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Nasseri GG, Matin N, Wild AR, Tosefsky K, Flibotte S, Stacey RG, Hollman RB, Foster LJ, Bamji SX. Synaptic activity-dependent changes in the hippocampal palmitoylome. Sci Signal 2022; 15:eadd2519. [PMID: 36473050 DOI: 10.1126/scisignal.add2519] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Dynamic protein S-palmitoylation is critical for neuronal function, development, and synaptic plasticity. Synaptic activity-dependent changes in palmitoylation have been reported for a small number of proteins. Here, we characterized the palmitoylome in the hippocampi of male mice before and after context-dependent fear conditioning. Of the 121 differentially palmitoylated proteins identified, just over half were synaptic proteins, whereas others were associated with metabolic functions, cytoskeletal organization, and signal transduction. The synapse-associated proteins generally exhibited increased palmitoylation after fear conditioning. In contrast, most of the proteins that exhibited decreased palmitoylation were associated with metabolic processes. Similar results were seen in cultured rat hippocampal neurons in response to chemically induced long-term potentiation. Furthermore, we found that the palmitoylation of one of the synaptic proteins, plasticity-related gene-1 (PRG-1), also known as lipid phosphate phosphatase-related protein type 4 (LPPR4), was important for synaptic activity-induced insertion of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) into the postsynaptic membrane. The findings identify proteins whose dynamic palmitoylation may regulate their role in synaptic plasticity, learning, and memory.
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Affiliation(s)
- Glory G Nasseri
- Department of Cellular and Physiological Sciences, Life Sciences Institute and Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Nusrat Matin
- Department of Cellular and Physiological Sciences, Life Sciences Institute and Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Angela R Wild
- Department of Cellular and Physiological Sciences, Life Sciences Institute and Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Kira Tosefsky
- Department of Cellular and Physiological Sciences, Life Sciences Institute and Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Stephane Flibotte
- Life Sciences Institute Bioinformatics Facility, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - R Greg Stacey
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Rocio B Hollman
- Department of Cellular and Physiological Sciences, Life Sciences Institute and Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Leonard J Foster
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Shernaz X Bamji
- Department of Cellular and Physiological Sciences, Life Sciences Institute and Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
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Ortiz-Sanz C, Balantzategi U, Quintela-López T, Ruiz A, Luchena C, Zuazo-Ibarra J, Capetillo-Zarate E, Matute C, Zugaza JL, Alberdi E. Amyloid β / PKC-dependent alterations in NMDA receptor composition are detected in early stages of Alzheimer´s disease. Cell Death Dis 2022; 13:253. [PMID: 35306512 PMCID: PMC8934345 DOI: 10.1038/s41419-022-04687-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 02/07/2022] [Accepted: 02/24/2022] [Indexed: 12/15/2022]
Abstract
Amyloid beta (Aβ)-mediated synapse dysfunction is an early event in Alzheimer’s disease (AD) pathogenesis and previous studies suggest that NMDA receptor (NMDAR) dysregulation may contribute to these pathological effects. Although Aβ peptides impair NMDAR expression and activity, the mechanisms mediating these alterations in the early stages of AD are unclear. Here, we observed that NMDAR subunit NR2B and PSD-95 levels were aberrantly upregulated and correlated with Aβ42 load in human postsynaptic fractions of the prefrontal cortex in early stages of AD patients, as well as in the hippocampus of 3xTg-AD mice. Importantly, NR2B and PSD95 dysregulation was revealed by an increased expression of both proteins in Aβ-injected mouse hippocampi. In cultured neurons, Aβ oligomers increased the NR2B-containing NMDAR density in neuronal membranes and the NMDA-induced intracellular Ca2+ increase, in addition to colocalization in dendrites of NR2B subunit and PSD95. Mechanistically, Aβ oligomers required integrin β1 to promote synaptic location and function of NR2B-containing NMDARs and PSD95 by phosphorylation through classic PKCs. These results provide evidence that Aβ oligomers modify the contribution of NR2B to NMDAR composition and function in the early stages of AD through an integrin β1 and PKC-dependent pathway. These data reveal a novel role of Aβ oligomers in synaptic dysfunction that may be relevant to early-stage AD pathogenesis.
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Affiliation(s)
- Carolina Ortiz-Sanz
- Department of Neuroscience, University of Basque Country (UPV/EHU) and CIBERNED, Leioa, Spain.,Achucarro Basque Center for Neuroscience, Leioa, Spain
| | - Uxue Balantzategi
- Department of Neuroscience, University of Basque Country (UPV/EHU) and CIBERNED, Leioa, Spain.,Achucarro Basque Center for Neuroscience, Leioa, Spain
| | - Tania Quintela-López
- Department of Neuroscience, University of Basque Country (UPV/EHU) and CIBERNED, Leioa, Spain.,Achucarro Basque Center for Neuroscience, Leioa, Spain.,Department of Neuroscience, Physiology, & Pharmacology, University College London, London, UK
| | - Asier Ruiz
- Department of Neuroscience, University of Basque Country (UPV/EHU) and CIBERNED, Leioa, Spain.,Achucarro Basque Center for Neuroscience, Leioa, Spain
| | - Celia Luchena
- Department of Neuroscience, University of Basque Country (UPV/EHU) and CIBERNED, Leioa, Spain.,Achucarro Basque Center for Neuroscience, Leioa, Spain
| | - Jone Zuazo-Ibarra
- Department of Neuroscience, University of Basque Country (UPV/EHU) and CIBERNED, Leioa, Spain.,Achucarro Basque Center for Neuroscience, Leioa, Spain
| | - Estibaliz Capetillo-Zarate
- Department of Neuroscience, University of Basque Country (UPV/EHU) and CIBERNED, Leioa, Spain.,Achucarro Basque Center for Neuroscience, Leioa, Spain.,IKERBASQUE Basque Foundation for Science, Bilbao, Spain
| | - Carlos Matute
- Department of Neuroscience, University of Basque Country (UPV/EHU) and CIBERNED, Leioa, Spain.,Achucarro Basque Center for Neuroscience, Leioa, Spain
| | - José L Zugaza
- Achucarro Basque Center for Neuroscience, Leioa, Spain.,IKERBASQUE Basque Foundation for Science, Bilbao, Spain.,Department of Genetics, Physical Anthropology and Animal Physiology, UPV/EHU, Leioa, Spain
| | - Elena Alberdi
- Department of Neuroscience, University of Basque Country (UPV/EHU) and CIBERNED, Leioa, Spain. .,Achucarro Basque Center for Neuroscience, Leioa, Spain.
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3
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Jia R, Du J, Cao L, Feng W, He Q, Xu P, Yin G. Application of transcriptome analysis to understand the adverse effects of hydrogen peroxide exposure on brain function in common carp (Cyprinus carpio). ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2021; 286:117240. [PMID: 33991737 DOI: 10.1016/j.envpol.2021.117240] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 04/01/2021] [Accepted: 04/22/2021] [Indexed: 06/12/2023]
Abstract
Hydrogen peroxide (H2O2), as a common disinfectant, has been extensively used in aquaculture. The toxicity of high ambient H2O2 for gills and liver of fish has received attention from many researchers. However, whether H2O2 exposure induced brain injury and neurotoxicity has not been reported in fish. Therefore, this study aimed to explore the potential mechanism of H2O2 toxicity in brain of common carp via transcriptome analysis and biochemical parameter detection. The fish were exposed to 0 (control) and 1 mM of H2O2 for 1 h per day lasting 14 days. The results showed that H2O2 exposure caused oxidative damage in brain evidenced by decreased glutathione (GSH), total antioxidant capacity (T-AOC) and nicotinamide adenine dinucleotide (NAD+) levels, and increased formation of malondialdehyde (MDA) and 8-hydroxy-2'-deoxyguanosine (8-OHdG). Meanwhile, H2O2 exposure reduced 5-hydroxytryptamine (5-HT) level, and down-regulated tryptophan hydroxylase 1 (tph1a), tph2, 5-hydroxytryptamine receptor 1A-beta (htr1ab) and htr2b expression in brain. Transcriptome analysis showed that H2O2 exposure up-regulated 604 genes and down-regulated 1209 genes in brain. Go enrichment displayed that the differently expressed genes (DEGs) were enriched mainly in cellular process, single-organism process, metabolic process, and biological regulation in the biological process category. Further, KEGG enrichment indicated that H2O2 exposure led to dysregulation of neurotransmitter signals including depression of glutamatergic synapse, GABAergic synapse and endocannabinoid signaling. Also, we found the alteration of three key pathways including calcium, cAMP and HIF-1 in brain after H2O2 exposure. In conclusion, our data indicated that H2O2 exposure induced oxidative damage and neurotoxicity, possibly related to dysregulation of neurotransmitters and calcium, cAMP and HIF-1 signaling pathways, which may adversely affect learning, memory and social responses of common carp. This study provided novel insight into biological effects and underlying mechanism of H2O2 toxicity in aquatic animal, and contributed to proper application of H2O2 in aquaculture.
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Affiliation(s)
- Rui Jia
- Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture and Rural Affairs, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi, 214081, China; International Joint Research Laboratory for Fish Immunopharmacology, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi, 214081, China
| | - Jinliang Du
- Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture and Rural Affairs, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi, 214081, China; International Joint Research Laboratory for Fish Immunopharmacology, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi, 214081, China
| | - Liping Cao
- Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture and Rural Affairs, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi, 214081, China; International Joint Research Laboratory for Fish Immunopharmacology, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi, 214081, China
| | - Wenrong Feng
- Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture and Rural Affairs, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi, 214081, China; International Joint Research Laboratory for Fish Immunopharmacology, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi, 214081, China
| | - Qin He
- Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture and Rural Affairs, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi, 214081, China
| | - Pao Xu
- Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture and Rural Affairs, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi, 214081, China; International Joint Research Laboratory for Fish Immunopharmacology, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi, 214081, China
| | - Guojun Yin
- Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture and Rural Affairs, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi, 214081, China; International Joint Research Laboratory for Fish Immunopharmacology, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi, 214081, China.
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4
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Grubisha MJ, Sweet RA, MacDonald ML. Investigating Post-translational Modifications in Neuropsychiatric Disease: The Next Frontier in Human Post-mortem Brain Research. Front Mol Neurosci 2021; 14:689495. [PMID: 34335181 PMCID: PMC8322442 DOI: 10.3389/fnmol.2021.689495] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Accepted: 06/18/2021] [Indexed: 12/27/2022] Open
Abstract
Gene expression and translation have been extensively studied in human post-mortem brain tissue from subjects with psychiatric disease. Post-translational modifications (PTMs) have received less attention despite their implication by unbiased genetic studies and importance in regulating neuronal and circuit function. Here we review the rationale for studying PTMs in psychiatric disease, recent findings in human post-mortem tissue, the required controls for these types of studies, and highlight the emerging mass spectrometry approaches transforming this research direction.
