Agonist-induced desensitization and loss of high-affinity binding sites of stably expressed human 5-HT1A receptors.
Exposure of HeLa cells stably expressing cloned human 5-hydroxytryptamine (5-HT)1A receptors (HA7 cells) to the agonist 8-hydroxy-2-(di-N-propylamino)-tetralin (8-OH-DPAT) results in a loss of high-affinity binding sites and a desensitization of receptor-adenylate cyclase coupling, as measured by 5-HT1A-mediated inhibition of forskolin-stimulated adenylate cyclase activity. These responses can also be observed after exposure to forskolin, which activates cyclic AMP-dependent protein kinase A or after treatment with known activators of protein kinase C (PKC) such as phorbol-12-myristate 13-acetate (PMA). The responses elicited by exposure to 8-OH-DPAT or PMA can be blocked completely by inhibitors of PKC and also by 24-hr exposure to PMA. Preincubation of HA7 cells with 8-OH-DPAT also stimulates hydrolysis of inositol phospholipids and the production of arachidonic acid. Inhibition of phospholipase A2 with quinacrine or by removal of extracellular Ca++ blocks the agonist-mediated loss of 5-HT1A receptor binding sites. These data demonstrate that agonist-induced down regulation of the 5-HT1A receptor occurs after stimulation of both the PKC and phospholipase A2 signaling pathways, both of which may activate PKC. The subsequent response is a loss of high-affinity ligand binding sites and functional receptor coupling to adenylate cyclase.
Harrington
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Nancy Pritzker Laboratory of Developmental and Molecular Neurobiology, Department of Psychiatry and Behavioral Sciences, Stanford University Medical Center, California.
Shaw
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Zhong
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Ciaranello
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D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000067956:Adenylyl Cyclase Inhibitors; D016718:Arachidonic Acid / Q000494:pharmacology; D001665:Binding Sites / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D004789:Enzyme Activation; D006367:HeLa Cells; D006801:Humans; D008024:Ligands; D010716:Phosphatidylinositols / Q000378:metabolism; D010741:Phospholipases A / Q000378:metabolism; D054467:Phospholipases A2; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D011796:Quinacrine / Q000494:pharmacology; D011985:Receptors, Serotonin / Q000187:drug effects* / Q000378:metabolism; D012701:Serotonin / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D000067956:Adenylyl Cyclase Inhibitors; D008024:Ligands; D010716:Phosphatidylinositols; D011985:Receptors, Serotonin; D005576:Colforsin; D016718:Arachidonic Acid; D012701:Serotonin; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D011493:Protein Kinase C; D010741:Phospholipases A; D054467:Phospholipases A2; D011796:Quinacrine; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium