Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.11 (AMPK)
 12,425 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Activation of cAMP-dependent protein kinase (kinase A) has recently been shown to enhance responses evoked by stimulation of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptors in cultured hippocampal pyramidal neurons. Here we report results of experiments designed to determine if activation of the cAMP cascade potentiates synaptic strength in field CA1 of rat hippocampal slices. We find that bath application of the direct adenylate cyclase activator forskolin (50 microM) enhances the field excitatory postsynaptic potential (EPSP) slope and population spike amplitude evoked by stimulation of Schaffer/commissural afferents. This effect is potentiated by the phosphodiesterase inhibitor and adenosine receptor antagonist 3-isobutyl-1-methylxanthine (IBMX). The enhancement produced by forskolin is suppressed in the presence of adenylate cyclase inhibitors and is not mimicked by the inactive forskolin analogue 1,9-dideoxyforskolin, indicating that, indeed, activation of adenylate cyclase mediates the effects of forskolin in field CA1. Our observations support the idea that changes in intracellular cAMP levels can modulate synaptic efficacy of excitatory glutamatergic synapses in the mammalian hippocampus.
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PMID:Modulation of synaptic efficacy in field CA1 of the rat hippocampus by forskolin. 137 10

The adenylate cyclase system has been studied from the standpoint of its significance in cholinergic modulation of the synaptic transmission in the CA1 field of the rat hippocampal slices. Microionphoretic application of ACh as well as addition of either carbachol or tolbutamide (an inhibitor of cAMP-dependent protein kinase) blocked the transmission in synapses formed by the Schaffer collaterals and commissural fibres with dendrites of carbacholine both the number of releasing quanta of the neurotransmitter and the probability of their release decreased. Atropine eliminated the inhibitory effect of carbacholine on synaptic transmission. Dibutyryl cAMP and forskolin increased the amplitude of synaptic potentials and completely or partially prevented the inhibitory effect of cholinomimetics on synaptic potentials. The results obtained revealed opposite effects of cholinomimetics and activators of the adenylate cyclase system on neurotransmission in synapses formed by the Schaffer collaterals/commissural fibres and dendrites of pyramidal neurons of the hippocampal CA1 field.
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PMID:[The role of the adenyl cyclase system in cholinergic modulation of synaptic transmission in the hippocampus]. 257 80

In situ hybridization was used to localize cAMP-dependent protein kinase (PKA) mRNAs in the adult mouse CNS. The PKA holoenzyme contains two catalytic (C) subunits and a regulatory (R) subunit dimer. Our studies demonstrate expression of two isoforms of C (C alpha and C beta) and four isoforms of R (RI alpha, RI beta, RII alpha, and RII beta) in the CNS. mRNAs for C alpha, RI alpha, and RI beta preferentially localize in the neocortex, caudate-putamen, hypothalamus, thalamus, and hippocampus. Hybridization with C beta and RII beta probes is clearly distinguished from the C alpha-like pattern by a reduced level of hybridization in the thalamus and by a relative increase in expression in the dentate gyrus compared with cell layers CA1-3 in the hippocampus. RII alpha transcripts are very specifically localized in the medial habenula. The differential expression of PKA subunit genes suggests that functional differences in cAMP responses within neural tissues may be mediated by the biochemical properties of specific PKA isoforms.
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PMID:Distinct patterns of cAMP-dependent protein kinase gene expression in mouse brain. 261 96

The cAMP-dependent protein kinase (PKA) has been shown to play an important role in long-term potentiation (LTP) in the hippocampus, but little is known about the function of PKA in long-term depression (LTD). We have combined pharmacologic and genetic approaches to demonstrate that PKA activity is required for both homosynaptic LTD and depotentiation and that a specific neuronal isoform of type I regulatory subunit (RI beta) is essential. Mice carrying a null mutation in the gene encoding RI beta were established by use of gene targeting in embryonic stem cells. Hippocampal slices from mutant mice show a severe deficit in LTD and depotentiation at the Schaffer collateral-CA1 synapse. This defect is also evident at the lateral perforant path-dentate granule cell synapse in RI beta mutant mice. Despite a compensatory increase in the related RI alpha protein and a lack of detectable changes in total PKA activity, the hippocampal function in these mice is not rescued, suggesting a unique role for RI beta. Since the late phase of CA1 LTP also requires PKA but is normal in RI beta mutant mice, our data further suggest that different forms of synaptic plasticity are likely to employ different combinations of regulatory and catalytic subunits.
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PMID:Hippocampal long-term depression and depotentiation are defective in mice carrying a targeted disruption of the gene encoding the RI beta subunit of cAMP-dependent protein kinase. 756 30

