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Coombs ID, Cull-Candy SG. Single-channel mechanisms underlying the function, diversity and plasticity of AMPA receptors. Neuropharmacology 2021; 198:108781. [PMID: 34480912 DOI: 10.1016/j.neuropharm.2021.108781] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2021] [Revised: 08/18/2021] [Accepted: 08/31/2021] [Indexed: 12/29/2022]
Abstract
The functional properties of AMPA receptors shape many of the essential features of excitatory synaptic signalling in the brain, including high-fidelity point-to-point transmission and long-term plasticity. Understanding the behaviour and regulation of single AMPAR channels is fundamental in unravelling how central synapses carry, process and store information. There is now an abundance of data on the importance of alternative splicing, RNA editing, and phosphorylation of AMPAR subunits in determining central synaptic diversity. Furthermore, auxiliary subunits have emerged as pivotal players that regulate AMPAR channel properties and add further diversity. Single-channel studies have helped reveal a fascinating picture of the unique behaviour of AMPAR channels - their concentration-dependent single-channel conductance, the basis of their multiple-conductance states, and the influence of auxiliary proteins in controlling many of their gating and conductance properties. Here we summarize basic hallmarks of AMPAR single-channels, in relation to function, diversity and plasticity. We also present data that reveal an unexpected feature of AMPAR sublevel behaviour. This article is part of the special Issue on 'Glutamate Receptors - AMPA receptors'.
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Affiliation(s)
- Ian D Coombs
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.
| | - Stuart G Cull-Candy
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.
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2
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Alhowail AH, Pinky PD, Eggert M, Bloemer J, Woodie LN, Buabeid MA, Bhattacharya S, Jasper SL, Bhattacharya D, Dhanasekaran M, Escobar M, Arnold RD, Suppiramaniam V. Doxorubicin induces dysregulation of AMPA receptor and impairs hippocampal synaptic plasticity leading to learning and memory deficits. Heliyon 2021; 7:e07456. [PMID: 34296005 PMCID: PMC8282984 DOI: 10.1016/j.heliyon.2021.e07456] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 06/10/2021] [Accepted: 06/28/2021] [Indexed: 11/27/2022] Open
Abstract
Doxorubicin (Dox) is a chemotherapeutic agent used widely to treat a variety of malignant cancers. However, Dox chemotherapy is associated with several adverse effects, including "chemobrain," the observation that cancer patients exhibit through learning and memory difficulties extending even beyond treatment. This study investigated the effect of Dox treatment on learning and memory as well as hippocampal synaptic plasticity. Dox-treated mice (5 mg/kg weekly x 5) demonstrated impaired performance in the Y-maze spatial memory task and a significant reduction in hippocampal long-term potentiation. The deficit in synaptic plasticity was mirrored by deficits in the functionality of synaptic `α-amino-3- hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) channels, including reduced probability of opening, decreased dwell open time, and increased closed times. Furthermore, a reduction in the AMPAR subunit GluA1 level, its downstream signaling molecule Ca2+/calmodulin-dependent protein kinase (CaMKII), and brain-derived neurotrophic factor (BDNF) were observed. This was also accompanied by an increase in extracellular signal regulated kinase (ERK) and protein kinase B (AKT) activation. Together these data suggest that Dox-induced cognitive impairments are at least partially due to alterations in the expression and functionality of the glutamatergic AMPAR system.
