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  • 1
    Digitale Medien
    Digitale Medien
    Glutamate Inhibits Adenylate Cyclase Activity in Dispersed Rat Hippocampal Cells Directly via an N-Methyl-d-Aspartate-Like Metabotropic Receptor (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 59 (1992), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: Three major subtypes of glutamate receptors that are coupled to cation channels—N-methyl-d-aspartate (NMDA), kainate, and α-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptors—are known as ionotropic receptors in the mammalian CNS. Recently, an additional subtype that is coupled to GTP binding proteins and stimulates (or inhibits) metabolism of phosphoinositides has been proposed as a metabotropic receptor. Incubation of dispersed hippocampal cells from adult rats with glutamate or NMDA decreased forskolin-stimulated cyclic AMP (cAMP) accumulation; half-maximal effects were obtained with 5.6 ± 2.2 and 6.4 ± 2.3 μM, respectively. Kainate and quisqualate were less potent. The effect of glutamate was antagonized by 2,3-diaminopropionate and 2-amino-5-phosphonovalerate, NMDA/glutamate receptor antagonists, but not by 0.5 μM Joro spider toxin, a specific blocker of the AMPA receptor. The inhibitory effect of glutamate on cAMP formation was not blocked by 2 μM tetrodotoxin or by the absence of Ca2+. In hippocampal membranes, glutamate, similar to carbachol, inhibited adenylate cyclase activity in a GTP-dependent manner. These findings suggest that the glutamate inhibition of adenylate cyclase is direct and is not due to a result of the release of other neurotransmitters. The effect of glutamate on cAMP accumulation was observed in an assay medium containing 0.7 mM MgCl2, which is known to inhibit both ionotropic NMDA receptor/channels in the hippocampus and metabotropic NMDA receptors in the cerebellum. The inhibitory effect of glutamate was abolished by pertussis toxin treatment. In conclusion, the rat hippocampus appears to contain a novel class of metabotropic receptors that prefer glutamate and NMDA and is coupled with adenylate cyclase in an inhibitory manner via pertussis toxin-sensitive GTP binding proteins.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1992.tb08319.x
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  • 2
    Digitale Medien
    Digitale Medien
    Ontogenesis of α2-Adrenoceptor Coupling with GTP-Binding Proteins in the Rat Telencephalon (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 53 (1989), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: The ontogenesis of α2-adrenoceptors and GTP-binding proteins and their coupling activity were investigated in telencephalon membranes of developing rats. The manganese-induced elevation of [3H]clonidine binding was increased in an age-dependent manner but the guanosine 5′-O-(3-thio)triphosphate-induced decrease in binding did not change. The extent of the binding of [3H]clonidine at 15 nM (saturable concentration) increased in an age-dependent manner and reached the adult level at 4 days after birth. Cholera toxin and pertussis toxin catalyzed ADP-ribosylation of proteins of 46 and 41/39 kilodaltons (kDa) in solubilized cholate extracts of the membranes. The 41/39-kDa proteins ADP-ribosylated by pertussis toxin (Giα+ Goα) were increased with age and reached the adult level at day 12, whereas the 46-kDa protein (Gsα) reached its peak on day 12 and then decreased to the fetal level at the adult stage. The immunoblot experiments of the homogenates with antiserum (specific antibody against α- and β-subunit of GTP-binding proteins) demonstrated that the 39-kDa α-subunit of (Goα) and the 36-kDa δ-subunit of GTP-binding protein (δ36) increased with postnatal age. In contrast, 35-kDa δ-subunit (δ35) did not change. From these results, it is suggested that the coupling activity of α-adrenoceptor with GTP-binding protein gradually develops in a manner parallel with the increase of α2-adrenoceptor and pertussis toxin sensitive GTP-binding proteins, Gi, and that α39β36γ may be related to the differentiation and/or growth of nerve cells in rat telencephalon.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1989.tb07321.x
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  • 3
    Digitale Medien
    Digitale Medien
