Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.13 (protein kinase C)
 49,245 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In rat hippocampal slices and in neurons in primary culture, K(+)-induced depolarization increased markedly and rapidly tyrosine phosphorylation of a 110-kDa protein (pp110) and, to a lesser degree, of a 120-kDa protein (pp120), in a calcium-dependent fashion. Glutamate, 1-aminocyclopentane-trans-1,3-dicarboxylic acid (an agonist of metabotropic glutamate receptors), and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (an agonist of ionotropic glutamate receptors) stimulated also tyrosine phosphorylation of pp110 and pp120. These effects were not observed in astrocytes in primary culture. In hippocampal slices tyrosine phosphorylation of pp110 and pp120 was stimulated by Ca(2+)-ionophores and by phorbol esters and antagonized by a chelator of intracellular Ca2+ and by drugs that inhibit protein kinase C. Stimulation of muscarinic and alpha 1-adrenergic receptors increased also tyrosine phosphorylation of pp110 and pp120. These results demonstrate that membrane depolarization and stimulation of neurotransmitter receptors activate a tyrosine phosphorylation pathway in neurons. This pathway involves an increase in intracellular Ca2+ concentrations and the activation of protein kinase C. It may provide a biochemical basis for some neurotrophic effects of electrical activity and neurotransmitters and may contribute to the role of tyrosine phosphorylation in long-term potentiation.
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PMID:Depolarization and neurotransmitters increase neuronal protein tyrosine phosphorylation. 750 78

Phosphorylation of glutamate receptors (GluRs) is emerging as an important regulatory mechanism. In this study 32P labeling of non-NMDA GluRs was investigated in cultured hippocampal neurons stimulated 2-15 min with agonists that selectively stimulate either Ca2+/calmodulin-dependent protein kinase II (CaM-kinase II), Ca2+/phospholipid-dependent protein kinase C (PKC), or cAMP-dependent protein kinase A (PKA). Treatment of hippocampal neurons with glutamate/glycine (Glu/Gly), ionomycin, or 12-O-tetradecanoylphorbol 13-acetate (TPA) increased 32P labeling of immunoprecipitated alpha-amino-3-hydroxy-5-methyl-4-isoxazoleproprionate (AMPA)-type GluRs by 145%, 180%, and 227%, respectively, of control values. This increased phosphorylation of GluRs was predominantly 32P-Ser with little 32P-Thr and no detectable 32P-Tyr. Glu/Gly and ionomycin, but not TPA, also increased 32P labeling of CaM-kinase II by 175% and 195%, respectively, of control values. Of these three agonists, only TPA stimulated phosphorylation of MARCKS (225% of control), a specific substrate of PKC. Forskolin treatment gave a three- to fourfold increase in the active catalytic subunit of PKA but did not result in the 32P labeling of AMPA-type GluRs, CaM-kinase II, or MARCKS. Phosphorylation of GluRs in response to Glu/Gly was blocked by a specific NMDA receptor/ion channel antagonist (DL-2-amino-5-phosphonovaleric acid) or by a cell-permeable inhibitor of CaM-kinase II (1-[N,O-bis(1,5-isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4- phenylpiperazine, KN-62). These results are consistent with the hypothesis that Ca2+ influx through the NMDA-type ion channel can activate CaM-kinase II, which in turn can phosphorylate and regulate AMPA-type GluR ion channels (McGlade-McCulloh et al., 1993).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Phosphorylation of AMPA-type glutamate receptors by calcium/calmodulin-dependent protein kinase II and protein kinase C in cultured hippocampal neurons. 750 63

