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

细胞质域细胞在遇到另一个表面携带与MHC蛋白结合的肽抗原的细胞时被激活，这是免疫系统识别和清除体内外来物质过程的一部分。这种相互作用包括克隆型T细胞受体（TCR）亚基对mhc肽复合物的特异性识别，以及粘附分子与来自T细胞和抗原提呈细胞的其他细胞表面受体之间的抗原非依赖性相互作用。使用抗体或多价抗原在T细胞表面聚集TCR复合物可以诱导T细胞与抗原呈递细胞相互作用的过程，这表明TCR组分的聚集或聚集对于T细胞激活的起始很重要。TCR的胞质结构域γ， δ, ε，特别是ζ亚基负责将细胞外结合信号传递到T细胞。与其他由寡聚化激活的细胞表面受体系统不同，TCR细胞质结构域似乎不携带内在的或相关的酶活性。膜结合激酶和细胞质激酶在抗原接合时与TCR细胞质结构域相互作用，触发细胞质信号级联反应。尽管研究深入，但t细胞表面受体聚集导致细胞质信号传导的机制尚不清楚，是该领域的一个主要突出问题。在本研究中，将研究TCR zeta链细胞质结构域的结构和功能。具体来说，一个新发现的脂质结合活性将被表征。脂质结合诱导TCR zeta链细胞质域的结构改变，构象改变控制src-家族激酶在体外的可及性。这种脂质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。本研究的具体目标是确定诱导脂质依赖性构象变化的要求，对脂质结合结构进行详细的结构描述，研究全长zeta亚基蛋白背景下细胞质结构域的非国家变化，并评估体内信号传导过程中构象变化的重要性。这些目标将通过纯化受体细胞质结构域与各种洗涤剂和脂质复合物的各种光谱研究，以及体外和体内信号传导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.