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Balbi M, Bonanno G, Bonifacino T, Milanese M. The Physio-Pathological Role of Group I Metabotropic Glutamate Receptors Expressed by Microglia in Health and Disease with a Focus on Amyotrophic Lateral Sclerosis. Int J Mol Sci 2023; 24:5240. [PMID: 36982315 PMCID: PMC10048889 DOI: 10.3390/ijms24065240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Revised: 03/03/2023] [Accepted: 03/06/2023] [Indexed: 03/30/2023] Open
Abstract
Microglia cells are the resident immune cells of the central nervous system. They act as the first-line immune guardians of nervous tissue and central drivers of neuroinflammation. Any homeostatic alteration that can compromise neuron and tissue integrity could activate microglia. Once activated, microglia exhibit highly diverse phenotypes and functions related to either beneficial or harmful consequences. Microglia activation is associated with the release of protective or deleterious cytokines, chemokines, and growth factors that can in turn determine defensive or pathological outcomes. This scenario is complicated by the pathology-related specific phenotypes that microglia can assume, thus leading to the so-called disease-associated microglia phenotypes. Microglia express several receptors that regulate the balance between pro- and anti-inflammatory features, sometimes exerting opposite actions on microglial functions according to specific conditions. In this context, group I metabotropic glutamate receptors (mGluRs) are molecular structures that may contribute to the modulation of the reactive phenotype of microglia cells, and this is worthy of exploration. Here, we summarize the role of group I mGluRs in shaping microglia cells' phenotype in specific physio-pathological conditions, including some neurodegenerative disorders. A significant section of the review is specifically focused on amyotrophic lateral sclerosis (ALS) since it represents an entirely unexplored topic of research in the field.
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Affiliation(s)
- Matilde Balbi
- Department of Pharmacy (DIFAR), University of Genoa, Viale Cembrano 4, 16148 Genova, Italy (M.M.)
| | - Giambattista Bonanno
- Department of Pharmacy (DIFAR), University of Genoa, Viale Cembrano 4, 16148 Genova, Italy (M.M.)
- IRCCS Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132 Genoa, Italy
| | - Tiziana Bonifacino
- Department of Pharmacy (DIFAR), University of Genoa, Viale Cembrano 4, 16148 Genova, Italy (M.M.)
- Inter-University Center for the Promotion of the 3Rs Principles in Teaching & Research (Centro 3R), 56122 Pisa, Italy
| | - Marco Milanese
- Department of Pharmacy (DIFAR), University of Genoa, Viale Cembrano 4, 16148 Genova, Italy (M.M.)
- IRCCS Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132 Genoa, Italy
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2
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Johnson CS, Mermelstein PG. The interaction of membrane estradiol receptors and metabotropic glutamate receptors in adaptive and maladaptive estradiol-mediated motivated behaviors in females. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2023; 168:33-91. [PMID: 36868633 DOI: 10.1016/bs.irn.2022.11.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Estrogen receptors were initially identified as intracellular, ligand-regulated transcription factors that result in genomic change upon ligand binding. However, rapid estrogen receptor signaling initiated outside of the nucleus was also known to occur via mechanisms that were less clear. Recent studies indicate that these traditional receptors, estrogen receptor α and estrogen receptor β, can also be trafficked to act at the surface membrane. Signaling cascades from these membrane-bound estrogen receptors (mERs) can rapidly alter cellular excitability and gene expression, particularly through the phosphorylation of CREB. A principal mechanism of neuronal mER action has been shown to occur through glutamate-independent transactivation of metabotropic glutamate receptors (mGlu), which elicits multiple signaling outcomes. The interaction of mERs with mGlu has been shown to be important in many diverse functions in females, including driving motivated behaviors. Experimental evidence suggests that a large part of estradiol-induced neuroplasticity and motivated behaviors, both adaptive and maladaptive, occurs through estradiol-dependent mER activation of mGlu. Herein we will review signaling through estrogen receptors, both "classical" nuclear receptors and membrane-bound receptors, as well as estradiol signaling through mGlu. We will focus on how the interactions of these receptors and their downstream signaling cascades are involved in driving motivated behaviors in females, discussing a representative adaptive motivated behavior (reproduction) and maladaptive motivated behavior (addiction).
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Affiliation(s)
- Caroline S Johnson
- Department of Neuroscience, University of Minnesota, Minneapolis, MN, United States
| | - Paul G Mermelstein
- Department of Neuroscience, University of Minnesota, Minneapolis, MN, United States.