Activation of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptor increases levels of intracellular calcium and can lead to stimulation of protein kinase C activity. Several reports have demonstrated that stimulation of protein kinase C can, in turn, increase electrophysiological responses to NMDA in certain cells or in oocytes expressing certain NMDA receptor subunits. In the present study, the effects of protein kinase C activation on NMDA receptor-mediated increases in intracellular Ca2+ level were investigated in primary cultures of rat cerebellar granule cells using fura-2 fluorescence spectroscopy. Pretreatment of the cells with the protein kinase C activator phorbol 12-myristate 13-acetate (PMA), but not the inactive analogue 4 alpha-phorbol 12-myristate 13-acetate, inhibited NMDA-induced increases in intracellular Ca2+ levels. Coincubation of cells with PMA and the kinase inhibitor staurosporine or calphostin C blocked the PMA effect. The potency of NMDA was reduced twofold, and the potency of the NMDA receptor co-agonist, glycine, to enhance the response to NMDA was decreased fourfold by pretreatment of cells with PMA. The effect on glycine was mimicked by pretreatment with okadaic acid, a protein phosphatase inhibitor. PMA treatment did not significantly alter Mg2+ inhibition of the NMDA response but decreased the potency of the competitive antagonist CGS-19755. These data suggest that, in cerebellar granule cells, the function of the NMDA receptor may be subject to feed-back inhibition by protein kinase C stimulation. Under physiological conditions, this inhibition may result from a decreased effectiveness of the endogenous co-agonists, glutamate and glycine.
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PMID:Protein kinase C activation attenuates N-methyl-D-aspartate-induced increases in intracellular calcium in cerebellar granule cells. 751 17

The contribution of the intracellular messengers nitric oxide, arachidonic acid and protein kinase C to persistent nociception in response to tissue injury in rats was examined following the subcutaneous injection of formalin into the hindpaw. Formalin injury-induced nociceptive behaviours were reduced by intrathecal pretreatment with inhibitors of nitric oxide synthase (NG-nitro-L-arginine methyl ester, L-NAME), arachidonic acid (dexamethasone) or protein kinase C [protein kinase C (19-26) and 1-95-(isoquinolinesulphonyl)-2-methylpiperazine dihydrochloride, H-7]. Each of these agents affected the tonic, but not the acute, phase of the formalin response. Furthermore, none of these agents affected mechanical or thermal flexion reflex thresholds in rats not injected with formalin. Conversely, formalin-induced nociceptive responses were enhanced by stimulators of nitric oxide (sodium nitroprusside), arachidonic acid metabolism (arachidonic acid) or protein kinase C [(+/-)-1-oleoyl-2-acetyl-glycerol], and were slightly reduced by inositol trisphosphate. Mechanical flexion reflexes were also reduced by arachidonic acid, while thermal flexion reflexes were reduced after treatment with sodium nitroprusside, arachidonic acid or [(+/-)-1-oleoyl-2-acetyl-glycerol]. The enhancement of formalin nociceptive behaviours (hyperalgesia) in rats treated with L-glutamate or substance P was reversed by pretreatment with inhibitors of nitric oxide (L-NAME), arachidonic acid (dexamethasone) or protein kinase C (H-7). The results suggest that central sensitization and persistent nociception following formalin-induced tissue injury, and the hyperalgesia in the formalin test induced by L-glutamate and substance P, are dependent on the intracellular messengers nitric oxide, arachidonic acid and protein kinase C.
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PMID:Intracellular messengers contributing to persistent nociception and hyperalgesia induced by L-glutamate and substance P in the rat formalin pain model. 752 41

Glutamate-gated ion channels mediate most excitatory synaptic transmission in the mammalian central nervous system and play major roles in synaptic plasticity, neuronal development, and in some neuropathological conditions. Recent studies have suggested that protein phosphorylation of neuronal glutamate receptors by cyclic AMP-dependent protein kinase (PKA) and protein kinase C (PKC) may regulate their function and play a role in some forms of synaptic plasticity. To test whether these protein kinase effects are due to direct phosphorylation of the receptors and to further examine the sites and mechanisms by which the receptors are modulated, we transiently expressed recombinant glutamate receptors in HEK-293 cells and studied their biochemical and biophysical properties. Our results indicate that the kainate-preferring receptor GluR6 is phosphorylated by PKA, primarily on a single serine in the proposed major intracellular loop. Moreover, using the whole cell patch clamp recording technique, we have shown that phosphorylation at this site increases the amplitude of the GluR6-mediated glutamate current without significantly altering its dose-response, current-voltage relation or desensitization kinetics. In other experiments, we have demonstrated that the NMDA receptor subunit NR1 is phosphorylated by PKC on several distinct sites, and most of these sites are located within a single alternatively spliced exon in the C-terminal domain. These findings suggest that RNA splicing can regulate NMDA receptor phosphorylation and that, contrary to the previously proposed membrane topology model, the NR1 C-terminus is intracellular. Furthermore, in HEK-293 cells co-transfected with NR2A and NR1 subunits containing the C-terminal exon with the PKC phosphorylation sites, our preliminary studies indicate that the NMDA-evoked current is potentiated by intracellular PKC. We are currently examining PKC effects on the NMDA-evoked current responses of mutant NR1 receptors that lack the C-terminal phosphorylation sites. These studies provide evidence that glutamate receptors are directly phosphorylated and functionally modulated by protein kinases. Moreover, by identifying phosphorylation sites within the receptor proteins, our results provide information about the structure and membrane topology of these receptors.
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PMID:Glutamate receptor modulation by protein phosphorylation. 753 May 47

