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Brunetti V, Soda T, Berra-Romani R, De Sarro G, Guerra G, Scarpellino G, Moccia F. Two Signaling Modes Are Better than One: Flux-Independent Signaling by Ionotropic Glutamate Receptors Is Coming of Age. Biomedicines 2024; 12:880. [PMID: 38672234 PMCID: PMC11048239 DOI: 10.3390/biomedicines12040880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2024] [Revised: 04/02/2024] [Accepted: 04/12/2024] [Indexed: 04/28/2024] Open
Abstract
Glutamate is the major excitatory neurotransmitter in the central nervous system. Glutamatergic transmission can be mediated by ionotropic glutamate receptors (iGluRs), which mediate rapid synaptic depolarization that can be associated with Ca2+ entry and activity-dependent change in the strength of synaptic transmission, as well as by metabotropic glutamate receptors (mGluRs), which mediate slower postsynaptic responses through the recruitment of second messenger systems. A wealth of evidence reported over the last three decades has shown that this dogmatic subdivision between iGluRs and mGluRs may not reflect the actual physiological signaling mode of the iGluRs, i.e., α-amino-3-hydroxy-5-methyl-4-isoxasolepropionic acid (AMPA) receptors (AMPAR), kainate receptors (KARs), and N-methyl-D-aspartate (NMDA) receptors (NMDARs). Herein, we review the evidence available supporting the notion that the canonical iGluRs can recruit flux-independent signaling pathways not only in neurons, but also in brain astrocytes and cerebrovascular endothelial cells. Understanding the signaling versatility of iGluRs can exert a profound impact on our understanding of glutamatergic synapses. Furthermore, it may shed light on novel neuroprotective strategies against brain disorders.
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Affiliation(s)
- Valentina Brunetti
- Laboratory of General Physiology, Department of Biology and Biotechnology “L. Spallanzani”, 27110 Pavia, Italy; (V.B.); (G.S.)
| | - Teresa Soda
- Department of Health Sciences, School of Medicine and Surgery, Magna Graecia University of Catanzaro, 88100 Catanzaro, Italy; (T.S.); (G.D.S.)
| | - Roberto Berra-Romani
- Department of Biomedicine, School of Medicine, Benemérita Universidad Autónoma de Puebla, Puebla 72410, Mexico;
| | - Giovambattista De Sarro
- Department of Health Sciences, School of Medicine and Surgery, Magna Graecia University of Catanzaro, 88100 Catanzaro, Italy; (T.S.); (G.D.S.)
- System and Applied Pharmacology@University Magna Grecia, Science of Health Department, School of Medicine, Magna Graecia University of Catanzaro, 88110 Catanzaro, Italy
| | - Germano Guerra
- Department of Medicine and Health Science “Vincenzo Tiberio”, School of Medicine and Surgery, University of Molise, 86100 Campobasso, Italy;
| | - Giorgia Scarpellino
- Laboratory of General Physiology, Department of Biology and Biotechnology “L. Spallanzani”, 27110 Pavia, Italy; (V.B.); (G.S.)
| | - Francesco Moccia
- Department of Medicine and Health Science “Vincenzo Tiberio”, School of Medicine and Surgery, University of Molise, 86100 Campobasso, Italy;
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Pressey JC, Woodin MA. Kainate receptor regulation of synaptic inhibition in the hippocampus. J Physiol 2020; 599:485-492. [PMID: 32162694 DOI: 10.1113/jp279645] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Accepted: 03/02/2020] [Indexed: 12/13/2022] Open
Abstract
Kainate receptors (KARs) are glutamate-type receptors that mediate both canonical ionotropic currents and non-canonical metabotropic signalling. While KARs are expressed widely throughout the brain, synaptic KAR currents have only been recorded at a limited set of synapses, and the KAR currents that have been recorded are relatively small and slow, which has led to the question, what is the functional significance of KARs? While the KAR current itself is relatively modest, its impact on inhibition in the hippocampus can be profound. In the CA1 region of the hippocampus, presynaptic KAR activation bidirectionally regulates γ-aminobutyric acid (GABA) release in a manner that depends on the glutamate concentration; lower levels of glutamate facilitate GABA release via an ionotropic pathway, while higher levels of glutamate depress GABA release via a metabotropic pathway. Postsynaptic interneuron KAR activation increases spike frequency through an ionotropic current, which in turn can strengthen inhibition. In the CA3 region, postsynaptic KAR activation in pyramidal neurons also strengthens inhibition, but in this case through a metabotropic pathway which regulates the neuronal chloride gradient and hyperpolarizes the reversal potential for GABA (EGABA ). Taken together, the evidence for KAR-mediated regulation of the strength of inhibition via pre- and postsynaptic mechanisms provides compelling evidence that KARs are ideally positioned to regulate excitation-inhibition balance - through sensing the excitatory tone and concomitantly tuning the strength of inhibition.
