Integrin-associated Protein Is a Receptor for the C-terminal Domain of Thrombospondin

doi:10.1074/jbc.271.1.21

Integrin-associated Protein Is a Receptor for the C-terminal Domain of Thrombospondin (*)

From the Department of Biochemistry and Molecular Biophysics and
Department of Medicine and Infectious Disease, Washington University School of Medicine, St. Louis, Missouri 63110

**To whom correspondence should be addressed:
Dept. of Biochemistry and Molecular Biophysics, Box 8231, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110.
Tel.: 314-362-3348; Fax: 314-362-7183; frazier{at}bcserv.wustl.edu.

Abstract

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 αβ 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 αβ integrin, the labeled 52-kDa protein is immunoprecipitated by an anti-αβ 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.

Footnotes

↵^§ Howard Hughes postdoctoral fellow during this work and currently an investigator of the Arthritis Foundation.
↵^¶ Supported by National Institutes of Health Grant F32-AI-08990 and a grant from the Lucille P. Markey Foundation.
↵* This work was supported by grants from the National Institutes of Health (to E. J. B. and W. A. F.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

TS

thrombospondin

TS1

human thrombospondin-1

IAP

integrin-associated protein (CD47)

mAb

monoclonal antibody

CBD

cell-binding domain of human thrombospondin-1

rCBD

recombinant cell-binding domain of human thrombospondin-1

HUVEC

human umbilical vein endothelial cells

HLA

human lymphocyte antigen

TNF

tumor necrosis factor. All peptides are indicated in single-letter amino acid code, and peptides referred to by trivial names are defined in the legend to Fig. 1.
↵²F. P. Lindberg and E. J. Brown, unpublished data.
↵³F. P. Lindberg and E. J. Brown, manuscript in preparation.
↵⁴A-G. Gao, S. S. Tolsma, M. B. Finn, P. J. Polverini, N. Bouck, and W. A. Frazier, submitted for publication.
- Received October 23, 1995.
- Revision received November 8, 1995.