Recombinant alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)/kainate receptors expressed in oocytes are inhibited by ethanol and the sensitivity to ethanol depends on the kainate concentration and the subunit(s) expressed. For example, GluR3 kainate channels are more sensitive to inhibition by ethanol than GluR6 channels in the presence of maximally effective kainate concentrations. To determine if the ethanol inhibition was influenced by the cation permeability (Na+ vs Na+ and Ca2+) of the channels expressed, we compared ethanol inhibition of Ca(2+)-permeable glutamate receptors (GluRs) in oocytes perfused with normal- and high-Ca2+ buffers. The ethanol inhibition was much greater when Ca2+ was the only permeant cation. When Ba2+ was substituted for Ca2+, the ethanol inhibition was reduced, although it was still greater than with normal buffer. The enhanced ethanol inhibition of kainate-stimulated Ca2+ currents was reduced in oocytes injected with the Ca2+ chelator BAPTA, suggesting a role for intracellular Ca2+ in mediating enhanced ethanol sensitivity of kainate channels. The enhanced ethanol inhibition of Ca2+ currents was not due to a direct ethanol inhibition of Ca(2+)-stimulated Cl- currents in the oocyte because ethanol produced no effect on Ca(2+)-stimulated Cl-currents induced by injection of myo-inositol-1,4,5-trisphosphate. Because Ca2+ activates protein kinase C (PKC) and because we found that the PKC activator phorbol 12-myristate 13-acetate inhibits kainate responses (Dildy-Mayfield and Harris, 1994), we examined the role of PKC in mediating the enhanced ethanol inhibition of kainate responses produced by increased Ca2+. Inhibition of PKC by injection of the PKC inhibitor peptide or calphostin C prevented the enhanced ethanol inhibition of kainate-induced Ca2+ responses without altering ethanol inhibition in normal buffer. Thus, ethanol inhibition of kainate channels may involve two mechanisms, one that is independent of PKC and a second type that is due to activation of PKC under conditions of elevated Ca2+, resulting in enhanced inhibition of kainate responses.
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PMID:Ethanol inhibits kainate responses of glutamate receptors expressed in Xenopus oocytes: role of calcium and protein kinase C. 753 28

Effects of L-glutamate (Glu), the neurotransmitter released by photoreceptors, on isolated cat bipolar cells were examined. Membrane currents of bipolar cells were recorded by the patch-clamp technique in a conventional whole-cell recording configuration using pipettes containing 1 mM cGMP, which has been known to activate a cationic current sensitive to Glu in ON-type bipolar cells. ON-type bipolar cells (depolarized by light in in situ) and OFF-type bipolar cells (hyperpolarized by light) were identified by their response polarity to Glu. When the whole-cell configuration was established, ON-type bipolar cells showed a steady inward current which was suppressed by Glu, consistent with the response polarity observed in in situ recordings. In contrast, OFF-type cells did not show a steady current during the recordings. However, they responded to Glu with an increase in cationic conductance. Among recorded cells, rod-driven bipolar cells were identified by their immunoreactivity to anti-protein kinase C (PKC-IR) antibody. Examination of PKC-IR revealed that ON-type bipolar cells included both rod- and cone-driven bipolar cells, while OFF-type cells were all cone-driven bipolar cells. The cGMP-activated current observed in ON-type cells was accompanied by a change in the current fluctuation due to the opening and closing of underlying channels. Fluctuation analysis gave a unitary conductance value of 13 pS. In half of the cells examined, maximum open probability reached almost 100%. The cGMP-activated channel in bipolar cells seems novel, fundamentally different from those found in photoreceptor cells or olfactory receptor cells.
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PMID:L-glutamate-induced responses and cGMP-activated channels in three subtypes of retinal bipolar cells dissociated from the cat. 753 64

