Structural Transition of Cellular Integrins and Applications Thereof

 描述（由申请人提供）：整合素是α/β异源二聚体细胞表面受体，通过其以多种构象存在的能力，调节多种生物学特性， 在许多人类疾病中起着关键作用。与整联蛋白的细胞外或细胞质面结合的蛋白质可影响长距离构象变化，将整联蛋白从静息低亲和力状态转化为活化高亲和力状态，这是一种对止血和血栓形成至关重要的整联蛋白（如αIIbβ3）的严格调控过程。整联蛋白的正常生物学功能由活化和失活状态之间的严格控制的平衡来调节。虽然在理解整合素活化的机制和分子方面取得了很大进展，但对整合素失活的过程知之甚少。我们一直从事于配体结合诱导的整合素构象变化导致激活的结构和功能分析，并已确定了一系列新的竞争性抑制剂，与传统的抑制剂不同，它可以取代αIIbβ3的配体而不诱导构象变化。基于这些发现，这项研究旨在研究整合素失活过程中发生的结构转变，我们假设这是由整合素的内在结构特征。将使用新型晶体学、生物化学和生物物理学方法的组合来定义αIIbβ3头片段在原子水平、细胞表面完整整合素中和溶液中构象失活的不同阶段。特定相互作用的相对贡献 将定义整合素失活中的胞外、跨膜和胞质结构域。N-连接糖基化在αIIbβ3和αVβ3整联蛋白构象调节中的重要性将被表征，并与人类疾病（如癌症和糖尿病）中的异常整联蛋白糖基化相关。这些研究的结果将使我们能够探索新的和广泛适用的策略，设计整合素拮抗剂，阻断配体结合，同时稳定（而不是破坏）的非活性构象，因此，这可能是上级现有的整合素拮抗剂，无意中诱导整合素活化。第二个目标集中于α整联蛋白胞质尾区（CT）在整联蛋白功能中的作用，源于我们最近的观察，即α-整联蛋白CT的膜远端（MD）区域对于整联蛋白活化是必不可少的。使用αIIb、αL和α5整合素作为产生MD区域交换嵌合体的平台，我们将研究α整合素CT MD区域在调节整合素构象激活和信号传导中的序列和结构决定因素。使用多方面的方法，我们将检查在原位整合素活化过程中α和β跨膜和胞质结构域的构象变化。总之，这些互补的特异性目的将促进我们对整合素构象转变的分子基础的理解，并提供对双向整合素信号传导的基于结构的见解，这将促进具有改善的治疗功效的新型整合素拮抗剂的开发。

 DESCRIPTION (provided by applicant): Integrins are α/β heterodimeric cell surface receptors, which, via their ability to exist in multiple conformations, regulate diverse biological processes and play critical roles in many human diseases. Proteins binding to either the extracellular or cytoplasmic face of an integrin can effect long-range conformational changes that convert integrin from a resting low-affinity to an activated high-affinity state, a tightly regulated process for integrins such as αIIbβ3 that is essential for both hemostasis and thrombosis. Normal biological functions of integrins are regulated by a tightly-controlled balance between activated and deactivated states. Although much progress has been made in understanding the mechanisms and molecules involved in integrin activation, the process of integrin deactivation is poorly understood. We have been engaged in structural and functional analyses of ligand-binding-induced integrin conformational changes leading to activation and have identified a novel series of competitive inhibitors, which, unlike conventional inhibitors, ca displace ligand from αIIbβ3 without inducing conformational changes. Based on these findings, this grant seeks to examine the structural transitions that occur during integrin deactivation, which we hypothesize is governed by intrinsic structure features of the integrin. A combination of novel crystallographic, biochemical and biophysical approaches will be used to define distinct stages of conformational deactivation of the αIIbβ3 headpiece at the atomic level, in intact integrins on the cell surface, and in solution. The relative contributions of specific interactions among the extracellular, transmembrane, and cytoplasmic domains in integrin deactivation will be defined. The importance of N-linked glycosylation in the conformational regulation of αIIbβ3 and αVβ3 integrins will be characterized and correlated with aberrant integrin glycosylation in human diseases like cancer and diabetes. Outcomes of these studies will enable us to explore novel and widely applicable strategies for designing integrin antagonists that block ligand binding while stabilizing (rather than disrupting) the inactive conformation and which may, therefore, be superior to existing integrin antagonists, which inadvertently induce integrin activation. A second aim focused on the role of α integrin cytoplasmic tail (CT) in integrin function, grew out of our recent observation that the membrane-distal (MD) region of the α-integrin CT is indispensable for integrin activation. Using αIIb, αL, and α5 integrins as platfoms for generating MD region swapped chimeras, we will examine the sequence and structural determinants of the α integrin CT MD region in regulating integrin conformational activation and signaling. Using multifaceted approaches, we will examine the conformational changes of both α and β transmembrane and cytoplasmic domains during integrin activation in situ. Together, these complementary Specific Aims will advance our understanding of the molecular basis for integrin conformational transitions and provide structure-based insights into bidirectional integri signaling, which will facilitate the development of novel integrin antagonists that have improved therapeutic efficacy.