共查询到20条相似文献,搜索用时 78 毫秒
1.
Evidence for Cyclic AMP-Mediated Increase of Aromatic L-Amino Acid Decarboxylase Activity in the Striatum and Midbrain 总被引:2,自引:0,他引:2
Abstract: Aromatic L-amino acid decarboxylase (AAAD) activity of mouse striatum and midbrain increased after an intracerebro-ventricular injection of either forskolin or 8-bromo-cyclic AMP. The increase was transient, peaking between 15 and 30 min and returning to baseline by ˜90 min. The increase of AAAD activity after forskolin was not affected by pretreatment with cycloheximide. Kinetic studies indicated an apparent increase of V max with little change of the K m for L-DOPA or pyridoxal 5'-phosphate. We conclude that AAAD activity of striatum and midbrain can be modulated by a cyclic AMP-dependent process. 相似文献
2.
Aromatic L-amino acid decarboxylase (AAAD), an enzyme required for the synthesis of catecholamines, indoleamines, and trace amines, is rapidly activated by cyclic AMP-dependent pathways in striatum and midbrain in vivo, suggesting enzyme phosphorylation. We now report that the catalytic subunit of cyclic AMP-dependent protein kinase (PKA) directly phosphorylated AAAD immunoprecipitated from homogenates prepared from the mouse striatum and midbrain in vitro. Under the same phosphorylation conditions, the catalytic subunit of PKA also phosphorylated a recombinant AAAD protein expressed in Escherichia coli transfected with an AAAD cDNA isolated from the bovine adrenal gland. The PKA-induced AAAD phosphorylation of immunoprecipitates from striatum and midbrain was time and concentration dependent and blocked by a specific PKA peptide inhibitor. Incubation of the catalytic subunit of PKA with striatal homogenates increased enzyme activity by approximately 20% in a time- and concentration-dependent manner. Moreover, incubation of the catalytic subunit of PKA with recombinant AAAD increased activity by approximately 70%. A direct phosphorylation of AAAD protein by PKA might underlie the cyclic AMP-induced rapid and transient activation of AAAD in vivo. 相似文献
3.
Ruth A. Lanius ‡Christopher A. Shaw †Ravenska Wagey † Charles Krieger 《Journal of neurochemistry》1994,63(1):155-160
Abstract: We have characterized a high-affinity [35 S]-glutathione ([35 S]GSH) binding site in mouse and human spinal cord. [35 S]GSH binding sites in mouse and human spinal cord were observed largely within the gray matter in both the dorsal and ventral horns of spinal cord at cervical, thoracic, and lumbosacral segments. High-affinity [35 S]GSH binding was saturable, showing a B max of 72 fmol/mg of protein and a K D of 3.0 n M for mouse spinal cord and a B max of 52 fmol/mg of protein and a K D of 1.6 n M for human spinal cord. [35 S]GSH binding was displaceable by GSH, l -cysteine, and S -hexyl-GSH, but not by glutamate, glycine, or NMDA. These [35 S]GSH binding sites exhibited kinetic and saturation characteristics similar to GSH binding sites in rat brain astrocytes. To determine whether [35 S]GSH binding sites could be regulated by protein kinase C, we exposed human spinal cord sections to phorbol 12,13-diacetate for 1 h before ligand binding. Phorbol ester treatment increased [35 S]GSH binding by ∼60%, an effect that could be blocked by exposure of spinal cord sections to 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine, a general protein kinase inhibitor. [35 S]GSH binding sites in the spinal cord of both species exhibited many of the characteristics of a receptor including saturable binding, high affinity, ligand specificity, and modulation by kinase activity. These data suggest that GSH is a neurotransmitter in the CNS. 相似文献
4.
