Structural correlates of T cell receptor signaling

摘要： T细胞受体与多肽-MHC的相互作用是独特的，因为每个受体都有能力参与和 对功能不同的配体作出不同的反应。了解这些特性的分子基础是 这不仅对机制洞察力很重要，而且对临床转化为抗原特异性免疫疗法也很重要。在这 建议我们重点研究TCR/pMHC界面的化学，它在识别两者的特异性中的作用 和TCR信号启动的触发阶段，以及利用这些信息来推进免疫治疗 战略。在这项提案的前一期，我们开发了一种技术，酵母肽-MHC展示，它 使我们对TCR的特异性和交叉反应的程度有了深刻的了解。我们发现 尽管TCR表现出交叉反应，但对其同源抗原具有高度特异性。这一特性使我们能够 通过对pMHC文库的无偏筛选，恢复已知的TCRs的多肽配体。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的多肽配体(例如Treg) 或来自致病系统(如癌症、自身免疫、传染病)。在目标#2中，我们希望然后 使用一种新的平台方法产生高亲和力的“TCR模拟”抗体，该抗体专门识别这些 新发现的配体，使我们能够跟踪组织表达并诱导细胞选择性杀伤 表达这些抗原。在目标3中，我们展示了pMHC库技术在理解方面也很强大 通过这种方法识别pMHC的TCR与信号之间的关系 产生大量的多肽，这些多肽可以根据信号和结构进行表征。使用这个 技术，我们令人惊讶的发现，高亲和力，但非刺激性的pMHC配体存在于 天然的人类免疫系统。我们能够分离出TCR触发形成的机制 TCR/pMHC接口中的“捕获键”，可以将TCR/pMHC结合强度与信号分离。在……里面 目标#3我们希望扩大对非刺激性TCR的研究，以更好地理解 TCR/pMHC界面触发的分子机制，并验证了一种新的观点，即捕获键 工程学，用于修改TCR，以绕过危险的方式展示更好的目标杀伤效力 亲和力成熟的TCR在过继细胞治疗中的应用。总体而言，这项建议旨在利用 TCR/pMHC结合化学在三个不同的方面有直接的翻译影响。

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.