Regulation of Human and Pig Renal Na+,K+-ATPase Activity by Tyrosine Phosphorylation of Their α1-Subunits

Modulation of the physiologically influential Na+,K+-ATPase is a complex process involving a wide variety of factors. To determine the possible effects of the protein tyrosine phosphatase (PTP) inhibitors dephostatin and Et-3,4-dephostatin on human and pig, renal cells and enzymatic extracts, we treated our samples (15 min–24 h) with those PTP inhibitors (0–100 μM). PTP inhibitors were found to possess a concentration-dependent inhibition of Na+,K+-ATPase activity in both human and pig samples. The inhibition was similarly demonstrated on all cellular, microsomal fraction and purified Na+,K+-ATPase levels. Despite rigorous activity recovery attempts, the PTP inhibitors’ effects were sustained on Na+,K+-ATPase activity. Western blotting experiments revealed the expression of both α1- and β1-subunits in both human and pig tissues. α1-Subunits possessed higher tyrosine phosphorylation levels with higher concentrations of PTP inhibitors. Meanwhile, serine/threonine residues of both α1- and β1-subunits demonstrated diminished phosphorylation levels upon dephostatin treatment. Accordingly, we provide evidence that Na+,K+-ATPase can be regulated through tyrosine phosphorylation of primarily their α1-subunits, using PTP inhibitors.