Malgorzata Chalimoniuk Anna Stolecka† Elzbieta Ziemiska‡ Adam Stpie§ Josef Langfort†¶ Joanna B. Strosznajder 《Journal of neurochemistry》2009,110(1):307-317
The study was aimed at investigating in vivo and in vitro the involvement of the cGMP/cGMP-dependent protein kinase (PKG) signaling pathway in MPP+ -induced cytosolic phospholipase A2 (cPLA2 ) activation of dopaminergic neurons. MPP+ activated neuronal nitric oxide synthase (NOS)/soluble guanylyl cyclase/cGMP pathway in mouse midbrain and striatum, and in pheochromocytoma cell line 12 cells, and caused an upward shift in [Ca2+ ]i level in the latter. The activation was accompanied by increases in total and phosphorylated cPLA2 , and increased arachidonic acid release. Effects of selective inhibitors [2-oxo-1,1,1-trifluoro-6,9-12,15-heneicosatetraene (AACOCF3 ), (E)-6-(bromomethylene)tetrahydro-3-(1-naphthalenyl)2h-pyran-2-one (BEL)] indicated the main impact of cPLA2 on arachidonic acid release in pheochromocytoma cell line 12 cells. Treatment of the cells with the protein kinase inhibitors GF102610x, UO126, and KT5823, and with the nitric oxide synthase (NOS) inhibitor NNLA revealed the involvement of protein kinase C (PKC) and extracellular signal-regulated kinases 1 and 2 (ERK 1/2), with the possible key role of PKG, in cPLA2 phosphorylation at Ser505. Inhibitors of cPLA2 and PKG increased viability and reduced MPP+ -induced apoptosis of the cells. Our results indicate that the neuronal NOS/cGMP/PKG pathway stimulates cPLA2 phosphorylation at Ser505 by activating PKC and ERK1/2, and suggest that up-regulation of this pathway in experimental models of Parkinson's disease may mediate dopaminergic neuron degeneration and death through activation of cPLA2 . 相似文献
5.
Abstract: GT1-7 cells, a clonal line derived from specific tumours of gonadotropin-releasing hormone-secreting neurons from mouse hypothalamus, were used as a model system to investigate the cellular mechanisms underlying the histamine H1 receptor-mediated desensitisation. GT1-7 cells contain H1 receptors, acute stimulation of which leads to the desensitisation of histamine-mediated calcium mobilisation and is manifest as a concurrent reduction in both the magnitude of the calcium transient and of the sustained phase. Acute pretreatment of the cells with the phorbol ester, phorbol 12-myristate 13-acetate, can also ablate the histamine-stimulated calcium mobilisation. In addition, acute H1 -receptor stimulation and acute phorbol ester treatment result in the attenuation of histamine-mediated inositol phosphate production. Receptor desensitisation resulting from acute stimulation with histamine is not affected by inhibiting protein kinase C (PKC) activity with Ro 31-7549 or staurosporine. In contrast, the desensitisation of H1 -receptor responses induced by direct activation of protein kinase C is preventable by PKC inhibitors. Thus, these results imply that a PKC-dependent mechanism and PKC-independent mechanism are involved in the H1 -receptor desensitisation cascade in GT1-7 cells and do not support the involvement of PKC in the receptor-mediated desensitisation of H1 receptor-stimulated calcium and inositol phosphate responses. 相似文献
6.
Kazuhiko Fukuda Shigehisa Kato Hitoshi Morikawa Takehiro Shoda Kenjiro Mori 《Journal of neurochemistry》1996,67(3):1309-1316
Abstract: To examine whether the mitogen-activated protein kinase (MAPK) cascade and phospholipase A2 (PLA2 ) are involved in the signal transduction mechanism of the opioid receptor, the δ-, μ-, and κ-opioid receptors were stably expressed from cDNA in Chinese hamster ovary cells. Activation of the δ-, μ-, and κ-receptors by agonists induced a rapid and transient increase in MAPK activity accompanied by reduced electrophoretic mobility of the 42-kDa isoform of MAPK (p42), probably owing to phosphorylation. The opioid receptor-mediated increase in MAPK activity was suppressed not only by pretreatment with genistein, a tyrosine protein kinase inhibitor, but also by prolonged exposure to phorbol 12-myristate 13-acetate and pretreatment with GF 109203X, a selective protein kinase C (PKC) inhibitor, suggesting the involvement of PKC as well as tyrosine protein kinase. Furthermore, stimulation of the δ-, μ-, and κ-receptors with opioid agonists in the presence of A23187, a calcium ionophore, resulted in an increase in arachidonate release, suggesting that PLA2 is activated by the opioid receptors when the intracellular Ca2+ concentration is elevated. Both MAPK activation and increase in arachidonate release mediated by the opioid receptors were abolished by pretreatment with pertussis toxin, suggesting that these responses are mediated by Gi or Go types of GTP-binding regulatory proteins. 相似文献
7.
