Na,K-ATPase alpha1-subunit dephosphorylation by protein phosphatase 2A is necessary for its recruitment to the plasma membrane

FASEB J. 2006 Dec;20(14):2618-20. doi: 10.1096/fj.06-6503fje. Epub 2006 Oct 25.

Abstract

In alveolar epithelial cells, G-protein coupled-receptors agonists (GPCR) induce the recruitment of the Na,K-ATPase to the plasma membrane. Here we report that for the recruitment of the Na,K-ATPase to occur, dephosphorylation of its alpha1-subunit at serine 18 is necessary, as demonstrated by in vitro phosphorylation, mutation of the serine 18 to alanine, and use of a specific phospho-antibody. Several approaches strongly suggest dephosphorylation to be mediated by protein phosphatase 2A (PP2A): 1) Na,K-ATPase dephosphorylation and recruitment were prevented by okadaic acid (OA); 2) the Na,K-ATPase alpha1-subunit is an in vitro substrate for PP2A; and 3) glutathione S-transferase (GST)-fusion proteins binding assays demonstrate a direct interaction between the catalytic subunit of PP2A and the first 90 amino acids of the Na,K-ATPase alpha1-subunit. Finally, GPCR agonists induced a rapid translocation of PP2A from the cytosol to the membrane fraction, which corresponded with increased coimmunoprecipitation and colocalization of PP2A and the Na,K-ATPase. Accordingly, we provide evidence that GPCR agonists promote PP2A translocation to the membrane fraction, leading to the dephosphorylation of the Na,K-ATPase alpha1-subunit at the serine 18 residue and its recruitment to the cell plasma membrane, which is of biological and physiological importance.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Cell Line
  • Epithelial Cells / metabolism
  • Humans
  • Male
  • Phosphoprotein Phosphatases / metabolism*
  • Protein Phosphatase 2
  • Protein Subunits
  • Protein Transport / physiology
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, G-Protein-Coupled / agonists
  • Sodium-Potassium-Exchanging ATPase / metabolism*

Substances

  • Protein Subunits
  • Receptors, G-Protein-Coupled
  • Phosphoprotein Phosphatases
  • Protein Phosphatase 2
  • Sodium-Potassium-Exchanging ATPase