Zhang Haining, Shao Zongjun, Alibin Caroline P, Acosta Crystal, Anderson Hope D
From the Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface General Hospital Research Centre, Winnipeg, Manitoba, Canada.
From the Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface General Hospital Research Centre, Winnipeg, Manitoba, Canada; Department of Pharmacology & Therapeutics, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada.
PLoS One. 2014 Dec 16;9(12):e115258. doi: 10.1371/journal.pone.0115258. eCollection 2014.
Ligand activation of peroxisome proliferator-activated receptors (PPARs) prevents cardiac myocyte hypertrophy, and we previously reported that diacylglycerol kinase zeta (DGKζ) is critically involved. DGKζ is an intracellular lipid kinase that catalyzes phosphorylation of diacylglycerol; by attenuating DAG signaling, DGKζ suppresses protein kinase C (PKC) and G-protein signaling. Here, we investigated how PPAR-DGKζ signaling blocks activation of the hypertrophic gene program. We focused on export of histone deacetylase 5 (HDAC5) from the nucleus, a key event during hypertrophy, since crosstalk occurs between PPARs and other members of the HDAC family. Using cardiac myocytes isolated from Sprague-Dawley rats, we determined that liganded PPARs disrupt endothelin-1 (ET1)-induced nuclear export of HDAC5 in a manner that is dependent on DGKζ. When DGKζ-mediated PKC inhibition was circumvented using a constitutively-active PKCε mutant, PPARs failed to block ET1-induced nuclear retention of HDAC5. Liganded PPARs also prevented (i) activation of protein kinase D (the downstream effector of PKC), (ii) HDAC5 phosphorylation at 14-3-3 protein chaperone binding sites (serines 259 and 498), and (iii) physical interaction between HDAC5 and 14-3-3, all of which are consistent with blockade of nucleo-cytoplasmic shuttling of HDAC5. Finally, the ability of PPARs to prevent neutralization of HDAC5 activity was associated with transcriptional repression of hypertrophic genes. This occurred by first, reduced MEF2 transcriptional activity and second, augmented deacetylation of histone H3 associated with hypertrophic genes expressing brain natriuretic peptide, β-myosin heavy chain, skeletal muscle α-actin, and cardiac muscle α-actin. Our findings identify spatial regulation of HDAC5 as a target for liganded PPARs, and to our knowledge, are the first to describe a mechanistic role for nuclear DGKζ in cardiac myocytes. In conclusion, these results implicate modulation of HDAC5 as a mechanism by which liganded PPARs suppress the hypertrophic gene program.
过氧化物酶体增殖物激活受体（PPARs）的配体激活可预防心肌细胞肥大，我们之前报道二酰甘油激酶ζ（DGKζ）起着关键作用。DGKζ是一种细胞内脂质激酶，催化二酰甘油的磷酸化；通过减弱二酰基甘油（DAG）信号传导，DGKζ抑制蛋白激酶C（PKC）和G蛋白信号传导。在此，我们研究了PPAR - DGKζ信号传导如何阻断肥厚基因程序的激活。我们聚焦于组蛋白去乙酰化酶5（HDAC5）从细胞核输出这一肥大过程中的关键事件，因为PPARs与HDAC家族的其他成员之间存在相互作用。使用从Sprague - Dawley大鼠分离的心肌细胞，我们确定配体结合的PPARs以依赖于DGKζ的方式破坏内皮素 - 1（ET1）诱导的HDAC5核输出。当使用组成型激活的PKCε突变体规避DGKζ介导的PKC抑制时，PPARs无法阻断ET1诱导的HDAC5核滞留。配体结合的PPARs还可防止（i）蛋白激酶D（PKC的下游效应器）的激活，（ii）HDAC5在14 - 3 - 3蛋白伴侣结合位点（丝氨酸259和498）的磷酸化，以及（iii）HDAC5与14 - 3 - 3之间的物理相互作用，所有这些均与HDAC5的核质穿梭阻断一致。最后，PPARs防止HDAC5活性中和的能力与肥厚基因的转录抑制相关。这首先通过降低MEF2转录活性，其次通过增强与表达脑钠肽、β - 肌球蛋白重链、骨骼肌α - 肌动蛋白和心肌α - 肌动蛋白的肥厚基因相关的组蛋白H3去乙酰化而发生。我们的研究结果确定HDAC5的空间调节是配体结合的PPARs的作用靶点，据我们所知，这是首次描述核DGKζ在心肌细胞中的机制作用。总之，这些结果表明HDAC5的调节是配体结合的PPARs抑制肥厚基因程序的一种机制。
