| Amino acid residues involved in agonist binding and its linking to channel gating, proximal to transmembrane domain of 5-HT3A receptor for halothane modulation. |
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Mi Kyeong Kim, Kyeong Tae Min, Bon Nyeo Koo |
1Department of Anesthesiology and Pain Medicine, Kyung Hee University College of Medicine, Seoul, Korea.
2Department of Anesthesiology and Pain Medicine, Research Institute of Anesthesia and Pain, Yonsei University College of Medicine, Seoul, Korea. koobn@yuhs.ac |
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| Abstract |
BACKGROUND
The 5-hydroxytryptamine type 3 (5-HT3) receptor is a member of the Cys-loop superfamily of ligand-gated ion channels (LGICs) and modulated by pharmacologic relevant concentrations of volatile anesthetics or n-alcohols like most receptors of LGICs. The goal of this study was to reveal whether the site-directed single mutations of E-106, F-107 and R-222 in 5-HT3 receptor may affect the anesthetic modulation of halothane known as positive modulator.
METHODS
The wild-type and mutant receptors, E106D, F107Y, R222F, R222V, were expressed in Xenopus Laevis oocytes and receptor function was assessed using two electrode voltage clamp techniques.
RESULTS
E106D, F107Y, R222F, R222V mutant 5-HT3A receptors were functionally expressed. F107Y mutant 5-HT3A receptors displayed decreased sensitivity to 5-HT compared to the wild type 5-HT3A receptor (P < 0.05). Halothane showed positive modulation in both wild and F107Y mutant 5-HT3A receptors but F107Y mutant 5-HT3 receptor showed greater enhancing modulation comparing to wild-type receptor. Meanwhile, R222F and R222V mutant 5-HT3 receptor lost positive modulation with 1 and 2 MAC of halothane. Most interestingly, positive modulation by halothane was converted into negative modulation in E106D mutant 5-HT3A receptor.
CONCLUSIONS
The present study implicate the amino acid residues known for agonist binding and linking agonist binding to channel gating might also have important role for anesthetic modulation in 5-HT3A receptor. |
| Key Words:
Electrophysiology; 5-HT3A receptor; 5-HT; Halothane; Site-directed single mutation; Xenopus Laevis oocytes |
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