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 recognition of the sequence spanning alpha 1(IV)531-543 has been proposed to 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 peptide analog of the alpha 1(IV)-531-543 sequence have been analyzed. Tumor cell adhesion (melanoma, ovarian carcinoma) to the alpha 1(IV)531-543 chemically synthesized peptide was inhibited by a monoclonal antibody against the alpha 3 integrin subunit, and to a lesser extent by monoclonal antibodies against the beta 1 and alpha 2 integrin subunits. An anti-alpha 5 monoclonal antibody and normal mouse IgG were ineffective as inhibitors of tumor cell adhesion to the peptide. Two cell surface proteins of 120 and 150 kDa bound to an alpha 1(IV)531-543 peptide affinity column and were eluted with 20 mM EDTA. When the eluted proteins were incubated with monoclonal antibodies against either the alpha 3 or beta 1 integrin subunit, proteins corresponding in molecular 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 the first collagen-like sequence that has been shown to bind the alpha 3 beta 1 integrin.