Subcellular mechanisms of platelet activation

描述（由申请人提供）：血小板积累是止血的标志，也是心脏病发作和中风的诱因。在之前的工作中，我们和其他人专注于鉴定支持血小板活化的分子。在这里，我们尝试一种范式转变，将血小板激活视为一个灵活的信号网络的产物，而不是一系列途径的集合，并将关于该网络运作的可测试想法与体内血小板激活的高分辨率成像结合起来。我们的目标是了解血小板信号网络如何形成止血反应，以及止血反应如何影响网络。我们的初步研究表明，穿透性损伤的反应不是血小板和纤维蛋白的均匀团块，而是由不同的细胞组成的分层结构

DESCRIPTION (provided by applicant): Platelet accumulation is a hallmark of hemostasis and a contributor to heart attacks and strokes. In previous work, we and others have focused on identifying molecules that support platelet activation. Here we attempt a paradigm shift, approaching platelet activation as the product of a flexible signaling network rather than a collection of pathways, and joining testable ideas about the operation of that network to high resolution imaging of platelet activation in vivo. Our goal is to understand how the platelet signaling network shapes the hemostatic response and how the hemostatic response impacts the network. Our initial studies show that, rather than a homogeneous mass of platelets and fibrin, the response to penetrating injuries yields a hierarchical structure comprised of distinct regions that vary in the extent of platelet activation, packing density and porosity. A prominent feature is a core of fully-activated platelets overlaid with an unstable shell of less-activated platelets, but additional domains are present as well. Greater packing in the core allows adjacent platelets to interact, generating contact-dependent signals. Within the core is a region where thrombin activation and fibrin deposition occur. Our hypothesis is that all parts of this structure are subject to the platelet signaling network, with the core providing thrombus stabilit and gradients of soluble agonists determining the extent of thrombus growth and the size of the shell. Aim #1 will test and extend this model, applying additional activation markers, developing new methods for tracking individual platelets in vivo, and exploiting a newly- developed thrombin biosensor. Aim #2 will map relationships between the platelet signaling network and the structure of the hemostatic mass, and reassess the impact of anti-platelet agents in the context of a hierarchical model of hemostasis. Aim #3 will test the novel hypothesis that contact-dependent events are separated spatially and temporally into sets that either promote or restrain the thrombus core. Through these aims, we hope to determine why multiple agonists and signals are needed to shape an optimal platelet response, account for differences in the impact of antiplatelet agents, and show how pathological conditions can subvert normal responses by effects on the platelet signaling network.