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起作用。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，动脉粥样硬化的发生和进展会减少。这一发现产生了稳定层流对动脉粥样硬化有保护作用的概念。该建议的主要假设是，稳定层流引发的内皮细胞（EC）信号转导事件通过减少炎症来限制动脉粥样硬化。我们的实验室主要研究有丝分裂原活化蛋白激酶（MAPK）的流动调节。在之前的资助期间，我们测试了一个假设，即了解血流调节细胞因子激活c-Jun n -末端激酶（INK）的机制，将有助于深入了解血流诱导的动脉粥样硬化保护机制。当我们发现两个分子-硫氧还蛋白和大MAPK-1 (BMK1) -受血流调节并抑制TNF对INK的激活时，这一假设得到了验证。我们的实验室首次证明了血流激活了EC中的BMK1。BMK1在EC功能中的重要性已被证实，BMK1缺失的小鼠表现出EC形态和血管形成缺陷，导致胚胎死亡。基于初步数据，我们提出了一种涉及血小板内皮细胞粘附分子(PECAM1)-SHP2磷酸酶- gabl接头蛋白- mekk3 - mek5 - bmkl的BMK1激活的机械转导途径。为了确定这一途径介导稳定层流的动脉粥样硬化保护作用的程度，我们提出了四个目标。1)表明PECAM1是血流诱导的BMK1激活所必需的机械传感器。2)表明Gabl易位和酪氨酸磷酸化是血流介导的BMK1激活所必需的。3)发现含有Phox和Beml （FBI）结构域的蛋白通过激活BMK1的流动来指定MEKK3-MEK5信号复合物的组装，而不是INK。4)表征内皮特异性BMK1缺失或激活对ApoE敲除小鼠动脉粥样硬化的影响。这些研究将为血流抑制血管炎症的机制提供洞见，并促进限制动脉粥样硬化的新治疗方法的发展。

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.