The cGMP-dependent protein kinase pathway in platelets

血小板中 cGMP 依赖性蛋白激酶途径

基本信息

批准号：
7819163
负责人：
Xiaoping Du
金额：
$ 1.95万
依托单位：
UNIVERSITY OF ILLINOIS AT CHICAGO
依托单位国家：
美国
项目类别：
财政年份：
2009
资助国家：
美国
起止时间：
2009-06-01 至 2010-08-31
项目状态：
已结题

项目摘要

Platelet activation play critical roles in the development of thrombotic diseases such as heart attack and stroke. The roles of platelets in thrombosis involves two major aspects: Firstly, platelet adhesion, aggregation and secretion of granule contents are important in the development of atherosclerosis, which causes chronic vascular injury. Secondly, platelet activation at the site of vascular injury is critical in initiating arterial thrombosis. An intracellular secondary messenger molecule, cGMP, is synthesized during platelet activation. The role of cGMP in platelet activation has been controversial since the discovery of cGMP. It has been a prevailing concept in the past 30 years that cGMP, by activating the cGMP-dependent protein kinase (PKG), inhibits platelet activation. This concept, however, has been challenged by our recent finding that cGMPand PKG play a biphasic role in platelet activation, We show that cGMP plays a stimulatory role when low concentrations of cGMP is produced upon platelet agonist stimulation, but becomes inhibitory at high cGMP concentrations. During the last funding period, we have made significant progress in understanding the mechanisms of the biphasic roles of the cGMP pathway in platelet activation. We have found that the cGMP-PKG pathway plays a general role in stimulating platelet secretion and secretion-dependent platelet aggregation induced by most platelet agonists. We have obtained evidence supporting a new upstream signaling pathway of cGMP during platelet activation involving phosphoinositide 3-kinase, various forms of Akt and nitric oxide (NO) synthase. We have also obtained evidence supporting a novel downstreamsignaling mechanism of cGMP involving various isoforms of PKG and PKG-dependent sequentially activation of p38 and ERK mitogen-activated protein kinase pathways. These discoveries allow us to hypothesize a novel signaling pathwaythat stimulates platelet secretion. In this pathway, platelet agonists, by activating different isoforms of PI3K, Akt, NOS3,soluble guanylyl cyclase, and PKG, and via the p38 and ERK pathways, induce platelet secretion, which amplifies and stabilizes platelet aggregation. To test this hypothesis, we propose following specific aims: 1.To investigate the role of different Akt isoforms as upstream activators of the cGMP pathway during platelet activation. 2. To determine mechanisms of agonist-induced platelet NO production, its regulation, and its role in platelet secretion and aggregation. 3.To characterize the roles and the signaling mechanisms of different isoforms of PKGin platelet secretion and aggregation.

血小板激活在心脏病和中风等血栓性疾病的发展中起着至关重要的作用。这血小板在血栓形成中的作用涉及两个主要方面：一是血小板的粘附、聚集和分泌颗粒内容物在动脉粥样硬化的发展中很重要，动脉粥样硬化会导致慢性血管损伤。第二，血管损伤部位的血小板活化对于引发动脉血栓形成至关重要。细胞内次级信使分子 cGMP 在血小板活化过程中合成。 cGMP 在血小板活化中的作用自 cGMP 发现以来一直备受争议。在过去的 30 年里，cGMP 已成为一个流行的概念，激活 cGMP 依赖性蛋白激酶 (PKG)，抑制血小板活化。然而这个概念已经被受到我们最近发现 cGMP 和 PKG 在血小板活化中发挥双相作用的挑战，我们证明 cGMP 当血小板激动剂刺激产生低浓度的 cGMP 时，发挥刺激作用，但高 cGMP 浓度下具有抑制作用。在上一个资助期间，我们在以下方面取得了重大进展：了解 cGMP 途径在血小板激活中的双相作用机制。我们发现 cGMP-PKG 通路在刺激血小板分泌和分泌依赖性血小板聚集中发挥一般作用由大多数血小板激动剂诱导。我们已获得支持 cGMP 新上游信号通路的证据血小板激活过程中涉及磷酸肌醇 3-激酶、各种形式的 Akt 和一氧化氮 (NO) 合酶。我们还获得了支持涉及各种亚型的 cGMP 下游信号传导机制的证据 PKG 和 p38 和 ERK 丝裂原激活蛋白激酶途径的 PKG 依赖性顺序激活。这些这些发现使我们能够假设一种刺激血小板分泌的新信号通路。在此途径中，血小板激动剂，通过激活 PI3K、Akt、NOS3、可溶性鸟苷酸环化酶和 PKG 的不同亚型，并通过 p38 和 ERK 通路诱导血小板分泌，从而放大并稳定血小板聚集。为了检验这个假设，我们提出以下具体目标： 1. 研究不同 Akt 亚型作为 cGMP 上游激活剂的作用血小板活化过程中的途径。 2. 确定激动剂诱导血小板 NO 产生的机制，其调节及其在血小板分泌和聚集中的作用。 3.描述角色和信号机制 PKGin 血小板分泌和聚集的不同亚型。