Novel mechanisms of TCR quality control

描述（由申请人提供）：T细胞受体对适应性免疫系统的主要功能至关重要，是最复杂的细胞表面受体之一。它由八条多肽链组成，这些多肽链必须以适当的化学计量组装在ER中以执行其重要功能。因此，它的组装对ER质量控制机构来说是一项艰巨的任务。尽管存在大量关于TCR的组装和质量控制的文献，但这些努力主要集中在单个链的不寻常的跨膜结构域上。这些具有带电残基，当未配对时，加速TCR链的降解，并被认为驱动组装。然而，该假定的“整体膜质量控制”步骤的基础尚未阐明。此外，很少有人注意到这种受体的内腔部分的可能作用，这可能是由ER的已知质量控制机制仔细检查的区域。为了弥补这一不足，我们建议结合联合收割机生物物理和细胞为基础的研究，以获得高分辨率的结构和动力学数据的折叠和组装的TCR，可以与检查点在细胞中。我们从这些方法中获得的初步数据已经揭示了TCR γ链的两个意想不到的特征。我们发现，它的恒定结构域是非结构化的，在没有协会与<$-链，其跨膜区不整合到ER膜单独表达时。这两个特征很可能在受体组装的质量控制中提供检查点。这些初步的见解将扩大，以获得一个综合的观点ER机制，帮助和监测TCR的生物合成，只允许正确组装的受体在细胞表面上表达。

DESCRIPTION (provided by applicant): The ¿¿T-cell receptor is essential for major functions of the adaptive immune system and is one of the most complex cell surface receptors. It is composed of eight polypeptide chains that must be assembled in the ER in the proper stoichiometry for it to perform its vital functions. As such, its assembly poses a formidable task for the ER quality control machinery. Although a large body of literature exists on the assembly and quality control of the ¿¿TCR, these efforts have focused primarily on the unusual transmembrane domains of the individual chains. These possess charged residues that, when unpaired, accelerate degradation of the ¿¿TCR chains and are believed to drive assembly. However, the basis of this presumed "integral membrane quality control" step has not been elucidated. Furthermore, very little attention has been directed to possible roles for the lumenal portions of this receptor, which are likely to be the regions scrutinized by the known quality control machinery of the ER. To remedy this deficiency, we propose to combine biophysical and cell based studies to obtain high resolution structural and kinetic data on the folding and assembly of the ¿¿TCR that can be correlated with checkpoints in the cell. Our preliminary data obtained from these approaches have already revealed two unanticipated features of the TCR ¿-chain. We find that its constant domain is unstructured in the absence of association with the ¿- chain and that its transmembrane region is not integrated into the ER membrane when expressed alone. These two features are very likely to provide checkpoints in the quality control of receptor assembly. These preliminary insights will be expanded in order to obtain an integrated view of the ER mechanisms that aid and monitor TCR biosynthesis allowing only properly assembled receptors to be expressed on the cell surface.