title: 1,25-Dihydroxyvitamin D3 regulation of phorbol ester receptors in HL-60 leukemia cells.
abstract: In this study the relationship between cell binding of phorbol 12,13-dibutyrate (PDBu) and induction of differentiation by 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) was examined. Binding of [3H]PDBu increased within 12 h of 1,25-(OH)2D3 treatment, and a 60-130% increase in [3H]PDBu receptor levels was observed within 24 h. By 48 h, however, [3H]PDBu binding was not different from control. Scatchard analysis of [3H]PDBu binding showed no statistical differences in Kd value (Kd approximately equal to 30 nM) between 1,25-(OH)2D3-treated and control cells 22 h post-treatment; however, a 2-fold increase in Bmax was observed in treated (338 +/- 24 pmol/10(9) cells) compared to control cultures (170 +/- 14 pmol/10(9) cells). Stimulation of [3H]PDBu binding was dependent on 1,25-(OH)2D3 concentrations over a range of 1-100 nM. Homogenates from 1,25-(OH)2D3-treated HL-60 cells also demonstrated an increase (70%) in [3H]PDBu binding to the Ca2+/phospholipid-dependent enzyme protein kinase C as assessed by incubation of cell homogenates with [3H]PDBu in the presence of saturating phosphatidylserine and calcium concentrations. This suggests that the increase in [3H]PDBu binding cannot be entirely explained by modulation of the latter two agents. Cycloheximide (5 microM), an inhibitor of protein synthesis, ablated the 1,25-(OH)2D3-stimulated increase in [3H]PDBu binding to intact HL-60 cells. These data demonstrate that an increase in [3H]PDBu binding occurs early in the course of 1,25-(OH)2D3-induced differentiation, results from an increased number of [3H]PDBu-binding site, and is dependent on protein synthesis.
authors.forename: R E
authors.initials: RE
authors.lastname: Martell
authors.forename: R U
authors.initials: RU
authors.lastname: Simpson
authors.forename: J M
authors.initials: JM
authors.lastname: Taylor
mesh_terms: D029742:Caenorhabditis elegans Proteins; D002117:Calcitriol / Q000494:pharmacology*; D002352:Carrier Proteins; D002460:Cell Line; D006801:Humans; D007700:Kinetics; D015470:Leukemia, Myeloid, Acute; D015240:Phorbol 12,13-Dibutyrate; D010703:Phorbol Esters / Q000378:metabolism*; D011493:Protein Kinase C; D011955:Receptors, Drug; D011971:Receptors, Immunologic / Q000187:drug effects / Q000378:metabolism*
chemical_list: D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D010703:Phorbol Esters; D011955:Receptors, Drug; D011971:Receptors, Immunologic; C083141:phorbol ester binding protein; C027776:phorbol ester receptor; D015240:Phorbol 12,13-Dibutyrate; D011493:Protein Kinase C; D002117:Calcitriol