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Affiliation(s)
- Melanie J. Grubisha
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA, United States
| | - Robert A. Sweet
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA, United States
| | - Matthew L. MacDonald
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA, United States
- Biomedical Mass Spectrometry Center, University of Pittsburgh, Pittsburgh, PA, United States
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5
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Davis-Reyes BD, Campbell VM, Land MA, Chapman HL, Stafford SJ, Anastasio NC. Profile of cortical N-methyl-D-aspartate receptor subunit expression associates with inherent motor impulsivity in rats. Biochem Pharmacol 2019; 168:204-213. [PMID: 31295463 PMCID: PMC6733662 DOI: 10.1016/j.bcp.2019.07.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Accepted: 07/07/2019] [Indexed: 01/01/2023]
Abstract
Impulsivity is a multifaceted behavioral manifestation with implications in several neuropsychiatric disorders. Glutamate neurotransmission through the N-methyl-D-aspartate receptors (NMDARs) in the medial prefrontal cortex (mPFC), an important brain region in decision-making and goal-directed behaviors, plays a key role in motor impulsivity. We discovered that inherent motor impulsivity predicted responsiveness to D-cycloserine (DCS), a partial NMDAR agonist, which prompted the hypothesis that inherent motor impulsivity is associated with the pattern of expression of cortical NMDAR subunits (GluN1, GluN2A, GluN2B), specifically the protein levels and synaptosomal trafficking of the NMDAR subunits. Outbred male Sprague-Dawley rats were identified as high (HI) or low (LI) impulsive using the one-choice serial reaction time task. Following phenotypic identification, mPFC synaptosomal protein was extracted from HI and LI rats to assess the expression pattern of the NMDAR subunits. Synaptosomal trafficking and stabilization for the GluN2 subunits were investigated by co-immunoprecipitation for postsynaptic density 95 (PSD95) and synapse associated protein 102 (SAP102). HI rats had lower mPFC GluN1 and GluN2A, but higher GluN2B and pGluN2B synaptosomal protein expression versus LI rats. Further, higher GluN2B:PSD95 and GluN2B:SAP102 protein:protein interactions were detected in HI versus LI rats. Thus, the mPFC NMDAR subunit expression pattern and/or synaptosomal trafficking associates with high inherent motor impulsivity. Increased understanding of the complex regulation of NMDAR balance within the mPFC as it relates to inherent motor impulsivity may lead to a better understanding of risk factors for impulse-control disorders.
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Affiliation(s)
- Brionna D Davis-Reyes
- Center for Addiction Research and Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX, USA
| | - Veronica M Campbell
- Center for Addiction Research and Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX, USA
| | - Michelle A Land
- Center for Addiction Research and Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX, USA
| | - Holly L Chapman
- Center for Addiction Research and Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX, USA
| | - Susan J Stafford
- Center for Addiction Research and Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX, USA
| | - Noelle C Anastasio
- Center for Addiction Research and Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX, USA.
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6
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Zhou XL, Zhang CJ, Peng YN, Wang Y, Xu HJ, Liu CM. ROR2 modulates neuropathic pain via phosphorylation of NMDA receptor subunit GluN2B in rats. Br J Anaesth 2018; 123:e239-e248. [PMID: 30916039 DOI: 10.1016/j.bja.2018.08.025] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Revised: 08/18/2018] [Accepted: 08/20/2018] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Neuropathic pain, a type of chronic pain as a result of direct central or peripheral nerve damage, is associated with significant quality of life and functional impairment. Its underlying mechanisms remain unclear. We investigated whether ROR2, a member of the receptor tyrosine kinase-like orphan receptor (ROR) family, participates in modulation of neuropathic pain. METHODS Thermal hyperalgesia and mechanical allodynia were measured using radiant heat and von Frey filament testing. Immunofluorescence staining was used to detect expression of ROR2 in neuronal nuclei. Fos expression was determined by immunocytochemistry. Phosphorylation status was detected by western blot and immunoprecipitation. Small interfering RNA was used to knock down ROR2 expression. RESULTS ROR2 was upregulated and activated in spinal neurones after chronic constriction injury (CCI) in mice [1.3 (0.1) to 2.1 (0.1)-fold of sham, P<0.01] from Day 1-21. CCI induced significant demethylation of the CpG island in the ROR2 gene promoter [0.37 (0.06) vs 0.12 (0.03)% CpG methylation, P<0.001]. Knockdown of ROR2 in the spinal cord prevented and reversed CCI-induced pain behaviours and spinal neuronal sensitisation [Fos expression: 130 (12) vs 81 (8) cells, P<0.05; 120 (11) vs 70 (7) cells, P<0.05]. In contrast, activation of spinal ROR2 by intrathecal injection of Wnt5a induced pain behaviours and spinal neuronal sensitisation [Fos expression: 11 (1) vs 100 (12) cells, P<0.001] in wild-type mice. Furthermore, ROR2-mediated pain modulation required phosphorylation of N-methyl-D-aspartate receptor 2B subunit (GluN2B) at Ser 1303 and Tyr1472 by pathways involving protein kinase C (PKC) and Src family kinases. Intrathecal injection of GluN2B, PKC, or Src family kinase-specific inhibitors significantly attenuated Wnt5a-induced pain behaviours. CONCLUSIONS ROR2 in the spinal cord regulates neuropathic pain via phosphorylation of GluN2B, suggesting a potential target for prevention and relief of neuropathic pain.
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Affiliation(s)
- X L Zhou
- Department of Anesthesiology, First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, China
| | - C J Zhang
- Department of Gastroenterology, Zhejiang Province People's Hospital, Hangzhou, Zhejiang, China
| | - Y N Peng
- Department of Anesthesiology, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, Jiangsu, China
| | - Y Wang
- Department of Anesthesiology, Taizhou People's Hospital, Taizhou, Jiangsu, China
| | - H J Xu
- Department of Anesthesiology, First People's Hospital of Shanghai Transportation University, Shanghai, China
| | - C M Liu
- Department of Anesthesiology, First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, China.
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Rahman A, Rao MS, Khan KM. Intraventricular infusion of quinolinic acid impairs spatial learning and memory in young rats: a novel mechanism of lead-induced neurotoxicity. J Neuroinflammation 2018; 15:263. [PMID: 30217162 PMCID: PMC6137743 DOI: 10.1186/s12974-018-1306-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 09/04/2018] [Indexed: 12/20/2022] Open
Abstract
Background Lead (Pb), a heavy metal, and quinolinic acid (QA), a metabolite of the kynurenine pathway of tryptophan metabolism, are known neurotoxicants. Both Pb and QA impair spatial learning and memory. Pb activates astrocytes and microglia, which in turn induce the synthesis of QA. We hypothesized increased QA production in response to Pb exposure as a novel mechanism of Pb-neurotoxicity. Methods Two experimental paradigms were used. In experiment one, Wistar rat pups were exposed to Pb via their dams’ drinking water from postnatal day 1 to 21. Control group was given regular water. In the second protocol, QA (9 mM) or normal saline (as Vehicle Control) was infused into right lateral ventricle of 21-day old rats for 7 days using osmotic pumps. Learning and memory were assessed by Morris water maze test on postnatal day 30 or 45 in both Pb- and QA-exposed rats. QA levels in the Pb exposed rats were measured in blood by ELISA and in the brain by immunohistochemistry on postnatal days 45 and 60. Expression of various molecules involved in learning and memory was analyzed by Western blot. Means of control and experimental groups were compared with two-way repeated measure ANOVA (learning) and t test (all other variables). Results Pb exposure increased QA level in the blood (by ~ 58%) and increased (p < 0.05) the number of QA-immunoreactive cells in the cortex, and CA1, CA3 and dentate gyrus regions of the hippocampus, compared to control rats. In separate experiments, QA infusion impaired learning and short-term memory similar to Pb. PSD-95, PP1, and PP2A were decreased (p < 0.05) in the QA-infused rats, whereas tau phosphorylation was increased, compared to vehicle infused rats. Conclusion Putting together the results of the two experimental paradigms, we propose that increased QA production in response to Pb exposure is a novel mechanism of Pb-induced neurotoxicity.
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Affiliation(s)
- Abdur Rahman
- Department of Food Science and Nutrition, College of Life Sciences, Kuwait University, Kuwait City, Kuwait.
| | - Muddanna S Rao
- Department of Anatomy, Faculty of Medicine, Kuwait University, Kuwait City, Kuwait
| | - Khalid M Khan
- Department of Anatomy, Faculty of Medicine, Kuwait University, Kuwait City, Kuwait
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8
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Berrout L, Isokawa M. Ghrelin upregulates the phosphorylation of the GluN2B subunit of the NMDA receptor by activating GHSR1a and Fyn in the rat hippocampus. Brain Res 2017; 1678:20-26. [PMID: 28993142 DOI: 10.1016/j.brainres.2017.09.028] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 09/03/2017] [Accepted: 09/24/2017] [Indexed: 11/18/2022]
Abstract
Ghrelin and its receptor GHSR1a have been shown to exert numerous physiological functions in the brain, in addition to the well-established orexigenic role in the hypothalamus. Earlier work indicated that ghrelin stimulated the phosphorylation of the GluN1 subunit of the NMDA receptor (NMDAR) and enhanced synaptic transmission in the hippocampus. In the present study, we report that the exogenous application of ghrelin increased GluN2B phosphorylation. This increase was independent of GluN2B subunit activity or NMDAR channel activity. However, it depended on the activation of GHSR1a and Fyn as it was blocked by D-Lys3-GHRP-6 and PP2, respectively. Inhibitors for G-protein-regulated second messengers, such as Rp-cAMP, H89, TBB, ryanodine, and thapsigargin, unexpectedly enhanced GluN2B phosphorylation, suggesting that cAMP, PKA, casein kinase II, and cytosolic calcium signaling may oppose to the effect of ghrelin on the phosphorylation of GluN2B. Our findings suggest that 1) GluN2B is likely a molecular target of ghrelin and GHSR1a-driven signaling cascades, and 2) the ghrelin-mediated phosphorylation of GluN2B depends on Fyn activation under complex negative regulation by other second messengers.
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Affiliation(s)
- Liza Berrout
- Department of Health and Biomedical Sciences, University of Texas Rio Grande Valley, 1W University Blvd., Brownsville, TX 78520, United States
| | - Masako Isokawa
- Department of Health and Biomedical Sciences, University of Texas Rio Grande Valley, 1W University Blvd., Brownsville, TX 78520, United States.
