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Ibrahim MJ, Baiju V, Sen S, Chandran PP, Ashraf GM, Haque S, Ahmad F. Utilities of Isolated Nerve Terminals in Ex Vivo Analyses of Protein Translation in (Patho)physiological Brain States: Focus on Alzheimer's Disease. Mol Neurobiol 2024; 61:91-103. [PMID: 37582987 DOI: 10.1007/s12035-023-03562-x] [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: 06/05/2023] [Accepted: 08/07/2023] [Indexed: 08/17/2023]
Abstract
Synapses are the cellular substrates of higher-order brain functions, and their dysfunction is an early and primary pathogenic mechanism across several neurological disorders. In particular, Alzheimer's disease (AD) is categorized by prodromal structural and functional synaptic deficits, prior to the advent of classical behavioral and pathological features. Recent research has shown that the development, maintenance, and plasticity of synapses depend on localized protein translation. Synaptosomes and synaptoneurosomes are biochemically isolated synaptic terminal preparations which have long been used to examine a variety of synaptic processes ex vivo in both healthy and pathological conditions. These ex vivo preparations preserve the mRNA species and the protein translational machinery. Hence, they are excellent in organello tools for the study of alterations in mRNA levels and protein translation in neuropathologies. Evaluation of synapse-specific basal and activity-driven de novo protein translation activity can be conveniently performed in synaptosomal/synaptoneurosomal preparations from both rodent and human brain tissue samples. This review gives a quick overview of the methods for isolating synaptosomes and synaptoneurosomes before discussing the studies that have utilized these preparations to study localized synapse-specific protein translation in (patho)physiological situations, with an emphasis on AD. While the review is not an exhaustive accumulation of all the studies evaluating synaptic protein translation using the synaptosomal model, the aim is to assemble the most relevant studies that have done so. The hope is to provide a suitable research platform to aid neuroscientists to utilize the synaptosomal/synaptoneurosomal models to evaluate the molecular mechanisms of synaptic dysfunction within the specific confines of mRNA localization and protein translation research.
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Affiliation(s)
- Mohammad Jasim Ibrahim
- Department of Biotechnology, Vellore Institute of Technology, Vellore, Tamil Nadu, India, 632014
| | - Viswanath Baiju
- Department of Biotechnology, Vellore Institute of Technology, Vellore, Tamil Nadu, India, 632014
| | - Shivam Sen
- Department of Biotechnology, Vellore Institute of Technology, Vellore, Tamil Nadu, India, 632014
| | - Pranav Prathapa Chandran
- Department of Biotechnology, Vellore Institute of Technology, Vellore, Tamil Nadu, India, 632014
| | - Ghulam Md Ashraf
- University of Sharjah, College of Health Sciences, and Research Institute for Medical and Health Sciences, Department of Medical Laboratory Sciences, University City, 27272, Sharjah, United Arab Emirates.
| | - Shafiul Haque
- Research and Scientific Studies Unit, College of Nursing and Allied Health Sciences, Jazan University, 45142, Jazan, Saudi Arabia
- Gilbert and Rose-Marie Chagoury School of Medicine, Lebanese American University, Beirut, Lebanon
- Centre of Medical and Bio-Allied Health Sciences Research, Ajman University, Ajman, United Arab Emirates
| | - Faraz Ahmad
- Department of Biotechnology, Vellore Institute of Technology, Vellore, Tamil Nadu, India, 632014.
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Pinky PD, Bloemer J, Smith WD, Du Y, Heslin RT, Setti SE, Pfitzer JC, Chowdhury K, Hong H, Bhattacharya S, Dhanasekaran M, Dityatev A, Reed MN, Suppiramaniam V. Prenatal Cannabinoid Exposure Elicits Memory Deficits Associated with Reduced PSA-NCAM Expression, Altered Glutamatergic Signaling, and Adaptations in Hippocampal Synaptic Plasticity. Cells 2023; 12:2525. [PMID: 37947603 PMCID: PMC10648717 DOI: 10.3390/cells12212525] [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: 06/21/2023] [Revised: 10/02/2023] [Accepted: 10/06/2023] [Indexed: 11/12/2023] Open
Abstract
Cannabis is now one of the most commonly used illicit substances among pregnant women. This is particularly concerning since developmental exposure to cannabinoids can elicit enduring neurofunctional and cognitive alterations. This study investigates the mechanisms of learning and memory deficits resulting from prenatal cannabinoid exposure (PCE) in adolescent offspring. The synthetic cannabinoid agonist WIN55,212-2 was administered to pregnant rats, and a series of behavioral, electrophysiological, and immunochemical studies were performed to identify potential mechanisms of memory deficits in the adolescent offspring. Hippocampal-dependent memory deficits in adolescent PCE animals were associated with decreased long-term potentiation (LTP) and enhanced long-term depression (LTD) at hippocampal Schaffer collateral-CA1 synapses, as well as an imbalance between GluN2A- and GluN2B-mediated signaling. Moreover, PCE reduced gene and protein expression of neural cell adhesion molecule (NCAM) and polysialylated-NCAM (PSA-NCAM), which are critical for GluN2A and GluN2B signaling balance. Administration of exogenous PSA abrogated the LTP deficits observed in PCE animals, suggesting PSA mediated alterations in GluN2A- and GluN2B- signaling pathways may be responsible for the impaired hippocampal synaptic plasticity resulting from PCE. These findings enhance our current understanding of how PCE affects memory and how this process can be manipulated for future therapeutic purposes.
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Affiliation(s)
- Priyanka D. Pinky
- Department of Drug Discovery and Development, Auburn University, Auburn, AL 36849, USA
- Department of Biomedical Engineering, University of California Irvine, Irvine, CA 92697, USA
| | - Jenna Bloemer
- Department of Drug Discovery and Development, Auburn University, Auburn, AL 36849, USA
- Department of Pharmaceutical and Biomedical Sciences, Touro College of Pharmacy, New York, NY 10036, USA
| | - Warren D. Smith
- Department of Drug Discovery and Development, Auburn University, Auburn, AL 36849, USA
| | - Yifeng Du
- Department of Drug Discovery and Development, Auburn University, Auburn, AL 36849, USA
| | - Ryan T. Heslin
- Department of Drug Discovery and Development, Auburn University, Auburn, AL 36849, USA
| | - Sharay E. Setti
- Department of Drug Discovery and Development, Auburn University, Auburn, AL 36849, USA
| | - Jeremiah C. Pfitzer
- Department of Drug Discovery and Development, Auburn University, Auburn, AL 36849, USA
| | - Kawsar Chowdhury
- Department of Drug Discovery and Development, Auburn University, Auburn, AL 36849, USA
| | - Hao Hong
- Key Laboratory of Neuropsychiatric Diseases, Jiangsu Key Laboratory of Drug Discovery for Metabolic Diseases, and State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing 210009, China
| | - Subhrajit Bhattacharya
- Department of Drug Discovery and Development, Auburn University, Auburn, AL 36849, USA
- Center for Neuroscience Initiative, Auburn University, Auburn, AL 36849, USA
- Keck Graduate Institute, School of Pharmacy and Health Sciences, Claremont Colleges, Claremont, CA 91711, USA
| | - Muralikrishnan Dhanasekaran
- Department of Drug Discovery and Development, Auburn University, Auburn, AL 36849, USA
- Molecular Neuroplasticity, German Center for Neurodegenerative Diseases (DZNE), 37075 Magdeburg, Germany
| | - Alexander Dityatev
- Center for Neuroscience Initiative, Auburn University, Auburn, AL 36849, USA
- Molecular Neuroplasticity, German Center for Neurodegenerative Diseases (DZNE), 37075 Magdeburg, Germany
- Medical Faculty, Otto-von-Guericke University, 39106 Magdeburg, Germany
| | - Miranda N. Reed
- Department of Drug Discovery and Development, Auburn University, Auburn, AL 36849, USA
- Center for Neuroscience Initiative, Auburn University, Auburn, AL 36849, USA
| | - Vishnu Suppiramaniam
- Department of Drug Discovery and Development, Auburn University, Auburn, AL 36849, USA
- Center for Neuroscience Initiative, Auburn University, Auburn, AL 36849, USA
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Hindley N, Sanchez Avila A, Henstridge C. Bringing synapses into focus: Recent advances in synaptic imaging and mass-spectrometry for studying synaptopathy. Front Synaptic Neurosci 2023; 15:1130198. [PMID: 37008679 PMCID: PMC10050382 DOI: 10.3389/fnsyn.2023.1130198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Accepted: 02/28/2023] [Indexed: 03/17/2023] Open
Abstract
Synapses are integral for healthy brain function and are becoming increasingly recognized as key structures in the early stages of brain disease. Understanding the pathological processes driving synaptic dysfunction will unlock new therapeutic opportunities for some of the most devastating diseases of our time. To achieve this we need a solid repertoire of imaging and molecular tools to interrogate synaptic biology at greater resolution. Synapses have historically been examined in small numbers, using highly technical imaging modalities, or in bulk, using crude molecular approaches. However, recent advances in imaging techniques are allowing us to analyze large numbers of synapses, at single-synapse resolution. Furthermore, multiplexing is now achievable with some of these approaches, meaning we can examine multiple proteins at individual synapses in intact tissue. New molecular techniques now allow accurate quantification of proteins from isolated synapses. The development of increasingly sensitive mass-spectrometry equipment means we can now scan the synaptic molecular landscape almost in totality and see how this changes in disease. As we embrace these new technical developments, synapses will be viewed with clearer focus, and the field of synaptopathy will become richer with insightful and high-quality data. Here, we will discuss some of the ways in which synaptic interrogation is being facilitated by methodological advances, focusing on imaging, and mass spectrometry.
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Affiliation(s)
- Nicole Hindley
- Division of Cellular and Systems Medicine, University of Dundee, Dundee, United Kingdom
- *Correspondence: Nicole Hindley,
| | - Anna Sanchez Avila
- Division of Cellular and Systems Medicine, University of Dundee, Dundee, United Kingdom
- Euan Macdonald Centre for Motor Neuron Disease, University of Edinburgh, Edinburgh, United Kingdom
| | - Christopher Henstridge
- Division of Cellular and Systems Medicine, University of Dundee, Dundee, United Kingdom
- Euan Macdonald Centre for Motor Neuron Disease, University of Edinburgh, Edinburgh, United Kingdom
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Chu MC, Wu HF, Lee CW, Chung YJ, Chi H, Chen PS, Lin HC. Generational synaptic functions of GABA A receptor β3 subunit deteriorations in an animal model of social deficit. J Biomed Sci 2022; 29:51. [PMID: 35821032 PMCID: PMC9277936 DOI: 10.1186/s12929-022-00835-w] [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: 04/01/2022] [Accepted: 07/06/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Disruption of normal brain development is implicated in numerous psychiatric disorders with neurodevelopmental origins, including autism spectrum disorder (ASD). Widespread abnormalities in brain structure and functions caused by dysregulations of neurodevelopmental processes has been recently shown to exert adverse effects across generations. An imbalance between excitatory/inhibitory (E/I) transmission is the putative hypothesis of ASD pathogenesis, supporting by the specific implications of inhibitory γ-aminobutyric acid (GABA)ergic system in autistic individuals and animal models of ASD. However, the contribution of GABAergic system in the neuropathophysiology across generations of ASD is still unknown. Here, we uncover profound alterations in the expression and function of GABAA receptors (GABAARs) in the amygdala across generations of the VPA-induced animal model of ASD. METHODS The F2 generation was produced by mating an F1 VPA-induced male offspring with naïve females after a single injection of VPA on embryonic day (E12.5) in F0. Autism-like behaviors were assessed by animal behavior tests. Expression and functional properties of GABAARs and related proteins were examined by using western blotting and electrophysiological techniques. RESULTS Social deficit, repetitive behavior, and emotional comorbidities were demonstrated across two generations of the VPA-induced offspring. Decreased synaptic GABAAR and gephyrin levels, and inhibitory transmission were found in the amygdala from two generations of the VPA-induced offspring with greater reductions in the F2 generation. Weaker association of gephyrin with GABAAR was shown in the F2 generation than the F1 generation. Moreover, dysregulated NMDA-induced enhancements of gephyrin and GABAAR at the synapse in the VPA-induced offspring was worsened in the F2 generation than the F1 generation. Elevated glutamatergic modifications were additionally shown across generations of the VPA-induced offspring without generation difference. CONCLUSIONS Taken together, these findings revealed the E/I synaptic abnormalities in the amygdala from two generations of the VPA-induced offspring with GABAergic deteriorations in the F2 generation, suggesting a potential therapeutic role of the GABAergic system to generational pathophysiology of ASD.
