Mechanisms of p42/44MAPK-induced LDL receptor expression

p42/44MAPK诱导LDL受体表达的机制

• 批准号: 6656862
• 负责人: KAMAL D MEHTA
• 金额: $ 25.81万
• 依托单位: OHIO STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-08-01 至 2005-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6656862
• 关键词: DNA footprinting; acetylation; biological signal transduction; cAMP response element binding protein; cell line; chromatin; disease /disorder model; genetic promoter element; genetic regulation; hepatocyte growth factor; hypercholesterolemia; immunoprecipitation; interleukin 1; intermolecular interaction; laboratory rat; lipopolysaccharides; low density lipoprotein; low density lipoprotein receptor; mitogen activated protein kinase; molecular site; nucleic acid structure; phosphorylation; protein structure function; receptor expression; site directed mutagenesis; western blottings

Of all known risk factors promoting coronary artery disease, a high serum low density lipoprotein (LDL) level is the most important. The regulation of hepatic LDL receptor expression is a potential mechanism by which dietary and humoral factors alter plasma LDL levels, and upregulation of LDL receptor expression is the basis for current treatment of hypercholesterolemia. The negative regulation of LDL receptor transcription by sterols has been extensively delineated; however, the molecular mechanisms of induction and the signaling cascades controlling activity of critical nuclear factor(s) are not known. Recently, we provided the first evidence that specific activation of the p42/44mitogen-activated protein kinase (MAPK) is not only required but is sufficient to fully induce LDL receptor expression. Our recent observations supporting the requirement of CREB-binding protein (CBP) in p42/44MAPK-induced LDL receptor transcription are the basis of Specific Aim 1, and the studies proposed will link CBP acetyltransferase activity with modification of sterol responsive element binding proteins (SREBPs) and/or chromatin remodeling in the promoter region. Effects of CBP-SREBP protein-protein interactions on transactivation and on chromatin structures during the induction process will be examined by using a p42/44MAPK-responsive mammalian two-hybrid system and in vivo footprinting techniques. The Specific Aim 2 will study interleukin-1beta- and hepatocyte growth factor-induced LDL receptor expression to examine how p42/44MAPK participates during induction by sterol-sensitive and sterol-independent mechanisms. The Specific Aim 3 will establish a negative relationship between stress-activated p38MAPK alpha- isoform and LDL receptor expression and then examine the role of p38MAPK activation in stress-induced hypercholesterolemia through suppression of LDL receptor expression. This aim is based on our observation that specific inhibition of p38MAPK alpha-isoform induces LDL receptor expression via suppression of p42/44MAPK. Finally, in light of the crucial roles of MAPKs in hepatic cells, the Specific Aim 4 will examine the roles of p42/44MAPK and p38MAPK cascades in regulating expression of LDL and scavenger receptors that are a critical determinant of lipid accumulation in the macrophages and their conversion to foam cells. Defining the molecular mechanisms and the signaling pathways regulating the induction process will help in understanding the pathologic states under which the receptor pathways are perturbed, resulting in hypercholesterolemia. This knowledge could be exploited to develop improved hypercholesterolemia therapies and to reduce foam cell formation.

在促进冠状动脉疾病的所有已知危险因素中，高血清低密度脂蛋白（LDL）水平是最重要的。 肝LDL受体表达的调节是一种潜在的机制，饮食和体液因子改变了血浆LDL水平，而LDL受体表达的上调是当前治疗高胆固醇血症的基础。 固醇对LDL受体转录的负调控已被广泛描述。然而，尚不清楚诱导和控制关键核因子活性的信号传导级联反应的分子机制。 最近，我们提供了第一个证据，表明p42/44的特异性激活不仅需要p42/44的蛋白质激酶（MAPK），而且足以完全诱导LDL受体表达。 我们最近支持p42/44MAPK诱导的LDL受体转录中CREB结合蛋白（CBP）的需求的观察结果是特定目标1的基础，并且提出的研究将将CBP乙酰基转移酶活性与固醇反应元件结合蛋白（SREBPS）（SREBPS）和/或或牛皮化剂的启动蛋白的改进联系起来。 CBP-SREBP蛋白 - 蛋白质相互作用对诱导过程中反式激活和染色质结构的影响将通过使用P42/44MAPK反应性哺乳动物两杂化系统和体内足迹技术来检查。具体目标2将研究白介素1Beta-和肝细胞生长因子诱导的LDL受体表达，以检查P42/44MAPK在诱导过程中如何通过固醇敏感和固醇独立的机制参与。 具体的目标3将在应力激活的p38mapkα-同工型和LDL受体表达之间建立负相关关系，然后检查p38MAPK激活在压力诱导的高胆固醇血症中通过抑制LDL受体表达的作用。 这个目的是基于我们观察到的，即对p38mapkα-同工型的特异性抑制通过抑制p42/44mapk诱导LDL受体表达。最后，鉴于MAPK在肝细胞中的关键作用，具体的目标4将检查p42/44mapk和p38mapk级联对于调节LDL和清除剂受体的表达的作用，这些作用是脂质噬细胞中脂质积累的关键决定性的决定性决定性的，及其对巨噬细胞中的脂肪及其对泡沫细胞的转化。 定义调节诱导过程的分子机制和信号通路将有助于理解受体途径受到干扰的病理状态，从而导致高胆固醇血症。 可以利用这些知识来发展改善的高胆固醇血症疗法并减少泡沫细胞的形成。