Characterization of phorbol esters binding to K 562 cells.
Binding of 20-[3H]-phorbol 2, 13-dibutyrate [( 3H] PDB) to intact human K 562 cells was characterized. Specific binding of [3H] PDB to K 562 cells at 20 degrees C or 37 degrees C reached a maximum within 15-20 min. Maximal specific [3H] PDB binding to K 562 cells was followed by a decline (down regulation) of radioacticity. This down regulation was temperature dependent; no loss of radioactivity occurred by 1 hour at 4 degrees C. When [3H] PDB binding was carried out a 4 degrees C, [3HDB bound to K 562 cells in a rapid, specific, and reversible manner. Phorbol esters which lack tumor-promoting activity, did not inhibit [3H] PDB binding. A Scatchard analysis was compatible with one class of binding sites, Kd = 50 nM and about 2 X 10(5) binding sites per cell. Human serum inhibited specific binding of [3H] PDB. The effect of several chemical compounds on [3H] PDB binding was also investigated. Most of the compounds tested such as butyrate, hemin, gamma-globulins, transferrin, insulin, EGF, and albumin failed to significantly affect the binding of [3H] PDB. In contrast, retinoic acid and quinacrine significantly affected the binding of [3H] PDB: retinoic acid induced a marked increase of [3H] PDB binding which was dose dependent; quinacrine induced a decrease of [3H] PDB binding, even at low concentration.
D001667:Binding, Competitive; D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D002460:Cell Line; D006801:Humans; D004915:Leukemia, Erythroblastic, Acute / Q000032:analysis*; D015470:Leukemia, Myeloid, Acute / Q000378:metabolism*; D015240:Phorbol 12,13-Dibutyrate; D010703:Phorbol Esters / Q000378:metabolism; D011493:Protein Kinase C; D011956:Receptors, Cell Surface / Q000032:analysis* / Q000187:drug effects; D011955:Receptors, Drug; D014316:Tritium
D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D010703:Phorbol Esters; D011956:Receptors, Cell Surface; D011955:Receptors, Drug; C083141:phorbol ester binding protein; C027776:phorbol ester receptor; D014316:Tritium; D015240:Phorbol 12,13-Dibutyrate; D011493:Protein Kinase C