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Affiliation(s)
- Ming-Chia Chu
- grid.260539.b0000 0001 2059 7017Department and Institute of Physiology, School of Medicine, National Yang Ming Chiao Tung University, Tainan, 112 Taiwan
| | - Han-Fang Wu
- grid.260539.b0000 0001 2059 7017Department and Institute of Physiology, School of Medicine, National Yang Ming Chiao Tung University, Tainan, 112 Taiwan
| | - Chi-Wei Lee
- grid.260539.b0000 0001 2059 7017Department and Institute of Physiology, School of Medicine, National Yang Ming Chiao Tung University, Tainan, 112 Taiwan
| | - Yueh-Jung Chung
- grid.260539.b0000 0001 2059 7017Department and Institute of Physiology, School of Medicine, National Yang Ming Chiao Tung University, Tainan, 112 Taiwan
| | - Hsiang Chi
- grid.260539.b0000 0001 2059 7017Department and Institute of Physiology, School of Medicine, National Yang Ming Chiao Tung University, Tainan, 112 Taiwan
| | - Po See Chen
- Department of Psychiatry, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan, 704, Taiwan. .,Institute of Behavioral Medicine, College of Medicine, National Cheng Kung University, Tainan, 704, Taiwan.
| | - Hui-Ching Lin
- Department and Institute of Physiology, School of Medicine, National Yang Ming Chiao Tung University, Taipei, 112, Taiwan. .,Ph.D. Program for Neural Regenerative Medicine, College of Medical Science and Technology, Taipei Medical University and National Health Research Institutes, Taipei, 110, Taiwan. .,Brain Research Center, National Yang Ming Chiao Tung University, Taipei, 112, Taiwan.
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Marin IA, Gutman-Wei AY, Chew KS, Raissi AJ, Djurisic M, Shatz CJ. The nonclassical MHC class I Qa-1 expressed in layer 6 neurons regulates activity-dependent plasticity via microglial CD94/NKG2 in the cortex. Proc Natl Acad Sci U S A 2022; 119:e2203965119. [PMID: 35648829 PMCID: PMC9191652 DOI: 10.1073/pnas.2203965119] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Accepted: 04/20/2022] [Indexed: 12/30/2022] Open
Abstract
During developmental critical periods, circuits are sculpted by a process of activity-dependent competition. The molecular machinery involved in regulating the complex process of responding to different levels of activity is now beginning to be identified. Here, we show that the nonclassical major histocompatibility class I (MHCI) molecule Qa-1 is expressed in the healthy brain in layer 6 corticothalamic neurons. In the visual cortex, Qa-1 expression begins during the critical period for ocular dominance (OD) plasticity and is regulated by neuronal activity, suggesting a role in regulating activity-dependent competition. Indeed, in mice lacking Qa-1, OD plasticity is perturbed. Moreover, signaling through CD94/NKG2, a known cognate Qa-1 heterodimeric receptor in the immune system, is implicated: selectively targeting this interaction phenocopies the plasticity perturbation observed in Qa-1 knockouts. In the cortex, CD94/NKG2 is expressed by microglial cells, which undergo activity-dependent changes in their morphology in a Qa-1–dependent manner. Our study thus reveals a neuron–microglial interaction dependent upon a nonclassical MHCI molecule expressed in L6 neurons, which regulates plasticity in the visual cortex. These results also point to an unexpected function for the Qa-1/HLA-E (ligand) and CD94/NKG2 (receptor) interaction in the nervous system, in addition to that described in the immune system.
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Affiliation(s)
- Ioana A. Marin
- Department of Biology, Stanford University, Stanford, CA 94035
- Department of Neurobiology, Stanford University, Stanford, CA 94035
| | - Alan Y. Gutman-Wei
- Department of Biology, Stanford University, Stanford, CA 94035
- Department of Neurobiology, Stanford University, Stanford, CA 94035
| | - Kylie S. Chew
- Department of Biology, Stanford University, Stanford, CA 94035
- Department of Neurobiology, Stanford University, Stanford, CA 94035
| | - Aram J. Raissi
- Department of Biology, Stanford University, Stanford, CA 94035
- Department of Neurobiology, Stanford University, Stanford, CA 94035
| | - Maja Djurisic
- Department of Biology, Stanford University, Stanford, CA 94035
- Department of Neurobiology, Stanford University, Stanford, CA 94035
| | - Carla J. Shatz
- Department of Biology, Stanford University, Stanford, CA 94035
- Department of Neurobiology, Stanford University, Stanford, CA 94035
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Alhowail AH, Pinky PD, Eggert M, Bloemer J, Woodie LN, Buabeid MA, Bhattacharya S, Jasper SL, Bhattacharya D, Dhanasekaran M, Escobar M, Arnold RD, Suppiramaniam V. Doxorubicin induces dysregulation of AMPA receptor and impairs hippocampal synaptic plasticity leading to learning and memory deficits. Heliyon 2021; 7:e07456. [PMID: 34296005 PMCID: PMC8282984 DOI: 10.1016/j.heliyon.2021.e07456] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 06/10/2021] [Accepted: 06/28/2021] [Indexed: 11/27/2022] Open
Abstract
Doxorubicin (Dox) is a chemotherapeutic agent used widely to treat a variety of malignant cancers. However, Dox chemotherapy is associated with several adverse effects, including "chemobrain," the observation that cancer patients exhibit through learning and memory difficulties extending even beyond treatment. This study investigated the effect of Dox treatment on learning and memory as well as hippocampal synaptic plasticity. Dox-treated mice (5 mg/kg weekly x 5) demonstrated impaired performance in the Y-maze spatial memory task and a significant reduction in hippocampal long-term potentiation. The deficit in synaptic plasticity was mirrored by deficits in the functionality of synaptic `α-amino-3- hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) channels, including reduced probability of opening, decreased dwell open time, and increased closed times. Furthermore, a reduction in the AMPAR subunit GluA1 level, its downstream signaling molecule Ca2+/calmodulin-dependent protein kinase (CaMKII), and brain-derived neurotrophic factor (BDNF) were observed. This was also accompanied by an increase in extracellular signal regulated kinase (ERK) and protein kinase B (AKT) activation. Together these data suggest that Dox-induced cognitive impairments are at least partially due to alterations in the expression and functionality of the glutamatergic AMPAR system.
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Affiliation(s)
- Ahmad H. Alhowail
- Department of Pharmacology and Toxicology, Qassim University, Buraydah, Saudi Arabia
| | - Priyanka D. Pinky
- Department of Drug Discovery and Development, Auburn University, Auburn, Alabama, USA
| | - Matthew Eggert
- Department of Drug Discovery and Development, Auburn University, Auburn, Alabama, USA
| | - Jenna Bloemer
- Department of Drug Discovery and Development, Auburn University, Auburn, Alabama, USA
- Department of Pharmaceutical and Biomedical Sciences, Touro College of Pharmacy, New York, NY, USA
| | - Lauren N. Woodie
- Department of Nutrition, Dietetics and Hospitality Management, College of Human Sciences, Auburn University, Auburn, Alabama, USA
- Institute for Diabetes, Obesity and Metabolism, Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Manal A. Buabeid
- College of Pharmacy and Health Sciences, Ajman University, Ajman, United Arab Emirates
| | - Subhrajit Bhattacharya
- Department of Drug Discovery and Development, Auburn University, Auburn, Alabama, USA
- Center for Neuroscience Initiative, Auburn University, Auburn, AL, USA
| | - Shanese L. Jasper
- Department of Drug Discovery and Development, Auburn University, Auburn, Alabama, USA
| | | | - Muralikrishnan Dhanasekaran
- Department of Drug Discovery and Development, Auburn University, Auburn, Alabama, USA
- Center for Neuroscience Initiative, Auburn University, Auburn, AL, USA
| | - Martha Escobar
- Department of Psychology, Oakland University, Rochester, MI, USA
| | - Robert D. Arnold
- Department of Drug Discovery and Development, Auburn University, Auburn, Alabama, USA
- Center for Neuroscience Initiative, Auburn University, Auburn, AL, USA
| | - Vishnu Suppiramaniam
- Department of Drug Discovery and Development, Auburn University, Auburn, Alabama, USA
- Center for Neuroscience Initiative, Auburn University, Auburn, AL, USA
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Barry J, Sarafian TA, Watson JB, Cepeda C, Levine MS. Mechanisms underlying the enhancement of γ-aminobutyric acid responses in the external globus pallidus of R6/2 Huntington's disease model mice. J Neurosci Res 2020; 98:2349-2356. [PMID: 32856336 DOI: 10.1002/jnr.24710] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2020] [Revised: 07/19/2020] [Accepted: 07/22/2020] [Indexed: 02/06/2023]
Abstract
In Huntington's disease (HD), the output of striatal indirect pathway medium-sized spiny neurons (MSNs) is altered in its target region, the external globus pallidus (GPe). In a previous study we demonstrated that selective optogenetic stimulation of indirect pathway MSNs induced prolonged decay time of γ-aminobutyric acid (GABA) responses in GPe neurons. Here we identified the mechanism underlying this alteration. Electrophysiological recordings in slices from symptomatic R6/2 and wildtype (WT) mice were used to evaluate, primarily, the effects of GABA transporter (GAT) antagonists on responses evoked by optogenetic activation of indirect pathway MSNs. In addition, immunohistochemistry (IHC) and Western blots (WBs) were used to examine GAT-3 expression in HD and WT mice. A GAT-3 blocker (SNAP5114) increased decay time of GABA responses in WT and HD GPe neurons, but the effect was significantly greater in WT neurons. In contrast, a GAT-1 antagonist (NO-711) or a GABAB receptor antagonist (CGP 54626) produced small increases in decay time but no differential effects between genotypes. IHC and WBs showed reduction of GAT-3 expression in the GPe of HD mice. Thus, reduced expression or dysfunction of GAT-3 could underlie alterations of GPe responses to GABA inputs from striatum and could be a target for therapeutic intervention.
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Affiliation(s)
- Joshua Barry
- IDDRC, Jane and Terry Semel Institute for Neuroscience & Human Behavior, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Theodore A Sarafian
- IDDRC, Jane and Terry Semel Institute for Neuroscience & Human Behavior, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Joseph B Watson
- IDDRC, Jane and Terry Semel Institute for Neuroscience & Human Behavior, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Carlos Cepeda
- IDDRC, Jane and Terry Semel Institute for Neuroscience & Human Behavior, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Michael S Levine
- IDDRC, Jane and Terry Semel Institute for Neuroscience & Human Behavior, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
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Ahmad F, Liu P. Synaptosome as a tool in Alzheimer's disease research. Brain Res 2020; 1746:147009. [PMID: 32659233 DOI: 10.1016/j.brainres.2020.147009] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 06/21/2020] [Accepted: 07/04/2020] [Indexed: 12/29/2022]
Abstract
Synapse dysfunction is an integral feature of Alzheimer's disease (AD) pathophysiology. In fact, prodromal manifestation of structural and functional deficits in synapses much prior to appearance of overt pathological hallmarks of the disease indicates that AD might be considered as a degenerative disorder of the synapses. Several research instruments and techniques have allowed us to study synaptic function and plasticity and their alterations in pathological conditions, such as AD. One such tool is the biochemically isolated preparations of detached and resealed synaptic terminals, the "synaptosomes". Because of the preservation of many of the physiological processes such as metabolic and enzymatic activities, synaptosomes have proved to be an indispensable ex vivo model system to study synapse physiology both when isolated from fresh or cryopreserved tissues, and from animal or human post-mortem tissues. This model system has been tremendously successful in the case of post-mortem tissues because of their accessibility relative to acute brain slices or cultures. The current review details the use of synaptosomes in AD research and its potential as a valuable tool in furthering our understanding of the pathogenesis and in devising and testing of therapeutic strategies for the disease.
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Affiliation(s)
- Faraz Ahmad
- Department of Anatomy, School of Biomedical Sciences, Brain Research New Zealand, University of Otago, Dunedin, New Zealand.
| | - Ping Liu
- Department of Anatomy, School of Biomedical Sciences, Brain Research New Zealand, University of Otago, Dunedin, New Zealand
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9
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Bloemer J, Pinky PD, Smith WD, Bhattacharya D, Chauhan A, Govindarajulu M, Hong H, Dhanasekaran M, Judd R, Amin RH, Reed MN, Suppiramaniam V. Adiponectin Knockout Mice Display Cognitive and Synaptic Deficits. Front Endocrinol (Lausanne) 2019; 10:819. [PMID: 31824431 PMCID: PMC6886372 DOI: 10.3389/fendo.2019.00819] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Accepted: 11/08/2019] [Indexed: 12/21/2022] Open
Abstract
Adiponectin is an adipokine that has recently been under investigation for potential neuroprotective effects in various brain disorders including Alzheimer's disease, stroke, and depression. Adiponectin receptors (AdipoR1 and AdipoR2) are found throughout various brain regions, including the hippocampus. However, the role of these receptors in synaptic and cognitive function is not clear. Therefore, the goal of the current study was to evaluate synaptic and cognitive function in the absence of adiponectin. The current study utilized 12-month-old adiponectin knockout (APN-KO) mice and age-matched controls to study cognitive and hippocampal synaptic alterations. We determined that AdipoR1 and AdipoR2 are present in the synaptosome, with AdipoR2 displaying increased presynaptic vs. postsynaptic localization, whereas AdipoR1 was enriched in both the presynaptic and postsynaptic fractions. APN-KO mice displayed cognitive deficits in the novel object recognition (NOR) and Y-maze tests. This was mirrored by deficits in long-term potentiation (LTP) of the hippocampal Schaefer collateral pathway in APN-KO mice. APN-KO mice also displayed a reduction in basal synaptic transmission and an increase in presynaptic release probability. Deficits in LTP were rescued through hippocampal slice incubation with the adiponectin receptor agonist, AdipoRon, indicating that acute alterations in adiponectin receptor signaling influence synaptic function. Along with the deficits in LTP, altered levels of key presynaptic and postsynaptic proteins involved in glutamatergic neurotransmission were observed in APN-KO mice. Taken together, these results indicate that adiponectin is an important regulator of cognition and synaptic function in the hippocampus. Future studies should examine the role of specific adiponectin receptors in synaptic processes.
