title: Ahnak stimulates BMP2-mediated adipocyte differentiation through Smad1 activation.
abstract: OBJECTIVE
  Previous reports have indicated that Ahnak-deficient mice were protected from high-fat diet-induced obesity. However, the molecular mechanism in which Ahnak mediates adipocyte differentiation and high-fat diet-induced obesity is unclear.
  
  
  METHODS
  Adipocytes from Ahnak knockout (Ahnak(-/-) ) mice and knockdown of Ahnak in C3H10T1/2 were used to investigate the function of Ahnak in adipocyte differentiation. Ahnak-induced adipocyte differentiation was analyzed by Oil Red O staining.
  
  
  RESULTS
  Adipocytes from Ahnak(-/-) mice were smaller than those from wild-type mice. Silencing of Ahnak in C3H10T1/2 and adipose tissue-derived mesenchymal stem cells (ADSCs) from Ahnak(-/-) mice showed severely impaired adipocyte differentiation. Down-regulation of Ahnak in C3H10T1/2 cells and ADSCs from Ahnak(-/-) mice attenuated the phosphorylation and nuclear localization of Smad1 in response to BMP2, whereas Ahnak overexpression in 3T3-L1 cells significantly increased Smad1 activation. Because PPARγ is a well-known transcriptional factor in adipocyte differentiation, the PPARγ expression in Ahnak-mediated adipocyte differentiation was investigated. Transfection of C3H10T1/2 cells with Ahnak siRNA resulted in reduced PPARγ expression apparently through inhibited binding of Smad1 to the Smad1-binding site in the PPARγ promoter. These results suggest that Ahnak regulates adipogenesis by regulating Smad1-dependent PPARγ expression.
  
  
  CONCLUSIONS
  A molecular mechanism was proposed in which Ahnak regulates adipocyte differentiation through Smad1 activation.
authors.affiliation: Department of Life Science, Ewha Womans University, Seoul, Korea.
authors.forename: Sunmee
authors.initials: S
authors.lastname: Shin
authors.affiliation: Laboratory of Developmental Biology and Genomics, College of Veterinary Medicine, and BK21 Program for Veterinary Science, Seoul National University, Daehak-Dong, Gwanak-Gu, Seoul, Korea.
authors.forename: Je Kyung
authors.initials: JK
authors.lastname: Seong
authors.affiliation: Department of Life Science, Ewha Womans University, Seoul, Korea.
authors.forename: Yun Soo
authors.initials: YS
authors.lastname: Bae
mesh_terms: D017667:Adipocytes / Q000378:metabolism*; D050156:Adipogenesis / Q000235:genetics; D000273:Adipose Tissue / Q000378:metabolism; D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000378:metabolism*; D002454:Cell Differentiation / Q000235:genetics; D059305:Diet, High-Fat; D015536:Down-Regulation; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009363:Neoplasm Proteins / Q000378:metabolism*; D009765:Obesity / Q000378:metabolism; D047495:PPAR gamma / Q000378:metabolism*; D051898:Smad1 Protein / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism
chemical_list: C489572:Ahnak protein, mouse; C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D047495:PPAR gamma; D051898:Smad1 Protein; D014157:Transcription Factors