Catherine Pasqualini Bernard Guibert Odile Frain Vincent Leviel 《Journal of neurochemistry》1994,62(3):967-977
Abstract: The mechanism of the short-term activation by prolactin (PRL) of tyrosine hydroxylase (TH) in tuberoinfundibular dopaminergic neurons was examined in vitro on hypothalamic slices from ovariectomized rats. TH activity (determined by 3,4-dihydroxyphenylalanine accumulation in the median eminence after blockade of decarboxylase with NSD 1055) showed a dose-dependent increase within 2 h of incubation of the hypothalamic slices with PRL. To determine whether a phosphorylation process was involved in this increase in TH activity, we studied the sensitivity of the enzyme to dopamine (DA) feedback inhibition. In control median eminences, two kinetically different forms of TH coexisted, one exhibiting a K 1(DA) value of 29.92 ± 0.49 μ M , the other being × 15-fold more sensitive to DA inhibition with a K 1(DA) of 1.96 ± 0.09 μ M , likely corresponding to a phosphorylated and active form and to a nonphosphorylated and less active form, respectively. After PRL treatment, the TH form of low K 1(DA) remained unaffected, whereas the K 1(DA) of the purported active form of TH increased to 62.6 ± 0.8 μ M , suggesting an increase in the enzyme phosphorylation. This increase in the K I(DA) of TH was selectively prevented by GF 109203X, a potent and selective inhibitor of protein kinase C, but not by a specific inhibitor of protein kinase A or calmodulin. Finally, this action of PRL could be mimicked by 12- O -tetradecan-oylphorbol 13-acetate (a direct activator of protein kinase C). These results suggest that PRL, at the median eminence level, activates TH by increasing the enzyme phosphorylation and that this action may involve an activation of protein kinase C. 相似文献
8.
Activation of Protein Kinase C by the Capsaicin Analogue Resiniferatoxin in Sensory Neurones 总被引:3,自引:0,他引:3
Abstract: Resiniferatoxin and capsaicin are sensory neurone-specific excitotoxins that operate a common cation channel in nociceptors. Resiniferatoxin is structurally similar to capsaicin and to phorbol esters. Specific [3 H]-resiniferatoxin binding, which was detected in the membrane ( K D value 1.8 ± 0.2 n M ) but not cytosolic fraction of rat dorsal root ganglia, could not be displaced by phorbol 12,13-dibutyrate. Conversely, resiniferatoxin did not displace [3 H]phorbol 12,13-dibutyrate binding in either the cytosolic or membrane fraction. Resiniferatoxin and capsaicin both caused translocation of protein kinase C in dorsal root ganglion neurones (EC50 value 18 ± 3 n M ). This translocation was greatly reduced but not abolished, in the absence of external Ca2+ , suggesting that it was secondary to Ca2+ entry. Resiniferatoxin also caused direct activation of a Ca2+ - and lipid-dependent kinase (or kinases) in the cytosolic fraction of dorsal root ganglia, at concentrations (100 n M to 10 µ M ) higher than required for displacement of [3 H]resiniferatoxin binding or translocation of protein kinase C. Capsaicin (up to 10 µ M ) was unable to mimic this effect. These data imply that although resiniferatoxin-induced translocation of protein kinase C in dorsal root ganglion neurones was mainly indirect, it also caused direct activation of a protein kinase C-like kinase in these cells. 相似文献
9.
Depolarization and Neurotransmitters Increase Neuronal Protein Tyrosine Phosphorylation 总被引:5,自引:2,他引:3
Julio C. Siciliano Michèle Gelman Jean-Antoine Girault 《Journal of neurochemistry》1994,62(3):950-959
Abstract: 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. Qlutamate, 1-aminocyclopentane- trans -1,3-dicarboxylic acid (an agonist of metabotropic glutamate receptors), and α-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 Ca2+ -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 α1 ,-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. 相似文献
10.
