Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.11.1 (protein kinase)
81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rat brain synaptosomes were isolated to study the effects of protein kinase inhibitors (sphingosine, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride, N-(6-aminohexyl)-5-chloro-1-naphtalenesulfonamide, staurosporine) on Ca2+-dependent and Ca2+-independent [14C]GABA release. The Ca2+-dependent [14C]GABA release was stimulated by depolarization with a K+-channel blocker, 4-aminopyridine, or high K+ concentration. It has been shown that 4-aminopyridine-evoked [14C]GABA release strongly depends on extracellular Ca2+ while K+-evoked [14C]GABA release only partly decreases in the absence of calcium. The substitution of sodium by choline in Ca2+-free medium completely abolished Ca2+-independent part of K+-evoked [14C]GABA release. So the main effect of 4-aminopyridine is the Ca2+-dependent one while high K+ is able to evoke [14C]GABA release in both a Ca2+-dependent and Na+-dependent manner. In experiments with protein kinase inhibitors, 4-aminopyridine and high K+ concentration were used to study the Ca2+-dependent and the Ca2+-independent [14C]GABA release, respectively. In addition, the Ca2+-independent [14C]GABA release was studied using alpha-latrotoxin as a tool. Pretreatment of synaptosomes with protein kinase inhibitors tested, except of 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride, resulted in a marked inhibition of 4-aminopyridine-stimulated Ca2+-dependent [14C]GABA release. The inhibitory effects of N-(6-aminohexyl)-5-chloro-1-naphtalenesulfonamide and staurosporine on [14C]GABA release were not due to their effects on 4-aminopyridine-promoted 45Ca2+ influx into synaptosomes. Only sphingosine (100 microM) reduced the 45Ca2+ influx. All the inhibitors investigated were absolutely ineffective in blocking the Ca2+-independent [14C]GABA release stimulated by alpha-latrotoxin. Three of them, except for sphingosine, did not affect the Ca2+-independent [14C]GABA release stimulated by high potassium. The inhibitory effect of sphingosine was equal to 30%. Thus, if [14C]GABA release occurred in a Ca2+-independent manner irrespective of whether alpha-latrotoxin or high K+ stimulated this process, it was not inhibited by the drugs decreased the Ca2+-dependent [14C] GABA release. Given the above points it is therefore not unreasonable to assume that the absence of Ca2+ in the extracellular medium created the conditions in which the activation of neurotransmitter release was not accompanied by Ca2+-dependent dephosphorylation of neuronal phosphoproteins, and as a consequence the regulation of exocytotic process was modulated so that the inhibition of protein kinases did not disturb the exocytosis.
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PMID:Differential effect of protein kinase inhibitors on calcium-dependent and calcium-independent [14C]GABA release from rat brain synaptosomes. 963 90

The mechanism through which kainate receptors downregulate the release of GABA in the hippocampus is not known. We have found that the action of kainate on the hippocampal inhibitory postsynaptic current (IPSC) is mediated by a metabotropic process that is sensitive to Pertussis toxin (PTx) and independent of ion channel current. The downregulation of GABA IPSCs by kainate was also prevented in a dose-dependent manner by calphostin C, a specific inhibitor of PKC, and the inhibition of phospholipase C (PLC) drastically reduced the action of kainate. The effect of kainate was completely occluded by phorbol esters and by increasing extracellular Ca2+ but remained unaltered after inhibition or activation of protein kinase A (PKA). These results demonstrate that the activation of kainate receptors triggers a second messenger cascade, which results in the stimulation of PKC, and therefore document a metabotropic action of kainate receptors, which results in the inhibition of GABA release.
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PMID:Kainate receptor modulation of GABA release involves a metabotropic function. 965 8

