A peptide model of basement membrane collagen α1(IV) 531-543 binds the α₃β₁ 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 α1(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 α1(IV)-531-543 sequence have been analyzed. Tumor cell adhesion (melanoma, ovarian carcinoma) to the α1(IV)531543 chemically synthesized peptide was inhibited by a monoclonal antibody against the α₃ integrin subunit, and to a lesser extent by monoclonal antibodies against the β₁ and α₂ integrin subunits. An anti-α₅ 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 α1(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 α₃ or β₁ integrin subunit, proteins corresponding in molecular weight to α₃ and β₁ integrin subunits were precipitated. No proteins were immunoprecipated with monoclonal antibodies against the α₂ or α₅ integrin subunits. Thus, the α₃β₁ integrin from two tumor cell types has been shown to bind directly to the α1(IV)531-543 peptide. The α1(IV)531-543 peptide is the first collagen- like sequence that has been shown to bind the α₃β₁ integrin.