    Possible Involvement of Inhibitory GTP Binding Regulatory Protein in α2-Adrenoceptor-Mediated Inhibition of Adenylate Cyclase Activity in Cerebral Cortical Membranes of Rats (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 45 (1985), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: Influences of α2-adrenoceptor stimulation on adenylate cyclase activity were investigated in cerebral cortical membranes of rats. Pretreatment of the membranes with islet-activating protein and NAD resulted in a significant increase in basal activity as well as in GTP-or forskolin/GTP-induced elevation of adenylate cyclase activity. Strong activation of adenylate cyclase was also caused in membranes pretreated with cholera toxin together with NAD in comparison to that in control membranes, suggesting that adenylate cyclase activity is perhaps regulated by stimulatory and inhibitory GTP binding regulatory protein existing in synaptic membranes. In addition, adrenaline (with propranolol) or clonidine significantly reduced adenylate cyclase activity stimulated by pretreatment with forskolin and GTP. The inhibitory effects of adrenaline were also observed in membranes pretreated with cholera toxin and NAD. Moreover, the inhibition by adrenaline or clonidine was completely abolished by treatment with (a) yohimbine or (b) islet-activating protein and NAD. It is suggested that α-receptor stimulation causes inhibitory influences on adenylate cyclase activity mediated by the inhibitory GTP binding regulatory protein in synaptic membranes of rat cerebral cortex.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1985.tb07219.x
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  • 4
    Digitale Medien
    Digitale Medien
    Increase in Neurite Formation and Acetylene line Release by Transfection of Growth-Associated Protein-43 cDNA into NG108–15 Cells (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 61 (1993), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: We previously reported that growth-associated protein-43 (GAP-43) could be involved in the maintenance of elongated neurites and that a decline in protein kinase C activity may be involved in accumulation of GAP-43. In the present study, to clarify the functional significance of GAP-43 for neurite maintenance and acetylcholine (ACh) release, we prepared NG-G11 cells by transfection of GAP-43 cDNA into NG108-15 cells. NG-G11 cells expressed GAP-43 mRNA at levels approximately twice that in nontransfected or vector-transfected cells under control conditions and after treatment with dibutyryl cyclic AMP (diBu-cAMP) or 12-O-tetradecanoylphorbol 13-acetate (TPA) plus diBu-cAMP. Neurite outgrowth after addition of diBu-cAMP was greater in NG-G11 than in control cells. In NG-G11 cells, neurites elongated by treatment with diBu-cAMP for 72 h were maintained after removal of the drug. Treatment with TPA plus diBu-cAMP for 24 h induced neurite outgrowth in NG-G11 cells, although control cells required 72 h. Depolarization by 50 mM KCI induced ACh release in both NG-G11 and control cells treated with diBu-cAMP or TPA/diBu-cAMP. Although removal of the drugs following diBu-cAMP treatment reversed ACh release to nontreated levels in control cells, a high-K+-induced level of ACh release remained in NG-G11 cells after removal of diBu-cAMP. ACh release induced by TPA plus diBu-cAMP for 24 h was further enhanced after removal of the drugs in NG-G11 cells, but it was not seen in control cells. These results suggest that levels of GAP-43 mRNA are correlated with neurite maintenance and the level of ACh release. Thus, GAP-43 may be involved in neuronal differentiation in NG108-15 cells.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1993.tb02155.x
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  • 5
    Digitale Medien
    Digitale Medien
    The Slow Cyclic GMP Increase Caused by Serotonin in NG108-15 Cells Is Not Inhibited by Antagonists of Known Serotonin Receptors: Possible Existence of a New Receptor Subtype Coupled with Membrane-Bound Guanylate Cyclase (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 57 (1991), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Characterization of the serotonin (5-HT〉induced cyclic GMP (cGMP) elevation was investigated in comparison with bradykinin- and ANP-induced elevations in NG108-15 cells. At 20 s, l,2-bis(2-aminophenoxy)ethaae-N,N,N′,N′-tetraaoetic acid tetraacetoxymethyl ester (BAPTA-AM, 100 μM), a membrane-permeabilized Ca2+ chelator, or N-monomethyl-L-arginine (NMMA, 300 μM), an inhibitor of L-arginine-derived nitric oxide (NO) synthesis, inhibited 5-HT-induced elevation by approximately 40%, and completely inhibited bradykinin-induced response. Neither 5-HT- nor ANP-induced cGMP elevation at 10 rain was affected by BAPTAAM or NMMA. The cGMP elevated by 5-HT as well as by ANP was effluxed to the extracellular medium. These results and our previous report suggest that 5-HT stimulates two subtypes of 5-HT receptors in NG108-15: first, 5-HT3 subtype stimulating Ca2+-sensitive cytosolic guanylate cyclaje through NO derived from L-arginine and second, a probably novel 5-HT receptor subtype involved in activation of membrane-bound guanylate cyclase.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1991.tb03804.x
