Synthesis of mannose-(inositol-P)(2)-ceramide, the major sphingolipid in Saccharomyces cerevisiae, requires the IPT1 (YDR072c) gene
Synthesis of mannose-(inositol-P)(2)-ceramide, the major sphingolipid in Saccharomyces cerevisiae, requires the IPT1 (YDR072c) gene
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DOI：
10.1074/jbc.272.47.29620
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发表时间：
1997-11-21
影响因子：
4.8
通讯作者：
Lester, RL
中科院分区：
文献类型：
--
作者：
Dickson, RC;Nagiec, EE;Lester, RL
对酿酒酵母鞘脂合成所必需的基因和蛋白质的了解还很不完全，这些信息将促进对途径调节和鞘脂功能的研究。利用最近鉴定的合成鞘脂肌醇-β-神经酰胺（IPC）所必需的Aur 1蛋白序列，我们证明了一个同源物，（开放阅读框YDR 072 c），称为肌醇磷酸转移酶1（Ipt 1），是合成甘露糖-（肌醇-P）（2）-神经酰胺（M（IP）（2）C）所必需的，甘露糖-（肌醇-P）（2）-神经酰胺是S中最丰富和复杂的鞘脂。该结论基于对ipt 1缺失菌株的分析，该菌株不能积累M（IP）（2）C，而是积累增加量的前体甘露糖肌醇-β-神经酰胺。该突变体也不能将放射性前体掺入M（IP）（2）C中，并且由其制备的膜不能将[H-3-肌醇]磷脂酰肌醇掺入M（IP）（2）C中，表明缺乏M（IP）（2）C合酶活性（嘌呤磷脂酰肌醇：甘露糖-肌醇-P-神经酰胺磷酸肌醇转移酶）。M（IP）（2）C合酶活性在微摩尔范围内被金芽孢杆菌素A抑制，但药物敏感性比报道的IPC合酶活性低1000倍以上。ipt 1缺失突变体没有严重的表型效应，但对钙离子的生长抑制的抗性略高。对ipt 1基因的鉴定有助于确定M（IP）（2）C鞘脂的功能以及确定TPC和M（IP）（2）C鞘脂酶的催化机制。
Knowledge of the Saccharomyces cerevisiae genes and proteins necessary for sphingolipid biosynthesis is far from complete, Such information should expedite studies of pathway regulation and sphingolipid functions, Using the Aur1 protein sequence, recently identified as necessary for synthesis of the sphingolipid inositol-P-ceramide (IPC), we show that a homolog (open reading frame YDR072c), termed Ipt1 (inositolphosphotransferase 1) is necessary for synthesis of mannose-(inositol-P)(2)-ceramide (M(IP)(2)C), the most abundant and complex sphingolipid in S. cerevisiae, This conclusion is based upon analysis of an ipt1-deletion strain, which fails to accumulate M(IP)(2)C and instead accumulates increased amounts of the precursor mannose inositol-P-ceramide. The mutant also fails to incorporate radioactive precursors into M(IP)(2)C, and membranes prepared from it do not incorporate [H-3-inositol]phosphatidylinositol into M(IP)(2)C, indicating a lack of M(IP)(2)C synthase activity (putatively phosphatidylinositol:mannose-inositol-P-ceramide phosphoinositol transferase), M(IP)(2)C synthase activity is inhibited in the micromolar range by aureobasidin A, but drug sensitivity is over 1000-fold lower than reported for IPC synthase activity. An ipt1-deletion mutant has no severe phenotypic effects but is slightly more resistant to growth inhibition by calcium ions, Identification of the IPT1 gene should be helpful in determining the function of the M(IP)(2)C sphingolipid and in determining the catalytic mechanism of TPC and M(IP)(2)C synthases.