AMP-activated protein kinase (AMPK) is a central energy sensor and master regulator of energy homeostasis. AMPK not only elicits acute metabolic responses, but also promotes metabolic reprogramming and adaptions in the long-term through regulation of specific transcription factors/co-activators. We performed a whole-genome transcriptome profiling in wild-type and AMPK-deficient mouse embryonic fibroblasts (MEF) and mouse primary hepatocytes that had been treated with two distinct classes of small-molecule AMPK activators, namely 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) or 991. This led to the identification of distinct compound-dependent gene expression signatures and to the discovery of several AMPK-regulated genes, including folliculin (Flcn), a gene encoding for a tumor suppressor and nutrient sensor. Gene set enrichment and pathway analyses identified the lysosomal pathway and the associated transcription factor EB (TFEB) as key transcriptional mediator responsible for AMPK-dependent gene expression changes. AMPK-induced Flcn expression was abolished in TFEB/TFE3 double knockout MEF and the promoter activity of Flcn was profoundly reduced when its putative TFEB-binding site was mutated.Mechanistically, we have found that AMPK promotes the dephosphorylation and nuclear localization of TFEB independently of mTOR activity.Collectively, we identified the AMPK-TFEB-FLCN axis as a potential key regulator for cellular and metabolic homeostasis. Moreover, data from zebrafish with physiologically and pharmacologically activated AMPK confirmed the AMPK-TFEB-FLCN cascade in vivo.is the tumor suppressor kinase LKB1 11 . In some cell types, Thr172 can be phosphorylated in a Ca 2+ -mediated process catalyzed by Ca 2+ /calmodulin-dependent protein kinase kinases 12 .AMPK is considered an attractive therapeutic target for metabolic disorders since AMPK activation brings about metabolic responses anticipated to counteract the metabolic abnormalities associated with obesity, insulin resistance, and type 2 diabetes 13,14 . Indeed several compounds, which can be divided into three categories 12 , have been reported to activate AMPK and elicit metabolic effects in cellular and pre-clinical studies. The first class comprises indirect activators which, through inhibition of mitochondrial respiration and eventual suppression of ATP synthesis, increase cellular AMP:ATP or ADP:ATP ratios (e.g. metformin, resveratrol) 15 .