Ca2+/calmodulin kinase II-dependent phosphorylation of ryanodine receptors suppresses Ca2+ sparks and Ca2+ waves in cardiac myocytes.
The multifunctional Ca(2+)/calmodulin-dependent protein kinase II delta(C) (CaMKIIdelta(C)) is found in the macromolecular complex of type 2 ryanodine receptor (RyR2) Ca(2+) release channels in the heart. However, the functional role of CaMKII-dependent phosphorylation of RyR2 is highly controversial. To address this issue, we expressed wild-type, constitutively active, or dominant-negative CaMKIIdelta(C) via adenoviral gene transfer in cultured adult rat ventricular myocytes. CaMKII-mediated phosphorylation of RyR2 was reduced, enhanced, or unaltered by dominant-negative, constitutively active, or wild-type CaMKIIdelta(C) expression, whereas phosphorylation of phospholamban at Thr17, an endogenous indicator of CaMKII activity, was at 73%, 161%, or 115% of the control group expressing beta-galactosidase (beta-gal), respectively. In parallel with the phospholamban phosphorylation, the decay kinetics of global Ca(2+) transients was slowed, accelerated, or unchanged, whereas spontaneous Ca(2+) spark activity was hyperactive, depressed, or unchanged in dominant-negative, constitutively active, or wild-type CaMKIIdelta(C) groups, respectively. When challenged by high extracellular Ca(2+), both wild-type and constitutively active CaMKIIdelta(C) protected the cells from store overload-induced Ca(2+) release, manifested by a approximately 60% suppression of Ca(2+) waves (at 2 to 20 mmol/L extracellular Ca(2+)) in spite of an elevated sarcoplasmic reticulum Ca(2+) content, whereas dominant-negative CaMKIIdelta(C) promoted Ca(2+) wave production (at 20 mmol/L Ca(2+)) with significantly depleted sarcoplasmic reticulum Ca(2+). Taken together, our data support the notion that CaMKIIdelta(C) negatively regulates RyR2 activity and spontaneous sarcoplasmic reticulum Ca(2+) release, thereby affording a negative feedback that stabilizes local and global Ca(2+)-induced Ca(2+) release in the heart.
Yang
Dongmei
D
Laboratory of Cardiovascular Science, National Institute on Aging, NIH, Baltimore, MD 21224, USA.
Zhu
Wei-Zhong
WZ
Xiao
Bailong
B
Brochet
Didier X P
DX
Chen
S R Wayne
SR
Lakatta
Edward G
EG
Xiao
Rui-Ping
RP
Cheng
Heping
H
D000200:Action Potentials; D000222:Adaptation, Physiological; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology*; D002147:Calmodulin / Q000378:metabolism; D002478:Cells, Cultured / Q000378:metabolism; D005799:Genes, Dominant; D007527:Isoenzymes / Q000502:physiology; D008955:Models, Cardiovascular; D016297:Mutagenesis, Site-Directed; D009200:Myocardial Contraction / Q000502:physiology*; D032383:Myocytes, Cardiac / Q000378:metabolism*; D010766:Phosphorylation; D051745:Protein Kinase C-delta / Q000235:genetics / Q000502:physiology*; D011499:Protein Processing, Post-Translational / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000502:physiology; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism
D002147:Calmodulin; D007527:Isoenzymes; D011993:Recombinant Fusion Proteins; D019837:Ryanodine Receptor Calcium Release Channel; C497260:Prkcd protein, rat; D051745:Protein Kinase C-delta; D002118:Calcium