Tani Motohiro, Kihara Akio, Igarashi Yasuyuki
Department of Biomembrane and Biofunctional Chemistry, Graduate School of Pharmaceutical Sciences, Hokkaido University, Kita 12-jo, Nishi 6-choume, Kita-ku, Sapporo 060-0812, Japan.
Biochem J. 2006 Feb 15;394(Pt 1):237-42. doi: 10.1042/BJ20051354.
In the yeast Saccharomyces cerevisiae, sphingolipids are essential for cell growth. Inactivation of sphingolipid biosynthesis, such as by disrupting the serine palmitoyltransferase gene (LCB2), is lethal, but cells can be rescued by supplying an exogenous LCB (long-chain base) like PHS (phytosphingosine) or DHS (dihydrosphingosine). In the present study, supplying SPH (sphingosine), an unnatural LCB for yeast, similarly rescued the Deltalcb2 cells, but only when SPH 1-phosphate production was inhibited by deleting the LCB kinase gene LCB4. Exogenously added SPH was adequately converted into phosphoinositol-containing complex sphingolipids. Interestingly, cells carrying SPH-based sphingolipids exhibited a defect in the association of Pma1p with Triton X-100-insoluble membrane fractions, and displayed sensitivities to both Ca2+ and hygromycin B. These results suggest that the SPH-based sphingolipids in these cells have properties that differ from those of the PHS- or DHS-based sphingolipids in regard to lipid microdomain formation, leading to abnormal sensitivities towards certain environmental stresses. The present paper is the first report showing that in sphingolipid-deficient S. cerevisiae, the requirement for LCB can be fulfilled by exogenous SPH, although this supplement results in failure of lipid microdomain formation.
在酿酒酵母中，鞘脂对于细胞生长至关重要。鞘脂生物合成的失活，例如通过破坏丝氨酸棕榈酰转移酶基因（LCB2），是致死性的，但通过提供外源性长链碱基（LCB）如植物鞘氨醇（PHS）或二氢鞘氨醇（DHS），细胞可以得到挽救。在本研究中，提供酵母的非天然LCB鞘氨醇（SPH）同样挽救了Deltalcb2细胞，但只有当通过缺失LCB激酶基因LCB4抑制SPH 1-磷酸的产生时才有效。外源添加的SPH被充分转化为含磷酸肌醇的复合鞘脂。有趣的是，携带基于SPH的鞘脂的细胞在Pma1p与Triton X-100不溶性膜组分的结合方面表现出缺陷，并对Ca2+和潮霉素B均敏感。这些结果表明，这些细胞中基于SPH的鞘脂在脂质微区形成方面具有与基于PHS或DHS的鞘脂不同的特性，导致对某些环境应激的异常敏感性。本文是首次报道表明，在鞘脂缺陷的酿酒酵母中，外源性SPH可以满足对LCB的需求，尽管这种补充导致脂质微区形成失败。
