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)

We used the alkylating agent N-ethylmaleimide in order to investigate G-proteins linked to release-modulating prejunctional receptors of sympathetic nerves in mouse atria incubated with [3H]-noradrenaline. The receptors tested were facilitatory beta-adrenoceptors and angiotensin II receptors and inhibitory neuropeptide Y receptors. In order to evaluate the specificity of the N-ethylmaleimide treatment, we tested N-ethylmaleimide against the second messenger pathways that are linked to beta-adrenoceptors (adenylate cyclase) and angiotensin II (protein kinase C). The results show that a 60-min preincubation with N-ethylmaleimide (3 microM) abolished the facilitatory effect of isoprenaline (0.1 microM) and angiotensin II (0.1 microM) on the stimulation-induced release of noradrenaline and reduced the inhibitory action of neuropeptide Y (0.3 microM). N-ethylmaleimide had no effect on the stimulatory action of either phorbol dibutyrate (0.01, 0.1 microM), forskolin (10 microM), or a combination of 8-bromo adenosine-3'5'-monophosphate (90 microM) and 3-isobutyl-1-methylxanthine (100 microM). However, at a higher concentration (10 microM), N-ethylmaleimide reduced the facilitatory effect of phorbol dibutyrate (0.1 microM) and the combination of 8-bromo adenosine-3',5'-monophosphate (90 microM) and 3-isobutyl-1-methylxanthine (100 microM). This suggests that N-ethylmaleimide at 3 microM but not 10 microM was selective for receptor-mediated modulation of noradrenaline release without directly affecting the adenylate cyclase (forskolin, 8-bromo adenosine-3',5'-monophosphate + 3-isobutyl-1-methylxanthine) or protein kinase C (phorbol dibutyrate) transduction pathways. In atria from mice pretreated with pertussis toxin (1.5 micrograms/mouse), N-ethylmaleimide preincubation (1 and 3 microM) resulted in a more pronounced reduction of the inhibitory action of neuropeptide Y (0.3 microM). The nature of this interaction is unclear. Since N-ethylmaleimide has been shown in other studies to inactivate G-proteins, the inhibitory effect of N-ethylmaleimide on prejunctional beta-adrenoceptors, angiotensin II receptors and neuropeptide Y receptors of sympathetic nerves may suggest that G-proteins are involved with these receptors, although other effects of N-ethylmaleimide on the receptor coupling processes cannot be ruled out. Moreover, it appears that the concentration of N-ethylmaleimide used is critical since a higher concentration (10 microM) resulted in non-specific effects on signal transduction mechanisms in the present experimental conditions.
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PMID:Prejunctional beta-adrenoceptors, angiotensin II and neuropeptide Y receptors on sympathetic nerves in mouse atria are linked to N-ethylmaleimide-susceptible G-proteins. 217 55

The role of calcium for the release of norepinephrine (NE, determined by high-pressure liquid chromatography) and neuropeptide Y (NPY, determined by radioimmunoassay) was investigated in guinea pig perfused hearts with intact sympathetic innervation. In the presence of extracellular calcium (1.85 mM), electrical stimulation of the left stellate ganglion (12 Hz, 1 min) induced a closely related release of NE and NPY with the molar ratio of approximately 400-600 (NE) to 1 (NPY). The stimulation-evoked overflow of both transmitters was dependent from the extracellular calcium concentration and was almost completely suppressed by calcium-free perfusion. The corelease of both transmitters was not affected by the L-type calcium channel blocker felodipine (1-10 microM). However, the overflow of NE and NPY was markedly attenuated by the unselective calcium antagonist flunarizine (1-10 microM) and completely prevented by the neuronal (N-type) calcium channel blockers omega-conotoxin (1-100 nM) and cadmium chloride (10-100 microM), indicating a key role for N-type calcium channels in the exocytotic release of transmitters from cardiac sympathetic nerve fibers. Possibly due to unspecific actions, such as interference with sodium channels or uptake1-blocking properties, the phenylalkylamines verapamil (0.01-10 microM) and gallopamil (1-10 microM) reduced NPY overflow with only a minor effect on NE overflow. The stimulation-induced transmitter release was increased up to twofold by activation of protein kinase C (phorbol 12-myristate 13-acetate, 3 nM-3 microM) and completely suppressed by inhibition of protein kinase C (polymyxin B, 100 microM).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Role of calcium channels and protein kinase C for release of norepinephrine and neuropeptide Y. 217 26

