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Blaylock RL. Additive aluminum as a cause of induced immunoexcitoxicity resulting in neurodevelopmental and neurodegenerative disorders: A biochemical, pathophysiological, and pharmacological analysis. Surg Neurol Int 2024; 15:171. [PMID: 38840623 PMCID: PMC11152537 DOI: 10.25259/sni_296_2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2024] [Accepted: 04/19/2024] [Indexed: 06/07/2024] Open
Abstract
Much has been learned about the neurotoxicity of aluminum over the past several decades in terms of its ability to disrupt cellular function, result in slow accumulation, and the difficulty of its removal from cells. Newer evidence suggests a central pathophysiological mechanism may be responsible for much of the toxicity of aluminum and aluminofluoride compounds on the brain and spinal cord. This mechanism involves activation of the brain's innate immune system, primarily the microglia, astrocytes, and macrophages, with a release of neurotoxic concentrations of excitotoxins and proinflammatory cytokines, chemokines, and immune mediators. Many studies suggest that excitotoxicity plays a significant role in the neurotoxic action of several metals, including aluminum. Recently, researchers have found that while most of the chronic pathology involved in the observed neurodegenerative effects of these metals are secondary to prolonged inflammation, it is the enhancement of excitotoxicity by the immune mediators that are responsible for most of the metal's toxicity. This enhancement occurs through a crosstalk between cytokines and glutamate-related mechanisms. The author coined the name immunoexcitotoxicity to describe this process. This paper reviews the evidence linking immunoexcitotoxicity to aluminum's neurotoxic effects and that a slow accumulation of aluminum may be the cause of neurodevelopmental defects as well as neurodegeneration in the adult.
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Affiliation(s)
- Russell L. Blaylock
- Theoretical Neuroscience Research, LLC, Ridgeland, Mississippi, United States
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2
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Kim YS, Lee CJ, Kim JH, Kim YB, Colwell CS, Kim YI. Activation of mGluR1 negatively modulates glutamate-induced phase shifts of the circadian pacemaker in the mouse suprachiasmatic nucleus. Neurobiol Sleep Circadian Rhythms 2023; 14:100089. [PMID: 36874931 PMCID: PMC9982032 DOI: 10.1016/j.nbscr.2023.100089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 01/25/2023] [Accepted: 02/16/2023] [Indexed: 02/22/2023] Open
Abstract
In mammals, photic information delivered to the suprachiasmatic nucleus (SCN) via the retinohypothalamic tract (RHT) plays a crucial role in synchronizing the master circadian clock located in the SCN to the solar cycle. It is well known that glutamate released from the RHT terminals initiates the synchronizing process by activating ionotropic glutamate receptors (iGluRs) on retinorecipient SCN neurons. The potential role of metabotropic glutamate receptors (mGluRs) in modulating this signaling pathway has received less attention. In this study, using extracellular single-unit recordings in mouse SCN slices, we investigated the possible roles of the Gq/11 protein-coupled mGluRs, mGluR1 and mGluR5, in photic resetting. We found that mGluR1 activation in the early night produced phase advances in neural activity rhythms in the SCN, while activation in the late night produced phase delays. In contrast, mGluR5 activation had no significant effect on the phase of these rhythms. Interestingly, mGluR1 activation antagonized phase shifts induced by glutamate through a mechanism that was dependent upon CaV1.3 L-type voltage-gated Ca2+ channels (VGCCs). While both mGluR1-evoked phase delays and advances were inhibited by knockout (KO) of CaV1.3 L-type VGCCs, different signaling pathways appeared to be involved in mediating these effects, with mGluR1 working via protein kinase G in the early night and via protein kinase A signaling in the late night. We conclude that, in the mouse SCN, mGluR1s function to negatively modulate glutamate-evoked phase shifts.
