title: TGF-beta receptors are diminished after retinoid exposure in rat liver epithelial cells.
abstract: When rat liver epithelial cells were exposed to retinoic acid or retinol for 24 hr, the levels of transforming growth factor-beta (TGF-beta) receptors were reduced in a dose-dependent way. The decrease appeared after 12 hr of incubation with the retinoids and binding levels remained low until 24 hr after the removal of the molecules. Retinoid treatment induced a fourfold enhancement of transglutaminase (TGase) activity in the cell membranes, and cystamine, an inhibitor of TGase, prevented the decrease of the receptors. Neutralization of TGF-beta by a monoclonal antibody did not suppress the decrease of the binding levels, indicating that decreased TGF-beta binding capacity was not due merely to the internalization of ligand-bound receptors promoted by a stimulation of TCF-beta synthesis. Thus, retinoid treatment resulted in an intense disappearance of the functional receptors from the membranes that seemed to be mediated by increased TGase activity. This phenomenon can represent a strong signal attenuation for TGF-beta following retinoid exposure.
authors.affiliation: Laboratoire de Nutrition et Securite Alimentaire, INRA-CRJ, 78352 Jouy-en-Josas Cedex, France.
authors.forename: T
authors.initials: T
authors.lastname: Mercier
authors.forename: I
authors.initials: I
authors.lastname: Gaillard-Sanchez
authors.forename: P
authors.initials: P
authors.lastname: Martel
authors.forename: C
authors.initials: C
authors.lastname: Heberden
mesh_terms: D000818:Animals; D002460:Cell Line; D004847:Epithelial Cells; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D008099:Liver / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism*; D011503:Transglutaminases / Q000378:metabolism; D014212:Tretinoin / Q000494:pharmacology*; D014801:Vitamin A / Q000494:pharmacology*
chemical_list: D018125:Receptors, Transforming Growth Factor beta; D014801:Vitamin A; D014212:Tretinoin; D011503:Transglutaminases