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Affiliation(s)
- Jessica C Pressey
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Melanie A Woodin
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
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Gandolfi D, Bigiani A, Porro CA, Mapelli J. Inhibitory Plasticity: From Molecules to Computation and Beyond. Int J Mol Sci 2020; 21:ijms21051805. [PMID: 32155701 PMCID: PMC7084224 DOI: 10.3390/ijms21051805] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 02/28/2020] [Accepted: 03/03/2020] [Indexed: 11/17/2022] Open
Abstract
Synaptic plasticity is the cellular and molecular counterpart of learning and memory and, since its first discovery, the analysis of the mechanisms underlying long-term changes of synaptic strength has been almost exclusively focused on excitatory connections. Conversely, inhibition was considered as a fixed controller of circuit excitability. Only recently, inhibitory networks were shown to be finely regulated by a wide number of mechanisms residing in their synaptic connections. Here, we review recent findings on the forms of inhibitory plasticity (IP) that have been discovered and characterized in different brain areas. In particular, we focus our attention on the molecular pathways involved in the induction and expression mechanisms leading to changes in synaptic efficacy, and we discuss, from the computational perspective, how IP can contribute to the emergence of functional properties of brain circuits.
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Affiliation(s)
- Daniela Gandolfi
- Department of Biomedical, Metabolic and Neural Sciences and Center for Neuroscience and Neurotechnology, University of Modena and Reggio Emilia, Via Campi 287, 41125 Modena, Italy; (D.G.); (A.B.); (C.A.P.)
- Department of Brain and behavioral sciences, University of Pavia, 27100 Pavia, Italy
| | - Albertino Bigiani
- Department of Biomedical, Metabolic and Neural Sciences and Center for Neuroscience and Neurotechnology, University of Modena and Reggio Emilia, Via Campi 287, 41125 Modena, Italy; (D.G.); (A.B.); (C.A.P.)
| | - Carlo Adolfo Porro
- Department of Biomedical, Metabolic and Neural Sciences and Center for Neuroscience and Neurotechnology, University of Modena and Reggio Emilia, Via Campi 287, 41125 Modena, Italy; (D.G.); (A.B.); (C.A.P.)
| | - Jonathan Mapelli
- Department of Biomedical, Metabolic and Neural Sciences and Center for Neuroscience and Neurotechnology, University of Modena and Reggio Emilia, Via Campi 287, 41125 Modena, Italy; (D.G.); (A.B.); (C.A.P.)
- Correspondence: ; Tel.: +39-059-205- 5459
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Chiu CQ, Barberis A, Higley MJ. Preserving the balance: diverse forms of long-term GABAergic synaptic plasticity. Nat Rev Neurosci 2019; 20:272-281. [PMID: 30837689 DOI: 10.1038/s41583-019-0141-5] [Citation(s) in RCA: 70] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Cellular mechanisms that regulate the interplay of synaptic excitation and inhibition are thought to be central to the functional stability of healthy neuronal circuits. A growing body of literature demonstrates the capacity for inhibitory GABAergic synapses to exhibit long-term plasticity in response to changes in neuronal activity. Here, we review this expanding field of research, focusing on the diversity of mechanisms that link glutamatergic signalling, postsynaptic action potentials and inhibitory synaptic strength. Several lines of evidence indicate that multiple, parallel forms of plasticity serve to regulate activity at both the input and output domains of individual neurons. Overall, these varied phenomena serve to promote both stability and flexibility over the life of the organism.
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Affiliation(s)
- Chiayu Q Chiu
- Centro Interdisciplinario de Neurociencia de Valparaiso, Universidad de Valparaiso, Valparaiso, Chile
| | | | - Michael J Higley
- Department of Neuroscience, Yale University, New Haven, CT, USA.
