Mutations of a Drosophila NPC1 gene confer sterol and ecdysone metabolic defects
Mutations of a Drosophila NPC1 gene confer sterol and ecdysone metabolic defects
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DOI：
10.1534/genetics.105.046565
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发表时间：
2006-01-01
期刊：
影响因子：
3.3
通讯作者：
Pallanck, LJ
中科院分区：
文献类型：
--
作者：
Fluegel, ML;Parker, TJ;Pallanck, LJ
膳食胆固醇在细胞内运输的分子机制尚不清楚。先前的研究表明，NPC1蛋白家族在这一过程中起着重要作用，尽管该蛋白家族的确切功能尚不清楚。我们采用遗传方法进一步探索果蝇NPC1家族。果蝇基因组编码两个NPC1同源物，分别为NPC1a和NPC1b，与人类NPC1蛋白的同源性分别为42%和35%。这里我们描述了NPC1a基因突变分析的结果。NPC1a基因是普遍表达的，NPC1a的一个空等位基因赋予了早期幼虫的致命性。NPC1a突变体的隐性致死表型可以在高胆固醇饮食或含有昆虫类固醇激素20-羟基蜕皮激素的饮食中部分恢复。我们还发现，环腺中NPC1a的表达足以挽救与NPC1a缺失相关的致死率，并且NPC1a突变体幼虫的胆固醇水平相对于对照组没有变化。我们的研究结果表明，在许多果蝇组织中，NPC1a促进了有效的细胞内固醇运输，包括必须将固醇运送到蜕皮激素合成位点的环腺。
The molecular mechanisms by which dietary cholesterol is trafficked within cells are poorly understood. Previous work indicates that the NPC1 family of proteins plays an important role in this process, although the precise functions performed by this protein family remain elusive. We have taken a genetic approach to further explore the NPC1 family in the fruit fly Drosophila melanogaster. The Drosophila genome encodes two NPC1 homologs, designated NPC1a and NPC1b, that exhibit 42% and 35% identity to the human NPC1 protein, respectively. Here we describe the results of mutational analysis of the NPC1a gene. The NPC1a gene is ubiquitously expressed, and a null allele of NPC1a confers early larval lethality. The recessive lethal phenotype of NPC1a mutants can be partially rescued on a diet of high cholesterol or one that includes the insect steroid hormone 20-hydroxyecdysone. We also find that expression of NPC1a in the ring gland is sufficient to rescue the lethality associated with the loss of NPC1a and that cholesterol levels in NPC1a mutant larvae are unchanged relative to controls. Our results suggest that NPC1a promotes efficient intracellular trafficking of sterols in many Drosophila tissues including the ring gland where sterols must be delivered to sites of ecdysone synthesis.