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3
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Zhang M, Weiland H, Schöfbänker M, Zhang W. Estrogen Receptors Alpha and Beta Mediate Synaptic Transmission in the PFC and Hippocampus of Mice. Int J Mol Sci 2021; 22:ijms22031485. [PMID: 33540803 PMCID: PMC7867372 DOI: 10.3390/ijms22031485] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 01/27/2021] [Accepted: 01/28/2021] [Indexed: 12/17/2022] Open
Abstract
Distinct from ovarian estradiol, the steroid hormone 17ß-estradiol (E2) is produced in the brain and is involved in numerous functions, particularly acting as a neurosteroid. However, the physiological role of E2 and the mechanism of its effects are not well known. In hippocampal slices, 17ß-estradiol has been found to cause a modest increase in fast glutamatergic transmission; because some of these effects are rapid and acute, they might be mediated by membrane-associated receptors via nongenomic action. Moreover, activation of membrane estrogen receptors can rapidly modulate neuron function in a sex-specific manner. To further investigate the neurological role of E2, we examined the effect of E2, as an estrogen receptor (ER) agonist, on synaptic transmission in slices of the prefrontal cortex (PFC) and hippocampus in both male and female mice. Whole-cell recordings of spontaneous excitatory postsynaptic currents (sEPSC) in the PFC showed that E2 acts as a neuromodulator in glutamatergic transmission in the PFC in both sexes, but often in a cell-specific manner. The sEPSC amplitude and/or frequency responded to E2 in three ways, namely by significantly increasing, decreasing or having no response. Additional experiments using an agonist selective for ERß, diarylpropionitrile (DPN) showed that in males the sEPSC and spontaneous inhibitory postsynaptic currents sIPSC responses were similar to their E2 responses, but in females the estrogen receptor ß (ERß) agonist DPN did not influence excitatory transmission in the PFC. In contrast, in the hippocampus of both sexes E2 potentiated the gluatmatergic synaptic transmission in a subset of hippocampal cells. These data indicate that activation of E2 targeting probably a estrogen subtypes or different downstream signaling affect synaptic transmission in the brain PFC and hippocampus between males versus females mice.
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Affiliation(s)
- Mingyue Zhang
- Correspondence: ; Tel.: +49-2518-351-824; Fax: +49-2518-357-123
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4
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Planas-Fontánez TM, Dreyfus CF, Saitta KS. Reactive Astrocytes as Therapeutic Targets for Brain Degenerative Diseases: Roles Played by Metabotropic Glutamate Receptors. Neurochem Res 2020; 45:541-550. [PMID: 31983009 PMCID: PMC7058558 DOI: 10.1007/s11064-020-02968-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 01/13/2020] [Accepted: 01/18/2020] [Indexed: 02/06/2023]
Abstract
Astrocytes are well known to play critical roles in the development and maintenance of the central nervous system (CNS). Moreover, recent reports indicate that these cells are heterogeneous with respect to the molecules they express and the functions they exhibit in the quiescent or activated state. Because astrocytes also contribute to pathology, promising new results raise the possibility of manipulating specific astroglial populations for therapeutic roles. In this mini-review, we highlight the function of metabotropic glutamate receptors (mGluRs), in particular mGluR3 and mGluR5, in reactive astrocytes and relate these to three degenerative CNS diseases: multiple sclerosis, Alzheimer's disease and Amyotrophic Lateral Sclerosis. Previous studies demonstrate that effects of these receptors may be beneficial, but this varies depending on the subtype of receptor, the state of the astrocytes, and the specific disease to which they are exposed. Elucidating the role of mGluRs on astrocytes at specific times during development and disease will provide novel insights in understanding how to best use these to serve as therapeutic targets.