The stimulation of [3H] inositol phosphate (InP) formation by the selective metabotropic-glutamate receptor agonist, 1S, 3R-ACPD, was significantly reduced in rat cortical astrocytes chronically exposed to 100 mM ethanol for 4 days. Under the same conditions, chronic ethanol either increased or did not affect the InP responses to norepinephrine and carbachol, respectively. The InP responses to all three agonists were sensitive to phorbol 12-myristate 13-acetate. Although the protein kinase C inhibitors, calphostin C and staurosporine, significantly relieved the ethanol induced inhibtion of the InP response to 1S, 3R-ACPD, these responses were still significantly less than corresponding values obtained from control cells treated with these inhibitors. The data suggests that mechanisms in addition to protein kinase C are responsible for the ethanol induced inhibition of metabotropic-glutamate function.
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PMID:Lack of involvement of protein kinase C in ethanol-induced inhibition of metabotropic-glutamate receptor function in primary cultures of astrocytes. 754 Jul 11

Our previous work using Na+ channel activators such tityustoxin (TsTX), indicated that local increases in Na+ modulate glutamate release from synaptosomes. We have now investigated the role of the Ca2+/phospholipid-dependent protein kinase (PKC) in mediating this effect. TsTX and KCl stimulate 'fast' glutamate release to the same extent but TsTX is more effective than KCl in enhancing the 'slow' phase of release. KCl greatly stimulates PKC translocation. However, TsTX inhibits basal and phorbol ester-induced translocation while the Na(+)-ionophore, gramicidin D, has no effect. Taken together, these data suggest TsTX mediated localized Na+ entry inhibits PKC translocation and that this effect may be associated with recruitment of vesicles to the readily releasable pool.
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PMID:Effects of sodium on PKC translocation; relationship to neurotransmitter release. 754 58

The potential involvement of platelet activating factor (PAF, 1-O-alkyl 2-O-acetyl-sn-glycero-3-phosphocholine) in aggravation of ischemic brain injury has been recently postulated. Reported evidences in support of this thesis include increases of brain PAF concentration during ischemia and the neuroprotective effect exerted by PAF antagonists. In this article, we demonstrate that several PAF-mediated biochemical responses in synaptoneurosomes in vitro resemble these observed previously in ischemic brain and are widely acknowledged as the potentially causal factors in this pathology. In synaptoneurosomes prepared from rat hippocampus, 10 nM PAF caused an observable elevation of intracellular calcium as measured by fluorescence Fura-2A probe. A similar elevation of synaptoneurosomal [Ca2+]i was evoked by 1 mM glutamate treatment. As an effect of calcium entry after PAF application, a translocation of protein kinase C (PKC) toward plasma membranes was demonstrated by 3H-labeled phorbol-binding method. It was followed by an increase of 50 kDa proteolytic fragment of the enzyme (PKM) recognized on Western blots with anti-PKC antibody. Incubation of synaptoneurosomes in the presence of calcium chelators abolished these effects of PAF and significantly decreased the content of PKC in the membranes. Furthermore, PAF treatment markedly attenuated the receptor- and postreceptor-activated cAMP accumulation in synaptoneurosomes. The decrease of cAMP level seems to be secondary to the PAF-induced calcium entry with subsequent activation of cAMP-specific phosphodiesterase, since it was completely blocked by IBMX, a potent inhibitor of this enzyme. Our observations indicate that PAF in a concentration found in ischemic brain can elevate [Ca2+]i and potentiate calcium-dependent intracellular signalling in synaptoneurosomes in vitro, including PKC translocation/activation and proteolysis, followed by IBMX-sensitive inhibition of cAMP production. The relative contribution of these events to ischemic brain injury is currently under extensive investigation.
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PMID:Modulation of signal transduction in rat synaptoneurosomes by platelet activating factor. 754 18


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