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Affiliation(s)
- Ahmad H. Alhowail
- Department of Pharmacology and Toxicology, Qassim University, Buraydah, Saudi Arabia
| | - Priyanka D. Pinky
- Department of Drug Discovery and Development, Auburn University, Auburn, Alabama, USA
| | - Matthew Eggert
- Department of Drug Discovery and Development, Auburn University, Auburn, Alabama, USA
| | - Jenna Bloemer
- Department of Drug Discovery and Development, Auburn University, Auburn, Alabama, USA
- Department of Pharmaceutical and Biomedical Sciences, Touro College of Pharmacy, New York, NY, USA
| | - Lauren N. Woodie
- Department of Nutrition, Dietetics and Hospitality Management, College of Human Sciences, Auburn University, Auburn, Alabama, USA
- Institute for Diabetes, Obesity and Metabolism, Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Manal A. Buabeid
- College of Pharmacy and Health Sciences, Ajman University, Ajman, United Arab Emirates
| | - Subhrajit Bhattacharya
- Department of Drug Discovery and Development, Auburn University, Auburn, Alabama, USA
- Center for Neuroscience Initiative, Auburn University, Auburn, AL, USA
| | - Shanese L. Jasper
- Department of Drug Discovery and Development, Auburn University, Auburn, Alabama, USA
| | | | - Muralikrishnan Dhanasekaran
- Department of Drug Discovery and Development, Auburn University, Auburn, Alabama, USA
- Center for Neuroscience Initiative, Auburn University, Auburn, AL, USA
| | - Martha Escobar
- Department of Psychology, Oakland University, Rochester, MI, USA
| | - Robert D. Arnold
- Department of Drug Discovery and Development, Auburn University, Auburn, Alabama, USA
- Center for Neuroscience Initiative, Auburn University, Auburn, AL, USA
| | - Vishnu Suppiramaniam
- Department of Drug Discovery and Development, Auburn University, Auburn, Alabama, USA
- Center for Neuroscience Initiative, Auburn University, Auburn, AL, USA
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3
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Summers KC, Bogard AS, Tavalin SJ. Preferential generation of Ca 2+-permeable AMPA receptors by AKAP79-anchored protein kinase C proceeds via GluA1 subunit phosphorylation at Ser-831. J Biol Chem 2019; 294:5521-5535. [PMID: 30737285 DOI: 10.1074/jbc.ra118.004340] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Revised: 02/06/2019] [Indexed: 01/01/2023] Open
Abstract
AMPA-type glutamate receptors (AMPARs) mediate fast excitatory neurotransmission in the mammalian central nervous system. Preferential AMPAR subunit assembly favors heteromeric GluA1/GluA2 complexes. The presence of the GluA2 subunit generates Ca2+-impermeable (CI) AMPARs that have linear current-voltage (I-V) relationships. However, diverse forms of synaptic plasticity and pathophysiological conditions are associated with shifts from CI to inwardly rectifying, GluA2-lacking, Ca2+-permeable (CP) AMPARs on time scales ranging from minutes to days. These shifts have been linked to GluA1 phosphorylation at Ser-845, a protein kinase A (PKA)-targeted site within its intracellular C-terminal tail, often in conjunction with protein kinase A anchoring protein 79 (AKAP79; AKAP150 in rodents), which targets PKA to GluA1. However, AKAP79 may impact GluA1 phosphorylation at other sites by interacting with other signaling enzymes. Here, we evaluated the ability of AKAP79, its signaling components, and GluA1 phosphorylation sites to induce CP-AMPARs under conditions in which CI-AMPARs normally predominate. We found that GluA1 phosphorylation at Ser-831 is sufficient for the appearance of CP-AMPARs and that AKAP79-anchored protein kinase C (PKC) primarily drives the appearance of these receptors via this site. In contrast, other AKAP79-signaling components and C-terminal tail GluA1 phosphorylation sites exhibited a permissive role, limiting the extent to which AKAP79 promotes CP-AMPARs. This may reflect the need for these sites to undergo active phosphorylation/dephosphorylation cycles that control their residency within distinct subcellular compartments. These findings suggest that AKAP79, by orchestrating phosphorylation, represents a key to a GluA1 phosphorylation passcode, which allows the GluA1 subunit to escape GluA2 dominance and promote the appearance of CP-AMPARs.
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Affiliation(s)
- Kyle C Summers
- From the Department of Pharmacology, University of Tennessee Health Science Center, Memphis, Tennessee 38103
| | - Amy S Bogard
- From the Department of Pharmacology, University of Tennessee Health Science Center, Memphis, Tennessee 38103
| | - Steven J Tavalin
- From the Department of Pharmacology, University of Tennessee Health Science Center, Memphis, Tennessee 38103
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4
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Phosphorylation of the AMPAR-TARP Complex in Synaptic Plasticity. Proteomes 2018; 6:proteomes6040040. [PMID: 30297624 PMCID: PMC6313930 DOI: 10.3390/proteomes6040040] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Revised: 10/04/2018] [Accepted: 10/06/2018] [Indexed: 11/17/2022] Open
Abstract
Synaptic plasticity has been considered a key mechanism underlying many brain functions including learning, memory, and drug addiction. An increase or decrease in synaptic activity of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) complex mediates the phenomena as shown in the cellular models of synaptic plasticity, long-term potentiation (LTP), and depression (LTD). In particular, protein phosphorylation shares the spotlight in expressing the synaptic plasticity. This review summarizes the studies on phosphorylation of the AMPAR pore-forming subunits and auxiliary proteins including transmembrane AMPA receptor regulatory proteins (TARPs) and discusses its role in synaptic plasticity.
