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Mele M, De Luca P, Santos AR, Vieira M, Salazar IL, Pinheiro PS, Duarte CB. GRASP1 ubiquitination regulates AMPA receptor surface expression and synaptic activity in cultured hippocampal neurons. FASEB J 2021; 35:e21763. [PMID: 34245609 DOI: 10.1096/fj.201903061rr] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 05/29/2021] [Accepted: 06/14/2021] [Indexed: 11/11/2022]
Abstract
The synaptic expression of glutamate receptors of the α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) type is dynamically controlled by interaction with binding partners and auxiliary proteins. These proteins can be regulated by posttranslational modifications, including ubiquitination. In this work, we investigated the regulation of glutamate receptor interacting protein-associated protein 1 (GRASP1) by ubiquitin-dependent mechanisms and its impact on surface expression and activity of synaptic AMPA receptors. Cotransfection of GFP-ubiquitin decreased myc-GRASP1 protein levels in HEK293T cells, and this effect was inhibited upon transfection of an ubiquitin mutant that cannot be ubiquitinated on Lys48. In addition, transfection of cultured hippocampal neurons with GFP-ubiquitin reduced the dendritic levels of endogenous GRASP1 and decreased the surface expression of GluA1 AMPA receptor subunits, an effect that was partly reversed by cotransfection with GRASP1. Similarly, transfection of hippocampal neurons with GFP-ubiquitin decreased the amplitude of miniature excitatory postsynaptic currents (mEPSCs) mediated by Ca2+ -impermeable AMPA receptors, and this effect was abrogated by cotransfection of GRASP1. Together, the results show a role for ubiquitination in the regulation of the postsynaptic protein GRASP1, which has an impact on the surface distribution of AMPA receptors and on their activity at the synapse.
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Affiliation(s)
- Miranda Mele
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,Institute for Interdisciplinary Research, University of Coimbra, Coimbra, Portugal
| | - Pasqualino De Luca
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,Institute for Interdisciplinary Research, University of Coimbra, Coimbra, Portugal
| | - Ana Rita Santos
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal
| | - Marta Vieira
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal
| | - Ivan L Salazar
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,Institute for Interdisciplinary Research, University of Coimbra, Coimbra, Portugal
| | - Paulo S Pinheiro
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,Institute for Interdisciplinary Research, University of Coimbra, Coimbra, Portugal
| | - Carlos B Duarte
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,Department of Life Sciences, University of Coimbra, Coimbra, Portugal
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Mele M, Vieira R, Correia B, De Luca P, Duarte FV, Pinheiro PS, Duarte CB. Transient incubation of cultured hippocampal neurons in the absence of magnesium induces rhythmic and synchronized epileptiform-like activity. Sci Rep 2021; 11:11374. [PMID: 34059735 PMCID: PMC8167095 DOI: 10.1038/s41598-021-90486-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Accepted: 04/29/2021] [Indexed: 11/09/2022] Open
Abstract
Cell culture models are important tools to study epileptogenesis mechanisms. The aim of this work was to characterize the spontaneous and synchronized rhythmic activity developed by cultured hippocampal neurons after transient incubation in zero Mg2+ to model Status Epilepticus. Cultured hippocampal neurons were transiently incubated with a Mg2+-free solution and the activity of neuronal networks was evaluated using single cell calcium imaging and whole-cell current clamp recordings. Here we report the development of synchronized and spontaneous [Ca2+]i transients in cultured hippocampal neurons immediately after transient incubation in a Mg2+-free solution. Spontaneous and synchronous [Ca2+]i oscillations were observed when the cells were then incubated in the presence of Mg2+. Functional studies also showed that transient incubation in Mg2+-free medium induces neuronal rhythmic burst activity that was prevented by antagonists of glutamate receptors. In conclusion, we report the development of epileptiform-like activity, characterized by spontaneous and synchronized discharges, in cultured hippocampal neurons transiently incubated in the absence of Mg2+. This model will allow studying synaptic alterations contributing to the hyperexcitability that underlies the development of seizures and will be useful in pharmacological studies for testing new drugs for the treatment of epilepsy.
