The C. elegans insulin-like peptides (ILPs)

Insulin and insulin-like peptides (ILPs) are conserved in living organisms to modulate homeostasis by functioning as ligands. For understanding of molecular mechanisms regulated by the ligands, the nematode Caenorhabditis elegans is a good model since: 1) the C. elegans genome size is small with over 40% homology to the human genome, 2) numerous genetic methods are available, and 3) the worms are transparent throughout the life cycle, so that the secretion of peptide hormones can be followed at cellular level in living preparations by GFP-tagged peptides. In this review, we describe the general appearance of the insulin/insulin-like growth factor (IGF)-1 signaling (IIS), and then focus on physiological functions, secretion, and transcriptional regulation of the C. elegans ILPs.