CaMKIIdelta isoforms differentially affect calcium handling but similarly regulate HDAC/MEF2 transcriptional responses.
The delta(B) and delta(C) splice variants of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII), which differ by the presence of a nuclear localization sequence, are both expressed in cardiomyocytes. We used transgenic (TG) mice and CaMKII expression in cardiomyocytes to test the hypothesis that the CaMKIIdelta(C) isoform regulates cytosolic Ca(2+) handling and the delta(B) isoform, which localizes to the nucleus, regulates gene transcription. Phosphorylation of CaMKII sites on the ryanodine receptor (RyR) and on phospholamban (PLB) were increased in CaMKIIdelta(C) TG. This was associated with markedly enhanced sarcoplasmic reticulum (SR) Ca(2+) spark frequency and decreased SR Ca(2+) content in cardiomyocytes. None of these parameters were altered in TG mice expressing the nuclear-targeted CaMKIIdelta(B). In contrast, cardiac expression of either CaMKIIdelta(B) or delta(C) induced transactivation of myocyte enhancer factor 2 (MEF2) gene expression and up-regulated hypertrophic marker genes. Studies using rat ventricular cardiomyocytes confirmed that CaMKIIdelta(B) and delta(C) both regulate MEF2-luciferase gene expression, increase histone deacetylase 4 (HDAC4) association with 14-3-3, and induce HDAC4 translocation from nucleus to cytoplasm, indicating that either isoform can stimulate HDAC4 phosphorylation. Finally, HDAC4 kinase activity was shown to be increased in cardiac homogenates from either CaMKIIdelta(B) or delta(C) TG mice. Thus CaMKIIdelta isoforms have similar effects on hypertrophic gene expression but disparate effects on Ca(2+) handling, suggesting distinct roles for CaMKIIdelta isoform activation in the pathogenesis of cardiac hypertrophy versus heart failure.
Zhang
Tong
T
Department of Pharmacology, University of California, San Diego, La Jolla, California 92093-0636, USA. tzhang@arenapharm.com
Kohlhaas
Michael
M
Backs
Johannes
J
Mishra
Shikha
S
Phillips
William
W
Dybkova
Nataliya
N
Chang
Shurong
S
Ling
Haiyun
H
Bers
Donald M
DM
Maier
Lars S
LS
Olson
Eric N
EN
Brown
Joan Heller
JH
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000378:metabolism; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000737:chemistry* / Q000502:physiology; D003600:Cytosol / Q000378:metabolism; D005786:Gene Expression Regulation; D006655:Histone Deacetylases / Q000378:metabolism; D064326:MEF2 Transcription Factors; D051379:Mice; D008822:Mice, Transgenic; D008954:Models, Biological; D009206:Myocardium / Q000378:metabolism; D018006:Myogenic Regulatory Factors / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D020033:Protein Isoforms; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D015854:Up-Regulation; D000099211:Phospholamban
D002118:Calcium; D002135:Calcium-Binding Proteins; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D006655:Histone Deacetylases; D064326:MEF2 Transcription Factors; D018006:Myogenic Regulatory Factors; D020033:Protein Isoforms; D019837:Ryanodine Receptor Calcium Release Channel; D000099211:Phospholamban; C578036:Mef2a protein, mouse; C498618:Hdac5 protein, mouse