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9
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Ghafari M, Keihan Falsafi S, Höger H, Bennett KL, Lubec G. Identification of new phosphorylation sites of AMPA receptors in the rat hippocampus--A resource for neuroscience research. Proteomics Clin Appl 2015; 9:808-16. [PMID: 25656447 DOI: 10.1002/prca.201400057] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Revised: 10/16/2014] [Accepted: 02/03/2015] [Indexed: 12/14/2022]
Abstract
PURPOSE AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptors (AMPARs) are glutamate-gated ion channels that mediate the majority of fast excitatory synaptic transmissions in the mammalian brain. A series of phosphorylation sites have been predicted or identified and knowledge on phosphorylations is mandatory for understanding receptor biology and functions. EXPERIMENTAL DESIGN Immunoprecipitation from extracted hippocampal rat proteins was carried out using an antibody against the AMPAR GluA1 subunit, followed by identification of GluA1 and binding partners by MS. Bands from SDS-PAGE were picked, peptides were generated by trypsin and chymotrypsin digestion and identified by MS/MS (LTQ Orbitrap Velos). RESULTS Using Mascot as a search engine, phosphorylation sites S506, S645, S720, S849, S863, S895, T858, Y228, Y419, and T734 were found on GluA1; S357, S513, S656, S727, T243, T420, T741, Y 143, Y301,Y426 on GluA2; S301, S516, S657, S732, T222, and T746 were observed on GluA3; and S514, S653 was phosphorylated on GluA4. CONCLUSIONS AND CLINICAL RELEVANCE A series of additional protein modifications were observed and in particular, tyrosine and tryptophan nitrations on GluA1 were detected that may raise questions on additional regulation mechanisms for AMPARs in addition to phosphorylations. The findings are relevant for interpretation of previous work and design of future studies using AMPAR serving as a resource for neuroscience research and indeed, phosphorylations and PTMs per se would have to be respected when neuropathological and neurological disorders are being studied.
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Affiliation(s)
- Maryam Ghafari
- Department of Pediatrics, Medical University of Vienna, Vienna, Austria
| | | | - Harald Höger
- Core Unit of Biomedical Research, Division of Laboratory Animal Science and Genetics, Medical University of Vienna, Himberg, Austria
| | - Keiryn L Bennett
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria
| | - Gert Lubec
- Department of Pediatrics, Medical University of Vienna, Vienna, Austria
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10
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Jamal M, Ono J, Ameno K, Shirakami G, Tanaka N, Takakura A, Kinoshita H. Aldehyde dehydrogenase 2 deficiency increases resting-state glutamate and expression of the GluN1 subunit of N-methyl-D-aspartate receptor in the frontal cortex of mice. J Neurol Sci 2014; 348:46-50. [PMID: 25467136 DOI: 10.1016/j.jns.2014.10.041] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Revised: 10/01/2014] [Accepted: 10/30/2014] [Indexed: 11/25/2022]
Abstract
Our previous study showed that Aldh2-knockout (Aldh2-KO) mice, an animal model of inactive aldehyde dehydrogenase 2 (ALDH2), have better spatial memory when compared with wild-type (WT) mice. Given that the neurotransmitter glutamate has been associated with learning and memory, the goal of the present study was to investigate whether the strain-dependent difference in spatial memory was associated with changes in glutamate transmitter levels or receptor function in the frontal cortex of Aldh2-KO and WT mice. Thus, we first measured extracellular glutamate levels in free-moving mice using microdialysis. Second, we studied protein expression of the N-methyl-D-aspartate (NMDA) receptor (GluN1) subunit and the α-amino-3-hydroxy-5 methylisoxazole-4-propionic acid (AMPA) receptor (GluA1) subunit in lipid raft fractions using Western blot (WB). The samples were collected for WB, and lipid rafts were prepared from the insoluble fraction of homogenate tissue. Protein concentration was measured in the whole cell lysate (WCL) and in five separate lipid raft fractions. Cholesterol was also measured in all fractions 1-5. The microdialysis study revealed that basal glutamate concentration in the dialysates was approximately three-fold (0.27 ± 0.12 μM) higher in Aldh2-KO mice than in WT (0.10 ± 0.03 μM) mice. We also found an increase in the expression of GluN1 in Aldh2-KO mice compared with WT mice, both in the WCL and fraction 5, but GluA1 levels were unchanged as measured by WB. Our novel findings provide the first evidence for the role of ALDH2 in glutamate release and GluN1 protein expression in the frontal cortex. The observed strain differences in glutamate levels and GluN1 expression may suggest that enhanced glutamatergic function facilitates improved spatial memory in Aldh2-KO mice and such observation deserves further investigation.
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Affiliation(s)
- Mostofa Jamal
- Department of Forensic Medicine, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki, Kita, Kagawa 761-0793, Japan.
| | - Junichiro Ono
- Department of Anesthesiology and Emergency Medicine, Faculty of Medicine, Kagawa University, Japan
| | - Kiyoshi Ameno
- Department of Forensic Medicine, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki, Kita, Kagawa 761-0793, Japan
| | - Gotaro Shirakami
- Department of Anesthesiology and Emergency Medicine, Faculty of Medicine, Kagawa University, Japan
| | - Naoko Tanaka
- Department of Forensic Medicine, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki, Kita, Kagawa 761-0793, Japan
| | - Ayaka Takakura
- Department of Forensic Medicine, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki, Kita, Kagawa 761-0793, Japan
| | - Hiroshi Kinoshita
- Department of Forensic Medicine, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki, Kita, Kagawa 761-0793, Japan
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Lanuza MA, Santafe MM, Garcia N, Besalduch N, Tomàs M, Obis T, Priego M, Nelson PG, Tomàs J. Protein kinase C isoforms at the neuromuscular junction: localization and specific roles in neurotransmission and development. J Anat 2013; 224:61-73. [PMID: 24102585 DOI: 10.1111/joa.12106] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/07/2013] [Indexed: 11/29/2022] Open
Abstract
The protein kinase C family (PKC) regulates a variety of neural functions including neurotransmitter release. The selective activation of a wide range of PKC isoforms in different cells and domains is likely to contribute to the functional diversity of PKC phosphorylating activity. In this review, we describe the isoform localization, phosphorylation function, regulation and signalling of the PKC family at the neuromuscular junction. Data show the involvement of the PKC family in several important functions at the neuromuscular junction and in particular in the maturation of the synapse and the modulation of neurotransmission in the adult.
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Affiliation(s)
- Maria A Lanuza
- Unitat d'Histologia i Neurobiologia (UHN), Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, Reus, Spain
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12
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Schael S, Nüchel J, Müller S, Petermann P, Kormann J, Pérez-Otaño I, Martínez SM, Paulsson M, Plomann M. Casein kinase 2 phosphorylation of protein kinase C and casein kinase 2 substrate in neurons (PACSIN) 1 protein regulates neuronal spine formation. J Biol Chem 2013; 288:9303-12. [PMID: 23420842 DOI: 10.1074/jbc.m113.461293] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The PACSIN (protein kinase C and casein kinase 2 substrate in neurons) adapter proteins couple components of the clathrin-mediated endocytosis machinery with regulators of actin polymerization and thereby regulate the surface expression of specific receptors. The brain-specific PACSIN 1 is enriched at synapses and has been proposed to affect neuromorphogenesis and the formation and maturation of dendritic spines. In studies of how phosphorylation of PACSIN 1 contributes to neuronal function, we identified serine 358 as a specific site used by casein kinase 2 (CK2) in vitro and in vivo. Phosphorylated PACSIN 1 was found in neuronal cytosol and membrane fractions. This localization could be modulated by trophic factors such as brain-derived neurotrophic factor (BDNF). We further show that expression of a phospho-negative PACSIN 1 mutant, S358A, or inhibition of CK2 drastically reduces spine formation in neurons. We identified a novel protein complex containing the spine regulator Rac1, its GTPase-activating protein neuron-associated developmentally regulated protein (NADRIN), and PACSIN 1. CK2 phosphorylation of PACSIN 1 leads to a dissociation of the complex upon BDNF treatment and induces Rac1-dependent spine formation in dendrites of hippocampal neurons. These findings suggest that upon BDNF signaling PACSIN 1 is phosphorylated by CK2 which is essential for spine formation.
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Affiliation(s)
- Sylvia Schael
- Center for Biochemistry, University of Cologne, D-50931, Cologne, Germany
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13
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Regulation of phosphorylation at Ser(1303) of GluN2B receptor in the postsynaptic density. Neurochem Int 2012; 61:981-5. [PMID: 22982438 DOI: 10.1016/j.neuint.2012.08.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2012] [Revised: 08/02/2012] [Accepted: 08/30/2012] [Indexed: 11/22/2022]
Abstract
Neuronal N-methyl-D-aspartate subtype of ionotropic glutamate receptor (NMDAR) that plays essential roles in excitatory synaptic transmission is regulated by phosphorylation. However, the kinases and phosphatases involved in this regulation are not completely known. We show that the GluN2B subunit of NMDAR is phosphorylated at Ser(1303) by protein kinase C (PKC) and is dephosphorylated by protein phosphatase 1 (PP1), but not protein phosphatase 2A (PP2A) in isolated postsynaptic density (PSD). Although PSD is known to harbor PKC, PP1 and PP2A, their ability to regulate phosphorylation of GluN2B-Ser(1303) would depend on the accessibility of GluN2B-Ser(1303) to these proteins. Since PSD preparation is likely to maintain the organization of its component proteins as inside neurons, accessibility of kinases and phosphatases to GluN2B-Ser(1303)in vivo would be addressed by experiments using this system. Using an antibody specific for the phosphorylated state of GluN2B-Ser(1303) we demonstrate that PP1 is the major phosphatase in rat brain PSD that can dephosphorylate the GluN2B-Ser(1303) endogenous to PSD. We also show that PKC present in PSD can phosphorylate GluN2B-Ser(1303). The events reported here might be important in regulating GluN2B-Ser(1303) phosphorylation in vivo.
