Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, KY 40536-0509, USA.
Platelets. 2010;21(3):167-75. doi: 10.3109/09537101003611385.
Platelets contain an invaginated, tubular membranous structure called the surface-connected open canalicular system (SCCS or OCS), which is contiguous with the plasma membrane and serves as a site for granule fusion and as a reservoir of membrane for platelet spreading. According to ultrastructural studies, platelets from some species lack OCS. In an attempt to correlate biochemical and functional attributes with the presence of an OCS, platelets from human, mouse and dog (OCS(+)), and from cow, camel and horse (OCS(-)) were analysed for differential protein expression and aggregation in response to thrombin. Among the 18 different cytoskeletal and regulatory proteins examined, five (Rac1, RhoA, Ras, calmodulin and Src) were expressed at higher levels in OCS(+) platelets (p < 0.05). Given the role of Arf6 in the formation of tubular invaginations in nucleated cells, the levels of Arf6-GTP were analysed in OCS(+) and OCS(-) platelets. There was no significant correlation between the presence of OCS and total Arf6 or Arf6-GTP levels. Comparison of platelet aggregation between different species suggests that OCS(-) platelets have delayed responses. This comparison of platelets from six different species, which differ in their OCS, shows the differential expression of known signaling components and foreshadows future studies focusing on OCS formation and function.
血小板含有一个内陷的管状膜结构，称为表面连接的开放小管系统（SCCS 或 OCS），它与质膜连续，作为颗粒融合的部位和血小板扩展的膜储备库。根据超微结构研究，一些物种的血小板缺乏 OCS。为了将生化和功能特性与 OCS 的存在相关联，分析了来自人类、小鼠和狗（OCS(+)）以及来自牛、骆驼和马（OCS(-））的血小板的差异蛋白表达和对凝血酶的聚集反应。在检查的 18 种不同的细胞骨架和调节蛋白中，有 5 种（Rac1、RhoA、Ras、钙调蛋白和 Src）在 OCS(+)血小板中表达水平更高（p<0.05）。鉴于 Arf6 在有核细胞管状内陷形成中的作用，分析了 OCS(+)和 OCS(-)血小板中 Arf6-GTP 的水平。OCS 的存在与总 Arf6 或 Arf6-GTP 水平之间没有显著相关性。不同物种血小板聚集的比较表明，OCS(-)血小板的反应延迟。对六种不同 OCS 存在差异的血小板的比较表明，已知信号成分的差异表达预示着未来将重点关注 OCS 的形成和功能。