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Affiliation(s)
- Jenna Bloemer
- Department of Drug Discovery and Development, Harrison School of Pharmacy, Auburn University, Auburn, AL, United States
- Center for Neuroscience, Auburn University, Auburn, AL, United States
| | - Priyanka D. Pinky
- Department of Drug Discovery and Development, Harrison School of Pharmacy, Auburn University, Auburn, AL, United States
- Center for Neuroscience, Auburn University, Auburn, AL, United States
| | - Warren D. Smith
- Department of Drug Discovery and Development, Harrison School of Pharmacy, Auburn University, Auburn, AL, United States
- Center for Neuroscience, Auburn University, Auburn, AL, United States
| | - Dwipayan Bhattacharya
- Department of Drug Discovery and Development, Harrison School of Pharmacy, Auburn University, Auburn, AL, United States
| | - Alisa Chauhan
- Department of Drug Discovery and Development, Harrison School of Pharmacy, Auburn University, Auburn, AL, United States
| | - Manoj Govindarajulu
- Department of Drug Discovery and Development, Harrison School of Pharmacy, Auburn University, Auburn, AL, United States
- Center for Neuroscience, Auburn University, Auburn, AL, United States
| | - Hao Hong
- Center for Neuroscience, Auburn University, Auburn, AL, United States
- Key Laboratory of Neuropsychiatric Diseases, Department of Pharmacology, China Pharmaceutical University, Nanjing, China
| | - Muralikrishnan Dhanasekaran
- Department of Drug Discovery and Development, Harrison School of Pharmacy, Auburn University, Auburn, AL, United States
- Center for Neuroscience, Auburn University, Auburn, AL, United States
| | - Robert Judd
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL, United States
| | - Rajesh H. Amin
- Department of Drug Discovery and Development, Harrison School of Pharmacy, Auburn University, Auburn, AL, United States
- Center for Neuroscience, Auburn University, Auburn, AL, United States
| | - Miranda N. Reed
- Department of Drug Discovery and Development, Harrison School of Pharmacy, Auburn University, Auburn, AL, United States
- Center for Neuroscience, Auburn University, Auburn, AL, United States
- *Correspondence: Miranda N. Reed
| | - Vishnu Suppiramaniam
- Department of Drug Discovery and Development, Harrison School of Pharmacy, Auburn University, Auburn, AL, United States
- Center for Neuroscience, Auburn University, Auburn, AL, United States
- Vishnu Suppiramaniam
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Neonatal maternal deprivation impairs localized de novo activity-induced protein translation at the synapse in the rat hippocampus. Biosci Rep 2018; 38:BSR20180118. [PMID: 29700212 PMCID: PMC5997792 DOI: 10.1042/bsr20180118] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Revised: 04/16/2018] [Accepted: 04/24/2018] [Indexed: 11/17/2022] Open
Abstract
Neonatal neuropsychiatric stress induces alterations in neurodevelopment that can lead to irreversible damage to neuronal physiology, and social, behavioral, and cognitive skills. In addition, this culminates to an elevated vulnerability to stress and anxiety later in life. Developmental deficits in hippocampal synaptic function and plasticity are among the primary contributors of detrimental alterations in brain function induced by early-life stress. However, the underlying molecular mechanisms are not completely understood. Localized protein translation, occurring at the synapse and triggered by neuronal activity, is critical for synapse function, maintenance, and plasticity. We used a rodent model of chronic maternal deprivation to characterize the effects of early-life neuropsychiatric stress on localized de novo protein translation at synaptic connections between neurons. Synaptoneurosomal preparations isolated biochemically from the hippocampi of rat pups that were subjected to maternal deprivation were deficient in depolarization-induced activity-dependent protein translation when compared with littermate controls. Conversely, basal unstimulated protein translation was not affected. Moreover, deficits in activity-driven synaptic protein translation were significantly correlated with a reduction in phosphorylated cell survival protein kinase protein B or Akt (p473 Ser and p308 Thr), but not phosphorylated extracellular signal-regulated kinase.
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The Study of Postmortem Human Synaptosomes for Understanding Alzheimer's Disease and Other Neurological Disorders: A Review. Neurol Ther 2017; 6:57-68. [PMID: 28733958 PMCID: PMC5520816 DOI: 10.1007/s40120-017-0070-z] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Indexed: 12/12/2022] Open
Abstract
Synaptic dysfunction is thought to play important roles in the pathophysiology of many neurological diseases, including Alzheimer’s disease, Parkinson’s disease, and schizophrenia. Over the past few decades, there have been systematic efforts to collect postmortem brain tissues via autopsies, leading to the establishment of dozens of human brain banks around the world. From cryopreserved human brain tissues, it is possible to isolate detached-and-resealed synaptic terminals termed synaptosomes, which remain metabolically and enzymatically active. Synaptosomes have become important model systems for studying human synaptic functions, being much more accessible than ex vivo brain slices or primary neuronal cultures. Here we review recent advances in the establishment of human brain banks, the isolation of synaptosomes, their biological activities, and various analytical techniques for investigating their biochemical and ultrastructural properties. There are unique insights to be gained by directly examining human synaptosomes, which cannot be substituted by animal models. We will also discuss how human synaptosome research has contributed to better understanding of neurological disorders, especially Alzheimer’s disease.
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12
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Sta Maria NS, Reger ML, Cai Y, Baquing MAT, Buen F, Ponnaluri A, Hovda DA, Harris NG, Giza CC. D-Cycloserine Restores Experience-Dependent Neuroplasticity after Traumatic Brain Injury in the Developing Rat Brain. J Neurotrauma 2017; 34:1692-1702. [PMID: 27931146 PMCID: PMC5397224 DOI: 10.1089/neu.2016.4747] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Traumatic brain injury (TBI) in children can cause persisting cognitive and behavioral dysfunction, and inevitably raises concerns about lost potential in these injured youth. Lateral fluid percussion injury (FPI) in weanling rats pathologically affects hippocampal N-methyl-d-aspartate receptor (NMDAR)- and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR)-mediated glutamatergic neurotransmission subacutely within the first post-injury week. FPI to weanling rats has also been shown to impair enriched-environment (EE) induced enhancement of Morris water maze (MWM) learning and memory in adulthood. Recently, improved outcomes can be achieved using agents that enhance NMDAR function. We hypothesized that administering D-cycloserine (DCS), an NMDAR co-agonist, every 12 h (i.p.) would restore subacute glutamatergic neurotransmission and reinstate experience-dependent plasticity. Postnatal day 19 (P19) rats received either a sham or FPI. On post-injury day (PID) 1-3, animals were randomized to saline (Sal) or DCS. Firstly, immunoblotting of hippocampal NMDAR and AMPAR proteins were measured on PID4. Second, PID4 novel object recognition, an NMDAR- and hippocampal- mediated working memory task, was assessed. Third, P19 rats were placed in an EE (17 days), and MWM performance was measured, starting on PID30. On PID4, DCS restored reduced NR2A and increased GluR2 by 54%, and also restored diminished recognition memory in FPI pups. EE significantly improved MWM performance in shams, regardless of treatment. In contrast, FPI-EE-Sal animals only performed to the level of standard housed animals, whereas FPI-EE-DCS animals were comparable with sham-EE counterparts. This study shows that NMDAR agonist use during reduced glutamatergic transmission after developmental TBI can reinstate early molecular and behavioral responses that subsequently manifest in experience-dependent plasticity and rescued potential.
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Affiliation(s)
- Naomi S. Sta Maria
- Department of Neurosurgery, UCLA Brain Injury Research Center, Los Angeles, California
- Department of Bioengineering, UCLA Brain Injury Research Center, Los Angeles, California
| | - Maxine L. Reger
- Department of Neurosurgery, UCLA Brain Injury Research Center, Los Angeles, California
- Department of Psychology, UCLA Brain Injury Research Center, Los Angeles, California
| | - Yan Cai
- Department of Neurosurgery, UCLA Brain Injury Research Center, Los Angeles, California
| | - Mary Anne T. Baquing
- Department of Neurosurgery, UCLA Brain Injury Research Center, Los Angeles, California
- Harbor-UCLA Department of Obstetrics and Gynecology, UCLA Brain Injury Research Center, Los Angeles, California
| | - Floyd Buen
- Department of Neurosurgery, UCLA Brain Injury Research Center, Los Angeles, California
- Department of Head and Neck Surgery, UCLA Brain Injury Research Center, Los Angeles, California
| | - Aditya Ponnaluri
- Department of Neurosurgery, UCLA Brain Injury Research Center, Los Angeles, California
- Department of Mechanical Engineering, UCLA Brain Injury Research Center, Los Angeles, California
| | - David A. Hovda
- Department of Neurosurgery, UCLA Brain Injury Research Center, Los Angeles, California
- Department of Medical and Molecular Pharmacology, UCLA Brain Injury Research Center, Los Angeles, California
| | - Neil G. Harris
- Department of Neurosurgery, UCLA Brain Injury Research Center, Los Angeles, California
| | - Christopher C. Giza
- Department of Neurosurgery, UCLA Brain Injury Research Center, Los Angeles, California
- Division of Pediatric Neurology, UCLA Brain Injury Research Center, Los Angeles, California
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Sarafian TA, Littlejohn K, Yuan S, Fernandez C, Cilluffo M, Koo BK, Whitelegge JP, Watson JB. Stimulation of synaptoneurosome glutamate release by monomeric and fibrillated α-synuclein. J Neurosci Res 2017; 95:1871-1887. [PMID: 28117497 DOI: 10.1002/jnr.24024] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Revised: 11/11/2016] [Accepted: 12/28/2016] [Indexed: 12/28/2022]
Abstract
The α-synuclein protein exists in vivo in a variety of covalently modified and aggregated forms associated with Parkinson's disease (PD) pathology. However, the specific proteoform structures involved with neuropathological disease mechanisms are not clearly defined. Since α-synuclein plays a role in presynaptic neurotransmitter release, an in vitro enzyme-based assay was developed to measure glutamate release from mouse forebrain synaptoneurosomes (SNs) enriched in synaptic endings. Glutamate measurements utilizing SNs from various mouse genotypes (WT, over-expressers, knock-outs) suggested a concentration dependence of α-synuclein on calcium/depolarization-dependent presynaptic glutamate release from forebrain terminals. In vitro reconstitution experiments with recombinant human α-synuclein proteoforms including monomers and aggregated forms (fibrils, oligomers) produced further evidence of this functional impact. Notably, brief exogenous applications of fibrillated forms of α-synuclein enhanced SN glutamate release but monomeric forms did not, suggesting preferential membrane penetration and toxicity by the aggregated forms. However, when applied to brain tissue sections just prior to homogenization, both monomeric and fibrillated forms stimulated glutamate release. Immuno-gold and transmission electron microscopy (TEM) detected exogenous fibrillated α-synuclein associated with numerous SN membranous structures including synaptic terminals. Western blots and immuno-gold TEM were consistent with SN internalization of α-synuclein. Additional studies revealed no evidence of gross disruption of SN membrane integrity or glutamate transporter function by exogenous α-synuclein. Overall excitotoxicity, due to enhanced glutamate release in the face of either overexpressed monomeric α-synuclein or extrasynaptic exposure to fibrillated α-synuclein, should be considered as a potential neuropathological pathway during the progression of PD and other synucleinopathies. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Theodore A Sarafian
- Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA
| | - Kaitlyn Littlejohn
- Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA
| | - Sarah Yuan
- Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA
| | - Charlene Fernandez
- Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA
| | | | - Bon-Kyung Koo
- Department of Chemistry and Biochemistry, UCLA, Los Angeles, CA, USA
| | - Julian P Whitelegge
- Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA
| | - Joseph B Watson
- Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA
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Banerjee B, Medda BK, Zhang J, Tuchscherer V, Babygirija R, Kannampalli P, Sengupta JN, Shaker R. Prolonged esophageal acid exposures induce synaptic downscaling of cortical membrane AMPA receptor subunits in rats. Neurogastroenterol Motil 2016; 28:1356-69. [PMID: 27271201 PMCID: PMC5063079 DOI: 10.1111/nmo.12834] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Accepted: 03/11/2016] [Indexed: 02/08/2023]
Abstract
BACKGROUND We recently reported the involvement of AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptor subunit upregulation and phosphorylation in the rostral cingulate cortex (rCC) as the underlying mechanism of acute esophageal acid-induced cortical sensitization. Based on these findings, we proposed to investigate whether prolonged esophageal acid exposures in rats exhibit homeostatic synaptic scaling through downregulation of AMPA receptor expression in rCC neurons. We intended to study further whether this compensatory mechanism is impaired when rats are pre-exposed to repeated esophageal acid exposures neonatally during neuronal development. METHODS Two different esophageal acid exposure protocols in rats were used. Since AMPA receptor trafficking and channel conductance depend on CaMKIIα-mediated phosphorylation of AMPA receptor subunits, we examined the effect of esophageal acid on CaMKIIα activation and AMPA receptor expression in synaptoneurosomes and membrane preparations from rCCs. KEY RESULTS In cortical membrane preparations, GluA1 and pGluA1Ser(831) expression were significantly downregulated following prolonged acid exposures in adult rats; this was accompanied by the significant downregulation of cortical membrane pCaMKIIα expression. No change in GluA1 and pGluA1Ser(831) expression was observed in rCC membrane preparations in rats pre-exposed to acid neonatally followed by adult rechallenge. CONCLUSIONS & INFERENCES This study along with our previous findings suggests that synaptic AMPA receptor subunits expression and phosphorylation may be involved bidirectionally in both esophageal acid-induced neuronal sensitization and acid-dependent homeostatic plasticity in cortical neurons. The impairment of homeostatic compensatory mechanism as observed following early-in-life acid exposure could be the underlying mechanism of heightening cortical sensitization and esophageal hypersensitivity in patients with gastroesophageal reflux disease.
