EC:2.7.11.13 - FACTA Search

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)

Activation of protein kinase C by phorbol esters is known to accelerate the processing and secretion of the beta/A4 amyloid protein precursor. We have now examined various first messengers that increase protein kinase C activity of target cells for their ability to affect beta/A4 amyloid protein precursor metabolism. Acetylcholine and interleukin 1, which are altered in Alzheimer disease, were shown to increase processing of the beta/A4 amyloid protein precursor via the secretory cleavage pathway. Cholinergic agonists stimulated secretion in human glioma and neuroblastoma cells as well as in PC12 cells transfected with the M1 receptor, while interleukin 1 stimulated secretion in human endothelial and glioma cells.
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PMID:Cholinergic agonists and interleukin 1 regulate processing and secretion of the Alzheimer beta/A4 amyloid protein precursor. 135 34

The selective alpha 1-adrenergic agonist methoxamine (10(-4)-10(-3) M), in the presence of propranolol (10(-6) M), can reduce both the inwardly rectifying K+ background current (IK1) and the muscarinic cholinergic receptor-activated K+ current (IK,ACh) in rabbit atrial myocytes resulting in action potential prolongation during the final phase of repolarization and a depolarization of the resting membrane potential. The reduction of these K+ currents(s) by alpha 1-adrenoceptor stimulation was insensitive to pre-treatment of atrial myocytes with pertussis toxin (0.15-0.5 micrograms/ml) and was irreversible following intracellular dialysis with the non-hydrolysable guanosine triphosphate (GTP) analogue, Gpp(NH)p (1-5 x 10(-3) M). Neither the protein kinase C (PKC) inhibitors, 1((5-isoquinolinesulphonyl)-2-methylpiperoxine (H-7) (5 x 10(-5) M) and staurosporine (1 x 10(-7) M), nor "downregulation" of PKC by prolonged phorbol ester exposure (5 x 10(-7) M, for 7-8 h) had an effect on the alpha 1-adrenergic modulation of this K+ current. Under cell-attached patch-clamp conditions, bath application of methoxamine reversibly decreased acetylcholine-induced single-channel activity, thus confirming the observed reduction of the ACh-induced current under whole-cell voltage clamp. These results demonstrate that the alpha 1-adrenoceptor, once activated, can reduce current through two different inwardly rectifying K+ channels in rabbit atrial myocytes. These current changes are mediated via a pertussis toxin-insensitive GTP-binding protein, and do not appear to involve the activation of PKC.
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PMID:Activation of alpha 1-adrenoceptors modulates the inwardly rectifying potassium currents of mammalian atrial myocytes. 136 Oct 52

The role of phosphatidylinositol (PI) turnover in excitation-contraction coupling was investigated in canine antral smooth muscle. Acetylcholine (ACh; 0.1-1 microM) transiently increased tissue levels of inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] and increased the amplitudes of the plateau phase of slow waves and associated Ca2+ transients and phasic contractions. ACh also increased basal concentrations of cytosolic Ca2+ ([Ca2+]c), but these changes were not associated with an increase in resting tension. ATP (0.3 mM) had similar effects on Ins(1,4,5)P3 levels, basal [Ca2+]c, and resting tension. However, in contrast to the effects of ACh, ATP transiently reduced the amplitude of the plateau phase of slow waves and reduced the amplitudes of associated Ca2+ transients and phasic contractions. We investigated the possibility that two products of PI turnover, diacylglycerol (DAG) and Ins(1,4,5)P3, might provide negative feedback to regulate Ca2+ entry during slow waves. 1) DAG is known to activate protein kinase C (PKC). Activation of PKC by phorbol 12,13-dibutyrate (PDBu, 0.5 microM) reduced the amplitude of the plateau phase of slow waves and corresponding Ca2+ transients and phasic contractions. Assay of PKC showed that ACh, ATP, and PDBu stimulated enzyme activity. 2) Ins(1,4,5)P3 is known to increase [Ca2+]c by release of Ca2+ from internal stores. Basal [Ca2+]c was also increased by elevated external K+, ionomycin, thapsigargin, or caffeine. Each of these compounds reduced the amplitude and duration of slow waves. Results suggest that products of PI turnover may provide negative-feedback control of Ca2+ influx during slow waves, tending to reduce the amplitude of phasic contractile activity in gastric muscles. Differences in responses to ACh and ATP can be explained by a G protein-dependent mechanism in which ACh suppresses the voltage dependence of Ca(2+)-activated K+ channels.
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PMID:Negative-feedback regulation of excitation-contraction coupling in gastric smooth muscle. 147 62

