G PROTEIN LINKED REGULATION OF INTEGRINS BY IAP (CD47)

整合素通过与细胞外基质蛋白结合，启动影响组织组织、炎症、凝血、肿瘤发生和血管生成的信号通路，调控生物过程。在本研究中，整合素相关蛋白（IAP, CD47）作为一种辅助受体在整合素信号传导中的作用将通过对受体装置和配体结构的操纵来研究。凝血反应蛋白（TS）的C端细胞结合域（CBD）是IAP的配体，从CBD衍生的肽通过异源三聚体G蛋白刺激整合素依赖过程。为了明确G蛋白与整合素-IAP复合物偶联的机制，1)将建立整合素、IAP和G蛋白亚基的模型表达系统，在IAP激动剂治疗后的细胞检测中评估受体功能；2)在转染细胞中进行G蛋白偶联的直接测量，并与功能分析相关联，以确定信号复合物中每个组分的作用；3)进行TS和CBD的表达和诱变，以确定IAP激活的决定因素。通过将受体和G蛋白组分相互作用的变化与下游或“读出”细胞功能联系起来，这些研究应该开始确定IAP在整合素调节的生物过程（如血管生成、肿瘤发生和伤口愈合）中作用的分子基础。

Integrins initiate signaling pathways that impact tissue organization, inflammation, blood clotting, oncogenesis and angiogenesis upon binding of extracellular matrix proteins, in the regulation of biological processes. In this proposal, the role of integrin-associated protein (IAP, CD47), a co-receptor in mediating integrin signaling, will be studied by manipulation of both the receptor apparatus and the ligand structure. The C- terminal cell-binding domain (CBD) of thrombospondin (TS) is a ligand of IAP, and peptides derived from the CBD stimulate integrin-dependent processes via heterotrimeric G proteins. To define the mechanism of G protein coupling to the integrin-IAP complex, 1) a model expression system will be established for integrins, IAP and G protein subunits to evaluate receptor function in cellular assays upon treatment with IAP agonists; 2) direct measurements of G protein coupling will be carried out in the transfected cells and correlated with functional assays to identify the role of each component in the signaling complex; and 3) expression and mutagenesis of TS and CBD will be carried out to identify the determinants for IAP activation. By correlating changes in the interactions of the receptor and G protein components with downstream or "read-out" cellular functions, these studies should begin to define the molecular basis for the role of IAP in integrin-regulated biological processes such as angiogenesis, tumorigenesis and wound healing.