Molecular dissection of the physiological role of bioactive sphingosine-1-phosphate and Edg receptors

为了描述鞘氨醇-1-磷酸（S1P）的生理和病理生理作用，我们进行了以下体外和体内研究。S1P及其受体正、负调节细胞运动。S1P受体Edg1和Edg3通过Gi介导Rac刺激从而趋化，而Edg5通过G12/13和Rho介导Rac抑制和细胞迁移抑制。现有证据表明，S1P可影响损伤血管的平滑肌蓄积。我们发现S1P刺激了新生内膜平滑肌中血小板衍生生长因子（PDGF） A链和B链的mRNA表达。这种刺激作用是通过Edg1-Gi-Ras-ERK/p38MAPK和Edg3/ edg5 - rho激酶介导的。ERK和p38MAPK介导KLF5表达的刺激，这是PDGF基因表达的必要和充分条件。S1P抑制血管平滑肌细胞的迁移。这一作用伴随着Rac抑制。有趣的是，G12/13和Gq都参与了s1p诱导的血管平滑肌细胞中Rac的抑制。除了Edg1和Edg3外，血管内皮细胞还表达Edg5， Edg5介导内皮细胞迁移和毛细血管样管形成的抑制。我们制备了转基因edg1和鞘氨醇激酶的小鼠，并分析了它们的表型。初步结果表明，S1P-Edg系统参与了心血管系统的内稳态。

In order to delineate physiological and pathophysiological roles of sphingosine-1-phosphate (S1P), we conducted the following in vitro and in vivo investigations. S1P and its receptors regulate cell motility both positively and negatively. The S1P receptors Edg1 and Edg3 mediate Rac stimulation and thereby chemotaxis via Gi, whereas Edg5 mediates Rac inhibition and cell migration inhibition via G12/13 and Rho. Available evidence suggests that S1P could affect vascular smooth muscle accumulation in injured blood vessels. We found that S1P stimulated mRNA expression of platelet-derived growth factor (PDGF) A and B chains in neointimal smooth muscle. This stimulatory effect was mediated via Edg1-Gi-Ras-ERK/p38MAPK and Edg3/Edg5-Rho-Rho kinase. The ERK and p38MAPK mediated stimulation of KLF5 expression, which was necessary and sufficient for PDGF gene expression. S1P inhibits migration of vascular smooth muscle cells. This action was accompanied by Rac inhibition. Interestingly, both G12/13 and Gq were involved in S1P-induced Rac inhibition in vascular smooth muscle cells. In addition to Edg1 and Edg3, vascular endothelial cells express Edg5, which mediates inhibition of endothelial cell migration and capillary like tube formation. We generated Edg1-transgenic and sphingosine kinase-transgenic mice, and analyzed their phenotypes. Preliminary results show that S1P-Edg system is involved in the homeostasis of the cardiovascular system.