In this study, we investigated the possible involvement of protein kinase C in the inhibitory effect of neuropeptide Y (NPY) on the electrical stimulation-induced release of radioactivity from mouse atria incubated with [3H]-noradrenaline. The protein kinase C activators, phorbol dibutyrate (PDB, 0.001-1 mumol/l) and phorbol myristate acetate (PMA, 0.001-1 mumol/l), increased the release of noradrenaline in a concentration-dependent manner. Interestingly, the maximum effect on noradrenaline release was significantly greater for phorbol dibutyrate compared to phorbol myristate acetate. The enhancement produced by both phorbol esters was significantly reduced by the protein kinase C inhibitor, K-252a (1 mumol/l). In the presence of the concentration of either phorbol ester (PMA, 0.1 mumol/l, PDB 1 mumol/l), that was supramaximal for increasing the release of noradrenaline, NPY (0.3 mumol/l) significantly inhibited the release of noradrenaline. Moreover, in the presence of the protein kinase C inhibitors, K-252a (1 mumol/l) or polymyxin B (70 mumol/l), NPY (0.3 mumol/l) also significantly inhibited the release of noradrenaline. Therefore, it is concluded that protein kinase C is not involved in the prejunctional inhibitory effect of NPY on noradrenaline release in the mouse atria. Furthermore, since K-252a also inhibits cyclic AMP-dependent protein kinase, cyclic GMP-dependent protein kinase and myosin light chain kinase, it is likely that these kinases are also not involved in the inhibitory mechanism of NPY.
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PMID:Inhibition of noradrenaline release by neuropeptide Y does not involve protein kinase C in mouse atria. 225 91

The intracellular messengers that seem to be involved in renin secretion (RS) from juxtaglomerular cells (JG) are calcium (Ca), cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). Unlike the majority of secretory systems, an increase in intracellular Ca concentration and calmodulin and protein kinase C activation inhibit RS. The intracellular Ca concentration in JG cells can be modified if: 1) the normal mechanisms of Ca extrusion of these cells is altered; 2) the calcium output is blocked by lanthanum; 3) the function of the voltage-sensitive Ca-channels is modified; 4) uptake or liberation of Ca from endoplasmic reticulum is modified; 5) plasmatic membrane is bypassed with calcium ionophores such as A 23187. 6) JG cells are stimulated by hormones that increase Ca and activate protein kinase C such as angiotensin II, vasopressin or alpha-1 adrenergic agonists; 7) extracellular Ca concentration increases or decreases. RS is stimulated by dibutyryl cAMP, cAMP phosphodiesterase inhibitors and by hormones and agents that activate adenylate cyclase (beta adrenergic agonists, bradykinin, histamine, forskolin and ethylcarboxamide adenosine). On the contrary, RS is inhibited by hormones and agents that inhibit adenylate cyclase such as: alpha-2 adrenergic agonists, neuropeptide Y, angiotensin II and cyclohexyladenosine. Pertussis toxin increases basal RS, blocks the inhibition by agents and hormones which inhibit adenylate cyclase and potentiate the stimulation produced by beta-adrenergic agonists. In JG cells, atrial natriuretic peptide inhibits RS, increases cGMP and decreases cAMP. The increase in cGMP correlates well with the inhibition of RS.
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PMID:[Intracellular messengers in the regulation of renin secretion]. 255 Oct 26

