Molecular cloning and expression of a 5-hydroxytryptamine7 serotonin receptor subtype.
We have utilized the polymerase chain reaction technique to selectively amplify a G protein-coupled receptor cDNA from rat kidney proximal convoluted tubule mRNA, which exhibits high homology with previously cloned serotonin receptors. Sequencing of a full-length clone isolated from a rat hippocampal cDNA library revealed an open reading frame of 1,212 base pairs encoding a 404-residue protein with seven hydrophobic regions predicted to represent transmembrane-spanning domains. Within the transmembrane regions, this receptor was found to be 44-50% identical with various members of the 5-HT1, 5-HT5, and 5-HT6 subfamilies with lower (37-40%) homology to the 5-HT2-like receptors. Northern blots revealed a approximately 3.6-kilobase transcript localized in various brain regions with the following rank order of abundance: hypothalamus > hippocampus = mesencephalon > cerebral cortex = olfactory bulb > olfactory tubercle. Expression of this clone in COS-7 cells resulted in the appearance of high affinity, saturable binding of [3H]lysergic acid diethylamide ([3H]LSD; KD = 5 nM) and [3H]serotonin ([3H]5-HT; KD = 1 nM). Among endogenous biogenic amines, only 5-HT completely inhibited radioligand binding. The inhibition of radioligand binding by other serotonergic agents revealed a pharmacological profile that does not correlate with any previously described serotonin receptor subtype. In addition, this receptor exhibits high affinity for a number of tricyclic antipsychotic and antidepressant drugs including clozapine, loxapine, and amitriptyline. In HEK-293 cells stably transfected with this receptor, serotonin elicits a potent stimulation of adenylylcyclase activity. The distinct structural and pharmacological properties of this receptor suggests that it represents a completely novel serotonin receptor subtype, which we propose to designate 5-HT7. Based on its pharmacology and its localization to limbic and cortical regions of the brain, it is likely that this receptor may play a role in several neuropsychiatric disorders that involve serotonergic systems.
Shen
Y
Y
Molecular Neuropharmacology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
Monsma
F J
FJ
Metcalf
M A
MA
Jose
P A
PA
Hamblin
M W
MW
Sibley
D R
DR
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001667:Binding, Competitive; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D003001:Cloning, Molecular / Q000379:methods; D000242:Cyclic AMP / Q000378:metabolism; D015870:Gene Expression; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008238:Lysergic Acid Diethylamide / Q000378:metabolism; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D016133:Polymerase Chain Reaction / Q000379:methods; D011869:Radioligand Assay; D051381:Rats; D011985:Receptors, Serotonin / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D012701:Serotonin / Q000378:metabolism / Q000494:pharmacology; D014162:Transfection
D009838:Oligodeoxyribonucleotides; D011985:Receptors, Serotonin; D011994:Recombinant Proteins; D012701:Serotonin; D008238:Lysergic Acid Diethylamide; D000242:Cyclic AMP