Regulation of ABCA1 functions by JAK2/STAT3 pathway

描述（由申请方提供）：动脉壁巨噬细胞中的胆固醇蓄积和动脉壁炎症均有助于心血管疾病（CVD）的发生。ATP结合盒转运蛋白A1（ABCA 1）是一种细胞膜蛋白，对HDL合成和逆转胆固醇转运至关重要，似乎通过几种机制保护免受CVD，包括从动脉壁细胞中清除胆固醇和抑制炎症。我们已经表明，Janus激酶2（JAK 2）激活调节ABCA 1介导的胆固醇和磷脂流出的影响相互作用的apoA 1或apoA-I模拟肽与ABCA 1。然而，JAK 2激活调节ABCA 1与apoA-I结合的机制尚不清楚。此外，我们还发现apoA-I或apoA-I模拟肽与ABCA 1的相互作用激活了STAT 3通路。而JAK 2的激活是必需的脂质清除和ABCA 1的最佳apoA-I结合活性，STAT 3的激活不参与脂质转运。已经显示巨噬细胞中STAT 3的组成性激活抑制炎性细胞因子的产生，这意味着激活巨噬细胞中STAT 3的因子具有抗炎作用。事实上，我们发现用apoA-I或其模拟肽预处理表达ABCA 1的J774巨噬细胞激活STAT 3并显著减少随后的LPS或脂质A刺激的细胞因子产生。我们假设，除了其胆固醇输出活性（其可能具有抗炎作用）之外，ABCA 1还通过独立于其脂质输出活性的STAT 3途径的激活而作为抗炎信号传导受体发挥作用。该项目将 回答几个关键问题：1. JAK 2的激活将如何影响apoA-I或其模拟肽与ABCA 1的相互作用，从而调节ABCA 1介导的胆固醇流出？第二章：没有胆固醇流出的STAT 3激活是否足以介导ABCA 1与apoA-I或apoA-I模拟肽相互作用的抗炎作用？第三章：在激活ABCA 1/JAK 2/STAT 3通路中具有更大和更特异活性的apoA-I模拟肽在介导ABCA 1的胆固醇流出和抗炎作用方面是否具有上级优势？这些问题的解决将大大提高我们对ABCA 1介导的胆固醇流出的认识，并可能为开发针对ABCA 1通路的治疗CVD的治疗剂提供新的机会

DESCRIPTION (provided by applicant): Cholesterol accumulation in arterial wall macrophages and inflammation of artery wall both contribute to the development of cardiovascular disease (CVD). ATP-binding cassette transporter A1 (ABCA1), a cell membrane protein that is essential for HDL synthesis and reversal cholesterol transport, appears to protect against CVD by several mechanisms that include removal of cholesterol from arterial wall cells and suppression of inflammation. We have shown that Janus kinase 2 (JAK2) activation regulates ABCA1- mediated cholesterol and phospholipids efflux by affecting the interaction of apoA1 or apoA-I mimetic peptides with ABCA1. However the mechanisms by which JAK2 activation regulates ABCA1 binding to apoA-I is unknown. Moreover, we also found that the interaction of apoA-I or apolipoprotein-mimetic peptides with ABCA1 activates STAT3 pathway. Whereas JAK2 activation is required for the lipid-removal and optimum apoA-I binding activity of ABCA1, STAT3 activation is not involved in lipid transport. It has been shown that constitutive activation of STAT3 in macrophages suppresses production of inflammatory cytokines, implying that factors that activate STAT3 in macrophages have an anti-inflammatory effect. Indeed, we found that pre- treating ABCA1-expressing J774 macrophages with apoA-I or its mimetic peptides activate STAT3 and markedly reduce subsequent LPS or lipid A-stimulated cytokine production. We hypothesize that, in addition to its cholesterol export activity, which may have anti-inflammatory effects, ABCA1 also functions as an anti- inflammatory signaling receptor through the activation of STAT3 pathway independent of its lipid export activity. This project will answer several key questions: 1. How will JAK2 activation affect apoA-I or its mimetic peptides interaction with ABCA1, therefore to regulate ABCA1-mediated cholesterol efflux? 2: Is STAT3 activation without cholesterol efflux sufficient to mediate the anti-inflammatory effect of the interaction of ABCA1 with apoA-I or apoA-I mimetic peptides? 3: Will apoA-I mimetic peptides that have greater and more specific activity in activating the ABCA1/JAK2/STAT3 pathways are superior at mediating the cholesterol efflux and anti-inflammatory effects of ABCA1? Address those questions would significantly advance our knowledge on ABCA1-mediated cholesterol efflux and could open new opportunities in the development of therapeutic agents that target ABCA1 pathways for treating CVD