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14
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Bakshi K, Kosciuk M, Nagele RG, Friedman E, Wang HY. Prenatal cocaine exposure increases synaptic localization of a neuronal RasGEF, GRASP-1 via hyperphosphorylation of AMPAR anchoring protein, GRIP. PLoS One 2011; 6:e25019. [PMID: 21980374 PMCID: PMC3181332 DOI: 10.1371/journal.pone.0025019] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Accepted: 08/23/2011] [Indexed: 11/18/2022] Open
Abstract
Prenatal cocaine exposure causes sustained phosphorylation of the synaptic anchoring protein, glutamate receptor interacting protein (GRIP1/2), preventing synaptic targeting of the GluR2/3-containing alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-type glutamate receptors (AMPARs; J. Neurosci. 29: 6308–6319, 2009). Because overexpression of GRIP-associated neuronal rasGEF protein (GRASP-1) specifically reduces the synaptic targeting of AMPARs, we hypothesized that prenatal cocaine exposure enhances GRASP-1 synaptic membrane localization leading to hyper-activation of ras family proteins and heightened actin polymerization. Our results show a markedly increased GRIP1-associated GRASP-1 content with approximately 40% reduction in its rasGEF activity in frontal cortices (FCX) of 21-day-old (P21) prenatal cocaine-exposed rats. This cocaine effect is the result of a persistent protein kinase C (PKC)- and downstream Src tyrosine kinase-mediated GRIP phosphorylation. The hyperactivated PKC also increased membrane-associated GRASP-1 and activated small G-proteins RhoA, cdc42/Rac1 and Rap1 as well as filamentous actin (F-actin) levels without an effect on the phosphorylation state of actin. Since increased F-actin facilitates protein transport, our results suggest that increased GRASP-1 synaptic localization in prenatal cocaine-exposed brains is an adaptive response to restoring the synaptic expression of AMPA-GluR2/3. Our earlier data demonstrated that persistent PKC-mediated GRIP phosphorylation reduces GluR2/3 synaptic targeting in prenatal cocaine-exposed brains, we now show that the increased GRIP-associated GRASP-1 may contribute to the reduction in GluR2/3 synaptic expression and AMPAR signaling defects.
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Affiliation(s)
- Kalindi Bakshi
- Departments of Physiology, Pharmacology and Neuroscience, Sophie Davis School of Biomedical Education, The City University of New York Medical School, New York, New York, United States of America
- Department of Biology & Neuroscience, Graduate Center of the City University of New York, New York, New York, United States of America
- Center for Developmental Neuroscience/Institute for Basic Research/City University of New York Graduate School, Staten Island, New York, United States of America
| | - Mary Kosciuk
- New Jersey Institute for Successful Aging, University of Medicine and Dentistry New Jersey-School of Osteopathic Medicine, Stratford, New Jersey, United States of America
| | - Robert G. Nagele
- New Jersey Institute for Successful Aging, University of Medicine and Dentistry New Jersey-School of Osteopathic Medicine, Stratford, New Jersey, United States of America
| | - Eitan Friedman
- Departments of Physiology, Pharmacology and Neuroscience, Sophie Davis School of Biomedical Education, The City University of New York Medical School, New York, New York, United States of America
- Department of Biology & Neuroscience, Graduate Center of the City University of New York, New York, New York, United States of America
| | - Hoau-Yan Wang
- Departments of Physiology, Pharmacology and Neuroscience, Sophie Davis School of Biomedical Education, The City University of New York Medical School, New York, New York, United States of America
- Department of Biology & Neuroscience, Graduate Center of the City University of New York, New York, New York, United States of America
- * E-mail:
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15
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On the induction of postsynaptic granule cell-Purkinje neuron LTP and LTD. THE CEREBELLUM 2011; 9:284-90. [PMID: 20446074 DOI: 10.1007/s12311-010-0174-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
In the last decade, several experimental studies have demonstrated that particular patterns of synaptic activity can induce postsynaptic parallel fiber (PF) long-term potentiation (LTP). This form of plasticity can reverse postsynaptic PF long-term depression (LTD), which has been traditionally considered as the principal form of plasticity underlying cerebellar learning. Postsynaptic PF-LTP requires a transient increase in intracellular Ca(2+) concentration and, in contrast to PF-LTD, is induced without concomitant climbing fiber (CF) activation. Thus, it has been postulated that the polarity of long-term synaptic plasticity is determined by the amplitude of the Ca(2+) transient during the induction protocol, with PF-LTP induced by smaller Ca(2+) signals without concomitant CF activation. However, this hypothesis is contradicted by recent studies. A quantitative analysis of Ca(2+) signals associated with induction of PF-LTP indicates that the bidirectional induction of long-term plasticity is regulated by more complex mechanisms. Here we review the state-of-the-art of research on postsynaptic PF-LTP and PF-LTD and discuss the principal open questions on this topic.
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16
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17
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Tikhonov DB, Magazanik LG. Origin and Molecular Evolution of Ionotropic Glutamate Receptors. ACTA ACUST UNITED AC 2009; 39:763-73. [DOI: 10.1007/s11055-009-9195-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2008] [Indexed: 10/20/2022]
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18
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19
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Kitahara, Noriaki Takeda, Hiroshi K T. Molecular Mechanisms of Vestibular Compensation in the Central Vestibular System - Review. Acta Otolaryngol 2009. [DOI: 10.1080/00016489850182675-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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20
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Ishihama K, Kogo M, Wakisaka S, Turman JE. Prenatal development of NMDA receptor composition and function in trigeminal neurons. ACTA ACUST UNITED AC 2009; 68:321-35. [PMID: 16477151 DOI: 10.1679/aohc.68.321] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The prenatal development of neural circuits for rhythmical oral-motor behaviors used for feeding is essential for the survival of the newborn mammal. The N-methyl-D-aspartate (NMDA) receptor plays a critical role in brainstem circuits underlying postnatal oral-motor behaviors. To understand a role for the NMDA receptor in the emergence of sucking behavior we conducted physiological and immunohistochemical experiments using fetal rats. Physiology experiments examined the development of the NMDA dose response of the brainstem circuit responsible for generating rhythmical trigeminal activity by recording trigeminal motor outputs using an in vitro preparation. The high dose of NMDA agonist bath application affected the mean cycle duration of rhythmical trigeminal activity (RTA) at both embryonic day (E) 18-19 and E20-21 in comparison with standard concentration of NMDA agonist. NMDA receptor immunohistochemistry studies, using antibodies directed against subunits NR1, NR2A, NR2B, NR3A and NR3B were performed to determine the prenatal regulation of NMDA subunits in trigeminal motoneurons (Mo5), and mesencephalic trigeminal neurons (Me5) between E17 to E20. In Mo5, NR1, NR2A, NR2B and NR3A immunoreactivity was observed throughout the time frame sampled. NR3B immunoreactivity was not observed in Mo5 or Me5. In Mo5, there was a significant decrease in the percentage of NR2B immunoreactive neurons between E17 and E20, and a concurrent increase in the NR2A/NR2B ratio between E17 and E20. In Me5, NR1, NR2A and NR3A immunoreactivity was observed throughout the time frame sampled; a significant decrease in the percentage of NR2A immunoreactive neurons between E17 and E20, and NR3A immunoreactive neurons between E17 and E18 occurred. The timing of subunit changes between E17 and E18 is coincident with the prenatal emergence of rhythmical jaw movements, and in vitro rhythmical trigeminal activity, shown in earlier studies. Our data suggest that NMDA receptor plays an important role in the development and function of prenatal oral-motor circuits.
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Affiliation(s)
- Kohji Ishihama
- First Department of Oral and Maxillofacial Surgery, Osaka University Graduate School of Dentistry, Japan
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21
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Chen N, Chen X, Wang JH. Homeostasis established by coordination of subcellular compartment plasticity improves spike encoding. J Cell Sci 2008; 121:2961-71. [PMID: 18697837 DOI: 10.1242/jcs.022368] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Homeostasis in cells maintains their survival and functions. The plasticity at neurons and synapses may destabilize their signal encoding. The rapid recovery of cellular homeostasis is needed to secure the precise and reliable encoding of neural signals necessary for well-organized behaviors. We report a homeostatic process that is rapidly established through Ca(2+)-induced coordination of functional plasticity among subcellular compartments. An elevation of cytoplasmic Ca(2+) levels raises the threshold potentials and refractory periods of somatic spikes, and strengthens the signal transmission at glutamatergic and GABAergic synapses, in which synaptic potentiation shortens refractory periods and lowers threshold potentials. Ca(2+) signals also induce an inverse change of membrane excitability at the soma versus the axon. The integrative effect of Ca(2+)-induced plasticity among the subcellular compartments is homeostatic in nature, because it stabilizes neuronal activities and improves spike timing precision. Our study of neuronal homeostasis that is fulfilled by rapidly coordinating subcellular compartments to improve neuronal encoding sheds light on exploring homeostatic mechanisms in other cell types.
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Affiliation(s)
- Na Chen
- State Key Labs for Macrobiomolecules and Brain and Cognitive Sciences, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, The People's Republic of China
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22
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Roche KW, Huganir RL. Detection of protein phosphorylation in tissues and cells. ACTA ACUST UNITED AC 2008; Chapter 5:Unit 5.14. [PMID: 18428497 DOI: 10.1002/0471142301.ns0514s11] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Phosphorylation is one of the principal regulatory mechanisms in the nervous system. Several different procedures used to characterize the phosphorylation state of neuronal proteins are described in this unit, including analysis of phosphorylation in situ, phosphoamino acid analysis, and phosphopeptide map analysis. In addition, there is a protocol describing in vitro phosphorylation of fusion proteins. These methods are often combined to provide a comprehensive evaluation of the phosphorylation state of a particular protein.
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Affiliation(s)
- K W Roche
- National Institute on Deafness and other Communication Disorders, NIH, Bethesda, Maryland, USA
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23
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Zou Q, Destexhe A. Kinetic models of spike-timing dependent plasticity and their functional consequences in detecting correlations. BIOLOGICAL CYBERNETICS 2007; 97:81-97. [PMID: 17530277 DOI: 10.1007/s00422-007-0155-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2006] [Accepted: 03/30/2007] [Indexed: 05/15/2023]
Abstract
Spike-timing dependent plasticity (STDP) is a type of synaptic modification found relatively recently, but the underlying biophysical mechanisms are still unclear. Several models of STDP have been proposed, and differ by their implementation, and in particular how synaptic weights saturate to their minimal and maximal values. We analyze here kinetic models of transmitter-receptor interaction and derive a series of STDP models. In general, such kinetic models predict progressive saturation of the weights. Various forms can be obtained depending on the hypotheses made in the kinetic model, and these include a simple linear dependence on the value of the weight ("soft bounds"), mixed soft and abrupt saturation ("hard bound"), or more complex forms. We analyze in more detail simple soft-bound models of Hebbian and anti-Hebbian STDPs, in which nonlinear spike interactions (triplets) are taken into account. We show that Hebbian STDPs can be used to selectively potentiate synapses that are correlated in time, while anti-Hebbian STDPs depress correlated synapses, despite the presence of nonlinear spike interactions. This correlation detection enables neurons to develop a selectivity to correlated inputs. We also examine different versions of kinetics-based STDP models and compare their sensitivity to correlations. We conclude that kinetic models generally predict soft-bound dynamics, and that such models seem ideal for detecting correlations among large numbers of inputs.
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Affiliation(s)
- Quan Zou
- Integrative and Computational Neuroscience Unit, CNRS, 1 Avenue de la Terrasse, 91198, Gif-sur-Yvette, France
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24
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Chen BS, Roche KW. Regulation of NMDA receptors by phosphorylation. Neuropharmacology 2007; 53:362-8. [PMID: 17644144 PMCID: PMC2001266 DOI: 10.1016/j.neuropharm.2007.05.018] [Citation(s) in RCA: 299] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2007] [Accepted: 05/21/2007] [Indexed: 11/18/2022]
Abstract
N-methyl-D-aspartate (NMDA) receptors are critical for neuronal development and synaptic plasticity. The molecular mechanisms underlying the synaptic localization and functional regulation of NMDA receptors have been the subject of extensive studies. In particular, phosphorylation has emerged as a fundamental mechanism that regulates NMDA receptor trafficking and can alter the channel properties of NMDA receptors. Here we summarize recent advances in the characterization of NMDA receptor phosphorylation, emphasizing subunit-specific phosphorylation, which differentially controls the trafficking and surface expression of NMDA receptors.
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Affiliation(s)
- Bo-Shiun Chen
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.
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25
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Shukla K, Kim J, Blundell J, Powell CM. Learning-induced glutamate receptor phosphorylation resembles that induced by long term potentiation. J Biol Chem 2007; 282:18100-18107. [PMID: 17472959 PMCID: PMC3910102 DOI: 10.1074/jbc.m702906200] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Long term potentiation and long term depression of synaptic responses in the hippocampus are thought to be critical for certain forms of learning and memory, although until recently it has been difficult to demonstrate that long term potentiation or long term depression occurs during hippocampus-dependent learning. Induction of long term potentiation or long term depression in hippocampal slices in vitro modulates phosphorylation of the alpha-amino-3-hydrozy-5-methylisoxazole-4-propionic acid subtype of glutamate receptor subunit GluR1 at distinct phosphorylation sites. In long term potentiation, GluR1 phosphorylation is increased at the Ca2+/calmodulin-dependent protein kinase and protein kinase C site serine 831, whereas in long term depression, phosphorylation of the protein kinase A site serine 845 is decreased. Indeed, phosphorylation of one or both of these sites is required for long term synaptic plasticity and for certain forms of learning and memory. Here we demonstrate that training in a hippocampus-dependent learning task, contextual fear conditioning is associated with increased phosphorylation of GluR1 at serine 831 in the hippocampal formation. This increased phosphorylation is specific to learning, has a similar time course to that in long term potentiation, and like memory and long term potentiation, is dependent on N-methyl-D-aspartate receptor activation during training. Furthermore, the learning-induced increase in serine 831 phosphorylation is present at synapses and is in heteromeric complexes with the glutamate receptor subunit GluR2. These data indicate that a biochemical correlate of long term potentiation occurs at synapses in receptor complexes in a final, downstream, postsynaptic effector of long term potentiation during learning in vivo, further strengthening the link between long term potentiation and memory.
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Affiliation(s)
- Kajal Shukla
- Departments of Neurology and Psychiatry, The University of Texas Southwestern Medical Center, Dallas, Texas 75390-8813
| | - James Kim
- Departments of Neurology and Psychiatry, The University of Texas Southwestern Medical Center, Dallas, Texas 75390-8813
| | - Jacqueline Blundell
- Departments of Neurology and Psychiatry, The University of Texas Southwestern Medical Center, Dallas, Texas 75390-8813
| | - Craig M Powell
- Departments of Neurology and Psychiatry, The University of Texas Southwestern Medical Center, Dallas, Texas 75390-8813.
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26
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Manev R, Mrazovac D, Manev H. Possible role for interactions between 5-lipoxygenase (5-LOX) and AMPA GluR1 receptors in depression and in antidepressant therapy. Med Hypotheses 2007; 69:1076-9. [PMID: 17449191 PMCID: PMC2719960 DOI: 10.1016/j.mehy.2007.02.038] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2007] [Accepted: 02/22/2007] [Indexed: 10/23/2022]
Abstract
Emerging evidence suggests that 5-lipoxygenase (5-LOX) plays a role in central nervous system functioning. It has been shown that 5-LOX metabolic products can decrease the phosphorylation of the glutamate receptor subunit GluR1, and that this effect can be antagonized by 5-LOX inhibitors. Recent concepts about the pathobiological mechanisms of depression and the molecular mechanisms of antidepressant activity postulate a significant role for glutamatergic neurotransmission and the GluR1 receptor. Regulation of GluR1 phosphorylation, i.e., enhancement of this phosphorylation, may be a part of antidepressant activity. On the other hand, reduced GluR1 phosphorylation may be a pathobiological mechanism contributing to depression. Since 5-LOX inhibitors, along with antidepressants share the capacity to increase GluR1 phosphorylation, we hypothesize that they may also have antidepressant properties. Furthermore, we postulate that increased brain 5-LOX expression may lead to decreased GluR1 phosphorylation and favor the development of depression. For example, brain 5-LOX expression is stimulated by stress hormone glucocorticoids, and stress is a known contributing factor in depression.
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Affiliation(s)
- Radmila Manev
- Department of Psychiatry and the Psychiatric Institute, University of Illinois at Chicago, 1601 West Taylor Street, M/C912, Chicago, IL 60612, USA
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27
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Gupta H, Verma D, Ahuja RK, Srivastava DN, Wadhwa S, Ray SB. Intrathecal co-administration of morphine and nimodipine produces higher antinociceptive effect by synergistic interaction as evident by injecting different doses of each drug in rats. Eur J Pharmacol 2007; 561:46-53. [PMID: 17320072 DOI: 10.1016/j.ejphar.2007.01.023] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2006] [Revised: 11/21/2006] [Accepted: 01/08/2007] [Indexed: 11/17/2022]
Abstract
Earlier, we reported that morphine-nimodipine combination produces significantly higher antinociception after intrathecal but not after systemic administration in mice. Different doses of morphine and nimodipine (5 microg of morphine, 5 microg of nimodipine, 5 microg each of morphine and nimodipine, 10 microg of morphine, 10 microg of nimodipine, 10 microg morphine with 5 microg nimodipine and 5 microg of morphine with 10 microg of nimodipine) were now injected intrathecally in Wistar rats to further characterise this antinociceptive effect. The acute antinociceptive effect was measured by the tail-flick test between 15 min to 7 h. The onset of maximum antinociception (100% MPE) was earlier (by 15 min) in nimodipine (5 microg) than in morphine (5 microg) treated group (by 30 min). Though earlier in onset, 5 microg nimodipine produced transient antinociception, which was significantly higher than saline treated controls for the initial 30 min only. Morphine (5 microg) produced significantly higher antinociception between 15 min to 3:30 h in comparison to control animals. However, co-administration of both morphine and nimodipine led to significantly higher antinociception than morphine alone at 4:00 h and also between 5:00 to 6:30 h. Interestingly, the combined antinociceptive action of morphine and nimodipine was not significantly different from 10 microg of morphine, which indicated synergistic interaction. Naloxone (5 mg/kg) could reverse this antinociceptive effect of morphine-nimodipine combination though it failed to reverse nimodipine (5 microg)-mediated antinociception at 15 min. Increasing the dose of either morphine or nimodipine to 10 mug did not increase antinociception except between 6:30-7:00 h. No obvious side effect was noted after administration of either morphine or nimodipine or both.
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Affiliation(s)
- Himanshu Gupta
- Department of Anatomy, All India Institute of Medical Sciences, New Delhi 110 029, India
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Imbesi M, Zavoreo I, Uz T, Sharma RP, Dimitrijevic N, Manev H, Manev R. 5-Lipoxygenase inhibitor MK-886 increases GluR1 phosphorylation in neuronal cultures in vitro and in the mouse cortex in vivo. Brain Res 2007; 1147:148-53. [PMID: 17349982 DOI: 10.1016/j.brainres.2007.02.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2006] [Revised: 02/07/2007] [Accepted: 02/08/2007] [Indexed: 10/23/2022]
Abstract
Modifications of AMPA glutamate receptor GluR1 phosphorylation are critical for neuroplastic mechanisms. Previous in vitro studies in brain slices employed MK-886, a functional inhibitor of the enzyme 5-lipoxygenase (5-LOX), and found increased GluR1 phosphorylation. Since slice preparations have accompanying postmortem phosphorylation changes, e.g., decreased GluR1 phosphorylation, it remains to be clarified whether MK-886 can affect GluR1 phosphorylation in intact neurons and in the brain in vivo. We used primary neuronal cultures prepared from embryonic mouse brain and in vivo drug administration to investigate the effects of MK-886 on GluR1 phosphorylation using quantitative Western immunoblotting assays. In vitro, MK-886 increased GluR1 phosphorylation at both serine 831 and serine 845. In vivo, repeated but not a single MK-886 injection increased GluR1 phosphorylation in the prefrontal cortex. These findings indicate that MK-886 has an intrinsic effect on neuronal phosphorylation both in vitro and in vivo and support the use of MK-886 as a pharmacological tool in studies of not only the 5-LOX pathway but also neuronal GluR1 functioning.
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Affiliation(s)
- Marta Imbesi
- The Psychiatric Institute, Department of Psychiatry, University of Illinois at Chicago, 1601 West Taylor Street, MC912, Chicago, IL 60612, USA
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29
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Daw MI, Scott HL, Isaac JTR. Developmental synaptic plasticity at the thalamocortical input to barrel cortex: mechanisms and roles. Mol Cell Neurosci 2007; 34:493-502. [PMID: 17329121 PMCID: PMC1952688 DOI: 10.1016/j.mcn.2007.01.001] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2006] [Revised: 12/21/2006] [Accepted: 01/03/2007] [Indexed: 11/28/2022] Open
Abstract
The thalamocortical (TC) input to layer IV provides the major pathway for ascending sensory information to the mammalian sensory cortex. During development there is a dramatic refinement of this input that underlies the maturation of the topographical map in layer IV. Over the last 10 years our understanding of the mechanisms of the developmental and experience-driven changes in synaptic function at TC synapses has been greatly advanced. Here we describe these studies that point to a key role for NMDA receptor-dependent synaptic plasticity, a role for kainate receptors and for a rapid maturation in GABAergic inhibition. The expression mechanisms of some of the forms of neonatal synaptic plasticity are novel and, in combination with other mechanisms, produce a layer IV circuit that exhibits functional properties necessary for mature sensory processing.
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Affiliation(s)
- Michael I Daw
- MRC Centre for Synaptic Plasticity, Department of Anatomy, University of Bristol, University Walk, Bristol BS8 1TD, UK.
