Nuclear histone deacetylase 4 (HDAC4) represses MEF2-mediated transcription, implicated in the development of heart failure. CaMKII-dependent phosphorylation drives nucleus-to-cytoplasm HDAC4 shuttling, but protein kinase A (PKA) is also linked to HDAC4 translocation. However, the interplay of CaMKII and PKA in regulating adult cardiomyocyte HDAC4 translocation is unclear. Here we sought to determine the interplay of PKA- and CaMKII-dependent HDAC4 phosphorylation and translocation in adult mouse, rabbit and human ventricular myocytes. Confocal imaging and protein analyses revealed that inhibition of CaMKII—but not PKA, PKC or PKD—raised nucleo-to-cytoplasmic HDAC4 fluorescence ratio (F_Nuc/F_Cyto) by ~ 50%, indicating baseline CaMKII activity that limits HDAC4 nuclear localization. Further CaMKII activation (via increased extracellular [Ca²⁺], high pacing frequencies, angiotensin II or overexpression of CaM or CaMKIIδC) led to significant HDAC4 nuclear export. In contrast, PKA activation by isoproterenol or forskolin drove HDAC4 into the nucleus (raising F_Nuc/F_Cyto by > 60%). These PKA-mediated effects were abolished in cells pretreated with PKA inhibitors and in cells expressing mutant HDAC4 in S265/266A mutant. In physiological conditions where both kinases are active, PKA-dependent nuclear accumulation of HDAC4 was predominant in the very early response, while CaMKII-dependent HDAC4 export prevailed upon prolonged stimuli. This orchestrated co-regulation was shifted in failing cardiomyocytes, where CaMKII-dependent effects predominated over PKA-dependent response. Importantly, human cardiomyocytes showed similar CaMKII- and PKA-dependent HDAC4 shifts. Collectively, CaMKII limits nuclear localization of HDAC4, while PKA favors HDAC4 nuclear retention and S265/266 is essential for PKA-mediated regulation. These pathways thus compete in HDAC4 nuclear localization and transcriptional regulation in cardiac signaling.

核组蛋白脱乙酰酶 4 (HDAC4) 抑制 MEF2 介导的转录，这与心力衰竭的发展有关。CaMKII 依赖性磷酸化驱动细胞核到细胞质的 HDAC4 穿梭，但蛋白激酶 A (PKA) 也与 HDAC4 易位有关。然而，CaMKII 和 PKA 在调节成人心肌细胞 HDAC4 易位中的相互作用尚不清楚。在这里，我们试图确定 PKA 和 CaMKII 依赖性 HDAC4 磷酸化和易位在成年小鼠、兔和人心室肌细胞中的相互作用。共聚焦成像和蛋白质分析表明，抑制 CaMKII（而非 PKA、PKC 或 PKD）可提高核质 HDAC4 荧光比 (F Nuc _/ F _Cyto) 约 50%，表明限制 HDAC4 核定位的基线 CaMKII 活动。进一步激活 CaMKII（通过增加细胞外 [Ca ²⁺ ]、高起搏频率、血管紧张素 II 或 CaM 或 CaMKIIδC 的过度表达）导致显着的 HDAC4 核输出。相比之下，异丙肾上腺素或毛喉素的 PKA 激活将 HDAC4 驱动到细胞核中（提高 F _Nuc /F _Cyto> 60%)。这些 PKA 介导的作用在用 PKA 抑制剂预处理的细胞和在 S265/266A 突变体中表达突变体 HDAC4 的细胞中被消除。在两种激酶都活跃的生理条件下，依赖于 PKA 的 HDAC4 核积累在极早期反应中占主导地位，而依赖于 CaMKII 的 HDAC4 输出在长时间的刺激下占主导地位。这种精心策划的协同调节在衰竭的心肌细胞中发生了变化，其中 CaMKII 依赖性效应优于 PKA 依赖性反应。重要的是，人类心肌细胞表现出类似的 CaMKII 和 PKA 依赖性 HDAC4 转变。总的来说，CaMKII 限制了 HDAC4 的核定位，而 PKA 有利于 HDAC4 核保留，而 S265/266 对于 PKA 介导的调节至关重要。