Abstract
RDC4 is a guanine nucleotide-binding protein-coupled receptor clone originally isolated from a canine thyroid cDNA library by Libert and colleagues [Science (Washington D. C.) 244:569-572 (1989)]. We have isolated the corresponding genomic clone for RDC4, have expressed this clone in murine LM (tk-) fibroblasts, and have determined that it encodes a serotonin 5-hydroxytryptamine1D (5-HT1D) receptor. RDC4 is an intronless gene encoding a protein of 377 amino acids, which exhibits greatest sequence identity (43%) to the 5-HT1A receptor and lower overall homology to other serotonergic and catecholaminergic receptors. Membranes prepared from murine LM (tk-) fibroblasts stably transfected with this clone were shown to bind [3H]5-HT in a saturable manner and displayed an apparently homogeneous population of high affinity (Kd = 3.6 nM, Bmax = 275 fmol/mg of protein) [3H]5-HT binding sites. High affinity [3H] 5-HT binding was unchanged using assay conditions [1 microM (+/- )-pindolol and 1 microM (R)-(+/- )-SCH 23390) to pharmacologically mask 5-HT1A, 5-HT1B, and 5-HT1C receptors. Serotonergic ligands displaced specific [3H]5-HT binding with a rank order of potency expected of a 5-HT1D receptor subtype, 5-carboxyamidotryptamine greater than 5-HT greater than yohimbine greater than 8-hydroxy-2-(di-n-propylamino)tetralin greater than ketanserin = spiperone greater than zacopride. Further, transfected cells responded to addition of 5-HT by decreasing the level of forskolin-stimulated cAMP accumulation. These data indicate that the gene RDC4 encodes a functional 5-HT1D receptor.
MolPharm articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|