Laboratory of Biomembrane, Tokyo Metropolitan Institute of Medical Science, Tokyo 156-8506, Japan.
Int J Mol Sci. 2020 Aug 2;21(15):5539. doi: 10.3390/ijms21155539.
Lipid rafts are dynamic assemblies of glycosphingolipids, sphingomyelin, cholesterol, and specific proteins which are stabilized into platforms involved in the regulation of vital cellular processes. The rafts at the cell surface play important functions in signal transduction. Recent reports have demonstrated that lipid rafts are spatially and compositionally heterogeneous in the single-cell membrane. In this review, we summarize our recent data on living platelets using two specific probes of raft components: lysenin as a probe of sphingomyelin-rich rafts and BCθ as a probe of cholesterol-rich rafts. Sphingomyelin-rich rafts that are spatially and functionally distinct from the cholesterol-rich rafts were found at spreading platelets. Fibrin is translocated to sphingomyelin-rich rafts and platelet sphingomyelin-rich rafts act as platforms where extracellular fibrin and intracellular actomyosin join to promote clot retraction. On the other hand, the collagen receptor glycoprotein VI is known to be translocated to cholesterol-rich rafts during platelet adhesion to collagen. Furthermore, the functional roles of platelet glycosphingolipids and platelet raft-binding proteins including G protein-coupled receptors, stomatin, prohibitin, flotillin, and HflK/C-domain protein family, tetraspanin family, and calcium channels are discussed.
脂质筏是糖脂、鞘磷脂、胆固醇和特定蛋白质的动态组装体，这些蛋白质稳定在参与调节重要细胞过程的平台中。细胞表面的筏在信号转导中发挥重要作用。最近的报告表明，单个细胞膜中的脂质筏在空间和组成上是不均匀的。在这篇综述中，我们总结了我们最近使用两种特定的筏成分探针（溶血素作为富含鞘磷脂的筏探针和 BCθ 作为富含胆固醇的筏探针）在活血小板上的数据。在扩展的血小板中发现了空间和功能上与富含胆固醇的筏不同的富含鞘磷脂的筏。纤维蛋白易位到富含鞘磷脂的筏上，血小板富含鞘磷脂的筏充当平台，使细胞外纤维蛋白和细胞内肌动球蛋白结合，促进血栓收缩。另一方面，已知胶原受体糖蛋白 VI 在血小板黏附到胶原时被易位到富含胆固醇的筏上。此外，还讨论了血小板糖脂和血小板筏结合蛋白（包括 G 蛋白偶联受体、stomatin、prohibitrin、flotillin 和 HflK/C 结构域蛋白家族、四跨膜蛋白家族和钙通道）的功能作用。