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Affiliation(s)
- Banani Banerjee
- Gastroenterology & Hepatology, Department of Medicine, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Bidyut K Medda
- Gastroenterology & Hepatology, Department of Medicine, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Jian Zhang
- Gastroenterology & Hepatology, Department of Medicine, Medical College of Wisconsin, Milwaukee, WI, United States
| | | | - Reji Babygirija
- Gastroenterology & Hepatology, Department of Pediatrics, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Pradeep Kannampalli
- Gastroenterology & Hepatology, Department of Medicine, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Jyoti N. Sengupta
- Gastroenterology & Hepatology, Department of Medicine, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Reza Shaker
- Gastroenterology & Hepatology, Department of Medicine, Medical College of Wisconsin, Milwaukee, WI, United States
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15
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Adelson JD, Sapp RW, Brott BK, Lee H, Miyamichi K, Luo L, Cheng S, Djurisic M, Shatz CJ. Developmental Sculpting of Intracortical Circuits by MHC Class I H2-Db and H2-Kb. Cereb Cortex 2016; 26:1453-1463. [PMID: 25316337 PMCID: PMC4785944 DOI: 10.1093/cercor/bhu243] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Synapse pruning is an activity-regulated process needed for proper circuit sculpting in the developing brain. Major histocompatibility class I (MHCI) molecules are regulated by activity, but little is known about their role in the development of connectivity in cortex. Here we show that protein for 2 MHCI molecules H2-Kb and H2-Db is associated with synapses in the visual cortex. Pyramidal neurons in mice lacking H2-Kb and H2-Db (KbDb KO) have more extensive cortical connectivity than normal. Modified rabies virus tracing was used to monitor the extent of pyramidal cell connectivity: Horizontal connectivity is greater in the visual cortex of KbDb KO mice. Basal dendrites of L2/3 pyramids, where many horizontal connections terminate, are more highly branched and have elevated spine density in the KO. Furthermore, the density of axonal boutons is elevated within L2/3 of mutant mice. These increases are accompanied by elevated miniature excitatory postsynaptic current frequency, consistent with an increase in functional synapses. This functional and anatomical increase in intracortical connectivity is also associated with enhanced ocular dominance plasticity that persists into adulthood. Thus, these MHCI proteins regulate sculpting of local cortical circuits and in their absence, the excess connectivity can function as a substrate for cortical plasticity throughout life.
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Affiliation(s)
| | | | | | - Hanmi Lee
- Departments of Biology and Neurobiology and Bio-X
| | | | - Liqun Luo
- Department of Biology, Stanford University, Stanford, CA94305, USA
| | - Sarah Cheng
- Departments of Biology and Neurobiology and Bio-X
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16
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Caesar M, Felk S, Aasly JO, Gillardon F. Changes in actin dynamics and F-actin structure both in synaptoneurosomes of LRRK2(R1441G) mutant mice and in primary human fibroblasts of LRRK2(G2019S) mutation carriers. Neuroscience 2014; 284:311-324. [PMID: 25301747 DOI: 10.1016/j.neuroscience.2014.09.070] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Revised: 09/01/2014] [Accepted: 09/02/2014] [Indexed: 12/13/2022]
Abstract
Converging evidence suggests that the Parkinson's disease-linked leucine-rich repeat kinase 2 (LRRK2) modulates cellular function by regulating actin dynamics. In the present study we investigate the role of LRRK2 in functional synaptic terminals of adult LRRK2-knockout and LRRK2(R1441G)-transgenic mice as well as in primary fibroblasts of LRRK2(G2019S) mutation carriers. We show that lack of LRRK2 decreases and overexpression of mutant LRRK2 age-dependently increases the effect of the actin depolymerizing agent Latrunculin A (LatA) on the synaptic cytoskeleton. Similarly, endogenous mutant LRRK2 increases sensitivity to LatA in primary fibroblasts. Under basal conditions however, these fibroblasts show an increase in F-actin bundles and a decrease in filopodial length which can be rescued by LatA treatment. Our data suggest that LRRK2 alters actin dynamics and F-actin structure both in brain neurons and skin fibroblasts. We hypothesize that increased F-actin bundling represents a compensatory mechanism to protect F-actin from the depolymerizing effect of mutant LRRK2 under basal conditions. Our data further indicate that LRRK2-dependent changes in the cytoskeleton might have functional consequences on postsynaptic NMDA receptor localization.
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Affiliation(s)
- M Caesar
- Boehringer Ingelheim Pharma GmbH & Co. KG, CNS Diseases Research, Biberach an der Riss, Germany.
| | - S Felk
- Boehringer Ingelheim Pharma GmbH & Co. KG, CNS Diseases Research, Biberach an der Riss, Germany
| | - J O Aasly
- St. Olav's University Hospital, Department of Neurology, Trondheim, Norway
| | - F Gillardon
- Boehringer Ingelheim Pharma GmbH & Co. KG, CNS Diseases Research, Biberach an der Riss, Germany.
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17
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Synapse elimination and learning rules co-regulated by MHC class I H2-Db. Nature 2014; 509:195-200. [PMID: 24695230 PMCID: PMC4016165 DOI: 10.1038/nature13154] [Citation(s) in RCA: 176] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Accepted: 02/13/2014] [Indexed: 12/31/2022]
Abstract
The formation of precise connections between retina and LGN involves the activity-dependent elimination of some synapses, with strengthening and retention of others. Here we show that the MHC Class I (MHCI) molecule H2-Db is necessary and sufficient for synapse elimination in the retinogeniculate system. In mice lacking both H2-Kb and H2-Db (KbDb−/−) despite intact retinal activity and basal synaptic transmission, the developmentally-regulated decrease in functional convergence of retinal ganglion cell synaptic inputs to LGN neurons fails and eye-specific layers do not form. Neuronal expression of just H2-Db in KbDb−/− mice rescues both synapse elimination and eye specific segregation despite a compromised immune system. When patterns of stimulation mimicking endogenous retinal waves are used to probe synaptic learning rules at retinogeniculate synapses, LTP is intact but LTD is impaired in KbDb−/− mice. This change is due to an increase in Ca2+ permeable AMPA receptors. Restoring H2-Db to KbDb−/− neurons renders AMPA receptors Ca2+ impermeable and rescues LTD. These observations reveal an MHCI mediated link between developmental synapse pruning and balanced synaptic learning rules enabling both LTD and LTP, and demonstrate a direct requirement for H2-Db in functional and structural synapse pruning in CNS neurons.
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18
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Caesar M, Felk S, Zach S, Brønstad G, Aasly JO, Gasser T, Gillardon F. Changes in matrix metalloprotease activity and progranulin levels may contribute to the pathophysiological function of mutant leucine-rich repeat kinase 2. Glia 2014; 62:1075-92. [DOI: 10.1002/glia.22663] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Revised: 03/04/2014] [Accepted: 03/07/2014] [Indexed: 12/28/2022]
Affiliation(s)
- Mareike Caesar
- Boehringer Ingelheim Pharma GmbH & Co KG; CNS Diseases Research; Biberach an der Riss Germany
| | - Sandra Felk
- Boehringer Ingelheim Pharma GmbH & Co KG; CNS Diseases Research; Biberach an der Riss Germany
| | - Susanne Zach
- Boehringer Ingelheim Pharma GmbH & Co KG; CNS Diseases Research; Biberach an der Riss Germany
| | - Gunnar Brønstad
- St. Olav's University Hospital; Department of Neurology; Trondheim Norway
| | - Jan O. Aasly
- St. Olav's University Hospital; Department of Neurology; Trondheim Norway
| | - Thomas Gasser
- Hertie Institut fuer klinische Hirnforschung; Tuebingen Germany
| | - Frank Gillardon
- Boehringer Ingelheim Pharma GmbH & Co KG; CNS Diseases Research; Biberach an der Riss Germany
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19
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Parameshwaran K, Buabeid MA, Bhattacharya S, Uthayathas S, Kariharan T, Dhanasekaran M, Suppiramaniam V. Long term alterations in synaptic physiology, expression of β2 nicotinic receptors and ERK1/2 signaling in the hippocampus of rats with prenatal nicotine exposure. Neurobiol Learn Mem 2013; 106:102-11. [DOI: 10.1016/j.nlm.2013.07.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Revised: 06/29/2013] [Accepted: 07/09/2013] [Indexed: 01/22/2023]
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20
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Mielke JG. Susceptibility to oxygen-glucose deprivation is reduced in acute hippocampal slices from euthermic Syrian golden hamsters relative to slices from Sprague-Dawley rats. Neurosci Lett 2013; 553:13-7. [PMID: 23933209 DOI: 10.1016/j.neulet.2013.07.050] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 07/24/2013] [Accepted: 07/27/2013] [Indexed: 02/06/2023]
Abstract
Hibernation in mammals is characterised by a marked decrease in body temperature and a dramatic suppression of metabolism. In addition, despite experiencing a reduced cardiac output that would normally cause profound cerebral ischaemia, hibernating animals display robust neuroprotection. However, whether the reduced susceptibility to neural injury displayed by hibernators is attributable to an innate factor, or to the physiologic changes that accompany hibernation, remains uncertain. To help clarify the nature of the ischaemic tolerance displayed by hibernators, the current study examined hippocampal slices from rodents not capable of hibernation (rat) and rodents that could undergo hibernation (hamsters), but were active immediately prior to slice preparation. Slices from each species were subjected to oxygen-glucose deprivation (OGD; a commonly used in vitro model of ischaemia), and their viability examined after a recovery period. Although OGD reduced plasma membrane integrity in each species, rat-derived slices displayed a nearly threefold greater degree of effect. In addition, only slices harvested from rats showed reductions in synaptic mitochondrial function. While the improved ischaemic tolerance displayed by euthermic hamster brain slices maintained at a physiological temperature suggests an intrinsic, protection-related variable, the synaptic level of the GluN1 subunit (which is required to form functional NMDA receptors) was not found to be different between the two species. Further work is needed to improve understanding of the molecular mechanisms underlying the intrinsic injury tolerance of hibernator brain, which should help provide inspiration for new approaches to neuroprotection.
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Affiliation(s)
- John G Mielke
- School of Public Health and Health Systems, University of Waterloo, Waterloo, ON, Canada.
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21
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Kintz N, Petzinger GM, Akopian G, Ptasnik S, Williams C, Jakowec MW, Walsh JP. Exercise modifies α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor expression in striatopallidal neurons in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-lesioned mouse. J Neurosci Res 2013; 91:1492-507. [PMID: 23918451 DOI: 10.1002/jnr.23260] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Revised: 04/26/2013] [Accepted: 05/16/2013] [Indexed: 12/11/2022]
Abstract
The α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic-acid-type glutamate receptor (AMPAR) plays a critical role in modulating experience-dependent neuroplasticity, and alterations in AMPAR expression may underlie synaptic dysfunction and disease pathophysiology. Using the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of dopamine (DA) depletion, our previous work showed exercise increases total GluA2 subunit expression and the contribution of GluA2-containing channels in MPTP mice. The purpose of this study was to determine whether exercise-dependent changes in AMPAR expression after MPTP are specific to the striatopallidal (D2 R) or striatonigral (D1 R) medium spiny neuron (MSN) striatal projection pathways. Drd2 -eGFP-BAC transgenic mice were used to delineate differences in AMPAR expression between striatal D2 R-MSNs and D1 R-MSNs. Striatal AMPAR expression was assessed by immunohistochemical (IHC) staining, Western immunoblotting (WB) of preparations enriched for postsynaptic density (PSD), and alterations in the current-voltage relationship of MSNs. We found DA depletion results in the emergence of GluA2-lacking AMPARs selectively in striatopallidal D2 R-MSNs and that exercise reverses this effect in MPTP mice. Exercise-induced changes in AMPAR channels observed after DA depletion were associated with alterations in GluA1 and GluA2 subunit expression in postsynaptic protein, D2 R-MSN cell surface expression, and restoration of corticostriatal plasticity. Mechanisms regulating experience-dependent changes in AMPAR expression may provide innovative therapeutic targets to increase the efficacy of treatments for basal ganglia disorders, including Parkinson's disease.