Endothelin Stimulates Phospholipase D in Striatal Astrocytes 总被引:1,自引:1,他引:0
Solange Desagher Jocelyne Cordier Jacques Glowinski Martine Tencé 《Journal of neurochemistry》1997,68(1):78-87
Abstract: In primary cultures of mouse striatal astrocytes prelabeled with [3 H]myristic acid, endothelin (ET)-1 induced a time-dependent formation of [3 H]phosphatidic acid and [3 H]diacylglycerol. In the presence of ethanol, a production of [3 H]phosphatidylethanol was observed, indicating the activation of a phospholipase D (PLD). ET-1 and ET-3 were equipotent in stimulating PLD activity (EC50 = 2–5 n M ). Pretreatment of the cells with pertussis toxin partially abolished the effect of ET-1, indicating the involvement of a Gi /Go protein. Inhibition of protein kinase C by Ro 31-8220 or down-regulation of the kinase by a long-time treatment with phorbol 12-myristate 13-acetate (PMA) totally abolished the ET-1-induced stimulation of PLD. In contrast, a cyclic AMP-dependent process is not involved in the activation of PLD, because the ET-1-evoked formation of [3 H]phosphatidylethanol was not affected when cells were coincubated with either isoproterenol, 8-bromo-cyclic AMP, or forskolin. Acute treatment with PMA also stimulated PLD through a protein kinase C-dependent process. However, the ET-1 and PMA responses were additive. Furthermore, the ET-1-evoked response, contrary to that of PMA, totally depended on the presence of extracellular calcium. These results suggest that at least two distinct mechanisms are involved in the control of PLD activity in striatal astrocytes. Finally, ET-1, ET-3, and PMA also stimulated PLD in astrocytes from the mesencephalon, the cerebral cortex, and the hippocampus. 相似文献
11.
Abstract: Termination of synaptic glutamate transmission depends on rapid removal of glutamate by neuronal and glial high-affinity transporters. Molecular biological and pharmacological studies have demonstrated that at least five subtypes of Na+ -dependent mammalian glutamate transporters exist. Our study demonstrates that Y-79 human retinoblastoma cells express a single Na+ -dependent glutamate uptake system with a K m of 1.7 ± 0.42 µ M that is inhibited by dihydrokainate and dl - threo -β-hydroxyaspartate (IC50 = 0.29 ± 0.17 µ M and 2.0 ± 0.43 µ M , respectively). The protein kinase C activator phorbol 12-myristate 13-acetate caused a concentration-dependent inhibition of glutamate uptake (IC50 = 0.56 ± 0.05 n M ), but did not affect Na+ -dependent glycine uptake significantly. This inhibition of glutamate uptake resulted from a fivefold decrease in the transporter's affinity for glutamate, without significantly altering the V max . 4α-Phorbol 12,13-didecanoate, a phorbol ester that does not activate protein kinase C, did not alter glutamate uptake significantly. The phorbol 12-myristate 13-acetate-induced inhibition of glutamate uptake was reversed by preincubation with staurosporine. The biophysical and pharmacological profile of the human glutamate transporter expressed by the Y-79 cell line indicates that it belongs to the dihydrokainate-sensitive EAAT2/GLT-1 subtype. This conclusion was confirmed by western blot analysis. Protein kinase C modulation of glutamate transporter activity may represent a mechanism to modulate extracellular glutamate and shape postsynaptic responses. 相似文献
12.
Carlos-Alberto Gonçalves Amanda Hall Alistair T. R. Sim Stephen J. Bunn Philip D. Marley Tat B. Cheah Peter R. Dunkley 《Journal of neurochemistry》1997,69(6):2387-2396
Abstract: The protein kinases and protein phosphatases that act on tyrosine hydroxylase in vivo have not been established. Bovine adrenal chromaffin cells were permeabilized with digitonin and incubated with [γ-32 P]ATP, in the presence or absence of 10 µ M Ca2+ , 1 µ M cyclic AMP, 1 µ M phorbol dibutyrate, or various kinase or phosphatase inhibitors. Ca2+ increased the phosphorylation of Ser19 and Ser40 . Cyclic AMP, and phorbol dibutyrate in the presence of Ca2+ , increased the phosphorylation of only Ser40 . Ser31 and Ser8 were not phosphorylated. The Ca2+ -stimulated phosphorylation of Ser19 was incompletely reduced by inhibitors of calcium/calmodulin-stimulated protein kinase II (46% with KN93 and 68% with CaM-PKII 273–302), suggesting that another protein kinase(s) was contributing to the phosphorylation of this site. The Ca2+ -stimulated phosphorylation of Ser40 was reduced by specific inhibitors of protein kinase A (56% with H89 and 38% with PKAi 5–22 amide) and protein kinase C (70% with Ro 31-8220 and 54% with PKCi 19–31), suggesting that protein kinases A and C contributed to most of the phosphorylation of this site. Results with okadaic acid and microcystin suggested that Ser19 and Ser40 were dephosphorylated by PP2A. 相似文献
13.
