Sphingosine 1-Phosphate Induces Platelet/Endothelial Cell Adhesion Molecule-1 Tyrosine Phosphorylation in Bovine Aortic Endothelial Cells through a PP2-Inhibitable Mechanism

Sphingosine 1-phosphate (S1P)是一種低分子?的多功能性水解磷酸脂，主要經由被活化的血小板釋放到血液中。S1P 和細胞表面特殊的G 型蛋白耦合受器結合後，會引發下游一??的細胞訊息傳遞及並影響細胞的基因表現與生?活動，包括：細胞增生、移?、傷口癒合，血管新生及免疫反應的過程。第一型血小板/內皮細胞附著因子(Platelet/endothelial cell adhesion molecule-1; PECAM-1)是一種大?表現在血小板及內皮細胞上的細胞黏著因子。其膜內結構上的?氨酸在磷酸化後會和具有SH2 結構之蛋白質結合並活化多種下游之細胞生?活動。在本實驗中，我們使用免疫沉澱與西方墨點法證明?S1P 的處?會引發牛主動脈內皮細胞上PECAM-1 ?氨酸的磷酸化以及後續SHP-2的結合。使用化學抑制劑所進?的前處?顯示?此PECAM-1 磷酸化的現象會被PP2 所抑制，顯示Src family kinases 在S1P 所引發的PECAM-1 ?氨酸磷酸化的過程中扮演?仲介者的角色。釐清此機制的細節將有助於未?在內皮細胞生?功能調控過程的研究。Sphingosine-1-phosphate (S1P) is a low-molecular-weight phospholipid derivative released by activated platelets. S1P transduces signals through a family of G protein-coupled receptors to modulate various physiological behaviors of endothelial cells. Platelet/endothelial cell adhesion molecule-1 (PECAM-1; CD31) is a 130-kDa protein expressed on the surfaces of leukocytes, platelets, and endothelial cells. Upon PECAM-1 activation, its cytoplasmic tyrosine residues become phosphorylated and bind with SH2 domain-containing proteins, thus leading to the downstream functions mediated by PECAM-1. In the present study, we found that S1P induced PECAM-1 tyrosine phosphorylation and SHP-2 association in bovine aortic endothelial cells (BAECs) by immunoprecipitation and western blotting. The pretreatment of BAECs with a series of chemical inhibitors to determine the signaling pathway showed that the PECAM-1 phosphorylation was inhibited by PP2, indicating the participation of Src family kinases. These results demonstrated that S1P induced PECAM-1 tyrosine phosphorylation in BAECs through mediation of Src family kinases, and this may regulate the physiological behaviors of endothelial cells