UNIPROT:P46098 - FACTA Search

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Query: UNIPROT:P46098 (5-HT3 receptor)
2,290 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Serotonin 5-HT1A receptors have been reported to be negatively coupled to muscarinic receptor-stimulated phosphoinositide turnover in the rat hippocampus. In the present study, we have investigated further the pharmacological specificity of this negative control and attempted to elucidate the mechanism whereby 5-HT1A receptor activation inhibits the carbachol-stimulated phosphoinositide response in immature or adult rat hippocampal slices. Various 5-HT1A receptor agonists were found to inhibit carbachol (10 microM)-stimulated formation of total inositol phosphates in immature rat hippocampal slices with the following rank order of potency (IC50 values in nM): 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) (11) greater than ipsapirone (20) greater than gepirone (120) greater than RU 24969 (140) greater than buspirone (560) greater than 1-(m-trifluoromethylphenyl)piperazine (1,500) greater than methysergide (5,644); selective 5-HT1B, 5-HT2, and 5-HT3 receptor agonists were inactive. The potency of the 5-HT1A receptor agonists investigated as inhibitors of the carbachol response was well correlated (r = 0.92) with their potency as inhibitors of the forskolin-stimulated adenylate cyclase in guinea pig hippocampal membranes. 8-OH-DPAT (10 microM) fully inhibited the carbachol-stimulated formation of inositol di-, tris-, and tetrakisphosphate but only partially antagonized (-40%) inositol monophosphate production. The effect of 8-OH-DPAT on carbachol-stimulated phosphoinositide turnover was not prevented by addition of tetrodotoxin (1 microM), by prior destruction of serotonergic afferents, by experimental manipulations causing an increase in cyclic AMP levels (addition of 10 microM forskolin), or by changes in membrane potential (increase in K+ concentration or addition of tetraethylammonium). Prior intrahippocampal injection of pertussis toxin also failed to alter the ability of 8-OH-DPAT to inhibit the carbachol response. Carbachol-stimulated phosphoinositide turnover in immature rat hippocampal slices was inhibited by the protein kinase C activators phorbol 12-myristate 13-acetate (10 microM) and arachidonic acid (100 microM). Moreover, the inhibitory effect of 8-OH-DPAT on the carbachol response was blocked by 10 microM quinacrine (a phospholipase A2 inhibitor) but not by BW 755C (100 microM), a cyclooxygenase and lipoxygenase inhibitor. These results collectively suggest that 5-HT1A receptor activation inhibits carbachol-stimulated phosphoinositide turnover by stimulating a phospholipase A2 coupled to 5-HT1A receptors, leading to arachidonic acid release. Arachidonic acid could in turn activate a gamma-protein kinase C with as a consequence an inhibition of carbachol-stimulated phosphoinositide turnover. This inhibition may be the consequence of a phospholipase C phosphorylation and/or a direct effect on the muscarinic receptor.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Potential mechanisms involved in the negative coupling between serotonin 5-HT1A receptors and carbachol-stimulated phosphoinositide turnover in the rat hippocampus. 184 78

The effect of agents that activate or inhibit protein kinase C (PKC) on the function of recombinant 5-HT3 receptors expressed in Xenopus oocytes was studied. The PKC activator phorbol 12-myristate 13-acetate (PMA) induced a long-lasting increase in the amplitude of 5-HT-activated ion current. The potentiation was maximal at 20 min and had a duration of approximately 60 min. The inactive phorbol ester, 4 alpha-PMA, had no effect on 5-HT3 receptor-mediated current. The PMA-induced potentiation was concentration-dependent over the concentration range 0.1-300 nM. The percentage potentiation by PMA was maximal at low 5-HT concentrations and decreased with increasing concentrations of 5-HT. For current activated by 0.1 microM 5-HT, maximal potentiation (Emax) was 667% of control, the EC50 was 15 nM and the apparent Hill coefficient was 0.99. The PKC inhibitor, staurosporin, antagonized the PMA potentiation; whereas, inhibitors of protein kinase A (PKA) or tyrosine kinase had no effect on this potentiation. The observations show that PMA can potentiate 5-HT3 receptor-mediated responses and suggest that this potentiation is mediated by activation of PKC.
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PMID:Potentiation of 5-HT3 receptor-mediated responses by protein kinase C activation. 748 49

1. 5-Hydroxytryptamine (5-HT) has been shown to induce contraction of tracheal smooth muscle. However, the mechanisms of action of 5-HT are not known. We therefore investigated the effects of 5-HT on phospholipase C (PLC)-mediated phosphoinositide (PI) hydrolysis and its regulation in canine cultured tracheal smooth muscle cells (TSMCs) labelled with [3H]-inositol. 5-HT-induced inositol phosphates (IPs) accumulation was time- and dose-dependent with a half-maximal response (EC50) and a maximal response at 0.38 +/- 0.05 and 10 microM, respectively. 2. Ketanserin and mianserin (10 and 100 nM), 5-HT2 receptor antagonists, were equipotent in blocking the 5-HT-induced IPs accumulation with pKB values of 8.46 and 8.21, respectively. In contrast, the dose-response curves of 5-HT-induced IPs accumulation were not shifted until the concentrations of NAN-190 and metoclopramide (5-HT1A and 5-HT3 receptor antagonists, respectively) were increased up to 10 microM. 3. Pretreatment of TSMCs with pertussis toxin or cholera toxin did not inhibit the 5-HT-induced IPs accumulation, but partially inhibited the AlF(4-)-induced IPs response. 4. Stimulation of IPs accumulation by 5-HT required the presence of external Ca2+ and was blocked by EGTA. The addition of Ca2+ (3-620 nM) to digitonin-permeabilized TSMCs directly stimulated IPs accumulation. A further Ca(2+)-dependent increase in IPs accumulation was obtained by inclusion of either guanosine 5'-O-(3-thiotriphoshate) (GTP gamma S) or 5-HT. The combination of GTP gamma S and 5-HT elicited an additive effect on IPs accumulation. 5. Treatment with phorbol 12-myristate 13-acetate (PMA, 1 microM, 30 min) abolished the 5-HT-induced IPs accumulation. The concentrations of PMA that gave a half-maximal and maximal inhibition of 5-HT-induced IPs accumulation were 2.2 +/- 0.4 nM and 1 microM, n = 3, respectively. The protein kinase C (PKC) activator, 4 alpha-phorbol 12,13-didecanoate, at 1 microM, did not influence this response. The inhibitory effect of PMA was reversed by staurosporine, a PKC inhibitor, suggesting that the inhibitory effect of PMA is mediated through the activation of PKC. 6. The site of this inhibition was further investigated by examining the effect of PMA on AlF(4-)-induced IPs accumulation in canine TSMCs. AlF(4-)-stimulated IPs accumulation was inhibited by PMA treatment, suggesting that the effect of PMA is distal to the 5-HT receptor. 7. Acetylcholine-induced IPs accumulation was completely inhibited by atropine, but not affected by ketanserin or mianserin, suggesting that 5-HT-induced IPs accumulation is not due to release of acetylcholine.8. These results demonstrate that 5-HT directly stimulates PLC-mediated PI hydrolysis via a pertussis toxin- and cholera toxin-insensitive GTP binding protein in canine TSMCs and that this coupling process is negatively regulated by PKC. 5-HT2 receptors may be predominantly mediating IPs accumulation and presumably IP-induced Ca2+ release may function as the transducing mechanism for 5-HT stimulated contraction of tracheal smooth muscle.
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PMID:5-Hydroxytryptamine receptor-mediated phosphoinositide hydrolysis in canine cultured tracheal smooth muscle cells. 801 56

The calcium requirement for serotonin (5-HT)- and the 5-HT3 receptor agonists, 2-Me-5-HT- and PBG-dependent breakdown of phosphatidyl inositol has been examined in the rat fronto-cingulate cortex. The omission of added Ca2+ from the Kreb's incubation medium reduced the [3H]inositol phosphate accumulation from pre-labelled phospholipids. Removal of Ca2+ by pre-incubation with EGTA (0.5 mM), as well as the addition of the calcium channel blocker, lanthanum (10 microM), abolished the 5-HT- and the 5-HT3 receptor agonists'-stimulated phosphoinositide (PI) response. By contrast, the calcium ionophores, A 23187 and Ionomycin (both at 30 microM) stimulated PI hydrolysis, and this effect was additive to the increased PI turnover induced by 5-HT, 2-Me-5-HT and PBG. The increase in phosphoinositide hydrolysis induced by 5-HT and 2-Me-5-HT was significantly inhibited by phorbol dibutyrate (PDBu) and phorbol myristate acetate, indicating that the activation of protein kinase C (PKC) may provide negative feedback to the PI response induced by 5-HT and 2-Me-5-HT-stimulated PI metabolism was reversed by the PKC inhibitors, staurosporine, calphostin C and chelerythrine (all at 10 microM), however, Pertussis toxin (0.5 and 1 microgram) had no effect on either 5-HT's or 2-Me-5-HT's increased stimulation of PI hydrolysis, suggesting that this response is not associated to a Gi GTP binding protein.
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PMID:Further characterization of 5-HT- and 5-HT3 receptor agonists'-stimulated phosphoinositol phosphates accumulation. 839 45

The interaction between serotonin and excitatory amino acid agonists at rat neocortical neurons was investigated using the grease-gap recording method. Depolarization evoked by 50 microM N-methyl-D-aspartate was dose dependently facilitated by serotonin (5-HT) (1 to 100 microM) giving a bell-shaped dose-response curve with maximum enhancement at 30 microM. In contrast, quisqualate and kainate depolarizations were not enhanced. Subnanomolar concentrations of methysergide, ritanserin and spiperone, but not ICS 205-930, attenuated the 5-HT enhancement, compatible with 5-HT2, but not 5-HT1 or 5-HT3 receptor subtype involvement. Enhancement was observed with 5-HT2 receptor agonists, whereas 5-HT1 receptor subtype agonists had either no effect (1B and 1C) or reduced (1A) the N-methyl-D-aspartate depolarization. Scopolamine and prazosin reduced the N-methyl-D-aspartate depolarization and blocked facilitation induced by carbachol and phenylephrine, but not that due to 5-HT. Tetrodotoxin reduced the N-methyl-D-aspartate depolarization, but the facilitation by 5-HT persisted. Activators of protein kinase C (phorbol diacetate and 1-oleoyl-2-acetyl-sn-glycerol) did not mimic the serotonin facilitation. We conclude that serotonin enhances N-methyl-D-aspartate depolarization of rat cortical neurons through activation of 5-HT2 receptors, however the cellular mechanism underlying the facilitation remains to be established.
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PMID:Activation of 5-HT2 receptors facilitates depolarization of neocortical neurons by N-methyl-D-aspartate. 844 27

Two splice variants of the ligand-gated 5-hydroxytryptamine or serotonin 5-HT3 receptor that differ in a six-amino-acid deletion were cloned by polymerase chain reaction from the hippocampus x neuroblastoma cell line HN9.10e. When expressed in Xenopus oocytes, both variants individually formed 5-HT3 receptors that revealed no significant differences in current responses to the agonists 5-HT and 1-phenylbiguanide and block by the specific antagonist LY-278, 584-maleate. For both receptors, the monovalent cations Na+, K+, Rb+ and Li+ showed the same relative permeability; NH4(+)permeated approximately 2.7 times better than Na+, and Tris+ was only poorly permeable. In contrast to other reports, the receptors were completely and reversibly blocked by extracellular Cs+ in both oocytes and native HN9.10 cells. Moreover, Ca2+ was not permeant and exhibited a concentration-dependent decrease (0.9-18 mM) of the 5-HT-induced currents without affecting the inward rectification of the current/voltage relation. The two receptors were reversibly inhibited by nanomolar concentrations of the specific inhibitor of protein kinase C (PKC) bisindolylmaleimide, but not by the equipotent and less specific inhibitor staurosporine. A regulatory effect on both 5-HT3 receptor subunits by PKC-mediated protein phosphorylation might be possible, however, a functional role of the two splice variants present in one cell remains to be determined.
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PMID:Functional characterization of two 5-HT3 receptor splice variants isolated from a mouse hippocampal cell line. 866 78

We examined the effects of several protein kinase C (PKC) inhibitors on the murine 5-hydroxytryptamine3 (5-HT3) receptor to determine whether they acted directly on the receptor. The 5-HT-evoked currents in Xenopus laevis oocytes expressing the recombinant 5-HT3 receptor were measured with the two-electrode voltage-clamp technique. The PKC inhibitors bisindolylmaleimide I (BIM, GF109203x) and staurosporine, but not calphostin C or chelerythrine, decreased the 5-HT3 receptor-mediated currents when coapplied with 5-HT. BIM blocked 0.5 microM 5-HT-elicited currents with an IC50 value of 7 nM, whereas in the presence of 5 microM staurosporine, 42% inhibition of 0.5 microM 5-HT-mediated currents was observed. Increasing concentrations of BIM resulted in a rightward shift of the 5-HT concentration-response curve, without altering efficacy. A Schild plot was generated, which had a slope of -1.01, suggesting competitive antagonism. The Ki value of BIM was determined to be 29 nM. To confirm competitive antagonism, a competitive binding assay was performed on Sf21 insect cells infected with the mouse 5-HT3 receptor cDNA in a baculovirus expression vector. BIM completely displaced binding of the selective 5-HT3 receptor antagonist [3H]GR65630. BIM bound to the 5-HT3 receptor with a Ki value of 61 nM, which was slightly less potent than that of the selective 5-HT3 receptor antagonist MDL72222 (27 nM). The PKC inhibitor BIM is a potent competitive antagonist at the 5-HT3 receptor.
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PMID:Competitive antagonism of the mouse 5-hydroxytryptamine3 receptor by bisindolylmaleimide I, a "selective" protein kinase C inhibitor. 1038 62