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  • 6
    Digitale Medien
    Digitale Medien
    Pertussis Toxin Attenuates 5-Hydroxytryptamine1A Receptor-Mediated Inhibition of Forskolin-Stimulated Adenylate Cyclase Activity in Rat Hippocampal Membranes (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 52 (1989), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: The inhibition of forskolin-stimulated adenylate cyclase activity by 5-hydroxytryptamine (5-HT) receptor agonists was measured in rat hippocampal membranes isolated from animals treated with vehicle or islet-activating protein (IAP; pertussis toxin). In vehicle-treated animals, 5-HT, 8-hydroxy-2-(di-n-propylamino)tetralin, buspirone, and gepirone were potent in inhibiting forskolin-stimulated adenylate cyclase activity with EC50 values of 60, 76, 376, and 530 nM, respectively. IAP treatment reduced by 30–55% the 5-HT1A agonist inhibition of adenylate cyclase activity via 5-HT1A receptors. The data indicate that the inhibitory guanine nucleotide-binding protein or Go (a similar GTP-binding protein of unknown function purified from brain) mediates the 5-HT1A agonist inhibition of hippocampal adenylate cyclase.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1989.tb09209.x
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  • 7
    Digitale Medien
    Digitale Medien
    Uncoupling of Rat Cerebral Cortical α2-Adrenoceptors from GTP-Binding Proteins by N-Ethylmaleimide (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 49 (1987), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Pretreatment of membranes from rat cerebral cortex with N-ethylmaleimide (NEM) decreased [3H]clonidine binding in a concentration-dependent manner. The Bmax values of high-affinity sites for [3H]clonidine were reduced by 50 μM NEM treatment. Treatment with 500 μM NEM diminished the sum of Bmax of both high-and low-affinity components. GTP, Na+, and Mn2+ exerted little effect on [3H]clonidine binding in NEM-treated membranes. The addition of purified GTP-binding proteins caused an increase in the binding to the membranes pretreated with 50 μM NEM, but did not increase [3H]clonidine binding in membranes treated with 500 μM NEM. In contrast, NEM pretreatment inhibited islet activating protein (IAP)-catalyzed ADP ribosylation of membrane-bound (41,000-dalton) and purified (39,000/41,000-dalton) GTP-binding proteins. From these results, it is suggested that two or three categories of essential sulfhydryl groups are involved in the coupling between agonist, α2-adrenoceptor, and GTP-binding protein. One is a highly sensitive site to NEM (a concentration range of 1–50 μM), which is probably a cysteine residue, IAP-catalyzed ADP-ribosylating site on the α-subunit of GTP-binding protein. Other sites have low sensitivity to NEM (a concentration range of 0.1–1 mM), and are the binding domain of agonist and/or the coupling domain of GTP-binding protein on the α2-adrenoceptor. In addition, Ki-ras p21 protein may lack the capacity to couple with the α2-adrenoceptor.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1987.tb02452.x
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  • 8
    Digitale Medien
    Digitale Medien
    Stimulatory Effects of Protein Kinase C and Calmodulin Kinase II on N-Methyl-d-Aspartate Receptor/Channels in the Postsynaptic Density of Rat Brain (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 61 (1993), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: To clarify the regulatory mechanism of the N-methyl-d-aspartate (NMDA) receptor/channel by several protein kinases, we examined the effects of purified type II of protein kinase C (PKC-II), endogenous Ca2+/calmodulin-dependent protein kinase II (CaMK-II), and purified cyclic AMP-dependent protein kinase on NMDA receptor/ channel activity in the postsynaptic density (PSD) of rat brain. Purified PKC-II and endogenous CaMK-II catalyzed the phosphorylation of 80–200-kDa proteins in the PSD and l-glutamate-(or NMDA)-induced increase of (+)-5-[3H]methyl-10, 11-dihydro-5H-dibenzo[a, d]cyclohepten-5, 10-imine maleate ([3H]MK-801; open channel blocker for NMDA receptor/channel) binding activity was significantly enhanced. However, the pretreatment of PKC-II-and CaMK-II-catalyzed phosphorylation did not change the binding activity of l-[3H]glutamate, cis-4-[3H](phospho-nomethyl)piperidine-2-carboxylate ([3H]CGS-19755; competitive NMDA receptor antagonist), [3H]glycine, α-[3H]-amino-3-hydroxy-5-methyl-isoxazole-4-propionate, or [3H]-kainate in the PSD. Pretreatment with PKC-II-and CaMK-II-catalyzed phosphorylation enhanced l-glutamate-induced increase of [3H]MK-801 binding additionally, although purified cyclic AMP-dependent protein kinase did not change l-glutamate-induced [3H]MK-801 binding. From these results, it is suggested that PKC-II and/or CaMK-II appears to induce the phosphorylation of the channel domain of the NMDA receptor/channel in the PSD and then cause an enhancement of Ca2+ influx through the channel.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1993.tb03542.x
