From the INSERM, UMR_S 1176, Paris-Sud University, Université Paris-Saclay, Le Kremlin-Bicêtre, France (F.A., A.K., M.B., D.B., O.D.C.)
From the INSERM, UMR_S 1176, Paris-Sud University, Université Paris-Saclay, Le Kremlin-Bicêtre, France (F.A., A.K., M.B., D.B., O.D.C.).
Arterioscler Thromb Vasc Biol. 2018 May;38(5):1037-1051. doi: 10.1161/ATVBAHA.117.310373. Epub 2018 Mar 8.
Platelet secretion is crucial for many physiological platelet responses. Even though several regulators of the fusion machinery for secretory granule exocytosis have been identified in platelets, the underlying mechanisms are not yet fully characterized.
By studying a mouse model (cKO [conditional knockout]) lacking Kif5b (kinesin-1 heavy chain) in its megakaryocytes and platelets, we evidenced unstable hemostasis characterized by an increase of blood loss associated to a marked tendency to rebleed in a tail-clip assay and thrombus instability in an in vivo thrombosis model. This instability was confirmed in vitro in a whole-blood perfusion assay under blood flow conditions. Aggregations induced by thrombin and collagen were also impaired in cKO platelets. Furthermore, P-selectin exposure, PF4 (platelet factor 4) secretion, and ATP release after thrombin stimulation were impaired in cKO platelets, highlighting the role of kinesin-1 in α-granule and dense granule secretion. Importantly, exogenous ADP rescued normal thrombin induced-aggregation in cKO platelets, which indicates that impaired aggregation was because of defective release of ADP and dense granules. Last, we demonstrated that kinesin-1 interacts with the molecular machinery comprising the granule-associated Rab27 (Ras-related protein Rab-27) protein and the Slp4 (synaptotagmin-like protein 4/SYTL4) adaptor protein.
Our results indicate that a kinesin-1-dependent process plays a role for platelet function by acting into the mechanism underlying α-granule and dense granule secretion.
血小板分泌对于许多生理血小板反应至关重要。尽管已经在血小板中鉴定出几种用于分泌颗粒胞吐融合机制的调节剂，但潜在的机制尚未完全表征。
通过研究一种在巨核细胞和血小板中缺乏 Kif5b（驱动蛋白-1 重链）的小鼠模型（cKO [条件性敲除]），我们证明了不稳定的止血作用，其特征是失血增加与尾巴夹测定中明显的再出血倾向以及体内血栓形成模型中的血栓不稳定。这种不稳定性在血流条件下的全血灌注测定中在体外得到了证实。cKO 血小板中由凝血酶和胶原蛋白诱导的聚集也受损。此外，cKO 血小板中 P-选择素暴露、PF4（血小板因子 4）分泌和凝血酶刺激后的 ATP 释放受损，突出了驱动蛋白-1 在α-颗粒和致密颗粒分泌中的作用。重要的是，外源性 ADP 挽救了 cKO 血小板中正常凝血酶诱导的聚集，这表明聚集受损是由于 ADP 和致密颗粒释放缺陷所致。最后，我们证明了驱动蛋白-1与包含颗粒相关的 Rab27（Ras 相关蛋白 Rab-27）蛋白和 Slp4（突触融合蛋白样蛋白 4/SYTL4）衔接蛋白的分子机制相互作用。
我们的结果表明，驱动蛋白-1 依赖性过程通过作用于α-颗粒和致密颗粒分泌的机制在血小板功能中发挥作用。