1. Previous studies have shown that beta-adrenergic receptor activation has many effects on neuronal function in hippocampal area CA1. However, all of the physiological effects of beta-adrenergic receptor activation in this region reported to date have been attributed to postsynaptic mechanisms. A series of studies was performed to test the hypothesis that beta-adrenergic receptor activation also acts presynaptically to enhance excitatory synaptic transmission. 2. Application of the selective beta-adrenergic agonist isoproterenol to hippocampal slices induced an increase in the amplitude of evoked excitatory postsynaptic currents (EPSCs) in CA1 pyramidal cells. This response was potentiated in the presence of a cyclic nucleotide phosphodiesterase inhibitor. Isoproterenol also resulted in the appearance of a late inward synaptic current that likely represents polysynaptically evoked EPSCs. Both the increased amplitude of the monosynaptic EPSC and the appearance of polysynaptic EPSCs in response to isoproterenol were blocked by H89, an inhibitor of adenosine 3',5'-cyclic monophosphate (cAMP)-dependent protein kinase. 3. Isoproterenol induced an increase in the frequency of spontaneous miniature EPSCs but did not affect the amplitude of these currents. In addition, isoproterenol had no effect on currents elicited by direct application of the ionotropic glutamate receptor agonist, (R,S)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA). 4. These results suggest that activation of presynaptic beta-adrenergic receptors enhances synaptic transmission in area CA1 via activation of cAMP-dependent protein kinase.
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PMID:Presynaptic enhancement of excitatory synaptic transmission by beta-adrenergic receptor activation. 780 26

The inhibition of voltage-activated Ca2+ channel currents by cortisol (hydrocortisone), the principal glucocorticoid in man and guinea pig, was examined in freshly dissociated pyramidal neurons from the adult guinea pig hippocampal CA1 region using whole-cell voltage-clamp recordings. Steady-state inhibition by cortisol of the peak Ca2+ channel current evoked by depolarization from -80 to -10 mV increased in a concentration-dependent fashion, with a maximal inhibition of 63 +/- 4% of the total current at 100 microM. Cortisone had a maximal 17 +/- 2% inhibition at 10 microM. Corticosterone and the metabolite allotetrahydrodeoxycorticosterone exhibited a plateau of inhibition of around 15% and 25%, respectively, between 10 pM and 100 nM; both compounds continued to inhibit at concentrations > 10(-7) M. Analysis of tail currents at -80 mV showed that cortisol and corticosterone had no effect on the voltage-dependent activation or deactivation of the Ca2+ channel current. However, cortisol slowed the activation of the current. Cortisol inhibited both the N-type or omega-conotoxin (CgTX)-sensitive, and the L-type or nifedipine (NIF)-sensitive Ca2+ channel current but had no effect on the CgTX/NIF-insensitive Ca2+ channel current. In neurons isolated from pertussis toxin (PTX)-treated animals, the cortisol inhibition was significantly diminished. Intracellular dialysis with GDP-beta-S (500 microM) or with the specific inhibitors of protein kinase C (PKC), the pseudosubstrate PKC inhibitor (PKCI 19-31) (2 microM) and bisindolylmaleimide (BIS) (1 microM) significantly diminished the cortisol inhibition of the Ca2+ channel current. The specific inhibitor of cAMP-dependent protein kinase (PKA) inhibitor, Rp-cAMPS (100 microM) had no effect.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Cortisol inhibition of calcium currents in guinea pig hippocampal CA1 neurons via G-protein-coupled activation of protein kinase C. 782 88

Studies carried out with mammals and invertebrates suggest that Ca(2+)-sensitive adenylyl cyclases may be important for neuroplasticity. Long-term potentiation in the hippocampus requires increases in intracellular Ca2+ which are accompanied by elevated cyclic AMP (cAMP). Furthermore, activation of cAMP-dependent protein kinase is required for the late stage of long-term potentiation in the CA1 region of the hippocampus, which is also sensitive to inhibitors of transcription. Therefore, some forms of synaptic plasticity may require coordinate regulation of transcription by Ca2+ and cAMP. In this study, we demonstrate that the expression of type I adenylyl cyclase in HEK-293 cells allows Ca2+ to stimulate reporter gene activity mediated through the cAMP response element. Furthermore, simultaneous activation by Ca2+ and isoproterenol caused synergistic stimulation of transcription in HEK-293 cells and cultured neurons. We propose that Ca2+ and neurotransmitter stimulation of type I adenylyl cyclase may play a role in synaptic plasticity by generating optimal cAMP signals for regulation of transcription.
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PMID:Type I adenylyl cyclase functions as a coincidence detector for control of cyclic AMP response element-mediated transcription: synergistic regulation of transcription by Ca2+ and isoproterenol. 796 63

