Understanding the role of phospholipids in integrin signaling

描述（由申请人提供）：整联蛋白是异二聚体细胞表面受体，参与细胞粘附和细胞-细胞相互作用的调节。因此，它们在许多对人类健康重要的生物过程中发挥着关键作用。我们提出的研究工作的目标是首次定量了解膜及其脂质成分对整合素激活和信号传导机制的作用。我们采用了一种新颖的方法，即采用纳米圆盘（Nanodiscs），即均匀的自组装纳米级盘状双层，以提供对膜成分的精确控制。我们将这种实验方法与采用新型膜模拟物的分子动力学模拟相结合，该模拟物允许以原子分辨率增强采样，从而详细描述蛋白质-膜界面处发生的相互作用。通过将我们的实验和理论重点集中在talin（参与由内而外信号传递的整合素的关键激活剂）上，我们回答了有关talin如何与膜结合以及阴离子磷脂（特别是PIP2）的存在如何调节这种重要相互作用的问题。此外，我们剖析了talin激活的机制及其自动抑制形式，将其与磷脂相互作用的贡献分开，以及效应器Rap1、RIAM和PIPKgamma的贡献。通过这个综合研究计划，我们试图了解这些相互作用的总和如何调节整合素的激活并控制其与配体结合的亲和力。 公共健康相关性：整合素是一类重要的粘附受体，参与广泛的生物过程，包括胚胎发育、止血、细胞迁移、伤口愈合和免疫反应，其功能受损与关节炎、心脏病、中风和癌症等关键人类疾病有关。该项目旨在研究膜表面在活性整联蛋白复合物形成中的作用，主要关注接头蛋白踝蛋白。采用一套紧密结合的理论和实验生物物理技术，目标是提供膜表面整合素激活的详细结构视图。

DESCRIPTION (provided by applicant): Integrins are heterodimeric cell surface receptors involved in the regulation of cellular adhesion and cell-cell interactions. As such they play a critical role in many biological processes of importance to human health. The goal of our proposed research effort is to provide the first quantitative understanding of role of the membrane and its lipid composition on the mechanism of integrin activation and signaling. We use a novel approach by employing Nanodiscs, homogeneous self- assembled nanometer scale discoidal bilayers to provide precise control of the membrane composition. We couple this experimental approach with molecular dynamic simulations employing a novel membrane mimetic that allows enhanced sampling at an atomic resolution, thereby a detailed description of the interactions occurring at the protein-membrane interface. By focusing our experimental and theoretical thrusts on talin, a key activator of integrin involved in inside-out signaling, we answr questions as to how talin engages the membrane and how the presence of anionic phospholipids, in particular PIP2, regulates this important interaction. In addition, we dissect th mechanism of talin activation from its auto-inhibited form separating the contributions from interactions with phospholipids, and that of the effectors Rap1, RIAM, and PIPKgamma. Through this integrated research plan we seek to understand how the sum of these interactions regulates the activation of integrin and control its affinity for ligand binding. PUBLIC HEALTH RELEVANCE: Integrins are an important class of adhesion receptors that are involved in a wide range of biological processes including embryonic development, hemostasis, cell migration, wound healing, and the immune response and their impaired function has been linked to key human diseases such as arthritis, heart attack, stroke, and cancer. This project seeks to investigate the role of the membrane surface in the formation of active integrin complexes with primary focus on the adapter protein talin. Employing a closely coupled set of theoretical and experimental biophysical techniques, the goal is to present a detailed structural view for activation of integrin on a membrane surface.