p90(RSK) is a serum-stimulated Na+/H+ exchanger isoform-1 kinase. Regulatory phosphorylation of serine 703 of Na+/H+ exchanger isoform-1.
The Na+/H+ exchanger isoform-1 (NHE-1) is the key member of a family of exchangers that regulates intracellular pH and cell volume. Activation of NHE-1 by growth factors is rapid, correlates with increased NHE-1 phosphorylation and cell alkalinization, and plays a role in cell cycle progression. By two-dimensional tryptic peptide mapping of immunoprecipitated NHE-1, we identify serine 703 as the major serum-stimulated amino acid. Mutation of serine 703 to alanine had no effect on acid-stimulated Na+/H+ exchange but completely prevented the growth factor-mediated increase in NHE-1 affinity for H+. In addition, we show that p90 ribosomal S6 kinase (p90(RSK)) is a key NHE-1 kinase since p90(RSK) phosphorylates NHE-1 serine 703 stoichiometrically in vitro, and transfection with kinase-inactive p90(RSK) inhibits serum-induced phosphorylation of NHE-1 serine 703 in transfected 293 cells. These findings establish p90(RSK) as a serum-stimulated NHE-1 kinase and a mediator of increased Na+/H+ exchange in vivo.
Takahashi
E
E
Departments of Medicine, University of Washington, Seattle, Washington 98195, USA.
Abe
J
J
Gallis
B
B
Aebersold
R
R
Spring
D J
DJ
Krebs
E G
EG
Berk
B C
BC
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001769:Blood; D002478:Cells, Cultured; D017931:DNA Primers; D018076:DNA, Complementary; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D048369:MAP Kinase Kinase 1; D008297:Male; D020929:Mitogen-Activated Protein Kinase Kinases; D016297:Mutagenesis, Site-Directed; D010449:Peptide Mapping; D010766:Phosphorylation; D011233:Precipitin Tests; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley; D019893:Ribosomal Protein S6 Kinases / Q000235:genetics / Q000378:metabolism*; D012694:Serine / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013917:Thrombin / Q000494:pharmacology; D014162:Transfection
D017931:DNA Primers; D018076:DNA, Complementary; D004791:Enzyme Inhibitors; D005419:Flavonoids; D020033:Protein Isoforms; D017923:Sodium-Hydrogen Exchangers; C069139:growth factor-activatable Na-H exchanger NHE-1; D012694:Serine; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D019893:Ribosomal Protein S6 Kinases; D048369:MAP Kinase Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases; D013917:Thrombin; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one