Phosphorylation of the catalyic α-subunit constitutes a triggering signal for Na+,K+-ATPase endocytosis

Alexander V. Chibalin, Carlos H. Pedemonte, Adrian I. Katz, Eric Féraille, Per Olof Berggren, Alejandro M. Bertorello

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139 Scopus citations


Inhibition of Na+,K+-ATPase activity by dopamine is an important mechanism by which renal tubules modulate urine sodium excretion during a high salt diet. However, the molecular mechanisms of this regulation are not clearly understood. Inhibition of Na+,K+-ATPase activity in response to dopamine is associated with endocytosis of its α- and β-subunits, an effect that is protein kinase C-dependent. In this study we used isolated proximal tubule cells and a cell line derived from opossum kidney and demonstrate that dopamine-induced endocytosis of Na+,K+-ATPase and inhibition of its activity were accompanied by phosphorylation of the α-subunit. Inhibition of both the enzyme activity and its phosphorylation were blocked by the protein kinase C inhibitor bisindolylmaleimide. The early time dependence of these processes suggests a causal link between phosphorylation and inhibition of enzyme activity. However, after 10 min of dopamine incubation, the α- subunit was no longer phosphorylated, whereas enzyme activity remained inhibited due to its removal plasma membrane. Dephosphorylation occurred in the late endosomal compartment. To further examine whether phosphorylation was a prerequisite for subunit endocytosis, we used the opossum kidney cell line transfected with the rodent α-subunit cDNA. Treatment of this cell line with dopamine resulted in phosphorylation and endocytosis of the α-subunit with a concomitant decrease in Na+,K+-ATPase activity. In contrast, none of these effects were observed in cells transfected with the rodent α-subunit that lacks the putative protein kinase C-phosphorylation sites (Ser11 and Ser18). Our results support the hypothesis that protein kinase C-dependent phosphorylation of the α-subunit is essential for Na+,K+-ATPase endocytosis and that both events are responsible for the decreased enzyme activity in response to dopamine.

Original languageEnglish (US)
Pages (from-to)8814-8819
Number of pages6
JournalJournal of Biological Chemistry
Issue number15
StatePublished - Apr 10 1998

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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