dTORC gene profiling

In fasted mammals, glucose homeostasis is maintained through activation of the cAMP responsive CREB coactivator TORC2, which stimulates the gluconeogenic program in concert with the forkhead transcription factor FOXO1. Here we show that starvation also triggers TORC activation in Drosophila, where it maintains energy balance by promoting the expression of CREB target genes in the brain. TORC mutant flies have reduced glycogen and lipid stores, and they are sensitive to starvation as well as oxidative stress. Neuronal TORC expression rescued starvation and oxidative stress sensitivity as well as CREB target gene expression in TORC mutants. During refeeding, increases in insulin signaling inhibited TORC activity in wild type flies by stimulating the Salt Inducible Kinase 2 (SIK2)-mediated phosphorylation and subsequent degradation of TORC. Depletion of neuronal SIK2 increased TORC activity and enhanced resistance to starvation and oxidative stress in adult flies. As disruption of insulin signaling, either by ablation of insulin-producing cells (IPCs) or by mutation of the insulin receptor adaptor gene chico, also increased TORC activity, our results illustrate the importance of an insulin-regulated pathway in brain that promotes energy balance in Drosophila.

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Wang B, Goode J, Best J, Meltzer J, Schilman PE, Chen J, Garza D, Thomas JB, Montminy M