DAF‐12‐dependent rescue of dauer formation in Caenorhabditis elegans by (25S)‐cholestenoic acid

• Published in: Aging cell Vol. 5; no. 4; pp. 283 - 291
• Main Authors: Held, Jason M., White, Mark P., Fisher, Alfred L., Gibson, Bradford W., Lithgow, Gordon J., Gill, Matthew S.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-08-2006
• Subjects: Animals; C. elegans; Caenorhabditis elegans - genetics; Caenorhabditis elegans - growth & development; Caenorhabditis elegans - metabolism; Caenorhabditis elegans Proteins - genetics; Caenorhabditis elegans Proteins - metabolism; Cell Line; Cholestenes - pharmacology; Cytochrome P-450 Enzyme System - genetics; Cytochrome P-450 Enzyme System - metabolism; DAF‐12; dauer; Dose-Response Relationship, Drug; Gene Expression Regulation, Developmental; Humans; Larva - metabolism; Larva - physiology; ligand; Ligands; lipid; Mutation; nuclear receptor; Phenotype; Receptors, Cytoplasmic and Nuclear - genetics; Receptors, Cytoplasmic and Nuclear - metabolism; Transfection
• ISSN: 1474-9718; 1474-9726
• DOI: 10.1111/j.1474-9726.2006.00218.x

Summary
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‐3β‐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 Δ5‐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.