Fluid Shear Stress Signal Transduction in Endothelium

描述（由申请人提供）：炎症在临床显著动脉粥样硬化发展的每个阶段都有贡献。与湍流和低流量区域相比，在与高层流剪切应力相关的稳定流动区域中，动脉粥样硬化的发生和进展减少。这一发现产生了稳定层流具有动脉粥样硬化保护作用的概念。该提议的主要假设是，稳定层流引起的内皮细胞（EC）中的信号转导事件通过减少炎症来限制动脉粥样硬化。我们的实验室一直专注于有丝分裂原活化蛋白激酶（MAPK）的流量调节。在上一个资助期，我们测试的假设，了解流动调节c-Jun N-末端激酶（INK）激活的细胞因子的机制，将提供洞察流动诱导的动脉粥样硬化保护机制。这一假设得到了验证，因为我们发现了两种分子-硫氧还蛋白和大MAPK-1（BMK 1）-受流量调节并抑制TNF激活的INK。我们的实验室首次表明，流动激活EC中的BMK 1。BMK 1在EC功能中的重要性已经通过BMK 1缺失小鼠表现出缺陷的EC形态和血管形成导致胚胎死亡的发现得到验证。基于初步的数据，我们提出了一种BMK 1激活的机械转导途径，涉及血小板内皮细胞粘附分子（PECAM 1）-SHP 2磷酸酶-Gabl衔接蛋白-MEKK 3-MEK 5-BMK 1。为了确定这一途径在多大程度上介导稳定层流的动脉粥样硬化保护作用，我们提出了四个目标。1)表明PECAM 1是流动诱导的BMK 1激活所必需的机械传感器。2)显示Gabl易位和酪氨酸磷酸化是血流介导的BMK 1活化所必需的。3)显示含有Phox和Beml（FBI）结构域的蛋白质通过激活BMK 1但不激活INK的流动指定MEKK 3-MEK 5信号传导复合物的组装。4)在ApoE敲除小鼠中表征内皮特异性BMK 1缺失或激活对动脉粥样硬化的影响。这些研究应该提供深入了解流动抑制血管炎症的机制，并促进新的治疗方法的发展，以限制动脉粥样硬化。

DESCRIPTION (provided by applicant): Inflammation contributes at each stage in the development of clinically significant atherosclerosis. The initiation and progression of atherosclerosis is decreased in regions of steady flow associated with high laminar shear stress, compared to regions of turbulent and low flow. This finding has yielded the concept that steady laminar flow is atheroprotective. The major hypothesis of this proposal is that signal transduction events in endothelial cells (EC) elicited by steady laminar flow limit atherosclerosis by decreasing inflammation. Our laboratory has focused on regulation of the mitogen activated protein kinases (MAPK) by flow. During the previous grant period we tested the hypothesis that understanding the mechanisms by which flow regulates c-Jun N-terminal kinase (INK) activation by cytokines will provide insight into the atheroprotective mechanisms induced by flow. The hypothesis was validated as we discovered two molecules - thioredoxin and Big MAPK-1 (BMK1) - that were regulated by flow and inhibited INK activation by TNF. Our lab was first to show that flow activated BMK1 in EC. The importance of BMK1 in EC function has been validated by the findings that BMK1 null mice display defective EC morphology and blood vessel formation leading to embryonic lethality. Based on preliminary data we propose a mechanotransduction pathway for BMK1 activation that involves platelet endothelial cell adhesion molecule (PECAM1)-SHP2 phosphatase-Gabl adaptor protein-MEKK3-MEK5-BMKl. To define the extent to which this pathway mediates the atheroprotective effects of steady laminar flow we propose four aims. 1) Show that PECAM1 is a mechanosensor necessary for flow-induced BMK1 activation. 2) Show that Gabl translocation and tyrosine phosphorylation are required for flow-mediated BMK1 activation. 3) Show that Phox and Beml (FBI) domain-containing proteins specify assembly of a MEKK3-MEK5 signaling complex by flow that activates BMK1, but not INK.. 4) Characterize the effect of endothelial-specific BMK1 deletion or activation on atherosclerosis in ApoE knockout mice. These studies should provide insight into mechanisms by which flow inhibits vascular inflammation and facilitate development of new therapeutic approaches to limit atherosclerosis.