Parathyroid hormone-mediated regulation of Na+-K +-ATPase requires ERK-dependent translocation of protein kinase Cα

Syed J. Khundmiri, William L. Dean, Kenneth R. McLeish, Eleanor D. Lederer

Research output: Contribution to journalArticle

25 Scopus citations

Abstract

Parathyroid hormone (PTH) inhibits Na+-K+-ATPase activity by serine phosphorylation of the α1 subunit through protein kinase C (PKC)- and extracellular signal-regulated kinase (ERK)-dependent pathways. Based on previous studies we postulated that PTH regulates sodium pump activity through isoform-specific PKC-dependent activation of ERK. In the present work utilizing opossum kidney cells, a model of renal proximal tubule, PTH stimulated membrane translocation of PKCα by 102 ± 16% and PKCβI by 41 ± 7% but had no effect on PKCβII and PKCζ. Both PKCα and PKCβI phosphorylated the Na +-K+-ATPase α1 subunit in vitro. PTH increased the activity of PKCα but not PKCβI. Coimmunoprecipitation assays demonstrated that treatment with PTH enhanced the association between Na+-K+-ATPase α1 subunit and PKCα, whereas the association between Na+-K+-ATPase α1 subunit and PKCβI remained unchanged. A PKCα inhibitory peptide blocked PTH-stimulated serine phosphorylation of the Na +-K+-ATPase α1 subunit and inhibition of Na+-K+-ATPase activity. Pharmacologic inhibition of MEK-1 blocked PTH-stimulated translocation of PKCα, whereas transfection of constitutively active MEK-1 cDNA induced translocation of PKCα and increased phosphorylation of the Na+-K+-ATPase α1 subunit. In contrast, PTH-stimulated ERK activation was not inhibited by pretreatment with the PKCa inhibitory peptide. Inhibition of PKCα expression by siRNA did not inhibit PTH-mediated ERK activation but significantly reduced PTH-mediated phosphorylation of the Na+-K +-ATPase α1 subunit. Pharmacologic inhibition of phosphoinositide 3-kinase blocked PTH-stimulated ERK activation, translocation of PKCα, and phosphorylation of the Na+-K+-ATPase α1 subunit. We conclude that PTH stimulates Na +-K+-ATPase phosphorylation and decreases the activity of Na+-K+-ATPase by ERK-dependent activation of PKCα.

Original languageEnglish (US)
Pages (from-to)8705-8713
Number of pages9
JournalJournal of Biological Chemistry
Volume280
Issue number10
DOIs
StatePublished - Mar 11 2005
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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