Na/K ATPase: Signaling Versus Pumping
Abstract (Summary)Several a1 subunit knock-down LLC-PK1 cells were generated by using RNA interference assay. While the knock-down of a1 resulted in significant decrease in Na/K-ATPase activity, it increased the basal Src activity and tyrosine phosphorylation of a Src effecter FAK. This Src-interacting pool of Na/K-ATPase may serve as the receptor for ouabain to activate protein kinases. Ouabain induced activation of Src or ERK1/2 was inhibited in the a1 knock down cells whereas the EGF induced EGFR hosphorylation on several tyrosine residues were found to be potentiated by the a1 depletion. Reconstitution of the knockdown cells with wild type a1 or its pumping-null mutant can restore the above cellular functional changes induced by a1-depletion back to normal. When the ion-pumping properties were characterized in these a1 knock-down cells, we found a mismatch between the cellular Na/K-ATPase amount and its pumping activity. More than 65% of the plasma membrane Na/K-ATPase in LLC-PK1 cells are not involved in ion pumping. The size of this pool of non-pumping Na/KATPase appears to be regulated by the integrity of caveolae.
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:na k atpase signal transduction ouabain
Date of Publication:01/01/2006