AMPK promotes induction of a tumor suppressor FLCN through activation of TFEB independently of mTOR
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.\n\nCollectively, 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.