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)

The role of various intracellular signals and of their possible interactions in the control of neurotransmitter release was investigated in PC12 cells. To this purpose, agents that affect primarily the cytosolic concentration of Ca2+, [Ca2+]i (ionomycin, high K+), agents that affect cyclic AMP concentrations (forskolin; the adenosine analogue phenylisopropyladenosine; clonidine) and activators of protein kinase C (phorbol esters) were applied alone or in combination to either growing chromaffin-like PC12-cells, or to neuron-like PC12+ cells differentiated by treatment with NGF (nerve growth factor). In addition, the release effects of muscarinic-receptor stimulation (which causes increase in [Ca2+]i, activation of protein kinase C and decrease in cyclic AMP) were investigated. Two techniques were employed to measure catecholamine release: static incubation of [3H]dopamine-loaded cells, and perfusion incubation of unlabelled cells coupled to highly sensitive electrochemical detection of released catecholamines. The results obtained demonstrate that: (1) release from PC12 cells can be elicited by both raising [Ca2+]i and activating protein kinases (protein kinase C and, although to a much smaller extent, cyclic AMP-dependent protein kinase); and (2) these various control pathways interact extensively. Activation of muscarinic receptors by carbachol induced appreciable release responses, which appeared to be due to a synergistic interplay between [Ca2+]i and protein kinase C activation. The muscarinic-induced release responses tended to become inactivated rapidly, possibly by feedback desensitization of the receptor mediated by protein kinase C. Muscarinic inactivation was prevented (or reversed) by agents that increase, and accelerated by agents that decrease, cyclic AMP. Agents that stimulate release primarily through the Ca2+ pathway (ionomycin and high K+) were found to be equipotent in both PC12- and PC12+ cells, whereas the protein kinase C activator 12-O-tetradecanoyl-phorbol 13-acetate was approx. 10-fold less potent in PC12+ cells, when administered either alone or in combination with ionomycin. In contrast, the cell binding of phorbol esters was not greatly modified by NGF treatment. Thus control of neurotransmitter release from PC12 cells is changed by differentiation, with a diminished role of the mechanism mediated by protein kinase C.
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PMID:Second-messenger control of catecholamine release from PC12 cells. Role of muscarinic receptors and nerve-growth-factor-induced cell differentiation. 285 Jul 96

NGF treatment of PC12 cells caused a rapid increase in the state of phosphorylation of synapsin I. This phosphorylation of synapsin I is accompanied by a decrease in its electrophoretic mobility on SDS-PAGE. Phosphopeptide fingerprint analysis of the synapsin I revealed that this phosphorylation occurred on a particular phosphopeptide, designated peptide N. Phosphoserine was the only phosphoamino acid detected in peptide N. Partially purified PC12 synapsin I was a substrate for several protein kinases known to be capable of phosphorylating brain synapsin I, but none of these kinases phosphorylated synapsin I on peptide N. The results suggest that the NGF-stimulated phosphorylation of synapsin I may be mediated by a novel protein kinase.
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PMID:Synapsin I in PC12 cells. II. Evidence for regulation by NGF of phosphorylation at a novel site. 303 68

Primary cultures of adult rat dorsal root ganglia (DRG) neurons were used to determine if activation of either the protein kinase A or C signal transduction pathways or treatment with the synthetic glucocorticoid dexamethasone modulate neuronal calcitonin gene-related peptide (CGRP) synthesis and release. DRG are the sites of neuronal cell bodies known to produce abundant CGRP levels, and to send axons peripherally to blood vessels and centrally to the spinal cord. Using immunocytochemical techniques, we confirmed that synthesis of immunoreactive CGRP (iCGRP) is restricted to a subpopulation of DRG neurons. Subsequently, we determined that treatment (24 h) of the neurons with either dibutyryl cAMP (1 mM) or phorbol 12-myristate 13-acetate (2 microM) increased CGRP mRNA content 2.2 +/- 0.4 (n = 6, p < 0.03) and 3.0 +/- 0.6-fold (n = 6, P < 0.02) respectively, while secreted iCGRP levels were increased 1.8 +/- 0.2 (n = 14, P < 0.005) and 4.5 +/- 1.0 (n = 14, P < 0.001)-fold over control levels. Treatment of the neurons with dexamethasone alone had no effect on CGRP expression; however, this agent was able to significantly attenuate the stimulatory effects of NGF on both CGRP mRNA accumulation and release of iCGRP. Time course studies demonstrated that in the phorbol ester treated neurons CGRP mRNA levels continued to increase at 48 h, while maximal induction with dibutyryl cAMP occurred at approximately 12 h. These results indicate that local and/or circulating factors which act through the protein kinase A and C signal transduction pathways upregulate both CGRP expression and release, while glucocorticoids attenuate the stimulatory effects of NGF.
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PMID:Dexamethasone and activators of the protein kinase A and C signal transduction pathways regulate neuronal calcitonin gene-related peptide expression and release. 758 74