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Maniezzi C, Talpo F, Spaiardi P, Toselli M, Biella G. Oxytocin Increases Phasic and Tonic GABAergic Transmission in CA1 Region of Mouse Hippocampus. Front Cell Neurosci 2019; 13:178. [PMID: 31133808 PMCID: PMC6516053 DOI: 10.3389/fncel.2019.00178] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Accepted: 04/12/2019] [Indexed: 11/17/2022] Open
Abstract
Oxytocin is a neuropeptide that plays important peripheral and central neuromodulatory functions. Our data show that, following activation of oxytocin receptors (OtRs) with the selective agonist TGOT (Thr4,Gly7-oxytocin), a significant increase in frequency and amplitude of spontaneous inhibitory postsynaptic currents (sIPSC) occurred in hippocampal CA1 pyramidal neurons (PYR) in mice. TGOT affected also sIPSC deactivation kinetics, suggesting the involvement of perisynaptic GABAA receptors (GABAARs) as well. By contrast, TGOT did not cause significant changes in frequency, amplitude or deactivation kinetics of miniature IPSC, suggesting that the effects elicited by the agonist are strictly dependent on the firing activity of presynaptic neurons. Moreover, TGOT was able to modulate tonic GABAergic current mediated by extrasynaptic GABAARs expressed by PYRs. Consistently, at spike threshold TGOT induced in most PYRs a significant membrane hyperpolarization and a decrease in firing rate. The source of increased inhibition onto PYRs was represented by stuttering fast-spiking GABAergic interneurons (INs) that directly respond to TGOT with a depolarization and an increase in their firing rate. One putative ionic mechanism underlying this effect could be represented by OtR activation-induced up-modulation of L-type Ca2+ channels. In conclusion, our results indicate that oxytocin can influence the activity of a subclass of hippocampal GABAergic INs and therefore regulate the operational modes of the downstream PYRs by increasing phasic and tonic GABAergic transmission in CA1 region of mouse hippocampus.
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Affiliation(s)
- Claudia Maniezzi
- Laboratory of Physiology, Department of Biology and Biotechnology "Lazzaro Spallanzani", University of Pavia, Pavia, Italy
| | - Francesca Talpo
- Laboratory of Physiology, Department of Biology and Biotechnology "Lazzaro Spallanzani", University of Pavia, Pavia, Italy
| | - Paolo Spaiardi
- Neurophysiology Unit, Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy
| | - Mauro Toselli
- Laboratory of Physiology, Department of Biology and Biotechnology "Lazzaro Spallanzani", University of Pavia, Pavia, Italy
| | - Gerardo Biella
- Laboratory of Physiology, Department of Biology and Biotechnology "Lazzaro Spallanzani", University of Pavia, Pavia, Italy
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Mazzone GL, Nistri A. Modulation of extrasynaptic GABAergic receptor activity influences glutamate release and neuronal survival following excitotoxic damage to mouse spinal cord neurons. Neurochem Int 2019; 128:175-185. [PMID: 31051211 DOI: 10.1016/j.neuint.2019.04.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 04/08/2019] [Accepted: 04/30/2019] [Indexed: 12/14/2022]
Abstract
Excitotoxic levels of released glutamate trigger a cascade of deleterious cellular events leading to delayed neuronal death. This phenomenon implies extensive dysregulation in the balance between network excitation and inhibition. Our hypothesis was that enhancing network inhibition should prevent excitotoxicity and provide neuroprotection. To test this notion, we used mouse organotypic spinal slice cultures and explored if excitotoxicity caused by the potent glutamate analogue kainate was blocked by pharmacological increase in GABAA receptor activity. To this end we monitored (with a biosensor) real-time glutamate release following 1 h kainate application and quantified neuronal survival 24 h later. Glutamate release evoked by kainate was strongly decreased by the allosteric GABAA modulator midazolam (10 nM) or the GABA agonist THIP (10 μM), leading to neuroprotection. On the contrary, much higher glutamate release was induced by the GABA antagonist bicuculline (20 μM) that inhibits synaptic and extrasynaptic GABAA receptors. Gabazine (20 μM), an antagonist of synaptic GABAA receptors, had no effect on glutamate release or neuroprotection. No effect was observed with the glycine antagonist strychnine or the glycine agonist L-alanine. These findings indicate that enhancement of GABA receptor activity was an effective tool to counteract excitotoxic death in spinal networks. In view of the potent activity by THIP, preferentially acting on extrasynaptic GABAA receptors, the present data imply a significant role for extrasynaptic GABAA receptors in sparing spinal cord neurons from injury.
