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

1. The effect of micromolar concentrations of divalent metal cations on ion current activated by 5-hydroxytryptamine (5-HT) was investigated in NCB-20 neuroblastoma cells by the use of the whole-cell, patch-clamp technique. 2. Ion current activated by 5-HT in these cells was mimicked by 5-HT3 receptor agonists, blocked by nanomolar concentrations of selective 5-HT3 receptor antagonists and reversed polarity at approximately 0 mV. These properties indicate that this current is carried primarily if not exclusively by the nonspecific cation channel activated by the 5-HT3 receptor. 3. The Group IIb metal cations Cd2+ and Zn2+ and the Group Ib cation Cu2+ inhibited 5-HT-activated current with inhibition increasing in a concentration-dependent manner over micromolar concentrations of the ions. The order of potency of the ions for inhibiting 5-HT-activated current was Zn2+ (IC50 = 20 microM) greater than or equal to Cu2+ (IC50 = 25 microM) greater than Cd2+ (IC50 = 75 microM) at -50 mV. The other divalent metal cations tested (Ba2+, Co2+, Mg2+, Mn2+, and Ni2+) produced little or no inhibition of 5-HT-activated current at concentrations up to 200 microM. 4. Inhibition of 5-HT-activated current by Cd2+ and Zn2+ was dependent on membrane potential with the Kd increasing e-fold per 72 and 52 mV, respectively. Inhibition by Cu2+ was much less voltage dependent with the Kd increasing e-fold per 233 mV. 5. Inhibition by all three cations decreased with increasing concentration of agonist over a range of 5-HT concentrations from 1 to 10 microM.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Inhibition of 5-HT3 receptor-mediated ion current by divalent metal cations in NCB-20 neuroblastoma cells. 172 46

1. The pharmacological and biophysical properties of a recombinant 5-HT3 receptor have been studied by use of patch-clamp techniques applied to HEK 293 cells stably transfected with the murine 5-HT3 R-A cDNA. 2. At a holding potential of -60 mV, 77% of cells investigated responded to ionophoretically applied 5-HT with an inward current. Such currents were unaffected by methysergide (1 microM), or ketanserin (1 microM), but were antagonized in a concentration-dependent and reversible manner by the selective 5-HT3 receptor antagonist, ondansetron (IC50 = 440 pM) and the non-selective antagonists (+)-tubocurarine (IC50 = 1.8 nM) and metoclopramide (IC50 50 nM). 3. The 5-HT-induced current reversed in sign (E5-HT) at approximately -2mV and exhibited inward rectification. The influence of extra- and intracellular ion substitutions upon E5-HT indicates the 5-HT-evoked current to be mainly mediated by a mixed monovalent cation conductance. 4. Calcium and magnesium (0.1-10 nM) produced a concentration-dependent, voltage-independent, inhibition of the 5-HT-induced response. Zinc (0.3-300 microM) exerted a biphasic effect with low concentrations enhancing, and high concentrations depressing, the 5-HT-evoked current. 5. Fluctuation analysis of inward currents evoked by a low (1 microM) concentration of 5-HT suggests the current to be mediated by the opening of channels with a conductance of 420 fS. 6. The pharmacological and biophysical properties of the 5-HT3 R-A are similar to those previously described for 5-HT3 receptors native to murine neuroblastoma cell lines, with the exception that the function of the recombinant receptor was enhanced by low concentrations of zinc. This observation suggests that the properties of the native receptor are not completely represented by the 5-HT3 R-A subunit alone.
 ...
PMID:An electrophysiological investigation of the properties of a murine recombinant 5-HT3 receptor stably expressed in HEK 293 cells. 762 Jul 11

In the presence of substance P (SP; 10 microM), serotonin (5-HT; 1 microM) triggered a cation permeability in cells of the hybridoma (mouse neuroblastoma x rat glioma) clone NG 108-15 that could be assessed by measuring the cell capacity to accumulate [14C]guanidinium for 10-15 min at 37 degrees C. In addition to 5-HT (EC50 0.33 microM), the potent 5-HT3 receptor agonists 2-methyl-serotonin, phenylbiguanide, and m-chlorophenylbiguanide, and quipazine, markedly increased [14C]guanidinium uptake in NG 108-15 cells exposed to 10 microM SP. In contrast, 5-HT3 receptor antagonists prevented the effect of 5-HT. The correlation (r = 0.97) between the potencies of 16 different ligands to mimic or prevent the effects of 5-HT on [14C]guanidinium uptake, on the one hand, and to displace [3H]zacopride specifically bound to 5-HT3 receptors on NG 108-15 cells, on the other hand, clearly demonstrated that [14C]guanidinium uptake was directly controlled by 5-HT3 receptors. Various compounds such as inorganic cations (La3+, Mn2+, Ba2+, Ni2+, and Zn2+), D-tubocurarine, and memantine inhibited [14C]guanidinium uptake in NG 108-15 cells exposed to 5-HT and SP, as expected from their noncompetitive antagonistic properties at 5-HT3 receptors. However, ethanol (100 nM), which has been reported to potentiate the electrophysiological response to 5-HT3 receptor stimulation, prevented the effects of 5-HT plus SP on [14C]guanidinium uptake. The cooperative effect of SP on this 5-HT3-evoked response resulted neither from an interaction of the peptide with the 5-HT3 receptor binding site nor from a possible direct activation of G proteins in NG 108-15 cells. Among SP derivatives, [D-Pro9]SP, a compound inactive at the various neurokinin receptor classes, was the most potent to mimic the stimulatory effect of SP on [14C]guanidinium uptake in NG 108-15 cells exposed to 5-HT. Although the cellular mechanisms involved deserve further investigations, the 5-HT-evoked [14C]guanidinium uptake appears to be a rapid and reliable response for assessing the functional state of 5-HT3 receptors in NG 108-15 cells.
 ...
PMID:Characteristics of [14C]guanidinium accumulation in NG 108-15 cells exposed to serotonin 5-HT3 receptor ligands and substance P. 768 66

