THROMBIN SIGNALING IN HEMOSTASIS AND THROMBOSIS

描述（改编自摘要） 这是为响应RFA HL-99-015而提交的三个协作RO之一 关于动脉血栓形成申请人提案的总体目标是定义 激活血小板的信号传导机制，从而提供 治疗开发和风险因素识别的框架。目标 这个项目的目的是确定凝血酶信号在 止血和血栓形成。凝血酶通过蛋白酶激活血小板 G蛋白偶联受体（PARs）。申请人应使用缺乏以下能力的小鼠： 这些受体问：1）血小板中的凝血酶信号传导是否是 正常止血吗PAR 3和PAR 4是已知的凝血酶受体， 参与小鼠血小板活化。mPAR 3似乎并不 介导跨膜信号传导，但作为mPAR 4的辅因子 通过低浓度凝血酶的切割和活化。因此 申请人预期PAR 4是小鼠中凝血酶信号传导所需的 血小板申请人将使用PAR 4缺陷小鼠来测试 凝血酶信号在止血中的作用。2)是否衰减或消融 血小板中的凝血酶信号抑制血栓形成？人血小板使用PAR 1 和PAR 4用于凝血酶信号传导，并且不知道PAR 1的抑制是否 和/或PAR 4的组合物将可用于预防或治疗血栓形成。PAR3- 缺陷型小鼠血小板类似于PAR 1抑制的人血小板 (both依赖于PAR 4进行凝血酶信号传导）。PAR 4缺陷小鼠血小板 将可能证明类似于人类血小板，其中所有凝血酶信号传导 被封锁了申请人将使用PAR 3和PAR 4缺陷型小鼠， 确定是否部分或完全抑制凝血酶信号传导， 血小板防止动脉和微血管血栓形成。3)是 通过凝血酶或其它蛋白酶的内皮细胞活化， 止血和血栓形成申请人假设， 内皮PAR 1和PAR 2通过促进血栓形成和炎症， 血小板和白细胞滚动和粘附。申请人将决定 PAR 1和/或PAR 2缺陷的小鼠是否在以下模型中得到保护： 炎症以及微血管和动脉血栓形成。4)做功能增益 血小板G蛋白偶联受体（GPCRs）突变促进血栓形成？ 在调节细胞因子的基因中发现血栓前突变 行为已经落后于编码血浆蛋白的基因。 几种人类疾病由GPCR中的功能获得性突变介导。 申请人将使用携带PAR 4功能获得性突变的小鼠， 确定这种GPCR突变，单独或与 其他基因，可能是血栓形成的基础。

DESCRIPTION (Adapted from abstract) This is one of three collaborative ROls submitted in response to RFA HL-99-015 on Arterial Thrombosis. The applicants proposal's overall goal is to define the signaling mechanisms by which platelets are activated, thereby providing a framework for therapeutic development and risk factor identification. The goal of this individual project is to define the role of thrombin signaling in hemostasis and thrombosis. Thrombin activates platelets via proteaseactivated G protein-coupled receptors (PARs). The applicants shall use mice deficient in these receptors to ask: 1) Is thrombin signaling in platelets necessary for normal hemostasis? PAR3 and PAR4 are the thrombin receptors known to participate in mouse platelet activation. It appears that mPAR3 does not mediate transmembrane signaling but instead acts as a cofactor for mPAR4 cleavage and activation by low concentrations o f thrombin. Thus the applicants expect PAR4 to be required for thrombin signaling in mouse platelets. The applicants will use PAR4-deficient mice to test the importance of thrombin signaling in hemostasis. 2) Does attenuation or ablation of thrombin signaling in platelets inhibit thrombosis? Human platelets use PAR1 and PAR4 for thrombin signaling, and it is unknown whether inhibition of PAR1 and/or PAR4 would be useful for preventing or treating thrombosis. PAR3- deficient mouse platelets are analogous to PARl-inhibited human platelets (both rely on PAR4 for thrombin signaling). PAR4-deficient mouse platelets will likely prove analogous to human platelets in which all thrombin signaling has been blocked. The applicants will use PAR3- and PAR4-deficient mice to determine whether partial or complete inhibition of thrombin signaling in platelets protects against arterial and microvascular thrombosis. 3) Is endothelial cell activation by thrombin or other proteases important in hemostasis and thrombosis? The applicants hypothesize that activation of endothelial PAR1 and PAR2 promotes thrombosis and inflammation by promoting platelet and leukocyte rolling and adhesion. The applicants will determine whether mice deficient in PAR1 and/or PAR2 are protected in models of inflammation and microvascular and arterial thrombosis. 4) Do gain-of-function mutations in platelet G protein-coupled receptors (GPCRs) promote thrombosis? The discovery of prothrombotic mutations in genes that regulate cellular behaviors has lagged that in genes encoding the plasma proteins. Several human diseases are mediated by gain-of-function mutations in GPCRs. The applicants will use mice bearing gain-of-function mutations in PAR4 to determine if such GPCR mutations, alone or in combination with mutations in other genes, might be a basis for thrombophilia.