Specific role of neuronal nitric-oxide synthase when tethered to the plasma membrane calcium pump in regulating the beta-adrenergic signal in the myocardium

Tamer M A Mohamed, Delvac Oceandy, Sukhpal Prehar, Nasser Alatwi, Zeinab Hegab, Florence M Baudoin, Adam Pickard, Aly O Zaki, Raja Nadif, Elizabeth J Cartwright, Ludwig Neyses

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25 Citations (Scopus)


The cardiac neuronal nitric-oxide synthase (nNOS) has been described as a modulator of cardiac contractility. We have demonstrated previously that isoform 4b of the sarcolemmal calcium pump (PMCA4b) binds to nNOS in the heart and that this complex regulates beta-adrenergic signal transmission in vivo. Here, we investigated whether the nNOS-PMCA4b complex serves as a specific signaling modulator in the heart. PMCA4b transgenic mice (PMCA4b-TG) showed a significant reduction in nNOS and total NOS activities as well as in cGMP levels in the heart compared with their wild type (WT) littermates. In contrast, PMCA4b-TG hearts showed an elevation in cAMP levels compared with the WT. Adult cardiomyocytes isolated from PMCA4b-TG mice demonstrated a 3-fold increase in Ser(16) phospholamban (PLB) phosphorylation as well as Ser(22) and Ser(23) cardiac troponin I (cTnI) phosphorylation at base line compared with the WT. In addition, the relative induction of PLB phosphorylation and cTnI phosphorylation following isoproterenol treatment was severely reduced in PMCA4b-TG myocytes, explaining the blunted physiological response to the beta-adrenergic stimulation. In keeping with the data from the transgenic animals, neonatal rat cardiomyocytes overexpressing PMCA4b showed a significant reduction in nitric oxide and cGMP levels. This was accompanied by an increase in cAMP levels, which led to an increase in both PLB and cTnI phosphorylation at base line. Elevated cAMP levels were likely due to the modulation of cardiac phosphodiesterase, which determined the balance between cGMP and cAMP following PMCA4b overexpression. In conclusion, these results showed that the nNOS-PMCA4b complex regulates contractility via cAMP and phosphorylation of both PLB and cTnI.

Original languageEnglish
Pages (from-to)12091-8
Number of pages8
JournalThe Journal of Biological Chemistry
Issue number18
Publication statusPublished - 01 May 2009


  • Animals
  • Calcium-Binding Proteins
  • Cells, Cultured
  • Cyclic AMP
  • Cyclic GMP
  • Mice
  • Mice, Transgenic
  • Multienzyme Complexes
  • Myocardium
  • Myocytes, Cardiac
  • Nitric Oxide
  • Nitric Oxide Synthase Type I
  • Phosphoric Diester Hydrolases
  • Plasma Membrane Calcium-Transporting ATPases
  • Rats
  • Rats, Sprague-Dawley
  • Signal Transduction
  • Troponin I


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