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Affiliation(s)
- Talia M. Planas-Fontánez
- grid.430387.b0000 0004 1936 8796Joint Graduate Program in Toxicology, Rutgers, The State University of New Jersey, Piscataway, NJ USA ,grid.430387.b0000 0004 1936 8796Department of Neuroscience and Cell Biology, Rutgers Robert Wood Johnson Medical School, Piscataway, NJ USA
| | - Cheryl F. Dreyfus
- grid.430387.b0000 0004 1936 8796Department of Neuroscience and Cell Biology, Rutgers Robert Wood Johnson Medical School, Piscataway, NJ USA ,grid.430387.b0000 0004 1936 8796Robert Wood Johnson Medical School, 683 Hoes Lane West, Room 361, Piscataway, NJ 08854 USA
| | - Kyle S. Saitta
- grid.430387.b0000 0004 1936 8796Joint Graduate Program in Toxicology, Rutgers, The State University of New Jersey, Piscataway, NJ USA ,grid.430387.b0000 0004 1936 8796Department of Neuroscience and Cell Biology, Rutgers Robert Wood Johnson Medical School, Piscataway, NJ USA
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5
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Buschler A, Manahan-Vaughan D. Metabotropic glutamate receptor, mGlu5, mediates enhancements of hippocampal long-term potentiation after environmental enrichment in young and old mice. Neuropharmacology 2016; 115:42-50. [PMID: 27267685 DOI: 10.1016/j.neuropharm.2016.06.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Revised: 06/01/2016] [Accepted: 06/02/2016] [Indexed: 12/24/2022]
Abstract
The metabotropic glutamate (mGlu) receptor, mGlu5, is of particular relevance for hippocampal function. It is critically required for the expression of long-term potentiation (LTP) and long-term depression (LTD), regulates neuronal oscillations, maintains the stability of place fields and is required for hippocampus-dependent memory. MGlu5-dysfunctions are associated with profound cognitive deficits in humans, and mGlu5 has been targeted as a putative cognitive enhancer. Cognitive enhancement, by means of environmental enrichment (EE) in rodents, results in improved hippocampal synaptic plasticity and memory. Here, we explored whether mGlu5 contributes to these enhancements. MGlu5-antagonism dose-dependently impaired the early phase of LTP (>4 h) in the CA1 region of young(3-4 month old) mice. Late-LTP (>24 h) was also impaired. LTP (>24 h) elicited in old (10-14 month old) mice displayed reduced sensitivity to mGlu5 antagonism. Short-term potentiation (STP, < 2 h) that was elicited by weaker afferent stimulation was unaffected by mGlu5-antagonism in both age-groups. EE significantly amplified STP (<2 h) in old and young animals, but did not increase the duration of synaptic potentiation, or promote induction of LTP. The improvement in STP was prevented by mGlu5-antagonism, in both young and old animals. These results indicate that modifications of the synapse that underlie improvements of LTP by EE require the contribution of mGlu5. Strikingly, although LTP in old mice does not critically depend on mGlu5, improvements in synaptic potentiation resulting from EE are mGlu5-dependent in old mice. Regarded in light of the known role for mGlu5 in hippocampal function and pathophysiology, these data suggest that mGlu5 regulation of synaptic information storage is pivotal to optimal hippocampal function. This article is part of the Special Issue entitled 'Metabotropic Glutamate Receptors, 5 years on'.
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Affiliation(s)
- Arne Buschler
- Ruhr University Bochum, Medical Faculty, Department of Neurophysiology, Bochum, Germany
| | - Denise Manahan-Vaughan
- Ruhr University Bochum, Medical Faculty, Department of Neurophysiology, Bochum, Germany.
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6
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Meitzen J, Mermelstein PG. Estrogen receptors stimulate brain region specific metabotropic glutamate receptors to rapidly initiate signal transduction pathways. J Chem Neuroanat 2011; 42:236-41. [PMID: 21458561 DOI: 10.1016/j.jchemneu.2011.02.002] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Revised: 02/14/2011] [Accepted: 02/15/2011] [Indexed: 11/17/2022]
Abstract
Estradiol and other steroid hormones modulate the nervous system and behavior on both acute and long-term time scales. Though estradiol was originally characterized as a regulator of gene expression through the action of nuclear estrogen receptors (ERs) that directly bind DNA, research over the past thirty years has firmly established that estradiol can bind to extra-nuclear ERs associated with the cellular membrane, producing changes in neurons through stimulation of various intracellular signaling pathways. Several studies have determined that the classical ERs, ERα and ERβ, mediate some of these fast-acting signaling pathways through activation of G proteins. Since ERα and ERβ are not G protein-coupled receptors, the mechanisms by which ERs can stimulate signal transduction pathways are a focus of recent research. Here we discuss recent studies illustrating one mechanism by which ERα and ERβ initiate these pathways: through direct association with metabotropic glutamate receptors (mGluRs). Estradiol binding to these membrane-localized estrogen receptors results in mGluR signaling independent of glutamate. ERs are organized with mGluRs into functional signaling microdomains via caveolin proteins. The pairing of ERs to specific mGluRs via caveolins is region specific, with ERs being linked to different mGluRs in hippocampal, striatal, and other neurons. It is becoming clear that ER signaling through mGluRs is one important mechanism by which estrogens can modulate neuron and glial physiology, ultimately impacting various aspects of nervous system function.