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Affiliation(s)
- Yoon Sik Kim
- Department of Physiology and Neuroscience Research Institute, Korea University College of Medicine, Seoul, 136-705, Republic of Korea
| | - C Justin Lee
- Center for Cognition and Sociality, Institute for Basic Science (IBS), Daejeon, Republic of Korea
| | - Ji-Hyeon Kim
- Department of Physiology and Neuroscience Research Institute, Korea University College of Medicine, Seoul, 136-705, Republic of Korea
| | - Young-Beom Kim
- Department of Physiology and Neuroscience Research Institute, Korea University College of Medicine, Seoul, 136-705, Republic of Korea
| | - Christopher S Colwell
- Department of Psychiatry & Biobehavioral Sciences, University of California-Los Angeles, 760 Westwood Plaza, Los Angeles, CA, 90024, USA
| | - Yang In Kim
- Department of Physiology and Neuroscience Research Institute, Korea University College of Medicine, Seoul, 136-705, Republic of Korea
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Ma J, Hu Z, Yue H, Luo Y, Wang C, Wu X, Gu Y, Wang L. GRM2 Regulates Functional Integration of Adult-Born DGCs by Paradoxically Modulating MEK/ERK1/2 Pathway. J Neurosci 2023; 43:2822-2836. [PMID: 36878727 PMCID: PMC10124958 DOI: 10.1523/jneurosci.1886-22.2023] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 02/01/2023] [Accepted: 02/19/2023] [Indexed: 03/08/2023] Open
Abstract
Metabotropic glutamate receptor 2 (GRM2) is highly expressed in hippocampal dentate granule cells (DGCs), regulating synaptic transmission and hippocampal functions. Newborn DGCs are continuously generated throughout life and express GRM2 when they are mature. However, it remained unclear whether and how GRM2 regulates the development and integration of these newborn neurons. We discovered that the expression of GRM2 in adult-born DGCs increased with neuronal development in mice of both sexes. Lack of GRM2 caused developmental defects of DGCs and impaired hippocampus-dependent cognitive functions. Intriguingly, our data showed that knockdown of Grm2 resulted in decreased b/c-Raf kinases and paradoxically led to an excessive activation of MEK/ERK1/2 pathway. Inhibition of MEK ameliorated the developmental defects caused by Grm2 knockdown. Together, our results indicate that GRM2 is necessary for the development and functional integration of newborn DGCs in the adult hippocampus through regulating the phosphorylation and activation state of MEK/ERK1/2 pathway.SIGNIFICANCE STATEMENT Metabotropic glutamate receptor 2 (GRM2) is highly expressed in mature dentate granule cells (DGCs) in the hippocampus. It remains unclear whether GRM2 is required for the development and integration of adult-born DGCs. We provided in vivo and in vitro evidence to show that GRM2 regulates the development of adult-born DGCs and their integration into existing hippocampal circuits. Lack of GRM2 in a cohort of newborn DGCs impaired object-to-location memory in mice. Moreover, we revealed that GRM2 knockdown paradoxically upregulated MEK/ERK1/2 pathway by suppressing b/c-Raf in developing neurons, which is likely a common mechanism underlying the regulation of the development of neurons expressing GRM2. Thus, Raf/MEK/ERK1/2 pathway could be a potential target for brain diseases related to GRM2 abnormality.
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Affiliation(s)
- Jiao Ma
- Department of Neurology of the First Affiliated Hospital, Interdisciplinary Institute of Neuroscience and Technology, Zhejiang University School of Medicine, 310027 Hangzhou, People's Republic of China
- Center of Stem Cell and Regenerative Medicine, and Department of Neurology of the Second Affiliated Hospital, NHC and CAMS Key Laboratory of Medical Neurobiology, Zhejiang University School of Medicine, 310058 Hangzhou, People's Republic of China
| | - Zhechun Hu
- School of Brain Science and Brain Medicine, Zhejiang University, 310058 Hangzhou, People's Republic of China
| | - Huimin Yue
- Department of Neurology of the First Affiliated Hospital, Interdisciplinary Institute of Neuroscience and Technology, Zhejiang University School of Medicine, 310027 Hangzhou, People's Republic of China
- School of Brain Science and Brain Medicine, Zhejiang University, 310058 Hangzhou, People's Republic of China
| | - Yujian Luo
- Department of Neurology of the First Affiliated Hospital, Interdisciplinary Institute of Neuroscience and Technology, Zhejiang University School of Medicine, 310027 Hangzhou, People's Republic of China
- School of Brain Science and Brain Medicine, Zhejiang University, 310058 Hangzhou, People's Republic of China
| | - Chao Wang
- School of Brain Science and Brain Medicine, Zhejiang University, 310058 Hangzhou, People's Republic of China
| | - Xuan Wu
- Center of Stem Cell and Regenerative Medicine, and Department of Neurology of the Second Affiliated Hospital, NHC and CAMS Key Laboratory of Medical Neurobiology, Zhejiang University School of Medicine, 310058 Hangzhou, People's Republic of China
| | - Yan Gu
- Center of Stem Cell and Regenerative Medicine, and Department of Neurology of the Second Affiliated Hospital, NHC and CAMS Key Laboratory of Medical Neurobiology, Zhejiang University School of Medicine, 310058 Hangzhou, People's Republic of China
- MOE Frontier Science Center for Brain Science and Brain-Machine Integration, Zhejiang University, 310058 Hangzhou, People's Republic of China
| | - Lang Wang
- Department of Neurology of the First Affiliated Hospital, Interdisciplinary Institute of Neuroscience and Technology, Zhejiang University School of Medicine, 310027 Hangzhou, People's Republic of China
- School of Brain Science and Brain Medicine, Zhejiang University, 310058 Hangzhou, People's Republic of China
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Brymer KJ, Hurley EP, Barron JC, Mukherjee B, Barnes JR, Nafar F, Parsons MP. Asymmetric dysregulation of glutamate dynamics across the synaptic cleft in a mouse model of Alzheimer's disease. Acta Neuropathol Commun 2023; 11:27. [PMID: 36788598 PMCID: PMC9926626 DOI: 10.1186/s40478-023-01524-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Accepted: 01/28/2023] [Indexed: 02/16/2023] Open
Abstract
Most research on glutamate spillover focuses on the deleterious consequences of postsynaptic glutamate receptor overactivation. However, two decades ago, it was noted that the glial coverage of hippocampal synapses is asymmetric: astrocytic coverage of postsynaptic sites exceeds coverage of presynaptic sites by a factor of four. The fundamental relevance of this glial asymmetry remains poorly understood. Here, we used the glutamate biosensor iGluSnFR, and restricted its expression to either CA3 or CA1 neurons to visualize glutamate dynamics at pre- and postsynaptic microenvironments, respectively. We demonstrate that inhibition of the primarily astrocytic glutamate transporter-1 (GLT-1) slows glutamate clearance to a greater extent at presynaptic compared to postsynaptic membranes. GLT-1 expression was reduced early in a mouse model of AD, resulting in slower glutamate clearance rates at presynaptic but not postsynaptic membranes that opposed presynaptic short-term plasticity. Overall, our data demonstrate that the presynapse is particularly vulnerable to GLT-1 dysfunction and may have implications for presynaptic impairments in a variety of brain diseases.
