Downstream molecular mechanisms underlying cerebral cavernous malformation

摘要-项目3 我们小组和其他人最近的研究已经确定MEKK 3-KLF 2/4信号传导是 CCM复合功能的直接靶点，并表明CCM功能的丧失赋予 通过获得MEKK 3信号和KLF 2和KLF 4升高形成病变 在脑内皮细胞中的表达。出乎意料的是，我们还发现， 肠道中革兰氏阴性菌来源的脂多糖对TLR 4的激活作用 微生物组在MEKK 3-KLF 2/4信号传导的激活中起着核心的上游作用 以及小鼠和人类的CCM形成。这些发现最终导致了现在 广泛接受的CCM疾病模型，但KLF 2的下游效应物 和KLF 4驱动损伤形成仍然未知。我们的初步研究显示 对驱动CCM形成的下游事件的新见解：1） 功能与CCM功能丧失协同作用，导致小鼠病变形成， 大多数手术切除的人CCM病变，和2）ADAMTS切割的α- 血管多功能蛋白聚糖驱动小鼠中的CCM表型。项目3将确定以下方面的作用： 使用已建立的和已证实的方法研究CCM发病过程中的PI 3 K信号传导和多功能蛋白聚糖蛋白水解， 新开发的小鼠遗传模型。这些研究将有力地补充那些 在项目1和核心A中，研究了人类CCM病变中的PIK 3CA突变， 一种细胞非自主机制，野生型内皮细胞通过该机制促进 CCM病变。最重要的是，我们希望这些研究能够迅速转化为 通过为使用FDA批准的药物（如PI 3 K）提供支持， 途径抑制剂雷帕霉素治疗CCM疾病。

SUMMARY – PROJECT 3 Recent studies by our group and others have identified MEKK3-KLF2/4 signaling as the direct target of CCM complex function, and showed that loss of CCM function confers lesion formation through gain of MEKK3 signaling and elevated KLF2 and KLF4 expression in brain endothelial cells. Unexpectedly, we have also found that endothelial TLR4 activation by lipopolysaccharide derived from gram negative bacteria in the gut microbiome plays a central, upstream role in the activation of MEKK3-KLF2/4 signaling and CCM formation in both mice and humans. These findings have culminated in a now widely accepted model of CCM disease, but the downstream effectors by which KLF2 and KLF4 drive lesion formation remain unknown. Our preliminary studies reveal two new insights into the downstream events that drive CCM formation: 1) PI3K gain of function synergizes with CCM loss of function to drive lesion formation in mice and a majority of surgically resected human CCM lesions, and 2) ADAMTS cleavage of peri- vascular versican drives the CCM phenotype in mice. Project 3 will define the roles of PI3K signaling and versican proteolysis during CCM pathogenesis using established and newly developed mouse genetic models. These studies will strongly complement those in Project 1 and Core A that examine the PIK3CA mutations in human CCM lesions and a cell non-autonomous mechanism by which wild-type endothelial cells contribute to CCM lesions. Most importantly, we expect these studies to be rapidly translated to the clinic by providing support for the use of FDA-approved agents such as the PI3K pathway inhibitor rapamycin to treat CCM disease.