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Affiliation(s)
- N Kintz
- The George and MaryLou Boone Center for Parkinson's Disease Research, Department of Neurology, University of Southern California, Los Angeles, California
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22
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Sarafian TA, Ryan CM, Souda P, Masliah E, Kar UK, Vinters HV, Mathern GW, Faull KF, Whitelegge JP, Watson JB. Impairment of mitochondria in adult mouse brain overexpressing predominantly full-length, N-terminally acetylated human α-synuclein. PLoS One 2013; 8:e63557. [PMID: 23667637 PMCID: PMC3646806 DOI: 10.1371/journal.pone.0063557] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Accepted: 04/02/2013] [Indexed: 12/24/2022] Open
Abstract
While most forms of Parkinson's Disease (PD) are sporadic in nature, a small percentage of PD have genetic causes as first described for dominant, single base pair changes as well as duplication and triplication in the α-synuclein gene. The α-synuclein gene encodes a 140 amino acid residue protein that interacts with a variety of organelles including synaptic vesicles, lysosomes, endoplasmic reticulum/Golgi vesicles and, reported more recently, mitochondria. Here we examined the structural and functional interactions of human α-synuclein with brain mitochondria obtained from an early, pre-manifest mouse model for PD over-expressing human α-synuclein (ASOTg). The membrane potential in ASOTg brain mitochondria was decreased relative to wildtype (WT) mitochondria, while reactive oxygen species (ROS) were elevated in ASOTg brain mitochondria. No selective interaction of human α-synuclein with mitochondrial electron transport complexes cI-cV was detected. Monomeric human α-synuclein plus carboxyl terminally truncated forms were the predominant isoforms detected in ASOTg brain mitochondria by 2-dimensional PAGE (Native/SDS) and immunoblotting. Oligomers or fibrils were not detected with amyloid conformational antibodies. Mass spectrometry of human α-synuclein in both ASOTg brain mitochondria and homogenates from surgically resected human cortex demonstrated that the protein was full-length and postranslationally modified by N-terminal acetylation. Overall the study showed that accumulation of full-length, N-terminally acetylated human α-synuclein was sufficient to disrupt brain mitochondrial function in adult mice.
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Affiliation(s)
- Theodore A. Sarafian
- Department of Psychiatry & Biobehavioral Sciences, David Geffen School of Medicine at UCLA, Los Angeles, California, United States of America
| | - Christopher M. Ryan
- Department of Psychiatry & Biobehavioral Sciences, David Geffen School of Medicine at UCLA, Los Angeles, California, United States of America
| | - Puneet Souda
- Department of Psychiatry & Biobehavioral Sciences, David Geffen School of Medicine at UCLA, Los Angeles, California, United States of America
| | - Eliezer Masliah
- Department of Neuroscience, University of California, San Diego School of Medicine, La Jolla, California, United States of America
| | - Upendra K. Kar
- Department of Psychiatry & Biobehavioral Sciences, David Geffen School of Medicine at UCLA, Los Angeles, California, United States of America
| | - Harry V. Vinters
- Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at UCLA, Los Angeles, California, United States of America
| | - Gary W. Mathern
- Department of Psychiatry & Biobehavioral Sciences, David Geffen School of Medicine at UCLA, Los Angeles, California, United States of America
- Department of Neurosurgery, David Geffen School of Medicine at UCLA, Los Angeles, California, United States of America
| | - Kym F. Faull
- Department of Psychiatry & Biobehavioral Sciences, David Geffen School of Medicine at UCLA, Los Angeles, California, United States of America
| | - Julian P. Whitelegge
- Department of Psychiatry & Biobehavioral Sciences, David Geffen School of Medicine at UCLA, Los Angeles, California, United States of America
| | - Joseph B. Watson
- Department of Psychiatry & Biobehavioral Sciences, David Geffen School of Medicine at UCLA, Los Angeles, California, United States of America
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Chang JW, Arnold MM, Rozenbaum A, Caputo A, Schweizer FE, Huynh M, Mathern GW, Sarafian TA, Watson JB. Synaptoneurosome micromethod for fractionation of mouse and human brain, and primary neuronal cultures. J Neurosci Methods 2012; 211:289-95. [PMID: 23017979 DOI: 10.1016/j.jneumeth.2012.09.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Revised: 07/25/2012] [Accepted: 09/05/2012] [Indexed: 11/26/2022]
Abstract
Brain and primary neuron fractions enriched in synaptic terminals are important tools for neuroscientists in biochemical, neuroanatomical and physiological studies. We describe an annotated updated micro-method for preparing synaptoneurosomes (SNs) enriched in presynaptic and postsynaptic elements. An easy to follow, step-by-step, protocol is provided for making SNs from small amounts of mammalian brain tissue. This includes novel applications for material obtained from human neurosurgical procedures and primary rat neuronal cultures. Our updated method for preparing SNs using smaller amounts of tissue provides a valuable new tool and expands the capabilities of neuroscientists.
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Affiliation(s)
- Julia W Chang
- Department of Neurosurgery, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
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24
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Marty VN, Spigelman I. Long-lasting alterations in membrane properties, k(+) currents, and glutamatergic synaptic currents of nucleus accumbens medium spiny neurons in a rat model of alcohol dependence. Front Neurosci 2012; 6:86. [PMID: 22701402 PMCID: PMC3370662 DOI: 10.3389/fnins.2012.00086] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Accepted: 05/22/2012] [Indexed: 01/19/2023] Open
Abstract
Chronic alcohol exposure causes marked changes in reinforcement mechanisms and motivational state that are thought to contribute to the development of cravings and relapse during protracted withdrawal. The nucleus accumbens (NAcc) is a key structure of the mesolimbic dopaminergic reward system. Although the NAcc plays an important role in mediating alcohol-seeking behaviors, little is known about the molecular mechanisms underlying alcohol-induced neuroadaptive changes in NAcc function. The aim of this study was to investigate the effects of chronic intermittent ethanol (CIE) treatment, a rat model of alcohol withdrawal and dependence, on intrinsic electrical membrane properties and glutamatergic synaptic transmission of medium spiny neurons (MSNs) in the NAcc core during protracted withdrawal. We show that CIE treatment followed by prolonged withdrawal increased the inward rectification of MSNs observed at hyperpolarized potentials. In addition, MSNs from CIE-treated animals displayed a lower input resistance, faster action potentials (APs), and larger fast afterhyperpolarizations (fAHPs) than MSNs from vehicle-treated animals, all suggestive of increases in K(+)-channel conductances. Significant increases in the Cs(+)-sensitive inwardly rectifying K(+)-current accounted for the increased input resistance, while increases in the A-type K(+)-current accounted for the faster APs and increased fAHPs in MSNs from CIE rats. We also show that the amplitude and the conductance of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR)-mediated mEPSCs were enhanced in CIE-treated animals due to an increase in a small fraction of functional postsynaptic GluA2-lacking AMPARs. These long-lasting modifications of excitability and excitatory synaptic receptor function of MSNs in the NAcc core could play a critical role in the neuroadaptive changes underlying alcohol withdrawal and dependence.
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Affiliation(s)
- Vincent N Marty
- Division of Oral Biology and Medicine, School of Dentistry, University of California Los Angeles, CA, USA
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25
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Adelson JD, Barreto GE, Xu L, Kim T, Brott BK, Ouyang YB, Naserke T, Djurisic M, Xiong X, Shatz CJ, Giffard RG. Neuroprotection from stroke in the absence of MHCI or PirB. Neuron 2012; 73:1100-7. [PMID: 22445338 DOI: 10.1016/j.neuron.2012.01.020] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/12/2012] [Indexed: 10/28/2022]
Abstract
Recovery from stroke engages mechanisms of neural plasticity. Here we examine a role for MHC class I (MHCI) H2-Kb and H2-Db, as well as PirB receptor. These molecules restrict synaptic plasticity and motor learning in the healthy brain. Stroke elevates neuronal expression not only of H2-Kb and H2-Db, but also of PirB and downstream signaling. KbDb knockout (KO) or PirB KO mice have smaller infarcts and enhanced motor recovery. KO hippocampal organotypic slices, which lack an intact peripheral immune response, have less cell death after in vitro ischemia. In PirB KO mice, corticospinal projections from the motor cortex are enhanced, and the reactive astrocytic response is dampened after MCAO. Thus, molecules that function in the immune system act not only to limit synaptic plasticity in healthy neurons, but also to exacerbate brain injury after ischemia. These results suggest therapies for stroke by targeting MHCI and PirB.
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Affiliation(s)
- Jaimie D Adelson
- Department of Biology and Neurobiology, Stanford University, Stanford, CA 94305-5437, USA
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26
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Parameshwaran K, Buabeid MA, Karuppagounder SS, Uthayathas S, Thiruchelvam K, Shonesy B, Dityatev A, Escobar MC, Dhanasekaran M, Suppiramaniam V. Developmental nicotine exposure induced alterations in behavior and glutamate receptor function in hippocampus. Cell Mol Life Sci 2012; 69:829-41. [PMID: 22033836 PMCID: PMC11114542 DOI: 10.1007/s00018-011-0805-4] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Revised: 07/29/2011] [Accepted: 08/11/2011] [Indexed: 12/24/2022]
Abstract
In the developing brain, nicotinic acetylcholine receptors (nAChRs) are involved in cell survival, targeting, formation of neural and sensory circuits, and development and maturation of other neurotransmitter systems. This regulatory role is disrupted when the developing brain is exposed to nicotine, which occurs with tobacco use during pregnancy. Prenatal nicotine exposure has been shown to be a strong risk factor for memory deficits and other behavioral aberrations in the offspring. The molecular mechanisms underlying these neurobehavioral outcomes are not clearly elucidated. We used a rodent model to assess behavioral, neurophysiological, and neurochemical consequences of prenatal nicotine exposure in rat offspring with specific emphasis on the hippocampal glutamatergic system. Pregnant dams were infused with nicotine (6 mg/kg/day) subcutaneously from the third day of pregnancy until birth. Results indicate that prenatal nicotine exposure leads to increased anxiety and depressive-like effects and impaired spatial memory. Synaptic plasticity in the form of long-term potentiation (LTP), basal synaptic transmission, and AMPA receptor-mediated synaptic currents were reduced. The deficit in synaptic plasticity was paralleled by declines in protein levels of vesicular glutamate transporter 1 (VGLUT1), synaptophysin, AMPA receptor subunit GluR1, phospho(Ser845) GluR1, and postsynaptic density 95 (PSD-95). These results suggest that prenatal nicotine exposure by maternal smoking could result in alterations in the glutamatergic system in the hippocampus contributing to the abnormal neurobehavioral outcomes.
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Affiliation(s)
- Kodeeswaran Parameshwaran
- Department of Pharmacal Sciences, Harrison School of Pharmacy, Auburn University, Auburn, AL 36849 USA
- Department of Pathobiology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849 USA
| | - Manal A. Buabeid
- Department of Pharmacal Sciences, Harrison School of Pharmacy, Auburn University, Auburn, AL 36849 USA
| | | | - Subramaniam Uthayathas
- Department of Pharmacal Sciences, Harrison School of Pharmacy, Auburn University, Auburn, AL 36849 USA
| | - Karikaran Thiruchelvam
- Department of Pharmacal Sciences, Harrison School of Pharmacy, Auburn University, Auburn, AL 36849 USA
| | - Brian Shonesy
- Department of Pharmacal Sciences, Harrison School of Pharmacy, Auburn University, Auburn, AL 36849 USA
| | - Alexander Dityatev
- Department of Pharmacal Sciences, Harrison School of Pharmacy, Auburn University, Auburn, AL 36849 USA
- Department of Neuroscience and Brain Technologies, Italian Institute of Technology, 16163 Genoa, Italy
| | | | | | - Vishnu Suppiramaniam
- Department of Pharmacal Sciences, Harrison School of Pharmacy, Auburn University, Auburn, AL 36849 USA
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27
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Kanju PM, Parameshwaran K, Sims-Robinson C, Uthayathas S, Josephson EM, Rajakumar N, Dhanasekaran M, Suppiramaniam V. Selective cholinergic depletion in medial septum leads to impaired long term potentiation and glutamatergic synaptic currents in the hippocampus. PLoS One 2012; 7:e31073. [PMID: 22355337 PMCID: PMC3280283 DOI: 10.1371/journal.pone.0031073] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Accepted: 01/02/2012] [Indexed: 12/02/2022] Open
Abstract
Cholinergic depletion in the medial septum (MS) is associated with impaired hippocampal-dependent learning and memory. Here we investigated whether long term potentiation (LTP) and synaptic currents, mediated by alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionate (AMPA) and N-methyl-D-aspartate (NMDA) receptors in the CA1 hippocampal region, are affected following cholinergic lesions of the MS. Stereotaxic intra-medioseptal infusions of a selective immunotoxin, 192-saporin, against cholinergic neurons or sterile saline were made in adult rats. Four days after infusions, hippocampal slices were made and LTP, whole cell, and single channel (AMPA or NMDA receptor) currents were recorded. Results demonstrated impairment in the induction and expression of LTP in lesioned rats. Lesioned rats also showed decreases in synaptic currents from CA1 pyramidal cells and synaptosomal single channels of AMPA and NMDA receptors. Our results suggest that MS cholinergic afferents modulate LTP and glutamatergic currents in the CA1 region of the hippocampus, providing a potential synaptic mechanism for the learning and memory deficits observed in the rodent model of selective MS cholinergic lesioning.
