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Dason JS, Allen AM, Vasquez OE, Sokolowski MB. Distinct functions of a cGMP-dependent protein kinase in nerve terminal growth and synaptic vesicle cycling. J Cell Sci 2019; 132:jcs.227165. [DOI: 10.1242/jcs.227165] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Accepted: 02/26/2019] [Indexed: 01/20/2023] Open
Abstract
Sustained neurotransmission requires the tight coupling of synaptic vesicle (SV) exocytosis and endocytosis. The mechanisms underlying this coupling are poorly understood. We tested the hypothesis that a cGMP-dependent protein kinase (PKG), encoded by the foraging (for) gene in Drosophila melanogaster, is critical for this process using a for null mutant, genomic rescues, and tissue specific rescues. We uncoupled FOR's exocytic and endocytic functions in neurotransmission using a temperature-sensitive shibire mutant in conjunction with fluorescein-assisted light inactivation of FOR. We discovered a dual role for presynaptic FOR, where FOR inhibits SV exocytosis during low frequency stimulation by negatively regulating presynaptic Ca2+ levels and maintains neurotransmission during high frequency stimulation by facilitating SV endocytosis. Additionally, glial FOR negatively regulated nerve terminal growth through TGF-β signaling and this developmental effect was independent from FOR's effects on neurotransmission. Overall, FOR plays a critical role in coupling SV exocytosis and endocytosis, thereby balancing these two components to maintain sustained neurotransmission.
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Affiliation(s)
- Jeffrey S. Dason
- Department of Cell & Systems Biology, University of Toronto, Toronto, Ontario, M5S 3B2, Canada
- Department of Biological Sciences, University of Windsor, Windsor, Ontario, N9B 3P4, Canada
| | - Aaron M. Allen
- Department of Cell & Systems Biology, University of Toronto, Toronto, Ontario, M5S 3B2, Canada
- Present Address: Centre for Neural Circuits and Behaviour, University of Oxford, OX1 3SR Oxford, UK
| | - Oscar E. Vasquez
- Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, Ontario, M5S 3B2, Canada
| | - Marla B. Sokolowski
- Department of Cell & Systems Biology, University of Toronto, Toronto, Ontario, M5S 3B2, Canada
- Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, Ontario, M5S 3B2, Canada
- Child and Brain Development Program, Canadian Institute for Advanced Research (CIFAR), Toronto, Ontario, M5G 1M1, Canada
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Lee JS, Song DW, Park JH, Kim JO, Cho C, Kim DH. miR-374 promotes myocardial hypertrophy by negatively regulating vascular endothelial growth factor receptor-1 signaling. BMB Rep 2018; 50:208-213. [PMID: 27802840 PMCID: PMC5437965 DOI: 10.5483/bmbrep.2017.50.4.165] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Indexed: 01/08/2023] Open
Abstract
Vascular endothelial growth factor (VEGF) is an essential cytokine that has functions in the formation of new blood vessels and regression of cardiac hypertrophy. VEGF/VEGF-receptor-1 (VEGFR1) signaling plays a key role in the regression of cardiac hypertrophy, whereas VEGF/VEGFR2 signaling leads to cardiac hypertrophy. In this study, we identified the prohypertrophic role of miR-374 using neonatal rat ventricular myocytes (NRVMs). Our results showed that overexpression of miR-374 activated G protein-coupled receptor-mediated prohypertrophic pathways by the inhibition of VEGFR1-dependent regression pathways. Luciferase assays revealed that miR-374 could directly target the 3'-untranslated regions of VEGFR1 and cGMP-dependent protein kinase-1. Collectively, these findings demonstrated that miR-374 was a novel pro-hypertrophic microRNA functioning to suppress the VEGFR1-mediated regression pathway. [BMB Reports 2017; 50(4): 208-213].