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Affiliation(s)
- John Meitzen
- Dept. of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA.
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7
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Malter JS, Ray BC, Westmark PR, Westmark CJ. Fragile X Syndrome and Alzheimer's Disease: Another story about APP and beta-amyloid. Curr Alzheimer Res 2010; 7:200-6. [PMID: 20088809 DOI: 10.2174/156720510791050957] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2009] [Accepted: 11/24/2009] [Indexed: 01/05/2023]
Abstract
As the mechanisms underlying neuronal development and degeneration become clarified, a number of common effectors and signaling pathways are becoming apparent. Here we describe the identification of Abeta, long considered a pathologic mediator of Alzheimers Disease and Down Syndrome, as similarly over-expressed in the neurodevelopmental disease, Fragile X Syndrome. We also show that mGluR5 inhibitors, currently employed for the treatment of Fragile X, reduce Abeta production in rodent models of Fragile X and AD as well as reduce disease phenotypes including seizures. Thus seemingly disparate neurologic diseases may share a common pathologic instigator and be treatable with a common, currently available class of therapeutics.
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Affiliation(s)
- J S Malter
- Department of Pathology, Waisman Center for Developmental Disabilities, UWMadison, WI, USA.
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8
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9
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Viwatpinyo K, Chongthammakun S. Activation of group I metabotropic glutamate receptors leads to brain-derived neurotrophic factor expression in rat C6 cells. Neurosci Lett 2009; 467:127-30. [PMID: 19822193 DOI: 10.1016/j.neulet.2009.10.020] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2009] [Revised: 10/05/2009] [Accepted: 10/06/2009] [Indexed: 11/18/2022]
Abstract
Brain-derived neurotrophic factor (BDNF), which mediates neuronal growth, neuroprotection and synaptic modulation, is expressed in neurons and glial cells. The present study investigated the expression of BDNF in response to the activation of group I metabotropic glutamate receptors (mGluRs) by (S)-3,5-Dihydroxyphenylglycine (DHPG) in rat C6 glioma cells. The increase in BDNF mRNA in DHPG-stimulated cells, which peaked by 12h after DHPG exposure, was attenuated by the mGluR5 inhibitor MPEP, but not by the mGluR1 inhibitor CPCCOEt. DHPG-induced BDNF mRNA expression reduced in cultures pretreated with protein kinase C (PKC) inhibitor, GFX, but not with calcium/calmodulin kinase II (CaMKII) inhibitor, KN-93. Immunostaining revealed high BDNF expression in cytoplasm of C6 cells after 48h of incubation with 1muM DHPG, but this was lower in MPEP-pretreated cells. These results indicate that activation of group I mGluRs induces BDNF mRNA and protein expression via mGluR5 subtype and PKC-dependent signaling pathway in C6 glioma cells.
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Affiliation(s)
- Kittikun Viwatpinyo
- Department of Anatomy, Faculty of Science, Mahidol University, Rama VI Road, Bangkok 10400, Thailand
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10
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Boulware MI, Mermelstein PG. Membrane estrogen receptors activate metabotropic glutamate receptors to influence nervous system physiology. Steroids 2009; 74:608-13. [PMID: 19070630 PMCID: PMC2799184 DOI: 10.1016/j.steroids.2008.11.013] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2008] [Revised: 11/06/2008] [Accepted: 11/07/2008] [Indexed: 11/21/2022]
Abstract
Until recently, the idea that estradiol could affect cellular processes independent of nuclear estrogen receptors was often dismissed as artifact. This in spite of a large number of carefully controlled studies performed both within and outside the nervous system demonstrating estrogens regulate various intracellular signaling pathways by acting at the membrane surface of cells and/or at biological rates incompatible with the time course of genomic-initiated events. The concept that estradiol can act on surface membrane receptors to regulate nervous system function is now far less controversial. However, there is evidence that there may be multiple types of estrogen receptors on the membrane surface of cells. Determining the physiological relevance of each of these receptors is currently underway. Two important membrane estrogen receptors are in fact the classical estrogen receptor-alpha (ERalpha) and estrogen receptor-beta (ERbeta) proteins, which is somewhat surprising based upon their well-established role in nuclear gene transcription. This review will focus on the mechanism by which surface-localized ERalpha and ERbeta stimulate intracellular signaling events in cells of the nervous system through activation of metabotropic glutamate receptors (mGluRs). This mechanism of estrogen receptor function also requires caveolin proteins, which provide the subcellular compartmentalization of the particular signaling components required for appropriate cell stimulation. The review will conclude with several examples of physiological processes under the apparent regulation of ER/mGluR signaling.
