Regulation of Integrin Function by CD47 Ligands

doi:10.1074/jbc.M206849200

Regulation of Integrin Function by CD47 Ligands

DIFFERENTIAL EFFECTS ON α_vβ₃AND α₄β₁ INTEGRIN-MEDIATED ADHESION*

From the ^‡Laboratory of Pathology, NCI, National Institutes of Health, Bethesda, Maryland 20892 and ^¶Department of Medicine, University of Wisconsin, Madison, Wisconsin 53706

Abstract

We examined the regulation of α₄β₁ integrin function in melanoma cells and T cells by ligands of CD47. A CD47 antibody (B6H12) that inhibited α_vβ₃-mediated adhesion of melanoma cells induced by CD47-binding peptides from thrombospondin-1 directly stimulated α₄β₁-mediated adhesion of the same cells to vascular cell adhesion molecule-1 and N-terminal regions of thrombospondin-1 or thrombospondin-2. B6H12 also stimulated α₄β₁- as well as α₂β₁- and α₅β₁-mediated adhesion of CD47-expressing T cells but not of CD47-deficient T cells. α₄β₁ and CD47 co-purified as a detergent-stable complex on a CD47 antibody affinity column. CD47-binding peptides based on C-terminal sequences of thrombospondin-1 also specifically enhanced adhesion of melanoma cells and T cells to α₄β₁ ligands. Unexpectedly, activation of α₄β₁ function by the thrombospondin-1 CD47-binding peptides also occurred in CD47-deficient T cells. CD47-independent activation of α₄β₁required the Val-Val-Met (VVM) motif of the peptides and was sensitive to inhibition by pertussis toxin. These results indicate that activation of α₄β₁ by the CD47 antibody B6H12 and by VVM peptides occurs by different mechanisms. The antibody directly activates a CD47-α₄β₁ complex, whereas VVM peptides may target an unidentified G_i-linked receptor that regulates α₄β₁.

Footnotes

↵* The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵§ Present address: Laboratory of Immunology, NEI, National Institutes of Health, Bldg. 10, 10B22, Bethesda, MD 20892.
↵‖ To whom correspondence should be addressed: NIH, Bldg. 10 Rm. 2A33, 10 Center Dr., MSC 1500, Bethesda, MD 20892-1500. Tel.: 301-496-6264; Fax: 301-402-0043; E-mail: droberts@helix.nih.gov.
Published, JBC Papers in Press, September 5, 2002, DOI 10.1074/jbc.M206849200
Abbreviations:

TSP1

human thrombospondin-1

TSP2

human thrombospondin-2

NoC1

trimeric human thrombospondin-1 residues 1–356

NoC2

thrombospondin-2 residues 1–359

VCAM-1

vascular cell adhesion molecule-1

PBS

phosphate-buffered saline

BSA

bovine serum albumin

CHAPS

3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid
- Received July 9, 2002.
- Revision received September 4, 2002.
The American Society for Biochemistry and Molecular Biology, Inc.