A PEPTIDE MODEL OF BASEMENT-MEMBRANE COLLAGEN ALPHA-1(IV)531-543 BINDS THE ALPHA(3)BETA(1) INTEGRIN

Tumor cell adhesion to the triple-helical domain of basement membrane (type IV) collagen occurs at several different regions. Cellular recog nition of the sequence spanning alpha 1(IV)531-543 has been proposed t o be independent of triple-helical conformation (Miles, A. J., Skubitz , A. P. N., Furcht, L. T., and Fields, G. B. (1994) J. Biol. Chem. 269 , 30939-30945). In the present study, integrin interactions with a pep tide analog of the alpha 1(TV)531-543 sequence have been analyzed. Tum or cell adhesion (melanoma, ovarian carcinoma) to the alpha 1(IV)531-5 43 chemically synthesized peptide was inhibited by a monoclonal antibo dy against the alpha(3) integrin subunit, and to a lesser extent by mo noclonal antibodies against the beta(1) and alpha(2) integrin subunits . An anti-alpha(5) monoclonal antibody and normal mouse IgG were ineff ective as inhibitors of tumor cell adhesion to the peptide. Two cell s urface proteins of 120 and 150 kDa bound to an alpha 1(IV)531-543 pept ide affinity column and were eluted with 20 mM EDTA. When the eluted p roteins were incubated with monoclonal antibodies against either the a lpha(3) or beta(1) integrin subunit, proteins corresponding in molecul ar weight to alpha(3) and beta(1) integrin subunits were precipitated. No proteins were immunoprecipated with monoclonal antibodies against the alpha(2) or alpha(5) integrin subunits. Thus, the alpha(3) beta(1) integrin from two tumor cell types has been shown to bind directly to the alpha(1)(IV)531-543 peptide. The alpha 1(IV)531-543 peptide is th e first collagen-like sequence that has been shown to bind the alpha(3 ) beta(1) integrin.