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Affiliation(s)
- Patrick M. Kanju
- Department of Pharmacal Sciences, Auburn University, Auburn, Alabama, United States of America
- Department of Neurobiology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Kodeeswaran Parameshwaran
- Department of Pharmacal Sciences, Auburn University, Auburn, Alabama, United States of America
- Department of Pathobiology, Auburn University, Auburn, Alabama, United States of America
| | - Catrina Sims-Robinson
- Department of Pharmacal Sciences, Auburn University, Auburn, Alabama, United States of America
- Department of Neurology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Subramaniam Uthayathas
- Department of Pharmacal Sciences, Auburn University, Auburn, Alabama, United States of America
- Department of Neurology, School of Medicine, Emory University, Atlanta, Georgia, United States of America
| | - Eleanor M. Josephson
- Department of Anatomy, Physiology and Pharmacology, Auburn University, Auburn, Alabama, United States of America
| | - Nagalingam Rajakumar
- Department of Anatomy and Cell Biology, The University of Western Ontario, London, Ontario, Canada
| | | | - Vishnu Suppiramaniam
- Department of Pharmacal Sciences, Auburn University, Auburn, Alabama, United States of America
- * E-mail:
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Oyang EL, Davidson BC, Lee W, Poon MM. Functional characterization of the dendritically localized mRNA neuronatin in hippocampal neurons. PLoS One 2011; 6:e24879. [PMID: 21935485 PMCID: PMC3173491 DOI: 10.1371/journal.pone.0024879] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2011] [Accepted: 08/22/2011] [Indexed: 11/19/2022] Open
Abstract
Local translation of dendritic mRNAs plays an important role in neuronal development and synaptic plasticity. Although several hundred putative dendritic transcripts have been identified in the hippocampus, relatively few have been verified by in situ hybridization and thus remain uncharacterized. One such transcript encodes the protein neuronatin. Neuronatin has been shown to regulate calcium levels in non-neuronal cells such as pancreatic or embryonic stem cells, but its function in mature neurons remains unclear. Here we report that neuronatin is translated in hippocampal dendrites in response to blockade of action potentials and NMDA-receptor dependent synaptic transmission by TTX and APV. Our study also reveals that neuronatin can adjust dendritic calcium levels by regulating intracellular calcium storage. We propose that neuronatin may impact synaptic plasticity by modulating dendritic calcium levels during homeostatic plasticity, thereby potentially regulating neuronal excitability, receptor trafficking, and calcium dependent signaling.
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Affiliation(s)
- Elaine L. Oyang
- Department of Biology, Harvey Mudd College, Claremont, California, Untied States of America
| | - Bonnie C. Davidson
- Department of Biology, Harvey Mudd College, Claremont, California, Untied States of America
| | - Winfong Lee
- Department of Biology, Harvey Mudd College, Claremont, California, Untied States of America
| | - Michael M. Poon
- Department of Biology, Harvey Mudd College, Claremont, California, Untied States of America
- * E-mail:
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29
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Cui W, Darby-King A, Grimes MT, Howland JG, Wang YT, McLean JH, Harley CW. Odor preference learning and memory modify GluA1 phosphorylation and GluA1 distribution in the neonate rat olfactory bulb: testing the AMPA receptor hypothesis in an appetitive learning model. Learn Mem 2011; 18:283-91. [PMID: 21498562 DOI: 10.1101/lm.1987711] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
An increase in synaptic AMPA receptors is hypothesized to mediate learning and memory. AMPA receptor increases have been reported in aversive learning models, although it is not clear if they are seen with memory maintenance. Here we examine AMPA receptor changes in a cAMP/PKA/CREB-dependent appetitive learning model: odor preference learning in the neonate rat. Rat pups were given a single pairing of peppermint and 2 mg/kg isoproterenol, which produces a 24-h, but not a 48-h, peppermint preference in the 7-d-old rat pup. GluA1 PKA-dependent phosphorylation peaked 10 min after the 10-min training trial and returned to baseline within 90 min. At 24 h, GluA1 subunits did not change overall but were significantly increased in synaptoneurosomes, consistent with increased membrane insertion. Immunohistochemistry revealed a significant increase in GluA1 subunits in olfactory bulb glomeruli, the targets of olfactory nerve axons. Glomerular increases were seen at 3 and 24 h after odor exposure in trained pups, but not in control pups. GluA1 increases were not seen as early as 10 min after training and were no longer observed 48 h after training when odor preference is no longer expressed behaviorally. Thus, the pattern of increased GluA1 membrane expression closely follows the memory timeline. Further, blocking GluA1 insertion using an interference peptide derived from the carboxyl tail of the GluA1 subunit inhibited 24 h odor preference memory providing causative support for our hypothesis. PKA-mediated GluA1 phosphorylation and later GluA1 insertion could, conjointly, provide increased AMPA function to support both short-term and long-term appetitive memory.
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Affiliation(s)
- Wen Cui
- Division of BioMedical Sciences, Memorial University of Newfoundland, St. John's NL, A1B 3V6 Canada
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30
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Vučković MG, Li Q, Fisher B, Nacca A, Leahy RM, Walsh JP, Mukherjee J, Williams C, Jakowec MW, Petzinger GM. Exercise elevates dopamine D2 receptor in a mouse model of Parkinson's disease: in vivo imaging with [¹⁸F]fallypride. Mov Disord 2011; 25:2777-84. [PMID: 20960487 DOI: 10.1002/mds.23407] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The purpose of the current study was to examine changes in dopamine D2 receptor (DA-D2R) expression within the basal ganglia of MPTP mice subjected to intensive treadmill exercise. Using Western immunoblotting analysis of synaptoneurosomes and in vivo positron emission tomography (PET) imaging employing the DA-D2R specific ligand [¹⁸F]fallypride, we found that high intensity treadmill exercise led to an increase in striatal DA-D2R expression that was most pronounced in MPTP compared to saline treated mice. Exercise-induced changes in the DA-D2R in the dopamine-depleted basal ganglia are consistent with the potential role of this receptor in modulating medium spiny neurons (MSNs) function and behavioral recovery. Importantly, findings from this study support the rationale for using PET imaging with [¹⁸F]fallypride to examine DA-D2R changes in individuals with Parkinson's Disease (PD) undergoing high-intensity treadmill training.
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Affiliation(s)
- Marta G Vučković
- Neuroscience Graduate Program, University of Southern California, Los Angeles, California, USA
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31
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Central insulin resistance and synaptic dysfunction in intracerebroventricular-streptozotocin injected rodents. Neurobiol Aging 2011; 33:430.e5-18. [PMID: 21256630 DOI: 10.1016/j.neurobiolaging.2010.12.002] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2010] [Revised: 11/22/2010] [Accepted: 12/07/2010] [Indexed: 11/24/2022]
Abstract
To better understand the role of insulin signaling in the development of Alzheimer's disease (AD), we utilized an animal model (intracerebroventricular injection of streptozotocin-ic-streptozotocin (STZ)) that displays insulin resistance only in the brain and exhibits AD pathology. In this model, deficits in hippocampal synaptic transmission and long-term potentiation (LTP) were observed. The decline in LTP correlated with decreased expression of NMDAR subunits NR2A and NR2B. The deficits in LTP were accompanied by changes in the expression and function of synaptic AMPARs. In ic-STZ animals, an alteration in integrin-linked kinase (ILK)-glycogen synthase kinase 3 beta (GSK-3-β) signaling was identified (p < 0.05). Similarly, there was decreased expression (p < 0.05) of brain derived neurotropic factor (BDNF) and stargazin, an AMPAR auxiliary subunit; both are required for driving AMPA receptors to the surface of the postsynaptic membrane. Our data illustrate that altered ILK-GSK-3β signaling due to impaired insulin signaling may decrease the trafficking and function of postsynaptic glutamate receptors; thereby, leading to synaptic deficits contributing to memory loss.
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32
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VanLeeuwen JE, Petzinger GM, Walsh JP, Akopian GK, Vuckovic M, Jakowec MW. Altered AMPA receptor expression with treadmill exercise in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-lesioned mouse model of basal ganglia injury. J Neurosci Res 2010; 88:650-68. [PMID: 19746427 DOI: 10.1002/jnr.22216] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Dopamine depletion leads to impaired motor performance and increased glutamatergic-mediated hyperexcitability of medium spiny neurons in the basal ganglia. Intensive treadmill exercise improves motor performance in both saline treatment and the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of Parkinson's disease. In the present study, we investigated the effect of high-intensity treadmill exercise on changes in alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) subunit expression, because these receptor channels confer the majority of fast excitatory neurotransmission in the brain, and their subunit composition provides a key mechanism for regulating synaptic strength and synaptic neuroplasticity and is important in modulating glutamatergic neurotransmission. Within the dorsolateral striatum of MPTP mice, treadmill exercise increased GluR2 subunit expression, with no significant effect on GluR1. Furthermore, neurophysiological studies demonstrated a reduction in the size of excitatory postsynaptic currents (EPSCs) in striatal medium spiny neurons (as determined by the input-output relationship), reduced amplitude of spontaneous EPSCs, and a loss of polyamine-sensitive inward rectification, all supportive of an increase in heteromeric AMPAR channels containing the GluR2 subunit. Phosphorylation of GluR2 at serine 880 in both saline-treated and MPTP mice suggests that exercise may also influence AMPAR trafficking and thus synaptic strength within the striatum. Finally, treadmill exercise also altered flip isoforms of GluR2 and GluR1 mRNA transcripts. These findings suggest a role for AMPARs in mediating the beneficial effects of exercise and support the idea that adaptive changes in GluR2 subunit expression may be important in modulating experience-dependent neuroplasticity of the injured basal ganglia.
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Affiliation(s)
- Jon-Eric VanLeeuwen
- Department of Neurology, The George and MaryLou Boone Center for Parkinson's Disease Research, University of Southern California, Los Angeles, California 90033, USA
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33
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Armstrong CL, Chung SH, Armstrong JN, Hochgeschwender U, Jeong YG, Hawkes R. A novel somatostatin-immunoreactive mossy fiber pathway associated with HSP25-immunoreactive purkinje cell stripes in the mouse cerebellum. J Comp Neurol 2009; 517:524-38. [PMID: 19795496 DOI: 10.1002/cne.22167] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Somatostatin 28 immunoreactivity (Sst28-ir) identifies a specific subset of mossy fiber terminals in the adult mouse cerebellum. By using double-labeling immunohistochemistry, we determined that Sst28-ir is associated with presynaptic mossy fiber terminal rosettes, and not Purkinje cells, Golgi cells, or unipolar brush cells. Sst28-ir mossy fibers are restricted to the central zone (lobules VI/VII) and nodular zone (lobules IX, X) of the vermis, and the paraflocculus and flocculus. Within each transverse zone the mossy fiber terminal fields form a reproducible array of parasagittal stripes. The boundaries of Sst28-ir stripes align with a specific array of Purkinje cell stripes revealed by using immunocytochemistry for the small heat shock protein HSP25. In the cerebellum of the homozygous weaver mouse, in which a subpopulation of HSP25-ir Purkinje cells are located ectopically, the corresponding Sst28-ir mossy fiber projection is also ectopic, suggesting a role for a specific Purkinje cell subset in afferent pattern formation. Likewise, in the scrambler mutant mouse, Sst28-ir mossy fibers show a very close association with HSP25-ir Purkinje cell clusters. HSP25 itself does not appear to be critical for normal patterning, however: in the KJR mouse, which does not express cerebellar HSP25, Sst28 expression appears to be normal. Likewise, the Purkinje cell patterning antigens zebrin II and HSP25 are expressed normally in both Sst- and Sst-receptor knockout mice, suggesting that somatostatinergic transmission is not necessary for Purkinje cell stripe formation.
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Affiliation(s)
- C L Armstrong
- Department of Biomedical Science, Ontario Veterinary College, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
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Watson JB, Hatami A, David H, Masliah E, Roberts K, Evans CE, Levine MS. Alterations in corticostriatal synaptic plasticity in mice overexpressing human alpha-synuclein. Neuroscience 2009; 159:501-13. [PMID: 19361478 DOI: 10.1016/j.neuroscience.2009.01.021] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2008] [Revised: 01/10/2009] [Accepted: 01/13/2009] [Indexed: 11/28/2022]
Abstract
Most forms of Parkinson's disease (PD) are sporadic in nature, but some have genetic causes as first described for the alpha-synuclein gene. The alpha-synuclein protein also accumulates as insoluble aggregates in Lewy bodies in sporadic PD as well as in most inherited forms of PD. The focus of the present study is the modulation of synaptic plasticity in the corticostriatal pathway of transgenic (Tg) mice that overexpress the human alpha-synuclein protein throughout the brain (ASOTg). Paired-pulse facilitation was detected in vitro by activation of corticostriatal afferents in ASOTg mice, consistent with a presynaptic effect of elevated human alpha-synuclein. However basal synaptic transmission was unchanged in ASOTg, suggesting that human alpha-synuclein could impact paired-pulse facilitation via a presynaptic mechanism not directly related to the probability of neurotransmitter release. Mice lacking alpha-synuclein or those expressing normal and A53T human alpha-synuclein in tyrosine hydroxylase-containing neurons showed, instead, paired-pulse depression. High-frequency stimulation induced a presynaptic form of long-term depression solely in ASOTg striatum. A presynaptic, N-methyl-d-aspartate receptor-independent form of chemical long-term potentiation induced by forskolin (FSK) was enhanced in ASOTg striatum, while FSK-induced cAMP levels were reduced in ASOTg synaptoneurosome fractions. Overall the results suggest that elevated human alpha-synuclein alters presynaptic plasticity in the corticostriatal pathway, possibly reflecting a reduction in glutamate at corticostriatal synapses by modulation of adenylyl cyclase signaling pathways. ASOTg mice may recapitulate an early stage in PD during which overexpressed alpha-synuclein dampens corticostriatal synaptic transmission and reduces movement.
