DAF-16-dependent and independent expression targets of DAF-2 insulin receptor-like pathway in Caenorhabditis elegans include FKBPs.

The daf-2 insulin-like receptor pathway regulates development and life-span in Caenorhabditis elegans. Reduced DAF-2 signaling leads to changes in downstream targets via the daf-16 gene, a fork-head transcription factor which is regulated by DAF-2, and results in extended life-span. Here, we describe the first identification of genes whose expression is controlled by the DAF-2 signaling cascade. dao-1, dao-2, dao-3, dao-4, dao-8 and dao-9 are down-regulated in daf-2 mutant adults compared to wild-type adults, whereas dao-5, dao-6 and dao-7 are up-regulated. The latter genes are negatively regulated by DAF-2 signaling and positively regulated by DAF-16. Positive regulation by DAF-2 on dao-1, dao-4 and dao-8 was mediated by DAF-16, whereas daf-16 mediates only part of DAF-2 signaling for dao-2 and dao-9. Regulation by DAF-2 is most likely DAF-16 independent for dao-3 and hsp-90. RNA levels of dao-5 and dao-6 showed elevated expression in daf-2 adults, as well as being strongly expressed in dauer larvae. In contrast, hsp-90 transcript levels are low in daf-2 mutant adults though they are enriched in dauer larvae, indicating overlapping but not identical mechanisms of efficient life maintenance in stress-resistant dauer larvae and long-lived daf-2 mutant adults. dao-1, dao-8 and dao-9 are homologs of the FK506 binding proteins that interact with the mammalian insulin pathway. dao-3 encodes a putative methylenetetrahydrofolate dehydrogenase. DAO-5 shows 33 % identity with human nucleolar phosphoprotein P130. dao-7 is similar to the mammalian ZFP36 protein. Distinct regulatory patterns of dao genes implicate their diverse positions within the signaling network of DAF-2 pathway, and suggest they have unique contributions to development, metabolism and longevity.

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