CaMKIIδB Mediates Aberrant NCX1 Expression and the Imbalance of NCX1/SERCA in Transverse Aortic Constriction-Induced Failing Heart

Ying-Mei Lu,Norifumi Shioda,Yasufumi Shirasaki,Kohji Fukunaga,Feng Han,Jiyun Huang,Xiao-Ming Li,Robert E Means

doi:10.1371/journal.pone.0024724

Ying-Mei Lu, Norifumi Shioda + Show 6 more

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https://doi.org/10.1371/journal.pone.0024724

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Abstract

Ca2+/calmodulin-dependent protein kinase II δB (CaMKIIδB) is one of the predominant isoforms of CaMKII in the heart. The precise role of CaMKIIδB in the transcriptional cross-talk of Ca2+-handling proteins during heart failure remains unclear. In this work, we aim to determine the mechanism of CaMKIIδB in modulating the expression of sarcolemmal Na+–Ca2+ exchange (NCX1). We also aim to address the potential effects of calmodulin antagonism on the imbalance of NCX1 and sarcoendoplasmic reticulum Ca2+ ATPase (SERCA) during heart failure. Eight weeks after transverse aortic constriction (TAC)-induced heart failure in mice, we found that the heart weight/tibia length (HW/TL) ratio and the lung weight/body weight (LW/BW) ratio increased by 59% and 133%, respectively. We further found that the left ventricle-shortening fraction decreased by 40% compared with the sham-operated controls. Immunoblotting revealed that the phosphorylation of CaMKIIδB significantly increased 8 weeks after TAC-induced heart failure. NCX1 protein levels were also elevated, whereas SERCA2 protein levels decreased in the same animal model. Moreover, transfection of active CaMKIIδB significantly increased NCX1 protein levels in adult mouse cardiomyocytes via class IIa histone deacetylase (HDAC)/myocyte enhancer factor-2 (MEF2)-dependent signaling. In addition, pharmacological inhibition of calmodulin/CaMKIIδB activity improved cardiac function in TAC mice, which partially normalized the imbalance between NCX1 and SERCA2. These data identify NCX1 as a cellular target for CaMKIIδB. We also suggest that the CaMKIIδB-induced imbalance between NCX1 and SERCA2 is partially responsible for the disturbance of intracellular Ca2+ homeostasis and the pathological process of heart failure.

Highlights

Ca2+/calmodulin-dependent protein kinase II (CaMKII) is involved in the development of cardiac hypertrophy and heart failure
Consistent with this idea, our results demonstrate that the expression levels of sarcoendoplasmic reticulum Ca2+-ATPase (SERCA2) and NCX1 were changed, but in opposite directions, following transverse aortic constriction (TAC) treatment
The dual staining of NCX1 and troponinT confirmed that both of these proteins are present at the same location in rat cardiomyocytes, in addition, increased expression of NCX1 was observed in TAC mice (Fig. 1C)

Summary

Introduction

Ca2+/calmodulin-dependent protein kinase II (CaMKII) is involved in the development of cardiac hypertrophy and heart failure. Predominant expression of the CaMKIId isoform contributes to cardiac decompensation by enhancing the ryanodine receptor (RyR)-mediated sarcoplasmic reticulum (SR) Ca2+ leak, and attenuating CaMKIId activation has been shown to limit the progression to heart failure [1,2]. As one of the two primary splicing variants of the d isoform in the heart of many mammals, CaMKIIdB localizes to the nucleus and is predicted to play a predominant role in Ca2+mediated transcriptional gene regulation. The over-expression of CaMKIIdB in transgenic mice has been shown to induce hypertrophy-related gene expression and result in cardiac hypertrophy [5,6]. Little is known about the relationship between aberrant CaMKIIdB expression and the cross talk of Ca2+-handling proteins during heart failure

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