antigen Presentation; Antigen Targeting; Antigen-Presenting Cells; Antigens; Attenuated; Autoimmunity; B-Cell Activation; B-Cell Antigen Receptor; B-Lymphocytes; Biochemical; Biological; CD4 Positive T Lymphocytes; Charge; Complex; Data; Dimerization; Dissociation; Dose; Endosomes; Exhibits; Fluorescence Resonance Energy Transfer; Foundations; Goals; Haptens; Histocompatibility Antigens Class II; Immune response; Immune system; Immunologics; Interphase Cell; Kinetics; Label; Laboratories; Lead; Liquid substance; MHC Class II Genes; Mainstreaming; Mass Spectrum Analysis; Mediating; Modeling; Molecular; Molecular Conformation; Molecular Genetics; Monoclonal Antibodies; Pathway interactions; Peptide Hydrolases; Peptide/MHC Complex; Peptides; Phase; Physiologic pulse; Process; Property; Proteomics; Publishing; Receptor Signaling; Reporting; Research Proposals; Rest; Role; Signal Transduction; Site; Source; Structure; T cell response; T-Cell Activation; Testing; Therapeutic; Transmembrane Domain; Vaccines; Work; antigen binding; antigen processing; base; comparative; conformer; genetic approach; immune activation; in vivo; insight; novel; novel strategies; novel therapeutic intervention; pathogen; peptide B; receptor binding; response; therapeutic target

Summary: The current mainstream view of exogenous antigen processing postulates a pool of proteases processing exogenous antigen within the endosome, with structurally homogeneous MHC class II (MHCII) molecules randomly capturing resultant peptides. However, this view is an oversimplification on at least two levels. First, work from multiple laboratories including our own has shown that MHCII molecules exist in two distinct conformational states based on alternative pairing of transmembrane domain GxxxG dimerization motifs (i.e., M1 and M2 paired MHCII) and that these two MHCII conformers have distinct biological and immunological properties. Second, we have reported that in B lymphocytes M1 and M2 paired MHCII molecules are selectively loaded with peptide derived from different pools of exogenous antigen. M1 MHCII is loaded with peptide derived from B cell receptor (BCR)-bound cognate antigen, whereas peptide derived from non-cognate antigen is loaded onto both M1 and M2 MHCII. New preliminary data also reveals that ~50% of the peptides bound to each conformer are unique to that set of molecules. As engagement of M1 and M2 peptide-MHCII drive different levels of B and T cell activation, differential MHCII conformer peptide loading will impact the focus, strength and quality of an immune response. This framework leads to the hypothesis that within an antigen presenting cells, there are two coincident but distinct pathways of exogenous antigen processing that leads to selective peptide loading onto M1 versus M2 paired MHCII molecules. The goal of this proposal is to define the two pathways of exogenous antigen processing that feed the two MHCII conformers. This goal will be attained by completing two Specific Aims. The objective of the first aim is to define/analyze the peptidomes of M1 and M2 paired MHCII isolated from both resting and antigen-pulsed B cells. This information will point to the subcellular sites of processing for M1 vs. M2 MHCII-bound peptides by defining the pool of source antigens for each MHCII conformer. The results will also reveal the impact of antigen targeting as well as BCR signaling-induced changes in the antigen processing pathway on the M1 and M2 MHCII peptidomes. The objectives of the second aim are to; 1) take a molecular genetics approach to define the structure and dynamics of the MHCII peptide loading complex (PLC) that selectively charges peptides from BCR-bound cognate antigen onto M1 MHCII and 2) to use a discovery- style approach to identify and characterize new PLC components. The potential impact of these studies is many-fold. For example, results will reveal how the form of antigen (e.g., vaccine) provided to the immune system would impact the levels of M1 and M2 MHCII peptide loading and thus the level of subsequent immune activation. Therapeutically, the ability to selectively interfere with M1 or M2 MHCII-restricted antigen presentation may lead to new therapeutic approaches to selectively control/block autoimmunity, while leaving the immune response to pathogens comparatively unimpaired.

概括： 当前外源抗原加工的主流观点假定蛋白酶加工池 内体中的外源抗原，具有结构均质的 MHC II 类 (MHCII) 分子 随机捕获所得肽。然而，这种观点至少在两个层面上过于简单化。第一的， 包括我们自己实验室在内的多个实验室的工作表明，MHCII 分子存在于两种不同的形式中： 基于跨膜结构域 GxxxG 二聚化基序的替代配对的构象状态（即， M1 和 M2 配对 MHCII) 并且这两个 MHCII 构象异构体具有不同的生物学和免疫学特性 特性。其次，我们报道了 B 淋巴细胞中 M1 和 M2 配对的 MHCII 分子 选择性地装载源自不同外源抗原库的肽。 M1 MHCII 装载 源自 B 细胞受体 (BCR) 结合同源抗原的肽，而源自非同源抗原的肽 抗原被加载到 M1 和 M2 MHCII 上。新的初步数据还表明，约 50% 的肽 与每个构象异构体结合的分子对于该组分子来说是独特的。作为 M1 和 M2 肽-MHCII 的结合 驱动不同水平的 B 和 T 细胞激活，不同的 MHCII 构象肽负载将影响 免疫反应的焦点、强度和质量。 这个框架导致了这样的假设：在抗原呈递细胞内，有两个一致的 但外源抗原加工的不同途径导致选择性肽加载到 M1 上 M2 配对的 MHCII 分子。该提案的目标是定义外源抗原的两条途径 提供两个 MHCII 构象异构体的加工。这一目标将通过完成两个具体目标来实现。 第一个目标是定义/分析从 MHCII 中分离出的 M1 和 M2 配对的 MHCII 的肽组。 静息 B 细胞和抗原脉冲 B 细胞。该信息将指向 M1 的亚细胞加工位点 通过定义每个 MHCII 构象异构体的源抗原池来比较 M2 MHCII 结合肽。结果 还将揭示抗原靶向的影响以及 BCR 信号诱导的抗原变化 M1 和 M2 MHCII 肽组上的加工途径。第二个目标的目标是： 1）取一个 分子遗传学方法定义 MHCII 肽负载复合物 (PLC) 的结构和动力学 选择性地将来自 BCR 结合同源抗原的肽装载到 M1 MHCII 上，并且 2) 使用一项发现- 识别和表征新 PLC 组件的风格方法。 这些研究的潜在影响是多方面的。例如，结果将揭示抗原的形式如何 提供给免疫系统的（例如疫苗）会影响 M1 和 M2 MHCII 肽负载的水平 从而影响随后的免疫激活水平。治疗上，选择性干扰 M1 的能力 或 M2 MHCII 限制性抗原呈递可能会导致新的治疗方法选择性地 控制/阻止自身免疫，同时使对病原体的免疫反应相对不受损害。