Mechanisms of integrin signaling and a new anti-platelet/anti-inflammatory approach

家长补助金摘要： 血栓性心血管疾病仍然是美国的主要死亡原因， 世界血小板在止血和血栓形成中起关键作用。不仅 血小板粘附并聚集在血管损伤部位形成血栓，但 血小板还促进凝结（形成纤维蛋白凝块）。血小板血栓 形成和凝固是导致脑出血发病率和死亡率的重要因素。 血栓性疾病，如心脏病发作和中风。因此，抗血小板药物和抗- 开发了凝血剂并在临床上用于预防和治疗血栓形成。 然而，目前的抗血小板药物和抗凝剂存在不足。第一，反 血小板药物和抗凝剂都有出血的主要不良反应， 可能会危及生命此外，抗血小板药物在治疗中并不有效。 凝血，反之亦然，但联合使用抗血小板和抗凝剂 大大加剧了出血风险。因此，发展双 抗血小板和抗凝药物，不会引起出血。此外，委员会认为， 血栓形成可由慢性和急性炎性病症引起 动脉粥样硬化和败血症。相反，血栓形成会诱发和加剧 炎症因此，还高度期望开发一种药物，该药物比传统的药物更有效。 阿司匹林具有抗血栓和抗炎的功效。粘附的整合素家族 受体在血小板和白细胞中起关键作用。血小板整合素aIIbb 3 （GPIIb-IIIa），在激动剂刺激的由内而外信号传导激活后，不仅 介导血小板粘附和血栓形成，但也由外向内传播 导致血栓扩张和闭塞性血栓形成的信号， 主要止血。白细胞β2整合素，βLβ 2和βmβ 2，介导白细胞 粘附和由外向内信号传导，导致细胞迁移，细胞因子释放， 吞噬作用等，因此在炎症中起关键作用。我们最近发现， 整合素的由外向内信号传导需要G蛋白亚基Gβ 13与ExE的结合 基序保守的细胞质结构域的B12和B13。本提案项目1 目的是研究Gβ 13依赖的整合素由外向内信号转导的机制。 项目2是研究在剪切-和𝛽 激动剂诱导的血小板促凝活性，以及靶向的概念基础 Gβ 13-G β 3相互作用，以开发具有最小 出血风险。项目3是研究依赖于Gβ13的整合素β2在细胞外的作用。 在白细胞的促炎功能和严重脓毒症中的信号传导中， 开发抗血栓和抗炎双重药物的概念基础， 治疗严重败血症和其他血栓炎性疾病。

Abstract of Parent Grant: Thrombotic cardiovascular diseases remain the leading cause of death in US and world. Blood platelets play key roles in both hemostasis and thrombosis. Not only do platelets adhere and aggregate to form thrombi at the site of vascular injury, but platelets also facilitate coagulation (formation of a fibrin clot). Both platelet thrombus formation and coagulation are important contributors to the morbidity and mortality of thrombotic diseases such as heart attack and stroke. Thus, anti-platelet drugs and anti- coagulants were developed and are clinically used to prevent and treat thrombosis. However, current anti-platelet drugs and anti-coagulants have deficiencies. First, anti- platelet drugs and anti-coagulants all have the major adverse effect of bleeding, which can be life-threatening. Furthermore, anti-platelet drugs are not as effective in treating coagulation, and vice versa, but combined use of anti-platelets and anti-coagulants greatly exacerbates bleeding risk. Thus, it would be highly significant to develop dual anti-platelet and anti-coagulant drugs, which do not cause bleeding. Furthermore, thrombosis can be induced by chronic and acute inflammatory conditions such as atherosclerosis and sepsis. Conversely, thrombosis induces and exacerbates inflammation. Thus, it is also highly desirable to develop a drug that is more potent than aspirin in anti-thrombotic and anti-inflammatory efficacy. The Integrin family of adhesion receptors plays key roles in both in platelets and leukocytes. Platelet integrin aIIbb3 (GPIIb-IIIa), upon activation by inside-out signaling stimulated by agonists, not only mediates platelet adhesion and thrombus formation, but also transmits outside-in signals leading to thrombus expansion and occlusive thrombosis but is dispensable for primary hemostasis. Leukocyte 𝛽2 integrins, 𝛼L𝛽2 and 𝛼m𝛽2, mediate leukocyte adhesion and outside-in signaling, leading to cell migration, cytokine release, phagocytosis, etc., and thus play critical roles in inflammation. We recently showed that outside-in signaling of integrins requires the binding of G protein subunit G𝛼13 to an ExE motif conserved in the cytoplasmic domains of both 𝛽2 and 𝛽3. Project 1 of this proposal is to investigate the mechanisms of G𝛼13-dependent integrin outside-in signaling. Project 2 is to investigate the important role of 𝛽3 outside-in signaling in shear- and agonist-induced platelet procoagulant activity, and the conceptual basis for targeting G𝛼13- 𝛽3 interaction to develop a dual anti-platelet/anti-coagulant drug with minimal bleeding risk. Project 3 is to investigate the role of G𝛼13-dependent 𝛽2 integrin outside- in signaling in proinflammatory functions of leukocytes and in severe sepsis, and the conceptual basis for developing dual anti-thrombotic and anti-inflammatory drugs for treating severe sepsis and other thrombo-inflammatory conditions.