title: DAPIT Over-Expression Modulates Glucose Metabolism and Cell Behaviour in HEK293T Cells.
abstract: BACKGROUND
  Diabetes Associated Protein in Insulin-sensitive Tissues (DAPIT) is a subunit of mitochondrial ATP synthase and has also been found to associate with the vacuolar H+-ATPase. Its expression is particularly high in cells with elevated aerobic metabolism and in epithelial cells that actively transport nutrients and ions. Deletion of DAPIT is known to induce loss of mitochondrial ATP synthase but the effects of its over-expression are obscure.
  
  
  RESULTS
  In order to study the consequences of high expression of DAPIT, we constructed a transgenic cell line that constitutively expressed DAPIT in human embryonal kidney cells, HEK293T. Enhanced DAPIT expression decreased mtDNA content and mitochondrial mass, and saturated respiratory chain by decreasing H+-ATP synthase activity. DAPIT over-expression also increased mitochondrial membrane potential and superoxide level, and translocated the transcription factors hypoxia inducible factor 1α (Hif1α) and β-catenin to the nucleus. Accordingly, cells over-expressing DAPIT used more glucose and generated a larger amount of lactate compared to control cells. Interestingly, these changes were associated with an epithelial to mesenchymal (EMT)-like transition by changing E-cadherin to N-cadherin and up-regulating several key junction/adhesion proteins. At physiological level, DAPIT over-expression slowed down cell growth by G1 arrest and migration, and enhanced cell detachment. Several cancers also showed an increase in genomic copy number of Usmg5 (gene encoding DAPIT), thereby providing strong correlative evidence for DAPIT possibly having oncogenic function in cancers.
  
  
  CONCLUSIONS
  DAPIT over-expression thus appears to modulate mitochondrial functions and alter cellular regulations, promote anaerobic metabolism and induce EMT-like transition. We propose that DAPIT over-expression couples the changes in mitochondrial metabolism to physiological and pathophysiological regulations, and suggest it could play a critical role in H+-ATP synthase dysfunctions.
authors.affiliation: Tampere Centre for Child Health Research, University of Tampere, Tampere, Finland.
authors.forename: Heidi
authors.initials: H
authors.lastname: Kontro
authors.affiliation: Institute of Biomedical Technology, University of Tampere, Tampere, Finland.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Cannino
authors.affiliation: INSERM UMR 1141, Paris, France; Université Paris 7, Paris, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Rustin
authors.affiliation: Institute of Biomedical Technology, University of Tampere, Tampere, Finland.
authors.forename: Eric
authors.initials: E
authors.lastname: Dufour
authors.affiliation: Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland.
authors.forename: Heikki
authors.initials: H
authors.lastname: Kainulainen
mesh_terms: D021581:Active Transport, Cell Nucleus; D058750:Epithelial-Mesenchymal Transition; D018628:Gene Dosage; D015870:Gene Expression; D005947:Glucose / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D019344:Lactic Acid / Q000096:biosynthesis; D008928:Mitochondria / Q000378:metabolism; D025261:Mitochondrial Proton-Translocating ATPases / Q000235:genetics* / Q000378:metabolism; D009369:Neoplasms / Q000235:genetics
chemical_list: C000606721:ATP5MK protein, human; D019344:Lactic Acid; D025261:Mitochondrial Proton-Translocating ATPases; D005947:Glucose