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Abdel-Ghani M, Lee Y, Akli LA, Moran M, Schneeweis A, Djemil S, ElChoueiry R, Murtadha R, Pak DTS. Plk2 promotes synaptic destabilization through disruption of N-cadherin adhesion complexes during homeostatic adaptation to hyperexcitation. J Neurochem 2023; 167:362-375. [PMID: 37654026 PMCID: PMC10592368 DOI: 10.1111/jnc.15948] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Revised: 07/20/2023] [Accepted: 08/12/2023] [Indexed: 09/02/2023]
Abstract
Synaptogenesis in the brain is highly organized and orchestrated by synaptic cellular adhesion molecules (CAMs) such as N-cadherin and amyloid precursor protein (APP) that contribute to the stabilization and structure of synapses. Although N-cadherin plays an integral role in synapse formation and synaptic plasticity, its function in synapse dismantling is not as well understood. Synapse weakening and loss are prominent features of neurodegenerative diseases, and can also be observed during homeostatic compensation to neuronal hyperexcitation. Previously, we have shown that during homeostatic synaptic plasticity, APP is a target for cleavage triggered by phosphorylation by Polo-like kinase 2 (Plk2). Here, we found that Plk2 directly phosphorylates N-cadherin, and during neuronal hyperexcitation Plk2 promotes N-cadherin proteolytic processing, degradation, and disruption of complexes with APP. We further examined the molecular mechanisms underlying N-cadherin degradation. Loss of N-cadherin adhesive function destabilizes excitatory synapses and promotes their structural dismantling as a prerequisite to eventual synapse elimination. This pathway, which may normally help to homeostatically restrain excitability, could also shed light on the dysregulated synapse loss that occurs in cognitive disorders.
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Affiliation(s)
- Mai Abdel-Ghani
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC 20057, USA
| | - Yeunkum Lee
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC 20057, USA
| | - Lyna Ait Akli
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC 20057, USA
| | - Marielena Moran
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC 20057, USA
| | - Amanda Schneeweis
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC 20057, USA
| | - Sarra Djemil
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC 20057, USA
| | - Rebecca ElChoueiry
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC 20057, USA
| | - Ruqaya Murtadha
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC 20057, USA
| | - Daniel T. S. Pak
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC 20057, USA
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2
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Wang Y, Liu Y, Bi X, Baudry M. Calpain-1 and Calpain-2 in the Brain: New Evidence for a Critical Role of Calpain-2 in Neuronal Death. Cells 2020; 9:E2698. [PMID: 33339205 PMCID: PMC7765587 DOI: 10.3390/cells9122698] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 12/08/2020] [Accepted: 12/14/2020] [Indexed: 01/24/2023] Open
Abstract
Calpains are a family of soluble calcium-dependent proteases that are involved in multiple regulatory pathways. Our laboratory has focused on the understanding of the functions of two ubiquitous calpain isoforms, calpain-1 and calpain-2, in the brain. Results obtained over the last 30 years led to the remarkable conclusion that these two calpain isoforms exhibit opposite functions in the brain. Calpain-1 activation is required for certain forms of synaptic plasticity and corresponding types of learning and memory, while calpain-2 activation limits the extent of plasticity and learning. Calpain-1 is neuroprotective both during postnatal development and in adulthood, while calpain-2 is neurodegenerative. Several key protein targets participating in these opposite functions have been identified and linked to known pathways involved in synaptic plasticity and neuroprotection/neurodegeneration. We have proposed the hypothesis that the existence of different PDZ (PSD-95, DLG and ZO-1) binding domains in the C-terminal of calpain-1 and calpain-2 is responsible for their association with different signaling pathways and thereby their different functions. Results with calpain-2 knock-out mice or with mice treated with a selective calpain-2 inhibitor indicate that calpain-2 is a potential therapeutic target in various forms of neurodegeneration, including traumatic brain injury and repeated concussions.
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Affiliation(s)
- Yubin Wang
- Graduate College of Biomedical Sciences, Western University of Health Sciences, Pomona, CA 91766, USA; (Y.W.); (Y.L.)
| | - Yan Liu
- Graduate College of Biomedical Sciences, Western University of Health Sciences, Pomona, CA 91766, USA; (Y.W.); (Y.L.)
| | - Xiaoning Bi
- College of Osteopathic Medicine of the Pacific, Western University of Health Sciences, Pomona, CA 91766, USA;
| | - Michel Baudry
- Graduate College of Biomedical Sciences, Western University of Health Sciences, Pomona, CA 91766, USA; (Y.W.); (Y.L.)