Dorsal root ganglion (DRG) neurons cultured from neonatal rats contained high concentrations of protein kinase C (PKC). Normally, the majority of the enzyme activity was found in the cytosol and considerably less was associated with the membrane fraction. Upon incubation with the phorbol ester phorbol dibutyrate (PDBu, 10(-6) M) for 20 min, PKC activity increased in the membrane-associated fraction and decreased in the cytoplasmic fraction. Longer incubations with phorbol ester also induced a decline in membrane-associated PKC activity. If incubations were continued for periods of over 10 hr, both membrane and cytosolic PKC activity declined essentially to zero. Down-regulation of PKC had no effect on the number or affinity of 125I-neuropeptide Y (NPY) binding sites on DRG cells or on the absolute magnitude of the DRG Ca2+ current. However, the ability of NPY to inhibit the DRG Ca2+ current was greatly reduced. When sustained Ca2+ currents were evoked from depolarized holding potentials (-40 mV), all concentrations of NPY (10(-10)-10(-7) M) were less effective. In contrast, higher concentrations of NPY still blocked the transient portion of the DRG Ca2+ current evoked from hyperpolarized holding potentials. These results support the suggestion that PKC is involved in the inhibitory modulation of DRG Ca2+ currents by neurotransmitters. The precise role of PKC may vary depending on the type of Ca2+ channel involved.
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PMID:The effect of down regulation of protein kinase C on the inhibitory modulation of dorsal root ganglion neuron Ca2+ currents by neuropeptide Y. 324 35

New rod photoreceptors are added to mature teleost retinas throughout life by regulated proliferation of rod precursor cells (RPCs). In this study, candidate regulators of RPC proliferation, acidic and basic fibroblast growth factors (aFGF and bFGF; 0.1 microgram/eye), interleukin-6 (IL-6; 0.1 microgram) and phytohaemagglutinin (HA15; 1.0 microgram), were injected intravitreally into one eye of goldfish (body length 5-6 cm), and mitotic RPCs in both retinas were detected and counted 3-50 days later by immunohistochemistry for proliferating cell nuclear antigen (PCNA). Retinal integrity after treatment was assessed by immunohistochemistry for tyrosine hydroxylase (TH) and other retinal antigens. All the agents applied altered the density of PCNA-immunoreactive (ir) cells in the outer and inner nuclear layers (ONL and INL) in both retinas as soon as 2-3 days after unilateral injection. Initially (2-20 days after injection), particularly in the treated retina, PCNA-ir cells appeared in clusters accompanied by various numbers of scattered individual cells, but subsequently the clusters of PCNA-ir cells disappeared while the density of singly distributed cells increased until 30 days after injection. At the doses given, these effects were most striking with aFGF and bFGF and less with IL-6 and HA15. In radial cryosections, other cellular elements immunoreactive to markers such as TH, serotonin, neuropeptide Y, substance P, glutamine synthetase, glial fibrillary acidic protein and protein kinase C, were found normal in terms of morphology. In addition, a monoclonal antibody (NN-2) was found to label some non-neuronal structures (macrophages, microglia and blood vessels) inside and outside the retina intoxicated with 6-hydroxydopamine, a few NN-2-ir cells being PCNA-positive. However, clustered PCNA-ir and marginal neuroblast cells were NN-2-negative. These results indicate that FGFs may play an important role in stimulating the proliferation of RPCs, for example, in the regeneration of fish retinas following neurotoxic destruction.
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PMID:Fibroblast growth factor induces proliferating cell nuclear antigen-immunoreactive cells in goldfish retina. 751 Mar 76

