Physical proximity and functional association of glycoprotein 1bα and protein-disulfide isomerase on the platelet plasma membrane
Physical proximity and functional association of glycoprotein 1bα and protein-disulfide isomerase on the platelet plasma membrane
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DOI：
10.1074/jbc.275.13.9758
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发表时间：
2000-03-31
影响因子：
4.8
通讯作者：
Hogg, PJ
中科院分区：
文献类型：
--
作者：
Burgess, JK;Hotchkiss, KA;Hogg, PJ
血小板功能受血小板巯基-二硫键平衡的影响。血小板活化导致表面蛋白巯基增加440%。在活化血小板表面上呈现游离巯基的两种蛋白质是蛋白质二硫键异构酶（PDI）和糖蛋白1b α（GP 1b α），PDI含有两个活性位点二硫醇/二硫化物。静息血小板上26%的PDI的活性位点是二硫醇形式，而活化血小板上的二硫醇形式为81%。类似地，GP 1b α在活化的血小板表面上呈现一个或多个游离巯基，但在静息血小板上不呈现。抗PDI抗体使vWF与血小板结合的解离常数增加了约50%，并且PDI和GP 1b α在血小板表面上足够接近，以允许与PDI和GP 1b α连接的发色团之间的荧光共振能量转移。用抗PDI抗体孵育静息血小板，然后用凝血酶活化，增强了单克隆抗体与活化血小板表面GP 1b α N-末端区域的标记和结合。这些观察结果表明，血小板活化引发了PDI活性位点二硫化物的还原和GP 1b α的构象变化，导致游离巯基暴露。
Platelet function is influenced by the platelet thiol-disulfide balance. Platelet activation resulted in 440% increase in surface protein thiol groups. Two proteins that presented free thiol(s) on the activated platelet surface were protein-disulfide isomerase (PDI) and glycoprotein 1b alpha (GP1b alpha), PDI contains two active site dithiols/disulfides. The active sites of 26% of the PDI on resting platelets was in the dithiol form, compared with 81% in the dithiol form on activated platelets. Similarly, GP1b alpha presented one or more free thiols on the activated platelet surface but not on resting platelets. Anti-PDI antibodies increased the dissociation constant for binding of vWF to platelets by similar to 50% and PDI and GP1b alpha were sufficiently close on the platelet surface to allow fluorescence resonance energy transfer between chromophores attached to PDI and GP1b alpha. Incubation of resting platelets with anti-PDI antibodies followed by activation with thrombin enhanced labeling and binding of monoclonal antibodies to the N-terminal region of GP1b alpha on the activated platelet surface. These observations indicated that platelet activation triggered reduction of the active site disulfides of PDI and a conformational change in GP1b alpha that resulted in exposure of a free thiol(s).