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Affiliation(s)
- Kyle J. Brymer
- grid.25055.370000 0000 9130 6822Division of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, NL A1B 3V6 Canada
| | - Emily P. Hurley
- grid.25055.370000 0000 9130 6822Division of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, NL A1B 3V6 Canada
| | - Jessica C. Barron
- grid.25055.370000 0000 9130 6822Division of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, NL A1B 3V6 Canada
| | - Bandhan Mukherjee
- grid.25055.370000 0000 9130 6822Division of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, NL A1B 3V6 Canada
| | - Jocelyn R. Barnes
- grid.25055.370000 0000 9130 6822Division of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, NL A1B 3V6 Canada
| | - Firoozeh Nafar
- grid.25055.370000 0000 9130 6822Division of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, NL A1B 3V6 Canada
| | - Matthew P. Parsons
- grid.25055.370000 0000 9130 6822Division of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, NL A1B 3V6 Canada
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5
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Yang S, Datta D, Elizabeth Woo, Duque A, Morozov YM, Arellano J, Slusher BS, Wang M, Arnsten AFT. Inhibition of glutamate-carboxypeptidase-II in dorsolateral prefrontal cortex: potential therapeutic target for neuroinflammatory cognitive disorders. Mol Psychiatry 2022; 27:4252-4263. [PMID: 35732693 PMCID: PMC9718677 DOI: 10.1038/s41380-022-01656-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2022] [Accepted: 05/27/2022] [Indexed: 02/07/2023]
Abstract
Glutamate carboxypeptidase-II (GCPII) expression in brain is increased by inflammation, e.g. by COVID19 infection, where it reduces NAAG stimulation of metabotropic glutamate receptor type 3 (mGluR3). GCPII-mGluR3 signaling is increasingly linked to higher cognition, as genetic alterations that weaken mGluR3 or increase GCPII signaling are associated with impaired cognition in humans. Recent evidence from macaque dorsolateral prefrontal cortex (dlPFC) shows that mGluR3 are expressed on dendritic spines, where they regulate cAMP-PKA opening of potassium (K+) channels to enhance neuronal firing during working memory. However, little is known about GCPII expression and function in the primate dlPFC, despite its relevance to inflammatory disorders. The present study used multiple label immunofluorescence and immunoelectron microscopy to localize GCPII in aging macaque dlPFC, and examined the effects of GCPII inhibition on dlPFC neuronal physiology and working memory function. GCPII was observed in astrocytes as expected, but also on neurons, including extensive expression in dendritic spines. Recordings in dlPFC from aged monkeys performing a working memory task found that iontophoresis of the GCPII inhibitors 2-MPPA or 2-PMPA markedly increased working memory-related neuronal firing and spatial tuning, enhancing neural representations. These beneficial effects were reversed by an mGluR2/3 antagonist, or by a cAMP-PKA activator, consistent with mGluR3 inhibition of cAMP-PKA-K+ channel signaling. Systemic administration of the brain penetrant inhibitor, 2-MPPA, significantly improved working memory performance without apparent side effects, with largest effects in the oldest monkeys. Taken together, these data endorse GCPII inhibition as a potential strategy for treating cognitive disorders associated with aging and/or neuroinflammation.