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Affiliation(s)
- Jong Sub Lee
- School of Life Sciences and Systems Biology Research Center, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Korea
| | - Dong Woo Song
- School of Life Sciences and Systems Biology Research Center, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Korea
| | - Jei Hyoung Park
- School of Life Sciences and Systems Biology Research Center, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Korea
| | - Jin Ock Kim
- School of Life Sciences and Systems Biology Research Center, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Korea
| | - Chunghee Cho
- School of Life Sciences and Systems Biology Research Center, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Korea
| | - Do Han Kim
- School of Life Sciences and Systems Biology Research Center, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Korea
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Hou J, Kang YJ. Regression of pathological cardiac hypertrophy: signaling pathways and therapeutic targets. Pharmacol Ther 2012; 135:337-54. [PMID: 22750195 DOI: 10.1016/j.pharmthera.2012.06.006] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Accepted: 06/12/2012] [Indexed: 02/05/2023]
Abstract
Pathological cardiac hypertrophy is a key risk factor for heart failure. It is associated with increased interstitial fibrosis, cell death and cardiac dysfunction. The progression of pathological cardiac hypertrophy has long been considered as irreversible. However, recent clinical observations and experimental studies have produced evidence showing the reversal of pathological cardiac hypertrophy. Left ventricle assist devices used in heart failure patients for bridging to transplantation not only improve peripheral circulation but also often cause reverse remodeling of the geometry and recovery of the function of the heart. Dietary supplementation with physiologically relevant levels of copper can reverse pathological cardiac hypertrophy in mice. Angiogenesis is essential and vascular endothelial growth factor (VEGF) is a constitutive factor for the regression. The action of VEGF is mediated by VEGF receptor-1, whose activation is linked to cyclic GMP-dependent protein kinase-1 (PKG-1) signaling pathways, and inhibition of cyclic GMP degradation leads to regression of pathological cardiac hypertrophy. Most of these pathways are regulated by hypoxia-inducible factor. Potential therapeutic targets for promoting the regression include: promotion of angiogenesis, selective enhancement of VEGF receptor-1 signaling pathways, stimulation of PKG-1 pathways, and sustention of hypoxia-inducible factor transcriptional activity. More exciting insights into the regression of pathological cardiac hypertrophy are emerging. The time of translating the concept of regression of pathological cardiac hypertrophy to clinical practice is coming.
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Affiliation(s)
- Jianglong Hou
- Regenerative Medicine Research Center, West China Hospital, Sichuan University, Chengdu, China
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Kupchik Y, Parnas H, Parnas I. A novel, extremely fast, feedback inhibition of glutamate release in the crayfish neuromuscular junction. Neuroscience 2011; 172:44-54. [DOI: 10.1016/j.neuroscience.2010.10.057] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2010] [Revised: 10/19/2010] [Accepted: 10/19/2010] [Indexed: 11/27/2022]
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Kiagiadaki F, Koulakis E, Thermos K. Dopamine (D1) receptor activation and nitrinergic agents influence somatostatin levels in rat retina. Exp Eye Res 2007; 86:18-24. [PMID: 17961553 DOI: 10.1016/j.exer.2007.09.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2007] [Revised: 08/09/2007] [Accepted: 09/04/2007] [Indexed: 10/22/2022]
Abstract
Somatostatin (SRIF) influences the release of two important neuromodulators of retinal circuitry, dopamine (DA) and nitric oxide (NO). The aim of the present study was to examine whether DA and NO modulate SRIF release in rat retina, and the mechanisms involved in their actions. Retinas of adult female Sprague--Dawley rats (250--300 g) were mechanically detached from the eyecup and ex vivo experiments were performed. Retinal explants were incubated in the presence of dopaminergic [DA (10 microM, 100 microM and 200 microM), apomorphine (nonselective D1/D2 agonist, 0.50 mM, 1.0 microM and 10 microM), A68930 (D1 selective agonist, 0.50 microM, 1.0 microM and 10 microM), quinpirole (D2 selective agonist, 0.50 microM, 1.0 microM and 10 microM), SCH 23390 (D1 selective antagonist, 250 nM and 500 nM) and sulpiride (D2 selective antagonist, 100 microM and 200 microM)], and nitrinergic agents [arginine (62.5 microM--5mM), SIN-1 (50 microM, 100 microM and 500 microM) and 8-Br-cGMP (50 microM, 250 microM and 500 microM)]. SRIF levels were quantified using radioimmunoassay (RIA). Dopamine had no effect on SRIF levels. Apomorphine produced a concentration dependent decrease and increase in SRIF levels, suggestive of pre- and postsynaptic effects. A68930 (10 microM) and SCH 23390 (250 nM and 500 nM) mimicked and reversed apomorphine's postsynaptic actions, respectively. Quinpirole had no effect, but blockade of D2 autoreceptors by sulpiride (200 microM) afforded an increase in SRIF levels. Arginine and SIN-1 increased, and 8-Br-cGMP attenuated SRIF levels. These results show that dopamine D1 receptors, and NO/peroxynitrite agents modulate SRIF release in the retina suggesting that the triad SRIF--DA--NO have reciprocal interactions via which they regulate retinal circuitry and vision transduction.
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Affiliation(s)
- Foteini Kiagiadaki
- Laboratory of Pharmacology, Department of Basic Sciences, Faculty of Medicine, University of Crete, Heraklion, Crete 71110 GR, Greece
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Cervia D, Bagnoli P. An update on somatostatin receptor signaling in native systems and new insights on their pathophysiology. Pharmacol Ther 2007; 116:322-41. [PMID: 17719647 DOI: 10.1016/j.pharmthera.2007.06.010] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2007] [Accepted: 06/28/2007] [Indexed: 12/20/2022]
Abstract
The peptide somatostatin (SRIF) has important physiological effects, mostly inhibitory, which have formed the basis for the clinical use of SRIF compounds. SRIF binding to its 5 guanine nucleotide-binding proteins-coupled receptors leads to the modulation of multiple transduction pathways. However, our current understanding of signaling exerted by receptors endogenously expressed in different cells/tissues reflects a rather complicated picture. On the other hand, the complexity of SRIF receptor signaling in pathologies, including pituitary and nervous system diseases, may be studied not only as alternative intervention points for the modulation of SRIF function but also to exploit new chemical space for drug-like molecules.
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Affiliation(s)
- Davide Cervia
- Department of Environmental Sciences, University of Tuscia, largo dell'Università snc, blocco D, 01100 Viterbo, Italy.
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Mastrodimou N, Kiagiadaki F, Hodjarova M, Karagianni E, Thermos K. Somatostatin receptors (sst2) regulate cGMP production in rat retina. ACTA ACUST UNITED AC 2005; 133:41-6. [PMID: 16280179 DOI: 10.1016/j.regpep.2005.09.034] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2005] [Accepted: 09/08/2005] [Indexed: 10/25/2022]
Abstract
The present study investigated the effect of somatostatin in the regulation of cGMP levels in rat retina and the mechanisms involved in this process. Isolated rat retinas were treated alone or in the presence of somatostatin (0.01-10 microM), BIM23014 (sst2 agonist, 0.01-10 microM), L-796,778 (sst3 agonist, 10 microM), somatostatin (0.1 microM) in combination with CYN154806 (sst2 antagonist, 1 microM), N(G)-methyl-L-arginine acetate salt (NMMA, inhibitor of the nitric oxide synthase (NOS), 250 microM), orthovanadate (inhibitor of tyrosine phosphatase, SHP-1, 1 microM), and arginine alone (250 microM). cGMP levels were quantified by ELISA. Immunohistochemistry studies were performed for the detection of cGMP and nNOS, while Western blot analysis was employed for the detection of SHP-1. Somatostatin increased cGMP levels in a concentration-dependent manner. This increase was inhibited by CYN154806. BIM23014 increased cGMP levels only at the concentration of 10 microM, while L-796,778 had no effect. NMMA blocked completely the somatostatin stimulated increase of cGMP levels and nNOS was detected in rat retina. cGMP immunoreactivity was observed primarily in bipolar cells only of nitroprusside-treated retinas. SHP-1 inhibition by orthovanadate reduced the somatostatin effect in a statistically significant manner. These results suggest that a SRIF/SHP-1/NO/cGMP mechanism underlies the actions of somatostatin in the retina and in its influence of retinal circuitry.
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Affiliation(s)
- Niki Mastrodimou
- Laboratory of Pharmacology, Department Basic Sciences, University of Crete, Faculty of Medicine, Heraklion, Crete, Greece
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Yu D, Eldred WD. Nitric oxide stimulates gamma-aminobutyric acid release and inhibits glycine release in retina. J Comp Neurol 2005; 483:278-91. [PMID: 15682393 PMCID: PMC1464839 DOI: 10.1002/cne.20416] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Nitric oxide (NO) modulates the uptake and/or release of neurotransmitters through a variety of cellular mechanisms. However, the pharmacological and biochemical processes underlying these neurochemical effects of NO often remain unclear. In our study, we used immunocytochemical methods to study the effects of NO, cyclic guanosine monophosphate (cGMP), and peroxynitrite on the uptake and release of gamma-aminobutyric acid (GABA) and glycine in the turtle retina. In addition, we examined the involvement of glutamate receptors, calcium, and the GABA transporter in this GABA uptake and release. We also tested for interactions between the GABAergic and glycinergic systems. In general, we show that NO stimulated GABA release and inhibited glycine release. The NO-stimulated GABA release involved calcium-dependent or calcium-independent synaptic release or reversal of the GABA transporter. Some effects of NO on GABA release involved glutamate, cGMP, or peroxynitrite. NO promoted glycine uptake and inhibited its release, and this inhibition of glycine release was influenced by GABAergic modulation. These findings indicate that NO modulates the levels of the inhibitory transmitters GABA and glycine through several specific biochemical mechanisms in different retinal cell types and layers. Thus it appears that some of the previously described reciprocal interactions between GABA and glycine in the retina function through specific NO signaling pathways.
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Affiliation(s)
- Dou Yu
- Department of Biology, Boston University, Boston, Massachusetts 02215, USA
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Vasilaki A, Mouratidou M, Schulz S, Thermos K. Somatostatin mediates nitric oxide production by activating sst(2) receptors in the rat retina. Neuropharmacology 2002; 43:899-909. [PMID: 12384175 DOI: 10.1016/s0028-3908(02)00181-8] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Somatostatin and its receptors (ssts) are found in the retina. Recent evidence suggested the involvement of sst(2A) and sst(2B) receptors in the regulation of nitric oxide (NO) (). In this study, we investigated further the localization of sst(1), sst(3)-sst(5), and the possible involvement of all subtypes, present in the rat retina, in the regulation of NO production. Polyclonal antibodies raised against sst(1), sst(3-5) were applied to 10-14 micro m cryostat sections of rat retinas fixed in paraformaldehyde. NADPH-diaphorase reactivity was assessed histochemically. The levels of NO in rat retinal explants were assessed by the production of its stable metabolites NO(2)(-) and NO(3)(-). sst(1) immunofluorescence was detected mainly in the retinal pigment epithelium, blood vessels of the inner retina, where it was colocalized with NADPH-diaphorase, and in processes of the inner plexiform layer (IPL). sst(4) immunohistochemistry was found in ganglion cell bodies, where it was colocalized with NADPH-diaphorase, processes of the IPL and ganglion cell layer, and optic nerve fibers. sst(3) or sst(5) immunostain was not detected. Somatostatin increased NO production and this effect was mimicked only by the sst(2) specific analog L-779976. The sst(2) antagonist CYN-154806 blocked the L-779976 increase of NO production. These results present conclusive evidence that somatostatin's role in the retina involves the regulation of NO by an sst(2) mechanism.
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Affiliation(s)
- A Vasilaki
- University of Crete, Faculty of Medicine, Department of Basic Sciences, Laboratory of Pharmacology, Heraclion, Crete, Greece
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Thiriet N, Aunis D, Zwiller J. The nitric oxide releasing agent sodium nitroprusside modulates cocaine-induced immediate early gene expression in rat brain. Ann N Y Acad Sci 2002; 965:47-54. [PMID: 12105084 DOI: 10.1111/j.1749-6632.2002.tb04150.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The nitric oxide (NO)/cGMP pathway triggers key events in synaptic phenomena involved in learning and memory. Using in situ hybridization, the present report demonstrates that NO released by sodium nitroprusside regulates egr-1, c-fos, and junB immediate early gene expression in rat forebrain. These genes, which are rapidly and transiently induced in response to diverse extracellular stimulation, coordinate alterations in gene expression underlying neuronal plasticity. Intracerebroventricular injection of sodium nitroprusside induced immediate early gene expression, which was highest in the nucleus accumbens. On the other hand, sodium nitroprusside abolished the cocaine-induced early gene expression in the dopaminergic projection fields nucleus accumbens, caudate-putamen, and frontal cortex. Further studies are warranted to explore the potential of the NO/cGMP/cGMP-dependent protein kinase pathway to modify cocaine-related behavioral effects.
