Cardioprotection by CaMKII-deltaB is mediated by phosphorylation of heat shock factor 1 and subsequent expression of inducible heat shock protein 70.
BACKGROUND
Ca2+/calmodulin-dependent protein kinase (CaMK)II is a multifunctional kinase involved in vital cellular processes such as Ca(2+) handling and cell fate regulation. In mammalian heart, 2 primary CaMKII isoforms, deltaB and deltaC, localize in nuclear and cytosolic compartments, respectively. Although previous studies have established an essential role of CaMKII-deltaC in cardiomyocyte apoptosis, the functional role of the more abundant isoform, CaMKII-deltaB, remains elusive.


OBJECTIVE
Here, we determined the potential role of CaMKII-deltaB in regulating cardiomyocyte viability and explored the underlying mechanism.


RESULTS
In cultured neonatal rat cardiomyocytes, the expression of CaMKII-deltaB and CaMKII-deltaC was inversely regulated in response to H2O2-induced oxidative stress with a profound reduction of the former and an increase of the later. Similarly, in vivo ischemia/reperfusion (IR) led to an opposite regulation of these CaMKII isoforms in a rat myocardial IR model. Notably, overexpression of CaMKII-deltaB protected cardiomyocytes against oxidative stress-, hypoxia-, and angiotensin II-induced apoptosis, whereas overexpression of its cytosolic counterpart promoted apoptosis. Using cDNA microarray, real-time PCR and Western blotting, we demonstrated that overexpression of CaMKII-deltaB but not CaMKII-deltaC elevated expression of heat shock protein (HSP)70 family members, including inducible (i)HSP70 and its homolog (Hst70). Moreover, overexpression of CaMKII-deltaB led to phosphorylation and activation of heat shock factor (HSF)1, the primary transcription factor responsible for HSP70 gene regulation. Importantly, gene silencing of iHSP70, but not Hst70, abolished CaMKII-deltaB-mediated protective effect, indicating that only iHSP70 was required for CaMKII-deltaB elicited antiapoptotic signaling.


CONCLUSIONS
We conclude that cardiac CaMKII-deltaB and CaMKII-deltaC were inversely regulated in response to oxidative stress and IR injury, and that in contrast to CaMKII-deltaC, CaMKII-deltaB serves as a potent suppressor of cardiomyocyte apoptosis triggered by multiple death-inducing stimuli via phosphorylation of HSF1 and subsequent induction of iHSP70, marking both CaMKII-delta isoforms as promising therapeutic targets for the treatment of ischemic heart disease.
Peng
Wei
W
Institute of Molecular Medicine, Peking University, Beijing, People's Republic of China.
Zhang
Yan
Y
Zheng
Ming
M
Cheng
Heping
H
Zhu
Weizhong
W
Cao
Chun-Mei
CM
Xiao
Rui-Ping
RP
D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis; D002118:Calcium / Q000378:metabolism; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004195:Disease Models, Animal; D005786:Gene Expression Regulation; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis* / Q000235:genetics; D000076249:Heat Shock Transcription Factors; D006861:Hydrogen Peroxide / Q000494:pharmacology; D015428:Myocardial Reperfusion Injury / Q000235:genetics / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000378:metabolism*; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D004268:DNA-Binding Proteins; D018840:HSP70 Heat-Shock Proteins; D000076249:Heat Shock Transcription Factors; C000619709:Hsf1 protein, rat; C490435:Hspa2 protein, rat; D016877:Oxidants; D014157:Transcription Factors; D000804:Angiotensin II; D006861:Hydrogen Peroxide; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D002118:Calcium