title: Altered dynamics of transforming growth factor β(TGF-β) receptors in scleroderma fibroblasts.
abstract: OBJECTIVE
  To investigate the difference in the dynamics of transforming growth factor β (TGF-β) receptors between normal and scleroderma fibroblasts.
  
  
  METHODS
  The cell surface expression levels of TGF-β receptors were determined by biotinylation and immunoprecipitation assay. The dynamics of TGF-β receptors on the cell surface was determined by the reversible biotinylation assay. The subcellular localisation of TGF-β receptors was determined by immunoprecipitation using antibodies against clathrin and caveolin.
  
  
  RESULTS
  Although the total expression levels of TGF-β receptors were elevated in scleroderma fibroblasts compared with normal fibroblasts, there was no significant difference in the cell surface expression levels of TGF-β receptors between these two groups. However, the internalisation rate of TGF-β receptors was higher in scleroderma fibroblasts compared with normal fibroblasts. Furthermore, caveolin constitutively made a complex with TGF-β receptors, while the interaction of clathrin with TGF-β receptors was marginal in scleroderma fibroblasts.
  
  
  CONCLUSIONS
  The dynamics of TGF-β receptors on the cell surface is accelerated in scleroderma fibroblasts. Considering that the activation state of TGF-β signalling is regulated by a balance between the clathrin-dependent internalisation and the lipid raft-caveolar internalisation, the accumulation of TGF-β receptors in caveolin-positive vesicles may result in the deceleration of caveolin-dependent internalisation and subsequently lead to the relative acceleration of clathrin-dependent internalisation.
authors.affiliation: Department of Dermatology, Faculty of Medicine, University of Tokyo, Bunkyo-ku, Tokyo, Japan. yasano-tky@umin.ac.jp
authors.forename: Yoshihide
authors.initials: Y
authors.lastname: Asano
authors.forename: Hironobu
authors.initials: H
authors.lastname: Ihn
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Jinnin
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Tamaki
authors.forename: Shinichi
authors.initials: S
authors.lastname: Sato
mesh_terms: D019921:Biotinylation; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D005347:Fibroblasts / Q000378:metabolism*; D006801:Humans; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism*; D012595:Scleroderma, Systemic / Q000378:metabolism* / Q000473:pathology; D012867:Skin / Q000378:metabolism
chemical_list: D018125:Receptors, Transforming Growth Factor beta