Bond Simon T, Howlett Kirsten F, Kowalski Greg M, Mason Shaun, Connor Timothy, Cooper Adrian, Streltsov Victor, Bruce Clinton R, Walder Ken R, McGee Sean L
Metabolic Research Unit, School of Medicine, Deakin University, Geelong, Victoria, Australia.
Centre for Molecular and Medical Research, Deakin University, Geelong, Victoria, Australia.
FASEB J. 2017 Jun;31(6):2592-2602. doi: 10.1096/fj.201601215R. Epub 2017 Mar 3.
Reciprocal regulation of hepatic glycolysis and gluconeogenesis contributes to systemic metabolic homeostasis. Recent evidence from lower order organisms has found that reversible post-translational modification of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), particularly acetylation, contributes to the reciprocal regulation of glycolysis/gluconeogenesis. However, whether this occurs in mammalian hepatocytes or is unknown. Several proteomics studies have identified 4 lysine residues in critical regions of mammalian GAPDH that are altered by multiple post-translational modifications. In FAO hepatoma cells, mutation of all 4 lysine residues (4K-R GAPDH) to mimic their unmodified state reduced GAPDH glycolytic activity and glycolytic flux and increased gluconeogenic GAPDH activity and glucose production. Hepatic expression of 4K-R GAPDH in mice increased GAPDH gluconeogenic activity and the contribution of gluconeogenesis to endogenous glucose production in the unfed state. Consistent with the increased reliance on the energy-consuming gluconeogenic pathway, plasma free fatty acids and ketones were elevated in mice expressing 4K-R GAPDH, suggesting enhanced lipolysis and hepatic fatty acid oxidation. In normal mice, food withholding and refeeding, as well as hormonal regulators of reciprocal glycolysis/gluconeogenesis, such as insulin, glucagon, and norepinephrine, had no effect on global GAPDH acetylation. However, GAPDH acetylation was reduced in obese and type 2 diabetic mice. These findings show that post-translational modification of GAPDH lysine residues regulates hepatic and systemic metabolism, revealing an unappreciated role for hepatic GAPDH in substrate selection and utilization.-Bond, S. T., Howlett, K. F., Kowalski, G. M., Mason, S., Connor, T., Cooper, A., Streltsov, V., Bruce, C. R., Walder, K. R., McGee, S. L. Lysine post-translational modification of glyceraldehyde-3-phosphate dehydrogenase regulates hepatic and systemic metabolism.
肝脏糖酵解与糖异生的相互调节有助于维持全身代谢稳态。来自低等生物的最新证据表明，甘油醛-3-磷酸脱氢酶（GAPDH）的可逆翻译后修饰，尤其是乙酰化，参与了糖酵解/糖异生的相互调节。然而，这在哺乳动物肝细胞中是否发生尚不清楚。多项蛋白质组学研究已确定哺乳动物GAPDH关键区域的4个赖氨酸残基会受到多种翻译后修饰的影响。在脂肪酸氧化（FAO）肝癌细胞中，将所有4个赖氨酸残基（4K-R GAPDH）突变为模拟其未修饰状态，会降低GAPDH的糖酵解活性和糖酵解通量，并增加糖异生的GAPDH活性和葡萄糖生成。小鼠肝脏中4K-R GAPDH的表达增加了GAPDH的糖异生活性以及空腹状态下糖异生对内源性葡萄糖生成的贡献。与对耗能的糖异生途径的依赖性增加一致，表达4K-R GAPDH的小鼠血浆游离脂肪酸和酮水平升高，表明脂肪分解和肝脏脂肪酸氧化增强。在正常小鼠中，禁食和再喂食以及糖酵解/糖异生相互调节的激素调节剂，如胰岛素、胰高血糖素和去甲肾上腺素，对整体GAPDH乙酰化没有影响。然而，肥胖和2型糖尿病小鼠的GAPDH乙酰化水平降低。这些发现表明，GAPDH赖氨酸残基的翻译后修饰调节肝脏和全身代谢，揭示了肝脏GAPDH在底物选择和利用中未被认识的作用。-邦德，S.T.，豪利特，K.F.，科瓦尔斯基，G.M.，梅森，S.，康纳，T.，库珀，A.，斯特列尔佐夫，V.，布鲁斯，C.R.，瓦尔德，K.R.，麦吉，S.L.甘油醛-3-磷酸脱氢酶的赖氨酸翻译后修饰调节肝脏和全身代谢。