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Rodzli NA, Lockhart-Cairns MP, Levy CW, Chipperfield J, Bird L, Baldock C, Prince SM. The Dual PDZ Domain from Postsynaptic Density Protein 95 Forms a Scaffold with Peptide Ligand. Biophys J 2020; 119:667-689. [PMID: 32652058 PMCID: PMC7399497 DOI: 10.1016/j.bpj.2020.06.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 06/11/2020] [Accepted: 06/16/2020] [Indexed: 01/29/2023] Open
Abstract
PSD-95 is a member of the membrane-associated guanylate kinase class of proteins that forms scaffolding interactions with partner proteins, including ion and receptor channels. PSD-95 is directly implicated in modulating the electrical responses of excitable cells. The first two PSD-95/disks large/zona occludens (PDZ) domains of PSD-95 have been shown to be the key component in the formation of channel clusters. We report crystal structures of this dual domain in both apo- and ligand-bound form: thermodynamic analysis of the ligand association and small-angle x-ray scattering of the dual domain in the absence and presence of ligands. These experiments reveal that the ligated double domain forms a three-dimensional scaffold that can be described by a space group. The concentration of the components in this study is comparable with those found in compartments of excitable cells such as the postsynaptic density and juxtaparanodes of Ranvier. These in vitro experiments inform the basis of the scaffolding function of PSD-95 and provide a detailed model for scaffold formation by the PDZ domains of PSD-95.
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Affiliation(s)
- Nazahiyah A Rodzli
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester, United Kingdom
| | - Michael P Lockhart-Cairns
- Wellcome Centre for Cell-Matrix Research, Division of Cell-Matrix Biology and Regenerative Medicine, Manchester Academic Health Science Centre, Manchester, United Kingdom
| | - Colin W Levy
- Manchester Protein Structure Facility, Manchester Institute of Biotechnology, University of Manchester, Manchester, United Kingdom
| | - John Chipperfield
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester, United Kingdom
| | - Louise Bird
- Oxford Protein Production Facility, Wellcome Trust Centre for Human Genetics, Headington, Oxford, United Kingdom
| | - Clair Baldock
- Wellcome Centre for Cell-Matrix Research, Division of Cell-Matrix Biology and Regenerative Medicine, Manchester Academic Health Science Centre, Manchester, United Kingdom
| | - Stephen M Prince
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester, United Kingdom.
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Kula B, Chen T, Kukley M. Glutamatergic signaling between neurons and oligodendrocyte lineage cells: Is it synaptic or non‐synaptic? Glia 2019; 67:2071-2091. [DOI: 10.1002/glia.23617] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 03/12/2019] [Accepted: 03/18/2019] [Indexed: 12/18/2022]
Affiliation(s)
- Bartosz Kula
- Group of Neuron Glia InteractionUniversity of Tübingen Tübingen Germany
- Graduate Training Centre for NeuroscienceUniversity of Tübingen Tübingen Germany
| | - Ting‐Jiun Chen
- Center for Neuroscience ResearchChildren's Research Institute, Children's National Medical Center Washington District of Columbia
| | - Maria Kukley
- Group of Neuron Glia InteractionUniversity of Tübingen Tübingen Germany
- Research Institute for OphthalmologyUniversity Hospital Tübingen Tübingen Germany
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5
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Abou-El-Hassan H, Sukhon F, Assaf EJ, Bahmad H, Abou-Abbass H, Jourdi H, Kobeissy FH. Degradomics in Neurotrauma: Profiling Traumatic Brain Injury. Methods Mol Biol 2017; 1598:65-99. [PMID: 28508358 DOI: 10.1007/978-1-4939-6952-4_4] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Degradomics has recently emerged as a subdiscipline in the omics era with a focus on characterizing signature breakdown products implicated in various disease processes. Driven by promising experimental findings in cancer, neuroscience, and metabolomic disorders, degradomics has significantly promoted the notion of disease-specific "degradome." A degradome arises from the activation of several proteases that target specific substrates and generate signature protein fragments. Several proteases such as calpains, caspases, cathepsins, and matrix metalloproteinases (MMPs) are involved in the pathogenesis of numerous diseases that disturb the physiologic balance between protein synthesis and protein degradation. While regulated proteolytic activities are needed for development, growth, and regeneration, uncontrolled proteolysis initiated under pathological conditions ultimately culminates into apoptotic and necrotic processes. In this chapter, we aim to review the protease-substrate repertoires in neural injury concentrating on traumatic brain injury. A striking diversity of protease substrates, essential for neuronal and brain structural and functional integrity, namely, encryptic biomarker neoproteins, have been characterized in brain injury. These include cytoskeletal proteins, transcription factors, cell cycle regulatory proteins, synaptic proteins, and cell junction proteins. As these substrates are subject to proteolytic fragmentation, they are ceaselessly exposed to activated proteases. Characterization of these molecules allows for a surge of "possible" therapeutic approaches of intervention at various levels of the proteolytic cascade.
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Affiliation(s)
- Hadi Abou-El-Hassan
- Faculty of Medicine, American University of Beirut Medical Center, Beirut, Lebanon.
| | - Fares Sukhon
- Faculty of Medicine, Department of Internal Medicine, American University of Beirut Medical Center, Beirut, Lebanon
| | - Edwyn Jeremy Assaf
- Faculty of Medicine, American University of Beirut Medical Center, Beirut, Lebanon
| | - Hisham Bahmad
- Faculty of Medical, Neuroscience Research Center, Beirut Arab University, Beirut, Lebanon
- Faculty of Medicine, Department of Anatomy, Cell Biology and Physiological Sciences, American University of Beirut, Beirut, Lebanon
| | - Hussein Abou-Abbass
- Faculty of Medical Sciences, Neuroscience Research Center, Lebanese University, Beirut, Lebanon
- Faculty of Medicine, Department of Biochemistry and Molecular Genetics, American University of Beirut, Beirut, Lebanon
| | - Hussam Jourdi
- Faculty of Science¸ Department of Biology, University of Balamand, Souk-el-Gharb Campus, Aley, Lebanon
| | - Firas H Kobeissy
- Faculty of Medicine, Department of Biochemistry and Molecular Genetics, American University of Beirut, Beirut, Lebanon.
- Department of Psychiatry, Center for Neuroproteomics and Biomarkers Research, University of Florida, Gainesville, FL, USA.
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Curcio M, Salazar IL, Mele M, Canzoniero LMT, Duarte CB. Calpains and neuronal damage in the ischemic brain: The swiss knife in synaptic injury. Prog Neurobiol 2016; 143:1-35. [PMID: 27283248 DOI: 10.1016/j.pneurobio.2016.06.001] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Revised: 03/22/2016] [Accepted: 05/09/2016] [Indexed: 12/26/2022]
Abstract
The excessive extracellular accumulation of glutamate in the ischemic brain leads to an overactivation of glutamate receptors with consequent excitotoxic neuronal death. Neuronal demise is largely due to a sustained activation of NMDA receptors for glutamate, with a consequent increase in the intracellular Ca(2+) concentration and activation of calcium- dependent mechanisms. Calpains are a group of Ca(2+)-dependent proteases that truncate specific proteins, and some of the cleavage products remain in the cell, although with a distinct function. Numerous studies have shown pre- and post-synaptic effects of calpains on glutamatergic and GABAergic synapses, targeting membrane- associated proteins as well as intracellular proteins. The resulting changes in the presynaptic proteome alter neurotransmitter release, while the cleavage of postsynaptic proteins affects directly or indirectly the activity of neurotransmitter receptors and downstream mechanisms. These alterations also disturb the balance between excitatory and inhibitory neurotransmission in the brain, with an impact in neuronal demise. In this review we discuss the evidence pointing to a role for calpains in the dysregulation of excitatory and inhibitory synapses in brain ischemia, at the pre- and post-synaptic levels, as well as the functional consequences. Although targeting calpain-dependent mechanisms may constitute a good therapeutic approach for stroke, specific strategies should be developed to avoid non-specific effects given the important regulatory role played by these proteases under normal physiological conditions.
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Affiliation(s)
- Michele Curcio
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Ivan L Salazar
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal; Doctoral Programme in Experimental Biology and Biomedicine, Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal; Institute for Interdisciplinary Research, University of Coimbra (IIIUC), 3030-789 Coimbra, Portugal
| | - Miranda Mele
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
| | | | - Carlos B Duarte
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal; Department of Life Sciences, University of Coimbra, 3000-456 Coimbra, Portugal.
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7
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Calpain-1 and Calpain-2: The Yin and Yang of Synaptic Plasticity and Neurodegeneration. Trends Neurosci 2016; 39:235-245. [PMID: 26874794 DOI: 10.1016/j.tins.2016.01.007] [Citation(s) in RCA: 168] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Revised: 01/20/2016] [Accepted: 01/21/2016] [Indexed: 01/09/2023]
Abstract
Many signaling pathways participate in both synaptic plasticity and neuronal degeneration. While calpains participate in these phenomena, very few studies have evaluated the respective roles of the two major calpain isoforms in the brain, calpain-1 and calpain-2. We review recent studies indicating that calpain-1 and calpain-2 exhibit opposite functions in both synaptic plasticity and neurodegeneration. Calpain-1 activation is required for the induction of long-term potentiation (LTP) and is generally neuroprotective, while calpain-2 activation limits the extent of potentiation and is neurodegenerative. This duality of functions is related to their associations with different PDZ-binding proteins, resulting in differential subcellular localization, and offers new therapeutic opportunities for a number of indications in which these proteases have previously been implicated.
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8
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Hossain S, Liu HN, Fragoso G, Almazan G. Agonist-induced down-regulation of AMPA receptors in oligodendrocyte progenitors. Neuropharmacology 2014; 79:506-14. [PMID: 24412648 DOI: 10.1016/j.neuropharm.2013.12.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Revised: 12/09/2013] [Accepted: 12/23/2013] [Indexed: 10/25/2022]
Abstract
Prolonged exposure of oligodendrocyte progenitor cultures to non-toxic concentrations of glutamate receptor agonists for 24 h decreased cellular proliferation mediated by α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. Since prolonged agonist stimulation can regulate the expression of various families of receptors, we examined this possibility. Pretreatment of progenitor cultures with 100 μM kainic acid (KA) for 1-24 h caused a time-dependent decrease in AMPA receptor activity, determined by agonist-induced (45)Ca(2+) uptake. The maximum effect (70-80% decrease), observed in the 24 h-pretreated cells, was accompanied by a significant reduction in AMPA receptor subunits, as determined by Western blotting. GluR2/3 and GluR4 subunits were the most affected. Receptor down-regulation and (45)Ca(2+) uptake were only partially reversible upon KA removal. Furthermore, 24 h co-treatment of cultures with CNQX blocked the KA-induced decreases in calcium uptake. To address whether calpain, a calcium-activated protease, was implicated in the regulation of the AMPA receptor subunits, cultures were treated with the specific inhibitor PD150606 alone or in combination with KA for 24 h. Calpain inhibition significantly increased GluR1 in both conditions and partly reversed downregulation of GluR4 by KA. Collectively, these results indicate that calpain is not involved in the agonist-induced down-regulation of AMPA receptors subunits 2/3 in oligodendrocyte progenitors, while it downregulates GluR1 and GluR4.