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Affiliation(s)
- Shengtao Yang
- grid.47100.320000000419368710Department Neuroscience, Yale University School of Medicine, New Haven, CT USA
| | - Dibyadeep Datta
- grid.47100.320000000419368710Department Neuroscience, Yale University School of Medicine, New Haven, CT USA ,grid.47100.320000000419368710Department Psychiatry, Yale University School of Medicine, New Haven, CT USA
| | - Elizabeth Woo
- grid.47100.320000000419368710Department Neuroscience, Yale University School of Medicine, New Haven, CT USA
| | - Alvaro Duque
- grid.47100.320000000419368710Department Neuroscience, Yale University School of Medicine, New Haven, CT USA
| | - Yury M. Morozov
- grid.47100.320000000419368710Department Neuroscience, Yale University School of Medicine, New Haven, CT USA
| | - Jon Arellano
- grid.47100.320000000419368710Department Neuroscience, Yale University School of Medicine, New Haven, CT USA
| | - Barbara S. Slusher
- grid.21107.350000 0001 2171 9311Department Neurology and Johns Hopkins Drug Discovery, Johns Hopkins School of Medicine, Baltimore, MD USA
| | - Min Wang
- grid.47100.320000000419368710Department Neuroscience, Yale University School of Medicine, New Haven, CT USA
| | - Amy F. T. Arnsten
- grid.47100.320000000419368710Department Neuroscience, Yale University School of Medicine, New Haven, CT USA
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6
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Neurogenetics of dynamic connectivity patterns associated with obsessive-compulsive symptoms in healthy children. BIOLOGICAL PSYCHIATRY GLOBAL OPEN SCIENCE 2021; 2:411-420. [DOI: 10.1016/j.bpsgos.2021.11.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Revised: 10/28/2021] [Accepted: 11/14/2021] [Indexed: 01/31/2023] Open
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7
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Cachope R, Pereda AE. Regulatory Roles of Metabotropic Glutamate Receptors on Synaptic Communication Mediated by Gap Junctions. Neuroscience 2020; 456:85-94. [PMID: 32619474 DOI: 10.1016/j.neuroscience.2020.06.034] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2020] [Revised: 06/19/2020] [Accepted: 06/22/2020] [Indexed: 12/18/2022]
Abstract
Variations of synaptic strength are thought to underlie forms of learning and can functionally reshape neural circuits. Metabotropic glutamate receptors play key roles in regulating the strength of chemical synapses. However, information within neural circuits is also conveyed via a second modality of transmission: gap junction-mediated synapses. We review here evidence indicating that metabotropic glutamate receptors also play important roles in the regulation of synaptic communication mediated by neuronal gap junctions, also known as 'electrical synapses'. Activity-driven interactions between metabotropic glutamate receptors and neuronal gap junctions can lead to long-term changes in the strength of electrical synapses. Further, the regulatory action of metabotropic glutamate receptors on neuronal gap junctions is not restricted to adulthood but is also of critical relevance during brain development and contributes to the pathological mechanisms that follow brain injury.
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Affiliation(s)
- Roger Cachope
- CHDI Foundation, USA; Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Alberto E Pereda
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY, USA.
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8
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Griego E, Galván EJ. Metabotropic Glutamate Receptors at the Aged Mossy Fiber - CA3 Synapse of the Hippocampus. Neuroscience 2020; 456:95-105. [PMID: 31917351 DOI: 10.1016/j.neuroscience.2019.12.016] [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: 08/02/2019] [Revised: 12/06/2019] [Accepted: 12/09/2019] [Indexed: 12/28/2022]
Abstract
Metabotropic glutamate receptors (mGluRs) are a group of G-protein-coupled receptors that exert a broad array of modulatory actions at excitatory synapses of the central nervous system. In the hippocampus, the selective activation of the different mGluRs modulates the intrinsic excitability, the strength of synaptic transmission, and induces multiple forms of long-term plasticity. Despite the relevance of mGluRs in the normal function of the hippocampus, we know very little about the changes that mGluRs functionality undergoes during the non-pathological aging. Here, we review data concerning the physiological actions of mGluRs, with particular emphasis on hippocampal area CA3. Later, we examine changes in the expression and functionality of mGluRs during the aging process. We complement this review with original data showing an array of electrophysiological modifications observed in the synaptic transmission and intrinsic excitability of aged CA3 pyramidal cells in response to the pharmacological stimulation of the different mGluRs.
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Affiliation(s)
- Ernesto Griego
- Departamento de Farmacobiología, Cinvestav Sede Sur, México City, Mexico
| | - Emilio J Galván
- Departamento de Farmacobiología, Cinvestav Sede Sur, México City, Mexico.
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9
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Unchanged type 1 metabotropic glutamate receptor availability in patients with Alzheimer's disease: A study using 11C-ITMM positron emission tomography. NEUROIMAGE-CLINICAL 2019; 22:101783. [PMID: 30909027 PMCID: PMC6434168 DOI: 10.1016/j.nicl.2019.101783] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 03/04/2019] [Accepted: 03/16/2019] [Indexed: 01/06/2023]
Abstract
Imaging of type 1 metabotropic glutamate receptor (mGluR1) has recently become possible using positron emission tomography (PET). To date, little evidence exists on the role of mGluR1 in the pathophysiology of Alzheimer's disease (AD). We aimed to examine mGluR1 availability in patients with AD. Ten patients with AD (78.9 ± 5.9 years) and 12 age-matched volunteers (74.6 ± 2.6 years) underwent PET using an mGluR1 radiotracer. All patients were anti-dementia drug-naive. Volumes-of-interest were placed on the anterior and posterior lobes and vermis in the cerebellum and frontal, parietal, and temporal cortices. The binding potential (BPND) was calculated to estimate mGluR1 availability, and partial volume correction was applied to the BPND values. Mini Mental State Examination (MMSE) scores were also obtained (22.0 ± 4.8). No significant difference was observed in BPND between the AD and control groups in the anterior lobe (p = .30), posterior lobe (p = .95), vermis (p = .96), frontal cortex (p = .61), parietal cortex (p = .59), or temporal cortex (p = .27). No significant correlation was observed between BPND and MMSE scores in the anterior lobe (p = .59), posterior lobe (p = .35), vermis (p = .92), frontal cortex (p = .78), parietal cortex (p = .83), or temporal cortex (p = .82). In conclusions, this study suggests that mGluR1 availability is unchanged in the relatively early stage of AD. However, because regional mGluR1 availability may change with the progression of AD, further longitudinal follow-up is necessary. Metabotropic glutamate receptors (mGluR) can be affected in AD. Little evidence exists on the role of type 1 mGluR (mGluR1) in AD. We examined mGluR1 availability in patients with AD. mGluR1 availability was unchanged in the relatively early stage of AD.
