title: Ca2+/calmodulin-dependent protein kinase modulates cardiac ryanodine receptor phosphorylation and sarcoplasmic reticulum Ca2+ leak in heart failure.
abstract: Abnormal release of Ca from sarcoplasmic reticulum (SR) via the cardiac ryanodine receptor (RyR2) may contribute to contractile dysfunction and arrhythmogenesis in heart failure (HF). We previously demonstrated decreased Ca transient amplitude and SR Ca load associated with increased Na/Ca exchanger expression and enhanced diastolic SR Ca leak in an arrhythmogenic rabbit model of nonischemic HF. Here we assessed expression and phosphorylation status of key Ca handling proteins and measured SR Ca leak in control and HF rabbit myocytes. With HF, expression of RyR2 and FK-506 binding protein 12.6 (FKBP12.6) were reduced, whereas inositol trisphosphate receptor (type 2) and Ca/calmodulin-dependent protein kinase II (CaMKII) expression were increased 50% to 100%. The RyR2 complex included more CaMKII (which was more activated) but less calmodulin, FKBP12.6, and phosphatases 1 and 2A. The RyR2 was more highly phosphorylated by both protein kinase A (PKA) and CaMKII. Total phospholamban phosphorylation was unaltered, although it was reduced at the PKA site and increased at the CaMKII site. SR Ca leak in intact HF myocytes (which is higher than in control) was reduced by inhibition of CaMKII but was unaltered by PKA inhibition. CaMKII inhibition also increased SR Ca content in HF myocytes. Our results suggest that CaMKII-dependent phosphorylation of RyR2 is involved in enhanced SR diastolic Ca leak and reduced SR Ca load in HF, and may thus contribute to arrhythmias and contractile dysfunction in HF.
authors.affiliation: Department of Medicine, University of Illinois at Chicago, IL 60612, USA.
authors.forename: Xun
authors.initials: X
authors.lastname: Ai
authors.forename: Jerry W
authors.initials: JW
authors.lastname: Curran
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Shannon
authors.forename: Donald M
authors.initials: DM
authors.lastname: Bers
authors.forename: Steven M
authors.initials: SM
authors.lastname: Pogwizd
mesh_terms: D000818:Animals; D001145:Arrhythmias, Cardiac / Q000209:etiology; D001596:Benzylamines / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000235:genetics; D002135:Calcium-Binding Proteins / Q000378:metabolism; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000502:physiology*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology; D004452:Echocardiography; D006333:Heart Failure / Q000378:metabolism*; D053496:Inositol 1,4,5-Trisphosphate Receptors; D032383:Myocytes, Cardiac / Q000378:metabolism; D010766:Phosphorylation; D011817:Rabbits; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics / Q000378:metabolism*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D013449:Sulfonamides / Q000494:pharmacology; D022061:Tacrolimus Binding Protein 1A / Q000032:analysis; D022021:Tacrolimus Binding Proteins / Q000032:analysis; D000099211:Phospholamban; D000096926:Benzenesulfonamides
chemical_list: D001596:Benzylamines; D002118:Calcium; D015220:Calcium Channels; D002135:Calcium-Binding Proteins; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D000252:Calcium-Transporting ATPases; D017868:Cyclic AMP-Dependent Protein Kinases; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D019837:Ryanodine Receptor Calcium Release Channel; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D013449:Sulfonamides; D022061:Tacrolimus Binding Protein 1A; D022021:Tacrolimus Binding Proteins; D000099211:Phospholamban; C072105:KN 93; D000096926:Benzenesulfonamides; C403484:tacrolimus binding protein 1B