AMPK promotes induction of the 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 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 Flcn encoding a tumor suppressor and nutrient sensor folliculin (FLCN). 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 supports the existence of the AMPK-TFEB-FLCN cascade in vivo.