Phosphorylation and activation of the plasma membrane Na +/H + exchanger (NHE1) during osmotic cell shrinkage

Robert R. Rigor, Catalina Damoc, Brett S. Phinney, Peter M Cala

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

The Na +/H + Exchanger isoform 1 (NHE1) is a highly versatile, broadly distributed and precisely controlled transport protein that mediates volume and pH regulation in most cell types. NHE1 phosphorylation contributes to Na +/H + exchange activity in response to phorbol esters, growth factors or protein phosphatase inhibitors, but has not been observed during activation by osmotic cell shrinkage (OCS). We examined the role of NHE1 phosphorylation during activation by OCS, using an ideal model system, the Amphiuma tridactylum red blood cell (atRBC). Na +/H + exchange in atRBCs is mediated by an NHE1 homolog (atNHE1) that is 79% identical to human NHE1 at the amino acid level. NHE1 activity in atRBCs is exceptionally robust in that transport activity can increase more than 2 orders of magnitude from rest to full activation. Michaelis-Menten transport kinetics indicates that either OCS or treatment with the phosphatase inhibitor calyculin-A (CLA) increase Na + transport capacity without affecting transport affinity (K m = 44 mM) in atRBCs. CLA and OCS act non-additively to activate atNHE1, indicating convergent, phosphorylation-dependent signaling in atNHE1 activation. In situ 32P labeling and immunoprecipitation demonstrates that the net phosphorylation of atNHE1 is increased 4-fold during OCS coinciding with a more than 2-order increase in Na + transport activity. This is the first reported evidence of increased NHE1 phosphorylation during OCS in any vertebrate cell type. Finally, liquid chromatography and mass spectrometry (LC-MS/MS) analysis of atNHE1 immunoprecipitated from atRBC membranes reveals 9 phosphorylated serine/threonine residues, suggesting that activation of atNHE1 involves multiple phosphorylation and/or dephosphorylation events.

Original languageEnglish (US)
Article numbere29210
JournalPLoS One
Volume6
Issue number12
DOIs
StatePublished - Dec 28 2011

Fingerprint

Sodium-Hydrogen Antiporter
Phosphorylation
Cell membranes
shrinkage
phosphorylation
Protein Isoforms
plasma membrane
Chemical activation
Cell Membrane
cells
Urodela
Blood
erythrocytes
Erythrocytes
Phosphoprotein Phosphatases
Liquid chromatography
Phorbol Esters
Threonine
sodium-hydrogen antiporter
dephosphorylation

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Medicine(all)

Cite this

Phosphorylation and activation of the plasma membrane Na +/H + exchanger (NHE1) during osmotic cell shrinkage. / Rigor, Robert R.; Damoc, Catalina; Phinney, Brett S.; Cala, Peter M.

In: PLoS One, Vol. 6, No. 12, e29210, 28.12.2011.

Research output: Contribution to journalArticle

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