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10
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Senter RK, Ghoshal A, Walker AG, Xiang Z, Niswender CM, Conn PJ. The Role of mGlu Receptors in Hippocampal Plasticity Deficits in Neurological and Psychiatric Disorders: Implications for Allosteric Modulators as Novel Therapeutic Strategies. Curr Neuropharmacol 2017; 14:455-73. [PMID: 27296640 PMCID: PMC4983746 DOI: 10.2174/1570159x13666150421003225] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Revised: 03/18/2015] [Accepted: 04/09/2015] [Indexed: 11/22/2022] Open
Abstract
Long-term potentiation (LTP) and long-term depression (LTD) are two distinct forms of synaptic plasticity that have been extensively characterized at the Schaffer collateral-CA1 (SCCA1) synapse and the mossy fiber (MF)-CA3 synapse within the hippocampus, and are postulated to be the molecular underpinning for several cognitive functions. Deficits in LTP and LTD have been implicated in the pathophysiology of several neurological and psychiatric disorders. Therefore, there has been a large effort focused on developing an understanding of the mechanisms underlying these forms of plasticity and novel therapeutic strategies that improve or rescue these plasticity deficits. Among many other targets, the metabotropic glutamate (mGlu) receptors show promise as novel therapeutic candidates for the treatment of these disorders. Among the eight distinct mGlu receptor subtypes (mGlu1-8), the mGlu1,2,3,5,7 subtypes are expressed throughout the hippocampus and have been shown to play important roles in the regulation of synaptic plasticity in this brain area. However, development of therapeutic agents that target these mGlu receptors has been hampered by a lack of subtype-selective compounds. Recently, discovery of allosteric modulators of mGlu receptors has provided novel ligands that are highly selective for individual mGlu receptor subtypes. The mGlu receptors modulate the multiple forms of synaptic plasticity at both SC-CA1 and MF synapses and allosteric modulators of mGlu receptors have emerged as potential therapeutic agents that may rescue plasticity deficits and improve cognitive function in patients suffering from multiple neurological and psychiatric disorders.
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Affiliation(s)
| | | | | | | | | | - P Jeffrey Conn
- Department of Pharmacology, Faculty of Vanderbilt University Medical Center, 1205 Light Hall, Nashville, TN 37232, USA.
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11
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Ganay T, Asraf H, Aizenman E, Bogdanovic M, Sekler I, Hershfinkel M. Regulation of neuronal pH by the metabotropic Zn(2+)-sensing Gq-coupled receptor, mZnR/GPR39. J Neurochem 2015; 135:897-907. [PMID: 26375174 DOI: 10.1111/jnc.13367] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2015] [Revised: 09/01/2015] [Accepted: 09/08/2015] [Indexed: 11/29/2022]
Abstract
Synaptically released Zn(2+) acts as a neurotransmitter, in part, by activating the postsynaptic metabotropic Zn(2+)-sensing Gq protein-coupled receptor (mZnR/GPR39). In previous work using epithelial cells, we described crosstalk between Zn(2+) signaling and changes in intracellular pH and/or extracellular pH (pHe). As pH changes accompany neuronal activity under physiological and pathological conditions, we tested whether Zn(2+) signaling is involved in regulation of neuronal pH. Here, we report that up-regulation of a major H(+) extrusion pathway, the Na(+)/H(+) exchanger (NHE), is induced by mZnR/GPR39 activation in an extracellular-regulated kinase 1/2-dependent manner in hippocampal neurons in vitro. We also observed that changes in pHe can modulate neuronal mZnR/GPR39-dependent signaling, resulting in reduced activity at pHe 8 or 6.5. Similarly, Zn(2+)-dependent extracellular-regulated kinase 1/2 phosphorylation and up-regulation of NHE activity were absent at acidic pHe. Thus, our results suggest that when pHe is maintained within the physiological range, mZnR/GPR39 activation can up-regulate NHE-dependent recovery from intracellular acidification. During acidosis, as pHe drops, mZnR/GPR39-dependent NHE activation is inhibited, thereby attenuating further H(+) extrusion. This mechanism may serve to protect neurons from excessive decreases in pHe. Thus, mZnR/GPR39 signaling provides a homeostatic adaptive process for regulation of intracellular and extracellular pH changes in the brain. We show that the postsynaptic metabotropic Zn(2+)-sensing Gq protein-coupled receptor (mZnR/GPR39) activation induces up-regulation of a major neuronal H(+) extrusion pathway, the Na(+)/H(+) exchanger (NHE), thereby enhancing neuronal recovery from intracellular acidification. Changes in extracellular pH (pHe), however, modulate neuronal mZnR/GPR39-dependent signaling, resulting in reduced activity at pHe 8 or 6.5. This mechanism may serve to protect neurons from excessive decreases in pHe during acidosis. Hence, mZnR/GPR39 signaling provides a homeostatic adaptive process for regulation of intracellular and extracellular pH changes in the brain.
