Ischemia-induced phosphorylation of phospholemman directly activates rat cardiac Na/K ATPase

William Fuller, Philip Eaton, James R. Bell, Michael J. Shattock

    Research output: Contribution to journalArticle

    89 Citations (Scopus)

    Abstract

    Regulation of the Na/K ATPase by protein kinases is model-specific. We have observed a profound activation of the sarcolemmal Na/K ATPase during cardiac ischemia, which is masked by an inhibitor of the enzyme in the cytosol. The aim of these studies was to characterize the pathways involved in this activation in the Langendorff-perfused rat heart. Na/K ATPase activity was determined by measuring ouabain-sensitive phosphate generation by cardiac homogenates at 37 degrees C. In isolated sarcolemma, ischemia (30 min) caused a substantial activation of the Na/K ATPase compared with aerobic controls, which was abolished by perfusing the heart with staurosporine or H89. However, the alpha1 subunit of the Na/K ATPase was not phosphorylated during ischemia. The sarcolemmal protein phospholemman (PLM) was found associated with the Na/K ATPase alpha1 and beta1 but not alpha2 subunits, and PLM increased its association with the catalytic subunit of PKA following ischemia. In vitro 14-3-3 binding assays indicated that PLM was phosphorylated following ischemia. These results indicate that the ischemia-induced activation of the Na/K ATPase is indirect, through phosphorylation of PLM, which is an integral part of the Na/K ATPase enzyme complex in the heart. The role of PLM is analogous to phospholamban in regulating the sarcoplasmic reticulum calcium ATPase. staurosporine or H89. However, the a1 subunit of the Na/K ATPase was not phosphorylated during ischemia. The sarcolemmal protein phospholemman (PLM) was found associated with the Na/K ATPase a1 and ß1 but not a2 subunits, and PLM increased its association with the catalytic subunit of PKA following ischemia. In vitro 14-3-3 binding assays indicated that PLM was phosphorylated following ischemia. These results indicate that the ischemia-induced activation of the Na/K ATPase is indirect, through phosphorylation of PLM, which is an integral part of the Na/K ATPase enzyme complex in the heart. The role of PLM is analogous to phospholamban in regulating the sarcoplasmic reticulum calcium ATPase.
    Original languageEnglish
    Pages (from-to)197-199
    Number of pages3
    JournalFASEB Journal
    Volume18
    Issue number1
    DOIs
    Publication statusPublished - Jan 2004

    Keywords

    • Ischemia
    • Phospholemman
    • Protein kinase
    • Isolated heart
    • Phosphorylation

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