Regulation of C. elegans DAF-16 and its human ortholog FKHRL1 by the daf-2 insulin-like signaling pathway

Curr Biol. 2001 Dec 11;11(24):1950-7. doi: 10.1016/s0960-9822(01)00595-4.


C. elegans insulin-like signaling regulates metabolism, development, and life span. This signaling pathway negatively regulates the activity of the forkhead transcription factor DAF-16. daf-16 encodes multiple isoforms that are expressed in distinct tissue types and are probable orthologs of human FKHRL1, FKHR, and AFX. We show that human FKHRL1 can partially replace DAF-16, proving the orthology. In mammalian cells, insulin and insulin-like growth factor signaling activate AKT/PKB kinase to negatively regulate the nuclear localization of DAF-16 homologs (reviewed in ). We show that the absence of AKT consensus sites on DAF-16 is sufficient to cause dauer arrest in daf-2(+) animals, proving that daf-16 is the major output of insulin signaling in C. elegans. FKHR, FKRHL1, and AFX may similarly be the major outputs of mammalian insulin signaling. daf-2 insulin signaling, via AKT kinases, negatively regulates DAF-16 by controlling its nuclear localization. Surprisingly, we find that daf-7 TGF-beta signaling also regulates DAF-16 nuclear localization specifically at the time when the animal makes the commitment between diapause and reproductive development. daf-16 function is supported by the combined action of two distinct promoter/enhancer elements, whereas the coding sequences of two major DAF-16 isoforms are interchangeable. Together, these observations suggest that the combined effects of transcriptional and posttranslational regulation of daf-16 transduce insulin-like signals in C. elegans and perhaps more generally.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Caenorhabditis elegans / genetics*
  • Caenorhabditis elegans Proteins*
  • DNA-Binding Proteins / physiology*
  • Forkhead Box Protein O1
  • Forkhead Box Protein O3
  • Forkhead Transcription Factors
  • Gene Expression Regulation / physiology*
  • Humans
  • Insulin / metabolism*
  • Receptor, Insulin / physiology*
  • Signal Transduction*
  • Transcription Factors / genetics*
  • Transcription Factors / physiology*


  • Caenorhabditis elegans Proteins
  • DNA-Binding Proteins
  • FOXO1 protein, human
  • FOXO3 protein, human
  • Forkhead Box Protein O1
  • Forkhead Box Protein O3
  • Forkhead Transcription Factors
  • Insulin
  • Transcription Factors
  • daf-16 protein, C elegans
  • DAF-2 protein, C elegans
  • Receptor, Insulin