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Nguyen PV, Gelinas JN. Noradrenergic gating of long-lasting synaptic potentiation in the hippocampus: from neurobiology to translational biomedicine. J Neurogenet 2018; 32:171-182. [DOI: 10.1080/01677063.2018.1497630] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Peter V. Nguyen
- Department of Physiology and Institute of Neuroscience & Mental Health, University of Alberta School of Medicine, Edmonton, Canada
| | - Jennifer N. Gelinas
- Department of Neurology and Institute for Genomic Medicine, College of Physicians & Surgeons of Columbia University, New York, NY,USA
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Jȩdrzejewska-Szmek J, Luczak V, Abel T, Blackwell KT. β-adrenergic signaling broadly contributes to LTP induction. PLoS Comput Biol 2017; 13:e1005657. [PMID: 28742159 PMCID: PMC5546712 DOI: 10.1371/journal.pcbi.1005657] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Revised: 08/07/2017] [Accepted: 06/27/2017] [Indexed: 12/18/2022] Open
Abstract
Long-lasting forms of long-term potentiation (LTP) represent one of the major cellular mechanisms underlying learning and memory. One of the fundamental questions in the field of LTP is why different molecules are critical for long-lasting forms of LTP induced by diverse experimental protocols. Further complexity stems from spatial aspects of signaling networks, such that some molecules function in the dendrite and some are critical in the spine. We investigated whether the diverse experimental evidence can be unified by creating a spatial, mechanistic model of multiple signaling pathways in hippocampal CA1 neurons. Our results show that the combination of activity of several key kinases can predict the occurrence of long-lasting forms of LTP for multiple experimental protocols. Specifically Ca2+/calmodulin activated kinase II, protein kinase A and exchange protein activated by cAMP (Epac) together predict the occurrence of LTP in response to strong stimulation (multiple trains of 100 Hz) or weak stimulation augmented by isoproterenol. Furthermore, our analysis suggests that activation of the β-adrenergic receptor either via canonical (Gs-coupled) or non-canonical (Gi-coupled) pathways underpins most forms of long-lasting LTP. Simulations make the experimentally testable prediction that a complete antagonist of the β-adrenergic receptor will likely block long-lasting LTP in response to strong stimulation. Collectively these results suggest that converging molecular mechanisms allow CA1 neurons to flexibly utilize signaling mechanisms best tuned to temporal pattern of synaptic input to achieve long-lasting LTP and memory storage. Long-term potentiation of the strength of synaptic connections is a mechanism of learning and memory storage. One of the most confusing aspects of hippocampal synaptic potentiation is that numerous experiments have revealed the requirement for a plethora of signaling molecules. Furthermore the degree to which molecules activated by the stress response modify hippocampal synaptic potentiation and memory is still unclear. We used a computational model to demonstrate that this molecular diversity can be explained by considering a combination of several key molecules. We also show that activation of β-adrenergic receptors by the stress response appears to be involved in most forms of synaptic potentiation, though in some cases unconventional mechanisms are utilized. This suggests that novel treatments for stress-related disorders may have more success if they target unconventional mechanisms activated by β-adrenergic receptors.
