Kim Hyunbae, Mendez Roberto, Chen Xuequn, Fang Deyu, Zhang Kezhong
Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, Michigan, USA.
Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan, USA.
Mol Cell Biol. 2015 Dec;35(24):4121-34. doi: 10.1128/MCB.00665-15. Epub 2015 Oct 5.
Cyclic AMP-responsive element-binding protein 3-like 3, hepatocyte specific (CREBH), is a hepatic transcription factor that functions as a key regulator of energy homeostasis. Here, we defined a regulatory CREBH posttranslational modification process, namely, lysine-specific acetylation, and its functional involvement in fasting-induced hepatic lipid metabolism. Fasting induces CREBH acetylation in mouse livers in a time-dependent manner, and this event is critical for CREBH transcriptional activity in regulating hepatic lipid homeostasis. The histone acetyltransferase PCAF-mediated acetylation and the deacetylase sirtuin-1-mediated deacetylation coexist to maintain CREBH acetylation states under fasting conditions. Site-directed mutagenesis and functional analyses revealed that the lysine (K) residue at position 294 (K294) within the bZIP domain of the CREBH protein is the site where fasting-induced acetylation/deacetylation occurs. Introduction of the acetylation-deficient (K294R) or acetylation-mimicking (K294Q) mutation inhibited or enhanced CREBH transcriptional activity, respectively. Importantly, CREBH acetylation at lysine 294 was required for the interaction and synergy between CREBH and peroxisome proliferator-activated receptor α (PPARα) in activating their target genes upon fasting or glucagon stimulation. Introduction of the CREBH lysine 294 mutation in the liver leads to hepatic steatosis and hyperlipidemia in animals under prolonged fasting. In summary, our study reveals a molecular mechanism by which fasting or glucagon stimulation modulates lipid homeostasis through acetylation of CREBH.
环磷酸腺苷反应元件结合蛋白3样3，肝细胞特异性（CREBH），是一种肝脏转录因子，作为能量稳态的关键调节因子发挥作用。在此，我们定义了一种CREBH的翻译后修饰调控过程，即赖氨酸特异性乙酰化，及其在禁食诱导的肝脏脂质代谢中的功能参与。禁食以时间依赖性方式诱导小鼠肝脏中CREBH的乙酰化，这一事件对于CREBH在调节肝脏脂质稳态中的转录活性至关重要。组蛋白乙酰转移酶PCAF介导的乙酰化和去乙酰化酶沉默调节蛋白1介导的去乙酰化共存，以在禁食条件下维持CREBH的乙酰化状态。定点诱变和功能分析表明，CREBH蛋白bZIP结构域中第294位的赖氨酸（K）残基（K294）是禁食诱导的乙酰化/去乙酰化发生的位点。引入乙酰化缺陷型（K294R）或乙酰化模拟型（K294Q）突变分别抑制或增强了CREBH的转录活性。重要的是，在禁食或胰高血糖素刺激下激活其靶基因时，CREBH赖氨酸294位的乙酰化是CREBH与过氧化物酶体增殖物激活受体α（PPARα）之间相互作用和协同作用所必需的。在肝脏中引入CREBH赖氨酸294突变会导致长期禁食的动物出现肝脂肪变性和高脂血症。总之，我们的研究揭示了一种分子机制，通过该机制禁食或胰高血糖素刺激通过CREBH的乙酰化调节脂质稳态。
