Integrin binding specificity of laminin-10/11 : laminin-10/11 are recognized by alpha 3 beta 1, alpha 6 beta 1 and alpha 6 beta 4 integrins

Laminin-10/11, the laminin isoforms containing the alpha 5 chain, are major components of basement membranes of many fetal and adult tissues. Laminin- 10/11 purified from the conditioned medium of human lung carcinoma cells we re potent in mediating adhesion of the carcinoma cells in an integrin alpha 3 beta 1-dependent manner. To further define the type(s) of integrins invo lved in cell adhesion to laminin-10/11, we examined the effects of a panel of function-blocking anti-integrin antibodies on the adhesion of different cell types to laminin-10/11. Although anti-integrin beta 1 antibody inhibit ed the adhesion of all cell types tested, anti-alpha 3 antibody inhibited t he adhesion of carcinoma and glioma cells but not fibroblastic cells. Adhes ion of fibroblastic cells was inhibited, however, by a combination of anti- alpha 3 and anti-alpha 6 antibodies, suggesting that both alpha 3 beta 1 an d alpha 6 beta 1 integrins function as laminin-10/11 receptors in these cel ls. To explore this possibility, we examined the adhesion of K562 leukemic cells transfected with integrin alpha 3 or alpha 6 subunit to laminin-10/11 or other laminin isoforms, Laminin-10/11 were potent adhesive ligands for both the alpha 3 beta 1 and alpha 6 beta 1 transfectants, whereas laminin-5 was the preferred ligand for the alpha 3 beta 1 transfectants. Upon stimul ation with the activating antiintegrin beta 1 antibody, both transfectants became more adherent to the substratum regardless of the type of laminins c oated, although their preference for laminin isoforms remained unaltered. K 562 cells transfected with alpha 6 and beta 4 subunits were also capable of adhering to laminin-10/11, indicating that integrin alpha 6 beta 4 is anot her receptor for laminin-10/11. Even with lung carcinoma cells, the alpha 6 -containing integrins partly contributed to adhesion to laminin-10/11 at hi gher coating concentrations, although non-integrin receptor(s) might also b e involved under such conditions. These results indicated that laminin-10/1 1 are potent and versatile adhesive ligands in basement membranes capable o f binding to both alpha 3 beta 1 and alpha 6 beta 1 integrins with high avi dity and also to alpha 6 beta 4 integrin.