Role of PKCbeta in Diet-induced Hypercholesterolemia

PKCbeta 在饮食引起的高胆固醇血症中的作用

• 批准号: 6857486
• 负责人: KAMAL D MEHTA
• 金额: $ 32.4万
• 依托单位: OHIO STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-12-06 至 2008-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6857486
• 关键词: RNase protection assay; atherosclerosis; cholesterol; dietary lipid; disease /disorder prevention /control; enhancer binding protein; gene environment interaction; genetic regulation; genetically modified animals; homeostasis; hypercholesterolemia; isozymes; laboratory mouse; low density lipoprotein; low density lipoprotein receptor; microarray technology; mitogen activated protein kinase; northern blottings; nutrition related tag; pathogenic diet; polymerase chain reaction; protein binding; protein kinase C; steroid metabolism

DESCRIPTION (provided by applicant): Coronary artery disease (CAD) remains the leading cause of death and disability in our society. Of all known risk factors promoting CAD, a high serum level of low-density lipoprotein (LDL)-cholesterol is one of the most important risk factors. The plasma level of this lipoprotein is strongly influenced by genetic factors and the amount of dietary fat and cholesterol; dietary modification remains the cornerstone of CAD prevention. Our knowledge of the regulatory mechanism(s) controlling cholesterol homeostasis in response to dietary cholesterol is limited, as is the role of signaling pathways initiated by alterations in cholesterol levels. Also, the interrelationships between these signaling pathways and sterol response element-binding proteins (SREBPs), as well as the mechanism linking SREBP processing and cholesterol levels are not clear. The emerging picture from our work is that regulation of hepatic LDL receptors, crucial for cholesterol homeostasis, results from the activity of a few interlinked regulatory signaling pathways. We have previously shown, for the first-time, involvement of specific isoforms of protein kinase C (PKC) in the regulation of LDL receptor expression in cultured hepatic cells, possibly through direct modulation of activity by cholesterol. Based on our recent results, we propose a central role for B-isoform of PKC (PKCb) in regulating cholesterol homeostasis via modulating expression of selected genes crucial for this process. In Specific Aim 1, the role of PKCb in cholesterol homeostasis will be established by evaluating the effect of knockout of this ldnase on overall cholesterol homeostasis. Initial studies with PKC(-deficient mice strongly support a central role of this kinase in controlling the responsiveness of plasma cholesterol to the changes in the dietary cholesterol content. Cholesterol metabolism will be compared in detail between normal and PKCb mutants fed special diets. The Specific Aim 2 will compare expression of the hepatic genes critical for cholesterol homeostasis in the above animals. In Specific Aim 3, mechanisms by which PKCb affects SREBP-2 expression and its proteolytic processing, possibly by regulating INSIG- 1 phosphorylation will be examined. Finally, the nature of the isoform-specific interaction between cholesterol and PKCb will be examined in the Specific Aim 4. The photoactive cholesterol probe will be used to define at the molecular level structure(s) and amino acids that produce isoform-specific binding of PKCb to cholesterol. The proposed studies will not only establish the role of PKCb in diet-induced hypercholesterolemia, but will also identify genes regulated by this kinase, to correlate regulatory mechanisms to animal physiology. They will also help understand the complex interactions between environment and genetics leading to atherosclerosis. Accomplishment of the above aims will unravel a central signaling component that may act as a sensor to respond to dietary cholesterol; modulation of its activity may be the preferable mode for the treatment of lipid disorders in the 21st century.

描述（由申请人提供）：冠状动脉疾病（CAD）仍然是我们社会死亡和残疾的主要原因。在所有已知的导致 CAD 的危险因素中，高血清低密度脂蛋白 (LDL) 胆固醇水平是最重要的危险因素之一。这种脂蛋白的血浆水平受到遗传因素以及膳食脂肪和胆固醇含量的强烈影响；饮食调整仍然是预防 CAD 的基石。我们对控制胆固醇稳态以响应膳食胆固醇的调节机制的了解是有限的，由胆固醇水平改变引发的信号通路的作用也是有限的。此外，这些信号通路与甾醇反应元件结合蛋白 (SREBP) 之间的相互关系，以及 SREBP 加工和胆固醇水平之间的联系机制尚不清楚。我们的工作得出的结论是，对胆固醇稳态至关重要的肝脏 LDL 受体的调节是由一些相互关联的调节信号通路的活动引起的。我们之前首次表明，蛋白激酶 C (PKC) 的特定异构体可能通过胆固醇直接调节活性来参与调节培养肝细胞中的 LDL 受体表达。根据我们最近的结果，我们提出 PKC B 亚型 (PKCb) 通过调节对该过程至关重要的选定基因的表达，在调节胆固醇稳态中发挥核心作用。在具体目标 1 中，将通过评估 PKCb 基因敲除对总体胆固醇稳态的影响来确定 PKCb 在胆固醇稳态中的作用。对 PKC(-缺陷小鼠) 的初步研究强烈支持该激酶在控制血浆胆固醇对饮食胆固醇含量变化的反应中发挥核心作用。将详细比较正常和 PKCb 突变体喂养特殊饮食的胆固醇代谢。具体目标 2 将比较上述动物中对胆固醇稳态至关重要的肝脏基因的表达。在具体目标 3 中，机制 将检查PKCb可能通过调节INSIG-1磷酸化影响SREBP-2表达及其蛋白水解加工。最后，胆固醇和 PKCb 之间异构体特异性相互作用的性质将在具体目标 4 中进行检查。光活性胆固醇探针将用于在分子水平上定义产生异构体特异性结合的结构和氨基酸。 PKCb 与胆固醇的关系。拟议的研究不仅将确定 PKCb 在饮食引起的高胆固醇血症中的作用，还将鉴定受该激酶调节的基因，从而将调节机制与动物生理学联系起来。它们还将有助于了解导致动脉粥样硬化的环境和遗传之间复杂的相互作用。实现上述目标将揭示一个中央信号组件，它可以充当传感器来响应 膳食胆固醇；调节其活性可能是21世纪治疗脂质紊乱的优选模式。