Intracellular and patch clamp recording techniques were used to investigate the role of GABA in immature CA3 hippocampal neurons. During the first postnatal week spontaneous GABA release was detected as spontaneous ongoing synaptic potentials (SPSPs) or giant depolarizing potentials (GDPs). GDPs were generated at regular intervals and regulated by ionotropic glutamate receptors (GluRs), whereas SPSPs occurred randomly and were unaffected by ionotropic GluRs. Both GDPs and SPSPs were positively modulated by metabotropic GluRs through cyclic AMP-dependent protein kinase. Moreover GABA controlled its own release through GABAA and GABAB receptors, probably localized on GABAergic nerve terminals. At this developmental stage, GABA depolarized CA3 pyramidal cells through two distinct classes of chloride-permeable receptors: bicuculline sensitive and insensitive, respectively. The bicuculline-insensitive responses were blocked by picrotoxin in a noncompetitive way. Whole-cell GABA currents, recorded in the presence of bicuculline, had a slower desensitization rate and faster recovery from desensitization. In excised outside-out patches, in the presence of bicuculline, GABA activated single-channel currents with conductances of 14, 22, and 31 pS. These values were similar to those obtained when GABA was applied in the absence of bicuculline. Interestingly, GABA responses obtained in the absence of bicuculline, were sensitive to the blocking effect of zinc, whereas bicuculline-resistant responses were almost unaffected by this divalent cation. Expression of different subunits in native receptors (particularly of the alpha and rho type) may account for the functional differences observed in the present experiments. Activation of bicuculline-insensitive receptors would strengthen and prolong the depolarizing action of GABA, thus favoring the entry of calcium through voltage-dependent calcium channels. This calcium signal may be essential in promoting stabilization of synaptic contacts during a critical period of postnatal development.
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PMID:GABA excites immature CA3 pyramidal cells through bicuculline-sensitive and -insensitive chloride-dependent receptors. 977 44

Chronic morphine administration induces adaptations in neurons resulting in opioid tolerance and dependence. Functional studies have implicated a role for the periaqueductal gray area (PAG) in the expression of many signs of opioid withdrawal, but the cellular mechanisms are not fully understood. This study describes an increased efficacy, rather than tolerance, of opioid agonists at mu-receptors on GABAergic (but not glutamatergic) nerve terminals in PAG after chronic morphine treatment. Opioid withdrawal enhanced the amplitudes of electrically evoked inhibitory synaptic currents mediated by GABAA receptors and increased the frequency of spontaneous miniature GABAergic synaptic currents. These effects were not blocked by 4-aminopyridine or dendrotoxin, although both Kv channel blockers abolish acute opioid presynaptic inhibition of GABA release in PAG. Instead, the withdrawal-induced increases were blocked by protein kinase A inhibitors and occluded by metabolically stable cAMP analogs, which do not prevent acute opioid actions. These findings indicate that opioid dependence induces efficacious coupling of mu-receptors to presynaptic inhibition in GABAergic nerve terminals via adenylyl cyclase- and protein kinase A-dependent processes in PAG. The potential role of these adaptations in expression of withdrawal behavior was supported by inhibition of enhanced GABAergic synaptic transmission by the alpha2 adrenoceptor agonist clonidine. These findings provide a cellular mechanism that is consistent with other studies demonstrating attenuated opioid withdrawal behavior after injections of protein kinase A inhibitors into PAG and suggest a general mechanism whereby opioid withdrawal may enhance synaptic neurotransmission.
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PMID:Enhanced opioid efficacy in opioid dependence is caused by an altered signal transduction pathway. 985 64

Rat cerebellar granule cells GABA(A) receptors were studied at the single-channel level in outside-out patches. Three conductance levels were detected as activated by 0.1 microM GABA: 11, 20 and 30 pS. Single-channel I-V relationships were linear. The probability of opening did not vary over time within single patches. Kinetic analysis brought to a mean open time constant of 3.2, 2.9 and 2.8 ms respectively for each conductance level and a closed time histogram fitted by the sum of two exponential functions (tau c1 = 2.1 ms, 43%; tau c2 = 18.2 ms, 57%). Protein kinase G (PKG) activation did not affect single-channel conductances, but resulted in a reduction over time of single-channel open probability for all the conductance levels. Kinetically, protein kinase G modified the mean open time constants and the relative areas of the two components of the closed state distribution whereas the mean closed time constants remained unaffected. These results confirm and add details about cerebellar granule GABA(A) receptors down regulation by PKG.
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PMID:Cerebellar granule cell GABA(A) receptors studied at the single-channel level: modulation by protein kinase G. 991 2

