Sensitization of adenylate cyclase induced by a dopamine D2 receptor mutant: inverse agonism by D2 receptor antagonists
| Autor: | Chuanyu Li, Jason C. Bermak, Clayton M. Bullock, Qun-Yong Zhou, Ming Li |
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| Rok vydání: | 2001 |
| Předmět: |
Agonist
medicine.medical_specialty Growth-hormone-releasing hormone receptor medicine.drug_class Down-Regulation CHO Cells Biology Transfection Beta-1 adrenergic receptor Dopamine receptor D2 Internal medicine Cricetinae Muscarinic acetylcholine receptor M5 medicine Inverse agonist Animals Humans Biological Psychiatry Pharmacology Receptors Dopamine D2 Dopamine D2 Receptor Antagonists Endocrinology Adenylyl Cyclase Inhibitors COS Cells Mutagenesis Site-Directed Dopamine Antagonists Cyclase activity Endogenous agonist Adenylyl Cyclases |
| Zdroj: | Progress in neuro-psychopharmacologybiological psychiatry. 25(7) |
| ISSN: | 0278-5846 |
| Popis: | 1. Mutations of residues in the third intracellular loops of several G-protein coupled receptors have been shown to confer constitutive activation. The authors investigated the effects of one such mutation in the dopamine D2 receptor. 2. Compared to the wild type D2, the mutant D2 receptor (D2T344K) showed a substantial increase in agonist affinity with affinity for antagonists unchanged. The increased agonist affinity was unaffected by pertussis toxin treatment, indicating it is an intrinsic property of the mutant receptor. The potency of dopamine for acute inhibition of forskolin-stimulated cAMP production in stably expressing Chinese Hamster Ovary (CHO) cells was higher for the mutant than the wild type receptor. 3. CHO cells stably expressing D2T344K displayed enhanced responses to forskolin-stimulated adenylate cyclase activity compared with cells stably expressing the wild type D2 receptor. The increased forskolin responsiveness of adenylate cyclase is similar to the sensitization previously observed with wild type D2 receptor after agonist treatment. Adenylate cyclase responsiveness of CHO cells stably expressing D2T344K receptor was not further increased by agonist treatment. 4. Sensitization was blocked by pertussis toxin and D2 receptor antagonists haloperidol, butaclamol, and clozapine, indicating inverse agonist activity of these compounds at D2T344K. Inverse agonist activity was further demonstrated by the finding that overnight treatment with these compounds drastically increased the density of the mutant receptor but had minimal effect on the density of the wild type receptor. 5. Taken together, these results suggest the authors have generated a constitutively active dopamine D2 receptor capable of sensitizing adenylate cyclase in the absence of agonist activation. |
| Databáze: | OpenAIRE |
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