The incorporation of [methyl-14C]choline into the choline-containing compounds of Ascaris suum muscle and the effects of acetylcholine and its agonists, carbachol and levamisole, on this incorporation were studied. Previous experiments reported a stimulation of phosphatidylcholine (lecithin) metabolism upon the administration of acetylcholine. Acetylcholine administered in vitro to A. suum muscle and body wall preparations resulted in a stimulation of phospholipase C activity that, in turn, produced an increased rate of hydrolysis of phosphatidylcholine to the corresponding diacylglyceride (DAG). The DAG, in turn, may act as a second messenger as it is required for the activation of an A. suum protein kinase C. Evidence presented here is in accordance with this hypothesis. The administration of cholinergics resulted in a stimulation of phosphatidylcholine turnover. Acetylcholine also stimulated isotope incorporation into glycerophosphorylcholine, presumably as a consequence of enhanced phospholipid turnover. These events appear to be associated with the ligand binding to the acetylcholine receptors of the A. suum muscle. Choline kinase activity is suggested in order to maintain the observed high ratio of phosphorylcholine to choline. Findings indicate that in the parasite's muscle phosphatidylcholine metabolism may be linked to receptor-dependent responses and subsequent signal transduction.
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PMID:Effects of cholinergic agents on the metabolism of choline in muscle from Ascaris suum. 159 77

Quantitatively, the major phospholipid in the muscle of the nematode Ascaris suum was found to be phosphatidylcholine (lecithin). Stimulation of Ascaris muscle with acetylcholine or the agonists carbachol and levamisole increased the level of phosphorylcholine, 1,2-diacylglycerides and phosphatidic acid. Increased levels of these compounds, together with the demonstration of phospholipase C activity, suggest that phospholipid hydrolysis may be associated with the ACh response of the muscle via second messenger pathways. In other tissues, diacylglycerides and phosphatidic acid have been reported to regulate protein kinase C activity. Protein kinase C activity also was demonstrated in the muscle of Ascaris. For optimal activity the kinase was dependent upon Ca2+, unsaturated 1,2-diacylglyceride and phospholipid. All of the data are in accord with the possible involvement of a second messenger system being operative in the ACh-stimulated contraction of Ascaris muscle.
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PMID:Phospholipids and protein kinase C in acetylcholine-dependent signal transduction in Ascaris suum. 176 27

1. Desensitization of the Ca2+ release response evoked by acetylcholine in acinar cells from rat lacrimal glands was studied using the Ca(2+)-sensitive dye Fura-2. The evolution of the amplitude and half-maximal rise time (t1/2) of the Ca2+ response was followed as a function of trial number in a series of stimulations. 2. Under control conditions repetitive applications of acetylcholine (15 s long applications every minute) led to a linear decrease of the amplitude and to a linear increase of t1/2 with trial number. Both amplitude and t1/2 recovered their control values after 20 min of washing. 3. Staurosporine (0.2-1 microM), an inhibitor of protein kinase C, was found to decrease the slopes of the variation of amplitude and t1/2 with trial number. 4. Prolonged treatment with 12-O-tetradecanoyl phorbol 13-acetate (TPA), an activator of protein kinase C (100-250 nM for 2-4 h), also led to a markedly decreased desensitization, presumably as a result of down-regulation of protein kinase C. On the other hand moderate pre-treatments with TPA (16-32 nM for 10 min) strongly inhibited the response, most probably as a result of protein kinase C activation. 5. Application of oleoylacetylglycerol (50 microM), a weaker activator of protein kinase C, inhibited the response and enhanced desensitization. These effects were, however, not obtained after down-regulation of protein kinase C with strong exposure to TPA. 6. We conclude that protein kinase C activation following the ACh-induced Ca2+ rise and the concomitant diacylglycerol production mediates desensitization of the response. 7. Arachidonic acid (100 microM) inhibited the ACh-induced response and enhanced desensitization. However, this effect did not appear to be mediated by protein kinase C since it was also obtained with docosahexaenoic acid, an analogue of arachidonic acid which does not activate protein kinase C.
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PMID:Protein kinase C-mediated desensitization of the muscarinic response in rat lacrimal gland cells. 184 45

