Mandala S M, Thornton R, Tu Z, Kurtz M B, Nickels J, Broach J, Menzeleev R, Spiegel S
Department of Biochemistry, Merck Research Laboratories, Rahway, NJ 07065, USA.
Proc Natl Acad Sci U S A. 1998 Jan 6;95(1):150-5. doi: 10.1073/pnas.95.1.150.
The sphingolipid metabolites ceramide and sphingosine-1-phosphate are second messengers with opposing roles in mammalian cell growth arrest and survival; their relative cellular level has been proposed to be a rheostat that determines the fate of cells. This report demonstrates that this rheostat is an evolutionarily conserved stress-regulatory mechanism that influences growth and survival of yeast. Although the role of sphingosine-1-phosphate in yeast was not previously examined, accumulation of ceramide has been shown to induce G1 arrest and cell death. We now have identified a gene in Saccharomyces cerevisiae, LBP1, that regulates the levels of phosphorylated sphingoid bases and ceramide. LBP1 was cloned from a yeast mutant that accumulated phosphorylated long-chain sphingoid bases and diverted sphingoid base intermediates from sphingolipid pathways to glycerophospholipid biosynthesis. LBP1 and its homolog, LBP2, encode very hydrophobic proteins that contain a novel-conserved sequence motif for lipid phosphatases, and both have long-chain sphingoid base phosphate phosphatase activity. In vitro characterization of Lbp1p shows that this phosphatase is Mg2+-independent with high specificity for phosphorylated long-chain bases, phytosphingosine and sphingosine. The deletion of LBP1 results in the accumulation of phosphorylated long-chain sphingoid bases and reduced ceramide levels. Moreover, deletion of LBP1 and LBP2 results in dramatically enhanced survival upon severe heat shock. Thus, these phosphatases play a previously unappreciated role in regulating ceramide and phosphorylated sphingoid base levels in yeast, and they modulate stress responses through sphingolipid metabolites in a manner that is reminiscent of their effects on mammalian cells.
鞘脂代谢产物神经酰胺和1 -磷酸鞘氨醇是在哺乳动物细胞生长停滞和存活中发挥相反作用的第二信使；它们在细胞内的相对水平被认为是决定细胞命运的一种变阻器。本报告表明，这种变阻器是一种进化上保守的应激调节机制，影响酵母的生长和存活。尽管此前未研究过1 -磷酸鞘氨醇在酵母中的作用，但神经酰胺的积累已被证明可诱导G1期停滞和细胞死亡。我们现已在酿酒酵母中鉴定出一个基因LBP1，它可调节磷酸化鞘氨醇碱和神经酰胺的水平。LBP1是从一个积累磷酸化长链鞘氨醇碱并将鞘氨醇碱中间体从鞘脂途径转移至甘油磷脂生物合成的酵母突变体中克隆得到的。LBP1及其同源物LBP2编码非常疏水的蛋白质，这些蛋白质含有一种新型的脂质磷酸酶保守序列基序，并且两者都具有长链鞘氨醇碱磷酸磷酸酶活性。对Lbp1p的体外特性分析表明，这种磷酸酶不依赖Mg2 +，对磷酸化长链碱基、植物鞘氨醇和鞘氨醇具有高度特异性。LBP1的缺失导致磷酸化长链鞘氨醇碱的积累和神经酰胺水平的降低。此外，LBP1和LBP2的缺失导致在严重热休克后存活率显著提高。因此，这些磷酸酶在调节酵母中神经酰胺和磷酸化鞘氨醇碱水平方面发挥了以前未被认识到的作用，并且它们通过鞘脂代谢产物调节应激反应，其方式类似于它们对哺乳动物细胞的影响。
