Physical Basis for T Cell Receptor Binding and Activity

描述(申请人提供)：TCR识别由MHC蛋白结合和呈递的多肽抗原是细胞免疫的基石。尽管TCR-pMHC相互作用的结构知识在过去十年中激增，但我们对TCR如何与pMHC结合并实现特异性、交叉反应性和MHC限制等关键免疫现象的理解仍存在显著差距。事实上，近年来关于TCR识别特性的决定因素存在争议，例如TCR在多大程度上进化地偏向于参与MHC蛋白，以及这种偏向如何受到其他因素的影响。此外，结构免疫学家正将越来越多的注意力集中在分子运动上，分子运动已被证明对特异性、交叉反应甚至潜在的信号传递具有复杂且鲜为人知的影响。随着抗原表位和TCR开始用于临床，除了提供基本的免疫学信息外，更好地了解TCR如何实现特异性、交叉反应和信号是至关重要的。这项竞争性的更新提案描述了一项雄心勃勃的计划，以解决与上述问题相关的关键问题，目标不仅是揭示基本原则，而且还推动基于TCR和pMHC的疗法的发展。有两个大致互补的具体目标。第一个将决定TCR-pMHC结合能的分布是如何由进化和非进化力量塑造的。将应用一系列实验方法，包括双突变循环分析、X射线结晶学、蛋白质工程和结构生物信息学。第二个目标将确定分子运动在TCR和pMHC识别中的作用和影响。将再次使用一系列方法，包括核磁共振、荧光和计算。在这两个目标中，将检验一些新的假设，包括我们的假设，即TCR结合部位已经进化出一种结构和能量的透射性，允许受体调整以适应每个界面中存在的独特化学物质。我们还将测试以下假设：MHC动力学的多肽调节影响NK受体结合，以及结合时TCR动力学的变化有助于T细胞信号转导。

DESCRIPTION (provided by applicant): TCR recognition of peptide antigens bound and presented by MHC proteins is a cornerstone of cellular immunity. Although structural knowledge of TCR-pMHC interactions has surged over the past decade, there are significant gaps in our understanding of how TCRs engage pMHC and achieve the key immunological phenomena of specificity, cross-reactivity, and MHC restriction. Indeed, recent years have seen controversy regarding the determinants of TCR recognition properties, such as the extent to which TCRs are evolutionarily biased towards engaging MHC proteins and how such bias may be influenced by other factors. Additionally, structural immunologists are focusing increased attention on molecular motion, which has been shown to have complex and poorly understood influences on specificity, cross-reactivity, and potentially even signaling. Beyond informing basic immunology, an improved understanding of how TCRs achieve specificity, cross-react, and signal is crucial as antigenic epitopes and TCRs begin to be used in clinical settings. This competitive renewal proposal describes an ambitious plan to address key questions related to the issues above, with goals of not only uncovering fundamental principles, but also advancing the development of TCR and pMHC-based therapeutics. There are two broadly complementary specific aims. The first will determine how the distribution of TCR-pMHC binding energy is shaped by evolutionary and non-evolutionary forces. A range of experimental approaches will be applied, including double mutant cycle analyses, X-ray crystallography, protein engineering, and structural bioinformatics. The second aim will establish the role and impact of molecular motion in TCR and pMHC recognition. A range of approaches will again be used, including NMR, fluorescence, and computation. Throughout both aims, a number of novel hypotheses will be tested, including our hypothesis that the TCR binding site has evolved a structural and energetic permissiveness that permits the receptor to adjust to the unique chemistry present in each interface. We will also test the hypotheses that peptide modulation of MHC dynamics influences NK receptor binding, and that alterations in TCR dynamics upon binding contribute to T cell signaling.