Staurosporine Activates a 60,000 Mr Protein Kinase in Bovine Chromaffin Cells That Phosphorylates Myelin Basic Protein In Vitro 总被引:2,自引:2,他引:0
Biljana Pavlovi-urjanev Anne L. Cahill Robert L. Perlman 《Journal of neurochemistry》1993,61(2):697-703
Abstract: Bovine chromaffin cells contain a family of renaturable protein kinases. One of these, a 60,000 Mr kinase (PK60) that phosphorylated myelin basic protein in vitro, was activated fourfold when cells were treated with the protein kinase inhibitor Staurosporine. Because staurosporine inhibits protein kinase C, the role of this kinase in the regulation of PK60 activity was investigated. Fifty nanomolar Staurosporine produced half-maximal inhibition of protein kinase C activity in chromaffin cells, whereas ∼225 n M Staurosporine was required to induce half-maximal activation of PK60. Other protein kinase C inhibitors, H-7 and K-252a, did not mimic the effect of Staurosporine on PK60 activity. Chromaffin cells have three protein kinase C isoforms: α, ε, and ζ. Prolonged treatment with phorbol esters depleted the cells of protein kinase C α and ε, but not ζ. Neither activation nor depletion of protein kinase C affected the basal activity of PK60. Moreover, Staurosporine activated PK60 in cells depleted of protein kinase C α and e; thus, Staurosporine appeared to activate PK60 by a mechanism that does not require these protein kinase C isoforms. Incubation of cell extracts with Staurosporine in vitro did not activate PK60. Incubation of these extracts with adenosine 5'-O-(3-thiotriphosphate), however, caused a twofold activation of PK60. Although this suggests that PK60 activity is regulated by phosphorylation, the mechanism by which Staurosporine activates PK60 is not known. Staurosporine has been reported to promote neurite outgrowth from chromaffin cells. The role of PK60 in mediating the effects of Staurosporine on chromaffin cell function remains to be determined. 相似文献
14.
HL-60 cells are very sensitive to the cytotoxic action of ether lipids. Several hypotheses have been proposed to explain this cytotoxicity. We investigated the influence of the alkylphospholipid ET-18-OCH3 on the activity of protein kinase C. HL-60 cells were incubated with ET-18-OCH3 at a concentration of 20 μg/ml for 4 h. After the incubation the membrane fraction of the HL-60 cells was isolated and the activity of protein kinase C was determined while it was still associated with the membrane, using the synthetic peptide substrate [Ser25]-protein kinase C (19–31) as a protein kinase C specific substrate. The activity of the membrane-bound protein kinase C was increased in HL-60 cells treated with ET-18-OCH3 compared to untreated HL-60 cells. The increase in protein kinase C activity was not a consequence of translocation and appeared to be additive to the effect of the phorbol ester 12-myristate 13-acetate. In contrast, solubilized protein kinase C from HL-60 cells could be inhibited or stimulated in vitro by ET-18-OCH3, dependent on the mode of addition of ET-18-OCH3 and phospholipids. 相似文献
15.