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Fazel A, Li SC, Burton FR. Octreotide relaxes the hypertensive sphincter of Oddi: pathophysiological and therapeutic implications. Am J Gastroenterol 2002; 97:612-6. [PMID: 11922555 DOI: 10.1111/j.1572-0241.2002.05538.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
OBJECTIVES As our understanding of the pathophysiology of sphincter of Oddi dysfunction (SOD) expands, new avenues arise for pharmacological intervention. Recent evidence suggests that SOD results from a loss of myenteric plexus inhibitory neurons resulting in unopposed cholinergic tone. Octreotide inhibits postganglionic cholinergic neurons, and thus we hypothesize that administration of octreotide will decrease sphincteric pressure in individuals with SOD. METHODS Thirty-eight patients presenting with recurrent abdominal pain and SOD (basal pressure > 40 mm Hg) were studied. The study was prospective, placebo controlled, and blinded. Patient allocation was consecutive. Sphincter of Oddi manometry was performed in standard fashion. The test group (n = 19) received octreotide acetate (100 microg i.v.), and the control group (n = 19) received i.v. saline. Basal, phasic, and duct pressures as well as phasic amplitude and frequency were recorded before and 3 min after the i.v. infusion. Changes in these parameters before and after i.v. infusions were compared. RESULTS Octreotide caused a statistically significant reduction in peak and basal sphincter of Oddi pressures relative to saline (p < 0.01 and p < 0.001). Octreotide did not significantly affect wave amplitude, wave frequency, or duct pressure. CONCLUSIONS Octreotide has the potential to be a valuable addition to the armamentarium for the medical management of SOD.
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Affiliation(s)
- Ali Fazel
- Division of Gastroenterology and Hepatology, Saint Louis University School of Medicine, St. Mary's Health Center, Missouri 63110-0250, USA
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de Vente J, Asan E, Gambaryan S, Markerink-van Ittersum M, Axer H, Gallatz K, Lohmann SM, Palkovits M. Localization of cGMP-dependent protein kinase type II in rat brain. Neuroscience 2002; 108:27-49. [PMID: 11738129 DOI: 10.1016/s0306-4522(01)00401-8] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
In brain, signaling pathways initiated by atrial natriuretic peptide, or transmitters which stimulate nitric oxide synthesis, increase cGMP as their second messenger. One important class of target molecules for cGMP is cGMP-dependent protein kinases, and in the present study, biochemical and immunocytochemical analyses demonstrate the widespread distribution of type II cGMP-dependent protein kinase in rat brain, from the cerebral cortex to the brainstem and cerebellum. Also, colocalization of cGMP-dependent protein kinase type II with its activator, cGMP, was found in several brain regions examined after in vitro stimulation of brain slices with sodium nitroprusside. In western blots, cGMP-dependent protein kinase type II was observed in all brain regions examined, although cerebellar cortex and pituitary contained comparatively less of the kinase. Immunocytochemistry revealed cGMP-dependent protein kinase type II in certain neurons, and occasionally in putative oligodendrocytes and astrocytes, however, its most striking and predominant localization was in neuropil. Electron microscopy examination of neuropil in the medial habenula showed localization of the kinase in both axon terminals and dendrites. As a membrane-associated protein, cGMP-dependent protein kinase type II often appeared to be transported to cell processes to a greater extent than being retained in the cell body. Thus, immunocytochemical labeling of cGMP-dependent protein kinase type II often did not coincide with the localization of kinase mRNA previously observed by others using in situ hybridization. We conclude that in contrast to cGMP-dependent protein kinase type I, which has a very restricted localization to cerebellar Purkinje cells and a few other sites, cGMP-dependent protein kinase type II is a very ubiquitous brain protein kinase and thus a more likely candidate for relaying myriad cGMP effects in brain requiring protein phosphorylation.
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Affiliation(s)
- J de Vente
- European Graduate School of Neuroscience (EURON), Department of Psychiatry, Maastricht University, The Netherlands.
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Wei JY, Jin X, Cohen ED, Daw NW, Barnstable CJ. cGMP-induced presynaptic depression and postsynaptic facilitation at glutamatergic synapses in visual cortex. Brain Res 2002; 927:42-54. [PMID: 11814431 DOI: 10.1016/s0006-8993(01)03323-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The mechanisms by which the intracellular messenger cGMP can modulate synaptic efficacy remain poorly understood. Here we report that cGMP, acting through cGMP-dependent protein kinase (PKG), has multiple rapid and reversible effects on synaptic transmission in slices and cultures of rodent visual cortex. Extracellular application of the membrane permeable cGMP analog 8-bromoguanosine-3',5'-cyclic monophosphate (8-Br-cGMP) and the PKG specific activator beta-phenyl-1,N2-etheno-8-bromoguanosine-3',5'-cyclic monophosphorothioate sp-isomer (Sp-8-Br-PET-cGMPS) reduced stimulus-evoked EPSPs in slices. In cortical cultures, both analogs reduced the frequency of spontaneous EPSCs, but not their amplitude. In both slices and cultures, intracellular perfusion of the postsynaptic neurons with a pseudosubstrate inhibitory peptide specific for PKG had no effect on the reduction in EPSPs and EPSCs, indicating that the inhibition occurred at presynaptic sites. Whole-cell calcium currents in cultured cortical neurons were also reduced by both analogs, which may account for the effect on synaptic release. To determine whether cGMP was also acting at postsynaptic sites, we applied exogenous kainate/AMPA and NMDA to the recorded cells directly. cGMP and its analogs showed little effect on the postsynaptic kainate/AMPA responses but produced a dramatic enhancement of NMDA responses. cGMP-induced NMDA potentiation was prevented by the specific PKG inhibitory peptide infused into the postsynaptic cell. In summary, cGMP, acting through PKG, had depressive presynaptic and facilitatory postsynaptic actions at excitatory synapses in the visual cortex. We suggest that these opposing actions may be useful for altering the balance of synaptic inputs to cortical neurons in ways that enhance signals important for synaptic facilitation and neuronal plasticity.
