a b s t r a c tThe Wnt signaling pathway was identified as crucial mediator of cardiomyocyte hypertrophy. In this study we found that activation of non-canonical Wnt signaling by Wnt5a stimulates protein synthesis and enlargement of cardiomyocyte surface area. These hypertrophic features were inhibited in Dapper-1 (Dpr1) depleted cells. On the molecular level, we observed inhibition of the non-canonical Wnt/planar-cell-polarity (PCP) pathway denoted by reduction of c-jun-n-terminal-kinase (JNK) phosphorylation. Upstream of JNK, increased protein levels of the Wnt/PCP trans-membrane receptor van-Gogh-like-2 (Vangl2) were observed along with an enrichment of Vangl2 in perinuclear located vesicles. The findings suggest that Dpr1 is essential for execution of the Wnt/PCP pathway and regulation of the Vangl2/JNK axis. Depletion of Dpr1 inhibits non-canonical Wnt signaling induced cardiomyocyte hypertrophy by blocking Wnt/PCP signaling. Structured summary of protein interactions:Dpr1 and Vangl2 colocalize by fluorescence microscopy (View interaction)

Abstract-Activation of Wnt signaling results in maladaptive cardiac remodeling and cardiomyopathy. Recently, calcium/ calmodulin-dependent protein kinase II (CaMKII) was reported to be a pivotal participant in myocardial remodeling. Because CaMKII was suggested as a downstream target of noncanonical Wnt signaling, we aimed to elucidate the role of CaMKII in dishevelled-1-induced cardiomyopathy and the mechanisms underlying its function. Dishevelled-1-induced cardiomyopathy was reversed by deletion of neither CaMKIIδ nor CaMKIIγ. Therefore, dishevelled-1-transgenic mice were crossed with CaMKIIδγ double-knockout mice. These mice displayed a normal cardiac phenotype without cardiac hypertrophy, fibrosis, apoptosis, or left ventricular dysfunction. Further mechanistic analyses unveiled that CaMKIIδγ couples noncanonical Wnt signaling to histone deacetylase 4 and myosin enhancer factor 2. Therefore, our findings indicate that the axis, consisting of dishevelled-1, CaMKII, histone deacetylase 4, and myosin enhancer factor 2, is an attractive therapeutic target for prevention of cardiac remodeling and its progression to left ventricular dysfunction. 4 genes (α, β, δ, and γ) that display distinct but overlapping expression patterns. 13 The α and β isoforms are almost exclusively expressed in the brain, whereas the other isoforms are found more ubiquitously. In the heart, CaMKII δ and γ are the predominant CaMKII isoforms, with CaMKIIδ displaying the highest expression level. Upregulation of CaMKII expression and activity is a general characteristic of heart failure in humans and in animal models. 14,15 Although CaMKII is a critical downstream target of dishevelled-1, 16 a functional relationship between these proteins in cardiac remodeling has not been identified to date. In this study, deletion of neither CaMKII δ nor γ reverses dishevelled-1-induced cardiomyopathy. Interestingly, here we found that mice lacking both CaMKII δ and γ isoforms are resistant to dishevelled-1-induced cardiac hypertrophy, fibrosis, and LV dysfunction, which is mediated by the histone deacetylase 4/myosin enhancer factor 2 (HDAC4/MEF2) complex. Therefore, this investigation suggests that both the δ and γ isoforms of CaMKII serve as fundamental links between dishevelled and consecutive detrimental effects. Our findings reveal that the dishevelled-CaMKII-HDAC4-MEF2 axis holds a pivotal role in maladaptive cardiac remodeling and is a potential novel therapeutic target for the prevention of LV dysfunction. MethodsMaterials and Methods are available in the online-only Data Supplement . ResultsCaMKIIδ-Knockout, CaMKIIγ-Knockout, CaMKIIδγ-Knockout, and Dishevelled-1-Transgenic Mice Lacking CaMKII Are GeneratedWe previously reported that dishevelled-1-transgenic (DVL) mice exhibit a robust increase in both phosphorylated and total CaMKII levels, 10 which are known to play a key role in cardiac dysfunction. In the same study, we have also found that Dlv-1 knockdown prevents cardiomyocyte hypertrophy in response to β-adrenergic stimulation. Using...