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Affiliation(s)
- Marissa I. Boulware
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, United States
| | - Paul G. Mermelstein
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, United States
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11
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Mermelstein PG. Membrane-localised oestrogen receptor alpha and beta influence neuronal activity through activation of metabotropic glutamate receptors. J Neuroendocrinol 2009; 21:257-62. [PMID: 19207809 PMCID: PMC2805164 DOI: 10.1111/j.1365-2826.2009.01838.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Until recently, the idea that oestradiol could affect cellular processes independent of nuclear oestrogen receptors (ERs) was controversial. This was despite the large number of carefully controlled studies performed both within and outside the nervous system demonstrating that oestrogens regulate various intracellular signalling pathways by acting at the membrane surface of cells and/or at biological rates incompatible with the time course of genomic-initiated events. At present, it is far less controversial that oestradiol acts at surface membrane receptors to regulate nervous system function. Recent studies have demonstrated that the classical intracellular ERs, ERalpha and ERbeta, are major players in mediating the actions of oestradiol on the membrane surface. This review focuses on one potential mechanism by which surface-localised ERalpha and ERbeta stimulate intracellular signalling events in cells of the nervous system. After oestradiol treatment, both ERalpha and ERbeta are capable of activating different classes of metabotropic glutamate receptors (mGluRs). Oestradiol activation of mGluRs is independent of glutamate, but requires expression of several different caveolin proteins to compartmentalise the different ERs with mGluRs into functional signalling microdomains. ER/mGluR signalling is a potential means by which oestrogens can both rapidly and for extended periods, influence a variety of intracellular signalling processes and behaviours.
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Affiliation(s)
- P G Mermelstein
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA.
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12
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Ferraguti F, Crepaldi L, Nicoletti F. Metabotropic glutamate 1 receptor: current concepts and perspectives. Pharmacol Rev 2009; 60:536-81. [PMID: 19112153 DOI: 10.1124/pr.108.000166] [Citation(s) in RCA: 154] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Almost 25 years after the first report that glutamate can activate receptors coupled to heterotrimeric G-proteins, tremendous progress has been made in the field of metabotropic glutamate receptors. Now, eight members of this family of glutamate receptors, encoded by eight different genes that share distinctive structural features have been identified. The first cloned receptor, the metabotropic glutamate (mGlu) receptor mGlu1 has probably been the most extensively studied mGlu receptor, and in many respects it represents a prototypical subtype for this family of receptors. Its biochemical, anatomical, physiological, and pharmacological characteristics have been intensely investigated. Together with subtype 5, mGlu1 receptors constitute a subgroup of receptors that couple to phospholipase C and mobilize Ca(2+) from intracellular stores. Several alternatively spliced variants of mGlu1 receptors, which differ primarily in the length of their C-terminal domain and anatomical localization, have been reported. Use of a number of genetic approaches and the recent development of selective antagonists have provided a means for clarifying the role played by this receptor in a number of neuronal systems. In this article we discuss recent advancements in the pharmacology and concepts about the intracellular transduction and pathophysiological role of mGlu1 receptors and review earlier data in view of these novel findings. The impact that this new and better understanding of the specific role of these receptors may have on novel treatment strategies for a variety of neurological and psychiatric disorders is considered.
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Affiliation(s)
- Francesco Ferraguti
- Department of Pharmacology, Innsbruck Medical University, Peter-Mayr Strasse 1a, Innsbruck A-6020, Austria.
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Byrnes KR, Loane DJ, Faden AI. Metabotropic glutamate receptors as targets for multipotential treatment of neurological disorders. Neurotherapeutics 2009; 6:94-107. [PMID: 19110202 PMCID: PMC2634659 DOI: 10.1016/j.nurt.2008.10.038] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Glutamate is a major excitatory neurotransmitter in the CNS that is involved in numerous cellular functions, including cell death and survival. Metabotropic glutamate receptors (mGluR) are G-protein coupled receptors that have been classified into three groups on the basis of signal transduction pathways and pharmacological profiles. Group I, II, and III mGluRs are found on cell types within and peripheral to the CNS, including neurons, microglia, astrocytes, oligodendrocytes, T- and B-cell lymphocytes, osteoblasts, hepatocytes, and endothelial cells, among others. These receptors have a number of effects on cells that can influence outcome after trauma, including reducing neuronal and oligodendroglial cell death, inflammation, and endothelial permeability. Thus, mGluRs are a promising multipotential therapeutic approach. Because the pathology of CNS trauma and neurodegeneration is multifactorial (including, for example, oxidative stress, mitochondrial breakdown, and inflammation), therapies that serve to modulate multiple pathophysiological pathways may prove more effective than those directed at a single target. This review examines the multipotential therapeutic utility of mGluR modulation in acute and chronic injury and neurodegeneration.
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Affiliation(s)
- Kimberly R Byrnes
- Department of Neuroscience, Georgetown University Medical Center, Washington, DC 20057, USA.
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14
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Micevych PE, Mermelstein PG. Membrane estrogen receptors acting through metabotropic glutamate receptors: an emerging mechanism of estrogen action in brain. Mol Neurobiol 2008; 38:66-77. [PMID: 18670908 DOI: 10.1007/s12035-008-8034-z] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2008] [Accepted: 06/18/2008] [Indexed: 12/27/2022]
Abstract
It has been over 60 years since the first studies have been published describing the effects of steroid hormones on brain function. For over 30 years, estrogen has been presumed to directly affect gene expression and protein synthesis through a specific receptor. More than 20 years ago, the first estrogen receptor was cloned and identified as a transcription factor. Yet, throughout their course of study, estrogens have also been observed to affect nervous system function via mechanisms independent of intracellular receptor regulation of gene expression. Up until recently, the membrane estrogen receptors responsible for these rapid actions have remained elusive. Recent studies have demonstrated that a large number of these rapid, membrane-initiated actions of estradiol are due to surface expression of classical estrogen receptors. This review focuses on the importance of membrane estrogen receptor interactions with metabotropic glutamate receptors for understanding rapid estradiol signaling mechanisms and downstream effectors, as well as their significance in a variety of physiological processes.
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Affiliation(s)
- Paul E Micevych
- Department of Neurobiology and Laboratory of Neuroendocrinology of the Brain Research Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
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15
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Kelley DJ, Bhattacharyya A, Lahvis GP, Yin JCP, Malter J, Davidson RJ. The cyclic AMP phenotype of fragile X and autism. Neurosci Biobehav Rev 2008; 32:1533-43. [PMID: 18601949 DOI: 10.1016/j.neubiorev.2008.06.005] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2008] [Revised: 06/06/2008] [Accepted: 06/08/2008] [Indexed: 12/27/2022]
Abstract
Cyclic AMP (cAMP) is a second messenger involved in many processes including mnemonic processing and anxiety. Memory deficits and anxiety are noted in the phenotype of fragile X (FX), the most common heritable cause of mental retardation and autism. Here we review reported observations of altered cAMP cascade function in FX and autism. Cyclic AMP is a potentially useful biochemical marker to distinguish autism comorbid with FX from autism per se and the cAMP cascade may be a viable therapeutic target for both FX and autism.
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Affiliation(s)
- Daniel J Kelley
- Waisman Laboratory for Brain Imaging and Behavior, Waisman Center, University of Wisconsin, Madison, WI, USA.
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Roles of calcium-stimulated adenylyl cyclase and calmodulin-dependent protein kinase IV in the regulation of FMRP by group I metabotropic glutamate receptors. J Neurosci 2008; 28:4385-97. [PMID: 18434517 DOI: 10.1523/jneurosci.0646-08.2008] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The fragile X syndrome is caused by the lack of fragile X mental retardation protein (FMRP) attributable to silencing of the FMR1 gene. The metabotropic glutamate receptors (mGluRs) in the CNS contribute to different brain functions, including learning/memory, mental disorders, drug addiction, and persistent pain. Most of the previous studies have been focused on downstream targets of FMRP in hippocampal neurons, and fewer studies have been reported for the second-messenger signaling pathways between group I mGluRs and FMRP. Furthermore, no molecular study has been performed in the anterior cingulate cortex (ACC), a key region involved in high brain cognitive and executive functions. In this study, we demonstrate that activation of group I mGluR upregulated FMRP in ACC neurons of adult mice through the Ca(2+)-dependent signaling pathways. Using genetic approaches, we found that Ca(2+)/calmodulin-stimulated adenylyl cyclase 1 (AC1) and calcium/calmodulin-dependent kinase IV (CaMKIV) contribute to the upregulation of FMRP induced by stimulating group I mGluRs. The upregulation of FMRP occurs at the transcriptional level. The cAMP-dependent protein kinase is activated by stimulating group I mGluRs through AC1 in ACC neurons. Both AC1 and CaMKIV contribute to the regulation of FMRP by group I mGluRs probably through cAMP response element-binding protein activation. Our study has provided the first evidence for a molecular link between group I mGluRs and FMRP in ACC neurons and may help us to understand the pathogenesis of fragile X syndrome.
