HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Supplemental Figures All Versions of this Article: 297/2/H846    most recent 01231.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Coccaro, E. Articles by Fliegel, L. PubMed PubMed Citation Articles by Coccaro, E. Articles by Fliegel, L.

Phenylephrine and sustained acidosis activate the neonatal rat cardiomyocyte Na⁺/H⁺ exchanger through phosphorylation of amino acids Ser⁷⁷⁰ and Ser⁷⁷¹

Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada

Submitted 24 November 2008 ; accepted in final form 15 June 2009

The mammalian Na⁺/H⁺ exchanger isoform 1 (NHE1) is a ubiquitously expressed membrane protein that regulates intracellular pH in the myocardium. NHE1 is also important in mediating myocardial hypertrophy, and the blockage of NHE1 activity prevents hypertrophy and reduces ischemia-reperfusion injury in animal models. We recently demonstrated that extracellular-regulated kinase (ERK)-mediated activation of NHE1 occurs during ischemia-reperfusion of the myocardium. To understand the regulation of NHE1 in the myocardium by phosphorylation, we expressed a series of adenoviruses that express wild-type and mutant cDNA for NHE1. All exogenous cDNA for NHE1 had additional mutations [Leu¹⁶³Phe/Gly¹⁷⁴Ser], which increases NHE1 resistance to EMD-87580 (a specific blocker of NHE1) 100-fold, and allowed the measurement of exogenous NHE1 while inhibiting endogenous NHE1. By examining the effects of a series of mutations of the NHE1 cytosolic region, we determined that the amino acids Ser⁷⁷⁰ and Ser⁷⁷¹ were essential for the acute activation of NHE1 activity in rat cardiomyocytes. The specific mutation of either residue prevented the rapid activation of exchanger activity by a sustained intracellular acidosis through ERK-dependent pathways. The same amino acids were critical to phenylephrine-mediated, ERK-dependent activation of NHE1 activity and increased the phosphorylation in intact rat cardiomyocytes. The results demonstrate that both sustained intracellular acidosis and phenylephrine rapidly activate the NHE1 protein in intact cardiac cells through ERK-dependent pathways that act on a common pathway mediated by amino acids Ser⁷⁷⁰ and Ser⁷⁷¹ of the cytosolic tail of the protein.

extracellular-regulated kinases-1/2; ischemia-reperfusion; sodium-hydrogen exchanger