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  • 9
    Digitale Medien
    Digitale Medien
    Possible Involvement of Pertussis Toxin-Sensitive G Proteins and D2 Dopamine Receptors in the A1 Adenosine Receptor-Adenylate Cyclase System in Rat Cerebral Cortex (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 55 (1990), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: To identify the involvement of dopamine receptors in the transmembrane signaling of the adenosine receptor-G protein-adenylate cyclase system in the CNS, we examined the effects of pertussis toxin (islet-activating protein, IAP) and apomorphine on A1 adenosine agonist (-)N6-R-[3H]phenylisopropyladenosine ([3H]PIA) and antagonist [3H]xanthine amine congener ([3H]XAC) binding activity and adenylate cyclase activity in cerebral cortex membranes of the rat brain. Specific binding to a single class of sites for [3H]XAC with a dissociation constant (KD) of 6.0 ± 1.3 nM was observed. The number of maximal binding sites (Bmax) was 1.21 ± 0.13 pmol/mg protein. Studies of the inhibition of [3H]XAC binding by PIA revealed the presence of two classes of PIA binding states, a high-affinity state (KD= 2.30 ±1.16 nM) and a low-affinity state (KD= 1,220 ± 230 nM). Guanosine 5′-(3-O-thio)triphosphate or IAP treatment reduced the number of the high-affinity state binding sites without altering the KD for PIA. Apomorphine (100 μM) increased the KD value 10-fold and decreased Bmax by ∼20% for [3H]PIA. The effect of apomorphine on the KD value increase was irreversible and due to a conversion from high-affinity to low-affinity states for PIA. The effect was dose dependent and was mediated via D2 dopamine receptors, since the D2 antagonist sulpiride blocked the phenomenon. The inhibitory effect of PIA on adenylate cyclase activity was abolished by apomorphine treatment. There was no effect of apomorphine on displacement of [3H]quinuclidinyl benzilate (muscarinic ligand) binding by carbachol. These data suggest that A1 adenosine receptor binding and function are selectively modified by D2 dopaminergic agents.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1990.tb04949.x
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  • 10
    Digitale Medien
    Digitale Medien
    Serotonin Stimulates Both Cytosolic and Membrane-Bound Guanylate Cyclase in NG108–15 Cells (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 55 (1990), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: The cyclic GMP (cGMP) content was rapidly (〉30 s) increased by serotonin [5-hydroxytryptamine (5-HT)] (EC50= 10 μM), and the increase lasted for 〉 10 min in NG108–15 cells. The 5-HT-induced elevation of cGMP level (EC50= 10 μM) at 20 s (“fast” elevation) was inhibited by ICS 205–930 or MDL 72,222 and by Ca2+ deficiency in the reaction medium but not by organic Ca2+ antagonists. The 5-HT effect at 10 min (“slow” elevation) was not inhibited by several antagonists for 5-HT receptors of the IA, IB, IC., ID, 2, and 3 subtypes and was independent from external Ca2+ concentration. The fast and slow effects of 5-HT were similar to the effects of bradykinin and atrial natriuretic peptide (ANP), respectively, in aspects of both Ca2+ dependency and time course of the effects. Bradykinin transiently stimulated formation of inositol phosphates as well as accumulation of cGMP, a finding suggesting that intracellular Ca2+ is involved in bradykinin-induced cGMP accumulation as shown in the fast response to 5-HT. ANP. an activator of membrane-associated guanylate cyclase (mGC), slowly (∼60 s) increased the cGMP content (EC50= 10 nAf), a result lasting for 〉10 min, and the effects were independent from external Ca2+, as shown in the slow response to 5-HT. 5-HT and ANP did not induce formation of inositol phosphates. These results suggest that (a) the fast effects of 5-HT on cGMP level elevation are mediated by 5-HT3 receptors, which activate cytosolic guanylate cyclase through Ca2+ entry via ion channels other than voltage-sensitive Ca24 channels, and (b) the slow effects seem to be due to an unidentified subtype of 5-HT receptor that activates ANP-sensitive mGC.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1990.tb04971.x
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