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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 62 (1994), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 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.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 55 (1990), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: DARPP-32, a dopamine- and cyclic AMP-regulated phosphoprotein of Mr 32,000, is phosphorylated in vitro by casein kinase II at a site which is also phosphorylated in intact cells. In the present study, we show that a protein kinase activity, present in caudate-putamen cytosol, phosphorylates DARPP-32 on a seryl residue located on the same thermolytic peptide that is phosphorylated by purified casein kinase II. This DARPP-32 serine kinase was indistinguishable from casein kinase II on the basis of a number of biochemical criteria. Excitotoxic lesions of the caudate-putamen and immunocytochemistry revealed the presence of casein kinase II in the medium-sized striatonigral neurons which are known to contain DARPP-32. Casein kinase II activity was high in all rat brain regions studied, and casein kinase II-like immunoreactivity was detected in most brain neurons, although some neuronal populations (e.g., cortical pyramidal cells and large striatal neurons) were stained more intensely than others. In rat caudate-putamen, 45% of the total casein kinase II activity was in the cytosol and 20% in the synaptosomal fraction. In mouse cerebral cortex and caudate-putamen, casein kinase II activity was high at embryonic day 16, and remained elevated during development. In addition to DARPP-32, several major substrates for casein kinase II were observed specifically in brain, but not in liver extracts. The high activity of casein kinase II in brain from the embryonic period to adult age and the existence of a number of specific substrates suggest that this enzyme may play an important role in both developing and mature brain, possibly in modulating the responsiveness of target proteins to various extracellular signals.
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  • 3
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: By means of the push-pull cannula method, the outflow of endogenous amino acids was studied in the striatum of halothane-anesthetized rats. Addition of K + ions (30 mM for 4 min) to the superfusion fluid increased the release of aspartate (+116%), glutamate (+ 217%), taurine (+109%), and γ-aminobutyric acid (GABA) (−429%) whereas a prolonged decrease in the outflow of glutamine (−28%) and a delayed reduction in the efflux of tyrosine (−25%) were observed. In the absence of Ca2-, the K+-induced release of aspartate, glutamate, and GABA was blocked whereas the K + -induced release of taurine was still present. Under these conditions, the decrease in glutamine efflux was reduced and that of tyrosine was abolished. Local application of tetrodotoxin (5 μM) decreased only the outflow of glutamate (-25%). One week following lesion of the ipsilateral sensorimotor cortex the spontaneous outflow of glutamine and of tyrosine was enhanced. Despite the lack of change in their spontaneous outflow, the K +-evoked release of aspartate and glutamate was less pronounced in lesioned than in control animals, whereas the K + -evoked changes in GABA and glutamine efflux were not modified. Our data indicate that the push-pull cannula method is a reliable approach for the study of the in vivo release of endogenous amino acids. In addition, they provide further evidence for a role for glutamate and aspartate as neuro-transmitters of corticostriatal neurons.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The distribution of inhibitor-1, a cyclic AMP-regulated inhibitor of protein phosphatase-1, was analyzed in various brain regions and peripheral tissues of various species by immunolabeling of sodium dodecyl sulfate-polyacrylamide gel transfers using specific antibodies. The distribution of inhibitor-1 was directly compared to that of DARPP-32, a structurally related cyclic AMP-regulated inhibitor of protein phosphatase-1. In rat CNS, a single immunoreactive protein of Mr 30,000, identified as inhibitor-1, was widely distributed. In contrast, DARPP-32 was highly concentrated in the basal ganglia. Inhibitor-1 was detected in brain tissue from frog (Mr 27,000), turtle (Mr 29,000/33,000), canary (Mr 26,000), pigeon (Mr 28,000), mouse (Mr 30,500), rabbit (Mr 26,500), cow (Mr 27,000), and monkey (Mr 27,500), but not from goldfish. Inhibitor-1 was detected at various levels in most peripheral tissues of the species studied; however, it was not detectable in certain tissues of particular species (e.g., rat and cow liver). DARPP-32 was detected in brain tissue of all the species tested except frog and goldfish, but was not detectable in most peripheral tissues. Both inhibitor-1 and DARPP-32 were concentrated in the cytosol and synaptosomal cytosol of rat striatum. The developmental expressions of inhibitor-1 and DARPP-32 in rat striatum differed: the level of inhibitor-1 peaked in the first postnatal week and then declined by the third postnatal week, whereas the level of DARPP-32 increased to a peak level by the third postnatal week and remained elevated thereafter. Because inhibitor-1 and DARPP-32 have distinct but partially overlapping regional distributions and developmental expression in rat CNS and have distinct tissue distributions in a number of species, it appears that their functions are not fully interchangeable.
