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)

We have used single-cell imaging of fura-2-loaded cells to examine the Ca2+ signals evoked by activation of 5-hydroxytryptamine type 3 (5-HT3) receptors in undifferentiated N1E-115 neuroblastoma cells and in human embryonic kidney (HEK) 293 cells transfected with either of the two cloned 5-HT3 receptor subunits. The selective 5-HT3 receptor agonist 1-(m-chlorophenyl)-biguanide (mCPBG) caused a concentration-dependent increase in the cytoplasmic Ca2+ concentration ([Ca2+]i) in N1E-115 cells and in HEK 293 cells transfected with either the 5-HT3 A subunit or the 5-HT3 As subunit. In each case, the [Ca2+]i rise was steeply dependent on the mCPBG concentration (nH = 2-4) and abolished by removal of extracellular Ca2+ or addition of ondansetron. Pretreatment of N1E-115 cells with thapsigargin, caffeine, and ryanodine to deplete intracellular Ca2+ stores had no effect on the mCPBG-evoked Ca2+ signals, indicating that they result entirely from stimulated Ca2+ entry. The steep concentration-effect curves therefore are not a consequence of amplification of Ca2+ influx by Ca(2+)-induced Ca2+ release from intracellular stores and probably reflect cooperative activation of 5-HT3 receptors by mCPBG. Depolarization of transfected HEK 293 cells with medium containing increased K+ concentrations invariably failed to evoke an increase in [Ca2+]i, confirming the absence of voltage-gated Ca2+ channels and indicating that the mCPBG-evoked rise in [Ca2+]i results from Ca2+ permeation of 5-HT3 receptors. However, in N1E-115 cells and transfected HEK 293 cells, both extracellular Na+ and K+ substantially inhibited the Ca2+ influx evoked by activation of 5-HT3 receptors, possibly by inhibition of agonist binding or by competition with Ca2+ for permeation of the channel. We conclude that 5-HT3 receptors are Ca2+ permeant, that the Ca2+ influx is sufficient to generate a significant rise in [Ca2+]i, and that, because the A and As subunits behave similarly, conflicting electrophysiological analyses of Ca2+ currents cannot be explained by differences between these two subunits.
Mol Pharmacol 1994 Dec
PMID:Ca2+ permeability of cloned and native 5-hydroxytryptamine type 3 receptors. 780 32

The structure of the mouse 5-HT3 receptor gene, 5-HT3R-A, is most similar to nicotinic acetylcholine receptor (nAChR) genes, in particular to the gene encoding the neuronal nAChR subunit alpha 7. These genes share among other things the location of three adjacent introns, suggesting that 5-HT3R-A and nAChR genes arose from a common precursor gene. The alternative use of two adjacent splice acceptor sites in intron 8 creates, in addition to the original 5-HT3R-A cDNA (5-HT3R-AL), a shorter isoform (5-HT3R-AS) which lacks six codons in the segment that translates into the major intracellular domain. This splice consensus sequence is not found in human genomic DNA. In mouse, we demonstrate by RNAse protection assay that 5-HT3R-AS mRNA is approximately 5 times more abundant than 5-HT3R-AL mRNA in both neuroblastoma cell lines and neuronal tissues. We used the Semliki Forest virus expression system for electrophysiological characterization of 5-HT3R-AS and 5-HT3R-AL in mammalian cells. No differences in electrophysiological characteristics, such as voltage dependence, desensitization kinetics, or unitary conductance were found between homomeric 5-HT3R-AS and 5-HT3R-AL receptors. Their properties are very similar to those of 5-HT3 receptors in mouse neuroblastoma cell lines.
Brain Res Mol Brain Res 1994 Oct
PMID:Organization of the mouse 5-HT3 receptor gene and functional expression of two splice variants. 785 52

The effects of 24 biguanide and four guanidine derivatives on 5-hydroxytryptamine (5-HT)3 receptors in N1E-115 neuroblastoma cells were examined using radioligand binding and whole-cell voltage-clamp techniques. Displacement of the selective 5-HT3 receptor antagonist [3H]BRL 43694 by phenylbiguanide (PBG) derivatives revealed Ki values ranging from 3.4 x 10(-4) to 4.4 x 10(-10) M. The rank order of potency of agonists was 2,3,5-trichloro-PBG > 2,3-dichloro-PBG = 2,5-dichloro-PBG = 3,5-dichloro-PBG > 3,4-dichloro-PBG = 3-chloro-PBG > 2-chloro-PBG = 4-chloro-PBG = 2-methyl-PBG = 2,4-difluoro-PBG > PBG = 2-trifluoro-5-chloro-PBG > 4-fluoro-PBG = 3-trifluoromethyl-PBG > 4-nitro-PBG = 1,5-bis-4-chloro-PBG = 3,5-ditrifluoromethyl-PBG > 4-ethoxy-PBG >> 4-sulfonic acid-PBG. All of the benzylbiguanides and indanylbiguanide were inactive on [3H]BRL 43694 binding or displaced it only weakly. The four guanidine derivatives were quite inactive. In the PBG series, all antagonist competition curves were steep (pseudo-Hill coefficients ranging from 1.05 to 1.58), monophasic, and best fit with a one-site model. Among PBG derivatives, the chlorinated compounds exhibited a good degree of selectivity for 5-HT3 receptors versus other 5-HT receptor subtypes and other neurotransmitter binding sites. Electrophysiological studies showed that the PBG derivatives tested produced rapid inward currents, at a holding potential of -65 mV, that showed rapid desensitization. The current induced by the 2,3,5-trichloro-PBG derivative was inhibited by the specific 5-HT3 receptor antagonist ICS 205-930 but was unaffected by the 5-HT2 receptor antagonist ketanserin. Analysis of concentration-response curves for the PBG derivatives gave EC50 values ranging from 2.2 x 10(-5) to 2.7 x 10(-8) M and Hill slopes ranging from 1.02 to 2.10. The rank order of potency was similar to that obtained from the binding data, and a good correlation was found between Ki and EC50 values. It is concluded that the triple-chloro substitution yielded a compound that is 30-fold more potent than 3-chloro-PBG and approximately 10-fold more potent than dichloro-PBG derivatives, making 2,3,5-trichloro-PBG the most potent 5-HT3 agonist described thus far.
Mol Pharmacol 1994 Oct
PMID:Biguanide derivatives: agonist pharmacology at 5-hydroxytryptamine type 3 receptors in vitro. 796 53

Serotonin (5-hydroxytryptamine; 5-HT) has recently been shown to induce collagenase production in myometrial smooth muscle cells (Jeffrey et al. (1991) J. Cell. Physiol. 146, 399-406) by activating transcription of the collagenase gene (Wilcox et al. (1992) J. Biol. Chem. 267, 20752-20757) following an interaction with the 5-HT2 receptor (Rydelek-Fitzgerald et al. (1993) Mol. Cell. Endocrinol. 91, 67-74). These studies were performed to investigate factors controlling the regulation of 5-HT2 receptors in these cells. Northern blot analysis indicates that serotonin increases levels of 5-HT2 receptor mRNA in cells by approximately 4-fold. Detectable increases in mRNA levels occur within 2 h after administration of serotonin with maximal levels occurring after 12 h. The 5-HT2 receptor antagonists, ketanserin and spiperone, inhibit the serotonin-mediated increase in receptor mRNA. Selective 5-HT2 receptor agonists ((+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane HCl (DOI) and quipazine) mimic the effect of serotonin, whereas 5-HT1 and 5-HT3 receptor agonists ((+/-)-8-hydroxydipropylaminotetralin (8-OH-DPAT), 1-(3-chlorophenyl)piperazine dihydrochloride (mCPP), m-phenylbiguanide) have no effect. These data demonstrate that serotonin induces an increase in 5-HT2 receptor mRNA by interacting with the 5-HT2 receptor itself. Nuclear run-on analysis revealed that serotonin increases the initiation of 5-HT2 receptor mRNA synthesis. Moreover, the protein synthesis inhibitor, cycloheximide, prevents the induction of the mRNA for the receptor, demonstrating that serotonin-dependent increases in 5-HT2 receptor transcription require de novo protein synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Endocrinol 1993 Apr
PMID:Serotonin-mediated 5-HT2 receptor gene regulation in rat myometrial smooth muscle cells. 831 29

Recent studies have shown that serotonin (5-hydroxytryptamine; 5-HT) is required for the induction of interstitial collagenase in cultured rat and human myometrial smooth muscle cells. The present study was performed to determine which serotonin receptor subtype mediates the induction of collagenase in these cells. [125I]DOI ((+/- )-1-(2,5-dimethoxy-4-[125I]iodophenyl)-2-aminopropane), a 5-HT2 receptor agonist radioligand, bound specifically to sites in myometrial cell membranes, and exhibited binding characteristics essentially identical to those observed with brain 5-HT2 receptors. Radioligands selective for other serotonin receptor subtypes (5-HT1 and 5-HT3) failed to yield detectable binding. Northern blot analysis demonstrated the presence of 5-HT2 mRNA in the uterine smooth muscle cell cultures, whereas transcripts for 5-HT1A and 5-HT1C receptors were not detectable. Moreover, RT-PCR indicated that 5-HT2 receptor mRNA is present in freshly isolated uterine tissue as well. Selective antagonists of the 5-HT2 receptor, ketanserin and spiperone, displayed concentration-dependent inhibition of serotonin-mediated collagenase induction in the myometrial cultures. These antagonists yielded IC50 values of 4.7 nM and 2.7 nM respectively, characteristic of values expected from a 5-HT2 receptor-mediated response. In addition, a number of selective 5-HT2 receptor agonists (quipazine, alpha-methyl-serotonin, DOI) mimicked the ability of serotonin to induce collagenase production, whereas compounds selective for 5-HT1 and 5-HT3 receptor subtypes had little effect.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Endocrinol 1993 Feb
PMID:Serotonin-dependent collagenase induction in rat myometrial smooth muscle cells: mediation by the 5-HT2 receptor. 847 55

In species which vomit, elevated intestinal serotonin (5-hydroxytryptamine, 5-HT) may stimulate abdominal vagal afferent fibers, which in turn evoke the vomiting reflex. The release of 5-HT from intestinal enterochromaffin (EC) cells is regulated by polymodal mechanisms. The object of this study was to evaluate the involvement of 5-HT autoreceptors in the regulation of 5-HT release from the small intestine. Functional studies were carried out using 5-HT3 receptor agonist and antagonists, and 5-HT4 receptor agonist. Ferret and rat ileal tissue were isolated and 5-HT released into the bathing solution was determined using HPLC with an electrochemical detector (ECD). We previously reported that cisplatin produced a significant increase in cumulative 5-HT release and that ondansetron, a selective 5-HT3 receptor antagonist, did not alter the 5-HT release from the ferret ileum. In this study, a selective 5-HT3 agonist, 2-methyl-5-HT, induced a dose-dependent increase of 5-HT from the rat ileum. This release of 5-HT was significantly reduced by granisetron, a selective 5-HT3 receptor antagonist. Furthermore, a selective 5-HT4 receptor agonist, 5-methoxytryptamine induced a concentration-dependent increase of 5-HT in the rat ileum. These results suggest that both 5-HT3 and 5-HT4 receptors may be involved in intestinal 5-HT release.
Res Commun Mol Pathol Pharmacol 1995 Aug
PMID:Chemical modulation of 5-HT3 and 5-HT4 receptors affects the release of 5-hydroxytryptamine from the ferret and rat intestine. 855 68

A human 5-hydroxytryptamine receptor type 3AS (5-HT3R-AS) subunit has been cloned from an amygdala cDNA library. We report the nucleotide and predicted amino acid sequence of the human subunit, which possesses 85% and 84% amino acid sequence identity with mouse and rat 5-HT3R-AS subunits, respectively. Acting on Xenopus laevis oocytes injected with RNA transcripts of the clone, 5-HT and selective 5-HT3 receptor agonists elicited inwardly directed current responses that displayed desensitization. Such currents were blocked in a concentration-dependent manner by selective and nonselective 5-HT3 receptor antagonists but were unaffected by compounds acting at G protein-linked 5-HT receptors. A quantitative comparison of the pharmacological profiles of human and mouse recombinant 5-HT3R-AS receptor complexes revealed differences in the potencies of some antagonist or agonist compounds tested, the most dramatic example being (+)-tubocurarine, which demonstrated an approximately 1800-fold discrepancy in antagonist potency. In view of the small number of sequence substitutions that occur between the human and mouse homologues of the 5-HT3R-AS in the extracellularly located aminoterminal domain, compounds such as (+)-tubocurarine, in conjunction with site-directed mutagenesis, may prove to be valuable in locating amino acid residues that contribute to the ligand binding site(s) of the 5-HT3 receptor. Also, when methodological differences are taken into account, the present study suggests that a homo-oligomeric assembly of human 5-HT3R-AS subunits can account for the distinctive ligand binding properties of human 5-HT3 receptors established in postmortem brain tissue.
Mol Pharmacol 1995 Dec
PMID:Cloning and functional expression of a human 5-hydroxytryptamine type 3AS receptor subunit. 884 5