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Affiliation(s)
- Shireen Hossain
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada
| | - Hsueh-Ning Liu
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada
| | - Gabriela Fragoso
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada
| | - Guillermina Almazan
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada.
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9
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Jourdi H, Kabbaj M. Acute BDNF treatment upregulates GluR1-SAP97 and GluR2-GRIP1 interactions: implications for sustained AMPA receptor expression. PLoS One 2013; 8:e57124. [PMID: 23460828 PMCID: PMC3584105 DOI: 10.1371/journal.pone.0057124] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Accepted: 01/17/2013] [Indexed: 12/23/2022] Open
Abstract
Brain-derived neurotrophic factor (BDNF) plays several prominent roles in synaptic plasticity and in learning and memory formation. Reduced BDNF levels and altered BDNF signaling have been reported in several brain diseases and behavioral disorders, which also exhibit reduced levels of AMPAr subunits. BDNF treatment acutely regulates AMPA receptor expression and function, including synaptic AMPAr subunit trafficking, and implicates several well defined signaling molecules that are required to elicit long term potentiation and depression (LTP and LTD, respectively). Long term encoding of synaptic events, as in long term memory formation, requires AMPAr stabilization and maintenance. However, factors regulating AMPAr stabilization in neuronal cell membranes and synaptic sites are not well characterized. In this study, we examine the effects of acute BDNF treatment on levels of AMPAr-associated scaffolding proteins and on AMPAr subunit-scaffolding protein interactions. We also examine the effects of BDNF-dependent enhanced interactions between AMPAr subunits with their specific scaffolding proteins on the accumulation of both types of proteins. Our results show that acute BDNF treatment upregulates the interactions between AMPAr subunits (GluR1 and GluR2) with their scaffold proteins SAP97 and GRIP1, respectively, leading to prolonged increased accumulation of both categories of proteins, albeit with distinct mechanisms for GluR1 and GluR2. Our findings reveal a new role for BDNF in the long term maintenance of AMPA receptor subunits and associated scaffolding proteins at synapses and further support the role of BDNF as a key regulator of synaptic consolidation. These results have potential implications for recent findings implicating BDNF and AMPAr subunits in various brain diseases and behavioral disorders.
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Affiliation(s)
- Hussam Jourdi
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, Florida, United States of America.
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10
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Abstract
INTRODUCTION Calpains represent a family of neutral, calcium-dependent proteases, which modify the function of their target proteins by partial truncation. These proteases have been implicated in numerous cell functions, including cell division, proliferation, migration, and death. In the CNS, where µ-calpain and m-calpain are the main calpain isoforms, their activation has been linked to synaptic plasticity as well as to neurodegeneration. This review will focus on the role of calpains in synaptic plasticity and discuss the possibility of developing methods to manipulate calpain activity for therapeutic purposes. AREAS COVERED This review covers the literature showing how calpains are implicated in synaptic plasticity and in a number of conditions associated with learning impairment. The possibility of developing new drugs targeting these enzymes for treating these conditions is discussed. EXPERT OPINION As evidence accumulates that calpain activation participates in neurodegeneration and cancer, there is interest in developing therapeutic approaches using direct or indirect calpain inhibition. In particular, a peptide derived from the calpain truncation site of mGluR1α was shown to decrease neurodegeneration following neonatal hypoxia/ischemia. More selective approaches need to be developed to target calpain or some of its substrates for therapeutic indications associated with deregulation of synaptic plasticity.
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Affiliation(s)
- Michel Baudry
- Western University of Health Sciences, Graduate College of Biomedical Sciences, Basic Medical Sciences, COMP , 309 E 2nd St, Pomona, CA 91766, USA.
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11
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Abstract
The glial cell line-derived neurotrophic factor (GDNF) was first identified as a survival factor for midbrain dopaminergic neurons, but additional studies provided evidences for a role as a trophic factor for other neurons of the central and peripheral nervous systems. GDNF regulates cellular activity through interaction with glycosyl-phosphatidylinositol-anchored cell surface receptors, GDNF family receptor-α1, which might signal through the transmembrane Ret tyrosine receptors or the neural cell adhesion molecule, to promote cell survival, neurite outgrowth, and synaptogenesis. The neuroprotective effect of exogenous GDNF has been shown in different experimental models of focal and global brain ischemia, by local administration of the trophic factor, using viral vectors carrying the GDNF gene and by transplantation of GDNF-expressing cells. These different strategies and the mechanisms contributing to neuroprotection by GDNF are discussed in this review. Importantly, neuroprotection by GDNF was observed even when administered after the ischemic injury.
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Affiliation(s)
- Emília P Duarte
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Largo Marquês de Pombal, Coimbra, Portugal
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12
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Morgan TE, Davis DA, Iwata N, Tanner JA, Snyder D, Ning Z, Kam W, Hsu YT, Winkler JW, Chen JC, Petasis NA, Baudry M, Sioutas C, Finch CE. Glutamatergic neurons in rodent models respond to nanoscale particulate urban air pollutants in vivo and in vitro. ENVIRONMENTAL HEALTH PERSPECTIVES 2011; 119:1003-9. [PMID: 21724521 PMCID: PMC3222976 DOI: 10.1289/ehp.1002973] [Citation(s) in RCA: 147] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2010] [Accepted: 03/29/2011] [Indexed: 05/06/2023]
Abstract
BACKGROUND Inhalation of airborne particulate matter (PM) derived from urban traffic is associated with pathology in the arteries, heart, and lung; effects on brain are also indicated but are less documented. OBJECTIVE We evaluated rodent brain responses to urban nanoscale (< 200 nm) PM (nPM). METHODS Ambient nPM collected near an urban freeway was transferred to aqueous suspension and reaerosolized for 10-week inhalation exposure of mice or directly applied to rat brain cell cultures. RESULTS Free radicals were detected by electron paramagnetic resonance in the nPM 30 days after initial collection. Chronic inhalation of reaerosolized nPM altered selected neuronal and glial activities in mice. The neuronal glutamate receptor subunit (GluA1) was decreased in hippocampus, whereas glia were activated and inflammatory cytokines were induced [interleukin-1α (IL-1α), tumor necrosis factor-α (TNFα)] in cerebral cortex. Two in vitro models showed effects of nPM suspensions within 24-48 hr of exposure that involved glutamatergic functions. In hippocampal slice cultures, nPM increased the neurotoxicity of NMDA (N-methyl-d-aspartic acid), a glutamatergic agonist, which was in turn blocked by the NMDA antagonist AP5 [(2R)-amino-5-phosphonopentanoate]. In embryonic neuron cultures, nPM impaired neurite outgrowth, also blocked by AP5. Induction of IL-1α and TNFα in mixed glia cultures required higher nPM concentrations than did neuronal effects. Because conditioned media from nPM-exposed glia also impaired outgrowth of embryonic neurites, nPM can act indirectly, as well as directly, on neurons in vitro. CONCLUSIONS nPM can affect embryonic and adult neurons through glutamatergic mechanisms. The interactions of nPM with glutamatergic neuronal functions suggest that cerebral ischemia, which involves glutamatergic excitotoxicity, could be exacerbated by nPM.
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Affiliation(s)
- Todd E Morgan
- Davis School of Gerontology, University of Southern California, Los Angeles, California 90089, USA
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Cleavage of the vesicular GABA transporter under excitotoxic conditions is followed by accumulation of the truncated transporter in nonsynaptic sites. J Neurosci 2011; 31:4622-35. [PMID: 21430162 DOI: 10.1523/jneurosci.3541-10.2011] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
GABA is the major inhibitory neurotransmitter in the CNS and changes in GABAergic neurotransmission affect the overall activity of neuronal networks. The uptake of GABA into synaptic vesicles is mediated by the vesicular GABA transporter (VGAT), and changes in the expression of the transporter directly regulate neurotransmitter release. In this work we investigated the changes in VGAT protein levels during ischemia and in excitotoxic conditions, which may affect the demise process. We found that VGAT is cleaved by calpains following excitotoxic stimulation of hippocampal neurons with glutamate, giving rise to a stable truncated cleavage product (tVGAT). VGAT cleavage was also observed after transient middle cerebral artery occlusion in mice, a cerebral ischemia model, and following intrahippocampal injection of kainate, but no effect was observed in transgenic mice overexpressing calpastatin, a calpain inhibitor. Incubation of isolated cerebrocortical synaptic vesicles with recombinant calpain also induced the cleavage of VGAT and formation of stable tVGAT. Immunoblot experiments using antibodies targeting different regions of VGAT and N-terminal sequencing analysis showed that calpain cleaves the transporter in the N-terminal region, at amino acids 52 and 60. Immunocytochemistry of GABAergic striatal neurons expressing GFP fusion proteins with the full-length VGAT or tVGAT showed that cleavage of the transporter induces a loss of synaptic delivery, leading to a homogeneous distribution of the protein along neurites. Our results show that excitotoxicity downregulates full-length VGAT, with a concomitant generation of tVGAT, which is likely to affect GABAergic neurotransmission and may influence cell death during ischemia.
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14
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Crish SD, Calkins DJ. Neurodegeneration in glaucoma: progression and calcium-dependent intracellular mechanisms. Neuroscience 2010; 176:1-11. [PMID: 21187126 DOI: 10.1016/j.neuroscience.2010.12.036] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2010] [Revised: 12/16/2010] [Accepted: 12/18/2010] [Indexed: 01/18/2023]
Abstract
Glaucoma is an age-related optic neuropathy involving sensitivity to ocular pressure. The disease is now seen increasingly as one of the central nervous system, as powerful new approaches highlight an increasing number of similarities with other age-related neurodegenerations such as Alzheimer's and Parkinson's. While the etiologies of these diseases are diverse, they involve many important common elements including compartmentalized programs of degeneration targeting axons, dendrites and finally cell bodies. Most age-related degenerations display early functional deficits that precede actual loss of neuronal substrate. These are linked to several specific neurochemical cascades that can be linked back to dysregulation of Ca(2+)-dependent processes. We are now in the midst of identifying similar cascades in glaucoma. Here we review recent evidence on the pathological progression of neurodegeneration in glaucoma and some of the Ca(2+)-dependent mechanisms that could underlie these changes. These mechanisms present clear implications for efforts to develop interventions targeting neuronal loss directly and make glaucoma an attractive model for both interrogating and informing other neurodegenerative diseases.
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Affiliation(s)
- S D Crish
- Department of Pharmaceutical Sciences, Northeastern Ohio Universities Colleges of Medicine and Pharmacy, Rootstown, OH 44272, USA
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15
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Diesel exhaust particles modulate vascular endothelial cell permeability: implication of ZO-1 expression. Toxicol Lett 2010; 197:163-8. [PMID: 20576493 DOI: 10.1016/j.toxlet.2010.05.017] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2010] [Revised: 05/18/2010] [Accepted: 05/20/2010] [Indexed: 01/06/2023]
Abstract
Exposure to air pollutants increases the incidence of cardiovascular disease. Recent toxicity studies revealed that ultra-fine particles (UFP, d(p)<100-200 nm), the major portion of particulate matter (PM) by numbers in the atmosphere, induced atherosclerosis. In this study, we posited that variations in chemical composition in diesel exhausted particles (DEP) regulated endothelial cell permeability to a different extent. Human aortic endothelial cells (HAEC) were exposed to well-characterized DEP (d(p)<100 nm) emitted from a diesel engine in either idling mode (DEP1) or in urban dynamometer driving schedule (UDDS) (DEP2). Horse Radish Peroxidase-Streptavidin activity assay showed that DEP2 increased endothelial permeability to a greater extent than DEP1 (control=0.077+/-0.005, DEP1=0.175+/-0.003, DEP2=0.265+/-0.006, n=3, p<0.01). DEP2 also down-regulated tight junction protein, Zonular Occludin-1 (ZO-1), to a greater extent compared to DEP1. LDH and caspase-3 activities revealed that DEP-mediated increase in permeability was not due to direct cytotoxicity, and DEP-mediated ZO-1 down-regulation was not due to a decrease in ZO-1 mRNA. Hence, our findings suggest that DEP1 vs. DEP2 differentially influenced the extent of endothelial permeability at the post-translational level. This increase in endothelium permeability is implicated in inflammatory cell transmigration into subendothelial layers with relevance to the initiation of atherosclerosis.
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Jourdi H, Hamo L, Oka T, Seegan A, Baudry M. BDNF mediates the neuroprotective effects of positive AMPA receptor modulators against MPP+-induced toxicity in cultured hippocampal and mesencephalic slices. Neuropharmacology 2009; 56:876-85. [PMID: 19371576 DOI: 10.1016/j.neuropharm.2009.01.015] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2008] [Revised: 12/24/2008] [Accepted: 01/13/2009] [Indexed: 01/08/2023]
Abstract
Neurotoxicity is involved in various neurodegenerative diseases including Parkinson's disease (PD), which affects mesencephalic dopaminergic neurons of the substantia nigra (SN). Positive alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor modulators (PARMs, a.k.a. Ampakines, such as CX614) increase brain-derived neurotrophic factor (BDNF) protein levels in vivo and in cultured hippocampal slices. BDNF is a survival factor for various neuronal cell types including mesencephalic dopaminergic neurons. Using cultured mesencephalic and hippocampal slices, we investigated whether preincubation with CX614 could provide neuroprotection against MPP(+) toxicity and whether such neuroprotection was mediated by BDNF. Various treatment protocols were tested to demonstrate CX614-induced neuroprotection against MPP(+). Pretreatment with CX614 significantly reduced MPP(+)-induced toxicity and increased BDNF levels in both hippocampal and mesencephalic cultured slices; CX614 pretreatment for 6 h in hippocampal slices and 24 h in mesencephalic slices was sufficient to produce significant neuroprotection as assessed with lactate dehydrogenase release in slice medium and propidium iodide uptake in slices. Both a BDNF scavenger and an inhibitor of the BDNF receptor TrkB, abrogated CX614-mediated reduction of MPP(+)-induced toxicity. Inhibition of Ca(2+)-activated proteases, calpains, was also protective against MPP(+)-induced toxicity. However, co-application of calpain inhibitor with CX614 abolished CX614-mediated protection, suggesting a dual action of calpains in this model. We conclude that CX614 is neuroprotective against MPP(+)-induced toxicity, an effect mediated by increased BDNF expression and activation of BDNF-dependent signaling pathways. Our results provide support for using PARMs as a new therapy for neurodegenerative disorders, including PD.
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Affiliation(s)
- H Jourdi
- Neurobiology, University of Southern California, 3641 Watt way, Los Angeles, CA 90089-2520, USA
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Lauterborn JC, Pineda E, Chen LY, Ramirez EA, Lynch G, Gall CM. Ampakines cause sustained increases in brain-derived neurotrophic factor signaling at excitatory synapses without changes in AMPA receptor subunit expression. Neuroscience 2008; 159:283-95. [PMID: 19141314 DOI: 10.1016/j.neuroscience.2008.12.018] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2008] [Revised: 11/27/2008] [Accepted: 11/06/2008] [Indexed: 12/25/2022]
Abstract
Recent demonstrations that positive modulators of AMPA-type glutamate receptors (ampakines) increase neuronal brain-derived neurotrophic factor (BDNF) expression have suggested a novel strategy for treating neurodegenerative diseases. However, reports that AMPA and BDNF receptors are down-regulated by prolonged activation raise concerns about the extent to which activity-induced increases in BDNF levels can be sustained without compromising glutamate receptor function. The present study constitutes an initial test of whether ampakines can cause enduring increases in BDNF content and signaling without affecting AMPA receptor (AMPAR) expression. Prolonged (12-24 h) treatment with the ampakine CX614 reduced AMPAR subunit (glutamate receptor subunit (GluR) 1-3) mRNA and protein levels in cultured rat hippocampal slices whereas treatment with AMPAR antagonists had the opposite effects. The cholinergic agonist carbachol also depressed GluR1-3 mRNA levels, suggesting that AMPAR down-regulation is a global response to extended periods of elevated neuronal activity. Analyses of time courses and thresholds indicated that BDNF expression is influenced by lower doses of, and shorter treatments with, the ampakine than is AMPAR expression. Accordingly, daily 3 h infusions of CX614 chronically elevated BDNF content with no effect on GluR1-3 concentrations. Restorative deconvolution microscopy provided the first evidence that chronic up-regulation of BDNF is accompanied by increased activation of the neurotrophin's TrkB-Fc receptor at spine synapses. These results show that changes in BDNF and AMPAR expression are dissociable and that up-regulation of the former leads to enhanced trophic signaling at excitatory synapses. These findings are encouraging with regard to the feasibility of using ampakines to tonically enhance BDNF-dependent functions in adult brain.
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Affiliation(s)
- J C Lauterborn
- Department of Anatomy and Neurobiology, Gillespie Neuroscience Research Facility (Room 3119), 837 Health Science Drive, University of California at Irvine, Irvine, CA 92697-4291, USA
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18
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Abstract
The calpain family of proteases is causally linked to postischemic neurodegeneration. However, the precise mechanisms by which calpains contribute to postischemic neuronal death have not been fully elucidated. This review outlines the key features of the calpain system, and the evidence for its causal role in postischemic neuronal pathology. Furthermore, the consequences of specific calpain substrate cleavage at various subcellular locations are explored. Calpain substrates within synapses, plasma membrane, endoplasmic reticulum, lysosomes, mitochondria, and the nucleus, as well as the overall effect of postischemic calpain activity on calcium regulation and cell death signaling are considered. Finally, potential pathways for calpain-mediated neurodegeneration are outlined in an effort to guide future studies aimed at understanding the downstream pathology of postischemic calpain activity and identifying optimal therapeutic strategies.
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Affiliation(s)
- Matthew B Bevers
- Department of Emergency Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-4283, USA
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Keith D, El-Husseini A. Excitation Control: Balancing PSD-95 Function at the Synapse. Front Mol Neurosci 2008; 1:4. [PMID: 18946537 PMCID: PMC2526002 DOI: 10.3389/neuro.02.004.2008] [Citation(s) in RCA: 145] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2008] [Accepted: 01/30/2008] [Indexed: 01/12/2023] Open
Abstract
Excitability of individual neurons dictates the overall excitation in specific brain circuits. This process is thought to be regulated by molecules that regulate synapse number, morphology and strength. Neuronal excitation is also influenced by the amounts of neurotransmitter receptors and signaling molecules retained at particular synaptic sites. Recent studies revealed a key role for PSD-95, a scaffolding molecule enriched at glutamatergic synapses, in modulation of clustering of several neurotransmitter receptors, adhesion molecules, ion channels, cytoskeletal elements and signaling molecules at postsynaptic sites. In this review we will highlight mechanisms that control targeting of PSD-95 at the synapse, and discuss how this molecule influences the retention and clustering of diverse synaptic proteins to regulate synaptic structure and strength. We will also discuss how PSD-95 may maintain a balance between excitation and inhibition in the brain and how alterations in this balance may contribute to neuropsychiatric disorders.
