Understanding the role of phospholipids in integrin signaling

描述(申请人提供)：整合素是细胞表面的异二聚体受体，参与调节细胞黏附和细胞间的相互作用。因此，它们在许多对人类健康具有重要意义的生物过程中发挥着关键作用。我们提出的研究工作的目的是提供第一个定量的了解膜及其脂组成在整合素激活和信号传递机制中的作用。我们使用了一种新的方法，通过使用纳米盘，均匀的自组装纳米级盘状双层膜来提供对膜成分的精确控制。我们将这种实验方法与分子动力学模拟相结合，使用了一种新的膜模拟物，允许在原子分辨率下进行增强采样，从而详细描述了发生在蛋白质-膜界面的相互作用。通过将我们的实验和理论重点放在talin上，talin是整合素的关键激活剂，参与内向外信号传递，我们回答了talin如何与膜结合以及阴离子磷脂，特别是PIP2的存在如何调节这一重要相互作用的问题。此外，我们剖析了Talin激活的机制，它的自动抑制形式将贡献与与磷脂的相互作用以及效应器Rap1、RIAM和PIPKGamma的作用分开。通过这一综合研究计划，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。 与公共健康相关：整合素是一类重要的黏附受体，参与广泛的生物学过程，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、心脏病发作、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形成活性整合素复合体中的作用，主要集中在适配蛋白talin上。利用一套紧密耦合的理论和实验生物物理技术，目标是呈现膜表面整合素激活的详细结构图。

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.