Regulation of Liver CPT-I during Diabetic Ketosis

糖尿病酮症期间肝脏 CPT-I 的调节

• 批准号: 7093174
• 负责人: Charles Leslie Hoppel
• 金额: $ 27.16万
• 依托单位: CASE WESTERN RESERVE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-07-11 至 2009-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7093174
• 关键词: carnitine palmitoyltransferase 1; chemical kinetics; diabetic acidosis; electrospray ionization mass spectrometry; enzyme activity; enzyme induction /repression; enzyme mechanism; fatty acid metabolism; high performance liquid chromatography; hormone regulation /control mechanism; immunoprecipitation; laboratory rabbit; laboratory rat; liver metabolism; malonyl coA; mitochondria; multiple sclerosis; phosphoprotein phosphatase; phosphorylation; posttranslational modifications; protein kinase; protein sequence

DESCRIPTION (provided by applicant): The liver plays a central role in physiological and pathological conditions by switching from a carbohydrate to fatty acid-based metabolism. Carnitine palmitoyltransferase-l (CPT-I) is the key regulated step in the hormone-induced changes in mitochondrial fatty acid oxidation mediated via the cAMP signaling system. Malonyl-CoA inhibits CPT-I activity and represents the control point for fatty acid oxidation. The mechanism for the dramatically decreased malonyl-CoA sensitivity of CPT-I in fasting and diabetes has not been uncovered. We have shown 1) regulation of CPT-I involves the covalent modification of the CPT-I protein by phosphorylation and dephosphorylation, 2) 50 percent of mitochondrial CPT-I localizes with contact sites, 3) the localization of CPT-I in contact sites is enhanced in diabetic ketoacidosis, 4) inhibition kinetics of CPT-I in liver mitochondrial contact sites from diabetic ketoacidotic rats differs markedly from insulin-treated diabetic rats. Our hypothesis is that in the hormonal milieu resulting in the activation of hepatic protein kinases, CPT-I is phosphorylated leading to resistance to malonyl-CoA inhibition; thus more malonyl-CoA is required to effect the same degree of inhibition, but without a change in the velocity of CPT-I. We hypothesize that contact sites serve as docking domains for protein kinases and protein phosphatases involved in CPT-I regulation. The phosphorylation / dephosphorylation-based regulation of CPT-I occurs in contact sites where the phosphorylated CPT-I predominantly exists. Aim 1 is to determine the amino acid sequence of the phosphorylated peptide following digestion of the immunoprecipitated CPT-I. Aim 2 is to identify the kinase(s) for phosphorylation and the phosphatase(s) for dephosphorylation of CPT-I. The studies will address the functional consequences of CPT-I phosphorylation in isolated hepatocytes. Aim 3 will examine the relationship between CPT-I kinetics and phosphorylation in liver of diabetic ketoacidotic rats. Aim 4 approaches whether contact sites provide docking domains for kinase(s) and phosphatase(s), as well as, for liver isoform of CPT-I. In Aim 5 malonyl-CoA content of the liver will be determined under the various metabolic states. The proposed studies will establish at the molecular and biochemical level the phosphorylation cycle of CPT-I and how it relates to the kinetics of CPT-I in liver.

描述（由申请人提供）：肝脏通过从碳水化合物代谢转变为基于脂肪酸的代谢，在生理和病理条件下发挥核心作用。肉碱棕榈酰转移酶-1 (CPT-I) 是通过 cAMP 信号系统介导的激素诱导的线粒体脂肪酸氧化变化的关键调节步骤。丙二酰辅酶A 抑制CPT-I 活性并代表脂肪酸氧化的控制点。 CPT-I 在禁食和糖尿病中显着降低丙二酰辅酶 A 敏感性的机制尚未被发现。我们已经证明 1) CPT-I 的调节涉及通过磷酸化和去磷酸化对 CPT-I 蛋白进行共价修饰，2) 50% 的线粒体 CPT-I 定位于接触位点，3) CPT-I 定位于接触位点在糖尿病酮症酸中毒中增强，4)糖尿病酮症酸中毒大鼠肝线粒体接触位点中CPT-I的抑制动力学与胰岛素治疗的糖尿病大鼠显着不同。我们的假设是，在导致肝蛋白激酶激活的激素环境中，CPT-I 被磷酸化，从而导致对丙二酰辅酶 A 抑制的抵抗；因此需要更多的丙二酰辅酶A来实现相同程度的抑制，但不改变CPT-I的速度。我们假设接触位点充当参与 CPT-I 调节的蛋白激酶和蛋白磷酸酶的对接域。 CPT-I 基于磷酸化/去磷酸化的调节发生在主要存在磷酸化 CPT-I 的接触位点。目标 1 是确定免疫沉淀的 CPT-I 消化后磷酸化肽的氨基酸序列。目标 2 是鉴定用于 CPT-I 磷酸化的激酶和用于去磷酸化的磷酸酶。这些研究将解决离体肝细胞中 CPT-I 磷酸化的功能后果。目标 3 将检查 CPT-I 动力学与糖尿病酮症酸中毒大鼠肝脏磷酸化之间的关系。目标 4 探讨接触位点是否为激酶和磷酸酶以及 CPT-I 的肝亚型提供对接结构域。在Aim 5中，将在各种代谢状态下测定肝脏的丙二酰辅酶A含量。拟议的研究将在分子和生化水平上确定 CPT-I 的磷酸化循环及其与肝脏中 CPT-I 动力学的关系。