Identification of protein kinase C as an intermediate in Na,K-ATPase beta-subunit mediated lamellipodia formation and suppression of cell motility in carcinoma cells.

We have shown that repletion of Na,K-ATPase Beta1-subunit (Na,K-Beta) in Moloney Sarcoma virus transformed MDCK (MSV-Na,K-Beta) cells induced lamellipodia and suppressed motility in a PI3-Kinase dependent manner. In this study, we provide evidence that decreased cell motility is due to increased attachment of Na,K-Beta expressing cells to the substratum. Treatment of MSV-Beta-GFP cells with bisindolylmalemide, a general Protein Kinase C (PKC) inhibitor, abolished PI3-Kinase activation and its down stream effects of Rac1 activation, binding of Na,K-Beta to annexin II, and suppression of cell motility and attachment. Thus, these studies unraveled that a PKC is involved upstream of PI3-Kinase in the suppression of Na,K-Beta mediated cell motility in carcinoma cells.