Relationship between Na+,K+-ATPase and cell attachment

A prolonged ouabain blockade of the Na+,K+-ATPase detaches cells from each other and from the substrate. This suggests the existence of a link between pump (P) and attachment (A), In the present work, we report that MDCK-W ce lls treated with ouabain increase tyrosine phosphorylation and content of a ctive MAP kinase, redistribute molecules involved in cell attachment (occlu din, ZO-1, desmoplakin, cytokeratin, alpha-actinin, vinculin and actin), an d detach. Genistein and UO126, inhibitors of protein tyrosine kinase and of MAP kinase kinase, respectively, block this detachment. The content of p19 0(Rho-GAP), a GTPase activating protein of the Rho small G-protein subfamil y, is increased by ouabain, suggesting that both the Rho/Rac and MAPK pathw ays are involved. Another clone of MDCK cells whose Na+,K+-ATPase has a neg ligible affinity for the drug, show none of the effects described for MDCK- W and remain attached. Ma104 cells, a line that has a high affinity for oua bain and stops pumping, fail to modify phosphorylation, as well as the patt ern of distribution of attaching molecules, and remain in the monolayer. Ta ken together, these results suggest that there is a mechanism (P --> A) tha t transduces a blockade of the pump in a detachment of the cell from neighb ors and substrate, in which Ma104 cells are faulty.