Hormonal-dependent recruitment of Na+,K+-ATPase to the plasmalemma is mediated by PKC beta and modulated by [Na+]i.
1. The present study demonstrates that stimulation of hormonal receptors of proximal tubule cells with the serotonin-agonist 8-hydroxy-2-(di-n-propylamino) tetraline (8-OH-DPAT) induces an augmentation of Na(+),K(+)-ATPase activity that results from the recruitment of enzyme molecules to the plasmalemma. 2. Cells expressing the rodent wild-type Na(+),K(+)-ATPase alpha-subunit had the same basal Na(+),K(+)-ATPase activity as cells expressing the alpha-subunit S11A or S18A mutants, but stimulation of Na(+),K(+)-ATPase activity was completely abolished in either mutant. 3. 8-OH-DPAT treatment of OK cells led to PKC(beta)-dependent phosphorylation of the alpha-subunit Ser-11 and Ser-18 residues, and determination of enzyme activity with the S11A and S18A mutants indicated that both residues are essential for the agonist-dependent stimulation of Na(+),K(+)-ATPase activity. 4. When cells were treated with both dopamine and 8-OH-DPAT, an activation of Na(+),K(+)-ATPase was observed at basal intracellular sodium concentration (approximately 9 mM), and this activation was gradually reduced and became a significant inhibition as the concentration of intracellular sodium gradually increased from 9 to 19 mM. Thus, besides the antagonistic effects of dopamine and 8-OH-DPAT, intracellular sodium modulates whether an activation or an inhibition of Na(+),K(+)-ATPase is produced.
Budu
Claudia E
CE
College of Pharmacy, University of Houston, Houston, Texas, TX 77204, U.S.A.
Efendiev
Riad
R
Cinelli
Angel M
AM
Bertorello
Alejandro M
AM
Pedemonte
Carlos H
CH
D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007424:Intracellular Fluid / Q000201:enzymology / Q000378:metabolism*; D007668:Kidney / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D009893:Opossums; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D064546:Protein Kinase C beta; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011985:Receptors, Serotonin / Q000378:metabolism; D012964:Sodium / Q000378:metabolism / Q000502:physiology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism*
D004791:Enzyme Inhibitors; D011956:Receptors, Cell Surface; D011985:Receptors, Serotonin; D012964:Sodium; D011493:Protein Kinase C; D064546:Protein Kinase C beta; D000254:Sodium-Potassium-Exchanging ATPase