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Affiliation(s)
- Thibault Ganay
- Department of Physiology and Cell Biology and The Zlotowski Center of Neuroscience, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Hila Asraf
- Department of Physiology and Cell Biology and The Zlotowski Center of Neuroscience, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Elias Aizenman
- Department of Physiology and Cell Biology and The Zlotowski Center of Neuroscience, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.,Department of Neurobiology and Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Milos Bogdanovic
- Department of Physiology and Cell Biology and The Zlotowski Center of Neuroscience, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Israel Sekler
- Department of Physiology and Cell Biology and The Zlotowski Center of Neuroscience, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Michal Hershfinkel
- Department of Physiology and Cell Biology and The Zlotowski Center of Neuroscience, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
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Majewski L, Kuznicki J. SOCE in neurons: Signaling or just refilling? BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:1940-52. [DOI: 10.1016/j.bbamcr.2015.01.019] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2014] [Revised: 01/22/2015] [Accepted: 01/26/2015] [Indexed: 01/14/2023]
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13
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mGlu5 acts as a switch for opposing forms of synaptic plasticity at mossy fiber-CA3 and commissural associational-CA3 synapses. J Neurosci 2015; 35:4999-5006. [PMID: 25810529 DOI: 10.1523/jneurosci.3417-14.2015] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Within the hippocampus, different kinds of spatial experience determine the direction of change of synaptic weights. Synaptic plasticity resulting from such experience may enable memory encoding. The CA3 region is very striking in this regard: due to the distinct molecular properties of the mossy fiber (MF) and associational-commissural (AC) synapses, it is believed that they enable working memory and pattern completion. The question arises, however, as to how information reaching these synapses results in differentiated encoding. Given its crucial role in enabling persistent synaptic plasticity in other hippocampal subfields, we speculated that the metabotropic glutamate receptor mGlu5 may regulate information encoding at MF and AC synapses. Here, we show that antagonism of mGlu5 inhibits LTP, but not LTD at MF synapses of freely behaving adult rats. Conversely, mGlu5 antagonism prevents LTD but not LTP at AC-CA3 synapses. This suggests that, under conditions in which mGlu5 is activated, LTP may be preferentially induced at MF synapses, whereas LTD is favored at AC synapses. To assess this possibility, we applied 50 Hz stimulation that should generate postsynaptic activity that corresponds to θm, the activation threshold that lies between LTP and LTD. MGlu5 activation had no effect on AC responses but potentiated MF synapses. These data suggest that mGlu5 serves as a switch that alters signal-to-noise ratios during information encoding in the CA3 region. This mechanism supports highly tuned and differentiated information storage in CA3 synapses.
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Arkhipov V, Kapralova M, Pershina E, Gordon R. Delayed treatments with pharmacological modulators of pre- and postsynaptic mGlu receptors rescue the hippocampus from kainate-induced neurodegeneration. Neurosci Lett 2014; 570:5-9. [PMID: 24747688 DOI: 10.1016/j.neulet.2014.04.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2013] [Revised: 04/01/2014] [Accepted: 04/09/2014] [Indexed: 11/18/2022]
Abstract
Gene expression of mGluR2, mGluR3 and mGluR5 was evaluated in the hippocampus and frontal cortex in Wistar rats in 1 and 4 weeks after bilateral microinjection of kainic acid into the dorsal hippocampus. The time-course of the receptors' expression suggested their adaptive role in response on the induction of excitotoxicity. It was assumed that the decrease of kainate-induced neurodegeneration could be achieved through simultaneous activation of presynaptic mGluRs and inhibition of mGlu postsynaptic receptors. Both negative allosteric modulator of mGluR5, MPEP, and agonist of mGluR2, LY354740, were administered intraperitoneally 5 days after microinjection of kainic acid. As shown by histochemical studies with cresyl violet and Fluoro-Jade, kainate induced significant damage of hippocampal neurons in the CA3 and CA1 fields. Pharmacological treatment with the negative modulator of mGlu5 receptors in common with the agonist of mGluR2 decreased kainate-induced neurodegeneration in dorsal hippocampus.