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Rosethorne EM, Nahorski SR, Challiss RJ. Regulation of cyclic AMP response-element binding-protein (CREB) by Gq/11-protein-coupled receptors in human SH-SY5Y neuroblastoma cells. Biochem Pharmacol 2007; 75:942-55. [PMID: 18036509 PMCID: PMC2593902 DOI: 10.1016/j.bcp.2007.10.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2007] [Revised: 10/03/2007] [Accepted: 10/11/2007] [Indexed: 11/18/2022]
Abstract
Human SH-SY5Y neuroblastoma cells have been used to investigate mechanisms involved in CREB phosphorylation after activation of two endogenously expressed Gq/11-protein-coupled receptors, the M3 muscarinic acetylcholine (mACh) and B2 bradykinin receptors. Stimulation with either methacholine or bradykinin resulted in maximal increases in CREB phosphorylation within 1 min, with either a rapid subsequent decrease (bradykinin) to basal levels, or a sustained response (methacholine). Inhibitor studies were performed to assess the involvement of a number of potential kinases in signalling to CREB phosphorylation. Removal of extracellular Ca2+, inhibition of Ca2+/calmodulin-dependent protein kinase II and down-regulation of protein kinase C (PKC) resulted in reduced CREB phosphorylation after both M3 mACh and B2 bradykinin receptor activation. In contrast, inhibition of MEK1/2 by U0126 resulted in significantly reduced CREB phosphorylation levels after B2 bradykinin, but not M3 mACh receptor activation. In addition, we demonstrate that maintained phosphorylation of CREB is necessary for CRE-dependent gene transcription as the M3 mACh, but not the B2 bradykinin receptor activates both a recombinant CRE-dependent reporter gene, and the endogenous c-Fos gene. These data highlight the involvement of multiple, overlapping signalling pathways linking these endogenous Gq/11-coupled metabotropic receptors to CREB and emphasize the importance of the duration of signalling pathway activation in converting a CREB phosphorylation event into a significant change in transcriptional activity.
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Kelley DJ, Davidson RJ, Elliott JL, Lahvis GP, Yin JCP, Bhattacharyya A. The cyclic AMP cascade is altered in the fragile X nervous system. PLoS One 2007; 2:e931. [PMID: 17895972 PMCID: PMC1976557 DOI: 10.1371/journal.pone.0000931] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2007] [Accepted: 09/04/2007] [Indexed: 01/31/2023] Open
Abstract
Fragile X syndrome (FX), the most common heritable cause of mental retardation and autism, is a developmental disorder characterized by physical, cognitive, and behavioral deficits. FX results from a trinucleotide expansion mutation in the fmr1 gene that reduces levels of fragile X mental retardation protein (FMRP). Although research efforts have focused on FMRP's impact on mGluR signaling, how the loss of FMRP leads to the individual symptoms of FX is not known. Previous studies on human FX blood cells revealed alterations in the cyclic adenosine 3', 5'-monophosphate (cAMP) cascade. We tested the hypothesis that cAMP signaling is altered in the FX nervous system using three different model systems. Induced levels of cAMP in platelets and in brains of fmr1 knockout mice are substantially reduced. Cyclic AMP induction is also significantly reduced in human FX neural cells. Furthermore, cAMP production is decreased in the heads of FX Drosophila and this defect can be rescued by reintroduction of the dfmr gene. Our results indicate that a robust defect in cAMP production in FX is conserved across species and suggest that cAMP metabolism may serve as a useful biomarker in the human disease population. Reduced cAMP induction has implications for the underlying causes of FX and autism spectrum disorders. Pharmacological agents known to modulate the cAMP cascade may be therapeutic in FX patients and can be tested in these models, thus supplementing current efforts centered on mGluR signaling.
