title: Two phorbol ester receptor affinities in partially transformed human urothelial cells and decrease of receptor binding in desensitized cells.
abstract: The presence of specific binding sites for phorbol esters was studied in a transformed but non-tumorigenic human urothelial cell line HCV-29 by assay of specific binding of 3H-phorbol-12,13-dibutyrate (3H-PDBu) to intact living cells. 3H-PDBu bound specifically to HCV-29 cells in a saturable and competitive manner. Scatchard plot analysis of specific binding yielded a curved plot consistent with two binding sites with Kd of 11 nM and 102 nM, respectively. At saturation the corresponding PDBu binding capacities (Bmax) were 8.8 pmol/10(6) cells (5.2 x 10(6) molecules bound per cell) and 2.8 pmol/10(6) cells (1.7 x 10(6) molecules bound per cell). 3H-PDBu binding was displaced by biologically active phorbol ester tumor promoters such as 12-O-tetradecanoylphorbol-13-acetate (TPA) and mezerein, but not by tumor promoters such as L-tryptophan, anthranilic acid and sodium saccharin. In cells desensitized by pretreatment with 1 microgram/ml (2 microM) TPA or PDBu for 24 h the level of binding was reduced to 28% of the level in non-exposed cells. The ability of desensitized cells to bind 3H-PDBu was gradually restored within 5-6 days. At the same time the cells became sensitive to the morphological alteration induced by PDBu. This suggests that desensitization of HCV-29 cells is due to a decreased receptor-ligand binding capacity probably associated with down regulation of the phorbol ester receptors.
authors.affiliation: Fibiger Institute, Danish Cancer Society, Copenhagen.
authors.forename: B
authors.initials: B
authors.lastname: Christensen
authors.forename: J
authors.initials: J
authors.lastname: Skouv
authors.forename: J
authors.initials: J
authors.lastname: Kieler
authors.forename: H
authors.initials: H
authors.lastname: Autrup
mesh_terms: D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D002461:Cell Line, Transformed; D002471:Cell Transformation, Neoplastic; D004305:Dose-Response Relationship, Drug; D006801:Humans; D015240:Phorbol 12,13-Dibutyrate / Q000378:metabolism; D011493:Protein Kinase C; D011955:Receptors, Drug / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D001743:Urinary Bladder / Q000187:drug effects / Q000378:metabolism; D001749:Urinary Bladder Neoplasms / Q000378:metabolism*
chemical_list: D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D011955:Receptors, Drug; C083141:phorbol ester binding protein; C027776:phorbol ester receptor; D015240:Phorbol 12,13-Dibutyrate; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate