An insulin signaling pathway couples feeding and nutritional status in mammals to metabolism in most tissues. An insulin-like signaling pathway regulates longevity and metabolism in C. elegans. This is reminiscent and may be mechanistically related to the longevity increase caused by caloric restriction in mammals. Our genetic analysis has also revealed that the signal transduction components and transcriptional outputs of C. elegans insulin-like signaling pathway. Mammalian orthologs of many of these genes have been identified. Thus the genetic components of the C. etegans insulin signaling pathway may be key components of a mammalian longevity determining pathway. While many points of congruence have been identified, we know from genetic epistasis experiments that there are missing components. We will identify these components by second generation genetics, using the mutants identified in the first round of genetics as tools in the genetics of this round. We will also explore the connection between reproductive longevity and organismal longevity by genetically analysing the regulation of reproductive senescence in C. elegans. We have shown that C. elegans has a large family of insulin like hormones and that human insulin will function in C. elegans. Our genetics has revealed that not all responses to C. elegans as well as human insulin are mediated by the canonical insulin response receptors. We will explore the novel insulin response pathway by genetic analysis. We will determine the molecular identity of the worm genes revealed by the extensive genetic analysis proposed in this grant, search for human homologues of those genes, and test whether these human proteins in fact can function in the C. elegans insulin-like signaling pathway, that is, are functional homologues. In addition to their possible roles in longevity control, the insulin signaling genes we have identified by C. elegans genetics may reveal components of insulin signaling in mammals that are important for the understanding and eventual treatment of diabetes. Diabetes is a common disease that affects the production or response to insulin, causing devastating metabolic dysregulations. The molecular basis of the defective insulin response in the adult onset or type IIdiabetes is unknown. It is clear that it is at least in part a genetic disease. Saturation genetic analysis of the homologous C. elegans metabolic control pathway has revealed genes that act downstream of the insulin-like receptor as well as other neuroendocrine signals that converge with insulin. The products of the genes we have identified may be targets for pharmaceutical development of diabetes therapies.