Sequential alterations in the binding of [3H]cyclic AMP (cAMP) as an indicator of cAMP-dependent protein kinase (cAMP-DPK) binding activity following transient cerebral ischaemia were studied in the gerbil brain using receptor autoradiography. Transient ischaemia was induced for 10 min. [3H]cAMP binding in the stratum oriens and pyramidale of the hippocampal CA1 sector significantly decreased in the early post-ischaemic stage and showed severe reduction 7 days and 1 month after recirculation. By contrast, [3H]cAMP binding showed no significant alterations in the stratum radiatum of the hippocampal CA1 sector and the stratum pyramidale of the hippocampal CA3 sector up to 48 h after ischaemia. However, the binding in these areas significantly decreased 7 days and 1 month after ischaemia. The stratum lacunosum-moleculare of the hippocampal CA1 sector and dentate gyrus showed no significant changes in [3H]cAMP binding throughout the recirculation period. However, in the dorsolateral part of the striatum, where severe neuronal damage was seen morphologically, [3H]cAMP binding was significantly reduced only one month after ischaemia. These results indicate that marked alteration of intracellular signal transduction precedes neuronal damage in the hippocampal CA1 sector, but not in the striatum. Furthermore, our autoradiographic data suggest that post-ischaemic alteration in [3H]cAMP binding between the hippocampal CA1 sector and striatum may be produced by different mechanisms.
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PMID:Sequential changes of [3H]cyclic AMP binding in the gerbil brain following transient cerebral ischaemia. 810 69

The inhibition of Ca2+ channel currents by endogenous brain steroids was examined in freshly dissociated pyramidal neurons from the adult guinea pig hippocampal CA1 region. The steady-state inhibition of the peak Ca2+ channel current evoked by depolarizing steps from -80 to -10 mV occurred in a concentration-dependent manner with the following IC50 values: pregnenolone sulfate (PES), 11 nM; pregnenolone (PE), 130 nM; and allotetrahydrocorticosterone (THCC), 298 nM. THCC, PE, and PES depressed a fraction of the Ca2+ channel current with a maximal inhibition of 60% of the total current. However, substitution of an acetate group for the sulfate group on PES resulted in a complete loss of activity. Progesterone had no effect (4% inhibition at 100 microM). Intracellular dialysis of PES had no effect on the Ca2+ current; concomitant extracellular perfusion of PES showed normal inhibitory activity, suggesting that the steroid binding site can only be accessed extracellularly. Analysis of tail currents at -80 mV demonstrated that THCC and PES slowed the rate of Ca2+ current activation and deactivation with no change in the voltage dependence of activation. Inhibition of the Ca2+ channel current by THCC and PES was voltage dependent. THCC primarily inhibits the omega-conotoxin (CgTX)-sensitive or N-type Ca2+ channel current. PE was nonselective in inhibiting both the CgTX- and the nifedipine (NIF)-sensitive Ca2+ channel current. These neurosteroids had no effect on the CgTX/NIF-insensitive current. In neurons isolated from pertussis toxin (PTX)-treated animals by chronic intracerebroventricular infusion (1000 ng/24 hr for 48 hr), the Ca2+ channel current inhibition by PES, PE, and THCC was significantly diminished. Intracellular dialysis with GDP-beta-S (500 microM) also significantly diminished the neurosteroid inhibition of the Ca2+ channel current. Intracellular dialysis with the general kinase inhibitors H-7 (100 microM), staurosporine (400 nM), and a 20 amino acid protein kinase inhibitor (1 microM) also significantly prevented the THCC and PES inhibition of the Ca2+ channel current. Intracellular dialysis with the more specific inhibitors of protein kinase C (PKC), the pseudosubstrate inhibitor (PKCI 19-36) (1-2 microM) and bisindolylmaleimide (1 microM) significantly diminished the THCC and PE inhibition of the Ca2+ channel current. Rp- cAMP (100 microM), a specific inhibitor of cAMP-dependent protein kinase (PKA), had no effect on the THCC and PE inhibition of the Ca2+ current.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Neurosteroids modulate calcium currents in hippocampal CA1 neurons via a pertussis toxin-sensitive G-protein-coupled mechanism. 815 51

Coactivation of metabotropic glutamate receptors (mGluRs) and beta-adrenergic receptors causes a synergistic increase in cAMP formation in the rat hippocampus. Increases in cAMP are known to have many actions in the hippocampus via activation of cAMP-dependent protein kinase. We now report that coactivation of mGluRs and beta-adrenergic receptors induces an acute depression of EPSCs at the Schaffer collateral-CA1 synapse. Interestingly, this depression of EPSCs is dependent upon increases in cAMP levels but independent of protein kinase activity. A series of studies suggests that cAMP-mediated depression of EPSCs is dependent on metabolism of cAMP and release of adenosine or 5'-AMP into the extracellular space with resultant activation of presynaptic adenosine receptors. These studies suggest that cAMP can have local hormone-like effects in the hippocampal formation which are independent of cAMP-dependent protein kinase.
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PMID:Potentiation of cAMP responses by metabotropic glutamate receptors depresses excitatory synaptic transmission by a kinase-independent mechanism. 818 47


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