A unique phenotype of 5-HT2C, agonist-induced GTPgamma35S binding, transferable to 5-HT2A and 5-HT2B, upon swapping intracellular regions

• Published in: British journal of pharmacology Vol. 138; no. 3; pp. 427 - 434
• Main Authors: Alberts, Glen L, Chio, Christopher L, Im, Wha Bin, Slightom, Jerry L
• Format: Journal Article
• Language: English
• Published: England 01.02.2003
• Subjects: Animals; Binding, Competitive; Cell Line; Cloning, Molecular; Guanosine 5'-O-(3-Thiotriphosphate) - metabolism; Humans; Ligands; Mice; Phenotype; Polymerase Chain Reaction; Protein Binding; Radioligand Assay; Receptor, Serotonin, 5-HT2A; Receptor, Serotonin, 5-HT2B; Receptor, Serotonin, 5-HT2C; Receptors, Serotonin - drug effects; Receptors, Serotonin - genetics; Receptors, Serotonin - metabolism; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; Serotonin Receptor Agonists - pharmacology
• ISSN: 0007-1188

1 The human 5-HT(2C) receptor, when expressed heterologously in various mammalian cell lines (HEK293, SH-EP and NIH-3T3) at various receptor densities (6 to 45 pmol mg(-1) protein), mediates robust agonist-induced GTPgamma(35)S binding from coupling to G(i) subtypes of G proteins, in addition to G(q/11). Such a phenotype, however, was not seen with the human 5-HT(2A) and 5-HT(2B) receptors, indicating their common pathway with 5-HT(2C) limited to G(q/11), not including G(i). 2 Because intracellular regions are largely responsible for signalling pathways, we prepared the chimeras of the 5-HT(2A) and 5-HT(2B) receptors where the second and third intracellular loops, and the C-terminal region were replaced with the 5-HT(2C) counterparts. 3 The chimeras showed robust agonist-induced GTPgamma(35)S binding. Relative intrinsic efficacies of agonists from the GTPgamma(35)S binding were nearly identical to the reported values for their parent receptors as measured with Ca(2+) or [(3)H]-inositol phosphate accumulation. Also the chimeras displayed the same ligand-binding properties as the parent receptors. 4 We conclude that the phenotype of agonist-induced GTPgamma(35)S binding is unique to 5-HT(2C) among the 5-HT(2) receptor family, and is transferable to 5-HT(2A) and 5-HT(2B), upon swapping intracellular sequences, without altering their receptor pharmacology.