The neurotransmitter, pituitary adenylate cyclase-activating polypeptide (PACAP), is present in the rat adrenal medulla and is a potent stimulus for catecholamine secretion. Previous studies have suggested that neurally derived signals stimulate proliferation of chromaffin cells in adult rats. To determine whether PACAP might be involved in mitogenic signalling, its effects on bromodeoxyuridine incorporation were studied in adrenal medullary cell cultures from adult female rats. Both PACAP 27 and PACAP 38 are able to stimulate proliferation of adult rat chromaffin cells in vitro, either alone or in conjunction with PMA, an activator of protein kinase C. BrdU-labelled nuclei are observed in both epinephrine and norepinephrine cells, and proliferation of both cell types is stimulated by the same concentrations of PACAP that elicit secretion of catecholamines. The mitogenic effects of PACAP are potentiated by indolidan, a phosphodiesterase inhibitor known to cause pheochromocytomas in rats, and are inhibited by H-89, an inhibitor of protein kinase A. Mitogenic concentrations of PACAP inhibit mitogenic effects of nerve growth factor. These findings support the hypothesis that neurally derived signals regulate chromaffin cell proliferation in adult rats. Indolidan and a variety of nongenotoxic agents that cause pheochromocytomas in rats may do so indirectly by increasing neurally mediated chromaffin cell turnover. The antagonism between PACAP and NGF suggests that neurotransmitters may supersede growth factors in regulating chromaffin cell proliferation during development by suppressing or co-opting portions of growth factor signaling pathways.
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PMID:Mitogenic and antimitogenic effects of pituitary adenylate cyclase-activating polypeptide (PACAP) in adult rat chromaffin cell cultures. 762 29

In PC12 cells, cAMP stimulates the MAP kinase pathway by an unknown mechanism. Firstly, we examined the role of calcium ion mobilization and of protein kinase C in cAMP-stimulated MAP kinase activation. We show that cAMP stimulates p44mapk independently of these events. Secondly, we studied the role of B-Raf in this process. We observed that NGF, PMA and cAMP induce the phosphorylation of B-Raf as well as an upward shift in its electrophoretic mobility. We show that B-Raf is activated following NGF and PMA treatment of PC12 cells, and that it can phosphorylate and activate MEK-1. However, cAMP inhibits B-Raf autokinase activity as well as its ability to phosphorylate and activate MEK-1. This inhibition is likely to be due to a direct effect since we found that PKA phosphorylates B-Raf in vitro. Further, we show that B-Raf binds to p21ras, but more important, this binding to p21ras is virtually abolished with B-Raf from PC12 cells treated with CPT-cAMP. Hence, these data indicate that the PKA-mediated phosphorylation of B-Raf hampers its interaction with p21ras, which is responsible for the PKA-mediated decrease in B-Raf activity. Finally, our work suggests that in PC12 cells, cAMP stimulates MAP kinase through the activation of an unidentified MEK kinase and/or the inhibition of a MEK phosphatase.
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PMID:Regulation of the MAP kinase cascade in PC12 cells: B-Raf activates MEK-1 (MAP kinase or ERK kinase) and is inhibited by cAMP. 783 30

The vgf gene encodes one of the most rapidly induced neuronal mRNAs identified in NGF-treated PC12 cells. Maximal inhibition of VGF mRNA induction was achieved using K-252a, an inhibitor of the NGF-receptor Trk tyrosine kinase, and by mutating both Y490 (SHC association site) and Y785 (PLC-gamma 1 association site) of Trk. Inhibitors of the NGF-activated protein kinase N (PKN) were found to partially and in some cases transiently block VGF induction by NGF while in PKA-deficient PC12 cells, VGF induction by NGF was comparable to that observed in parental PC12 cells. The binding of NGF to Trk therefore activates redundant signal transduction pathways which converge to regulate vgf gene expression.
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PMID:Stimulation of vgf gene expression by NGF is mediated through multiple signal transduction pathways involving protein phosphorylation. 787 12

A pheochromocytoma from a 59-year-old woman was found to be immunoreactive to adrenocorticotropin (ACTH), chromogranin, neurofilament-200, neuron-specific enolase and S-100 protein. Northern blot analysis showed that both proopiomelanocortin (POMC) and corticotropin-releasing hormone (CRH) genes were expressed in the pheochromocytoma but not in the surrounding adrenal cortex. In primary culture, the POMC and CRH mRNAs were increased by dexamethasone (500 micrograms/l for 3 days) up to 10- and 15-fold of the control, respectively. The secretion of ACTH also was stimulated eightfold with the same treatment. The stimulatory effect of dexamethasone on POMC gene expression was inhibited 70% by nerve growth factor (NGF, 200 micrograms/l), 30% by 12-O-tetradecanoyl phorbol 13-acetate (TPA, 160 nmol/l) (a protein kinase-C activator) and 30% by (Bu)2cAMP (1 mmol/l). On the other hand, NGF alone increased the CRH mRNA accumulation up to 10-fold, and further enhanced the stimulatory effect of dexamethasone on the CRH mRNA twofold, and TPA inhibited (30%) the dexamethasone-induced CRH mRNA accumulation. Furthermore, the conditioned medium of the pheochromocytoma cells increased secretion of corticosterone fourfold in the primary culture of rat fetal adrenal cells. Our results indicate abnormal expression and regulation of POMC and CRH genes in this pheochromocytoma.
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PMID:Pheochromocytoma expressing adrenocorticotropin and corticotropin-releasing hormone; regulation by glucocorticoids and nerve growth factor. 792 Dec 4

