PLASMA FIBRONECTIN IN PLATELET HEMOSTATIC FUNCTION

在止血和血栓栓塞性疾病中，血小板起着核心作用 部分彼此粘连(聚集)或管壁粘连(粘连)。 这些反应在一定程度上是通过与一类大型 二硫键连接的糖蛋白。我们发现凝血酶能诱导 其中一种糖蛋白纤维连接蛋白的特异性和可饱和性结合 (FN)到血小板。根据我们的初步数据，我们预计 FN与血小板相互作用涉及的四个步骤如图所示 下面。静息细胞大于Fn结合部位II大于Fn 绑定III大于FN处理IV大于功能性。我们会 剖析并定义反应中的每个单独步骤 序列。反应I描述了FN结合位点的诱导 对血小板的刺激。我们将确定哪些刺激有效，哪些无效。 使用分泌性和非分泌性刺激支持FN绑定。这个 作为一种手段，将研究选定药物对FN结合的影响 确定结合位点诱导所需的生化途径。 反应II需要FN与血小板结合。的影响 环境条件，如温度，pH和二价离子，将是 以及由血小板识别的Fn的结构域 将会被定义。此外，还将使用多种方法来确定 FN的结合部位。将特别强调以下方面的作用 根据我们的初步数据，纤维蛋白(原)在纤维连接蛋白结合中。反应III 需要处理与血小板结合的FN，我们将调查 转谷氨酰胺酶对血小板表面纤维蛋白原的交联作用 FN的二硫键、内化及其相互作用 细胞骨架元素。反应IV涉及的功能后果是 FN与血小板的结合，作为初始结合或 后续处理。它对血小板聚集和黏附的影响， 血栓回缩和单核细胞-血小板相互作用是可能的 将探索的候选事件。

Platelets play a central role in hemostasis and thromboembolic disease, in part adherence to each other (aggregation) or vessel walls (adhesion). These reactions are mediated in part by interactions with a class of large disulfide-linked glycoproteins. We have found that thrombin induces specific and saturable binding of one of these glycoproteins, fibronectin (fn) to platelets. Based on our preliminary data, we envision the interaction of fn with the platelet to involve the four steps diagrammed below. Resting Cell greater than FN Binding Site II greater than Fn Binding III greater than Fn Processing IV greater than Functional. We will dissect and define each of these individual steps in the reaction sequence. Reaction I describes the induction of the fn binding site by platelet stimulation. We shall identify stimuli which do and do not support fn binding using both secretory and non secretory stimuli. The effect of selected drugs on fn binding will be investigated as a means of defining biochemical pathways required for binding site induction. Reaction II entails fn binding to the platelet. The effect of environmental conditions such as temperature, pH and divalent ions, will be established, and the domains of fn which are recognized by the platelet will be defined. In addition, multiple approaches will be used to identify the binding site for fn. Particular emphasis will be given to the role of fibrin(ogen) in fn binding based on our preliminary data. Reaction III entails processing of platelet-bound fn, and we shall investigate cross-linking of fn on the platelet surface via transglutaminases or disulfide bonding, internalization of fn, and interactions with cytoskeletal elements. Reaction IV involves the functional consequences of fn binding to the platelet, either as a result of initial binding or subsequent processing. Its effect on platelet aggregation and adhesion, clot retraction and monocyte-platelet interaction represent likely candidate events which will be explored.