Gómez-Muñoz A, Waggoner D W, O'Brien L, Brindley D N
Department of Biochemistry, University of Alberta, Edmonton, Canada.
J Biol Chem. 1995 Nov 3;270(44):26318-25. doi: 10.1074/jbc.270.44.26318.
C2- and C6-ceramides (N-acetylsphingosine and N-hexanoylsphingosine, respectively) abolished the stimulation of DNA synthesis by sphingosine 1-phosphate in rat fibroblasts. This inhibition by ceramide was partially prevented by insulin. C2-ceramide did not alter the stimulation of DNA synthesis by insulin and decreased the sphingosine-induced stimulation by only 16%. The ceramides did not significantly modify the actions of sphingosine or sphingosine 1-phosphate in decreasing cAMP concentrations. C2- and C6-ceramides blocked the activation of phospholipase D by sphingosine 1-phosphate, and this inhibition was not affected by insulin. Okadaic acid decreased the activation of phospholipase D by sphingosine 1-phosphate and did not reverse the inhibitory effect of C2-ceramide on this activation. Therefore, this effect of C2-ceramide is unlikely to involve the stimulation of phosphoprotein phosphatase activity. Sphingosine did not activate phospholipase D activity significantly after 10 min. C2-ceramide stimulated the conversion of exogenous [3H]sphingosine 1-phosphate to sphingosine and ceramide in fibroblasts. Ceramides can inhibit some effects of sphingosine 1-phosphate by stimulating its degradation via a phosphohydrolase that also hydrolyzes phosphatidate. Furthermore, C2- and C6-ceramides stimulated ceramide production from endogenous lipids, and this could propagate the intracellular signal. This work demonstrates that controlling the production of ceramide versus sphingosine and sphingosine 1-phosphate after sphingomyelinase activation could have profound effects on signal transduction.
C2-神经酰胺和C6-神经酰胺（分别为N-乙酰鞘氨醇和N-己酰鞘氨醇）可消除1-磷酸鞘氨醇对大鼠成纤维细胞DNA合成的刺激作用。胰岛素可部分阻止神经酰胺的这种抑制作用。C2-神经酰胺不会改变胰岛素对DNA合成的刺激作用，且仅使鞘氨醇诱导的刺激作用降低16%。神经酰胺不会显著改变鞘氨醇或1-磷酸鞘氨醇在降低环磷酸腺苷（cAMP）浓度方面的作用。C2-神经酰胺和C6-神经酰胺可阻断1-磷酸鞘氨醇对磷脂酶D的激活作用，且这种抑制作用不受胰岛素影响。冈田酸可降低1-磷酸鞘氨醇对磷脂酶D的激活作用，但不会逆转C2-神经酰胺对该激活作用的抑制效果。因此，C2-神经酰胺的这种作用不太可能涉及磷蛋白磷酸酶活性的刺激。10分钟后，鞘氨醇不会显著激活磷脂酶D活性。C2-神经酰胺可刺激成纤维细胞中外源性[3H]1-磷酸鞘氨醇转化为鞘氨醇和神经酰胺。神经酰胺可通过刺激其经一种也能水解磷脂酸的磷酸水解酶降解来抑制1-磷酸鞘氨醇的某些作用。此外，C2-神经酰胺和C6-神经酰胺可刺激内源性脂质生成神经酰胺，这可能会传播细胞内信号。这项研究表明，在鞘磷脂酶激活后控制神经酰胺与鞘氨醇及1-磷酸鞘氨醇的生成可能会对信号转导产生深远影响。
