AIBP-Mediated Cholesterol Efflux and Angiogenesis

描述(由申请人提供)：在美国，心肌梗死是导致死亡和发病率的主要原因。再灌注后，血管生成和微循环的恢复是恢复正常心功能的重要组成部分。血管生成对斑马鱼心脏再生也很重要。在了解血管生成的分子机制方面已经取得了很大的进展，但对代谢和血管生成之间的联系的研究较少。我的初步研究强烈表明，内皮细胞的胆固醇外流调节血管生成。我发现斑马鱼在体外和胚胎中的血管生成是由ApoA-I结合蛋白(AIBP)调节的，AIBP是一种分泌蛋白，在一系列与ApoA-I物理相关的蛋白质中被鉴定出来。AIBP促进Abcg1介导的血管内皮细胞胆固醇外流。此外，AIBP控制斑马鱼胚胎节段性动脉(SEA)的形成。AIBP的过表达抑制了SEA的萌发，而AIBP的敲除导致了SEA的萌发和分枝的失调。在我指导的K99阶段，我建议测试这样一个假设，即分泌AIBP作为EC胆固醇外流的部位特异性调节因子，并调控胚胎血管生成。首先，我计划证明AIBP介导的ABC转运体依赖的胆固醇外流调节斑马鱼胚胎血管的生成。我发现AIBP缺失引起的表型是通过细胞胆固醇转运蛋白ABCA1和Abcg1被敲除而产生的。我的目的是证明AIBP对胚胎血管生成的影响依赖于AIBP在胆固醇代谢中的作用。这些研究将建立一个先前未知的机制，将胆固醇外流与胚胎血管生成联系起来。然后在我独立的R00阶段，我将证明AIBP在成年斑马鱼中的过度表达会减弱心脏再生。冠状动脉血管的形成被认为对心脏再生很重要，因为可以想象，它为心肌细胞的强劲增殖提供了必要的资源。我将建立一个AIBP条件表达转基因鱼系，并研究AIBP过表达对斑马鱼心脏再生过程中血管生成的影响。我在独立R00阶段的第二个目标是评估AIBP表达对小鼠冠状动脉血管生成的调节作用。由于我的结果提示AIBP限制血管生成，我认为在心肌肥厚的情况下，心肌细胞特异性缺失AIBP可以促进血管生成。这些研究将阐明AIBP调控的血管生成在心脏再生和心肌肥厚中的潜在作用，并提出可能的治疗干预措施，通过促进血管生成来刺激微血管的恢复。

DESCRIPTION (provided by applicant): Myocardial infarction is the leading cause of mortality and morbidity in the US. Following reperfusion, angiogenesis and restoration of microcirculation is a critical component in the recovery of normal cardiac function. Angiogenesis is also important for zebrafish heart regeneration. Much progress has been made towards understanding of the molecular mechanisms of angiogenesis, but the connection between metabolism and angiogenesis is less studied. My preliminary studies strongly suggest that cholesterol efflux from endothelial cells regulates angiogenesis. I found that angiogenesis in vitro and in embryonic zebrafish was regulated by ApoA-I binding protein (AIBP), a secreted protein identified in a screen of proteins that physically associate with ApoA-I. AIBP accelerated ABCG1-mediated cholesterol efflux from endothelial cells (EC) in vitro. Furthermore, AIBP controlled formation of segmental arteries (SeA) in embryonic zebrafish. Overexpression of AIBP inhibited SeA sprouting, while AIBP knockdown resulted in dysregulated SeA sprouting and branching. In my mentored K99 phase, I propose to test the hypothesis that secreted AIBP functions as a site-specific regulator of cholesterol efflux from EC and governs embryonic angiogenesis. First, I plan to demonstrate that AIBP-mediated, ABC transporters-dependent cholesterol efflux regulates embryonic angiogenesis in zebrafish. I found that the phenotype caused by the loss of AIBP was phenocopied by knockdown of cellular cholesterol transporters ABCA1 and ABCG1. My goal in this Aim is to prove that the effect of AIBP on embryonic angiogenesis relies on the AIBP function in cholesterol metabolism. These studies will establish a previously unrecognized mechanism connecting cholesterol efflux with embryonic angiogenesis. Then in my independent R00 phase, I will demonstrate that AIBP overexpression in adult zebrafish attenuates heart regeneration. Formation of coronary vasculature is believed to be important for heart regeneration because it conceivably provides resources necessary for robust proliferation of cardiomyocytes. I will make an AIBP conditional expression transgenic fish line, and investigate the impact of AIBP overexpression on angiogenesis that occurs during zebrafish heart regeneration. My second Aim in the independent R00 phase is to assess that AIBP expression modulates coronary angiogenesis in mice. Because my results suggest that AIBP limits angiogenesis, I propose that cardiomyocyte-specific loss of AIBP would promote angiogenesis under conditions of cardiac hypertrophy. These studies will elucidate a potential role for AIBP-governed angiogenesis in heart regeneration and in cardiac hypertrophy and suggest possible therapeutic interventions to stimulate the recovery of the microvasculature by promoting angiogenesis.