Törnquist K, Saarinen P, Vainio M, Ahlström M
Department of Biosciences, University of Helsinki, Finland.
Endocrinology. 1997 Oct;138(10):4049-57. doi: 10.1210/endo.138.10.5422.
Sphingosine 1-phosphate (SPP) potently mobilizes sequestered calcium and is a mitogen in several cell types. In the present investigation, we have evaluated the effect of SPP on intracellular free calcium concentration ([Ca2+]i) and synthesis of DNA in thyroid FRTL-5 cells. SPP rapidly and transiently mobilized sequestered calcium and stimulated entry of extracellular calcium. The entry of calcium, but not the mobilization, was in part inhibited by pretreatment with pertussis toxin (Ptx), and by activation of protein kinase C. SPP did not stimulate the production of inositol 1,4,5-trisphosphate. SPP stimulated the incorporation of 3H-thymidine in a time- and dose-dependent manner. The effect was not inhibited by Ptx. Furthermore, SPP stimulated the activation of the proto-oncogene c-fos. SPP rapidly tyrosine-phosphorylated an approximately 66 kDa protein. This phosphorylation persisted for at least 1 h. Pretreatment of the cells with genistein abolished the SPP-evoked tyrosine phosphorylation, and attenuated the SPP-evoked increase in [Ca2+]i. Furthermore, the SPP-evoked activation of Na+-H+ exchange was inhibited by genistein. The phosphorylation was not attenuated by pretreatment of the cells with Ptx. SPP per se did not affect cellular cAMP levels but attenuated the TSH-evoked increase in cAMP. As the effect of SPP might be due to activation of phospholipase D, we tested whether phosphatidic acid (PA) mobilized calcium or stimulated the incorporation of 3H-thymidine. PA mobilized sequestered calcium but did not stimulate calcium entry. PA very modestly enhanced the incorporation of 3H-thymidine. Our results suggest, that SPP stimulates DNA synthesis and activates entry of calcium in FRTL-5 cells. The effect on calcium entry appears to be dependent, at least in part, on one or several tyrosine kinases.
鞘氨醇-1-磷酸（SPP）能有效动员储存的钙，并且在多种细胞类型中是一种促有丝分裂原。在本研究中，我们评估了SPP对甲状腺FRTL-5细胞内游离钙浓度（[Ca2+]i）和DNA合成的影响。SPP迅速且短暂地动员了储存的钙，并刺激细胞外钙的内流。钙的内流而非动员部分受到百日咳毒素（Ptx）预处理以及蛋白激酶C激活的抑制。SPP并未刺激肌醇1,4,5-三磷酸的产生。SPP以时间和剂量依赖的方式刺激3H-胸腺嘧啶核苷的掺入。该作用不受Ptx抑制。此外，SPP刺激原癌基因c-fos的激活。SPP迅速使一种约66 kDa的蛋白质发生酪氨酸磷酸化。这种磷酸化持续至少1小时。用染料木黄酮预处理细胞可消除SPP引起的酪氨酸磷酸化，并减弱SPP引起的[Ca2+]i升高。此外，染料木黄酮抑制了SPP引起的Na+-H+交换激活。用Ptx预处理细胞并未减弱这种磷酸化。SPP本身不影响细胞内cAMP水平，但减弱了促甲状腺激素（TSH）引起的cAMP升高。由于SPP的作用可能是由于磷脂酶D的激活，我们测试了磷脂酸（PA）是否能动员钙或刺激3H-胸腺嘧啶核苷的掺入。PA动员了储存的钙，但未刺激钙内流。PA非常适度地增强了3H-胸腺嘧啶核苷的掺入。我们的结果表明，SPP刺激FRTL-5细胞中的DNA合成并激活钙内流。对钙内流的影响似乎至少部分依赖于一种或几种酪氨酸激酶。
