Glycoprotein VI is associated with GPIb-IX-V on the membrane of resting and activated platelets
Glycoprotein VI is associated with GPIb-IX-V on the membrane of resting and activated platelets
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DOI：
10.1160/th04-09-0584
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发表时间：
2005-04-01
影响因子：
6.7
通讯作者：
Berndt, MC
中科院分区：
文献类型：
--
作者：
Arthur, JF;Gardiner, EE;Berndt, MC
血小板胶原受体糖蛋白（GP）VI在低剪切应力下启动血小板聚集，而结合血管性血液病因子的GPlb-IX-V在高剪切条件下引发血小板聚集。为了研究GPlbIX-V和GPVI在血小板表面关联的可能性，我们首先确定了GPVI特异性激动剂、胶原相关肽（如胶原）诱导的聚集被GPlb α特异性单克隆抗体SZ2明显交叉阻断。从未刺激血小板的1% (v/v) triton可溶性部分用抗gplb α免疫沉淀GPlb-IX和抗GPVI免疫印迹显示GPIb-IX和GPVI之间存在关联。当血小板被凝血酶激活时，这种关联得以维持。在这些条件下，用甲基- β -环糊精预处理血小板以破坏脂筏并不影响静息血小板的关联。这种关联也独立于细胞骨架附着，因为它不受n-乙基马来酰亚胺或DNasel的影响，它们分别将GPIb-IX与丝蛋白和含有肌动蛋白的细胞骨架分离。最后，这种关联涉及GPlb α和GPVI的外结构域之间的相互作用，因为在GPVI脱落的条件下，GPlba（糖钙蛋白）和GPVI的可溶性片段从血小板上清中共同沉淀。因此，GPIb-IX-V对gpvi诱导的血小板反应的贡献，以及反之亦然，值得进一步研究。
The platelet collagen receptor, glycoprotein (GP)VI, initiates platelet aggregation at low shear stress while GPlb-IX-V, which binds von Willebrand factor, elicits platelet aggregation under high shear conditions. To investigate the possibility that GPlbIX-V and GPVI are associated on the platelet surface, we first ascertained that aggregation induced by a GPVI-specific agonist, collagen-related peptide, like collagen, is markedly cross-blocked by a GPlb alpha-specific monoclonal antibody, SZ2. Immunoprecipitation of GPlb-IX with anti-GPlb alpha from the 1% (v/v) Triton-soluble fraction of unstimulated platelets and immunoblotting with anti-GPVI demonstrated association between GPIb-IX and GPVI. This association was maintained when platelets were activated by thrombin. Pre-treatment of platelets with methyl-beta-cyclodextrin to disrupt lipid rafts did not affect association in resting platelets under these conditions of detergent lysis.The association is also independent of cytoskeletal attachment, since it was unaffected by treatment with N-ethylmaleimide or DNasel,which dissociate GPIb-IX from filamin and the actin-containing cytoskeleton, respectively. Finally, the association involves an interaction between the ectodomains of GPlb alpha and GPVI, since soluble fragments of GPlba (glycocalicin) and GPVI are co-precipitated from the platelet supernatant under conditions where GPVI is shed. A contribution of GPIb-IX-V to GPVI-induced platelet responses, and vice versa, therefore warrants further investigation.