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Affiliation(s)
- Joanna Jȩdrzejewska-Szmek
- The Krasnow Institute for Advanced Studies, George Mason University, Fairfax, Virginia, United States of America
| | - Vincent Luczak
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Ted Abel
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Kim T Blackwell
- The Krasnow Institute for Advanced Studies, George Mason University, Fairfax, Virginia, United States of America
- * E-mail:
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Sathler MF, Stutz B, Martins RS, Dos Santos Pereira M, Pecinalli NR, Santos LE, Taveira-da-Silva R, Lowe J, de Freitas IG, de Melo Reis RA, Manhães AC, Kubrusly RCC. Single exposure to cocaine impairs aspartate uptake in the pre-frontal cortex via dopamine D1-receptor dependent mechanisms. Neuroscience 2016; 329:326-36. [PMID: 27208619 DOI: 10.1016/j.neuroscience.2016.05.022] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Revised: 05/10/2016] [Accepted: 05/12/2016] [Indexed: 11/16/2022]
Abstract
Dopamine and glutamate play critical roles in the reinforcing effects of cocaine. We demonstrated that a single intraperitoneal administration of cocaine induces a significant decrease in [(3)H]-d-aspartate uptake in the pre-frontal cortex (PFC). This decrease is associated with elevated dopamine levels, and requires dopamine D1-receptor signaling (D1R) and adenylyl cyclase activation. The effect was observed within 10min of cocaine administration and lasted for up to 30min. This rapid response is related to D1R-mediated cAMP-mediated activation of PKA and phosphorylation of the excitatory amino acid transporters EAAT1, EAAT2 and EAAT3. We also demonstrated that cocaine exposure increases extracellular d-aspartate, l-glutamate and d-serine in the PFC. Our data suggest that cocaine activates dopamine D1 receptor signaling and PKA pathway to regulate EAATs function and extracellular EAA level in the PFC.
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Affiliation(s)
- Matheus Figueiredo Sathler
- Laboratório de Neurofarmacologia, Departamento de Fisiologia e Farmacologia, Universidade Federal Fluminense, Niterói, Brazil.
| | - Bernardo Stutz
- Laboratório de Neuroquímica, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil.
| | - Robertta Silva Martins
- Laboratório de Neurofarmacologia, Departamento de Fisiologia e Farmacologia, Universidade Federal Fluminense, Niterói, Brazil.
| | - Maurício Dos Santos Pereira
- Laboratório de Neurofarmacologia, Departamento de Fisiologia e Farmacologia, Universidade Federal Fluminense, Niterói, Brazil; Laboratório de Neurofisiologia Molecular, Departamento de Fisiologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil.
| | - Ney Roner Pecinalli
- Laboratório de Neurofarmacologia, Departamento de Fisiologia e Farmacologia, Universidade Federal Fluminense, Niterói, Brazil.
| | - Luis E Santos
- Laboratório de Neuroquímica, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil.
| | - Rosilane Taveira-da-Silva
- Laboratório de Fisico-Química Biológica Aída Hassón-Voloch Instituto de Biofísica Carlos Chagas Filho Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
| | - Jennifer Lowe
- Laboratório de Fisico-Química Biológica Aída Hassón-Voloch Instituto de Biofísica Carlos Chagas Filho Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
| | - Isis Grigorio de Freitas
- Laboratório de Neurofarmacologia, Departamento de Fisiologia e Farmacologia, Universidade Federal Fluminense, Niterói, Brazil.
| | - Ricardo Augusto de Melo Reis
- Laboratório de Neuroquímica, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil.
| | - Alex C Manhães
- Laboratório de Neurofisiologia, Departamento de Ciências Fisiológicas, Instituto de Biologia Roberto Alcantara Gomes, Centro Biomédico, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
| | - Regina C C Kubrusly
- Laboratório de Neurofarmacologia, Departamento de Fisiologia e Farmacologia, Universidade Federal Fluminense, Niterói, Brazil.
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8
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Babiec WE, Guglietta R, O'Dell TJ. Basal levels of AMPA receptor GluA1 subunit phosphorylation at threonine 840 and serine 845 in hippocampal neurons. ACTA ACUST UNITED AC 2016; 23:127-33. [PMID: 26980779 PMCID: PMC4793196 DOI: 10.1101/lm.040675.115] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Accepted: 01/12/2016] [Indexed: 01/19/2023]
Abstract
Dephosphorylation of AMPA receptor (AMPAR) GluA1 subunits at two sites, serine 845 (S845) and threonine 840 (T840), is thought to be involved in NMDA receptor-dependent forms of long-term depression (LTD). Importantly, the notion that dephosphorylation of these sites contributes to LTD assumes that a significant fraction of GluA1 subunits are basally phosphorylated at these sites. To examine this question, we used immunoprecipitation/depletion assays to estimate the proportion of GluA1 subunits basally phosphorylated at S845 and T840. Although dephosphorylation of S845 is thought to have a key role in LTD, our results indicate that few GluA1 subunits in hippocampal neurons are phosphorylated at this site. In contrast, ∼50% of GluA1 subunits are basally phosphorylated at T840, suggesting that dephosphorylation of this site can contribute to the down-regulation of AMPAR-mediated synaptic transmission in LTD.