Although neuronal nicotinic ACh receptors (nAChR) play a key role in synaptic transmission and information transfer in the nervous system, little is known about the molecular mechanisms that govern the expression of the multiple subunits that form the receptors and determine their functional properties. Using electrophysiological and molecular biological approaches, we have investigated the NGF-mediated regulation of nAChR expression in rat pheochromocytoma (PC12) cells and protein kinase A (PKA)-deficient PC12 cells. We report that NGF treatment increases steady state levels of mRNA encoding the alpha 3, alpha 5, alpha 7, beta 2, and beta 4 subunits, increases the occurrence of ACh-induced single-channel activity in excised patches, and increases ACh-induced macroscopic current density, all by mechanisms independent of PKA activity.
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PMID:Nerve growth factor increases nicotinic ACh receptor gene expression and current density in wild-type and protein kinase A-deficient PC12 cells. 812 Jun 17

We have examined the effects of the protein kinase inhibitor KT5926 on NGF-promoted responses in PC12 and PC12-C41 cells (a subclone of the parental cell line). Our findings reveal that this compound specifically and reversibly prevents the NGF-induced outgrowth and regeneration of neurites. In addition, neurites of NGF-pretreated cells cease further elongation upon exposure to KT5926. However, preexisting neurite networks in the cultures remain intact in the presence of the drug. The inhibition of neuritic growth appears to occur at least in part at the level of growth cones since KT5926 also causes these structures to collapse and inhibits NGF-promoted reactivation of NGF-deprived growth cones. Although KT5926 is an analogue of K-252a, which blocks all responses to NGF, it does not affect other NGF-elicited cellular responses examined, including NGF-dependent priming of cells, gp140prototrk autophosphorylation, immediate-early gene induction, and phosphorylation of several known cytoskeletal proteins (MAP 1.2/1B, chartin MAPs, and beta-tubulin). However, phosphate incorporation into a cytoskeletally localized 58 kDa phosphoprotein, designated pp58, is selectively reduced in KT5926-treated cultures (+/- NGF). Although KT5926 is an in vitro inhibitor of myosin light chain kinase and calmodulin-dependent protein kinase II, inhibition of these two kinase activities by ML-9 and KN-62, respectively, applied alone or together, does not mimic the effects of KT5926 on neurite growth and on pp58 phosphorylation. Taken together, our findings suggest that KT5926, via a previously unidentified protein kinase inhibitory activity, differentially interferes with NGF-promoted growth cone function and consequently affects neuritic outgrowth. This compound should therefore be a useful tool for dissecting the mechanism of NGF actions and affords a means to identify phosphoproteins that play specific roles in neurite growth/elongation.
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PMID:KT5926 selectively inhibits nerve growth factor-dependent neurite elongation. 818 31

Using PC12 cells to study ethanol's effects on growth of neural processes, we found that ethanol enhances NGF- and basic FGF-induced neurite outgrowth. Chronic ethanol exposure selectively up-regulates delta and epsilon protein kinase C (PKC) and increases PKC-mediated phosphorylation in PC12 cells. Since PKC regulates differentiation, we investigated the role of PKC in enhancement of neurite outgrowth by ethanol. Like ethanol, 0.3-10 nM phorbol 12-myristate, 13-acetate (PMA) increased NGF-induced neurite outgrowth. However, higher concentrations did not, and immunoblot analysis demonstrated that 100 nM PMA markedly depleted cells of beta, delta and epsilon PKC. PMA (100 nM) also down-regulated beta, delta and epsilon PKC in ethanol-treated cells and completely prevented enhancement of neurite outgrowth by ethanol. In contrast, the cAMP analogue 8-bromoadenosine cAMP did not completely mimic the effects of ethanol on neurite outgrowth, and ethanol was able to enhance neurite formation in mutant PC12 cells deficient in protein kinase A (PKA). These findings implicate beta, delta or epsilon PKC, but not PKA, in the neurite-promoting effects of ethanol and PMA. Since chronic ethanol exposure up-regulates delta and epsilon, but not beta PKC, these findings suggest that delta or epsilon PKC regulate neurite outgrowth.
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PMID:Protein kinase C isozymes that mediate enhancement of neurite outgrowth by ethanol and phorbol esters in PC12 cells. 825 18


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