Novel Regulatory Mechanisms Underlying Inside-out Integrin Activation

项目总结/摘要 整合素在细胞的粘附、生长、迁移等基本功能中发挥重要作用 作为止血过程中血小板栓形成和T细胞介导的免疫调节的专门功能， 应答整合素的异常表达和过度活性导致心血管疾病， 炎症反应、T细胞功能障碍和增强的肿瘤转移。目前的整联蛋白抑制剂， 阻断细胞外配体结合常引起严重的不良反应。我们的总体目标是阐明 分子机制，激活整合素更具体地通过由内而外的信号通路，因此， 促进针对该途径的新疗法的开发。这项拟议研究的主要重点是 了解分子间相互作用和分子内重排的结构基础， 调节整联蛋白活性，从而改变细胞粘附和运动性。 由内而外的整合素信号通路最近成为抑制整合素的新靶点 活动通过该途径的整合素活化由talin触发并由小的GT3，Rap 1介导， 及其效应蛋白RIAM（Rap 1相互作用衔接分子）。一种共激活剂，kindlin， 增强整合素活性。然而，许多关键问题，关于如何具体的分子间和分子内 相互作用调节由内而外的整联蛋白活化仍然没有答案。 我们之前已经确定了Rap 1和PM招募RIAM的结构基础 通过RIAM对talin的转位和构象激活。在这一建议中，我们旨在解决以下问题 关于构象重排和特定相互作用的中心问题， RIAM，talin和kindlin的功能调节：1）阐明调节分子内的结构基础 研究了RIAM和talin的相互作用; 2）确定了由RIAM诱导的talin活性增强的分子基础。 RIAM和talin的相互作用;和3）探索不同整合素的分子机制。 Kindlin同种型之间的调节特性以及Kindlin和talin在整联蛋白信号传导中的共定位。 我们的研究将显著推进对整合素激活的调控机制的理解 通过由内而外的途径。

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.