Structural correlates of T cell receptor signaling

摘要： T细胞受体与肽-MHC的相互作用是独特的，因为每种受体都具有参与并 对功能上不同的配体有不同的反应。了解这些性质的分子基础是 这不仅对机理认识很重要，而且对抗原特异性免疫疗法的临床转化也很重要。在这 我们的建议集中在TCR/pMHC界面的化学，其在特异性识别两者中的作用 和TCR信号启动的触发阶段，以及使用这些信息来促进免疫调节， 战略布局本课题前期，我们开发了一种酵母肽-MHC展示技术， 使我们能够深入了解TCR特异性和交叉反应性的程度。我们发现 TCR对其同源抗原具有高度特异性，尽管表现出交叉反应性。这一特性使我们 通过pMHC文库的无偏筛选回收TCR的已知肽配体。现在，在目标1中， 这一发现开辟了许多令人兴奋的可能性：主要是使用pMHC显示技术来查询 TCR的特异性，并鉴定天然免疫系统中“孤儿”TCR的肽配体（例如Treg） 或来自致病系统（例如癌症、自身免疫、传染病）。在目标#2中，我们希望 使用一种新的平台方法产生高亲和力的“TCR模拟物”抗体， 新发现的配体，使我们能够跟踪组织表达和诱导细胞的选择性杀伤 表达这些抗原。在目标#3中，我们展示了pMHC文库技术对于理解 TCR对pMHC的识别与信号传导之间的关系， 产生大量的肽，这些肽可以在信号传导和结构方面进行表征。使用此 技术，我们令人惊讶的发现，高亲和力，但非刺激性pMHC配体存在于 天然的人类免疫系统我们能够“分离”TCR触发形成的机制， TCR/pMHC界面中的“捕获键”，其可以将TCR/pMHC结合强度与信号传导解耦。在 当前提案的目标#3，我们希望扩展我们对非刺激性TCR的研究，以更好地了解 在TCR/pMHC界面触发的分子机制，并测试一个新的想法，'捕捉键 工程，用于修饰TCR，以绕过危险的方式表现出提高的靶杀伤效力 亲和力成熟的TCR在过继性细胞治疗中的应用总的来说，这项建议旨在利用“第一原则”， TCR/pMHC结合化学沿着三个不同的前沿，具有直接的翻译影响。

Abstract: The T cell receptor interaction with peptide-MHC is unique in that each receptor has the capacity to engage and differentially respond to functionally distinct ligands. Understanding the molecular basis for these properties is important not only for mechanistic insight but for clinical translation to antigen-specific immunotherapies. In this proposal we focus on the chemistry of the TCR/pMHC interface, its role in the specificity of both the recognition and triggering phases of TCR signal initiation, and the use of this information to advance immunotherapeutic strategies. In the prior term of this proposal, we developed a technology, yeast peptide-MHC display, which enabled us obtain a deep understanding of the extent of TCR specificity and cross-reactivity. We found that TCRs are highly specific for their cognate antigens despite exhibiting cross-reactivity. This property enabled us to recover the known peptide ligands of TCRs through un-biased screening of pMHC libraries. Now, in Aim #1, this finding has opened up many exciting possibilities: principally to use pMHC display technology to query the specificity of TCRs, and to identify peptide ligands for ‘orphan’ TCRs in the natural immune system (e.g. Treg) or from pathogenic systems (e.g. cancer, autoimmunity, infectious disease). In Aim #2 we wish to then then generate high-affinity “TCR mimic” antibodies, using a novel platform approach, that specifically recognize these newly discovered ligands and enables us to track tissue expression and inducing selective killing of cells expressing these antigens. In Aim #3, we show that pMHC library technology is also powerful for understanding the relationship between TCR recognition of pMHC and signaling through the capacity of this approach to generate large panels of peptides that can be characterized with respect to signaling and structure. Using this technology, we made the surprising finding that high-affinity, but non-stimulatory pMHC ligands exist in the natural human immune repertoire. We were able to ‘isolate’ the mechanism of TCR triggering to the formation of “catch bonds” in the TCR/pMHC interface, which can decouple TCR/pMHC binding strength from signaling. In Aim #3 of the current proposal we wish to expand on our studies of non-stimulatory TCRs to better understand the molecular mechanisms of triggering at the TCR/pMHC interface, and test a new idea, ‘catch bond engineering,’ for modifying TCRs to exhibit improved target killing potency in a way that bypasses the dangers of affinity-matured TCRs in adoptive cell therapy. Collectively, this proposal aims to exploit ‘first principles’ of TCR/pMHC binding chemistry along three different fronts that have direct translational impact.