Novel mechanisms of TCR quality control

描述(申请人提供)：T细胞受体对适应性免疫系统的主要功能是必不可少的，是最复杂的细胞表面受体之一。它由八条多肽链组成，必须在内质网中以适当的化学计量比组装，才能发挥其重要功能。因此，它的组装对ER质量控制机构提出了一项艰巨的任务。尽管有大量关于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域上。它们含有带电残基，当没有配对时，会加速TCR链的降解，并被认为可以驱动组装。然而，这一假定的“整体膜质量控制”步骤的基础还没有被阐明。此外，很少有人注意到这种受体的管腔部分的可能作用，这些部分很可能是已知的内质网质量控制机制仔细检查的区域。为了弥补这一不足，我们建议将生物物理学和基于细胞的研究相结合，以获得与细胞中检查点相关的TCR折叠和组装的高分辨率结构和动力学数据。我们从这些方法获得的初步数据已经揭示了TCR链的两个意想不到的特征。我们发现它的恒定结构域在没有与？链结合的情况下是非结构化的，并且当它单独表达时，它的跨膜区没有整合到内质网中。这两个特征很可能在受体组装的质量控制中提供检查点。这些初步的见解将被扩展，以获得帮助和监测TCR生物合成的内质网机制的综合视图，仅允许正确组装的受体在细胞表面表达。

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.