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30
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Bruneau EG, Akaaboune M. The dynamics of recycled acetylcholine receptors at the neuromuscular junction in vivo. Development 2006; 133:4485-93. [PMID: 17050625 DOI: 10.1242/dev.02619] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
At the peripheral neuromuscular junction (NMJ), a significant number of nicotinic acetylcholine receptors (AChRs) recycle back into the postsynaptic membrane after internalization to intermingle with not-yet-internalized ;pre-existing' AChRs. However, the way in which these receptor pools are maintained and regulated at the NMJ in living animals remains unknown. Here, we demonstrate that recycled receptors in functional synapses are removed approximately four times faster than pre-existing receptors, and that most removed recycled receptors are replaced by new recycled ones. In denervated NMJs, the recycling of AChRs is significantly depressed and their removal rate increased, whereas direct muscle stimulation prevents their loss. Furthermore, we show that protein tyrosine phosphatase inhibitors cause the selective accumulation of recycled AChRs in the peri-synaptic membrane without affecting the pre-existing AChR pool. The inhibition of serine/threonine phosphatases, however, has no effect on AChR recycling. These data show that recycled receptors are remarkably dynamic, and suggest a potential role for tyrosine dephosphorylation in the insertion and maintenance of recycled AChRs at the postsynaptic membrane. These findings may provide insights into long-term recycling processes at less accessible synapses in the central nervous system in vivo.
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Affiliation(s)
- Emile G Bruneau
- Department of Molecular, Cellular and Developmental Biology and Neuroscience Program, University of Michigan, 830 North University Avenue, Ann Arbor, MI 48109, USA
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31
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Chao X, Muff TJ, Park SY, Zhang S, Pollard AM, Ordal GW, Bilwes AM, Crane BR. A receptor-modifying deamidase in complex with a signaling phosphatase reveals reciprocal regulation. Cell 2006; 124:561-71. [PMID: 16469702 DOI: 10.1016/j.cell.2005.11.046] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2005] [Revised: 09/22/2005] [Accepted: 11/15/2005] [Indexed: 12/30/2022]
Abstract
Signal transduction underlying bacterial chemotaxis involves excitatory phosphorylation and feedback control through deamidation and methylation of sensory receptors. The structure of a complex between the signal-terminating phosphatase, CheC, and the receptor-modifying deamidase, CheD, reveals how CheC mimics receptor substrates to inhibit CheD and how CheD stimulates CheC phosphatase activity. CheD resembles other cysteine deamidases from bacterial pathogens that inactivate host Rho-GTPases. CheD not only deamidates receptor glutamine residues contained within a conserved structural motif but also hydrolyzes glutamyl-methyl-esters at select regulatory positions. Substituting Gln into the receptor motif of CheC turns the inhibitor into a CheD substrate. Phospho-CheY, the intracellular signal and CheC target, stabilizes the CheC:CheD complex and reduces availability of CheD. A point mutation that dissociates CheC from CheD impairs chemotaxis in vivo. Thus, CheC incorporates an element of an upstream receptor to influence both its own effect on receptor output and that of its binding partner, CheD.
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Affiliation(s)
- Xingjuan Chao
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
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32
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Zhang X, Wu J, Lei Y, Fang L, Willis WD. Protein phosphatase modulates the phosphorylation of spinal cord NMDA receptors in rats following intradermal injection of capsaicin. ACTA ACUST UNITED AC 2005; 138:264-72. [PMID: 15919130 DOI: 10.1016/j.molbrainres.2005.05.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2004] [Revised: 04/07/2005] [Accepted: 05/01/2005] [Indexed: 11/21/2022]
Abstract
The present study investigates the role of serine/threonine protein phosphatase 2A (PP2A) in the modulation of the phosphorylation of the NR1 and NR2B subunits of NMDA receptors in the spinal cord of rats following intradermal injection of capsaicin. The effects of a specific inhibitor of PP2A, fostriecin, on the expression of NR1, phospho-NR1, NR2B, and phospho-NR2B subunits of the NMDA receptor in the spinal cord of rats following noxious stimulation were examined. After continually perfusing with ACSF or fostriecin (3 microM) through a previously implanted microdialysis fiber for 30 min, central sensitization was initiated by injection of capsaicin into the plantar surface of the left paw of rats. The spinal cord was removed at different time points (30, 60, 90, 120, 180 min) after intradermal injection of capsaicin. Western blots were performed to examine the expression of NMDA subunits in spinal cord tissue by using specific antibodies. We found that the upregulated phosphorylation of both NR1 and NR2B subunits induced by capsaicin injection was significantly potentiated by the PP2A inhibitor without affecting the NR1 and NR2B protein itself. These results suggest that PP2A may have a regulatory effect on central sensitization induced by noxious stimuli in the periphery by regulating the phosphorylation state of NMDA receptors.
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Affiliation(s)
- Xuan Zhang
- Department of Neuroscience and Cell Biology, The University of Texas Medical Branch, Galveston, TX 77555-1069, USA
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33
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Qiu S, Korwek KM, Weeber EJ. A fresh look at an ancient receptor family: emerging roles for low density lipoprotein receptors in synaptic plasticity and memory formation. Neurobiol Learn Mem 2005; 85:16-29. [PMID: 16198608 DOI: 10.1016/j.nlm.2005.08.009] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2005] [Revised: 07/30/2005] [Accepted: 08/11/2005] [Indexed: 01/11/2023]
Abstract
The well-known family of low-density lipoprotein receptors represents a collection of ancient membrane receptors that have been remarkably conserved throughout evolution. These multifunctional receptors, known to regulate cholesterol transport, are becoming increasingly interesting to the neuroscience community due to their ability to transduce a diversity of extracellular signals across the membrane in the adult CNS. Their roles in modulating synaptic plasticity and necessity in hippocampus-specific learning and memory have recently come to light. In addition, genetic, biochemical and behavioral studies have implicated these signaling systems in a number of human neurodegenerative and neuropsychiatric disorders involving loss of cognitive ability, such as Alzheimer's disease, schizophrenia and autism. This review describes the known functions of these receptors and discusses their potential role in processes of synaptic regulation and memory formation.
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Affiliation(s)
- Shenfeng Qiu
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN 37232-0615, USA
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34
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Palmer CL, Cotton L, Henley JM. The molecular pharmacology and cell biology of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors. Pharmacol Rev 2005; 57:253-77. [PMID: 15914469 PMCID: PMC3314513 DOI: 10.1124/pr.57.2.7] [Citation(s) in RCA: 160] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptors (AMPARs) are of fundamental importance in the brain. They are responsible for the majority of fast excitatory synaptic transmission, and their overactivation is potently excitotoxic. Recent findings have implicated AMPARs in synapse formation and stabilization, and regulation of functional AMPARs is the principal mechanism underlying synaptic plasticity. Changes in AMPAR activity have been described in the pathology of numerous diseases, such as Alzheimer's disease, stroke, and epilepsy. Unsurprisingly, the developmental and activity-dependent changes in the functional synaptic expression of these receptors are under tight cellular regulation. The molecular and cellular mechanisms that control the postsynaptic insertion, arrangement, and lifetime of surface-expressed AMPARs are the subject of intense and widespread investigation. For example, there has been an explosion of information about proteins that interact with AMPAR subunits, and these interactors are beginning to provide real insight into the molecular and cellular mechanisms underlying the cell biology of AMPARs. As a result, there has been considerable progress in this field, and the aim of this review is to provide an account of the current state of knowledge.
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Affiliation(s)
- Claire L Palmer
- Medical Research Council Centre for Synaptic Plasticity, Department of Anatomy, School of Medical Sciences, Bristol University, Bristol, UK
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35
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Steckler T, Lavreysen H, Oliveira AM, Aerts N, Van Craenendonck H, Prickaerts J, Megens A, Lesage ASJ. Effects of mGlu1 receptor blockade on anxiety-related behaviour in the rat lick suppression test. Psychopharmacology (Berl) 2005; 179:198-206. [PMID: 15821950 DOI: 10.1007/s00213-004-2056-7] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2004] [Accepted: 09/24/2004] [Indexed: 10/26/2022]
Abstract
RATIONALE Group I metabotropic glutamate receptor antagonists, which block both the mGlu1 and mGlu5 receptors, have been shown to have anxiolytic effects in the lick suppression test in rats. OBJECTIVE The anxiolytic potential of the selective mGlu1 antagonist 3,4-dihydro-2H-pyrano[2,3]beta-quinolin-7-yl)(cis-4-methoxycyclohexyl)methanone (JNJ16259685) was investigated and compared with the mGlu5 antagonist MPEP. METHODS Anxiety-related behaviour was assessed in lick suppression and in the elevated zero maze in rats. Non-specific effects on pain threshold, water intake and locomotor activity were also measured. RESULTS Acute administration of JNJ16259685 or MPEP increased the number of licks (lowest active dose 2.5 mg/kg IP for each compound). JNJ16259685 did not increase water intake or reduce acute pain threshold, suggesting that the anxiolytic-like properties are specific. However, acute administration decreased locomotor activity. The effects of chronic administration of JNJ16259685 over 14 days (5 mg/kg bid) on lick suppression were comparable to those seen after acute administration, arguing against development of behavioural tolerance or sensitisation. Yet, there was a tendency for an increase in locomotor activity after cessation of chronic treatment. Acute co-administration of both JNJ16259685 and MPEP had additive effects on the number of licks. No anxiolytic-like properties of JNJ16259685 were observed in the elevated zero maze. CONCLUSION Our data suggest that the anxiolytic-like effects induced by group I metabotropic glutamate receptor antagonists are mediated through both mGlu1 and mGlu5 receptors. Rather than producing a general anxiolytic-like effect, the effects seen following mGlu1 antagonism seem task-dependent, as prominent effects were seen in a conflict procedure, but not in a task based on spontaneous exploration.
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Affiliation(s)
- Thomas Steckler
- Johnson & Johnson Pharmaceutical Research and Development, Turnhoutseweg 30, 2340 Beerse, Belgium.
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36
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Hayashi T, Huganir RL. Tyrosine phosphorylation and regulation of the AMPA receptor by SRC family tyrosine kinases. J Neurosci 2005; 24:6152-60. [PMID: 15240807 PMCID: PMC6729658 DOI: 10.1523/jneurosci.0799-04.2004] [Citation(s) in RCA: 143] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Phosphorylation of AMPA receptors is a major mechanism for the regulation of receptor function and underlies several forms of synaptic plasticity in the CNS. Although serine and threonine phosphorylation of AMPA receptors has been well studied, the potential role of tyrosine phosphorylation of AMPA receptors has not been investigated. Here, we show that the GluR2 subunit of AMPA receptors is tyrosine phosphorylated in vitro and in vivo by Src family tyrosine kinases on tyrosine 876 near its C terminus. In addition, GluR agonist treatment of cultured cortical neurons increased phosphorylation of tyrosine 876. The association with GluR2-interacting molecules GRIP1/2 was decreased by tyrosine phosphorylation of GluR2, whereas PICK1 interaction was not influenced. Moreover, mutation of tyrosine 876 eliminated AMPA- and NMDA-induced internalization of the GluR2 subunit. These data indicate that tyrosine phosphorylation of tyrosine 876 on the GluR2 C terminus by Src family tyrosine kinases is important for the regulation of AMPA receptor function and may be important for synaptic plasticity.
