title: Mechanisms of ligand-induced desensitization of the 5-hydroxytryptamine(2A) receptor.
abstract: We have examined the cellular processes underlying the desensitization of the 5-hydroxytryptamine (5-HT)(2A) receptor induced by agonist or antagonist exposure. Treatment of C6 glioma cells with either 5-HT or the 5-HT(2A) receptor antagonist ketanserin resulted in an attenuation in 5-HT(2A) receptor function, specifically the accumulation of inositol phosphates stimulated by the partial agonist quipazine. 5-HT-induced desensitization of the 5-HT(2A) receptor involved receptor internalization through a clathrin- and dynamin-dependent process because it was prevented by concanavalin A, monodansylcadaverine, and by expression of the dominant negative mutants beta-arrestin (319-418) and dynamin K44A. Although short-term (i.e., 10 min) 5-HT and ketanserin exposure resulted in the same degree of desensitization, ketanserin-induced desensitization was not prevented by these agents and did not involve receptor internalization. In contrast, prolonged ketanserin exposure (i.e., 2 h) resulted in 5-HT(2A) receptor internalization through a clathrin- and dynamin-dependent process, as was observed after agonist treatment. Inhibitors of protein kinase C or calcium-calmodulin kinase II did not attenuate or prevent 5-HT-induced desensitization of the receptor. 5-HT(2A) receptor desensitization induced by 5-HT and prolonged ketanserin treatment, but not by short-term ketanserin treatment, was prevented by the expression of the dominant negative mutant of G protein-coupled receptor kinase (GRK)2, GRK2-K220R, and by an anti-GRK2/3 antibody. Our data indicate a dual mechanism of early and late desensitization by the antagonist ketanserin. Short-term ketanserin treatment reduced the specific binding of the agonist radioligand [(125)I](+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane ([(125)I]DOI) and the ability of 5'-guanylylimidodiphosphate to attenuate this binding, suggesting that at the early stage of antagonist-induced desensitization the capacity of the 5-HT(2A) receptor to couple to G protein is impaired.
authors.affiliation: Department of Pharmacology, University of Texas Health Science Center, San Antonio, Texas 78229-3900, USA.
authors.forename: Nicole R Sullivan
authors.initials: NR
authors.lastname: Hanley
authors.forename: Julie G
authors.initials: JG
authors.lastname: Hensler
mesh_terms: D019393:Arrestin / Q000235:genetics / Q000378:metabolism; D002966:Clathrin / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism; D034281:Dynamins; D004797:Enzyme-Linked Immunosorbent Assay; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism; D006165:Guanylyl Imidodiphosphate / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D007294:Inositol / Q000378:metabolism; D007650:Ketanserin / Q000378:metabolism / Q000494:pharmacology; D008024:Ligands; D044402:Receptor, Serotonin, 5-HT2A; D011985:Receptors, Serotonin / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D012702:Serotonin Antagonists / Q000378:metabolism / Q000494:pharmacology*; D014162:Transfection; D014407:Tumor Cells, Cultured; D051552:beta-Adrenergic Receptor Kinases
chemical_list: D019393:Arrestin; D002966:Clathrin; D008024:Ligands; D044402:Receptor, Serotonin, 5-HT2A; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D006165:Guanylyl Imidodiphosphate; D007294:Inositol; D007650:Ketanserin; D017868:Cyclic AMP-Dependent Protein Kinases; D051552:beta-Adrenergic Receptor Kinases; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D034281:Dynamins