Investigation on physiological roles of sphingosine-1-phosphate signaling system using genetically engineered mice.

我们已经鉴定了鞘氨醇-1-磷酸(S1P)受体亚型S1P_2是第一个负调节细胞流动性的G蛋白偶联受体。在本研究中，我们证实了在小鼠黑色素瘤B16-F10细胞中内源性表达S1P_2确实在体外系统中介导了抑制细胞的迁移和侵袭。此外，我们还在尾静脉注射模型中发现，S1P通过内源性表达S1P_2，有效地抑制了B16细胞的肺转移。这些结果提出了一个有趣的可能性，即S1P_2选择性激动剂可能作为一种肿瘤细胞侵袭和转移的抑制因子。与S1P_2形成鲜明对比的是，我们和其他人证明了S1P_1和S1P_3介导S1IP刺激细胞迁移，从而发挥趋化受体的作用。事实上，后一种受体亚型在B16黑色素瘤细胞中的过表达导致了体外迁移和侵袭的刺激，以及对S1P治疗的体内肺转移的加剧。此外，我们最近还发现，S1P_1通过转录因子KLF5的作用，介导S1P刺激培养的血管平滑肌细胞中血小板衍生生长因子上调。这一结果可能与S1P_1在动脉粥样硬化发生发展中的病理生理作用有关。为了阐明S1P信号系统在体内的生理作用，我们建立了S1P_2基因敲除小鼠和鞘氨醇激酶转基因小鼠。对这些转基因小鼠的调查目前正在进行中。

We have identified sphingosine-1-phosphate(S1P) receptor isoform S1P_2 as the first G protein-coupled receptor that negatively regulates cell mobility. In the present study we demonstrated that endogenously expressed S1P_2 in mouse melanoma B16-F10 cells indeed mediated inhibition of cell migration and invasion in in vitro system. In addition, we found that pretreatment of B16 cells with S1P potently inhibited pulmonary metastasis in vivo in tail vein injection model, via endogenously expressed S1P_2. These results raises an intriguing possibility that S1P_2-selective agonist could serve as an inhibitor of tumor cell invasion and metastasis in a subset of human malignancies. In sharp contrast to S1P_2, we and others have demonstrated that S1P_1 and S1lP_3 mediates S1IP stimulation of cell migration, thereby acting as chemotactic receptors. Indeed, overexpression of either of the latter receptor isoforms in B16 melanoma cells resulted in stimulation of migration and invasion in vitro, and aggravation of lung metastasis in vivo in response to S1P treatment. In addition, we have recently found that S1P_1 mediated S1P stimulation of platelet-derived growth factor upregulation in cultured vascular smooth muscle rails, through die action of a transcription factor KLF5. The results may implicate pathophysiological role for S1P_1 in development of atherosclerosis. In an attempt to elucidate physiological role of S1P signaling system in vivo, we have created S1P_2 knockout mice and sphingosine kinase transgenic mice. Investigation on these genetically engineered mice is now underway.