Bergmeier Wolfgang, Piffath Crystal L, Cheng Guiying, Dole Vandana S, Zhang Yuhua, von Andrian Ulrich H, Wagner Denisa D
CBR Institute for Biomedical Research, Harvard Medical School, Boston, Mass 02115-6399, USA.
Circ Res. 2004 Oct 1;95(7):677-83. doi: 10.1161/01.RES.0000143899.73453.11. Epub 2004 Sep 2.
Interaction of the platelet receptor glycoprotein (GP) Ib-V-IX with von Willebrand factor exposed at a site of vascular injury is an essential step in the initiation of a hemostatic plug. Proteolytic cleavage (shedding) of the GPIbalpha subunit was first described >25 years ago, the protease mediating this event as well as its physiological function, however, have not been elucidated. We reported recently that shedding of GPIbalpha induced by platelet storage or mitochondrial injury involves a platelet-derived metalloproteinase(s). Here we show that GPIbalpha shedding in response to mitochondrial injury or physiological activation is inhibited in platelets obtained from chimeric mice, which express inactive tumor necrosis factor-alpha converting enzyme (TACE(DeltaZn/DeltaZn)) in blood cells only. Shedding was also inhibited in mouse and human platelets in the presence of 2 potent TACE inhibitors: TAP1 and TMI-1. Our data further suggest that TACE is important in the regulation of GPIbalpha expression in vivo because we observed an approximately 90% reduction in soluble GPIbalpha (glycocalicin) in plasma of TACE(DeltaZn/DeltaZn) chimeras as well as significantly increased levels of GPIbalpha on circulating platelets. In contrast, shedding of P-selectin from activated platelets was not affected by the mutation in TACE. Damaged TACE(DeltaZn/DeltaZn) platelets were further characterized by a markedly improved post-transfusion recovery and hemostatic function in mice. In conclusion, our data demonstrate that TACE is expressed in platelets and that it is the key enzyme mediating shedding of GPIbalpha.
血小板受体糖蛋白（GP）Ib-V-IX与血管损伤部位暴露的血管性血友病因子相互作用是启动止血栓形成的关键步骤。25多年前首次描述了GPIbalpha亚基的蛋白水解切割（脱落），然而，介导这一过程的蛋白酶及其生理功能尚未阐明。我们最近报道，血小板储存或线粒体损伤诱导的GPIbalpha脱落涉及一种血小板衍生的金属蛋白酶。在此我们表明，仅在血细胞中表达无活性肿瘤坏死因子-α转化酶（TACE(DeltaZn/DeltaZn)）的嵌合小鼠的血小板中，对线粒体损伤或生理激活的反应中GPIbalpha脱落受到抑制。在存在两种有效的TACE抑制剂TAP1和TMI-1的情况下，小鼠和人类血小板中的脱落也受到抑制。我们的数据进一步表明，TACE在体内GPIbalpha表达的调节中很重要，因为我们观察到TACE(DeltaZn/DeltaZn)嵌合体血浆中可溶性GPIbalpha（糖萼素）降低了约90%，同时循环血小板上GPIbalpha水平显著升高。相比之下，活化血小板中P-选择素的脱落不受TACE突变的影响。受损的TACE(DeltaZn/DeltaZn)血小板在小鼠体内的输血后恢复和止血功能明显改善。总之，我们的数据表明TACE在血小板中表达，并且它是介导GPIbalpha脱落的关键酶。
