MG2-MEDIATED ADHESION OF DERMAL FIBROBLASTS AND KERATINOCYTES TO VARIOUS EXTRACELLULAR-MATRIX PROTEINS( AND CA2+ DIFFERENTIALLY REGULATE BETA(1) INTEGRIN)

The specific requirements for divalent cations in the integrin-depende nt adhesion and deadhesion of human dermal fibroblasts and human epide rmal keratinocytes to various extracellular matrix proteins have been studied in vitro. The adhesion of both cell types to collagen type I a nd to laminin was enhanced by Mg2+ in a concentration-dependent manner , while Ca2+ dose-dependently antagonized this effect, thus promoting deadhesion. The cation-dependent conversion between adhesion and deadh esion occurred already at 2 to 10 min after addition of the alternate cation and was almost completed at 20 min. Interestingly, Ca2+ could n ot reverse the Mg2+-enhanced adhesion of both cell types to fibronecti n. Inhibition studies with function-blocking antibodies directed again st distinct beta(1) integrins showed that the Mg2+-enhanced fibroblast adhesion to collagen type I was mediated by the alpha(1) beta(1) and the alpha(2) beta(1) integrins, whereas keratinocyte adhesion to colla gen type I was mediated by the alpha(2) beta(1) integrin. Both cell ty pes utilized the alpha(2) beta(1) and the alpha(6) beta(1) integrins f or Mg2+-dependent adhesion to laminin and the alpha(5) beta(1) integri n for the adhesion to fibronectin. Integrin expression at the cell sur face was not altered, indicating that divalent cation-dependent confor mational changes of beta(1) integrins most likely regulate their funct ional activity. (C) 1994 Academic Press, Inc.