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（PARs）对凝血蛋白酶作出反应，帮助协调参与止血、炎症和修复的细胞反应。在之前的项目期间，我们发现PARs在胚胎发育中也发挥着独特而重要的作用。事实上，内皮细胞中的PAR1信号对于小鼠胚胎中血管发育的适当重塑和/或完整性是必需的。PAR1在血管形成过程中监测哪些生化和生理过程？内皮细胞对PAR1激活的哪些反应对血管发育是重要的？我们假设凝血级联和PARs共同提供了一个监测和调节血管形成、重塑和完整性的系统。为了验证这一假设，我们将首先确定PARs是否在小鼠胚胎发育过程中感知凝血蛋白酶，以及PARs的激活是否在此背景下解释凝血因子的作用。具体问题包括：a) PARs联合缺乏是否表现为组织因子缺乏？b)血管内或血管周围的组织因子表达是否足以支持胚胎发育？c)携带凝血酶原突变的胚胎能否通过PAR1的互补突变获救？接下来，我们将通过研究小鼠胚胎内皮细胞中特定G蛋白通路的功能，确定哪些信号通路对血管发育过程中内皮细胞中PAR1和其他gpcr的功能起重要作用。我们希望这些研究能够阐明凝血级联和PARs的新作用，并为其他情况下血管发育和新血管形成的机制提供新的见解。

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.