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 preferen tial activation of the alpha 2 isoform of the Na,K-ATPase. The questio n under consideration here is whether expression of the alpha 2 isofor m is sufficient to replicate its differential activation by insulin. A ccordingly, we compared the effect of insulin on the activity of the o uabain resistant rat alpha 1 and alpha 2RD (alpha 2L111R,N122D) isofor ms in HeLa cells. In HeLa cells, in contrast to the rat adipocyte, ins ulin 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 subuni ts. 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 i soform in the rat adipocyte. (C) 1997 Academic Press.