Protein Kinase Mediated Regulation of the Na+/H+ Exchanger in the Rat Myocardium by MAP-Kinase-dependent Pathways

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  • We examined regulation of the Na+/H+ exchanger isoform 1 by phosphorylation in the rat myocardium. We utilized cell extracts from adult rat hearts, adult rat extracts fractionated by fast performance liquid chromatography, and extracts from cultured neonatal cardiac myocytes. The carboxyl-terminal 178 amino acids of the Na+/H+ exchanger were expressed inEscherichia coli fused with glutathioneS-transferase. The purified protein was used as a substrate for in vitro phosphorylation and in-gel kinase assays. Unfractionated extracts from neonatal myocytes or adult hearts phosphorylated the COOH-terminal domain of the antiporter. Western blot analysis revealed that mitogen-activated protein (MAP) kinase (44 and 42 kDa) and p90rsk (90 kDa) were present in specific fractions of cardiac extracts that phosphorylated the COOH-terminal protein. In-gel kinase assays confirmed that protein kinases of approximately 44 and 90 kDa could phosphorylate this domain. MAP kinase and p90rsk-dependent phosphorylation of the antiporter could be demonstrated by immunoprecipitation of these kinases from extracts of neonatal cardiac myocytes. PD98059, a mitogen-activated protein kinase kinase inhibitor, decreased MAP kinase and p90rsk phosphorylation of the antiporter and abolished serum and endothelin 1-stimulated increases in steady-state pHi. These results confirm the presence of MAP kinase-dependent phosphorylation in the regulation of the Na+/H+exchanger in the rat myocardium and suggest an important role for p90rsk phosphorylation in regulation of the protein by endothelin-mediated stimulation of the antiporter.

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    Article (Published)
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    Attribution 4.0 International
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    • Moor, Andrea Noor, & Fliegel, Larry. (1999). Protein Kinase Mediated Regulation of the Na+/H+ Exchanger in the Rat Myocardium by MAP-Kinase-dependent Pathways. Journal of Biological Chemistry, 274(33), 22985-22992.
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