title: Functional divergence of dafachronic acid pathways in the control of C. elegans development and lifespan.
abstract: Steroid hormone and insulin/insulin-like growth factor signaling (IIS) pathways control development and lifespan in the nematode Caenorhabditis elegans by regulating the activity of the nuclear receptor DAF-12 and the FoxO transcription factor DAF-16, respectively. The DAF-12 ligands Delta(4)- and Delta(7)-dafachronic acid (DA) promote bypass of the dauer diapause and proper gonadal migration during larval development; in adults, DAs influence lifespan. Whether Delta(4)- and Delta(7)-DA have unique biological functions is not known. We identified the 3-beta-hydroxysteroid dehydrogenase (3betaHSD) family member HSD-1, which participates in Delta(4)-DA biosynthesis, as an inhibitor of DAF-16/FoxO activity. Whereas IIS promotes the cytoplasmic sequestration of DAF-16/FoxO, HSD-1 inhibits nuclear DAF-16/FoxO activity without affecting DAF-16/FoxO subcellular localization. Thus, HSD-1 and IIS inhibit DAF-16/FoxO activity via distinct and complementary mechanisms. In adults, HSD-1 was required for full lifespan extension in IIS mutants, indicating that HSD-1 interactions with IIS are context-dependent. In contrast to the Delta(7)-DA biosynthetic enzyme DAF-36, HSD-1 is dispensable for proper gonadal migration and lifespan extension induced by germline ablation. These findings provide insights into the molecular interface between DA and IIS pathways and suggest that Delta(4)- and Delta(7)-DA pathways have unique as well as overlapping biological functions in the control of development and lifespan.
authors.affiliation: Life Sciences Institute, University of Michigan, 210 Washtenaw Avenue, Ann Arbor, MI 48109, USA.
authors.forename: Kathleen J
authors.initials: KJ
authors.lastname: Dumas
authors.forename: Chunfang
authors.initials: C
authors.lastname: Guo
authors.forename: Xi
authors.initials: X
authors.lastname: Wang
authors.forename: Kirk B
authors.initials: KB
authors.lastname: Burkhart
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Adams
authors.forename: Hena
authors.initials: H
authors.lastname: Alam
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Hu
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans / Q000235:genetics / Q000502:physiology*; D002782:Cholestenes / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D017238:Genes, Helminth; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D008136:Longevity / Q000235:genetics / Q000502:physiology*; D008954:Models, Biological; D009154:Mutation; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D019076:Transgenes
chemical_list: D002782:Cholestenes; D011993:Recombinant Fusion Proteins; C533800:dafachronic acid; D049452:Green Fluorescent Proteins