Cell Biology Group and Pharmaceutical Analysis and Metabolomics Research Group, Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, UK.
Cell Signal. 2013 Apr;25(4):1011-7. doi: 10.1016/j.cellsig.2013.01.002. Epub 2013 Jan 11.
Two isoforms of sphingosine kinase, SK1 and SK2, catalyze the formation of the bioactive lipid sphingosine 1-phosphate (S1P) in mammalian cells. We have previously shown that treatment of androgen-sensitive LNCaP prostate cancer cells with a non-selective SK isoform inhibitor, 2-(p-hydroxyanilino)-4-(p-chlorophenyl)thiazole (SKi), induces the proteasomal degradation of SK1. This is concomitant with a significant increase in C22:0-ceramide and sphingosine levels and a reduction in S1P levels, resulting in the apoptosis of LNCaP cells. In contrast, we show here that a SK2-selective inhibitor, (R)-FTY720 methyl ether (ROME), increases sphingosine and decreases S1P levels but has no effect on ceramide levels and does not induce apoptosis in LNCaP cells. We also show that several glycolytic metabolites and (R)-S-lactoylglutathione are increased upon treatment of LNCaP cells with SKi, which induces the proteasomal degradation of c-Myc. These changes reflect an indirect antagonism of the Warburg effect. LNCaP cells also respond to SKi by diverting glucose 6-phosphate into the pentose phosphate pathway to provide NADPH, which serves as an antioxidant to counter an oxidative stress response. SKi also promotes the formation of a novel pro-apoptotic molecule called diadenosine 5',5'''-P(1),P(3)-triphosphate (Ap3A), which binds to the tumor suppressor fragile histidine triad protein (FHIT). In contrast, the SK2-selective inhibitor, ROME, induces a reduction in some glycolytic metabolites and does not affect oxidative stress. We conclude that SK1 functions to increase the stability of c-Myc and suppresses Ap3A formation, which might maintain the Warburg effect and cell survival, while SK2 exhibits a non-overlapping function.
两种亚型的鞘氨醇激酶（SK1 和 SK2）在哺乳动物细胞中催化生物活性脂质鞘氨醇 1-磷酸（S1P）的形成。我们之前已经表明，用非选择性 SK 同工型抑制剂 2-（对羟基苯胺基）-4-（对氯苯基）噻唑（SKi）处理雄激素敏感的 LNCaP 前列腺癌细胞会诱导 SK1 的蛋白酶体降解。这伴随着 C22:0-神经酰胺和鞘氨醇水平的显著增加以及 S1P 水平的降低，导致 LNCaP 细胞凋亡。相比之下，我们在这里表明，SK2 选择性抑制剂（R）-FTY720 甲基醚（ROME）会增加鞘氨醇并降低 S1P 水平，但对神经酰胺水平没有影响，也不会诱导 LNCaP 细胞凋亡。我们还表明，在用 SKi 处理 LNCaP 细胞时，几种糖酵解代谢物和（R）-S-乳酰谷胱甘肽会增加，这会诱导 c-Myc 的蛋白酶体降解。这些变化反映了对沃伯格效应的间接拮抗作用。LNCaP 细胞也会对 SKi 做出反应，将葡萄糖 6-磷酸分流到戊糖磷酸途径以提供 NADPH，作为抗氧化剂来对抗氧化应激反应。SKi 还促进了一种称为二腺苷 5'，5'''-P（1），P（3）-三磷酸（Ap3A）的新型促凋亡分子的形成，该分子与肿瘤抑制因子脆性组氨酸三联体蛋白（FHIT）结合。相比之下，SK2 选择性抑制剂 ROME 会降低一些糖酵解代谢物的水平，而不会影响氧化应激。我们得出的结论是，SK1 发挥作用以增加 c-Myc 的稳定性并抑制 Ap3A 的形成，这可能维持沃伯格效应和细胞存活，而 SK2 则表现出非重叠的功能。
