Mechanisms of Membrane Targeting by C2 and PH Domains

描述（由申请人提供）：这个正在进行的项目研究C2和pleckstrin同源性（PH）基序，它们是分别在300多种和800多种人类蛋白质中用作靶向模块的保守信号结构域。这两种基元都被第二个信使激活，然后停靠在特定的胞内膜上，从而将它们的亲本蛋白靶向到底物或效应器所在的膜表面。这种靶向对于激活一系列广泛的信号通路至关重要，包括磷酸化级联、G蛋白回路、钙信号传导、囊泡运输、吞噬、内、外细胞作用、突触囊泡融合和神经递质释放、脂质衍生的第二信使的产生、细胞生长和趋化性的控制。C2和PH结构域也与多种人类疾病有关，从癌症（PTEN的C2结构域；蛋白激酶B / Akt的PH结构域）到炎症（胞质磷脂酶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，负责追踪入侵或被标记为破坏的受损细胞，这是有效免疫反应的核心途径。该项目的具体目标是阐明C2和PH结构域识别和对接到其特定靶膜的分子机制，生成两个结构域的膜对接状态的结构图，并开发白细胞趋化过程中由C2和PH结构域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和初步的研究结果，揭示了C2结构域钙的选择性和活化机制，PH结构域寻找其罕见的靶脂质的机制，以及膜结合的C2结构域的对接几何结构。总的来说，拟议的研究结果将对C2和PH结构域信号在人类健康和疾病中的分子理解具有重要意义。

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.