The tumor suppressor folliculin regulates AMPK-dependent metabolic transformation
Ming Yan, … , Andrew R. Tee, Arnim Pause
Ming Yan, … , Andrew R. Tee, Arnim Pause
Published April 24, 2014
Citation Information: J Clin Invest. 2014;124(6):2640-2650. https://doi.org/10.1172/JCI71749.
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Research Article Oncology

The tumor suppressor folliculin regulates AMPK-dependent metabolic transformation

Abstract

The Warburg effect is a tumorigenic metabolic adaptation process characterized by augmented aerobic glycolysis, which enhances cellular bioenergetics. In normal cells, energy homeostasis is controlled by AMPK; however, its role in cancer is not understood, as both AMPK-dependent tumor-promoting and -inhibiting functions were reported. Upon stress, energy levels are maintained by increased mitochondrial biogenesis and glycolysis, controlled by transcriptional coactivator PGC-1α and HIF, respectively. In normoxia, AMPK induces PGC-1α, but how HIF is activated is unclear. Germline mutations in the gene encoding the tumor suppressor folliculin (FLCN) lead to Birt-Hogg-Dubé (BHD) syndrome, which is associated with an increased cancer risk. FLCN was identified as an AMPK binding partner, and we evaluated its role with respect to AMPK-dependent energy functions. We revealed that loss of FLCN constitutively activates AMPK, resulting in PGC-1α–mediated mitochondrial biogenesis and increased ROS production. ROS induced HIF transcriptional activity and drove Warburg metabolic reprogramming, coupling AMPK-dependent mitochondrial biogenesis to HIF-dependent metabolic changes. This reprogramming stimulated cellular bioenergetics and conferred a HIF-dependent tumorigenic advantage in FLCN-negative cancer cells. Moreover, this pathway is conserved in a BHD-derived tumor. These results indicate that FLCN inhibits tumorigenesis by preventing AMPK-dependent HIF activation and the subsequent Warburg metabolic transformation.

Authors

Ming Yan, Marie-Claude Gingras, Elaine A. Dunlop, Yann Nouët, Fanny Dupuy, Zahra Jalali, Elite Possik, Barry J. Coull, Dmitri Kharitidi, Anders Bondo Dydensborg, Brandon Faubert, Miriam Kamps, Sylvie Sabourin, Rachael S. Preston, David Mark Davies, Taren Roughead, Laëtitia Chotard, Maurice A.M. van Steensel, Russell Jones, Andrew R. Tee, Arnim Pause

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Figure 4

AMPK activation upon loss of FLCN binding drives the PGC-1α-ROS–mediated HIF induction.

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AMPK activation upon loss of FLCN binding drives the PGC-1α-ROS–mediated...
(A) Western blot analysis of AMPK expression (AMPKα) and activation (pT172 AMPKα [pAMPKα]) levels and acetyl-CoA carboxylase (ACC) expression and activation (pS79 ACC [pACC]) levels in the indicated MEFs. Actin was used as loading control. (B) Western blot analysis of Ampk–/– or Ampk+/+ MEFs downregulated (shFlcn) for FLCN or not (shEV). Actin was used as loading control. (C) Relative PPARGC1A mRNA expression and (D) ROS production levels in the indicated MEFs. (E–G) Flcn KO MEFs were rescued with FLCN WT, FLCN S62A mutant (S62A), or EV constructs, and (E) the extent of FLCN binding to AMPKα and FNIP1 was determined by coimmunoprecipitation. The effect of the S62A mutation on (F and G) PGC-1α, (G) HIF target gene expression, and (F) AMPK activation (pT172 AMPKα) was assayed by (F) Western blot and (G) qRT-PCR. Results in A, B, E, and F are representative of 3 independent experiments and data in C, D, and G represent the mean ± SD of 4 independent experiments performed in triplicate. **P < 0.01, ***P < 0.001.