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Affiliation(s)
- Dove Keith
- Department of Psychiatry and the Brain Research Centre, University of British Columbia Vancouver, BC, Canada
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Keith D, El-Husseini A. Excitation Control: Balancing PSD-95 Function at the Synapse. Front Mol Neurosci 2008; 1:4. [PMID: 18946537 DOI: 10.3389/neuro.02.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2008] [Accepted: 01/30/2008] [Indexed: 05/19/2023] Open
Abstract
Excitability of individual neurons dictates the overall excitation in specific brain circuits. This process is thought to be regulated by molecules that regulate synapse number, morphology and strength. Neuronal excitation is also influenced by the amounts of neurotransmitter receptors and signaling molecules retained at particular synaptic sites. Recent studies revealed a key role for PSD-95, a scaffolding molecule enriched at glutamatergic synapses, in modulation of clustering of several neurotransmitter receptors, adhesion molecules, ion channels, cytoskeletal elements and signaling molecules at postsynaptic sites. In this review we will highlight mechanisms that control targeting of PSD-95 at the synapse, and discuss how this molecule influences the retention and clustering of diverse synaptic proteins to regulate synaptic structure and strength. We will also discuss how PSD-95 may maintain a balance between excitation and inhibition in the brain and how alterations in this balance may contribute to neuropsychiatric disorders.
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Affiliation(s)
- Dove Keith
- Department of Psychiatry and the Brain Research Centre, University of British Columbia Vancouver, BC, Canada
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21
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Wu HY, Lynch DR. Calpain and synaptic function. Mol Neurobiol 2007; 33:215-36. [PMID: 16954597 DOI: 10.1385/mn:33:3:215] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2005] [Revised: 11/30/1999] [Accepted: 02/20/2006] [Indexed: 01/13/2023]
Abstract
Proteolysis by calpain is a unique posttranslational modification that can change integrity, localization, and activity of endogenous proteins. Two ubiquitous calpains, mu-calpain and m-calpain, are highly expressed in the central nervous system, and calpain substrates such as membrane receptors, postsynaptic density proteins, kinases, and phosphatases are localized to the synaptic compartments of neurons. By selective cleavage of synaptically localized molecules, calpains may play pivotal roles in the regulation of synaptic processes not only in physiological states but also during various pathological conditions. Activation of calpains during sustained synaptic activity is crucial for Ca2+-dependent neuronal functions, such as neurotransmitter release, synaptic plasticity, vesicular trafficking, and structural stabilization. Overactivation of calpain following dysregulation of Ca2+ homeostasis can lead to neuronal damage in response to events such as epilepsy, stroke, and brain trauma. Calpain may also provide a neuroprotective effect from axotomy and some forms of glutamate receptor overactivation. This article focuses on recent findings on the role of calpain-mediated proteolytic processes in potentially regulating synaptic substrates in physiological and pathophysiological events in the nervous system.
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Affiliation(s)
- Hai-Yan Wu
- Department of Pediatrics, Children's Hospital of Philadelphia and the University of Pennsylvania, Philadelphia, PA, USA
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22
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Javitt DC. Glutamate and schizophrenia: phencyclidine, N-methyl-D-aspartate receptors, and dopamine-glutamate interactions. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2007; 78:69-108. [PMID: 17349858 DOI: 10.1016/s0074-7742(06)78003-5] [Citation(s) in RCA: 395] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Schizophrenia is a serious mental disorder that affects up to 1% of the population worldwide. As of yet, neurochemical mechanisms underlying schizophrenia remain unknown. To date, the most widely considered neurochemical hypothesis of schizophrenia is the dopamine hypothesis, which postulates that symptoms of schizophrenia may result from excess dopaminergic neurotransmission particularly in striatal brain regions, along with dopaminergic deficits in prefrontal brain regions. Alternative neurochemical models of schizophrenia, however, have been proposed involving glutamatergic mechanisms in general and N-methyl-D-aspartate (NMDA) receptors in particular. A potential role for glutamatergic mechanisms in schizophrenia was first proposed approximately 15 years ago based on the observation that the psychotomimetic agents phencyclidine (PCP) and ketamine induce psychotic symptoms and neurocognitive disturbances similar to those of schizophrenia by blocking neurotransmission at NMDA-type glutamate receptors. Since that time, significant additional evidence has accumulated supporting a role for NMDA hypofunction in the pathophysiology of schizophrenia. Clinical challenge studies with PCP and ketamine have confirmed the close resemblance between NMDA antagonist-induced symptoms and neurocognitive deficits and those observed in schizophrenia, and suggest that NMDA dysfunction may lead to secondary dopaminergic dysregulation in striatal and prefrontal brain regions. As compared to dopaminergic agents, NMDA antagonists induce negative and cognitive symptoms of schizophrenia, as well as positive symptoms. Treatment studies with NMDA modulators, such as glycine, d-serine, and glycine transport inhibitors (GTIs), have yielded encouraging findings, although results remain controversial. Finally, genetic linkage and in vivo neurochemical studies in schizophrenia highlight potential etiological mechanisms giving rise to glutamatergic/NMDA dysfunction in schizophrenia.
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Affiliation(s)
- Daniel C Javitt
- Program in Cognitive Neuroscience and Schizophrenia, Nathan Kline Institute for Psychiatric, Research, New York University School of Medicine, Orangeburg, New York 10962, USA
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