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Affiliation(s)
- Takashi Hayashi
- Department of Neuroscience, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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37
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Gabellini N. Transcriptional regulation by cAMP and Ca2+ links the Na+/Ca2+ exchanger 3 to memory and sensory pathways. Mol Neurobiol 2004; 30:91-116. [PMID: 15247490 DOI: 10.1385/mn:30:1:091] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The signaling cascades triggered by neurotrophins such as BDNF and by several neurotransmitters and hormones lead to the rapid induction of gene transcription by increasing the intracellular concentration of cAMP and Ca2+. This review examines the mechanisms by which these second messengers control transcriptional initiation at CRE promoters via transcription factor CREB, as well as at DRE sites via transcriptional repressor DREAM. The regulation of the SLC8A3 gene encoding the Na+/Ca2+ exchanger 3 (NCX3) is taken as an example to illustrate both mechanisms since it includes a CRE site in the promoter and several DRE sites in the exon 1 sequence. The upregulation of the NCX3 by Ca2+ signals may be specifically required to establish the Ca2+ balance that regulates several physiological and pathological processes in neurons. The regulatory features and the expression pattern of SLC8A3 gene suggest that NCX3 activity could be crucial in neuronal functions such as memory formation and sensory processing.
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Affiliation(s)
- Nadia Gabellini
- Department of Biological Chemistry, University of Padova, Padova, Italy.
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38
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Singh MR, Pratap Rudra MP, Rao SLN, Singh SS. In vitro activation of protein kinase C by beta-N-oxalyl-L-alpha,beta-diaminopropionic acid, the Lathyrus sativus neurotoxin. Neurochem Res 2004; 29:1343-8. [PMID: 15202763 DOI: 10.1023/b:nere.0000026395.25468.57] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Beta-N-oxalyl-L-alpha,beta-diaminopropionic acid (L-ODAP) toxicity has been associated with lathyrism; a spastic paraparesis caused by excessive dietary intake of the pulse Lathyrus sativus. We investigated the effect of Lathyrus neurotoxin L-ODAP on protein kinase C (PKC) activity under in vitro conditions. L-ODAP activated phosphorylation activity of purified chick brain PKC. Both lysine-rich (histone III-S) and arginine-rich (protamine sulfate) substrate phosphorylation was enhanced in the presence of L-ODAP. The activation is concentration dependent, and maximal activation is observed at 100 microM concentration. Protamine sulfate phosphorylation was enhanced by 47%, whereas histone III-S phosphorylation was enhanced by 50% over PS/PDBu/Ca2+ dependent activity. The nontoxic D-isomer (D-ODAP) did not affect both histone III-S and protamine sulfate phosphorylation activity. These results indicate that L-ODAP taken up by neuronal cells could also contribute to PKC activation and so be associated with toxicity.
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39
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Chen G, Greengard P, Yan Z. Potentiation of NMDA receptor currents by dopamine D1 receptors in prefrontal cortex. Proc Natl Acad Sci U S A 2004; 101:2596-600. [PMID: 14983054 PMCID: PMC356995 DOI: 10.1073/pnas.0308618100] [Citation(s) in RCA: 192] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Interactions between dopamine and N-methyl-D-aspartate receptors (NMDARs) in prefrontal cortex (PFC) and other brain regions are believed to play an important role in normal mental function and neuropsychiatric disorders. In this study, we examined the regulation of NMDAR currents by the dopamine D1 receptor in PFC pyramidal neurons. Application of the D1 receptor agonist SKF81297 caused a prominent increase of the steady-state NMDA-evoked current in acutely isolated PFC pyramidal neurons. The D1 effect on NMDARs was independent of protein kinase A or protein phosphatase 1, but was abolished by incubation of neurons in Ca2+-free medium. Intracellular application of the Ca2+ chelator, calmodulin, or calmodulin inhibitors largely prevented the D1 modulation of NMDAR currents. Moreover, inhibiting PKC activity or disrupting PKC association with its anchoring protein also significantly reduced the D1 effect on NMDAR currents. This upregulation of NMDAR activity by dopamine D1 receptors and the previous finding on up-regulation of dopamine D1 receptors by NMDAR activation provide a cellular mechanism for the reciprocal interactions between D1 and NMDARs. These interactions may play an important role in modulating synaptic plasticity and thus in cognitive and emotional processes.
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Affiliation(s)
- Guojun Chen
- Department of Physiology and Biophysics, School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York, Buffalo, NY 14214, USA
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40
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Fritz KI, Ashraf QM, Zubrow AB, Mishra OP, Delivoria-Papadopoulos M. Expression and Phosphorylation of N-Methyl- D-Aspartate Receptor Subunits during Graded Hypoxia in the Cerebral Cortex of Newborn Piglets. Neonatology 2004; 85:128-37. [PMID: 14631158 DOI: 10.1159/000074969] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2003] [Accepted: 08/28/2003] [Indexed: 11/19/2022]
Abstract
The present study tests the hypothesis that during graded hypoxia, N-methyl-D-aspartate (NMDA) receptor expression and phosphorylation are altered in the cerebral cortex of newborn piglets. Studies were performed in anesthetized, ventilated piglets, 6 normoxic and 9 exposed to different lengths of decreased fractions of inspired oxygen to achieve varying biochemical levels of phosphocreatine (PCr). P(2) membrane proteins were immunoprecipitated with antiphosphoserine, antiphosphotyrosine, or antiphosphothreonine antibodies and separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Proteins were transblotted and probed with NMDA receptor subunit 1 (NR1), NR2A or NR2B antibodies. As tissue PCr levels decreased from 3.5 to 0.5 micromol/g brain during hypoxia, NR1, NR2A and NR2B protein increased by 84, 56 and 38%, respectively. Phosphorylated serine, tyrosine and threonine residues also increased during hypoxia on the three subunits. However, the increase in subunit protein exceeded the increase in phosphorylated residues for all three subunits. Therefore, the ratio of phosphorylated/dephosphorylated serine, tyrosine and threonine residues decreased with worsening hypoxia. We speculate that an alteration in the ratio of phosphorylated/dephosphorylated residues of the NMDA receptor may regulate receptor activation during hypoxia.
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Affiliation(s)
- Karen I Fritz
- Department of Pediatrics, St. Christopher's Neonatology Research Laboratory, Drexel University College of Medicine, Neonatology Research Laboratories, Medical College of Pennsylvania, Philadelphia, Pa. 19129, USA.
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41
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Zhang X, Wu J, Fang L, Willis WD. The effects of protein phosphatase inhibitors on nociceptive behavioral responses of rats following intradermal injection of capsaicin. Pain 2004; 106:443-451. [PMID: 14659528 DOI: 10.1016/j.pain.2003.09.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The functions of crucial proteins in the nervous system are modulated by kinases and phosphatases which catalyze opposing reactions of phosphorylation and dephosphorylation. During spinal cord central sensitization, serine/threonine protein phosphatase 2A (PP2A) may play an important role in determining the excitability of nociceptive neurons in the spinal cord by modulating the phosphorylation state of some critical proteins. The effects of a general inhibitor of PP2A, okadaic acid (OA), and a specific inhibitor, fostriecin, on the behavioral responses of rats following capsaicin injection were investigated in this study. Hyperalgesia was initiated by injection of capsaicin into the plantar surface of the hindpaw of rats. An intrathecal catheter was previously implanted into the subarachnoid space of the spinal cord for the administration of a variety of drugs. Rats were tested for responses to mechanical stimuli using von Frey filaments of different bending forces applied at a site outside the area of injection. Responses to heat stimuli were detected from a site near the injection area. The responses were recorded before and after injection of capsaicin with the perfusion of ACSF, OA negative control, OA or fostriecin at different time points. The results demonstrated that secondary mechanical hyperalgesia and allodynia can be induced by the intradermal injection of capsaicin. Compared to administration of ACSF or the OA negative control, infusion of the phosphatase inhibitor OA or of fostriecin into the subarachnoid space enhanced the secondary mechanical hyperalgesia and allodynia by making the intradermal capsaicin-induced hyperalgesia and allodynia last longer.
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Affiliation(s)
- Xuan Zhang
- Department of Anatomy and Neuroscience, Marine Biomedical Institute, The University of Texas Medical Branch, 301 University Blvd, Galveston, TX 77555-1069, USA
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42
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Dynamic modulation of inspiratory drive currents by protein kinase A and protein phosphatases in functionally active motoneurons. J Neurosci 2003. [PMID: 12598595 DOI: 10.1523/jneurosci.23-04-01099.2003] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Plasticity underlying adaptive, long-term changes in breathing behavior is hypothesized to be attributable to the modulation of respiratory motoneurons by intracellular second-messenger cascades. In quiescent preparations, protein kinases, including cAMP-dependent protein kinase A (PKA), potentiate glutamatergic inputs. However, the dynamic role of protein kinases or phosphatases in functionally active and behaviorally relevant preparations largely remains to be established. Rhythmic inspiratory drive to motoneurons innervating inspiratory muscles is mediated by the release of glutamate acting predominantly on AMPA receptors. In rhythmically active brainstem slices from neonatal rats, we investigated whether synaptic AMPA receptor function could be modulated by changes in intracellular PKA activity, affecting inspiratory drive in hypoglossal (XII) motoneurons. Intracellular perfusion of the catalytic subunit of PKA potentiated endogenous synaptic and (exogenously applied) AMPA-induced currents in XII motoneurons. Conversely, when a peptide inhibitor of PKA was perfused intracellularly, inspiratory drive currents were depressed. Intracellular perfusion with microcystin, a potent phosphatase 1 and 2a inhibitor, increased both endogenous and exogenous AMPA receptor-mediated currents, further supporting a role of phosphorylation in modulating motoneuronal excitability affecting behaviorally relevant synaptic inputs. These findings suggest that PKA is constitutively active in XII motoneurons in vitro. Thus, endogenous synaptic AMPA currents in XII motoneurons are influenced by phosphorylation, specifically by PKA, and dephosphorylation. The role of this modulation may be to keep the activity of motoneurons within a dynamic range that aids in responding to different physiological challenges affecting breathing, such as exercise, hypoxia, and sleep.