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Affiliation(s)
- Walter E Babiec
- Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095, USA
| | - Ryan Guglietta
- Interdepartmental Ph.D. Program for Neuroscience at UCLA, Los Angeles, California 90095, USA
| | - Thomas J O'Dell
- Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095, USA UCLA Integrative Center for Learning and Memory, Brain Research Institute, Los Angeles, California 90095, USA
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Caudal D, Rame M, Jay TM, Godsil BP. Dynamic Regulation of AMPAR Phosphorylation In Vivo Following Acute Behavioral Stress. Cell Mol Neurobiol 2016; 36:1331-1342. [PMID: 26814839 DOI: 10.1007/s10571-016-0332-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Accepted: 07/31/2015] [Indexed: 12/20/2022]
Abstract
The tuning of glutamatergic transmission is an essential mechanism for neuronal communication. α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) are ionotropic glutamate receptors that mediate fast synaptic transmission. The phosphorylation states of specific serine residues on the GluA1 and GluA2 AMPAR subunits are considered critical post-translational modifications that regulate AMPAR activity and subcellular trafficking. While behavioral stress, via stress hormones, exerts specific alterations on such glutamatergic processes, there have been conflicting data concerning the influence of stress on AMPAR phosphorylation in different brain regions, and the post-stress signaling mechanisms mediating these processes are not well delineated. Here, we examined the dynamics of phosphorylation at three AMPAR serine residues (ser831-GluA1, ser845-GluA1, and ser880-GluA2) in four brain regions [amygdala, medial prefrontal cortex (mPFC), dorsal hippocampus, and ventral hippocampus] of the rat during the hour following behavioral stress. We also tested the impact of post-stress corticosteroid receptor blockade on AMPAR phosphorylation. Both GluA1 subunit residues exhibited elevated phosphorylation after stress, yet post-stress administration of corticosteroid receptor antagonists curtailed these effects only at ser831-GluA1. In contrast, ser880-GluA2 displayed a time-dependent tendency for early decreased phosphorylation (that was selectively augmented by mifepristone treatment in the amygdala and mPFC of stressed animals) followed by increased phosphorylation later on. These findings show that the in vivo regulation of AMPAR phosphorylation after stress is a dynamic and subunit-specific process, and they provide support for the hypothesis that corticosteroid receptors have an ongoing role in the regulation of ser831-GluA1 phosphorylation during the post-stress interval.
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Affiliation(s)
- Dorian Caudal
- Physiopathologie des Maladies Psychiatriques, UMR_S 894 Inserm, Centre de Psychiatrie et Neurosciences, 2ter rue d'Alesia, 75014, Paris, France.,Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Marion Rame
- Physiopathologie des Maladies Psychiatriques, UMR_S 894 Inserm, Centre de Psychiatrie et Neurosciences, 2ter rue d'Alesia, 75014, Paris, France
| | - Thérèse M Jay
- Physiopathologie des Maladies Psychiatriques, UMR_S 894 Inserm, Centre de Psychiatrie et Neurosciences, 2ter rue d'Alesia, 75014, Paris, France.,Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Bill P Godsil
- Physiopathologie des Maladies Psychiatriques, UMR_S 894 Inserm, Centre de Psychiatrie et Neurosciences, 2ter rue d'Alesia, 75014, Paris, France. .,Université Paris Descartes, Sorbonne Paris Cité, Paris, France.
