Structure and Function of the T-cell Receptor Zeta Chain Cytoplasmic Domain

T细胞受体Zeta链细胞质结构域的结构和功能T细胞与另一个细胞相遇时被激活，该细胞表面携带与MHC蛋白结合的多肽抗原，这是免疫系统识别和清除体内异物的过程的一部分。这种相互作用涉及克隆型T细胞受体(TCR)亚基对MHC-肽复合体的特异性识别，以及T细胞和抗原提呈细胞中的黏附分子与其他细胞表面受体之间的抗原非依赖性相互作用。用抗体或多价抗原在T细胞表面聚集TCR复合体可以诱导T细胞与抗原提呈细胞相互作用的过程，这表明TCR组分的聚集或聚集对于启动T细胞激活是重要的。TCRγ、β、epsilon，特别是Zeta亚基的细胞质结构域负责将细胞外结合信号传递到T细胞。与其他由齐聚激活的细胞表面受体系统不同，TCR胞浆结构域似乎不携带固有的或相关的酶活性。膜结合蛋白和胞浆蛋白激酶在抗原结合时与TCR胞浆结构域相互作用，触发胞质信号级联反应。尽管进行了大量的研究，但T细胞表面受体聚集导致胞质信号转导的机制尚不清楚，是该领域的一个主要突出问题。在拟议的研究中，将研究TCR Zeta链细胞质结构域的结构和功能。具体地说，将描述一种新发现的脂结合活性。脂质结合导致TCR Zeta链胞质结构域的结构变化，而这种一致性变化控制着体外对src家族激酶的可及性。这种脂结合活性和构象变化在T细胞激活途径中的可能作用将被研究。具体的目标或拟议的研究是为了确定诱导脂质依赖的构象变化的要求，产生脂结合结构的详细结构描述，在全长Zeta亚单位蛋白的背景下研究细胞质结构域的构象变化，并评估构象变化在体内信号传递过程中的重要性。这些目标将通过各种光谱学研究纯化的受体胞质结构域与各种洗涤剂和脂质的复合体，以及体外和体内信号传递过程的生化分析来实现。

Structure and Function of the T-cell Receptor Zeta Chain Cytoplasmic DomainT cells are activated upon encounter with another cell that carries on its surface a peptide antigen bound to an MHC protein, as part of the process by which foreign material in the body is recognized and cleared by the immune system. The interaction involves specific recognition of the MHC-peptide complexes by clonotypic T-cell receptor (TCR) subunits, as well as antigen-independent interactions between adhesion molecules and other cell surface receptors from the T cell and the antigen presenting cell. Clustering of TCR complexes at the T-cell surface using antibodies or multivalent antigens can induce T cell processes characteristic of interaction with an antigen-presenting cell, suggesting that clustering or aggregation of TCR components isimportant for initiation of T-cell activation. Cytoplasmic domains of the TCR gamma, delta, epsilon, and particularly zeta subunits are responsible for transmitting extracellular binding signals into the T cell. Unlike other cell surface receptor systems activated by oligomerization, TCR cytoplasmic domains do not appear to carry intrinsic or associated enzymatic activities. Membrane-bound and cytoplasmic kinases interact with TCR cytoplasmic domains upon antigen engagement, triggering cytoplasmic signaling cascades. Despite intensive study, the mechanism by which clustering of T-cell surface receptors can leads to cytoplasmic signaling is not clear and is a major outstanding problem in the field. In the proposed research, the structure and function of the TCR zeta chain cytoplasmic domain will be investigated. Specifically, a newly discovered lipid-binding activity will be characterized. Lipid binding induces a structural alteration in the TCR zeta chain cytoplasmic domain, and the conforynational change controls accessibility to src- family kinases in vitro. Possible roles of this lipid binding activity and conformational change in the T-cell activation pathway will be investigated. The specific objectives or the proposed research are to determine the requirements for inducing the lipid-dependent conforrnational change, to produce a detailed structural description of the lipid-bound structure, to investigate the confon-national change of cytoplasmic domain in the context of the full-length zeta subunit protein, and to evaluate the importance of the conformational change in signaling processes in vivo. These objectives will be pursued through a variety of spectroscopic studies of purified receptor cytoplasmic domains in complex with various detergents and lipids, and biochemical assays of signaling processes in vitro and in vivo.