We have examined the ability of divalent cations to inhibit 3H-GR 65630 binding to 5-HT3 receptor recognition sites in rat brain cortical membranes. Among the divalent metal cations tested, Cd2+, Zn2+ and Cu2+ inhibited the specific 3H-GR 65630 binding activity to 5-HT3 receptors at a concentration of 0.1-1 mM. The other divalent metal cations tested (i.e. Co2+, Ni2+, Ba2+, Ca2+, Mg2+ and Mn2+) produced no inhibition of the specific 3H-GR 65630 binding. Cd2+, Zn2+ and Cu2+ did not change the Bmax value of the binding activity, but significantly increased the Kd value. It was suggested that these cations inhibited the binding activity by reducing affinity of the 5-HT3 receptor for the antagonist, resulting in apparent inhibition of the binding activity. As to the binding association rate, Cd2+, Cu2+ and Zn2+ were found to have an inhibitory effect. The binding dissociation rate, however, was shown to be decreased by Cu2+ but not by Cd2+ and Zn2+. Furthermore, the Zn(2+)-induced inhibition of 3H-GR 65630 binding was suggested to be antagonized by both concanavalin A and wheatgerm agglutinin. The Cu(2+)-induced inhibition, however, was not influenced by these lectins, indicating that Cu2+ has a different lectin sensitivity for its inhibitory effect. The different mechanism of action between Cu2+ and Zn2+ was suggested in their inhibitory effect on the specific 3H-GR 65630 binding activity.
 ...
PMID:Differential effects of divalent cations on specific 3H-GR 65630 binding to 5-HT3 receptors in rat cortical membranes. 802 34

The effects of several metals on the serotonin receptor-channel complex were studied using mouse neuroblastoma N1E-115 cells which are known to be endowed with the 5-HT3 subclass of the receptor. The whole-cell patch clamp technique was used to record currents induced by serotonin at a concentration of 3 microM which was equivalent to the apparent dissociation constant. Methylmercury and mercuric chloride suppressed serotonin-induced currents irreversibly, with a 50% suppression being observed at concentrations of 3 microM and 2 microM, respectively. Lead and zinc suppressed the current with IC50S of 80 microM and 50 microM, respectively, and the effects of both metals were reversible after washing with metal-free solution. Lanthanum also suppressed the current with an IC50 of 10 microM, and the effect was partially reversible. Cadmium and cobalt augmented serotonin-induced currents slightly but consistently at a concentration of 100 microM, and the effect was reversible. Aluminum at 100 microM, had no effect on serotonin-induced currents. It was concluded that the 5-HT3 receptor is endowed with a unique property with respect to the actions of metals which is not shared by some other ligand-gated and voltage-gated ion channels.
 ...
PMID:Modulation of serotonin-induced currents by metals in mouse neuroblastoma cells. 887 Sep 59

Considerable controversy surrounds the location of the closed channel gate in members of the Cys-loop receptor family of neurotransmitter-gated ion channels that includes the GABAA, glycine, acetylcholine, and 5-HT3 receptors. Cysteine-accessibility studies concluded that the gate is near the cytoplasmic end of the channel in acetylcholine and GABAA receptors but in the middle of the 5-HT3A receptor channel. Zn2+ accessibility studies in a chimeric 5-HT3-ACh receptor suggested the gate is near the channel's cytoplasmic end. In the 4-A resolution structure of the acetylcholine receptor closed state determined by cryoelectron microscopy, the narrowest region, inferred to be the gate, is in the channel's midsection from 9' to 14' but the M1-M2 loop residues at the channel's cytoplasmic end were not resolved in that structure. We used blocker trapping experiments with picrotoxin, a GABAA receptor open channel blocker, to determine whether a gate exists at a position more extracellular than the picrotoxin binding site, which is in the vicinity of alpha1Val257 (2') near the channel's cytoplasmic end. We show that picrotoxin can be trapped in the channel after removal of GABA. By using the state-dependent accessibility of engineered cysteines as reporters for the channel's structural state we infer that after GABA washout, with picrotoxin trapped in the channel, the channel appears to be in the closed state. We infer that a gate exists between the picrotoxin binding site and the channel's extracellular end, consistent with a closed channel gate in the middle of the channel. Given the homology with acetylcholine and 5-HT3 receptors there is probably a similar gate in those channels as well. This does not preclude the existence of an additional gate at a more cytoplasmic location.
 ...
PMID:The location of a closed channel gate in the GABAA receptor channel. 1722 18

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.
 ...
PMID:Effects of a mutation in the TM2-TM3 linker region of the glycine receptor alpha1 subunit on gating and allosteric modulation. 1743 60