Insulin signaling is a major pathway controlling lifespan in multiple organisms, such as worms, flies and mammals. The insulin signaling pathway initiated by the activation of the insulin receptor (DAF-2) brings about the repression of the downstream transcription factor DAF-16. DAF-16 is one of the key transcription factors that regulate the expression of genes involved in lifespan as well as other functions such as development, immunity and stress resistance. We have previously conducted a genome wide RNAi screen to identify genes that are essential for enhanced longevity in
daf-2 mutant worms {Samuelson, 2007}1. This screen led to the identification of 103 gene inactivations which cause premature aging (the "progeric gene panel", PGP) . Interestingly, 19 genes in the PGP are annotated to be involved in endosomal protein sorting or vesicular trafficking. Similar studies in yeast have also identified genes involved in vacuolar protein sorting to be essential for longevity suggesting a conserved role for proper endosomal function in regulating aging {Fabrizio, 2010}2. However, the mechanism by which endocytosis influences longevity is still not clear. To explore this further, our lab has undertaken a systems level analysis to identify the members of the PGP that are involved in endocytosis, the ER unfolded protein response (ERUPR), and protein homeostasis. To this end, transgenic worms for different endocytosis markers such as the Rab GTPases and GFP fusions to those proteins whose proper localization within the worm depends on functional endocytic machinery have been screened. While the endocytosis machinery is critical to protein degradation and proper protein sorting, ER serves as a primary site for protein synthesis and folding and
daf-2 mutant animals exhibit lower levels of the ERUPR marker
hsp-4::GFP indicating improved ER homeostasis {Korenblit, 2010}3 . To identify the members of the PGP that influence longevity via the ER stress response pathway,
hsp-4::GFP transgenic worms have been screened to identify gene inactivations that either induce the ERUPR in the absence of stress or conversely impair the ERUPR after stress. Lastly, we have identified the members of the PGP that cause the premature collapse of protein homeostasis, as measured by foci formation of Q35::YFP. Highlights of this comprehensive analysis will be presented. References 1. Samuelson et al (2007) Genes Dev 21(22):2976-94 2. Fabrizio et al (2010) PLOS Genet. 6 (7):
e1001024 3. Korenblit et al (2010) PNAS 107(21):9730-5.