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Affiliation(s)
- Daniel J. Kelley
- Waisman Laboratory for Brain Imaging and Behavior, Waisman Center, University of Wisconsin, Madison, Wisconsin, United States of America
- Neuroscience Training Program, University of Wisconsin School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin, United States of America
- Medical Scientist Training Program, University of Wisconsin School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Richard J. Davidson
- Waisman Laboratory for Brain Imaging and Behavior, Waisman Center, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Jamie L. Elliott
- Medical Scientist Training Program, University of Wisconsin School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin, United States of America
- Department of Genetics, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Garet P. Lahvis
- Department of Surgery, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Jerry C. P. Yin
- Department of Genetics, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Anita Bhattacharyya
- Stem Cells and Developmental Disorders Laboratory, Waisman Center, University of Wisconsin, Madison, Wisconsin, United States of America
- * To whom correspondence should be addressed. E-mail:
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Garber K, Smith KT, Reines D, Warren ST. Transcription, translation and fragile X syndrome. Curr Opin Genet Dev 2006; 16:270-5. [PMID: 16647847 DOI: 10.1016/j.gde.2006.04.010] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2006] [Accepted: 04/18/2006] [Indexed: 10/24/2022]
Abstract
The fragile X mental retardation protein (FMRP) plays a role in the control of local protein synthesis in the dendrites. Loss of its production in fragile X syndrome is associated with transcriptional dysregulation of the gene. Recent work demonstrates that Sp1 and NRF1 transcriptionally control this gene. Other studies reveal how the microRNA pathway and signaling are related to FMRP function through the metabotropic glutamate receptor. These studies provide new insights through which we can better understand the inactivation of the FMR1 gene and, in turn, the consequence of FMRP loss.
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Affiliation(s)
- Kathryn Garber
- Department of Human Genetics, 615 Michael Street, Room 300, Emory University, Atlanta, GA 30322, USA
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Smith KT, Nicholls RD, Reines D. The gene encoding the fragile X RNA-binding protein is controlled by nuclear respiratory factor 2 and the CREB family of transcription factors. Nucleic Acids Res 2006; 34:1205-15. [PMID: 16500891 PMCID: PMC1383620 DOI: 10.1093/nar/gkj521] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
FMR1 encodes an RNA-binding protein whose absence results in fragile X mental retardation. In most patients, the FMR1 gene is cytosine-methylated and transcriptionally inactive. NRF-1 and Sp1 are known to bind and stimulate the active, but not the methylated/silenced, FMR1 promoter. Prior analysis has implicated a CRE site in regulation of FMR1 in neural cells but the role of this site is controversial. We now show that a phospho-CREB/ATF family member is bound to this site in vivo. We also find that the histone acetyltransferases CBP and p300 are associated with active FMR1 but are lost at the hypoacetylated fragile X allele. Surprisingly, FMR1 is not cAMP-inducible and resides in a newly recognized subclass of CREB-regulated genes. We have also elucidated a role for NRF-2 as a regulator of FMR1 in vivo through a previously unrecognized and highly conserved recognition site in FMR1. NRF-1 and NRF-2 act additively while NRF-2 synergizes with CREB/ATF at FMR1's promoter. These data add FMR1 to the collection of genes controlled by both NRF-1 and NRF-2 and disfavor its membership in the immediate early response group of genes.
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Affiliation(s)
| | - Robert D. Nicholls
- Birth Defects Laboratories and Division of Medical Genetics, Department of Pediatrics, Children's Hospital of Pittsburgh3705 Fifth Avenue, Pittsburgh, PA 15213, USA
| | - Daniel Reines
- To whom correspondence should be addressed. Tel: +1 404 727 3361; Fax: +1 404 727 3452;
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Abstract
Ultrasensitive responses are common in cellular information transfer because they allow cells to decode extracellular stimuli in an all-or-none manner. Biochemical responses are usually analyzed by fitting the Hill equation, and the estimated Hill coefficient is taken as a measure of sensitivity. However, this approach is not appropriate if the response under consideration significantly deviates from the best-fit Hill equation. In addition, Hill coefficients greater than unity do not necessarily imply ultrasensitive behaviour if basal activation is significant. In order to circumvent these problems we propose a general method for the quantitative analysis of sensitivity, the relative amplification plot, which is based on the response coefficient defined in metabolic control analysis. To quantify sensitivity globally (i.e. over the whole stimulus range) we introduce the integral-based relative amplification coefficient. Our relative amplification approach can easily be extended to monotonically decreasing, bell-shaped or nonsaturated responses.
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Affiliation(s)
- Stefan Legewie
- Institute for Theoretical Biology, Humboldt University Berlin, Germany.
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