title: NO-dependent CaMKII activation during β-adrenergic stimulation of cardiac muscle.
abstract: OBJECTIVE
  During β-adrenergic receptor (β-AR) stimulation, phosphorylation of cardiomyocyte ryanodine receptors by protein kinases may contribute to an increased diastolic Ca(2+) spark frequency. Regardless of prompt activation of protein kinase A during β-AR stimulation, this appears to rely more on activation of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII), by a not yet identified signalling pathway. The goal of the present study was to identify and characterize the mechanisms which lead to CaMKII activation and elevated Ca(2+) spark frequencies during β-AR stimulation in single cardiomyocytes in diastolic conditions.
  
  
  RESULTS
  Confocal imaging revealed that β-AR stimulation increases endogenous NO production in cardiomyocytes, resulting in NO-dependent activation of CaMKII and a subsequent increase in diastolic Ca(2+) spark frequency. These changes of spark frequency could be mimicked by exposure to the NO donor GSNO and were sensitive to the CaMKII inhibitors KN-93 and AIP. In vitro, CaMKII became nitrosated and its activity remained increased independent of Ca(2+) in the presence of GSNO, as assessed with biochemical assays.
  
  
  CONCLUSIONS
  β-AR stimulation of cardiomyocytes may activate CaMKII by a novel direct pathway involving NO, without requiring Ca(2+) transients. This crosstalk between two established signalling pathways may contribute to arrhythmogenic diastolic Ca(2+) release and Ca(2+) waves during adrenergic stress, particularly in combination with cardiac diseases. In addition, NO-dependent activation of CaMKII is likely to have repercussions in many cellular signalling systems and cell types.
authors: Department of Physiology, University of Bern, Bühlplatz 5, CH-3012 Bern, Switzerland.
authors: Daniel A
authors: DA
authors: Gutierrez
authors: Miguel
authors: M
authors: Fernandez-Tenorio
authors: Jakob
authors: J
authors: Ogrodnik
authors: Ernst
authors: E
authors: Niggli
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000201:enzymology / Q000503:physiopathology; D020013:Calcium Signaling / Q000187:drug effects; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D003971:Diastole; D004789:Enzyme Activation; D006168:Guinea Pigs; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000201:enzymology; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D013997:Time Factors; D015854:Up-Regulation
chemical_list: D000318:Adrenergic beta-Agonists; D020030:Nitric Oxide Donors; D047428:Protein Kinase Inhibitors; D009569:Nitric Oxide; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2
keywords: Ca sparks; Ca waves; CaMKII; NO-synthase