Abstract : In this study we have used the presynaptic-rich rat cerebrocortical synaptosomal preparation to investigate the proteolytic cleavage of the amyloid precursor protein (AβPP) by the α-secretase pathway within the βA4 domain to generate a soluble secreted N-terminal fragment (AβPPs ). AβPP was detected in crude cortical synaptosomal membranes, although at a lower density than that observed in whole-tissue homogenates. Protein kinase C (PKC) activation induced a translocation of the conventional PKC isoform β1 and novel PKCε from cytosol to membrane fractions, but there was no alteration in the proportion of AβPP associated with the Tritonsoluble and -insoluble fractions. AβPPs was constitutively secreted from cortical synaptosomes, with this secretion being enhanced significantly by the direct activation of PKC with phorbol ester. The PKC-induced secretion of AβPPs was only partially blocked by the PKC inhibitor GF109203X (2.5 μ M ), whereas the phosphorylation of the myristoylated alanine-rich C kinase substrate (MARCKS) protein was significantly inhibited by GF109203X. The differential sensitivities of the MARCKS phosphorylation and AβPPs secretion to GF109203X may imply that different PKC isoforms are involved in these two events in the synaptosomal system. These findings strongly suggest that the α-secretase activity leading to the secretion of AβPPs can occur at the level of the presynaptic terminal. 相似文献
16.
Calcium Influx Through AMPA Receptors and Through Calcium Channels Is Regulated by Protein Kinase C in Cultured Retina Amacrine-Like Cells 总被引:3,自引:1,他引:2
Ana Luísa Carvalho Carlos B. Duarte Carlos J. Faro Arsélio P. Carvalho Euclides V. Pires 《Journal of neurochemistry》1998,70(5):2112-2119
Abstract: The functional modulation of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors by protein kinase C (PKC) was investigated in cultures enriched in retinal amacrine-like cells. The kainate-evoked [Ca2+ ]i increase is due to Ca2+ entry through open AMPA receptor channels, because it was blocked by the active isomer of a 2,3-benzodiazepine (LY 303070), an AMPA receptor antagonist. The AMPA receptor response to kainate was potentiated by phorbol 12-myristate 13-acetate, which specifically stimulates PKC, and it was decreased by bisindolylmaleimide I, a selective inhibitor of PKC, as well as by PKC down-regulation. The results indicate not only that the AMPA receptor activation has a PKC requirement, but also that PKC amplifies maximal receptor activation by 100 µ M kainate. The effect of PKC activation or inhibition on voltage-gated Ca2+ -channel activity was also investigated. Activation of PKC caused inhibition of Ca2+ channels, and the same effect was produced by inhibition of PKC, whereas the inactive analogue of the phorbol ester did not affect channel activity. Our results show an important role for PKC in regulating the function of both AMPA receptors and Ca2+ channels in cultured retina cells. 相似文献
17.
Transduction Mechanisms Involved in Thrombin Receptor-Induced Nerve Growth Factor Secretion and Cell Division in Primary Cultures of Astrocytes 总被引:1,自引:0,他引:1
Thomas Debeir Josseline Gueugnon Xavier Vigé Jesús Benavides 《Journal of neurochemistry》1996,66(6):2320-2328
Abstract: In astrocytes, thrombin and thrombin receptor-activating activating peptide (TRAP-14), a 14-amino-acid agonist of the proteolytic activating receptor for thrombin (PART), significantly increased cell division as assessed by [3 H]thymidine incorporation into DNA (EC50 = 1 n M and +650% at 100 n M for thrombin; EC50 = 3 µ M and +600% at 100 µ M for TRAP-14) and nerve growth factor (NGF) secretion (approximately twofold at 100 n M thrombin or 100 µ M TRAP-14). The [3 H]thymidine incorporation was prevented by protein kinase C inhibitors (staurosporine and H7) or by down-regulation of this enzyme by chronic exposure of astrocytes to phorbol 12-myristate 13-acetate (PMA). Thrombin-induced NGF secretion was completely inhibited by protein kinase C inhibitors. Treatment with PMA stimulated NGF secretion 19-fold, and this effect was not further enhanced by thrombin. These data suggest an absolute requirement of protein kinase C activity for thrombin-induced NGF secretion and cell division. Pretreatment of astrocytes with pertussis toxin (PTX) reduced thrombin- and TRAP-14-induced DNA synthesis. PART activation caused a decrease in forskolin-stimulated cyclic AMP accumulation. PTX treatment prevented the inhibitory effect of PART activation on cyclic AMP accumulation, suggesting that a PTX-sensitive G protein, such as Gi or Go , is involved in thrombin-induced cell division. In contrast, thrombin-induced NGF secretion was not inhibited by PTX. Finally, the protein tyrosine kinase inhibitor herbimycin A partially but significantly prevented thrombin- and TRAP-14-induced cell division but was without effect on NGF secretion. Taken together, these results demonstrate that, in astrocytes, PART(s)-triggered cell division or NGF secretion is mediated by distinct transduction mechanisms. 相似文献
18.
