Understanding the role of phospholipids in integrin signaling

描述（由申请人提供）：整合素是异二聚体细胞表面受体，参与细胞粘附和细胞间相互作用的调节。因此，它们在许多对人类健康至关重要的生物过程中发挥着关键作用。我们提出的研究目标是首次定量了解膜及其脂质组成在整合素激活和信号传导机制中的作用。我们采用了一种新颖的方法，采用纳米片，均匀自组装的纳米级盘状双层来精确控制膜的组成。我们将这种实验方法与分子动力学模拟结合起来，采用一种新型的膜模拟物，可以在原子分辨率上增强采样，从而详细描述蛋白质-膜界面上发生的相互作用。通过将我们的实验和理论重点放在talin上，talin是整合素参与内向外信号传导的关键激活剂，我们回答了talin如何参与膜以及阴离子磷脂，特别是PIP2的存在如何调节这种重要的相互作用的问题。此外，我们从talin的自动抑制形式剖析了其激活机制，分离了与磷脂相互作用的贡献，以及效应物Rap1， RIAM和PIPKgamma。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对配体结合的亲和力。

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.