title: Beta-adrenergic enhancement of sarcoplasmic reticulum calcium leak in cardiac myocytes is mediated by calcium/calmodulin-dependent protein kinase.
abstract: Enhanced cardiac diastolic Ca leak from the sarcoplasmic reticulum (SR) ryanodine receptor may reduce SR Ca content and contribute to arrhythmogenesis. We tested whether beta-adrenergic receptor (beta-AR) agonists increased SR Ca leak in intact rabbit ventricular myocytes and whether this depends on protein kinase A or Ca/calmodulin-dependent protein kinase II (CaMKII) activity. SR Ca leak was assessed by acute block of the ryanodine receptor by tetracaine and assessment of the consequent shift of Ca from cytosol to SR (measured at various SR Ca loads induced by varying frequency). Cytosolic [Ca] ([Ca](i)) and SR Ca load ([Ca](SRT)) were assessed using fluo-4. beta-AR activation by isoproterenol dramatically increased SR Ca leak. However, this effect was not inhibited by blocking protein kinase A by H-89, despite the expected reversal of the isoproterenol-induced enhancement of Ca transient amplitude and [Ca](i) decline rate. In contrast, inhibitors of CaMKII, KN-93, or autocamtide-2-related inhibitory peptide II or beta-AR blockade reversed the isoproterenol-induced enhancement of SR Ca leak, and CaMKII inhibition could even reduce leak below control levels. Forskolin, which bypasses the beta-AR in activating adenylate cyclase and protein kinase A, did not increase SR Ca leak, despite robust enhancement of Ca transient amplitude and [Ca](i) decline rate. The results suggest that beta-AR stimulation enhances diastolic SR Ca leak in a manner that is (1) CaMKII dependent, (2) not protein kinase A dependent, and 3) not dependent on bulk [Ca](i).
authors.affiliation: Rush University Medical Center, Chicago, IL 60611, USA.
authors.forename: Jerald
authors.initials: J
authors.lastname: Curran
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Hinton
authors.forename: Eduardo
authors.initials: E
authors.lastname: Ríos
authors.forename: Donald M
authors.initials: DM
authors.lastname: Bers
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Shannon
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D001596:Benzylamines / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000502:physiology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D002147:Calmodulin / Q000502:physiology; D002478:Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D003971:Diastole; D006333:Heart Failure / Q000209:etiology; D007545:Isoproterenol / Q000494:pharmacology*; D007546:Isoquinolines / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology*; D009206:Myocardium / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism; D010455:Peptides / Q000494:pharmacology; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational / Q000502:physiology*; D011817:Rabbits; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology*; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013449:Sulfonamides / Q000494:pharmacology; D013748:Tetracaine / Q000494:pharmacology; D000096926:Benzenesulfonamides
chemical_list: D000318:Adrenergic beta-Agonists; D001596:Benzylamines; D002118:Calcium; D020746:Calcium Channels, L-Type; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002147:Calmodulin; D005576:Colforsin; D017868:Cyclic AMP-Dependent Protein Kinases; D007545:Isoproterenol; D007546:Isoquinolines; D010455:Peptides; D011943:Receptors, Adrenergic, beta; D019837:Ryanodine Receptor Calcium Release Channel; D013449:Sulfonamides; D013748:Tetracaine; C085903:autocamtide-2; C072105:KN 93; D000096926:Benzenesulfonamides; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide