Molecular cloning of a mammalian serotonin receptor that activates adenylate cyclase.
Serotonin modulates a wide range of physiological functions by activating multiple receptors, which are coupled to various effector systems. Using a strategy based on amino acid sequence homology between 5-hydroxytryptamine (5-HT) receptors, we have isolated from a mouse brain library a cDNA encoding a new 5-HT receptor, 5-HTx, that activates adenylate cyclase. Amino acid sequence comparisons revealed that the 5-HTx receptor was a distant relative of previously cloned 5-HT receptors, with the highest percentage of homology (42%) being with the 5-HTdro1 receptor, a Drosophila 5-HT receptor positively coupled to adenylate cyclase. In COS-7 cells transiently expressing the 5-HTx receptor, 5-HT induced an increase in cAMP levels that was dose dependent and saturable (EC50 = 45 nM). Agonists displayed the following rank order of potencies: 5-carboxamidotryptamine > 5-methoxytryptamine > 5-HT > RU 24969 > 8-hydroxy-2-(di-n-propylamino)tetralin. The most efficient antagonists in inhibiting the stimulatory effect of 5-HT were methysergide, methiothepin, mesulergine, metergoline, clozapine, ergotamine, and (+)-butaclamol. Membranes of COS-7 cells expressing the 5-HTx receptor displayed a single saturable binding site for [3H]5-HT. The order of potencies of various drugs in displacing [3H]5-HT binding was similar to the order obtained in cAMP experiments. The pharmacological profile of this receptor does not correspond to the profile of any of the classic 5-HT receptor subtypes. Expression of 5-HTx mRNA was highest in brainstem and lower in forebrain, cerebellum, intestine, and heart. The 5-HTx receptor might therefore correspond to 5-HT1-like receptors that have been shown to induce relaxation in porcine vena cava and guinea pig ileum as well as tachycardia in cat heart. The high affinity of the 5-HTx receptor for neuroleptic agents such as (+)-butaclamol and clozapine suggests also that this receptor might play a role in certain neuropsychiatric disorders.
Laboratoire de Génétique Moléculaire des Eucaryotes du CNRS, U/184 de l'INSERM, Département de Neurobiologie, Faculté de Médecine, Strasbourg, France.
J L
JL
Plassat
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Amlaiky
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R
Hen
D000262:Adenylyl Cyclases / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000378:metabolism; D003001:Cloning, Molecular; D000242:Cyclic AMP / Q000378:metabolism; D004247:DNA / Q000737:chemistry / Q000235:genetics; D004330:Drosophila; D004789:Enzyme Activation; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009206:Myocardium / Q000378:metabolism; D011985:Receptors, Serotonin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology
D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D004247:DNA; D000242:Cyclic AMP; D000262:Adenylyl Cyclases