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Affiliation(s)
- Miranda Mele
- CNC-Center for Neuroscience and Cell Biology, Faculty of Medicine, University of Coimbra, Rua Larga, 3004-504, Coimbra, Portugal.,Institute for Interdisciplinary Research, Coimbra, Portugal
| | - Ricardo Vieira
- CNC-Center for Neuroscience and Cell Biology, Faculty of Medicine, University of Coimbra, Rua Larga, 3004-504, Coimbra, Portugal
| | - Bárbara Correia
- CNC-Center for Neuroscience and Cell Biology, Faculty of Medicine, University of Coimbra, Rua Larga, 3004-504, Coimbra, Portugal
| | - Pasqualino De Luca
- CNC-Center for Neuroscience and Cell Biology, Faculty of Medicine, University of Coimbra, Rua Larga, 3004-504, Coimbra, Portugal.,Institute for Interdisciplinary Research, Coimbra, Portugal
| | - Filipe V Duarte
- CNC-Center for Neuroscience and Cell Biology, Faculty of Medicine, University of Coimbra, Rua Larga, 3004-504, Coimbra, Portugal.,Institute for Interdisciplinary Research, Coimbra, Portugal
| | - Paulo S Pinheiro
- CNC-Center for Neuroscience and Cell Biology, Faculty of Medicine, University of Coimbra, Rua Larga, 3004-504, Coimbra, Portugal.,Institute for Interdisciplinary Research, Coimbra, Portugal
| | - Carlos B Duarte
- CNC-Center for Neuroscience and Cell Biology, Faculty of Medicine, University of Coimbra, Rua Larga, 3004-504, Coimbra, Portugal. .,Department of Life Sciences, University of Coimbra, Coimbra, Portugal.
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Afonso P, De Luca P, Carvalho RS, Cortes L, Pinheiro P, Oliveiros B, Almeida RD, Mele M, Duarte CB. BDNF increases synaptic NMDA receptor abundance by enhancing the local translation of Pyk2 in cultured hippocampal neurons. Sci Signal 2019; 12:12/586/eaav3577. [PMID: 31213568 DOI: 10.1126/scisignal.aav3577] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The effects of brain-derived neurotrophic factor (BDNF) in long-term synaptic potentiation (LTP) are thought to underlie learning and memory formation and are partly mediated by local protein synthesis. Here, we investigated the mechanisms that mediate BDNF-induced alterations in the synaptic proteome that are coupled to synaptic strengthening. BDNF induced the synaptic accumulation of GluN2B-containing NMDA receptors (NMDARs) and increased the amplitude of NMDAR-mediated miniature excitatory postsynaptic currents (mEPSCs) in cultured rat hippocampal neurons by a mechanism requiring activation of the protein tyrosine kinase Pyk2 and dependent on cellular protein synthesis. Single-particle tracking using quantum dot imaging revealed that the increase in the abundance of synaptic NMDAR currents correlated with their enhanced stability in the synaptic compartment. Furthermore, BDNF increased the local synthesis of Pyk2 at the synapse, and the observed increase in Pyk2 protein abundance along dendrites of cultured hippocampal neurons was mediated by a mechanism dependent on the ribonucleoprotein hnRNP K, which bound to Pyk2 mRNA and dissociated from it upon BDNF application. Knocking down hnRNP K reduced the BDNF-induced synaptic synthesis of Pyk2 protein, whereas its overexpression enhanced it. Together, these findings indicate that hnRNP K mediates the synaptic distribution of Pyk2 synthesis, and hence the synaptic incorporation of GluN2B-containing NMDARs, induced by BDNF, which may affect LTP and synaptic plasticity.
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Affiliation(s)
- Pedro Afonso
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal.,Faculty of Pharmacy, University of Coimbra, 3000-548 Coimbra, Portugal
| | - Pasqualino De Luca
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal.,Institute for Interdisciplinary Research, University of Coimbra (IIIUC), 3030-790 Coimbra, Portugal
| | - Rafael S Carvalho
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Luísa Cortes
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal.,Institute for Interdisciplinary Research, University of Coimbra (IIIUC), 3030-790 Coimbra, Portugal
| | - Paulo Pinheiro
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal.,Institute for Interdisciplinary Research, University of Coimbra (IIIUC), 3030-790 Coimbra, Portugal
| | - Barbara Oliveiros
- Laboratory of Biostatistics and Medical Informatics, Faculty of Medicine, University of Coimbra, 3000-548 Coimbra, Portugal.,Coimbra Institute for Clinical and Biomedical Research (iCBR), Faculty of Medicine, University of Coimbra, 3000-548 Coimbra, Portugal
| | - Ramiro D Almeida
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal.,Health Sciences Program, Department of Medical Sciences, Institute of Biomedicine - iBiMED, University of Aveiro, 3810-193 Aveiro, Portugal
| | - Miranda Mele
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal.,Institute for Interdisciplinary Research, University of Coimbra (IIIUC), 3030-790 Coimbra, Portugal
| | - Carlos B Duarte
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal. .,Department of Life Sciences, University of Coimbra, 3000-456 Coimbra, Portugal
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