1. Recent data suggesting that the human neuroblastoma SH-SY5Y is a suitable cell line in which to study the effect of second messengers on NA release are discussed in the context of current views on exocytosis. 2. Release of NA is evoked by depolarization, as well as activation of muscarinic (M3) and bradykinin (B2) receptors in SH-SY5Y cells which have not been differentiated by the addition of growth factors. 3. Evoked release is enhanced by activation of protein kinase C. 4. Activation of protein kinase C decreases the changes in intracellular calcium evoked by carbachol, bradykinin and 100 mM K+. 5. SH-SY5Y express N-type and L-type voltage sensitive Ca2+ channels. L-Type Ca(2+)-channels are coupled to NA release under conditions of weak depolarization. However with strong depolarization (100 mM K+) both L-type and N-type channels are involved. 6. Muscarinic- and neuropeptide Y receptors are coupled to the inhibition of Ca2+ channel activity.
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PMID:The use of the human neuroblastoma SH-SY5Y to study the effect of second messengers on noradrenaline release. 759 Jan 7

Increased sympathetic activity has been documented in patients during acute myocardial infarction. Clinical and experimental studies have suggested that this increased sympatho-adrenergic activation may contribute to the development of lethal ventricular arrhythmias in the ischemic heart. In acute myocardial ischemia, adrenergic stimulation of the ischemic myocardium is independent of plasma catecholamines, since local catecholamine concentrations within the ischemic myocardium surpass plasma concentrations by several orders of magnitude. Both afferent and efferent autonomic nerves are activated immediately with myocardial ischemia. Poorly perfused myocardium, however, is protected within the first few minutes of ischemia, via several mechanisms, against high local concentrations of catecholamines. Ischemia-associated metabolic alterations, such as extracellular potassium accumulation, acidosis, and especially the accumulation of adenosine reduce the transmitter release induced by central sympathetic stimulation. Furthermore, the functional neuronal amine reuptake (uptake1) prevents excessive local accumulation of noradrenaline. With progression of myocardial ischemia to more than 10 min local nonexocytotic noradrenaline release prevails. This release is not prevented by the above-mentioned protective mechanisms and accounts for local extracellular catecholamine concentrations in the micromolar range, i.e., 100 to 1000 times higher than the normal plasma concentrations. It shows several features that make it possible to differentiate it from exocytotic release and to assign it to a carrier-mediated transport of noradrenaline from the sympathetic nerve ending into the synaptic cleft. This release is independent of central sympathetic activity, availability of extracellular calcium, activation of both neuronal calcium channels and protein kinase C, and is not accompanied by the release of sympathetic co-transmitters such as neuropeptide Y. It is however suppressed by blockers of uptake1 and by inhibitors of sodium-proton exchange. Depletion of cardiac catecholamine stores by chronic sympathetic denervation effectively suppresses malignant arrhythmias induced by experimental coronary ligature. Accordingly, inhibitors of nonexocytotic noradrenaline release such as uptake1, blocking agents or sodium-proton exchange inhibitors effectively reduce the occurrence of ischemia-associated ventricular fibrillation, emphasizing the relevance of nonexocytotic noradrenaline release in myocardial ischemia. At the postsynaptic side, catecholamines released during myocardial ischemia exert their effects by stimulating alpha- and beta-adrenergic receptors of cardiac myocytes. During acute myocardial ischemia the responsiveness of adrenergic receptors to stimulation by catecholamines is enhanced. Several studies have demonstrated an increase in functionally coupled beta-adrenergic receptor number during myocardial ischemia. Likewise, alpha 1-adrenergic responsivity increases in myocardium subjected to acute ischemia and contributes significantly to the arrhythmogenic effect of catecholamines.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Sympatho-adrenergic activation of the ischemic myocardium and its arrhythmogenic impact. 763 99

