title: Phorbol esters alter muscarinic receptor binding and inhibit polyphosphoinositide breakdown in human neuroblastoma (SH-SY5Y) cells.
abstract: Many recent reports have indicated that the effect of the phorbol ester tumor promoters is mediated through the Ca2+/phospholipid dependent protein kinase C. We have investigated the effect of two biologically active phorbol esters, 4 beta-phorbol 12 beta-myristate 13 alpha-acetate (PMA) and 4 beta-phorbol 12 beta,13 alpha-didecanoate (beta PDD) on muscarinic agonist binding and receptor-stimulated phosphoinositide breakdown in cultured human neuroblastoma (SH-SY5Y) cells. Preincubation of these cells with phorbol esters significantly reduced the carbachol-stimulated breakdown of inositol phospholipids and caused a decrease of agonist affinity for [3H](-)methyl quinuclidinyl benzilate ([3H](-)MQNB) binding without affecting the affinity of antagonist to the muscarinic receptor. The nontumor promoting 4 alpha-phorbol 12 beta,12 alpha-didecanoate (alpha PDD) was ineffective in our studies. These results suggest that the activation of protein kinase C may play an important role in regulating the muscarinic receptor system.
mesh_terms: D001285:Atropine / Q000494:pharmacology; D002460:Cell Line; D006801:Humans; D009447:Neuroblastoma / Q000378:metabolism; D010703:Phorbol Esters / Q000494:pharmacology*; D010716:Phosphatidylinositols / Q000378:metabolism*; D011493:Protein Kinase C / Q000032:analysis; D011976:Receptors, Muscarinic / Q000187:drug effects* / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D010703:Phorbol Esters; D010716:Phosphatidylinositols; D011976:Receptors, Muscarinic; C008876:phorbol-12,13-didecanoate; D001285:Atropine; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate