Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom.
Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom.
Sci Rep. 2018 Jul 3;8(1):9987. doi: 10.1038/s41598-018-28363-4.
Platelets protect the vascular system during damage or inflammation, but platelet activation can result in pathological thrombosis. Activated platelets release a variety of extracellular vesicles (EVs). EVs shed from the plasma membrane often expose phosphatidylserine (PS). These EVs are pro-thrombotic and increased in number in many cardiovascular and metabolic diseases. The mechanisms by which PS-exposing EVs are shed from activated platelets are not well characterised. Cholesterol-rich lipid rafts provide a platform for coordinating signalling through receptors and Ca channels in platelets. We show that cholesterol depletion with methyl-β-cyclodextrin or sequestration with filipin prevented the Ca-triggered release of PS-exposing EVs. Although calpain activity was required for release of PS-exposing, calpain-dependent cleavage of talin was not affected by cholesterol depletion. P2Y and TPα, receptors for ADP and thromboxane A, respectively, have been reported to be in platelet lipid rafts. However, the P2Y antagonist, AR-C69931MX, or the cyclooxygenase inhibitor, aspirin, had no effect on A23187-induced release of PS-exposing EVs. Together, these data show that lipid rafts are required for release of PS-exposing EVs from platelets.
血小板在损伤或炎症期间保护血管系统，但血小板的激活会导致病理性血栓形成。激活的血小板释放各种细胞外囊泡 (EVs)。从质膜脱落的 EVs 常常暴露磷脂酰丝氨酸 (PS)。这些 EVs 具有促血栓形成作用，在许多心血管和代谢疾病中数量增加。激活的血小板从 PS 暴露 EVs 脱落的机制尚未得到很好的描述。富含胆固醇的脂筏为通过血小板中的受体和 Ca 通道协调信号提供了一个平台。我们表明，用甲基-β-环糊精或 Filipin 进行胆固醇耗竭可防止 Ca 触发的 PS 暴露 EVs 的释放。尽管钙蛋白酶活性是 PS 暴露释放所必需的，但胆固醇耗竭并不影响钙蛋白酶依赖性凝溶胶蛋白的切割。已报道 P2Y 和 TPα 分别是 ADP 和血栓素 A 的受体，存在于血小板脂筏中。然而，P2Y 拮抗剂 AR-C69931MX 或环氧化酶抑制剂阿司匹林对 A23187 诱导的 PS 暴露 EVs 的释放没有影响。综上所述，这些数据表明脂筏是血小板释放 PS 暴露 EVs 所必需的。
