VAMP-7 links granule exocytosis to actin reorganization during platelet activation
VAMP-7 links granule exocytosis to actin reorganization during platelet activation
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DOI：
10.1182/blood-2014-12-618744
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发表时间：
2015-07-30
期刊：
影响因子：
20.3
通讯作者：
Flaumenhaft, Robert
中科院分区：
文献类型：
--
作者：
Koseoglu, Secil;Peters, Christian G.;Flaumenhaft, Robert
血小板活化导致深刻的形态变化并伴随着颗粒内容物的释放。最近的证据表明，在激活过程中颗粒与质膜的融合提供了辅助膜来覆盖生长的肌动蛋白结构。然而，人们对膜融合如何与肌动蛋白重组相结合知之甚少。囊泡相关膜蛋白 (VAMP)-7 存在于血小板囊泡上，并具有 N 末端 longin 结构域，能够将胞吐作用与细胞骨架重塑联系起来。我们评估了 VAMP-7(-/-) 小鼠的血小板，以确定这种 VAMP 亚型是否有助于颗粒释放和血小板扩散。 VAMP-7(-/-) 血小板在致密颗粒胞吐作用和聚集受损方面表现出部分缺陷。在血栓形成过程中，VAMP-7(-/-) 血小板的α颗粒胞吐作用在体外和体内均减弱。与 VAMP-7 在细胞骨架重塑中的作用一致，与野生型对照相比，VAMP-7(-/-) 血小板在基质上的扩散减少。 VAMP-7 的免疫沉淀揭示了与 VPS9 结构域锚蛋白重复蛋白 (VARP) 的关联，VARP 是一种与膜结合蛋白和细胞骨架蛋白以及 Arp2/3 相互作用的接头蛋白。 VAMP-7、VARP 和 Arp2/3 在扩散过程中定位于血小板周边。这些研究表明，VAMP-7 参与血小板颗粒的分泌和扩散，并提出了 VAMP-7 将颗粒胞吐作用与肌动蛋白重组联系起来的机制。
Platelet activation results in profound morphologic changes accompanied by release of granule contents. Recent evidence indicates that fusion of granules with the plasma membrane during activation provides auxiliary membrane to cover growing actin structures. Yet little is known about how membrane fusion is coupled with actin reorganization. Vesicle-associated membrane protein (VAMP)-7 is found on platelet vesicles and possesses an N-terminal longin domain capable of linking exocytosis to cytoskeletal remodeling. We have evaluated platelets from VAMP-7(-/-) mice to determine whether this VAMP isoform contributes to granule release and platelet spreading. VAMP-7(-/-) platelets demonstrated a partial defect in dense granule exocytosis and impaired aggregation. alpha Granule exocytosis from VAMP-7(-/-) platelets was diminished both in vitro and in vivo during thrombus formation. Consistent with a role of VAMP-7 in cytoskeletal remodeling, spreading on matrices was decreased in VAMP-7(-/-) platelets compared to wild-type controls. Immunoprecipitation of VAMP-7 revealed an association with VPS9-domain ankyrin repeat protein (VARP), an adaptor protein that interacts with both membrane-bound and cytoskeleton proteins and with Arp2/3. VAMP-7, VARP, and Arp2/3 localized to the platelet periphery during spreading. These studies demonstrate that VAMP-7 participates in both platelet granule secretion and spreading and suggest a mechanism whereby VAMP-7 links granule exocytosis with actin reorganization.