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  • 5
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: DARPP-32 (dopamine- and cyclic AMP-regulated phosphoprotein, Mr= 32,000, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis) is a neuronal phosphoprotein that is enriched in neurons which possess dopamine D1 receptors, particularly striatonigral neurons. In rat brain slices, the phosphorylation state of DARPP-32 is regulated by dopamine, acting through the dopamine D1 receptor and the adenylyl cyclase system. This study reports that chronic blockade (21 days) of either dopamine D1 receptors by SCH-23390 or dopamine D2 receptors by raclopride does not affect the concentrations of DARPP-32 in specific rat brain regions (striatum, thalamus, hippocampus, frontal cerebral cortical pole). Northern blot analysis indicates that the steady-state level of DARPP-32 mRNA in striatum is also unchanged by these treatments.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 60 (1993), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: ARPP-21 is a cyclic AMP-regulated phosphoprotein (Mr= 21,000) that has a distribution in brain similar to that of DARPP-32 (dopamine- and cyclic AMP-regulated phosphoprotein, Mr= 32,000). It is enriched in the medium-sized spiny neurons in the striatum and in the striatonigral nerve terminals in the pars reticulata of the substantia nigra. The present study shows that dopamine D1 agonist SKF 38393 increases the state of phosphorylation of ARPP-21 by 26% in nigral slices and that pretreatment of the slices with D1 antagonist SCH 23390 blocks this effect. These results demonstrate that ARPP-21 is a dopamine-regulated phosphoprotein. Because D1 receptors are localized on nerve terminals of striatonigral pathway, the phosphorylation of ARPP-21 is likely to mediate some of the intracellular effects of dopamine on these terminals.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Using antiphosphotyrosine antibodies, we have investigated protein phosphorylation in mouse brain during development in intact animals and in reaggregated cerebral cultures. Under basal conditions, in vivo and in vitro, the levels of two main phosphoproteins, of Mr 120,000 and 180,000 (pp180), increased with development, reaching a maximum in the early postnatal period and decreasing thereafter. In adult forebrain, pp180 was still highly phosphorylated, but it was not detected in cerebellum or in peripheral tissues. In reaggregated cortical cultures, epidermal growth factor (EGF), type I insulin-like growth factor (IGF-I), and insulin enhanced protein tyrosine phosphorylation of several proteins, which were specific for EGF or IGF-I/insulin. In highly enriched neuronal or astrocytic monolayer cultures, some proteins phosphorylated in basal conditions, or in response to EGF and IGF-I, were found in both types of culture, whereas others appeared cell type specific. In addition, in each cell type, some proteins were phosphorylated under the action of both growth factors. These results indicate that tyrosine protein phosphorylation is maximal in mouse brain during development and is regulated by growth factors in neurons as well as in astrocytes.
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  • 8
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Pharmacology 44 (2004), S. 269-296 
    ISSN: 0362-1642
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Medicine , Chemistry and Pharmacology
    Notes: Dopamine- and cAMP-regulated phosphoprotein, Mr 32 kDa (DARPP-32), was identified initially as a major target for dopamine and protein kinase A (PKA) in striatum. However, recent advances now indicate that regulation of the state of DARPP-32 phosphorylation provides a mechanism for integrating information arriving at dopaminoceptive neurons, in multiple brain regions, via a variety of neurotransmitters, neuromodulators, neuropeptides, and steroid hormones. Activation of PKA or PKG stimulates DARPP-32 phosphorylation at Thr34 and thereby converts DARPP-32 into a potent inhibitor of protein phosphatase-1 (PP-1). DARPP-32 is also phosphorylated at Thr75 by Cdk5 and this converts DARPP-32 into an inhibitor of PKA. Thus, DARPP-32 has the unique property of being a dual-function protein, acting either as an inhibitor of PP-1 or of PKA. The state of phosphorylation of DARPP-32 at Thr34 depends on the phosphorylation state of two serine residues, Ser102 and Ser137, which are phosphorylated by CK2 and CK1, respectively. By virtue of its ability to modulate the activity of PP-1 and PKA, DARPP-32 is critically involved in regulating electrophysiological, transcriptional, and behavioral responses to physiological and pharmacological stimuli, including antidepressants, neuroleptics, and drugs of abuse.
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 77 (2001), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Cannabinoid receptors (CB1-R) are the target of a novel class of neuromodulators, the endocannabinoids. Yet, their signalling mechanisms in adult brain are poorly understood. We report that, in rat and mouse hippocampal slices, anandamide and 2-arachidonoylglycerol, synthetic cannabinoids, and Δ9-tetrahydrocannabinol activated p38 mitogen-activated protein kinases (MAPK), but not c-Jun N-terminal kinase (JNK). In contrast, lysophosphatidic acid (LPA), a lipid messenger acting on different receptors, increased both p38-MAPK and JNK phosphorylation. The effects of cannabinoids on p38-MAPK were mediated through activation of CB1-R because they were blocked in the presence of SR 141716 A and absent in CB1-R knockout mice, two conditions that did not alter the effects of LPA. The activation of p38-MAPK by cannabinoids was insensitive to inhibitors of Src. These results provide new insights into the cellular mechanisms by which cannabinoids exert their effects in hippocampus.
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  • 10
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: PEA-15 (phosphoprotein enriched in astrocytes, Mr = 15,000) is an acidic serine-phosphorylated protein highly expressed in the CNS, where it can play a protective role against cytokine-induced apoptosis. PEA-15 is a major substrate for protein kinase C. Endothelins, which are known to exert pleiotropic effects on astrocytes, were used to analyze further the processes involved in PEA-15 phosphorylation. Endothelin-1 or endothelin-3 (0.1 µM) induced a robust phosphorylation of PEA-15 that was abolished by the removal of extracellular calcium, but only diminished by inhibitors of protein kinase C. Microsequencing of phosphopeptides generated by digestion of PEA-15 following endothelin-1 treatment identified two phosphorylated residues: Ser104, previously recognized as the protein kinase C site, and a novel phosphoserine, Ser116, located in a consensus motif for either protein kinase casein kinase II or calcium/calmodulin-dependent protein kinase II (CaMKII). Partly purified PEA-15 was a substrate in vitro for CaMKII, but not for casein kinase II. Two-dimensional phosphopeptide mapping demonstrated that the site phosphorylated in vitro by CaMKII was also phosphorylated in intact astrocytes in response to endothelin. CaMKII phosphorylated selectively Ser116 and had no effect on Ser104, but in vitro phosphorylation by CaMKII appeared to facilitate further phosphorylation by protein kinase C. Treatment of intact astrocytes with okadaic acid enhanced the phosphorylation of the CaMKII site. These results demonstrate that PEA-15 is phosphorylated in astrocytes by CaMKII (or a related kinase) and by protein kinase C in response to endothelin.
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