Phospholemman expression is high in the newborn rabbit heart and declines with postnatal maturation

Abstract

Phospholemman (PLM) is a small sarcolemmal protein that modulates the activities of Na +/K +-ATPase and the Na +/Ca 2+ exchanger (NCX), thus contributing to the maintenance of intracellular Na + and Ca 2+ homeostasis. We characterized the expression and subcellular localization of PLM, NCX, and the Na +/K +-ATPase α1-subunit during perinatal development. Western blotting demonstrates that PLM (15 kDa), NCX (120 kDa), and Na +/K +-ATPase α-1 (∼100 kDa) proteins are all more than 2-fold higher in ventricular membrane fractions from newborn rabbit hearts (1–4-day old) compared to adult hearts. Our immunocytochemistry data demonstrate that PLM, NCX, and Na +/K +-ATPase are all expressed at the sarcolemma of newborn ventricular myocytes. Taken together, our data indicate that PLM, NCX, and Na +/K +-ATPase α-1 proteins have similar developmental expression patterns in rabbit ventricular myocardium. Thus, PLM may have an important regulatory role in maintaining cardiac Na + and Ca 2+ homeostasis during perinatal maturation.