Protein kinase C-dependent phosphorylation of Na(+)-K(+)-ATPase alpha-subunit in rat kidney cortical tubules.
We have previously shown that, in oxygenated rat kidney proximal convoluted tubules (PCT), activation of protein kinase C (PKC) by phorbol 12,13-dibutyrate (PDBu) directly stimulates Na(+)-K(+)-adenosinetriphosphatase (ATPase) activity. PKC modulation of Na(+)-K(+)-ATPase activity by phosphorylation of its alpha-subunit was the postulated mechanism. The present study was therefore designed to investigate the relationship between PKC-mediated phosphorylation of the catalytic alpha-subunit and the cation transport activity of the Na(+)-K(+)-ATPase. In a suspension of rat kidney cortical tubules, activation of PKC by 10(-7) M PDBu increased the level of phosphorylation of the Na(+)-K(+)-ATPase alpha-subunit and stimulated the ouabain-sensitive 86Rb uptake by 47 and 42%, respectively. Time and dose dependence of the PDBu-induced increase in Na(+)-K(+)-ATPase activity and phosphorylation was strongly linearly correlated. The effects of PDBu on phosphorylation and activity of Na(+)-K(+)-ATPase were prevented by GF-109203X, a specific PKC inhibitor, whereas H-89, a specific PKA inhibitor, was ineffective. These results demonstrate that PKC activation induces phosphorylation of the catalytic alpha-subunit of Na(+)-K(+)-ATPase, which may participate in the stimulation of its cation transport activity in the rat PCT.
Carranza
M L
ML
Division de Néphrologie, Hôpital Cantonal Universitaire, Geneva, Switzerland.
Féraille
E
E
Favre
H
H
D000818:Animals; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D004789:Enzyme Activation; D007672:Kidney Cortex; D007684:Kidney Tubules / Q000378:metabolism*; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011233:Precipitin Tests; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D015240:Phorbol 12,13-Dibutyrate; D010042:Ouabain; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D000254:Sodium-Potassium-Exchanging ATPase