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Affiliation(s)
- Vladimir Arkhipov
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Russian Federation.
| | - Marina Kapralova
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Russian Federation
| | - Ekaterina Pershina
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Russian Federation; Pushchino State Institute of Natural Sciences, Russian Federation
| | - Rita Gordon
- Institute of Cell Biophysics, Russian Academy of Sciences, Russian Federation
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15
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Arkhipov VI, Kapralova MV. Expression of Metabotropic Glutamate Receptors after Hippocampal Injury. Bull Exp Biol Med 2014; 156:457-60. [DOI: 10.1007/s10517-014-2373-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Indexed: 10/25/2022]
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16
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Gipson CD, Kupchik YM, Kalivas PW. Rapid, transient synaptic plasticity in addiction. Neuropharmacology 2014; 76 Pt B:276-86. [PMID: 23639436 PMCID: PMC3762905 DOI: 10.1016/j.neuropharm.2013.04.032] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Revised: 04/10/2013] [Accepted: 04/16/2013] [Indexed: 12/20/2022]
Abstract
Chronic use of addictive drugs produces enduring neuroadaptations in the corticostriatal glutamatergic brain circuitry. The nucleus accumbens (NAc), which integrates cortical information and regulates goal-directed behavior, undergoes long-term morphological and electrophysiological changes that may underlie the increased susceptibility for relapse in drug-experienced individuals even after long periods of withdrawal. Additionally, it has recently been shown that exposure to cues associated with drug use elicits rapid and transient morphological and electrophysiological changes in glutamatergic synapses in the NAc. This review highlights these dynamic drug-induced changes in this pathway that are specific to a drug seeking neuropathology, as well as how these changes impair normal information processing and thereby contribute to the uncontrollable motivation to relapse. Future directions for relapse prevention and pharmacotherapeutic targeting of the rapid, transient synaptic plasticity in relapse are discussed. This article is part of a Special Issue entitled 'NIDA 40th Anniversary Issue'.
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Affiliation(s)
- Cassandra D Gipson
- Department of Neurosciences, Medical University of South Carolina, 173 Ashley Ave., BSB 403, Charleston, SC 29425, USA.
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17
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Ostapchenko VG, Beraldo FH, Guimarães ALS, Mishra S, Guzman M, Fan J, Martins VR, Prado VF, Prado MAM. Increased prion protein processing and expression of metabotropic glutamate receptor 1 in a mouse model of Alzheimer's disease. J Neurochem 2013; 127:415-25. [PMID: 23651058 DOI: 10.1111/jnc.12296] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2012] [Revised: 04/29/2013] [Accepted: 05/02/2013] [Indexed: 12/14/2022]
Abstract
Prion protein (PrP(C) ), a glycosylphosphatidylinositol-anchored protein corrupted in prion diseases, has been shown recently to interact with group I metabotropic glutamate receptors (mGluRs). Moreover, both PrP(C) and mGluRs were proposed to function as putative receptors for β-amyloid in Alzheimer's disease. PrP(C) can be processed in neurons via α or β-cleavage to produce PrP(C) fragments that are neuroprotective or toxic, respectively. We found PrP(C) α-cleavage to be 2-3 times higher in the cortex of APPswe/PS1dE9 mice, a mouse model of Alzheimer's disease. A similar age-dependent increase was observed for PrP(C) β-cleavage. Moreover, we observed considerable age-dependent increase in cortical expression of mGluR1, but not mGluR5. Exposure of cortical neuronal cultures to β-amyloid oligomers upregulated mGluR1 and PrP(C) α-cleavage, while activation of group I mGluRs increased PrP(C) shedding from the membrane, likely due to increased levels of a disintegrin and metalloprotease10, a key disintegrin for PrP(C) shedding. Interestingly, a similar increase in a disintegrin and metalloprotease10 was detected in the cortex of 9-month-old APPswe/PS1dE9 animals. Our experiments reveal novel and complex processing of PrP(C) in connection with mGluR overexpression that seems to be triggered by β-amyloid peptides. Prion protein (PrP(C) ) and metabotropic glutamate receptors (mGluR) are implicated in Alzheimer's disease (AD). We found age-dependent increase in PrP(C) processing, ADAM10 and mGluR1 levels in AD mouse model. These changes could be reproduced in cultured cortical neurons treated with Aβ peptide. Our findings suggest that increased levels of Aβ can trigger compensatory responses that may affect neuronal toxicity.
