AMPK signaling mediates synphilin-1-induced hyperphagia and obesity in Drosophila

Expression of synphilin-1 in neurons induces hyperphagia and obesity in a Drosophila model. However, the molecular pathways underlying synphilin-1-linked obesity remain unclear. Here, Drosophila models and genetic tools were used to study the synphilin-1-linked pathways in energy balance by combining molecular biology and pharmacological approaches. We found that expression of human synphilin-1 in flies increased AMP-activated kinase (AMPK) phosphorylation at Thr172 compared with that in non-transgenic flies. Knockdown of AMPK reduced AMPK phosphorylation and food intake in non-transgenic flies, and further suppressed synphilin-1-induced AMPK phosphorylation, hyperphagia, fat storage and body weight gain in transgenic flies. Expression of constitutively activated AMPK significantly increased food intake and body weight gain in non-transgenic flies, but it did not alter food intake in the synphilin-1 transgenic flies. In contrast, expression of dominant-negative AMPK reduced food intake in both non-transgenic and synphilin-1 transgenic flies. Treatment with STO-609 also suppressed synphilin-1-induced AMPK phosphorylation, hyperphagia and body weight gain. These results demonstrate that the AMPK signaling pathway plays a critical role in synphilin-1-induced hyperphagia and obesity. These findings provide new insights into the mechanisms of synphilin-1-controlled energy homeostasis.