Protease-activated receptors in embryonic development

描述（由申请人提供）：在成人中，蛋白酶激活受体（PAR）对凝血蛋白酶产生应答，以帮助协调参与止血、炎症和修复的细胞应答。在前一个项目期间，我们发现PAR在胚胎发育中也起着独特而重要的作用。事实上，内皮细胞中的PAR 1信号传导是小鼠胚胎中发育血管的适当重塑和/或完整性所必需的。PAR 1在血管形成过程中监测哪些生化和生理过程？哪些内皮细胞对PAR 1激活的反应对血管正常发育很重要？我们假设凝血级联和PAR共同提供了一个监测和调节血管形成、重塑和发育中血管完整性的系统。为了验证这一假设，我们首先要确定PARs是否在小鼠胚胎发育过程中感知凝血蛋白酶，以及PARs的激活是否解释了凝血因子在这种情况下的作用。具体问题包括：a）PAR联合缺乏症是否表现为组织因子缺乏症？B）组织因子在血管中或血管周围的表达是否是支持胚胎发育所必需和充分的？和c）携带凝血酶原突变的胚胎可以通过PAR 1中的互补突变来拯救吗？接下来，我们将通过消除小鼠胚胎内皮细胞中特异性G蛋白通路的功能来确定哪些信号通路对血管发育期间内皮细胞中PAR 1和其他GPCR的功能是重要的。我们希望这些研究能够阐明凝血级联反应和PAR的新作用，并提供有关血管发育机制的新见解，也许在其他环境中形成新的血管。

DESCRIPTION (provided by applicant): In the adult, protease-activated receptors (PARs) respond to coagulation proteases to help orchestrate cellular responses involved in hemostasis, inflammation and repair. In the previous project period, we showed that PARs also play distinct and important roles in embryonic development. Indeed, PAR1 signaling in endothelial cells is required for proper remodeling and/or integrity of developing blood vessels in mouse embryos. What biochemical and physiological processes does PAR1 monitor during blood vessel formation? Which endothelial cell responses to PAR1 activation are important for proper vessel development? We hypothesize that the coagulation cascade and PARs together provide a system for monitoring and regulating the formation, remodeling, and integrity of developing blood vessels. Toward testing this hypothesis we shall first determine whether PARs sense coagulation proteases during mouse embryonic development, and whether activation of PARs account for the roles of coagulation factors in this context. Specific questions include a) Does combined deficiency of PARs phenocopy tissue factor deficiency? b) Is tissue factor expression in or around blood vessels necessary and sufficient to support embryonic development? and c) Can embryos bearing prothrombin mutations be rescued by complementary mutations in PAR1? We shall next determine which signaling pathways are important for the function of PAR1 and other GPCRs in endothelial cells during vascular development by ablating the function of specific G protein pathways in endothelial cells in the mouse embryo. We expect these studies to illuminate a novel role for the coagulation cascade and PARs and to provide new insights regarding the mechanisms governing vascular development and perhaps new blood vessel formation in other settings.