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10
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O'Dell TJ, Connor SA, Guglietta R, Nguyen PV. β-Adrenergic receptor signaling and modulation of long-term potentiation in the mammalian hippocampus. ACTA ACUST UNITED AC 2015; 22:461-71. [PMID: 26286656 PMCID: PMC4561407 DOI: 10.1101/lm.031088.113] [Citation(s) in RCA: 96] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 06/02/2015] [Indexed: 02/06/2023]
Abstract
Encoding new information in the brain requires changes in synaptic strength. Neuromodulatory transmitters can facilitate synaptic plasticity by modifying the actions and expression of specific signaling cascades, transmitter receptors and their associated signaling complexes, genes, and effector proteins. One critical neuromodulator in the mammalian brain is norepinephrine (NE), which regulates multiple brain functions such as attention, perception, arousal, sleep, learning, and memory. The mammalian hippocampus receives noradrenergic innervation and hippocampal neurons express β-adrenergic receptors, which are known to play important roles in gating the induction of long-lasting forms of synaptic potentiation. These forms of long-term potentiation (LTP) are believed to importantly contribute to long-term storage of spatial and contextual memories in the brain. In this review, we highlight the contributions of noradrenergic signaling in general and β-adrenergic receptors in particular, toward modulating hippocampal LTP. We focus on the roles of NE and β-adrenergic receptors in altering the efficacies of specific signaling molecules such as NMDA and AMPA receptors, protein phosphatases, and translation initiation factors. Also, the roles of β-adrenergic receptors in regulating synaptic "tagging" and "capture" of LTP within synaptic networks of the hippocampus are reviewed. Understanding the molecular and cellular bases of noradrenergic signaling will enrich our grasp of how the brain makes new, enduring memories, and may shed light on credible strategies for improving mental health through treatment of specific disorders linked to perturbed memory processing and dysfunctional noradrenergic synaptic transmission.
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Affiliation(s)
- Thomas J O'Dell
- Department of Physiology, David Geffen School of Medicine and Integrative Center for Learning and Memory, Brain Research Institute, University of California, Los Angeles, Los Angeles, California 90095, USA
| | - Steven A Connor
- Department of Physiology, University of Alberta School of Medicine, Edmonton, Alberta T6G 2H7, Canada
| | - Ryan Guglietta
- Interdepartmental Ph.D. Program for Neuroscience, University of California, Los Angeles, Los Angeles, California 90095, USA
| | - Peter V Nguyen
- Department of Physiology, University of Alberta School of Medicine, Edmonton, Alberta T6G 2H7, Canada Department of Psychiatry, University of Alberta School of Medicine, Edmonton, Alberta T6G 2H7, Canada Department of Neuroscience & Mental Health Institute, University of Alberta School of Medicine, Edmonton, Alberta T6G 2H7, Canada
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11
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Abstract
Dynamic changes in synaptic strength are thought to be critical for higher brain function such as learning and memory. Alterations in synaptic strength can result from modulation of AMPA receptor (AMPAR) function and trafficking to synaptic sites. The phosphorylation state of AMPAR subunits is one mechanism by which cells regulate receptor function and trafficking. Receptor phosphorylation is in turn regulated by extracellular signals; these include neuronal activity, neuropeptides, and neuromodulators such as dopamine and norepinephrine (NE). Although numerous studies have reported that the neuropeptide pituitary adenylate cyclase activating polypeptide 38 (PACAP38) alters hippocampal CA1 synaptic strength and GluA1 synaptic localization, its effect on AMPAR phosphorylation state has not been explored. We determined that PACAP38 stimulation of hippocampal cultures increased phosphorylation of S845, and decreased phosphorylation of T840 on the GluA1 AMPAR subunit. Increases in GluA1 S845 phosphorylation primarily occurred via PAC1 and VPAC2 receptor activation, whereas a reduction in GluA1 T840 phosphorylation was largely driven by PAC1 receptor activation and to a lesser extent by VPAC1 and VPAC2 receptor activation. GluA1 S845 phosphorylation could be blocked by a PKA inhibitor, and GluA1 T840 dephosphorylation could be blocked by a protein phosphatase 1/2A (PP1/PP2A) inhibitor and was partly blocked by a NMDA receptor (NMDAR) antagonist. These results demonstrate that the neuropeptide PACAP38 inversely regulates the phosphorylation of two distinct sites on GluA1 and may play an important role modulating AMPAR function and synaptic plasticity in the brain.
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