G PROTEIN LINKED REGULATION OF INTEGRINS BY IAP (CD47)

在生物过程的调控中，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、肿瘤形成和血管生成的信号通路。在这项建议中，整合素相关蛋白(IAP，CD47)是一种介导整合素信号转导的共同受体，将通过操纵受体装置和配体结构来研究其作用。凝血酶敏感蛋白(TS)的C末端细胞结合域(CBD)是IAP的配体，其衍生的多肽通过异源三聚体G蛋白刺激整合素依赖的过程。为了确定G蛋白与整合素-IAP复合体的偶联机制，1)将建立整合素、IAP和G蛋白亚单位的模型表达系统，以评估在IAP激动剂处理后的细胞分析中的受体功能；2)将在转基因细胞中直接测量G蛋白偶联并与功能分析相关联，以确定每个组分在信号复合体中的作用；以及3)TS和CBD的表达和突变以确定IAP激活的决定因素。通过将受体和G蛋白成分相互作用的变化与下游或“读出”的细胞功能联系起来，这些研究应该开始确定IAP在整合素调控的生物过程中所起作用的分子基础，如血管生成、肿瘤形成和伤口愈合。

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.