The study was conducted on a human (Jurkat) T cell line, loaded with a Na+ fluorescent probe, SBFI/AM. Serotonin and an agonist of 5-HT3 receptor-channels, 2-methyl-5HT, evoked Na+ influx, whereas the agonists of other serotonergic receptor subtypes, i.e., 5-HT1A and 5-HT1B receptors, failed to induce Na+ influx in these cells. By using 3H-BRL43694, an agonist of 5-HT3 receptor-channels, we characterized 5-HT3 lymphocyte receptors which exhibited a density (Bmax) of 300 +/- 20 fmol/10(6) cells and a Kd of 30 nM in Jurkat T cells. The T-cell 5-HT3 receptor-channel is not regulated either by the protein kinase C or by the free intracellular calcium concentrations as the agents known to activate the PKC and to induce increases in intracellular free calcium concentrations failed to influence the free intracellular Na+ concentrations, [Na+]i, in these cells. Furthermore, an increase in [Na+]i, induced by 2-methyl-5HT, via 5-HT3 receptor-channels seems to stimulate T-cell activation by facilitating the progression of T cells from S to G2/M phase of the cell cycle.
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PMID:5-HT3 receptor-channels coupled with Na+ influx in human T cells: role in T cell activation. 1049 77

The effects of phorbol 12-myristate, 13-acetate (PMA) on 5-hydroxytryptamine (5-HT)-evoked ion currents in the mouse 5-HT3A receptor were examined. Perfusion with PMA caused a concentration dependent potentiation of 5-HT mediated currents and increased both potency and efficacy of 5-HT at the 5-HT3A receptor expressed in Xenopus oocytes. Enhancement of receptor function was partially blocked by injection of oocytes with PKCI, the peptide inhibitor of protein kinase C (PKC). Mutation of all 12 intracellular serine and threonine residues to alanine was without effect on PMA-induced potentiation of 5-HT elicited currents. Mutation of tyrosine 458 in the 5-HT3A receptor lacking intracellular serines and threonines reduced the PMA-induced potentiation of 5-HT evoked currents by approximately 55%. In contrast, mutation of tyrosine 458 in the wild-type receptor did not alter PMA-induced enhancement. The tyrosine kinase inhibitor, lavendustin A, reduced the enhancement of 5-HT3A receptor mediated currents by PMA in the mutant 5-HTA3A receptor containing no intracellular serine or threonine residues, but not in the wild-type receptor. Thus, the role of intracellular serines and threonines is redundant with that of tyrosine, suggesting that these two components act through a similar pathway in response to PMA treatment.
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PMID:Enhancement of 5-hydroxytryptamine3A receptor function by phorbol 12-myristate, 13-acetate is mediated by protein kinase C and tyrosine kinase activity. 1244 87

Modulation of neurotransmitter-gated membrane ion channels by protein kinase C (PKC) has been the subject of a number of studies. However, less is known about PKC modulation of the serotonin type 3 (5-HT3) receptor, a ligand-gated membrane ion channel that can mediate fast synaptic transmission in the central and peripheral nervous system. Here, we show that PKC potentiated 5-HT3 receptor-mediated current in Xenopus oocytes expressing 5-HT3A receptors and mouse N1E-115 neuroblastoma cells. In addition, using a specific antibody directed to the extracellular N-terminal domain of the 5-HT3A receptor, treatment with the PKC activator, 4 beta-phorbol 12-myristate 13-acetate (PMA), significantly increased surface immunofluorescence. PKC also increased the amount of 5-HT3A receptor protein in the cell membrane without affecting the amount receptor protein in the total cell extract. The magnitude of PMA potentiation of 5-HT3A receptor-mediated responses is correlated with the magnitude of PMA enhancement of the receptor abundance in the cell surface membrane. PMA potentiation is unlikely to occur via direct phosphorylation of the 5-HT3A receptor protein since the potentiation was not affected by point mutation of each of the putative sites for PKC phosphorylation. However, preapplication of phalloidin, which stabilizes the actin polymerization, significantly inhibited PMA potentiation of 5-HT-activated responses in both N1E-115 cells and oocytes expressing 5-HT3A receptors. On the other hand, latrunculin-A, which destabilizes actin cytoskeleton, enhanced the PMA potentiation of 5-HT3A receptors. The observations suggest that PKC can modulate 5-HT3A receptor function and trafficking through an F-actin-dependent mechanism.
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PMID:Modulation of 5-HT3 receptor-mediated response and trafficking by activation of protein kinase C. 1279 92

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