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Affiliation(s)
- J B Watson
- Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
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35
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Transcriptome analysis of synaptoneurosomes identifies neuroplasticity genes overexpressed in incipient Alzheimer's disease. PLoS One 2009; 4:e4936. [PMID: 19295912 PMCID: PMC2654156 DOI: 10.1371/journal.pone.0004936] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2008] [Accepted: 01/15/2009] [Indexed: 11/21/2022] Open
Abstract
In Alzheimer's disease (AD), early deficits in learning and memory are a consequence of synaptic modification induced by toxic beta-amyloid oligomers (oAβ). To identify immediate molecular targets downstream of oAβ binding, we prepared synaptoneurosomes from prefrontal cortex of control and incipient AD (IAD) patients, and isolated mRNAs for comparison of gene expression. This novel approach concentrates synaptic mRNA, thereby increasing the ratio of synaptic to somal mRNA and allowing discrimination of expression changes in synaptically localized genes. In IAD patients, global measures of cognition declined with increasing levels of dimeric Aβ (dAβ). These patients also showed increased expression of neuroplasticity related genes, many encoding 3′UTR consensus sequences that regulate translation in the synapse. An increase in mRNA encoding the GluR2 subunit of the α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor (AMPAR) was paralleled by elevated expression of the corresponding protein in IAD. These results imply a functional impact on synaptic transmission as GluR2, if inserted, maintains the receptors in a low conductance state. Some overexpressed genes may induce early deficits in cognition and others compensatory mechanisms, providing targets for intervention to moderate the response to dAβ.
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36
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Wijayawardhane N, Shonesy BC, Vaithianathan T, Pandiella N, Vaglenova J, Breese CR, Dityatev A, Suppiramaniam V. Ameliorating effects of preadolescent aniracetam treatment on prenatal ethanol-induced impairment in AMPA receptor activity. Neurobiol Dis 2007; 29:81-91. [PMID: 17916430 DOI: 10.1016/j.nbd.2007.08.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2007] [Revised: 08/02/2007] [Accepted: 08/06/2007] [Indexed: 11/25/2022] Open
Abstract
Ethanol-induced damage in the developing hippocampus may result in cognitive deficits such as those observed in fetal alcohol spectrum disorder (FASD). Cognitive deficits in FASD are partially mediated by alterations in glutamatergic synaptic transmission. Recently, we reported that synaptic transmission mediated by alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) is impaired following fetal ethanol exposure. This finding led us to develop a rational approach for the treatment of alcohol-related cognitive deficits using aniracetam, an allosteric AMPAR modulator. In the present study, 28 to 34-day-old rats exposed to ethanol in utero were treated with aniracetam, and subsequently exhibited persistent improvement in mEPSC amplitude, frequency, and decay time. Furthermore, these animals expressed positive changes in synaptic single channel properties, suggesting that aniracetam ameliorates prenatal ethanol-induced deficits through modifications at the single channel level. Specifically, single channel open probability, conductance, mean open and closed times, and the number and burst duration were positively affected. Our findings emphasize the utility of compounds which slow the rate of deactivation and desensitization of AMPARs such as aniracetam.
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Affiliation(s)
- Nayana Wijayawardhane
- Department of Pharmacal Sciences, 401 Walker Building, Harrison School of Pharmacy, Auburn University, Auburn, AL 36849, USA
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Hu XD, Huang Q, Yang X, Xia H. Differential regulation of AMPA receptor trafficking by neurabin-targeted synaptic protein phosphatase-1 in synaptic transmission and long-term depression in hippocampus. J Neurosci 2007; 27:4674-86. [PMID: 17460080 PMCID: PMC6672995 DOI: 10.1523/jneurosci.5365-06.2007] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Filamentous actin binding protein neurabin I (NrbI) targets protein phosphatase-1 (PP1) to specific postsynaptic microdomains, exerting critical control over AMPA receptor (AMPAR)-mediated synaptic transmission. NrbI-targeted synaptic PP1, which promotes synaptic depression upon long-term depression (LTD) stimuli, serves to prevent synaptic depression under basal conditions. The present studies investigate this opposite regulation of AMPAR trafficking during basal synaptic transmission and LTD by expressing NrbI or NrbI mutant, which is defective in PP1 binding, in hippocampal slice or neuron cultures. We find that expression of the NrbI mutant to interfere with PP1 targeting dramatically reduces basal synaptic transmission, which is correlated with the reduction in surface expression of AMPA subtype glutamate receptor (GluR) 1 and GluR2 subunits. Biochemical analysis demonstrates that the NrbI mutant selectively increases the phosphorylation of GluR2 at C-terminal consensus PKC site, serine 880, which is known to favor GluR2 interaction with PDZ (postsynaptic density 95/Discs large/zona occludens 1) protein PICK1 (protein interacting with C kinase-1). Inhibition of PKC activity or GluR2-PICK1 interaction completely reverses the synaptic depression in neurons expressing the NrbI mutant, suggesting that NrbI-targeted synaptic PP1 stabilizes the basal transmission by negatively controlling PKC phosphorylation of GluR2 and the subsequent PICK1-mediated decrease in GluR2-containing AMPAR surface expression. Distinct from basal transmission, blocking GluR2-PICK1 interaction or PKC activity produces minimal effects on LTD in NrbI-expressing neurons. Instead, NrbI-targeted PP1 facilitates LTD by dephosphorylating GluR1 at both serine 845 and serine 831, with GluR2 serine 880 phosphorylation unaltered. Our studies thus elucidate that NrbI-targeted PP1, in response to distinct synaptic activities, regulates the synaptic trafficking of specific AMPAR subunits.
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Affiliation(s)
- Xiao-dong Hu
- Neuroscience Center of Excellence, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112
| | - Qing Huang
- Neuroscience Center of Excellence, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112
| | - Xian Yang
- Neuroscience Center of Excellence, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112
| | - Houhui Xia
- Neuroscience Center of Excellence, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112
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Watson JB, Arnold MM, Ho YS, O'Dell TJ. Age-dependent modulation of hippocampal long-term potentiation by antioxidant enzymes. J Neurosci Res 2007; 84:1564-74. [PMID: 16941635 DOI: 10.1002/jnr.21040] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Oxidative stress has long been associated with normal aging and age-related neurodegenerative disorders such as Alzheimer's disease (AD) and Parkinson's disease (PD). However, it is now evident that reactive oxygen species (ROS) such as superoxide (O(2-*)) and hydrogen peroxide (H(2)O(2)) also play pivotal roles in normal cell signaling. The focus of the present study was to examine the effects of the antioxidant enzymes CuZnSOD (SOD1) and catalase, which produce and remove H(2)O(2), respectively, on long-term potentiation (LTP) forms of synaptic plasticity during aging. Consistent wth previous studies, LTP, when induced in vitro in CA1 of the hippocampus with a high-frequency stimulation protocol, is significantly reduced in slices from older mice (22-26 months) relative to younger mice (2-4 months). Neither knockout of the endogenous catalase gene (Cat KO) nor acute enzymatic treatment with SOD1 altered LTP in slices from adult mice. Conversely, enzymatic applications of SOD1 inhibited LTP in slices from older mice. A much different set of results emerges with exogenous applications of catalase to hippocampal slices. Catalase significantly inhibited LTP in slices from adult mice but reversed age-related LTP deficits in slices from older mice. Measurements of H(2)O(2) showed that exogenous treatments with catalase lowered H(2)O(2) in synapse-enriched synaptoneurosome (SN) fractions prepared from adult mice. Notably, SNs from both Cat KO and old mice were deficient in removing extracellular challenges of H(2)O(2). Overall, the results suggest that dynamic alterations in extracellular H(2)O(2) metabolism affect synaptic plasticity in the hippocampus during aging.
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Affiliation(s)
- J B Watson
- Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine at UCLA, Los Angeles, California 90095, USA.
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Parameshwaran K, Sims C, Kanju P, Vaithianathan T, Shonesy BC, Dhanasekaran M, Bahr BA, Suppiramaniam V. Amyloid β-peptide Aβ1–42 but not Aβ1–40 attenuates synaptic AMPA receptor function. Synapse 2007; 61:367-74. [PMID: 17372971 DOI: 10.1002/syn.20386] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The brains of Alzheimer's disease (AD) patients have large numbers of plaques that contain amyloid beta (Abeta) peptides which are believed to play a pivotal role in AD pathology. Several lines of evidence have established the inhibitory role of Abeta peptides on hippocampal memory encoding, a process that relies heavily on alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor function. In this study the modulatory effects of the two major Abeta peptides, Abeta(1-40) and Abeta(1-42), on synaptic AMPA receptor function was investigated utilizing the whole cell patch clamp technique and analyses of single channel properties of synaptic AMPA receptors. Bath application of Abeta(1-42) but not Abeta(1-40) reduced both the amplitude and frequency of AMPA receptor mediated excitatory postsynaptic currents in hippocampal CA1 pyramidal neurons by approximately 60% and approximately 45%, respectively, in hippocampal CA1 pyramidal neurons. Furthermore, experiments with single synaptic AMPA receptors reconstituted in artificial lipid bilayers showed that Abeta(1-42) reduced the channel open probability by approximately 42% and channel open time by approximately 65% and increased the close times by several fold. Abeta(1-40), however, did not show such inhibitory effects on single channel properties. Application of the reverse sequence peptide Abeta(42-1) also did not alter the mEPSC or single channel properties. These results suggest that Abeta(1-42) but not Abeta(1-40) closely interacts with and exhibits inhibitory effects on synaptic AMPA receptors and may contribute to the memory impairment observed in AD.
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Affiliation(s)
- Kodeeswaran Parameshwaran
- Department of Pharmacal Sciences, Harrison School of Pharmacy, Auburn University, Auburn, AL 36849, USA
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40
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Hammond MSL, Sims C, Parameshwaran K, Suppiramaniam V, Schachner M, Dityatev A. Neural Cell Adhesion Molecule-associated Polysialic Acid Inhibits NR2B-containing N-Methyl-d-aspartate Receptors and Prevents Glutamate-induced Cell Death. J Biol Chem 2006; 281:34859-69. [PMID: 16987814 DOI: 10.1074/jbc.m602568200] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The neural cell adhesion molecule (NCAM) and its associated glycan polysialic acid play important roles in the development of the nervous system and N-methyl-D-aspartate(NMDA)receptor-dependent synaptic plasticity in the adult. Here, we investigated the influence of polysialic acid on NMDA receptor activity. We found that glutamate-elicited NMDA receptor currents in cultured hippocampal neurons were reduced by approximately 30% with the application of polysialic acid or polysialylated NCAM but not by the sialic acid monomer, chondroitin sulfate, or non-polysialylated NCAM. Polysialic acid inhibited NMDA receptor currents elicited by 3 microm glutamate but not by 30 microm glutamate, suggesting that polysialic acid acts as a competitive antagonist, possibly at the glutamate binding site. The polysialic acid induced effects were mimicked and fully occluded by the NR2B subunit specific antagonist, ifenprodil. Recordings from single synaptosomal NMDA receptors reconstituted in lipid bilayers revealed that polysialic acid reduced open probability but not the conductance of NR2B-containing NMDA receptors in a polysialic acid and glutamate concentration-dependent manner. The activity of single NR2B-lacking synaptosomal NMDA receptors was not affected by polysialic acid. Application of polysialic acid to hippocampal cultures reduced excitotoxic cell death induced by low micromolar concentration of glutamate via activation of NR2B-containing NMDA receptors, whereas enzymatic removal of polysialic acid resulted in increased cell death that occluded glutamate-induced excitotoxicity. These observations indicate that the cell adhesion molecule-associated glycan polysialic acid is able to prevent excitotoxicity via inhibition of NR2B subunit-containing NMDA receptors.
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Affiliation(s)
- Martin S L Hammond
- Zentrum für Molekulare Neurobiologie Hamburg and Institut für Neurophysiologie und Pathophysiologie, Universitätsklinikum Hamburg-Eppendorf, 20246 Hamburg, Germany
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41
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Giza CC, Maria NSS, Hovda DA. N-methyl-D-aspartate receptor subunit changes after traumatic injury to the developing brain. J Neurotrauma 2006; 23:950-61. [PMID: 16774479 PMCID: PMC2531140 DOI: 10.1089/neu.2006.23.950] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Traumatic brain injury (TBI) is a major cause of disability in the pediatric population and can result in abnormal development. Experimental studies conducted in animals have revealed impaired plasticity following developmental TBI, even in the absence of significant anatomical damage. The N-methyl-D-aspartate receptor (NMDAR) is clearly involved in both normal development and in the pathophysiology of TBI. Following lateral fluid percussion injury in postnatal day (PND) 19 rats, we tested the hypothesis that TBI sustained at an early age would result in impaired NMDAR expression. Using immunoblotting and reverse transcriptase-polymerase chain reaction (RT-PCR), protein and RNA levels of NMDAR subunits were measured in the cerebral cortex and hippocampus on post-injury days (PID) 1, 2, 4, and 7 (though the PID7 analysis was only for protein) and compared with age-matched shams. Significant effects of hemisphere (analysis of variance [ANOVA], p<0.01), and interactions between hemisphere and injury (ANOVA, p<0.05) and hemisphere and PID (ANOVA, p<0.05) were found for synaptic protein levels of the NR2A subunit in hippocampus. Specifically, within the ipsilateral hippocampus, NR2A was reduced by 9.9%, 47.9%, 40.8%, and 6.3% on PID1, PID2, PID4, and PID7, respectively. Within the cortex, there was a significant effect of injury (ANOVA, p<0.05) without any hemispheric differences. These bilateral cortical reductions measured 30.5%, 3.2%, 5.7%, and 13.4% at the same timepoints after injury. Injury had no significant main effect on NR1 or NR2B protein levels. RT-PCR analysis showed no significant changes in NR1, NR2A, or NR2B gene expression; however, as a positive control, hsp70 was induced more than twofold in ipsilateral cortex and hippocampus on PID1. It is known that NR2A expression levels increase during normal development, and in response to environmental stimuli. Our data suggest that injury-induced reduction in the expression of NR2A is one likely mechanism for the impaired experience-dependent neuroplasticity seen following traumatic injury to the immature brain.
