Protein S Regulates Blood Coagulation by Inhibiting Factor IXa

S蛋白(PS)是一种血浆抗凝剂，对维持止血至关重要。 PS的缺乏或异常可导致血栓形成，如肺 栓塞症、深静脉血栓形成和急性小血管凝血。PS是一种非 激活蛋白C和组织因子途径抑制物的酶辅助因子。最近， 我们发现PS抑制促凝血剂FixA。这一重大发现很可能解释了 与PS缺乏相关的血栓病理。因此，我们寻求推导出一个完整的 理解FixA和PS之间的相互作用并明确其重要性 PS-FixA相互作用，不包括PS与APC和TFPI的相互作用。身份识别 PS-FixA相互作用的生化细节将使开发一种PS的小衍生产品成为可能 可以治疗FixA活动过多(和凝血过多)和PS的患者 缺陷缺陷或异常。 我们已经将PS结合位点准确地定位到FixA的肝素结合位点，并鉴定了HBE PS-Fixa结合所需的残留物。我们已经确定了GLA和EGF结构域 FixA有助于与PS相互作用的稳定性，我们发现孤立的 PS的层粘连蛋白G1+2结构域是FixA的有效抑制剂。 对于这个项目，我们将使用以下体内和体外方法来实现 彻底了解PS与FixA的相互作用：(1)确认PS结构域 FixA抑制，(2)确定FixA抑制所需的PS残基，以及(3)定义体内 FixA与PS LG结构域和单位点LG结构域突变体的相互作用。分子和 从本研究中获得的生化知识将为创造PS- 派生FixA抑制分子治疗PS所致血栓形成 FixA缺乏或上调。

Protein S (PS), a plasma anticoagulant, is vital for the maintenance of hemostasis. Deficiencies or abnormalities in PS can lead to thrombotic conditions such as pulmonary embolism, deep vein thrombosis, and acute small blood vessel coagulation. PS is a non- enzymatic cofactor for Activated Protein C and for Tissue Factor Pathway Inhibitor. Recently, we discovered that PS inhibits procoagulant FIXa. This significant finding likely explains the thrombotic pathology associated with PS deficiency. Thus, we seek to derive a complete understanding of the interaction between FIXa and PS and to establish the explicit importance of the PS-FIXa interaction, exclusive of PS interactions with APC and TFPI. Identification of the biochemical details of PS-FIXa interaction will enable development a small derivative of PS that could treat individuals who have excess FIXa activity (and excess blood clotting) and PS deficiencies or abnormalities. We have pinpointed the PS binding site to FIXa’s heparin-binding site and identified HBE residues necessary for PS-FIXa binding. We have established that the Gla and EGF domains of FIXa contribute to the stability of the interaction with PS, and we discovered that the isolated Laminin G1+2 domains of PS are effective inhibitors of FIXa. For this project, we will use the following in vivo and in vitro approaches to achieve a thorough understanding of the interaction of PS with FIXa: (1) Confirm PS domains required for FIXa inhibition, (2) Identify PS residues required for FIXa inhibition, and (3) Define the in vivo interaction of FIXa with PS LG domains and single-site LG domain mutants. The molecular and biochemical knowledge obtained from this study will provide the basis for creation of a PS- derived FIXa-inhibiting molecule for the treatment of thrombotic conditions caused by PS deficiency or upregulation of FIXa.