Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P46098 (5-HT3 receptor)
 2,290 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The 5-HT3 receptor is a transmitter-gated ion channel of the Cys-loop superfamily. Uniquely, 5-HT3 receptor subunits (5-HT3A and 5-HT3B) possess a positively charged lysine residue within the putative channel lining M2 domain (4' position). Using whole cell recording techniques, we examined the role of this residue in receptor function using wild-type (WT) and mutant 5-HT3A receptor subunits of murine origin transiently expressed in human embryonic kidney (HEK 293) cells. WT 5-HT3A receptors mediated rapidly activating currents in response to 5-HT (10-90 % rise time, 103 ms; EC50, 2.34 microM; Hill coefficient, nH, 2.87). The currents rectified inwardly, reversed in sign at a potential of -9 mV and desensitized in the continuous presence of agonist (half-time of desensitization, t(1/2), 2.13 s). 5-HT3A receptor subunits in which the 4'lysine was mutated to arginine, glutamine, serine or glycine formed functional receptors. 5-HT EC50 values were approximately 2-fold lower than for WT 5-HT3A receptors, but Hill coefficients, kinetics of current activation, rectification, and reversal potentials were unaltered. Each of the mutants desensitized more slowly than the WT 5-HT3A receptor, with the arginine and glycine mutations exhibiting the greatest effect (5-fold reduction). The rank order of effect was arginine > glycine > serine > glutamine. The single-channel conductance of the WT 5-HT3A receptor, as assessed by fluctuation analysis of macroscopic currents, was 390 fS. A similar value was obtained for the 4'lysine mutant receptors. Thus it appears unlikely that 4'lysine is exposed to the channel lumen. Mutation of residues immediately adjacent to 4'lysine to glutamate or lysine resulted in lack of receptor expression or function. We conclude that 4'lysine does not form part of the channel lining, but may play an important role in 5-HT3 receptor desensitization.
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PMID:The 4'lysine in the putative channel lining domain affects desensitization but not the single-channel conductance of recombinant homomeric 5-HT3A receptors. 1063 97

In this study of the amino acid nutrition of a marsupial we tested three hypotheses: (a) that brushtail possums eat less when diets contain excesses or deficiencies in essential amino acids, (b) that brushtail possums choose diets that do not contain amino acid excesses, and (c) that amino acid consumption is mediated partly by the 5HT3 receptor. Possums ate less when 0.2-1.0% methionine (wet matter) was added to the diet, but similar concentrations of lysine and threonine had little effect. However, when given a choice, possums always selected the basal ration over one with added lysine, methionine or threonine at concentrations between 0.05% and 0.9%. In contrast to the experiments with excess amino acids, possums did not eat less of a diet almost devoid of an essential amino acid. Instead, the possums ate less when their diets contained synthetic amino acids rather than similar amounts and proportions of amino acids as casein. Contrary to the third hypothesis, the 5HT3 receptor antagonist, ondansetron, did not affect feeding by possums given a diet containing 0.8% methionine, suggesting that post-ingestive feedback, via the 5HT3 receptor, does not regulate amino acid intake when diets contain amino acid excesses.
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PMID:The effect of excesses and deficiencies in amino acids on the feeding behaviour of the common brushtail possum (Trichosurus vulpecula). 1235 29

Alcohols and volatile anesthetics modulate the function of cys-loop ligand-gated ion channels, binding to a putative site between transmembrane domains two and three. The extracellular linker between these two domains is important in the transduction of the gating signal from the glycine binding site to the channel gate. Although the anesthetic binding site is proposed to be in the same region throughout the cys-loop receptor family, the modulatory effects of these compounds depend on the receptor. A sequence comparison revealed an extra proline in the TM2-TM3 loop of the 5-HT3A receptor (5-HT3AR) that is not found in the glycine receptor (GlyR). We hypothesized that this proline residue could affect the size and orientation of the putative alcohol and anesthetic binding pocket and perhaps explain some of the differences in alcohol and anesthetic effects seen in this family of receptors. A lysine to proline mutation was introduced into the TM2-TM3 linker region at position 281 (K281P) of the alpha1 GlyR. Mutation at this residue did not affect thiol binding to residues in TM2 or TM3 and it does not appear that residue 281 constitutes part of the alcohol binding site. The K281P receptors displayed constitutive activity in the absence of glycine, and unlike wild-type receptors, this channel opening was antagonized by application of either volatile anesthetics or another GlyR modulator, zinc. Our data suggest that the TM2-TM3 extracellular loop plays a role in the transduction of signals generated by allosteric modulators in addition to gating signals that follow glycine binding.
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PMID:Effects of a mutation in the TM2-TM3 linker region of the glycine receptor alpha1 subunit on gating and allosteric modulation. 1743 60