Held Jason M, White Mark P, Fisher Alfred L, Gibson Bradford W, Lithgow Gordon J, Gill Matthew S
Buck Institute for Age Research, 8001 Redwood Boulevard, Novato, CA 94945, USA.
Aging Cell. 2006 Aug;5(4):283-91. doi: 10.1111/j.1474-9726.2006.00218.x.
Population density, temperature and food availability all regulate the formation of the Caenorhabditis elegans dauer larva by modulating endocrine signaling pathways. The orphan nuclear receptor DAF-12 is pivotal for the decision to form a dauer or to undergo normal reproductive development. The DAF-12 ligand has been predicted to be a sterol that is metabolized by DAF-9, a cytochrome P450. Here we chemically characterize purified lipophilic nematode extracts and show that the ligand for DAF-12 contains a carboxyl moiety and is likely to be derived from a sterol. Using a candidate ligand approach we find that the C27 bile acid cholestenoic acid (5-cholesten-3beta-ol-(25S)-carboxylic acid) promotes reproductive growth in dauer-constitutive mutants in a daf-9- and daf-12-dependent manner. Furthermore, we find that cholestenoic acid can act as a DAF-12 ligand by activating DAF-12 in a cell-based transcription assay. Analysis of dauer-rescuing lipophilic extracts from nematodes by gas chromatography-mass spectrometry indicates the presence of several regioisomers of cholestenoic acid that are distinct from Delta(5)-cholestenoic acid and are not present in extracts from daf-9 mutants. These data suggest that carboxylated sterols may be key determinants of life history.
种群密度、温度和食物可利用性均通过调节内分泌信号通路来调控秀丽隐杆线虫 dauer 幼虫的形成。孤儿核受体 DAF-12 对于决定形成 dauer 幼虫还是进行正常生殖发育起着关键作用。DAF-12 的配体被预测为一种由细胞色素 P450 DAF-9 代谢的固醇。在此，我们对纯化的亲脂性线虫提取物进行化学表征，并表明 DAF-12 的配体含有羧基部分，且可能源自一种固醇。使用候选配体方法，我们发现 C27 胆汁酸胆甾烯酸（5-胆甾烯-3β-醇-(25S)-羧酸）以依赖 daf-9 和 daf-12 的方式促进 dauer 组成型突变体中的生殖生长。此外，我们发现胆甾烯酸可通过在基于细胞的转录测定中激活 DAF-12 来充当 DAF-12 的配体。通过气相色谱-质谱法分析线虫的 dauer 拯救亲脂性提取物表明存在几种胆甾烯酸的区域异构体，它们与 Δ(5)-胆甾烯酸不同，且不存在于 daf-9 突变体的提取物中。这些数据表明羧化固醇可能是生活史的关键决定因素。
