Mechanism of atheroprotective function of Akt3 kinase

Akt3激酶的动脉粥样硬化保护功能机制

• 批准号: 9031810
• 负责人: EUGENE A PODREZ
• 金额: $ 39.63万
• 依托单位: CLEVELAND CLINIC LERNER COM-CWRU
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-03-09 至 2019-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9031810
• 关键词: AKT3 gene; Ablation; Apolipoprotein E; Apoptosis; Arteries; Atherosclerosis; Bone Marrow; Cardiovascular Diseases; Cardiovascular system; Cell physiology; Cells; Chimera organism; Cholesterol; Cholesterol Esters; Cholesterol Homeostasis; Coronary Arteriosclerosis; Disease; Esterification; Event; Family; Foam Cells; Genes; Genetic; Goals; Health; Human; Human Cell Line; In Vitro; Lipids; Lipoproteins; Mammals; Marrow; Molecular; Mus; Pathway interactions; Patients; Phenotype; Phospholipids; Phosphorylation; Phosphotransferases; Physiology; Pinocytosis; Protein Isoforms; Protein Kinase; Protein-Serine-Threonine Kinases; Proteins; Regulation; Role; Signal Pathway; Specificity; Sterol O-Acyltransferase; Testing; atherogenesis; atheroprotective; cell growth; glucose metabolism; in vivo; knock-down; lipid metabolism; macrophage; monocyte; mutant; novel; novel strategies; novel therapeutic intervention; prevent; sterol O-acyltransferase 1; uptake

 DESCRIPTION (provided by applicant): Serine/threonine kinases Akt (also known as PKB), are among the most important and versatile protein kinases at the core of human physiology and disease. Akt regulate numerous cellular processes, including cell growth, glucose and lipid metabolism, differentiation, proliferation, and apoptosis. Three highly homologous Akt isoforms, encoded by three separate genes, are expressed in mammals. Combined deletions of the three Akt isoforms in the mouse suggest compensatory and complementary roles of isoforms. However, the three isoforms also have distinct functions, even though the mechanisms of specificity are only starting to emerge. Studies of the role of Akt, and specifically of Akt isofors, in atherogenesis are very limited. It has been recently shown that genetic ablation of Akt1 promotes coronary atherosclerosis via the enhanced expression of proinflammatory genes in the artery wall in a macrophage independent manner. We have recently explored the role of Akt3 in atherosclerosis using mice with a genetic ablation of the Akt3 gene. Our studies have demonstrated a specific, macrophage dependent, atheroprotective role for Akt3 in hyperlipidemic ApoE-/- mice. In a step-by-step fashion, we tested various potential mechanisms and demonstrated that the absence of Akt3 transforms macrophage into cell which aggressively accumulates cholesterol esters via two mechanisms: increased lipoprotein uptake via pinocytosis, and parallel increased protein stability of cholesterol esterifying enzyme ACAT1 (also known as SOAT1). Multiple lines of evidence suggested that Akt3 suppresses atherosclerosis by restricting cholesteryl ester accumulation and foam cell formation in macrophages, an early and critical step in atherogenesis. The mechanism is Akt isoform specific, and our preliminary studies suggest that one mechanism for specificity is via differentia subcellular localization of Akt1 (a major isoform in macrophages) and Akt3 in macrophages. The long-term goal of this proposal is to investigate the molecular mechanism of Akt3 regulation of macrophage function. As a specific hypothesis, we propose that Akt3 specifically suppresses transformation of macrophage into lipid accumulating phenotype by inhibiting macrophage pinocytosis and by regulating a particular branch of cholesterol metabolism - cholesterol esterification via direct regulation of ACAT1 protein stability. We will investigate the role of AK3 in atherogenesis in vivo and in vitro with a particular focus on the molecular mechanisms of regulation of Akt3 activity, ACAT1 expression and pinocytosis.

 描述（由申请人提供）：丝氨酸/苏氨酸激酶 Akt（也称为 PKB）是人类生理学和疾病核心的最重要和最通用的蛋白激酶之一。 Akt 调节许多细胞过程，包括细胞生长、葡萄糖和脂质代谢、分化、增殖和凋亡。哺乳动物中表达由三个独立基因编码的三种高度同源的 Akt 亚型。小鼠中三种 Akt 同工型的联合缺失表明同工型的补偿和互补作用。然而，这三种亚型也具有不同的功能，尽管特异性机制才刚刚开始出现。关于 Akt，特别是 Akt 异构体在动脉粥样硬化形成中的作用的研究非常有限。最近的研究表明，Akt1 的基因消融通过以不依赖于巨噬细胞的方式增强动脉壁中促炎基因的表达来促进冠状动脉粥样硬化。我们最近使用 Akt3 基因基因消除的小鼠探索了 Akt3 在动脉粥样硬化中的作用。我们的研究证明 Akt3 在高脂血症 ApoE-/- 小鼠中具有特定的、巨噬细胞依赖性的动脉粥样硬化保护作用。我们逐步测试了各种潜在机制，并证明 Akt3 的缺失会将巨噬细胞转化为通过两种机制积极积累胆固醇酯的细胞：通过胞饮作用增加脂蛋白摄取，并平行增加胆固醇酯化酶 ACAT1（也称为 SOAT1）的蛋白质稳定性。多种证据表明，Akt3 通过限制巨噬细胞中胆固醇酯的积累和泡沫细胞的形成（动脉粥样硬化形成的早期且关键的步骤）来抑制动脉粥样硬化。该机制是 Akt 亚型特异性的，我们的初步研究表明，一种特异性机制是通过巨噬细胞中 Akt1（巨噬细胞中的主要亚型）和 Akt3 的差异亚细胞定位。该提案的长期目标是研究Akt3调节巨噬细胞功能的分子机制。作为一个具体的假设，我们提出 Akt3 通过抑制巨噬细胞胞饮作用并通过直接调节 ACAT1 蛋白稳定性来调节胆固醇代谢的特定分支 - 胆固醇酯化，从而特异性抑制巨噬细胞向脂质积累表型的转化。我们将研究 AK3 在体内和体外动脉粥样硬化形成中的作用，特别关注 Akt3 活性、ACAT1 表达和胞饮作用调节的分子机制。