Identification of a domain affecting agonist potency of meta-chlorophenylbiguanide in 5-HT3 receptors.
The pharmacological properties of rat and human 5-HT3 receptors expressed in Xenopus oocytes were assessed using a two-electrode voltage clamp technique. Meta-chlorophenylbiguanide (mCPBG), a 5-HT3 receptor-selective agonist, elicited typical current responses in both rat and human 5-HT3 receptor-expressing oocytes. However, the EC50 value for rat 5-HT3 receptors was 13-fold lower than for human 5-HT3 receptors. Using several chimeric human-rat 5-HT3 receptors, we identified a potential domain responsible for this difference in mCPBG-response. The domain is in the N-terminal extracellular region adjacent to the first transmembrane domain of rat 5-HT3 receptors and includes a rat-specific seven amino acid sequence (Phe197, Thr198, Lys199, Gln201, Ile205, Thr207 and Ser210). Replacement of corresponding amino acids in human 5-HT3 receptors by rat receptor residues increased the potency of mCPBG on human receptors indicating these amino acids play an important role in the pharmacological response to mCPBG.
Mochizuki
S
S
Molecular Medicine Laboratories, Institute for Drug Discovery Research, Yamanouchi Pharmaceutical, Tsukuba, Ibaraki, Japan. mochizuk@yamanouchi.co.jp
Miyake
A
A
Furuichi
K
K
D000595:Amino Acid Sequence; D000818:Animals; D001645:Biguanides / Q000378:metabolism / Q000494:pharmacology*; D001665:Binding Sites; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D015870:Gene Expression; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D008969:Molecular Sequence Data; D009154:Mutation; D009865:Oocytes; D018408:Patch-Clamp Techniques; D051381:Rats; D011985:Receptors, Serotonin / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D044406:Receptors, Serotonin, 5-HT3; D011993:Recombinant Fusion Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D017366:Serotonin Receptor Agonists / Q000378:metabolism / Q000494:pharmacology*; D014981:Xenopus
D001645:Biguanides; D011985:Receptors, Serotonin; D044406:Receptors, Serotonin, 5-HT3; D011993:Recombinant Fusion Proteins; D017366:Serotonin Receptor Agonists; C065734:1-(3-chlorophenyl)biguanide