Amino acids in transmembrane domain two influence anesthetic enhancement of serotonin-3A receptor function.
Alcohols and volatile anesthetics affect the function of members of the nicotinic acetylcholine (nACh) superfamily of receptors. Studies on glycine and GABA(A) receptors implicate amino acid residues within transmembrane (TM) regions two and three of these receptors as critical for alcohol and anesthetic enhancement of receptor function. The serotonin-3 (5-HT(3)) receptor is a member of the nicotinic acetylcholine receptor superfamily, sharing sequence and structural homology with the other members. We tested the hypothesis that amino acids of the 5-HT(3) receptor homologous to those shown to affect alcohol and anesthetic potentiation in GABA(A) and glycine receptors also determine the effects of these compounds on the 5-HT(3) receptor. Six 5-HT(3A) mutant cDNAs were generated by site-directed mutagenesis of two amino acids, phenylalanine-269 (14') and lecucine-270 (15') in transmembrane domain two (TM2). When assayed electrophysiologically in Xenopus oocytes, wild-type 5-HT(3) receptors exhibit enhancement of function by enflurane, halothane, isoflurane, chloroform and ethanol, but not by decanol and propofol. Mutations in transmembrane domain two markedly affected alcohol and anesthetic enhancement of 5-HT(3) receptor function. Some mutations had differential effects on the abilities of the isomers enflurane and isoflurane to potentiate 5-HT(3) receptor function.
Lopreato
Gregory F
GF
Section of Neurobiology, Waggoner Center for Alcohol and Addiction Research, Institute for Neuroscience, and the Institute for Cellular and Molecular Biology, University of Texas at Austin, 2500 Speedway, MBB 1.148, Austin, TX 78712, USA.
Banerjee
Paula
P
Mihic
S John
SJ
D000595:Amino Acid Sequence / Q000187:drug effects / Q000235:genetics; D000596:Amino Acids / Q000737:chemistry* / Q000187:drug effects; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D002462:Cell Membrane / Q000737:chemistry* / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D000431:Ethanol / Q000494:pharmacology; D005260:Female; D007930:Leucine / Q000737:chemistry / Q000187:drug effects; D016297:Mutagenesis, Site-Directed; D009154:Mutation / Q000235:genetics; D009865:Oocytes / Q000378:metabolism; D010649:Phenylalanine / Q000737:chemistry / Q000187:drug effects; D017434:Protein Structure, Tertiary / Q000187:drug effects / Q000502:physiology; D044406:Receptors, Serotonin, 5-HT3 / Q000737:chemistry* / Q000187:drug effects / Q000235:genetics; D012701:Serotonin / Q000378:metabolism / Q000494:pharmacology; D014982:Xenopus laevis
D000596:Amino Acids; D018685:Anesthetics, Inhalation; D044406:Receptors, Serotonin, 5-HT3; D012701:Serotonin; D000431:Ethanol; D010649:Phenylalanine; D007930:Leucine