PDF(Pubmed)
Abstract：
UNASSIGNED: Glycoprotein Ibα (GPIbα), the ligand-binding subunit of platelet GPIb-IX complex, interacts with von Willebrand factor (VWF) exposed at the injured vessel wall, initiating platelet adhesion, activation, hemostasis, and thrombus formation. The cytoplasmic tail of GPIbα interacts with 14-3-3ζ, regulating the VWF-GPIbα-elicited signal transduction and VWF binding function of GPIbα. However, we unexpectedly found that the GPIbα-14-3-3ζ association, beyond VWF-dependent function, is essential for general platelet activation. We found that the myristoylated peptide of GPIbα C-terminus MPαC, a potential GPIbα inhibitor, by itself induced platelet aggregation, integrin αIIbβ3 activation, granule secretion, and phosphatidylserine (PS) exposure. Conversely, the deletion of the cytoplasmic tail of GPIbα in mouse platelets (10aa-/-) decreased platelet aggregation, integrin αIIbβ3 activation, granule secretion, and PS exposure induced by various physiological agonists. Phosphoproteome-based kinase activity profiling revealed significantly upregulated protein kinase C (PKC) activity in MPαC-treated platelets. MPαC-induced platelet activation was abolished by the pan-PKC inhibitor and PKCα deletion. Decreased PKC activity was observed in both resting and agonist-stimulated 10aa-/- platelets. GPIbα regulates PKCα activity by sequestering 14-3-3ζ from PKCα. In vivo, the deletion of the GPIbα cytoplasmic tail impaired mouse hemostasis and thrombus formation and protected against platelet-dependent pulmonary thromboembolism. Therefore, our findings demonstrate an essential role for the GPIbα cytoplasmic tail in regulating platelet general activation and thrombus formation beyond the VWF-GPIbα axis.
摘要：
糖蛋白(GP)Ib,血小板GPIb-IX复合物的配体结合亚基，与暴露在损伤血管壁上的血管性血友病因子(VWF)相互作用，启动血小板粘附，激活,止血,和血栓形成。GPIb的细胞质尾与14-3-3相互作用，调节VWF-GPIb的信号转导和VWF结合功能。然而,我们意外地发现，GPIb-14-3-3协会，超越VWF依赖函数，对于一般的血小板活化至关重要。我们发现，GPIb_细胞质尾肽MP_C，潜在的GPIb抑制剂，自身诱导的血小板聚集，整合素αIIbβ3激活，颗粒分泌，和磷脂酰丝氨酸(PS)暴露。相反，小鼠血小板(10aa-/-)中GPIb的胞质尾缺失降低了血小板聚集,整合素IIb3激活，颗粒分泌，和由各种生理激动剂诱导的PS暴露。基于磷酸化蛋白质组的激酶活性分析显示，在MPC处理的血小板中，蛋白激酶C（PKC）活性显着上调。Pan-PKC抑制剂和PKC的缺失消除了MP-C诱导的血小板活化。在静息和激动剂刺激的10aa-/-血小板中均观察到降低的PKC活性。GPIb通过隔离PKC的14-3-3来调节PKC的活动。在体内,GPIb的缺失会损害小鼠的止血和血栓形成，并防止血小板依赖性肺血栓栓塞。因此,我们的研究结果证明了GPIb的细胞质尾在调节血小板的一般活化和血栓形成方面的重要作用，超出了VWF-GPIb的轴。
