Signal transduction for apoptosis induction using apoptosis-inducing immunosuppressant

在我们之前的研究中，鞘鞘苷样免疫抑制剂ISP-1被发现通过抑制丝氨酸棕榈酰转移酶来抑制白细胞介素2依赖性细胞毒性T细胞系CTLL-2的增殖，丝氨酸棕榈酰转移酶催化鞘鞘脂生物合成的承诺步骤。鞘氨醇可拮抗ISP-1诱导的生长抑制作用。代替鞘氨醇，植物鞘氨醇在酿酒酵母中通过与哺乳动物细胞相似的途径合成。本研究中，在酿酒酵母中观察到ISP-1对增殖的抑制作用，并通过添加植物鞘氨醇来消除这种抑制作用。此外，流式细胞术检测到ISP-1处理的酵母细胞中DNA的过度复制。我们已经鉴定出一种酿酒酵母基因SLI2，它可以抵抗ISP-1的生长抑制。蛋白激酶催化结构域位于Sli2p的羧基末端。SLI2的激酶死亡突变体对ISP-1没有任何抗性，这使我们预测Sli2p的激酶活性对于其抵抗ISP-1的功能至关重要。Sli2p过表达对丝氨酸棕榈酰转移酶活性和鞘脂代谢无影响。这些结果表明Sli2p可能在拯救酵母免受ISP-1诱导的鞘脂减少中起重要作用。

In our previous study, the sphingosine-like immunosuppressant, ISP-1, was found to suppress proliferation of an interleukin-2-depentent cytotoxic T cell line, CTLL-2, through the inhibition of serine palmitoyltransferase, which catalyzes the committed step of sphingolipid biosynthesis. The growth inhibition induced by ISP-1 was antagonized by the addition of sphingosine. Instead of sphingosine, phytosphingsine is synthesized in the Saccharomyces cerevisiae by the similar pathway of mammalian cells, In this study, the inhibition of proliferation by ISP-1 was observed with Saccharomyces cerevisiae, and was abolished by addition of phytosphingsine. In addition, overreplication of DNA was detected in the ISP-1 treated yeast cells by flow cytometry. And we have identified a Saccharomyces cerevisiae gene, SLI2, that resisted the growth inhibition of ISP-1. The protein kinase catalytic domain is located at the carboxy-terminal portion of Sli2p. Kinase-dead mutants of SLI2 did not give any resistance to ISP-1, leading us to predict that kinase activity of Sli2p should be essential for its function in resisting ISP-1. Sli2p overexpression had no effect on serine palmitoyltransferase activity and sphingolipids metabolism. These results indicated that Sli2p may play an important role in rescuing yeast from decrease of sphingolipids induced by ISP-1.