ADHESION OF HUMAN EPIDERMAL-KERATINOCYTES TO LAMININ

We have examined the mechanism by which human epidermal keratinocytes adhere to the A/B1/82 (alpha(1) beta(1) gamma(1)) form of laminin. Adh esion could be completely inhibited with an antibody to the beta(1) in tegrin subunit or a combination of antibodies recognising the alpha(2) beta(1), alpha(3) beta(1) and alpha(6) beta(4) integrins. Keratinocyt es adhered in the presence of magnesium and manganese ions, but calciu m ions did not support adhesion and inhibited adhesion when combined w ith magnesium and manganese. The effects of anti-integrin antibodies ( including a stimulatory antibody to the beta(1) subunit) were not infl uenced by specific cations, with the exception that inhibition by an a ntibody to alpha(2) beta(1) was abrogated by the presence of manganese ions. The E3 and E8 proteolytic fragments of laminin did not support keratinocyte adhesion and heat inactivation of the E8 site in intact l aminin did not reduce adhesion. Three laminin fragments that did suppo rt adhesion were P1, E4 and E1X-Nd, P1 activity being attributable at least in part to the RGD site; antibody blocking experiments suggested that adhesion to these fragments was primarily via alpha(3) beta(1). The synthetic peptide GD-6, derived from the carboxy terminus of the l aminin A chain (included within E3) did support adhesion, but the sign ificance of this observation is unclear, since a scrambled control pep tide could also support adhesion. In conclusion, keratinocyte adhesion to A/B1/B2 laminin involves three integrins and multiple binding site s that are different from those defined previously.