Activation and inhibition of protein kinase C (PKC) has been reported to induce several effects in hippocampus in vitro. It has been also proposed that, in hippocampus, phorbol esters mimic the effects of acetylcholine. To test whether the actions produced by PKC activators and inhibitors in situ are comparable to those induced in vitro preparations, we studied, in the CA1 region of the hippocampus both in situ and in vitro, the responses produced by activation and inhibition of protein kinase C. Once the effects of various PKC activators and inhibitors were established their interaction with muscarinic agonists was studied. The main findings were as follows: I) Extracellular studies in situ: 1) Phorbol diacetate (PDAc) enhanced the population spike and dendritic field amplitudes. Unlike ACh, it never induced disfacilitation or disinhibition. 2) The effects produced by muscarinic agonists were not occluded by prolonged PDAc applications. 3) Inhibition of PKC with H-7 induced a strong excitation manifested by induction of multiple spikes and broadening of the dendritic field response. This excitation was associated with blockade of IPSPs, represented by positive waves, at a presynaptic site, which was antagonised by PDAc suggesting the involvement of PKC. 4) Sphingosine, a dual PKC/calcium-calmodulin-dependent kinase inhibitor, did not reproduce H-7-induced responses. However, it did prevent the actions of muscarinic agonists. II) Intracellular studies in vitro: 1) PDAc applications by either iontophoresis or superfusion produced a i) depolarization; ii) increase in input resistance (RN); iii) blockade of the anomalous rectification ("sag"); iv) increase in the fast--but decrease in the slow--afterhyperpolarization (AHP); and v) reduction in excitability, measured by the repetitive firing evoked by depolarizing pulses. 2) During local (iontophoretic) applications of PDAc, the reversal potential of IPSPs was not affected significantly whereas during bath applications, it shifted toward more positive values. 3) Iontophoresis of H-7 caused a decrease in RN, hyperpolarization, and blockade of IPSPs. In conclusion, in the hippocampus, PKC can modulate the IPSPs, the anomalous rectification, and the membrane potential, but PKC is unlikely to be the major intracellular mediator of the excitatory actions of acetylcholine. The possible involvement of calcium-calmodulin-dependent kinase is discussed.
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PMID:Effects of protein kinase C activators and inhibitors on membrane properties, synaptic responses, and cholinergic actions in CA1 subfield of rat hippocampus in situ and in vitro. 188 29

1. Receptor-mediated modulation of the delayed outward potassium current (IK) was investigated in guinea-pig single ventricular cells by using whole-cell voltage clamp and intracellular dialysis. 2. Isoprenaline increased IK in a dose-dependent manner with a half-maximum dose of 1.8 X 10(-8) M. Isoprenaline (10(-6) M) maximally increased IK by a factor of 2.85. This effect did not depend on the concentration of intracellular Ca2+ [( Ca2+]i). 3. External application of 10(-5) M-forskolin and internal application of 5 X 10(-5) M-cyclic AMP or 5 X 10(-6) M of the catalytic subunit of cyclic AMP-dependent protein kinase (PKA) also increased IK about 3-fold. The effect of isoprenaline on IK was masked by previous application of cyclic AMP. 4. All the above phosphorylating agents increased the amplitude of IK without a significant change in the current kinetics. 5. In the presence of 10(-5) M-forskolin, an additional application of 10(-8) M-12-O-tetradecanoylphorbol-13-acetate, an activator of protein kinase C (PKC), produced a further increase in IK, suggesting that the active sites of PKA and PKC on the IK channel are different. 6. Acetylcholine (10(-6) M) suppressed IK when the current was previously enhanced by 2 X 10(-8) M-isoprenaline, but had little effect in the absence of isoprenaline. 7. We conclude that beta-adrenergic modulation of IK is mediated by cyclic AMP-dependent phosphorylation but not by an increase in [Ca2+]i, that PKA and PKC enhance IK independently, and that acetylcholine antagonizes beta-adrenergic stimulation of IK most probably by inhibiting adenylate cyclase.
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PMID:Mechanism of receptor-mediated modulation of the delayed outward potassium current in guinea-pig ventricular myocytes. 216 57

