Parathyroid hormone inhibits renal phosphate transport by phosphorylation of serine 77 of sodium-hydrogen exchanger regulatory factor-1

J Clin Invest. 2007 Nov;117(11):3412-20. doi: 10.1172/JCI32738.

Abstract

Parathyroid hormone (PTH), via activation of PKC and/or protein kinase A, inhibits renal proximal tubular phosphate reabsorption by facilitating the internalization of the major sodium-dependent phosphate transporter, Npt2a. Herein, we explore the hypothesis that the effect of PTH is mediated by phosphorylation of serine 77 (S77) of the first PDZ domain of the Npt2a-binding protein sodium-hydrogen exchanger regulatory factor-1 (NHERF-1). Using recombinant polypeptides representing PDZ I, S77 of NHERF-1 is phosphorylated by PKC but not PKA. When expressed in primate kidney epithelial cells (BSC-1 cells), however, activation of either protein kinase phosphorylates S77, suggesting that the phosphorylation of PDZ I by PKC and PKA proceeds by different biochemical pathways. PTH and other activators of PKC and PKA dissociate NHERF-1/Npt2a complexes, as assayed using quantitative coimmunoprecipitation, confocal microscopy, and sucrose density gradient ultracentrifugation in mice. Murine NHERF-1-/- renal proximal tubule cells infected with adenovirus-GFP-NHERF-1 containing an S77A mutation showed significantly increased phosphate transport compared with a phosphomimetic S77D mutation and were resistant to the inhibitory effect of PTH compared with cells infected with wild-type NHERF-1. These results indicate that PTH-mediated inhibition of renal phosphate transport involves phosphorylation of S77 of the NHERF-1 PDZ I domain and the dissociation of NHERF-1/Npt2a complexes.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Retracted Publication

MeSH terms

  • Animals
  • Biological Transport / physiology
  • Cells, Cultured
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • Enzyme Activation
  • Enzyme Inhibitors / metabolism
  • Kidney / cytology
  • Kidney / metabolism*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • PDZ Domains
  • Parathyroid Hormone / metabolism*
  • Phosphates / metabolism*
  • Phosphoproteins / genetics
  • Phosphoproteins / metabolism*
  • Phosphorylation
  • Protein Kinase C / metabolism
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Second Messenger Systems / physiology
  • Serine / metabolism*
  • Sodium / metabolism
  • Sodium-Hydrogen Exchangers / genetics
  • Sodium-Hydrogen Exchangers / metabolism*

Substances

  • Enzyme Inhibitors
  • Parathyroid Hormone
  • Phosphates
  • Phosphoproteins
  • Recombinant Fusion Proteins
  • Sodium-Hydrogen Exchangers
  • sodium-hydrogen exchanger regulatory factor
  • Serine
  • Sodium
  • Cyclic AMP-Dependent Protein Kinases
  • Protein Kinase C