Recent studies have suggested that alcohols can affect the function of neurotransmitter-gated ion channels by a direct interaction with the receptor protein. However, the molecular region of the receptor protein that mediates the alcohol action is not known. To address this question, we studied the effect of ethanol on the function of recombinant nicotinic acetylcholine type alpha 7 (nACh alpha 7) receptors, 5-hydroxytryptamine (serotonin) type 3 (5-HT3) receptors, and a chimeric receptor constructed from these two receptors. The receptors were expressed in Xenopus oocytes and their function was studied using the two-electrode voltage-clamp technique. Ethanol inhibited the response of nACh alpha 7 receptors in a concentration-dependent manner over the concentration range of 5-100 mM; the EC50 for this inhibition was 33 mM ethanol. Ethanol decreased the maximal amplitude (Emax) of the nACh alpha 7 receptor agonist concentration-response curve, without significantly affecting the EC50. In contrast, ethanol potentiated 5-HT3 receptor-mediated responses at low agonist concentrations. The potentiation was concentration-dependent over the concentration range of 10-100 mM; the EC50 for this potentiation was 57 mM ethanol. The magnitude of the ethanol potentiation of 5-HT3 receptor-mediated responses decreased with increasing agonist concentration. The chimeric receptor had the amino-terminal domain from the nACh alpha 7 receptor and the transmembrane and carboxyl-terminal domains from the 5-HT3 receptor. Ethanol was found to inhibit the function of this chimeric receptor in a manner similar to that of nACh alpha 7 receptors. Because the inhibition transfers with the amino-terminal domain of the receptor, the observations suggest that the amino-terminal domain of the receptor is involved in the inhibition.
Mol Pharmacol 1996 Oct
PMID:Ethanol inhibition of nicotinic acetylcholine type alpha 7 receptors involves the amino-terminal domain of the receptor. 886 48

Homopentameric complexes of either the A or As subunit of the 5-hydroxytryptamine3 receptor form Ca(2+)-permeable channels that can be activated by the selective agonist 1-(m-chlorophenyl)-biguanide (mCPBG). In both N1E-115 neuroblastoma cells and human embryonic kidney 293 cells stably expressing the 5-HT3 receptor As subunit, (+)-verapamil, (-)-verapamil, diltiazem, and nimodipine caused reversible and concentration-dependent (IC50 = 2.5-6.5 microM) inhibition of the increases in cytosolic [Ca2+] evoked by mCPBG. In voltage-clamped human embryonic kidney 293 cells stably expressing the 5-HT3 receptor As subunit, similar concentrations of the Ca2+ channel antagonists (IC50 = 3.0-6.8 microM) accelerated the rate at which 5-HT-evoked currents decayed without affecting the amplitude of the peak current. In equilibrium competition binding assays to membranes from Sf9 cells infected with the 5-HT3 receptor As subunit, [3H]mCPBG and [3H]granisetron were displaced by (+)-verapamil, (-)-verapamil, and diltiazem; (+)-verapamil was approximately 10-fold more potent than (-)-verapamil and approximately-30-fold more potent than diltiazem. Nimodipine neither displaced [3H]granisetron binding nor affected its displacement by diltiazem and (+)-verapamil. The stereoselectivity of verapamil binding, which contrasts with the similar potency of each isomer in functional assays, was maintained when the incubations were performed at 20 degrees or when an antagonist of the 5-HT3 receptor, [3H]granisetron, was used as the radioligand. The interaction between verapamil and either [3H]mCPBG or [3H]granisetron binding was not competitive. We conclude that the inhibition of [3H]mCPBG binding by diltiazem and verapamil is mediated by a site that is distinct from both the agonist-binding site and from the site through which nimodipine inhibits 5-HT3 receptor function. Our results provide evidence for allosteric regulation of agonist binding to 5-HT3 receptors and the first example of a ligandgated ion channel whose function is directly inhibited by members of all three major classes of L-type Ca2+ channel antagonists.
Mol Pharmacol 1996 Nov
PMID:Direct inhibition of 5-hydroxytryptamine3 receptors by antagonists of L-type Ca2+ channels. 891 60

Several human Mendelian diseases, including the long-QT syndrome, malignant hyperthermia, and episodic ataxia/myokymia syndrome, have recently been demonstrated to be due to mutations in ion channel genes. Systematic mapping of ion channel genes may therefore reveal candidates for other heritable disorders. In this study, the GenBank and dbEST databases were used to identify members of several ion channel families (voltage-gated calcium and sodium, cardiac chloride, and all classes of potassium channels). Genes and ESTs without prior map localization were identified based on GDB and OWL database information and 15 genes and ESTs were selected for mapping. Of these 15, only the serotonin receptor 5HT3R had been previously mapped to a chromosome. A somatic cell hybrid panel (SCH) was screened with an STS from each gene and, if necessary the results verified by a second SCH panel. For three ESTs, rodent derived PCR products of the same size as the human STS precluded SCH mapping. For these three, human P1 clones were isolated and the genomic location was determined by metaphase FISH. These genes and ESTs can now be further evaluated as candidate genes for inherited cardiac, neuromuscular and psychiatric disorders mapped to these chromosomes. Furthermore, the ESTs developed in this study can be used to isolate genomic clones, enabling the determination of each transcript's genomic structure and physical map location. This approach may also be applicable to other gene families and may aid in the identification of candidate genes for groups of related heritable disorders.
Somat Cell Mol Genet 1996 Sep
PMID:Chromosomal localization of 15 ion channel genes. 903 51


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