1. Phorbol esters are known to inhibit phospholipase C-mediated hydrolysis of membrane phosphoinositide. This inhibition is attributed to participation of protein kinase C (PKC) in a negative-feedback control of phosphoinositide metabolism. We have tested this hypothesis by using different types of activators and inhibitors of PKC. 2. Phorbol-12,13-dibutyrate (PDB) inhibited the stimulatory effect of acetylcholine (ACh) on [3H]inositol monophosphate ([3H]IP) formation in cultured sympathetic neurons of the chick embryo and adrenal medulla of the rat. 3. Acetylcholine (ACh) and 5-hydroxytryptamine (5-HT) activated neuronal PKC by 3- to 8-fold. The extent of PKC activation by 100 microM-ACh was comparable to that of 100 nM-PDB. Activation of PKC by pre-incubation of sympathetic neurons with ACh (or 5-HT) did not inhibit the stimulatory effects of ACh (or 5-HT) on [3H]IP formation. 4. Pre-treatment of sympathetic neurons or adrenal medulla with a PKC inhibitor H7 (1-(5-isoquinolinyl-sulphonyl)-2-methyl-piperazine) almost completely blocked activation of the enzyme induced by PDB, ACh or 5-HT. However, blockade of PKC did not prevent the inhibitory effects of PDB on ACh-induced [3H]IP formation. 5. Vasoactive intestinal polypeptide (VIP) and muscarine induced catecholamine secretion from the perfused adrenal medulla via formation of inositol-1,4,5-tirisphosphate (IP3). Phorbol-12,13-dibutyrate decreased muscarine-induced catecholamine secretion. However, activation of PKC by VIP had no effect on muscarine-induced catecholamine secretion and vice versa. 6. These results suggest that PKC is not negatively coupled to phosphoinositide hydrolysis in sympathetic neurons and chromaffin cells. Phorbol esters must have targets other than PKC to interfere with the phosphoinositide hydrolysis.
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PMID:Phosphoinositide hydrolysis is not negatively regulated by protein kinase C in the peripheral tissues of rat and chick. 217 Jun 29

The effects of the phorbol ester, 12-tetradecanoyl-phorbol-13-acetate (TPA) and related compounds on acetylcholine (ACh)-evoked [3H]leucine-labelled protein release (secretion) were tested in isolated permeabilized rat pancreatic acini. The aim was to determine whether the diacylglycerol-like compounds can still potentiate the actions of ACh during unfluctuating supramaximal elevation of cytosolic free calcium (Ca2+) levels. TPA and R59022, an inhibitor of diacylglycerol kinase, evoked marked biphasic dose-dependent increases in 3H-labelled protein secretion from permeabilized rat pancreatic acini. Synthetic diacylglycerol (OAG) and 8-bromo cyclic GMP elicited small increases in 3H-labelled protein release while an inactive phorbol ester (4 alpha-phorbol-12,13-didecanoate; 4 alpha-PDD) and polymyxin B, an inhibitor of protein kinase C, were unable to stimulate secretion. Combining polymyxin B with TPA resulted in an inhibition of 3H-labelled protein secretion. Acetylcholine also induced a dose-dependent increase in 3H-labelled protein output, but when TPA or R59022 was combined with ACh, there was a marked potentiation of the ACh-evoked secretory response, particularly at higher concentrations of ACh. This synergism was unaffected by the protein kinase C inhibitor, polymyxin B. The results show that cytosolic free Ca2+ and protein kinase C may not be the only mediators of ACh-evoked secretion. Moreover, they indicate that protein kinase C may not be involved in the potentiation by TPA of ACh-evoked 3H-labelled protein release.
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PMID:Effects of phorbol ester and related compounds on acetylcholine-evoked [3H]leucine-labelled protein secretion in permeabilized rat pancreatic acini. 217 84

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