Cloning and pharmacological characterization of a novel human 5- hydroxytryptamine1D receptor subtype

SA Veldman and MJ Bienkowski

Department of Cell Biology, Upjohn Laboratories, Kalamazoo, Michigan 49007.

The canine RDC4 gene was used to isolate two distinct human serotonin receptor genes. The receptor encoded by clone RH-6 was the species homolog of RDC4 and was identical to a human serotonin 5- hydroxytryptamine1D (5-HT1D) receptor that was recently reported [Mol. Pharmacol. 40:143-148 (1991)]. The receptor encoded by RH-2 was a novel 5-HT receptor that was 61% identical to RH-6 and showed the greatest homology with the rat 5-HT1B receptor sequence (94%). The RH-2 gene contained an intronless, 1170-base pair, open reading frame that encoded a 390-amino acid protein that contained all of the hallmarks of a guanine nucleotide-binding protein-linked receptor. Heterologous expression of the RH-2 gene in Chinese hamster ovary cells led to the appearance of high affinity binding sites for 5-HT (Kd = 2.6 nM, Bmax = 2.9 pmol/mg of membrane protein), and the receptor expressed in Chinese hamster ovary cells was coupled to inhibition of adenylyl cyclase. Competition binding experiments using compounds that are selective for various 5-HT receptor subtypes showed the highest correlation with a 5- HT1D-like receptor (r = 0.89) and a low correlation with 5-HT1B-like receptors. Examples of the 5-HT1D-like pharmacology displayed by RH-2 include high affinity for the 5-HT1D-selective compound sumatriptan (Ki = 9.4 nM) and for the alpha 2-adrenergic receptor antagonist rauwolscine (Ki = 47 nM). Therefore, despite the close genetic relationship between RH-2 and the rat 5-HT1B receptor, our results indicate that the receptor encoded by RH-2 2 is best classified as a human 5-HT1D receptor subtype and defines a second member of the human 5-HT1D receptor family.

Volume 42, Issue 3, pp. 439-444, 09/01/1992
Copyright © 1992 by American Society for Pharmacology and Experimental Therapeutics