A Role of Chondroitin Sulfate Glycosaminoglycan Binding Site in α4β1 Integrin-mediated Melanoma Cell Adhesion

doi:10.1074/jbc.273.10.5955

A Role of Chondroitin Sulfate Glycosaminoglycan Binding Site in α₄β₁ Integrin-mediated Melanoma Cell Adhesion*

From the ^‡Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, Minnesota 55455, the ^¶Department of Orthopedic Surgery and Biochemistry, University of Minnesota, Minneapolis, Minnesota 55455, ^‖Athena Neuroscience Inc., South San Francisco, California 94080, the ^**Division of Hematology, School of Medicine, University of Washington, Seattle, Washington 98195, and the ^‡Biomedical Engineering Institute, University of Minnesota, Minneapolis, Minnesota 55455

Abstract

We have previously reported that α₄β₁ (but not α₅β₁) integrin-mediated melanoma cell adhesion is inhibited by removal of cell surface chondroitin sulfate glycosaminoglycan (CSGAG), suggesting that melanoma chondroitin sulfate proteoglycan plays a role in modulating the adhesive function of α₄β₁ integrin. In the current study, we demonstrated that α₄β₁ integrin binds to CSGAG. We have identified a peptide from within α₄ integrin termed SG1 (KKEKDIMKKTI) that binds to cell surface melanoma chondroitin sulfate proteoglycan, indicating that SG1 represents a CSGAG binding site within the α₄ integrin subunit. Soluble SG1 inhibits α₄β₁integrin-mediated human melanoma cell adhesion to CS1. Polyclonal antibody generated against the peptide inhibits melanoma cell adhesion to CS1, and the inhibition is reversed by Mn²⁺ and an activating monoclonal antibody anti-β₁ (8A2). Additionally, pretreatment of cells with anti-SG1 IgG inhibits the expression of the monoclonal antibody 15/7 epitope in the presence of soluble CS1 peptide, suggesting that anti-SG1 IgG prevents ligand binding by α₄β₁ integrin. These results demonstrate that α₄β₁ integrin interacts directly with CSGAG through SG1 site, and that this site can affect the ligand binding properties of the integrin.

Footnotes

↵* This work was supported by Grant CA21463 from the National Institutes of Health and a Allen-Pardee professorship in Cancer Biology (to L. T. F.).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.
↵§ To whom correspondence should be addressed: Dept. of Laboratory Medicine and Pathology, Box 609, University of Minnesota Health Center, 420 Delaware St. S. E., University of Minnesota, Minneapolis, MN 55455.
↵1 The abbreviations used are: ECM, extracellular matrix; CSGAG, chondroitin sulfate glycosaminoglycan; MCSP, melanoma chondroitin sulfate proteoglycan; mAb, monoclonal antibody; FN, fibronectin; CSPG, chondroitin sulfate proteoglycan; GAG, glycosaminoglycan; OVA, ovalbumin; EDC,l-ethyl-3(3-dimethylaminopropyl)-carbodiimide hydrochloride; NEM, N-ethylmaleimide; PMSF, phenylmethylsulfonyl fluoride; BSA, bovine serum albumin; PBS, phosphate-buffered saline; PG, proteoglycan.
↵2 J. Iida, unpublished data.
↵3 J. Iida, unpublished observations.
↵4 A. M. L. Meijne, J. Iida, T. A. Yednock, N. L. Kovach, L. T. Furcht, and J. B. McCarthy, submitted for publication.
- Received September 10, 1997.
- Revision received December 9, 1997.
The American Society for Biochemistry and Molecular Biology, Inc.