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Affiliation(s)
- Graciela L Mazzone
- Instituto de Investigaciones en Medicina Traslacional (IIMT), CONICET-Universidad Austral, Derqui-Pilar, Buenos Aires, Argentina.
| | - Andrea Nistri
- Neuroscience Dept., International School for Advanced Studies (SISSA), Trieste, Italy
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Exciting Times: New Advances Towards Understanding the Regulation and Roles of Kainate Receptors. Neurochem Res 2017; 44:572-584. [PMID: 29270706 PMCID: PMC6420428 DOI: 10.1007/s11064-017-2450-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Revised: 11/27/2017] [Accepted: 12/07/2017] [Indexed: 12/11/2022]
Abstract
Kainate receptors (KARs) are glutamate-gated ion channels that play fundamental roles in regulating neuronal excitability and network function in the brain. After being cloned in the 1990s, important progress has been made in understanding the mechanisms controlling the molecular and cellular properties of KARs, and the nature and extent of their regulation of wider neuronal activity. However, there have been significant recent advances towards understanding KAR trafficking through the secretory pathway, their precise synaptic positioning, and their roles in synaptic plasticity and disease. Here we provide an overview highlighting these new findings about the mechanisms controlling KARs and how KARs, in turn, regulate other proteins and pathways to influence synaptic function.
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Expression and cellular distribution of transient receptor potential vanilloid 4 in cortical tubers of the tuberous sclerosis complex. Brain Res 2016; 1636:183-192. [DOI: 10.1016/j.brainres.2016.02.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Revised: 01/27/2016] [Accepted: 02/04/2016] [Indexed: 11/24/2022]
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Chen X, Sun FJ, Wei YJ, Wang LK, Zang ZL, Chen B, Li S, Liu SY, Yang H. Increased Expression of Transient Receptor Potential Vanilloid 4 in Cortical Lesions of Patients with Focal Cortical Dysplasia. CNS Neurosci Ther 2016; 22:280-90. [PMID: 26842013 DOI: 10.1111/cns.12494] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Revised: 11/10/2015] [Accepted: 11/14/2015] [Indexed: 12/13/2022] Open
Abstract
AIM Focal cortical dysplasia (FCD) represents a well-known cause of medically intractable epilepsy. Studies found that transient receptor potential vanilloid receptor 4 (TRPV4) may participate in the occurrence of seizures. This study investigated the expression patterns of TRPV4 in FCD and the cascade that regulate functional state of TRPV4 in cortical neurons. METHODS Thirty-nine surgical specimens from FCD patients and 10 age-matched control samples from autopsies were included in this study. Protein expression and distribution were detected by Western blot, immunohistochemistry, and immunofluorescence staining. Calcium imaging was used to detect the TRPV4-mediated Ca(2+) influx in cortical neurons. RESULTS (1) The protein levels of TRPV4 and of an upstream factor, protein kinase C (PKC), were markedly elevated in FCD. (2) TRPV4 staining was stronger in the dysplastic cortices of FCD and mainly observed in neuronal microcolumns and malformed cells. (3) The activation of TRPV4 was central for [Ca(2+)]i elevation in cortical neurons, and this activity of TRPV4 in cortical neurons was regulated by the PKC, but not the PKA, pathway. CONCLUSION The overexpression and altered cellular distribution of TRPV4 in FCD suggest that TRPV4 may potentially contribute to the epileptogenesis of FCD.
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Affiliation(s)
- Xin Chen
- Department of Neurosurgery, Xinqiao Hospital, Third Military Medical University, Chongqing, China
| | - Fei-Ji Sun
- Department of Neurosurgery, Xinqiao Hospital, Third Military Medical University, Chongqing, China
| | - Yu-Jia Wei
- Department of Neurosurgery, Xinqiao Hospital, Third Military Medical University, Chongqing, China
| | - Lu-Kang Wang
- Department of Neurosurgery, Xinqiao Hospital, Third Military Medical University, Chongqing, China
| | - Zhen-Le Zang
- Department of Neurosurgery, Xinqiao Hospital, Third Military Medical University, Chongqing, China
| | - Bing Chen
- Department of Neurosurgery, Xinqiao Hospital, Third Military Medical University, Chongqing, China
| | - Song Li
- Department of Neurosurgery, Xinqiao Hospital, Third Military Medical University, Chongqing, China
| | - Shi-Yong Liu
- Department of Neurosurgery, Xinqiao Hospital, Third Military Medical University, Chongqing, China
| | - Hui Yang
- Department of Neurosurgery, Xinqiao Hospital, Third Military Medical University, Chongqing, China
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