Regulation of ABCA1 functions by JAK2/STAT3 pathway

描述(申请人提供)：动脉壁巨噬细胞中胆固醇积聚和动脉壁炎症均可导致心血管疾病(CVD)的发生。ATP结合盒转运体A1(ABCA1)是一种细胞膜蛋白，对于高密度脂蛋白的合成和胆固醇的逆转运输是必不可少的，它似乎通过几种机制来预防心血管疾病，包括从动脉壁细胞中清除胆固醇和抑制炎症。我们已经证明Janus kinase2(JAK2)的激活通过影响apoA1或apoA-I模拟肽与ABCA1的相互作用来调节ABCA1介导的胆固醇和磷脂外流。然而，JAK2激活调控ABCA1与apoA-I结合的机制尚不清楚。此外，我们还发现apoA-I或载脂蛋白模拟肽与ABCA1的相互作用激活了STAT3途径。虽然JAK2激活是ABCA1去除脂质和最佳apoA-I结合活性所必需的，但STAT3激活并不参与脂质运输。研究表明，巨噬细胞中STAT3的结构性激活抑制了炎性细胞因子的产生，这意味着激活巨噬细胞中的STAT3的因子具有抗炎作用。事实上，我们发现，用apoA-I或其模拟肽预先处理表达ABCA1的J774巨噬细胞，可以激活STAT3，并显著减少随后由内毒素或脂蛋白A刺激的细胞因子的产生。我们推测，ABCA1除了可能具有抗炎作用的胆固醇输出活性外，还通过激活STAT3通路发挥抗炎信号受体的作用，而不依赖于其脂质输出活性。这个项目将 回答几个关键问题：1.激活JAK2将如何影响apoA-I或其模拟肽与ABCA1的相互作用，从而调节ABCA1介导的胆固醇外流？2：没有胆固醇外流的STAT3激活是否足以介导ABCA1与apoA-I或apoA-I模拟肽相互作用的抗炎作用？3：在激活ABCA1/JAK2/STAT3途径中具有更大和更特异活性的apoA-I模拟肽是否在介导ABCA1的胆固醇外流和抗炎效应方面具有优势？解决这些问题将大大促进我们对ABCA1介导的胆固醇外流的了解，并可能在开发针对ABCA1途径治疗心血管疾病的治疗剂方面开辟新的机会

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