(1) The interaction of substance P (SP)-mediated synaptic transmission with general anesthetics remains unknown. (2) Intracellular recordings were obtained from guinea-pig inferior mesenteric ganglion neurons to study monosynaptic responses to exogenous SP and GABA. (3) Propofol (1-100 microM) caused an increase in SP-evoked inward current responses and a concurrent decrease in peak amplitude of the afterspike hyperpolarization of intermittently evoked action potentials. These effects were occluded by the (BK)-K+-channel-selective blocker charybdotoxin (10 nM), and prevented by the protein kinase inhibitor staurosporine (100 nM). (4) Propofol also increased GABA-evoked current (I(GABA)) responses. (5) When elicited during a SP response, I(GABA) was significantly diminished compared to control. In the presence of staurosporine (100 nM), the inhibitory effect of SP upon I(GABA) was abolished, and the propofol-induced augmentation of I(GABA) was significantly increased. (6) Thus, SP-evoked protein kinase activity produced reciprocal changes in anesthetic sensitivity of (BK)-K+- and GABA A-receptor-gated currents of these sympathetic neurons.
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PMID:Protein kinase-mediated reciprocal modulatory changes in anesthetic sensitivity of (BK)-K+- and GABA-A receptor-gated conductances in guinea-pig sympathetic neurons. 1004 88

The gamma-aminobutyric acid type A (GABAA) receptor is the predominant Cl- channel protein mediating inhibition in the olfactory bulb and elsewhere in the mammalian brain. The olfactory bulb is rich in neurons containing both GABA and dopamine. Dopamine D1 and D2 receptors are also highly expressed in this brain region with a distinct and complementary distribution pattern. This distribution suggests that dopamine may control the GABAergic inhibitory processing of odor signals, possibly via different signal-transduction mechanisms. We have observed that GABAA receptors in the rat olfactory bulb are differentially modulated by dopamine in a cell-specific manner. Dopamine reduced the currents through GABA-gated Cl- channels in the interneurons, presumably granule cells. This action was mediated via D1 receptors and involved phosphorylation of GABAA receptors by protein kinase A. Enhancement of GABA responses via activation of D2 dopamine receptors and phosphorylation of GABAA receptors by protein kinase C was observed in mitral/tufted cells. Decreasing or increasing the binding affinity for GABA appears to underlie the modulatory effects of dopamine via distinct receptor subtypes. This dual action of dopamine on inhibitory GABAA receptor function in the rat olfactory bulb could be instrumental in odor detection and discrimination, olfactory learning, and ultimately odotopic memory formation.
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PMID:Dopamine receptor subtypes modulate olfactory bulb gamma-aminobutyric acid type A receptors. 1005 64

Activation of cAMP-dependent protein kinase (PKA) can enhance or reduce the function of neuronal GABAA receptors, the major sites of fast synaptic inhibition in the brain. This differential regulation depends on PKA-induced phosphorylation of adjacent conserved sites in the receptor beta subunits. Phosphorylation of beta 3 subunit-containing receptors at S408 and S409 enhanced the GABA-activated response, whereas selectively mutating S408 to alanine converted the potentiation into an inhibition, comparable to that of beta 1 subunits, which are phosphorylated solely on S409. These distinct modes of regulation were interconvertible between beta 1 and beta 3 subunits and depended upon the presence of S408 in either subunit. In contrast, beta 2 subunit-containing receptors were not phosphorylated or affected by PKA. Differential regulation by PKA of postsynaptic GABAA receptors containing different beta subunits may have profound effects on neuronal excitability.
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PMID:Adjacent phosphorylation sites on GABAA receptor beta subunits determine regulation by cAMP-dependent protein kinase. 1019 4

