title: Regulation of mitochondrial oxidative metabolism by tumor suppressor FLCN.
abstract: BACKGROUND
  Birt-Hogg-Dubé (BHD) syndrome is a hereditary hamartoma syndrome that predisposes patients to develop hair follicle tumors, lung cysts, and kidney cancer. Genetic studies of BHD patients have uncovered the causative gene, FLCN, but its function is incompletely understood.
  
  
  METHODS
  Mice with conditional alleles of FLCN and/or peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PPARGC1A), a transcriptional coactivator that regulates mitochondrial biogenesis, were crossbred with mice harboring either muscle creatine kinase (CKM) -Cre or myogenin (MYOG) -Cre transgenes to knock out FLCN and/or PPARGC1A in muscle, or cadherin 16 (CDH16)- Cre transgenes to knock out FLCN and/or PPARGC1A in kidney. Real-time polymerase chain reaction, immunoblotting, electron microscopy, and metabolic profiling assay were performed to evaluate mitochondrial biogenesis and function in muscle. Immunoblotting, electron microscopy, and histological analysis were used to investigate expression and the pathological role of PPARGC1A in FLCN-deficient kidney. Real-time polymerase chain reaction, oxygen consumption measurement, and flow cytometry were carried out using a FLCN-null kidney cancer cell line. All statistical analyses were two-sided.
  
  
  RESULTS
  Muscle-targeted FLCN knockout mice underwent a pronounced metabolic shift toward oxidative phosphorylation, including increased mitochondrial biogenesis (FLCN ( f/f ) vs FLCN ( f/f ) /CKM-Cre: % mitochondrial area mean = 7.8% vs 17.8%; difference = 10.0%; 95% confidence interval = 5.7% to 14.3%; P < .001), and the observed increase in mitochondrial biogenesis was PPARGC1A dependent. Reconstitution of FLCN-null kidney cancer cells with wild-type FLCN suppressed mitochondrial metabolism and PPARGC1A expression. Kidney-targeted PPARGC1A inactivation partially rescued the enlarged kidney phenotype and abrogated the hyperplastic cells observed in the FLCN-deficient kidney.
  
  
  CONCLUSIONS
  FLCN deficiency and subsequent increased PPARGC1A expression result in increased mitochondrial function and oxidative metabolism as the source of cellular energy, which may give FLCN-null kidney cells a growth advantage and drive hyperplastic transformation.
authors.affiliation: Urologic Oncology Branch, National Cancer Institute, 10 Center Dr, MSC 1107, CRC Rm 1-5940W, Bethesda, MD 20892, USA.
authors.forename: Hisashi
authors.initials: H
authors.lastname: Hasumi
authors.forename: Masaya
authors.initials: M
authors.lastname: Baba
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Hasumi
authors.forename: Ying
authors.initials: Y
authors.lastname: Huang
authors.forename: Hyoungbin
authors.initials: H
authors.lastname: Oh
authors.forename: Robert M
authors.initials: RM
authors.lastname: Hughes
authors.forename: Mara E
authors.initials: ME
authors.lastname: Klein
authors.forename: Shoichi
authors.initials: S
authors.lastname: Takikita
authors.forename: Kunio
authors.initials: K
authors.lastname: Nagashima
authors.forename: Laura S
authors.initials: LS
authors.lastname: Schmidt
authors.forename: W Marston
authors.initials: WM
authors.lastname: Linehan
mesh_terms: D000818:Animals; D058249:Birt-Hogg-Dube Syndrome / Q000235:genetics; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism*; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D007680:Kidney Neoplasms / Q000378:metabolism* / Q000473:pathology*; D051379:Mice; D018345:Mice, Knockout; D008854:Microscopy, Electron; D008928:Mitochondria / Q000378:metabolism; D063269:Mitochondrial Turnover; D009132:Muscles / Q000378:metabolism* / Q000473:pathology; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D010766:Phosphorylation; D011518:Proto-Oncogene Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*
chemical_list: C526060:Bhd protein, mouse; C476078:FLCN protein, human; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; C485290:Ppargc1a protein, mouse; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; C111264:peroxisome-proliferator-activated receptor-gamma coactivator-1