Mechanisms of Membrane Targeting by C2 and PH Domains

描述(由申请人提供)：这个持续的项目研究C2和Pleckstrin同源(PH)基序，这是一种保守的信号域，分别在300和800多个人类蛋白质中用作靶向模块。这两个基序都被第二个信使激活，然后对接到特定的细胞膜上，从而将它们的亲本蛋白靶向底物或效应器所在的膜表面。这种靶向对于一系列信号通路的激活是必不可少的，包括磷酸化级联、G蛋白通路、钙信号、囊泡运输、吞噬、胞内和胞外、突触囊泡融合和神经递质释放、产生脂类衍生的第二信使、控制细胞生长和趋化。C2和PH结构域也与一系列人类疾病有关，从癌症(PTEN的C2结构域；蛋白激酶B/Akt的PH结构域)到炎症(胞浆磷脂酶A2的C2结构域)。此外，多个C2和PH结构域是白细胞趋化途径的重要组成部分，负责追踪标记为破坏的入侵或受损细胞，这一途径是有效免疫反应的核心。该项目的具体目标是阐明C2和PH结构域识别和对接其特定靶膜的分子机制，生成这两个结构域的膜对接状态的结构图，并开发C2和PH结构域在白细胞趋化过程中触发的靶向事件的复杂网络的时空图。该进展报告描述了已发表的初步结果，揭示了C2结构域的钙选择性和激活机制，PH结构域寻找其稀有靶标脂质的机制，以及膜结合C2结构域的对接几何结构。总体而言，拟议的研究结果将对分子理解C2和PH结构域信号在人类健康和疾病中的作用具有重要意义。

DESCRIPTION (provided by applicant): This continuing project investigates the C2 and pleckstrin homology (PH) motifs, which are conserved signaling domains used as targeting modules in over 300 and 800 human proteins, respectively. Both of these motifs are activated by a second messenger then dock to a specific intracellular membrane, thereby targeting their parent proteins to the membrane surface where substrates or effectors are located. Such targeting is essential for the activation of a wide array of signaling pathways, including phosphorylation cascades, G protein circuits, calcium signaling, vesicle trafficking, phago-, endo-, and exo-cytosis, synaptic vesicle fusion and neurotransmitter release, generation of lipid-derived second messengers, control of cell growth and chemotaxis. C2 and PH domains are also linked to a wide array of human diseases ranging from cancer (C2 domain of PTEN; PH domain of protein kinase B / Akt) to inflammation (C2 domain of cytosolic phospholipase A2). Moreover, multiple C2 and PH domains are essential components of the leukocyte chemotaxis pathway responsible for tracking down invading or damaged cells marked for destruction, a pathway that is central to effective immune response. The Specific Aims of the project are to elucidate the molecular mechanisms used by C2 and PH domains to recognize and dock to their specific target membranes, to generate a structural picture of the membrane-docked states of both domains, and to develop a spatiotemporal map of the complex web of targeting events triggered by C2 and PH domains during leukocyte chemotaxis. The Progress Report describes published and preliminary results revealing the mechanisms of C2 domain calcium selectivity and activation, the mechanism of PH domain searching for its rare target lipid, and the docking geometry of membrane-bound C2 domains. Overall, the results of the proposed studies will have significant implications for a molecular understanding of C2 and PH domain signaling in human health and disease.