17Beta-estradiol (E2) rapidly (<20 min) attenuates the ability of mu-opioids to hyperpolarize guinea pig hypothalamic neurons. We have used intracellular recordings from female guinea pig hypothalamic slices to characterize the receptor and intracellular pathway(s) mediating E2's rapid effects. E2 acts stereospecifically with physiologically relevant concentration-dependence (EC50 = 8 nM) to cause a fourfold reduction in the potency of the mu-opioid agonist (D-Ala2-N-Me-Phe4-Gly5-ol)-enkephalin and the GABA(B) agonist baclofen to activate an inwardly rectifying K+ conductance in hypothalamic neurons. Both the nonsteroidal estrogen diethylstilbestrol and the anti-estrogen ICI 164,384 blocked E2 actions to uncouple mu-opioid receptors. Using a pharmacological Schild analysis, we found that ICI 164,384 competed for this E2 receptor with a Ke of approximately 0.3 nM. The protein synthesis inhibitor cycloheximide did not block the estrogenic uncoupling of the mu-opioid receptor from its K+ channel, implying a rapid, nongenomic mechanism of E2 action. The effects of E2 were mimicked by the bath application of the protein kinase A (PKA) activators, forskolin and Sp-cAMP, and the protein kinase C (PKC) activator phorbol-12,13-dibutyrate. Furthermore, the selective PKA antagonists Rp-cAMP and KT5720, which have different chemical structures and modes of action, both blocked the effects of E2. In addition, the actions of E2 were blocked by the selective PKC inhibitor Calphostin C. Therefore, it appears that E2 can activate both PKA and PKC to cause a heterologous desensitization of both mu-opioid and GABA(B) receptors, which has the potential to alter synaptic transmission in many regions of the CNS.
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PMID:Rapid effects of estrogen to modulate G protein-coupled receptors via activation of protein kinase A and protein kinase C pathways. 1032 74

Long-term facilitation of neurotransmission by monoaminergic systems is implicated in the cellular mechanism of memory and learning-related processes at invertebrate synapses. Using whole-cell recording and rat cerebellar slices, we have examined whether mammalian monoamine-containing neurons play analogous roles in synaptic plasticity, and our results suggest that serotonin and noradrenaline are critically involved in short- and long-term modulation of GABAergic transmission in the cerebellar cortex. Exogenously applied serotonin and noradrenaline selectively induced a short-term enhancement of GABAergic transmission between cerebellar interneurons and Purkinje cells, their effect subsiding in 30 min. Successive amine applications converted this effect to long-term facilitation lasting more than 2 h. During the monoamine-induced short- and long-term facilitation, spontaneously occurring miniature inhibitory synaptic responses increased in frequency, without significant changes in their mean amplitude and amplitude distribution, as well as the GABA receptor sensitivity of Purkinje cells. The actions of the two amines on the inhibitory transmission were mimicked by forskolin and blocked by kinase inhibitors, H-7, H-89 and Rp-adenosine 3',5'-cyclic monophosphothioate. Thus, serotonin and noradrenaline are likely to activate cyclic-AMP- and protein kinase-dependent pathways in GABAergic interneurons, thereby reinforcing the inhibitory transmission on to Purkinje cells. Repetitive electrical stimulation within the molecular layer mimicked the facilitatory effect induced by exogenous monoamines: namely, neural stimulation selectively elicited long-lasting enhancement of GABAergic transmission in a manner sensitive to the monoamine receptor antagonists, methiothepin and propranolol, and an uptake inhibitor, imipramine. Synaptically released monoamines thus appear to induce cyclic-AMP- and protein kinase-dependent long-term facilitation of cerebellar GABAergic transmission, thereby providing a likely mechanism of synaptic plasticity associated with motor coordination within the mammalian cerebellar system.
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PMID:Monoaminergic long-term facilitation of GABA-mediated inhibitory transmission at cerebellar synapses. 1036 24


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