A unique phenotype of 5-HT2C, agonist-induced GTPgamma35S binding, transferable to 5-HT2A and 5-HT2B, upon swapping intracellular regions.
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.
Alberts
Glen L
GL
BiologyII/Neurobiology, Pharmacia, 301 Henrietta Street, Kalamazoo, MI 49007, USA.
Chio
Christopher L
CL
Im
Wha Bin
WB
Slightom
Jerry L
JL
D000818:Animals; D001667:Binding, Competitive; D002460:Cell Line; D003001:Cloning, Molecular; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism*; D006801:Humans; D008024:Ligands; D051379:Mice; D010641:Phenotype; D016133:Polymerase Chain Reaction; D011485:Protein Binding; D011869:Radioligand Assay; D044402:Receptor, Serotonin, 5-HT2A; D044403:Receptor, Serotonin, 5-HT2B; D044405:Receptor, Serotonin, 5-HT2C; D011985:Receptors, Serotonin / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*
D008024:Ligands; D044402:Receptor, Serotonin, 5-HT2A; D044403:Receptor, Serotonin, 5-HT2B; D044405:Receptor, Serotonin, 5-HT2C; D011985:Receptors, Serotonin; D011993:Recombinant Fusion Proteins; D017366:Serotonin Receptor Agonists; D016244:Guanosine 5'-O-(3-Thiotriphosphate)