Somatostatin (SS) and neuropeptide Y (NPY) are coproduced in a subpopulation of neurons that are selectively resistant to NMDA neurotoxicity. We have previously reported that quinolinic acid (QUIN), an NMDA receptor agonist, augments SS mRNA in cultured fetal rat cortical neurons. This study examines coregulation of SS and NPY by QUIN and NMDA in cultured cortical neurons and compares the effects of these agents with those of forskolin and phorbol 12-myristate 13-acetate (PMA), known to activate SS and NPY gene transcription by protein kinase A- and protein kinase C-dependent mechanisms. In addition, transcriptional regulation of the SS gene was investigated by acute transfection of cortical cultures with an SS promoter-chloramphenicol acetyltransferase (CAT) construct. QUIN and NMDA displayed dose-dependent fourfold augmentation of levels of mRNA for SS but not for NPY. In contrast, forskolin and PMA increased both SS and NPY mRNA levels. QUIN- and NMDA-mediated induction of SS mRNA was blocked by the NMDA receptor antagonist (-)-2-amino-5-phosphonovaleric acid and displayed regional brain specificity because it was not observed in fetal hypothalamic cell cultures. In time course studies, the effects of QUIN/NMDA on SS mRNA occurred after a latency of 8 h, indicating a delayed effect. Cortical cells transfected with pSS-750 CAT showed three- to fourfold stimulation of CAT activity with forskolin but not by QUIN or NMDA. These data reveal a dose-dependent, tissue-specific, NMDA receptor-mediated stimulation of SS but not NPY mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Differential stimulation of somatostatin but not neuropeptide Y gene expression by quinolinic acid in cultured cortical neurons. 764 30

Cultured principal neurons of the superior cervical ganglion (SCG), which coexpress high levels of catecholamines and neuropeptide Y (NPY), were used as a model to simultaneously examine whether sympathetic neuronal peptide and transmitter content or secretion are differentially regulated. Accumulation of NPY immunoreactivity and the dopamine metabolites DOPAC and HVA in SCG neuronal conditioned culture medium was used as an index of NPY and catecholamine secretion, respectively. Release of NPY and catecholamines was linear with time; SCG neurons exhibited a basal NPY secretory rate of approximately 0.9-3 fmol NPY immunoreactivity/10(4) cells/hr, and basal DOPAC plus HVA accumulation was about 10-20 pmol total metabolites/10(4) cells/hr. While sympathetic neuronal NPY and total catecholamine cell content increased more than 6-10-fold by 14 d of culture, secretion remained constant. Depolarization stimulated the rate of NPY secretion 18-fold, whereas medium catecholamine metabolite levels increased 3-fold. Activation of intracellular signaling pathways was shown to be an important point of regulation of sympathetic neuron peptide and transmitter content and secretion. Differential regulation of SCG neuron NPY and catecholamine expression was second messenger system specific. Activation of the protein kinase A pathway with the cAMP analog dibutyryl cAMP, or the adenylyl cyclase activator forskolin, produced a concentration-dependent, sustained stimulation of NPY secretion; maximal stimulation resulted in decreased cellular NPY content. Parallel stimulated neuronal catecholamine release was observed, but in contrast to NPY, total cellular catecholamine content was also increased. Regulation of the protein kinase C pathway with phorbol myristate acetate (PMA) stimulated SCG neuronal NPY secretion to a lesser degree than activation of protein kinase A, but did not alter cellular NPY levels. PMA minimally stimulated catecholamine release and content. NPY secretion induced by the calcium ionophore A23187 was paralleled by a concomitant decrease in cellular NPY. A23187 decreased catecholamine release, but did not change cellular total catecholamine levels. The magnitude of the secretory responses of sympathetic neurons to these regulators was far greater than changes in NPY or catecholamine content, biosynthesis or mRNA levels, suggesting that release is a primary site of regulation. The independent regulation of sympathetic neuronal NPY and catecholamine content and release is consistent with the fundamental differences in the biosynthetic pathways, vesicular compartmentalization, uptake and metabolism of neuropeptides and neurotransmitters.
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PMID:Differential regulation of sympathetic neuron neuropeptide Y and catecholamine content and secretion. 779 Sep 25


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