AMPK supports growth in Drosophila by regulating muscle activity and nutrient uptake in the gut

The larval phase of the Drosophila life cycle is characterized by constant food intake, resulting in a two hundred-fold increase in mass over four days. Here we show that the conserved energy sensor AMPK is essential for nutrient intake in Drosophila Mutants lacking dAMPK alpha are small, with low triglyceride levels, small fat body cells and early pupal lethality Using mosaic analysis, we find that dAMPK alpha functions as a nonautonomous regulator of cell growth. Nutrient absorption is impaired in dAMPK alpha mutants, and this defect stems not from altered gut epithelial cell polarity but from impaired peristaltic activity. Expression of a wild-type dAMPK alpha transgene or an activated version of the AMPK target myosin regulatory light chain (MRLC) in the dAMPK alpha mutant visceral musculature restores gut function and growth These data suggest strongly that AMPK regulates visceral smooth muscle function through phosphorylation of MRLC Furthermore, our data show that in Drosophila, AMPK performs an essential cell-nonautonomous function, serving the needs of the organism by promoting activity of the visceral musculature and, consequently. nutrient intake (C) 2010 Elsevier Inc. All rights reserved.