Gao A G, Lindberg F P, Finn M B, Blystone S D, Brown E J, Frazier W A
Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
J Biol Chem. 1996 Jan 5;271(1):21-4. doi: 10.1074/jbc.271.1.21.
The C-terminal "cell-binding domain" (CBD) of thrombospondin-1 (TS1) is a binding site for many cell types. Cell-binding peptides based on the sequence RFYVVM from the CBD of TS1 affinity label a 52-kDa cell surface glycoprotein, which we show is integrin-associated protein (IAP or CD47). IAP associates with alpha v beta 3 and thereby modulates the activity of several integrins. Cells that express IAP bind strongly to TS1, the CBD, and its active cell-binding peptides while IAP negative cells do not. The 52-kDa protein is affinity labeled on IAP-positive but not IAP-negative cells, and monoclonal antibodies against IAP specifically immunoprecipitate the affinity-labeled 52-kDa protein from lysates of IAP-positive cells. Consistent with the association of IAP with alpha v beta 3 integrin, the labeled 52-kDa protein is immunoprecipitated by an anti-alpha v beta 3 antibody. Endothelial cells exhibit chemotaxis toward TS1 (at concentrations above 10 nM) and RFYVVM peptides. Chemotaxis to both agents is specifically inhibited by a function blocking anti-IAP monoclonal antibody. These data establish IAP (CD47) as a receptor for the CBD of TS1 and suggest a mechanism for the well established effects of the CBD on cell motility.
血小板反应蛋白-1（TS1）的C末端“细胞结合结构域”（CBD）是多种细胞类型的结合位点。基于TS1的CBD中RFYVVM序列的细胞结合肽可亲和标记一种52 kDa的细胞表面糖蛋白，我们发现该蛋白是整合素相关蛋白（IAP或CD47）。IAP与αvβ3相关联，从而调节多种整合素的活性。表达IAP的细胞能强烈结合TS1、CBD及其活性细胞结合肽，而IAP阴性细胞则不能。这种52 kDa的蛋白在IAP阳性细胞而非IAP阴性细胞上被亲和标记，并且针对IAP的单克隆抗体可从IAP阳性细胞裂解物中特异性免疫沉淀亲和标记的52 kDa蛋白。与IAP与αvβ3整合素的关联一致，标记的52 kDa蛋白可被抗αvβ3抗体免疫沉淀。内皮细胞对TS1（浓度高于10 nM）和RFYVVM肽表现出趋化性。对这两种物质的趋化性均被一种功能阻断性抗IAP单克隆抗体特异性抑制。这些数据确定IAP（CD47）为TS1的CBD的受体，并提示了CBD对细胞运动产生既定效应的一种机制。
