The alpha 2L111R,N122D isoform of the Na,K-ATPase expressed in HeLa cells does not undergo an adipocyte-like increase in activity in response to insulin

In the rat adipocyte, insulin increases potassium uptake by a preferential activation of the alpha 2 isoform of the Na,K-ATPase. The question under consideration here is whether expression of the alpha 2 isoform is sufficient to replicate its differential activation by insulin. Accordingly, we compared the effect of insulin on the activity of the ouabain resistant rat alpha 1 and alpha 2RD (alpha 2L111R,N122D) isoforms in HeLa cells. In HeLa cells, in contrast to the rat adipocyte, insulin produces an increase of equal magnitude in the rate of Rb-86(+)/K+ uptake by the ouabain resistant rat alpha 1 and rat alpha 2RD subunits. We conclude that the mechanism of insulin activation of the alpha 2RD isoform in HeLa cells differs from that of the wild type alpha 2 isoform in the rat adipocyte. (C) 1997 Academic Press.