Phosphorylation of phospholamban at threonine-17 in the absence and presence of beta-adrenergic stimulation in neonatal rat cardiomyocytes

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Item Type:	Article
Title:	Phosphorylation of phospholamban at threonine-17 in the absence and presence of beta-adrenergic stimulation in neonatal rat cardiomyocytes
Creators Name:	Bartel, S., Vetter, D., Schlegel, W.P., Wallukat, G., Krause, E.G. and Karczewski, P.
Abstract:	The site-specific phospholamban phosphorylation was studied with respect to the interplay of cAMP- and Ca2+ signaling in neonatal rat cardiomyocytes. To elucidate the signal pathway(s) for the activation of Ca2+/calmodulin-dependent protein kinase (CaMKII) we studied Thr17 phosphorylation of phospholamban in dependence of Ca2+ channel activation by S(-)-Bay K8644 and in dependence of the depletion of the sarcoplasmic reticulum Ca2+ stores by ryanodine or thapsigargin in the absence or presence of β-adrenergic stimulation. The isoproterenol (0.1 μM)-induced Thr17 phosphorylation was potentiated 2.5-fold in presence of 1 μM S(-)-Bay K8644. Interestingly, S(-)-Bay K8644 alone was also able to induce Thr17 phosphorylation in a dose- and time-dependent fashion. Ryanodine (1.0 μM) reduced both the isoproterenol (0.1 μM) and S(-)-Bay K8644-(1 μM) mediated Thr17 phosphorylation by about 90%. Thapsigargin (1 μM) diminished the S(-)-Bay K8644 and isoproterenol-associated Thr17 phosphorylation by 53.5 ± 6.3% and 92.5 ± 11.1%, respectively. Ser16 phosphorylation was not affected under these conditions. KN-93 reduced the Thr17 phosphorylation by S(-)-Bay K8644 and isoproterenol to levels of 1.1 ± 0.3% and 8,6 ± 2.1%, respectively. However, the effect of KN-93 was attenuated (47.8 ± 3.6%) in isoproterenoi prestimulated cells. Protein phosphatase inhibition by okadaic acid increased exclusively the Ser16 phosphorylation. In summary, our results reflect a crosstalk between β-adrenoceptor stimulation and intracellular Ca2+ at the level of CaMKII-mediated phospholamban phosphorylation in neonatal rat cardiomyocytes. We report conditions which exclusively produce Thr17 or Ser16 phosphorylation. We postulate that Ca2+ transport systems of the sarcoplasmic reticulum are critical determinants for the activation of CaMKII that catalyzes phosphorylation of phospholamban.
Keywords:	{Beta}-Adrenoceptor, Cross-Talk, L-Type Ca2+ Channel, Phospholamban, Animals, Rats
Source:	Journal of Molecular and Cellular Cardiology
ISSN:	0022-2828
Publisher:	Elsevier
Volume:	32
Number:	12
Page Range:	2173-2185
Date:	1 January 2000
Official Publication:	https://doi.org/10.1006/jmcc.2000.1243
PubMed:	View item in PubMed

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