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Affiliation(s)
- Ji Ye Wei
- Department of Ophthalmology and Visual Science, Yale University School of Medicine, 330 Cedar Street, P.O. Box 208061, New Haven, CT 06520-8061, USA
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Differential frequency-dependent regulation of transmitter release by endogenous nitric oxide at the amphibian neuromuscular synapse. J Neurosci 2001. [PMID: 11160378 DOI: 10.1523/jneurosci.21-04-01087.2001] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Nitric oxide (NO) is a potent neuromodulator in the CNS and PNS. At the frog neuromuscular junction (nmj), exogenous application of NO reduces neurotransmitter release, and NO synthases (NOSs), the enzymes producing NO, are present at this synapse. This work aimed at studying the molecular mechanisms by which NO modulates synaptic efficacy at the nmj using electrophysiological recordings and Ca(2+)-imaging techniques. Bath application of the NO donors S-nitroso-N-acetylpenicillamine (SNAP) and sodium nitroprusside decreased end plate potential (EPP) amplitude as well as the frequency of miniature EPPs but not their amplitude. Ca(2+) responses elicited in presynaptic terminals by single action potentials were unaffected by NO, but responses evoked by a short train of stimuli were increased. Tonic endogenous production of NO was observed as suggested by the increase in EPP amplitude by bath application of the NO scavenger hemoglobin and the neuronal NOS inhibitor 3-bromo-7-nitroindazole sodium salt. A soluble guanylate cyclase inhibitor, 6-anilino-5,8-quinolinedione (LY-83583), increased EPP amplitude and occluded the effects of the NO donor, suggesting that NO acts via a cGMP-dependent mechanism. High-frequency-induced depression was reduced in the presence of the NO scavenger but not by LY-83583. However, adenosine-induced depression was significantly reduced after bath perfusion of SNAP and in the presence of LY-83583. Our results indicate that NO regulates transmitter release and adenosine-induced depression via a cGMP-dependent mechanism that occurs after Ca(2+) entry and that high-frequency-induced synaptic depression is regulated by NO in a cGMP-independent manner.
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Esteve L, Lutz P, Thiriet N, Revel M, Aunis D, Zwiller J. Cyclic GMP-dependent protein kinase potentiates serotonin-induced Egr-1 binding activity in PC12 cells. Cell Signal 2001; 13:425-32. [PMID: 11384841 DOI: 10.1016/s0898-6568(01)00163-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The NO/cyclic GMP (cGMP) signal transduction pathway, which involves the cGMP-dependent protein kinase (PKG), regulates transcription of several genes, including immediate early genes. Using transfection experiments with the PKG-Ialpha cDNA cloned from human aorta, we show here that addition of membrane-permeable cGMP analogues to PC12 cells slightly upregulated ERK MAP (mitogen-activated protein) kinase. Likewise, PKG-Ialpha was found to activate weakly DNA binding activity of the Egr-1 transcription factor. On the other hand, PKG-Ialpha overexpression was shown to tremendously amplify the Egr-1 binding activity induced by the neurotransmitter serotonin, which activates egr-1 gene expression also via the stimulation of the ERK MAP kinase pathway. Since this potentiation occurred neither at the level of ERK nor at the egr-1 transcriptional level, the mechanism of amplification probably results from the convergence of ERK and PKG pathways at the level of the transcription factor Egr-1.
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Affiliation(s)
- L Esteve
- INSERM Unité U338, Centre de Neurochimie, 5, rue Blaise Pascal, Cedex 67084, Strasbourg, France
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