Understanding insulin signalling and its role in regulating ageing in C elegans using pharmacological and genetic approaches

Throughout history aging is an impasse humans have aspired to overcome. In Caenorhabditis elegans, downregulation of Insulin/IGF-1-like signalling (IIS) through mutation of daf-2 (equivalent of the human Insulin receptor) has been observed to cause a substantial lifespan extension via AKT1&2, through activation of the transcription factor DAF-16 (human FOXO3A). Many cancer treatment drugs target AKT; I set out to test whether they could be re-purposed as an anti-ageing therapy. Using a DAF-16::GFP overexpressing strain of C. elegans, we monitored the IIS pathway in response to competitive and allosteric AKT inhibitors, AT13148 and MK2206 respectively, by examining the degree of DAF-16 nuclear accumulation. AT1341 and MK2206 were found not to induce DAF-16 nuclear localisation at concentrations up to 500?M and 200?M respectively.

Secondly, in a separate but related project I undertook work to explore the activation and functional role of a second transcription factor SKN-1 (human NFE2-related factor), in response to reduced IIS. In particular, an isoform of this transcription factor SKN- 1B, expressed in ASI neurones, remains relatively uncharacterised. Using worms expressing a SKN-1B::GFP transgene, the effect of temperature on SKN-1B::GFP expression in the ASIs in response to reduced IIS was determined. Maintenance of SKN-1B in the neurones was found to require insulin signalling at 20°C and 25°C but not 15°C, this effect involved DAF-16 at 20°C but not 25°C.

Finally, in an effort to understand why skn-1b is required for dietary restriction induced longevity, I explored the role of skn-1b in chemo-sensation of food in worms as a function of age. Interestingly, skn-1b knockout worms showed reduced foraging behaviour compared to WT under some conditions.