Phospholipid metabolism and membrane function

磷脂代谢和膜功能

• 批准号: 8657370
• 负责人: GEORGE M. CARMAN
• 金额: $ 7.09万
• 依托单位: RUTGERS, THE STATE UNIV OF N.J.
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-04 至 2014-09-03
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8657370
• 关键词: 1,2-diacylglycerol; Biochemical; Biochemical Genetics; Cells; Cytidine Diphosphate Diglycerides; Defect; Diacylglycerol Kinase; Diglycerides; Endocytosis; Enzymatic Biochemistry; Enzymes; Equilibrium; Exhibits; Fatty Acids; Gene Expression; Genes; Grant; Growth; Human; Hydrolysis; Inflammation; Lecithin; Lipids; Lipodystrophy; Lipolysis; Mammals; Membrane; Metabolic Diseases; Metabolism; Mus; Mutation; Myoglobinuria; Nature; Nuclear; Obesity; Pathway interactions; Peripheral Nervous System Diseases; Phase; Phenotype; Phosphatidate Phosphatase; Phosphatidic Acid; Phosphatidylethanolamine; Phospholipid Metabolism; Phospholipids; Protein Dephosphorylation; Protein Isoforms; Reaction; Regulation; Role; Saccharomyces cerevisiae; Signaling Molecule; Transcriptional Regulation; Triglycerides; Yeasts; gene synthesis; lipid metabolism; lipine; membrane synthesis; mutant; novel; overexpression; trafficking

Phosphatidic acid phosphatase (PAP) catalyzes the dephosphorylation of phosphatidic acid (PA) to yield diacylglycerol (DAG) and Pi. The DAG generated in the reaction is used for the synthesis of triacylglycerol (TAG), and for the synthesis of phosphatidylethanolamine and phosphatidylcholine via the Kennedy pathway. By the nature of its reaction, PAP also controls the cellular content of PA, which is the precursor of phospholipids synthesized via the CDP-DAG pathway. PA is also a signaling molecule that triggers phospholipid synthesis gene expression, membrane expansion, vesicular trafficking, secretion, and endocytosis. Biochemical and genetic studies to establish the roles of PAP in lipid metabolism became possible by our discoveries of the PAP-encoding genes from the yeast Saccharomyces cerevisiae (e.g., PAH1) and mammals (e.g., LPIN1). The importance PAP in lipid metabolism is exemplified by its mutant phenotypes. In yeast, pah1 mutants exhibit defects in the transcriptional regulation of phospholipid synthesis genes, the anomalous expansion of the nuclear/ER membrane, and a 90 % reduction in TAG content in stationary phase cells. Studies with mice and humans have shown that genetic defects in lipin 1 and lipin 2 are manifested in several metabolic diseases that include lipodystrophy, obesity, peripheral neuropathy, myoglobinuria, and inflammation. In the next grant period, we will focus on the regulated expression of the yeast PAH1-encoded PAP enzyme during growth and its role in lipid metabolism (specific aim 1). In addition, we will expand our studies on PAP to include the enzymology and biochemical regulation of the human LPIN1-, LPIN2-, and LPIN3-encoded PAP isoforms (specific aim 2). We also discovered a novel CTP-dependent DGK1-encoded DAG kinase in yeast that counterbalanced the activity of PAP to control the cellular contents of PA and DAG. The dgk1 mutation suppresses phenotypes caused by the pah1 mutation, whereas the overexpression of DAG kinase blunts phenotypes caused by the overexpression of PAP. In yeast, TAG hydrolysis (e.g., lipolysis) to DAG and fatty acids is a prerequisite for membrane phospholipid synthesis and resumption of growth from the stationary phase. We will examine the role and regulation of the DGK1-encoded DAG kinase enzyme in this metabolism (specific aim 3).

磷脂酸性磷酸酶(PAP)催化磷脂酸(PA)去磷酸化生成二酰甘油(DAG)和PI。反应中产生的DAG用于合成三酰甘油(TAG)，并通过肯尼迪途径合成磷脂酰乙醇胺和磷脂酰胆碱。根据其反应的性质，PAP还控制PA的细胞含量，PA是通过CDP-DAG途径合成磷脂的前体。PA也是一个信号分子，触发磷脂合成基因表达、膜扩张、囊泡运输、分泌和内吞作用。我们在酿酒酵母(如PAH1)和哺乳动物(如LPIN1)中发现了编码PAP的基因，从而有可能进行生化和遗传学研究，以确定PAP在脂质代谢中的作用。PAP在脂类代谢中的重要性从其突变表型中可见一斑。在酵母中，pah1突变体表现出磷脂合成基因转录调控的缺陷，核/ER膜的异常扩张，以及稳定期细胞中Tag含量的90%下降。对小鼠和人类的研究表明，脂类1和脂类2的遗传缺陷表现在几种代谢性疾病中，包括脂肪营养不良、肥胖、周围神经病变、肌红蛋白尿和炎症。在下一个资助期间，我们将重点研究酵母PAH1编码的PAP酶在生长过程中的调控表达及其在脂肪代谢中的作用(特定目标1)。此外，我们将扩大我们对PAP的研究，包括人类LPIN1-、LPIN2-和LPIN3编码的PAP亚型的酶学和生化调节(特定目标2)。我们还在酵母中发现了一种新的依赖CTP的DGK1编码的DAG激酶，它平衡了PAP的活性，控制了PA和DAG的细胞含量。Dgk1突变抑制由pah1突变引起的表型，而DAG激酶的过表达使PAP过表达引起的表型钝化。在酵母中，TAG水解(例如脂解)为DAG和脂肪酸是膜磷脂合成和从固定相恢复生长的先决条件。我们将研究DGK1编码的DAG激酶在这种代谢中的作用和调节(特定目标3)。