Asn-linked oligosaccharide-dependent interaction between laminin and gp120/140. An alpha 6/beta 1 integrin

Receptor-mediated recognition and adhesion to laminin, a specific glycoprotein from basement membranes, exert an important role in many biological phenomena. Studying cell surface proteins of B16-F10, a metastatic murine melanoma cell line, we identified a 120-140 kDa glycoprotein (gp120/140) that binds laminin. This glycoprotein was recognized by a polyclonal antibody raised against the human fibronectin receptor beta 1-integrin chain, as well as immunoprecipitated by an anti-alpha 6 chain (monoclonal antibody GoH3), characterizing it as an alpha 6/beta 1-integrin. Its binding to laminin was specific and displayed moderate affinity, as its apparent dissociation constant was 18 nM. To characterize the influence of carbohydrate moieties on the laminin-gp120/140 interaction, metaperiodate oxidation, metabolic inhibition of glycosylation, and enzymatic deglycosylation studies were performed. Our results indicate that gp120/140 Asn-linked oligosaccharides play a part in this interaction. Reciprocally, both metaperiodate and N-glycanase treatment of native laminin reduced its binding to gp120/140, characterizing the latter as a lectin-like molecule. These results point to glycosylation processes as a possible mechanism for variable binding specificity profiles among integrins.