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Affiliation(s)
- Valeriy G Ostapchenko
- Robarts Research Institute, Department of Physiology and Pharmacology, University of Western Ontario, London, ON, Canada
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18
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Sandiego CM, Nabulsi N, Lin SF, Labaree D, Najafzadeh S, Huang Y, Cosgrove K, Carson RE. Studies of the metabotropic glutamate receptor 5 radioligand [¹¹C]ABP688 with N-acetylcysteine challenge in rhesus monkeys. Synapse 2013; 67:489-501. [PMID: 23424090 DOI: 10.1002/syn.21656] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Accepted: 02/12/2013] [Indexed: 02/05/2023]
Abstract
Detecting changes in receptor binding at the metabotropic glutamate receptor 5 (mGluR5) with the PET allosteric antagonist, [¹¹C]ABP688, may be valuable for studying dysfunctional glutamate transmission associated with psychiatric illnesses. This study was designed to validate the findings of a recent pilot study in baboons which reported a significant global decrease from baseline [¹¹C]ABP688 binding after increasing endogenous glutamate with 50 mg/kg N-acetylcysteine (NAC), with no change from test to retest. In rhesus monkeys (n = 5), paired [¹¹C]ABP688 scans were performed on the same day on the Focus-220 as follows (n = 3 per group): test-retest, baseline-NAC (50 mg/kg), and baseline-NAC (100 mg/kg). Multiple modeling methods were evaluated for kinetic analysis to estimate the total volume of distribution (VT ) and non-displaceable binding potential (BP(ND)) in regions-of-interest (ROIs), with the cerebellum gray matter (CGM) as the reference region. There was an increasing trend from test to retest BP(ND) across ROIs (13%). NAC (50 mg/kg and 100 mg/kg) increased VT (5% and 19%) and decreased BP(ND) (3% and 10%), respectively, significant only for VT in ROIs at the 100 mg/kg dose. High intersubject variability in BP(ND) was comparable to that reported in the baboon study. However, interpretability of BP(ND) is difficult with increases in VT in the CGM reference region at the higher NAC dose. Additionally, the net reduction in BP(ND) from the baseline-NAC scans may be obscured due to observed increases in test-retest BP(ND). Thus, we did not strictly replicate the findings in the baboon study based on BP(ND).
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Affiliation(s)
- Christine M Sandiego
- Department of Biomedical Engineering, Yale University, New Haven, Connecticut 06520, USA.
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Torres-Torrelo J, Rodríguez-Rosell D, Nunez-Abades P, Carrascal L, Torres B. Glutamate modulates the firing rate in oculomotor nucleus motoneurons as a function of the recruitment threshold current. J Physiol 2012; 590:3113-27. [PMID: 22570384 DOI: 10.1113/jphysiol.2011.226985] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Studies in alert preparations have demonstrated that ocular motoneurons exhibit a phasic–tonic firing rate related to eye velocity and position, respectively. The slopes of these relationships are higher in motoneurons with higher recruitment threshold and have been proposed to depend upon synaptic input. To investigate this hypothesis, motoneurons of the rat oculomotor nucleus were recorded in a brain slice preparation in control conditions and during glutamate (5 μm) application to the bath. Glutamate did not affect membrane potential or input resistance, but produced a decrease in rheobase and depolarization voltage as a function of the current needed for generating a maintained repetitive discharge (recruitment threshold current). In addition, glutamate compressed the range of recruitment threshold current (0.1–0.4 nA) as compared to the control (0.15–0.7 nA). Glutamate exposed motoneurons showed an increase in the tonic frequency gain and the peak frequency. Such increments depended on the recruitment threshold current and the last recruited motoneurons almost doubled the tonic frequency gain (35.2 vs. 57.9 spikes s(−1) nA(−1)) and the peak frequency (52.4 vs. 102.6 spikes s(−1)). Finally, glutamate increased the spike frequency adaptation due to a significant increase in the phasic firing component as compared to the tonic one. In conclusion, glutamate modulates tonic and phasic discharge properties as a function of the recruitment threshold current and, presumably, motoneuron size. These findings contribute to understand the link between cellular functions and motoneuron discharge during oculomotor behaviour.
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Haynes LP, McCue HV, Burgoyne RD. Evolution and functional diversity of the Calcium Binding Proteins (CaBPs). Front Mol Neurosci 2012; 5:9. [PMID: 22375103 PMCID: PMC3284769 DOI: 10.3389/fnmol.2012.00009] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2012] [Accepted: 01/25/2012] [Indexed: 02/01/2023] Open
Abstract
The mammalian central nervous system (CNS) exhibits a remarkable ability to process, store, and transfer information. Key to these activities is the use of highly regulated and unique patterns of calcium signals encoded by calcium channels and decoded by families of specific calcium-sensing proteins. The largest family of eukaryotic calcium sensors is those related to the small EF-hand containing protein calmodulin (CaM). In order to maximize the usefulness of calcium as a signaling species and to permit the evolution and fine tuning of the mammalian CNS, families of related proteins have arisen that exhibit characteristic calcium binding properties and tissue-, cellular-, and sub-cellular distribution profiles. The Calcium Binding Proteins (CaBPs) represent one such family of vertebrate specific CaM like proteins that have emerged in recent years as important regulators of essential neuronal target proteins. Bioinformatic analyses indicate that the CaBPs consist of two subfamilies and that the ancestral members of these are CaBP1 and CaBP8. The CaBPs have distinct intracellular localizations based on different targeting mechanisms including a novel type-II transmembrane domain in CaBPs 7 and 8 (otherwise known as calneuron II and calneuron I, respectively). Recent work has led to the identification of new target interactions and possible functions for the CaBPs suggesting that they have multiple physiological roles with relevance for the normal functioning of the CNS.
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Affiliation(s)
- Lee P Haynes
- The Physiological Laboratory, Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool Liverpool, UK
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