Immaculada Herrero María Teresa Miras-Portugal José Sánchez-Prieto 《Journal of neurochemistry》1992,59(4):1574-1577
Abstract: The effects of arachidonic acid and phorbol esters in the Ca2+ -dependent release of glutamate evoked by 4-aminopyridine (4-AP) in rat cerebrocortical synaptosomes were studied. In the absence of arachidonic acid, high concentrations (500 n M ) of 4β-phorbol dibutyrate (4β-PDBu) were required to enhance the release of glutamate. However, in the presence of arachidonic acid, low concentrations of 4β-PDBu (1–50 n M ) were effective in potentiating glutamate exocytosis. This potentiation of glutamate release by phorbol esters was not observed with the methyl ester of arachidonic acid, which does not activate protein kinase C. Moreover, pretreatment of synaptosomes with the protein kinase inhibitor staurosporine also prevented the stimulatory effect by arachidonic acid and phorbol esters. These results suggest that the activation of protein kinase C by both arachidonic acid and phorbol esters may play a role in the potentiation of glutamate exocytosis. 相似文献
19.
Abstract: Neurotransmitter receptors that increase phosphatidylinositol hydrolysis generate second messengers that activate protein kinase C. Here, we used metabotropic glutamate receptor agonists to increase both phosphatidylinositol hydrolysis and secretion of the soluble extracellular fragment of amyloid precursor protein (APPs) from cortical astrocyte cultures. The increase in APPs secretion was mimicked by direct activation of protein kinase C with phorbol ester and was suppressed by the metabotropic glutamate receptor antagonist l -(+)-2-amino-3-phosphonopropionic acid or by the protein kinase C inhibitor GF109203X. Ionotropic glutamate agonists did not increase APPs secretion. Forskolin or dibutyryl cyclic AMP inhibited the increase in APPs secretion caused by metabotropic glutamate receptor agonists or by phorbol ester treatment but did not affect basal APPs levels. Therefore, glutamatergic agonists that increase protein kinase C activation or decrease cyclic AMP formation may enhance the conversion of full-length APP to nonamyloidogenic APPs in Alzheimer's disease. 相似文献
20.
Phorbol Esters Increase Dopamine Transporter Phosphorylation and Decrease Transport Vmax 总被引:1,自引:1,他引:0
Robin A. Huff Roxanne A. Vaughan †Michael J. Kuhar ‡ George R. Uhl 《Journal of neurochemistry》1997,68(1):225-232
Abstract: Sodium- and chloride-coupled transport of dopamine from synapses into presynaptic terminals plays a key role in terminating dopaminergic neurotransmission. Regulation of the function of the dopamine transporter, the molecule responsible for this translocation, is thus of interest. The primary sequence of the dopamine transporter contains multiple potential phosphorylation sites, suggesting that the function of the transporter could be regulated by phosphorylation. Previous work from this laboratory has documented that phorbol ester activation of protein kinase C (PKC) decreases dopamine transport V max in transiently expressing COS cells. In the present report, we document in vivo phosphorylation of the rat dopamine transporter stably expressed in LLC-PK1 cells and show that phosphorylation is increased threefold by phorbol esters. Dopamine uptake is also regulated by phorbol esters in these cells; phorbol 12-myristate 13-acetate (PMA) reduces transport V max by 35%. Parallels between the time course, concentration dependency, and staurosporine sensitivity of alterations in transporter phosphorylation and transporter V max suggest that dopamine transporter phosphorylation involving PKC could contribute to this decreased transporter function. Phosphorylation of the dopamine transporter by PKC or by a PKC-activated kinase could be involved in rapid neuroadaptive processes in dopaminergic neurons. 相似文献