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Massie A, Cnops L, Jacobs S, Van Damme K, Vandenbussche E, Eysel UT, Vandesande F, Arckens L. Glutamate levels and transport in cat (Felis catus) area 17 during cortical reorganization following binocular retinal lesions. J Neurochem 2003; 84:1387-97. [PMID: 12614339 DOI: 10.1046/j.1471-4159.2003.01636.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Glutamate is known to play a crucial role in the topographic reorganization of visual cortex after the induction of binocular central retinal lesions. In this study we investigated the possible involvement of the glial high-affinity Na+/K+-dependent glutamate transporters in cortical plasticity using western blotting and intracortical microdialysis. Basal extracellular glutamate levels and the re-uptake activity for glutamate have been determined by comparing the extracellular glutamate concentration before and during the blockage of glutamate removal from the synaptic cleft with the potent transporter inhibitor l-trans-pyrrolidine-3,4-dicarboxylic acid. In cats with central retinal lesions we observed increased basal extracellular glutamate concentrations together with a decreased re-uptake activity in non-deprived, peripheral area 17, compared with the sensory-deprived, central cortex of the same animal as well as the topographically matching regions of area 17 in normal subjects. Western blotting experiments revealed a parallel decrease in the expression level of the glial glutamate transporter proteins GLT-1 and GLAST in non-deprived cortex compared with sensory-deprived cortex of lesion cats and the corresponding regions of area 17 of normal subjects. This study shows that partial sensory deprivation of the visual cortex affects the removal of glutamate from the synaptic cleft and implicates a role for glial-neuronal interactions in adult brain plasticity.
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Affiliation(s)
- Ann Massie
- Laboratory of Neuroendocrinology and Immunological Biotechnology, Katholieke Universiteit Leuven, Leuven, Belgium
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44
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Qu Y, Massie A, Van der Gucht E, Cnops L, Vandenbussche E, Eysel UT, Vandesande F, Arckens L. Retinal lesions affect extracellular glutamate levels in sensory-deprived and remote non-deprived regions of cat area 17 as revealed by in vivo microdialysis. Brain Res 2003; 962:199-206. [PMID: 12543470 DOI: 10.1016/s0006-8993(02)04047-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
This study aimed at gaining insight into the role of the excitatory neurotransmitter glutamate in topographic map reorganization in the sensory systems of adult mammals after restricted deafferentations. Hereto, in vivo microdialysis was used to sample extracellular glutamate from sensory-deprived and non-deprived visual cortex of adult awake cats 18 to 53 days after the induction of restricted binocular retinal lesions, and in topographically corresponding cortical regions of control animals. A microbore HPLC-ED method was applied for the analysis of the microdialysates. In normal subjects, the visual cortex subserving central and peripheral vision showed similar extracellular fluid glutamate concentrations. In contrast, in animals with homonymous central retinal lesions, the extracellular glutamate concentration was significantly lower in central, sensory-deprived cortex compared to peripheral, non-deprived cortex. Compared to control regions in normal subjects, glutamate decreased in the extracellular fluid of deprived cortex but increased significantly in remote non-deprived visual cortex. These results not only suggest an activity-dependent regulation of the glutamate levels in visual cortex but also imply a role for perilesional cortical regions in topographic map reorganization following sensory deafferentation.
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Affiliation(s)
- Ying Qu
- Laboratory of Neuroendocrinology and Immunological Biotechnology, Katholieke Universiteit Leuven, Naamsestraat 59, B-3000 Leuven, Belgium.
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Lee FJS, Xue S, Pei L, Vukusic B, Chéry N, Wang Y, Wang YT, Niznik HB, Yu XM, Liu F. Dual regulation of NMDA receptor functions by direct protein-protein interactions with the dopamine D1 receptor. Cell 2002; 111:219-30. [PMID: 12408866 DOI: 10.1016/s0092-8674(02)00962-5] [Citation(s) in RCA: 396] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Dopamine D1-like receptors, composed of D1 and D5 receptors, have been documented to modulate glutamate-mediated fast excitatory synaptic neurotransmission. Here, we report that dopamine D1 receptors modulate NMDA glutamate receptor-mediated functions through direct protein-protein interactions. Two regions in the D1 receptor carboxyl tail can directly and selectively couple to NMDA glutamate receptor subunits NR1-1a and NR2A. While one interaction is involved in the inhibition of NMDA receptor-gated currents, the other is implicated in the attenuation of NMDA receptor-mediated excitotoxicity through a PI-3 kinase-dependent pathway.
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Affiliation(s)
- Frank J S Lee
- Department of Neuroscience, Centre for Addiction and Mental Health, Clarke Division, University of Toronto, Toronto, M5T 1R8, Ontario, Canada
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Cai X, Gu Z, Zhong P, Ren Y, Yan Z. Serotonin 5-HT1A receptors regulate AMPA receptor channels through inhibiting Ca2+/calmodulin-dependent kinase II in prefrontal cortical pyramidal neurons. J Biol Chem 2002; 277:36553-62. [PMID: 12149253 DOI: 10.1074/jbc.m203752200] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have studied the regulation of AMPA (alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid) receptor channels by serotonin signaling in pyramidal neurons of prefrontal cortex (PFC). Application of serotonin reduced the amplitude of AMPA-evoked currents, an effect mimicked by 5-HT(1A) receptor agonists and blocked by 5-HT(1A) antagonists, indicating the mediation by 5-HT(1A) receptors. The serotonergic modulation of AMPA receptor currents was blocked by protein kinase A (PKA) activators and occluded by PKA inhibitors. Inhibiting the catalytic activity of protein phosphatase 1 (PP1) also eliminated the effect of serotonin on AMPA currents. Furthermore, the serotonergic modulation of AMPA currents was occluded by application of the Ca(2+)/calmodulin-dependent kinase II (CaMKII) inhibitors and blocked by intracellular injection of calmodulin or recombinant CaMKII. Application of serotonin or 5-HT(1A) agonists to PFC slices reduced CaMKII activity and the phosphorylation of AMPA receptor subunit GluR1 at the CaMKII site in a PP1-dependent manner. We concluded that serotonin, by activating 5-HT(1A) receptors, suppress glutamatergic signaling through the inhibition of CaMKII, which is achieved by the inhibition of PKA and ensuing activation of PP1. This modulation demonstrates the critical role of CaMKII in serotonergic regulation of PFC neuronal activity, which may explain the neuropsychiatric behavioral phenotypes seen in CaMKII knockout mice.
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Affiliation(s)
- Xiang Cai
- Department of Physiology and Biophysics, School of Medicine and Biomedical Sciences, State University of New York, Buffalo, New York 14214, USA
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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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Distance-dependent increase in AMPA receptor number in the dendrites of adult hippocampal CA1 pyramidal neurons. J Neurosci 2002. [PMID: 11717348 DOI: 10.1523/jneurosci.21-23-09151.2001] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The Schaffer collateral pathway provides hippocampal CA1 pyramidal cells with a fairly homogeneous excitatory synaptic input that is spread out across several hundred micrometers of their apical dendritic arborizations. A progressive increase in synaptic conductance, with distance from the soma, has been reported to reduce the location dependence that should result from this arrangement. The excitatory synaptic contacts within this pathway primarily use AMPA- and NMDA-type glutamate receptors. To investigate the underlying mechanism of the increased distal excitatory postsynaptic conductance, we used outside-out patches and a fast application system to characterize the properties and distribution of synaptic glutamate receptors across the range of apical dendrites receiving Schaffer collateral input. We observed an approximately twofold increase in AMPA-mediated current amplitude (0.3-0.6 nA) in the range of CA1 apical dendrites that receive a uniform density of Schaffer collateral input (approximately 100-250 micrometer from soma). NMDA-mediated current amplitude, however, remained unchanged. We analyzed the current kinetics, agonist affinity, single-channel conductance, maximum open probability, and reversal potential of AMPA receptors and did not find any differences. Instead, the number of AMPA receptors present in our patches increased approximately twofold. These data suggest that an increase in the number of AMPA receptors present at distal synapses may play an important role in the distance-dependent scaling of Schaffer collateral synapses.
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Abstract
Regulation of protein phosphatase 2A (PP2A) activity and NMDA receptor (NMDAR) phosphorylation state contribute to the modulation of synaptic plasticity, yet these two mechanisms have not been functionally linked. The NMDAR subunit NR3A is equipped with a unique carboxyl domain that is different from other NMDAR subunits. We hypothesized that the NR3A C-terminal intracellular domain might serve as synaptic anchor for the phosphatase in the developing CNS. A cDNA library was screened by the yeast two-hybrid method using the NR3A carboxyl domain as the bait. The catalytic subunit of the serine-threonine PP2A was found to be associated with the NR3A carboxyl domain. Immunoprecipitation studies indicated that the NR3A subunit formed a stable complex with PP2A in the rat brain in vivo. Association of PP2A with NMDARs led to an increase in the phosphatase activity of PP2A and the dephosphorylation of serine 897 of the NMDAR subunit NR1. Stimulation of NMDARs led to the dissociation of PP2A from the complex and the reduction of PP2A activity. A peptide corresponding to the PP2A-NR3A binding domain functioned as a negative regulator of PP2A activity. These data suggest that NMDARs are allosteric modulators of PP2A, which in turn controls their phosphorylation state. The data delineate a mechanistic model of the dynamic regulation of a PP2A-NMDAR signaling complex, mediated by the interaction of NR3A and PP2A, and suggest a novel NMDAR-mediated signaling mechanism in addition to the traditional ionotropic functions of NMDARs.
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Grossman SD, Rosenberg LJ, Wrathall JR. Relationship of altered glutamate receptor subunit mRNA expression to acute cell loss after spinal cord contusion. Exp Neurol 2001; 168:283-9. [PMID: 11259116 DOI: 10.1006/exnr.2001.7629] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Alterations in the expression of ionotropic glutamate receptors (GluR) contribute to neuronal loss after brain ischemia and epilepsy. In order to determine whether altered expression of GluR subunits might contribute to cell loss after spinal cord injury (SCI), we performed a time course study of subunit mRNA expression using quantitative in situ hybridization. Expression was studied in ventral horn motor neurons (VMN) and glia in adjacent ventral white matter at 15 min and 4, 8, and 24 h after SCI in tissue sections 4 mm rostral and caudal to the injury epicenter. We found that the AMPA subunit GluR2 was significantly down-regulated in VMN at 24 h, but not at the earlier times examined, although half the loss of VMN in these locations occurs by 8 h after injury. No changes in the normal expression of GluR2 or GluR4 were found in white matter where glial loss occurs after SCI. NMDA subunits NR1 and NR2A were significantly and rapidly up-regulated in VMN after SCI, but only caudal to the lesion site, while VMN loss is similar rostral and caudal to the epicenter. Thus, the temporal pattern of AMPA and the spatial pattern of NMDA subunit expression changes were distinct from the pattern of VMN loss after SCI. We conclude that altered GluR subunit expression after SCI is unlikely to be involved in secondary cell loss and instead may be involved with plasticity and reorganization of the injured spinal cord.
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Affiliation(s)
- S D Grossman
- Department of Cell Biology, Georgetown University Medical Center, 3970 Reservoir Road, Washington, DC 20007, USA
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