Regulation of CD28 Signaling in T cells by Cytoplasmic Domain Membrane Binding

描述（由申请人提供）：T细胞受体（TCR）是通过在基因组水平上重排单个细胞中的V、D和J片段而产生的。因此，TCR库共同地可以识别任何抗原。由于这种随机重排过程，T细胞缺乏区分自身抗原和病原体相关抗原的能力。相反，T细胞必须被先天免疫抗原呈递细胞（APC）激活，并被指示分化为效应细胞。这种激活信号需要TCR的抗原依赖性刺激和通过CD 28的共刺激，CD 28是在所有原始T细胞和记忆T细胞亚群上组成性表达的膜受体。与通过识别病原体相关分子而激活的APC上表达的其配体B7.1（CD 80）或B7.2（CD 86）结合，提供与TCR信号传导协同作用并促进细胞存活、增殖和效应器功能的共刺激信号。 TCR或CD 28的配体接合导致受体触发和信号转导的机制仍然未知;对于任何基于磷酸酪氨酸的免疫受体，受体触发的一般机制仍有待阐明。相反，防止CD 28和其他基于磷酸酪氨酸的受体的自发和异常信号传导的机制也知之甚少。使用荧光共振能量转移（FRET）显微镜、生物化学和细胞测定的组合来评估T细胞信号传导和功能，以及多发性硬化症的体内模型（小鼠实验性自身免疫性脑脊髓炎），本研究将检查：a）CD 28胞质结构域（CD 28 CD）与质膜内小叶的结合; B）这种关联对信号传导和T细胞功能调节的结果;和c）在生理条件下CD 28 CD从质膜释放的机制。对CD 28调节机制的理解将提供对更普遍的受体触发模型的深入了解。 公共卫生相关性：先天免疫系统的抗原呈递细胞通过CD 28提供给T细胞的共刺激是几种动物模型中自身免疫发作所需的。该研究项目的目标是提高我们对共刺激信号如何产生的理解，这反过来又可以提高我们对自身免疫性疾病（如1型糖尿病，多发性硬化症和类风湿性关节炎）启动的理解。

DESCRIPTION (provided by applicant): The T cell receptor (TCR) is generated by rearrangement of V, D and J segments in individual cells at the genomic level. Therefore, the TCR repertoire collectively can recognize any antigen. As a consequence of this random rearrangement process, T cells lack the ability to discriminate between self antigens and pathogen- associated antigens. Instead, T cells must be activated by innate immune antigen presenting cells (APCs) and instructed to differentiate into effector cells. This activating signal requires antigen-dependent stimulation of the TCR and costimulation through CD28, which is a membrane receptor constitutively expressed on all naove T cells and subsets of memory T cells. Binding to its ligands B7.1 (CD80) or B7.2 (CD86) expressed on APCs activated by recognition of pathogen-associated molecules delivers a costimulatory signal that synergizes with TCR signaling and promotes cell survival, proliferation and effector functions. The mechanism by which ligand engagement by TCR or CD28 leads to receptor triggering and signal transduction remains unknown; a general mechanism of receptor triggering remains to be elucidated for any phosphotyrosine-based immune receptor. Conversely, the mechanism preventing spontaneous and aberrant signaling of CD28 and other phosphotyrosine-based receptors is also poorly understood. Using a combination of fluorescence resonance energy transfer (FRET) microscopy, biochemical and cellular assays to assess T cell signaling and function, and an in vivo model of multiple sclerosis (murine experimental autoimmune encephalomyelitis), this research will examine: a) association of CD28 cytoplasmic domain (CD28CD) with the inner leaflet of the plasma membrane; b) the consequences of this association for regulation of signaling and T cell function; and c) the mechanism by which CD28CD is released from the plasma membrane under physiological conditions. Mechanistic understanding of CD28 regulation would provide insight into a more generalizable model of receptor triggering. PUBLIC HEALTH RELEVANCE: Co-stimulation provided to T cells via CD28 by antigen presenting cells of the innate immune system is required for the onset of autoimmunity in several animals models. The goal of this research project is to improve our understanding of how co-stimulatory signals are generated, which could in turn improve our understanding of the initiation of autoimmune disorders such as type 1 diabetes, multiple sclerosis and rheumatoid arthritis.