Novel Regulatory Mechanisms Underlying Inside-out Integrin Activation

项目摘要/摘要 整合素在细胞的基本功能中也扮演着重要的角色，如黏附、生长和迁移 在止血和T细胞免疫中的特殊功能 回应。整合素的异常表达和过度活动导致心血管疾病，受损 炎症反应、T细胞功能障碍和肿瘤转移增强。目前的整合素抑制剂 阻断细胞外配体结合往往会引起严重的不良反应。我们的总体目标是阐明 通过由内而外的信号通路激活整合素的分子机制，因此 促进针对这一途径的新疗法的开发。这项拟议研究的主要重点是 要了解分子间相互作用和分子内重排的结构基础， 调节整合素的活性，从而改变细胞的黏附和运动。 整合素信号通路是近年来出现的抑制整合素的新靶点 活动。整合素的激活通过这一途径由talin触发，并由一个小的GTP酶Rap1， 及其效应蛋白RIAM(Rap1相互作用接头分子)。共同激活剂Kindlin也显著地 提高了整合素的活性。然而，关于如何具体地在分子间和分子内 由内向外调节整合素激活的相互作用仍未得到回答。 我们之前已经确定了RAP1和PM招募RAM的结构基础 Riam对talin的移位和构象激活作用。在这项建议中，我们的目标是解决以下问题 关于构象重排和潜在的特定相互作用的中心问题 Riam、talin和kindlin的功能调控：1)阐明分子内调控的结构基础 RIAM和Talin的相互作用；2)确定TALIN活性增强的分子基础 Riam和talin的相互作用；3)探讨不同整合素的分子机制。 Kindlin异构体之间的调节特性以及kindlin和talin在整合素信号转导中的共定位。 我们的研究将极大地促进对整合素激活调节机制的理解 通过由内而外的路径。

Project Summary/Abstract Integrins play important roles in basic cellular functions such as adhesion, growth, and migration as well as specialized functions in platelet plug formation during hemostasis and in T cell mediated immune responses. Abnormal expression and hyperactivity of integrins leads to cardiovascular diseases, impaired inflammatory responses, T cell malfunction, and enhanced tumor metastasis. Current integrin inhibitors that block extracellular ligand binding often cause serious adverse effects. Our overall goal is to elucidate the molecular mechanisms that activate integrins more specifically through the inside-out signaling pathway, thus facilitating the development of new therapies targeting this pathway. The main focus of this proposed study is to understand the structural basis of intermolecular interactions and intramolecular rearrangements that modulate integrin activity, thus altering cell adhesion and motility. The inside-out integrin signaling pathway has recently emerged as a new target for suppressing integrin activity. Integrin activation through this pathway is triggered by talin and mediated by a small GTPase, Rap1, and its effector protein RIAM (Rap1-interacting adaptor molecule). A co-activator, kindlin, also significantly enhanced the integrin activity. However, many key questions regarding how specific inter- and intra-molecular interactions regulate inside-out integrin activation remain unanswered. We have previously determined the structural basis of RIAM recruitment by Rap1 and the PM translocation and conformational activation of talin by RIAM. In this proposal, we aim to address the following central questions regarding the conformational rearrangement and specific interactions underlying the functional regulation of RIAM, talin, and kindlin: 1) to elucidate the structural basis of regulatory intramolecular interactions of RIAM and talin; 2) to determine the molecular basis of enhanced talin activity induced by the interaction of RIAM and talin; and 3) to probe the molecular mechanisms underlying the different integrin- regulating properties among kindlin isoforms and the co-localization of kindlin and talin in integrin signaling. Our studies will significantly advance the understanding of the regulatory mechanisms of integrin activation through the inside-out pathway.