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Affiliation(s)
- Christopher C Giza
- UCLA Brain Injury Research Center, Division of Neurosurgery/Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, California 90095, USA.
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Villasana LE, Klann E, Tejada-Simon MV. Rapid isolation of synaptoneurosomes and postsynaptic densities from adult mouse hippocampus. J Neurosci Methods 2006; 158:30-6. [PMID: 16797717 PMCID: PMC2014514 DOI: 10.1016/j.jneumeth.2006.05.008] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2006] [Revised: 05/02/2006] [Accepted: 05/04/2006] [Indexed: 10/24/2022]
Abstract
Previous postsynaptic density (PSD) isolation methodologies have utilized either whole brain or discrete brain regions of relatively large mammals such as dogs and rats. The present report details a simple and highly effective procedure for the rapid isolation of PSDs from small amounts of adult mouse hippocampus that has several advantages. First, by substituting synaptoneurosomes for synaptosomes as starting material, we have decreased the steps, time, and amount of tissue required to isolate PSDs. Second, by modifying critical steps in the synaptic isolation protocols we were able to isolate PSDs from less than 200 mg of mouse hippocampi in 3 h. Electron micrographs of isolated synaptoneurosomes showed presynaptic vesicles and densely stained membranes representing PSDs. Morphological examination of these PSDs by electron microscopy revealed a preparation that seems to be quite pure, with little or no membrane contamination. A comparison by Western blot analysis of synaptoneurosome and PSD fractions suggests that this technique yields a purified sample. Moreover, two different protocols using swing and fixed bucket rotors were used for this small-scale PSD isolation and both resulted in a very pure partition, supporting the idea that this procedure is reliable and consistent.
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Affiliation(s)
- Laura Elena Villasana
- Department of Molecular Physiology & Biophysics, Baylor College of Medicine, Houston, TX, USA
| | - Eric Klann
- Department of Molecular Physiology & Biophysics, Baylor College of Medicine, Houston, TX, USA
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Maria Victoria Tejada-Simon
- Department of Molecular Physiology & Biophysics, Baylor College of Medicine, Houston, TX, USA
- * Correspondence to: Department of Molecular Physiology and Biophysics, One Baylor Plaza, 413B, Houston, TX 77030, USA. Tel.: +1 713 798 5618; fax: +1 713 798 3475. E-mail address: (M.V. Tejada-Simon)
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Shumyatsky GP, Malleret G, Shin RM, Takizawa S, Tully K, Tsvetkov E, Zakharenko SS, Joseph J, Vronskaya S, Yin D, Schubart UK, Kandel ER, Bolshakov VY. stathmin, a gene enriched in the amygdala, controls both learned and innate fear. Cell 2006; 123:697-709. [PMID: 16286011 DOI: 10.1016/j.cell.2005.08.038] [Citation(s) in RCA: 174] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2005] [Revised: 06/17/2005] [Accepted: 08/26/2005] [Indexed: 11/18/2022]
Abstract
Little is known about the molecular mechanisms of learned and innate fear. We have identified stathmin, an inhibitor of microtubule formation, as highly expressed in the lateral nucleus (LA) of the amygdala as well as in the thalamic and cortical structures that send information to the LA about the conditioned (learned fear) and unconditioned stimuli (innate fear). Whole-cell recordings from amygdala slices that are isolated from stathmin knockout mice show deficits in spike-timing-dependent long-term potentiation (LTP). The knockout mice also exhibit decreased memory in amygdala-dependent fear conditioning and fail to recognize danger in innately aversive environments. By contrast, these mice do not show deficits in the water maze, a spatial task dependent on the hippocampus, where stathmin is not normally expressed. We therefore conclude that stathmin is required for the induction of LTP in afferent inputs to the amygdala and is essential in regulating both innate and learned fear.
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Affiliation(s)
- Gleb P Shumyatsky
- Department of Genetics, Rutgers University, Piscataway, New Jersey 08854, USA.
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Ho OH, Delgado JY, O'Dell TJ. Phosphorylation of proteins involved in activity-dependent forms of synaptic plasticity is altered in hippocampal slices maintained in vitro. J Neurochem 2005; 91:1344-57. [PMID: 15584911 DOI: 10.1111/j.1471-4159.2004.02815.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The acute hippocampal slice preparation has been widely used to study the cellular mechanisms underlying activity-dependent forms of synaptic plasticity such as long-term potentiation (LTP) and long-term depression (LTD). Although protein phosphorylation has a key role in LTP and LTD, little is known about how protein phosphorylation might be altered in hippocampal slices maintained in vitro. To begin to address this issue, we examined the effects of slicing and in vitro maintenance on phosphorylation of six proteins involved in LTP and/or LTD. We found that AMPA receptor (AMPAR) glutamate receptor 1 (GluR1) subunits are persistently dephosphorylated in slices maintained in vitro for up to 8 h. alpha calcium/calmodulin-dependent kinase II (alphaCamKII) was also strongly dephosphorylated during the first 3 h in vitro but thereafter recovered to near control levels. In contrast, phosphorylation of the extracellular signal-regulated kinase ERK2, the ERK kinase MEK, proline-rich tyrosine kinase 2 (Pyk2), and Src family kinases was significantly, but transiently, increased. Electrophysiological experiments revealed that the induction of LTD by low-frequency synaptic stimulation was sensitive to time in vitro. These findings indicate that phosphorylation of proteins involved in N-methyl-D-aspartate (NMDA) receptor-dependent forms of synaptic plasticity is altered in hippocampal slices and suggest that some of these changes can significantly influence the induction of LTD.
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Affiliation(s)
- Oanh H Ho
- Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095, USA
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45
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Gylys KH, Fein JA, Yang F, Wiley DJ, Miller CA, Cole GM. Synaptic changes in Alzheimer's disease: increased amyloid-beta and gliosis in surviving terminals is accompanied by decreased PSD-95 fluorescence. THE AMERICAN JOURNAL OF PATHOLOGY 2004; 165:1809-17. [PMID: 15509549 PMCID: PMC1618663 DOI: 10.1016/s0002-9440(10)63436-0] [Citation(s) in RCA: 183] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
In an effort to examine changes that precede synapse loss, we have measured amyloid-beta and a series of damage markers in the synaptic compartment of Alzheimer's disease (AD) cases. Because localization of events to the terminal region in neurons is problematic with conventional methods, we prepared synaptosomes from samples of cryopreserved human association cortex, and immunolabeled terminals with a procedure for intracellular antigens. Fluorescence was quantified using flow cytometry. The viability dye calcein AM was unchanged in AD terminals compared to controls, and the fraction of large synaptosome particles did not change, although a striking loss of large terminals was observed in some AD cases. The percent positive fraction for a series of pre- and postsynaptic markers was not affected by AD in this cohort. However, the amyloid-beta-positive fraction increased from 16 to 27% (P < 0.02) in terminals from AD cortex. The expression level on a per-terminal basis is indicated in this assay by fluorescence (relative fluorescence units). The fluorescence of presynaptic markers did not change in AD terminals, but PSD-95 fluorescence was decreased by 19% (P < 0.03). Amyloid-beta fluorescence was increased by 132% (P < 0.01), and glial fibrillary acidic protein labeling by 31% (P < 0.01). These results suggest that synapse-associated amyloid-beta is prominent in regions relatively unaffected by AD lesions, and that amyloid accumulation in surviving terminals is accompanied by gliosis and alteration in the postsynaptic structure.
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Affiliation(s)
- Karen Hoppens Gylys
- UCLA School of Nursing and Brain Research Institute, Box 956919 Factor Bldg., Los Angeles, CA 90095-6919, USA.
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46
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Hou L, Klann E. Activation of the phosphoinositide 3-kinase-Akt-mammalian target of rapamycin signaling pathway is required for metabotropic glutamate receptor-dependent long-term depression. J Neurosci 2004; 24:6352-61. [PMID: 15254091 PMCID: PMC6729543 DOI: 10.1523/jneurosci.0995-04.2004] [Citation(s) in RCA: 408] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Hippocampal long-term depression (LTD) is a long-lasting decrease in synaptic strength that is most commonly studied at glutamatergic inputs to pyramidal cells in hippocampal area CA1. Activation of G-protein-coupled group I (including types 1 and 5) metabotropic glutamate receptors (mGluRs) by the pharmacological agonist (RS)-3,5-dihydroxyphenylglycine (DHPG) elicits LTD in area CA1 of the hippocampus. Recent reports have shown that de novo protein synthesis is necessary for DHPG-induced LTD. However, relatively little is known about the signaling pathways that couple mGluRs to translation initiation. In this study, we investigated whether the activation of the phosphoinositide 3-kinase (PI3K)-Akt-mammalian target of rapamycin (mTOR) pathway, which has been shown to regulate translation initiation, is necessary for mGluR-LTD induced by DHPG. We found that brief incubations of mouse hippocampal slices with DHPG resulted in increased phosphorylation of Akt and mTOR in hippocampal area CA1. Two structurally unrelated PI3K inhibitors, LY294002 and wortmannin, blocked the DHPG-induced increases in phosphorylation of Akt and mTOR. Biochemical fractionation studies showed that the DHPG-induced increase in the phosphorylation of Akt and mTOR could be detected in synaptoneurosome preparations, and immunohistochemical analysis revealed that similar increases could be detected in both stratum pyramidale and stratum radiatum in area CA1. Finally, we observed that both PI3K inhibitors and rapamycin, an mTOR inhibitor, prevented mGluR-LTD induced by DHPG. Together, our findings indicate that activation of the PI3K-Akt-mTOR signaling cascade is required for mGluR-LTD and suggest that this pathway may couple group I mGluRs to translation initiation in hippocampal area CA1.
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Affiliation(s)
- Lingfei Hou
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas 77030, USA
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Hayashi ML, Choi SY, Rao BSS, Jung HY, Lee HK, Zhang D, Chattarji S, Kirkwood A, Tonegawa S. Altered cortical synaptic morphology and impaired memory consolidation in forebrain- specific dominant-negative PAK transgenic mice. Neuron 2004; 42:773-87. [PMID: 15182717 DOI: 10.1016/j.neuron.2004.05.003] [Citation(s) in RCA: 231] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2004] [Revised: 04/23/2004] [Accepted: 05/06/2004] [Indexed: 11/18/2022]
Abstract
Molecular and cellular mechanisms for memory consolidation in the cortex are poorly known. To study the relationships between synaptic structure and function in the cortex and consolidation of long-term memory, we have generated transgenic mice in which catalytic activity of PAK, a critical regulator of actin remodeling, is inhibited in the postnatal forebrain. Cortical neurons in these mice displayed fewer dendritic spines and an increased proportion of larger synapses compared to wild-type controls. These alterations in basal synaptic morphology correlated with enhanced mean synaptic strength and impaired bidirectional synaptic modifiability (enhanced LTP and reduced LTD) in the cortex. By contrast, spine morphology and synaptic plasticity were normal in the hippocampus of these mice. Importantly, these mice exhibited specific deficits in the consolidation phase of hippocampus-dependent memory. Thus, our results provide evidence for critical relationships between synaptic morphology and bidirectional modifiability of synaptic strength in the cortex and consolidation of long-term memory.
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Affiliation(s)
- Mansuo L Hayashi
- The Picower Center for Learning and Memory, Howard Hughes Medical Institute, RIKEN-MIT Neuroscience Research Center, Center for Cancer Research, Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Gylys KH, Fein JA, Yang F, Cole GM. Enrichment of presynaptic and postsynaptic markers by size-based gating analysis of synaptosome preparations from rat and human cortex. ACTA ACUST UNITED AC 2004; 60:90-6. [PMID: 15229861 DOI: 10.1002/cyto.a.20031] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
BACKGROUND Synapse regions in the brain are difficult to isolate and study; resealed nerve terminals (synaptosomes) are a widely used in vitro system for the study of neurotransmission, but nonsynaptosomal elements in the homogenate complicate data interpretation. With the goal of quantitative analysis of pathways leading to synapse loss in neurodegenerative disease, we have developed a method that allows focus on the intact synaptosomes within a crude synaptosomal preparation by gating the largest particles based on forward angle light scatter (FSC). METHODS Crude synaptosomal fractions (P-2) were prepared and labeled with a viability dye (calcein AM), a presynaptic marker (SNAP-25), and a postsynaptic marker (PSD-95). Forward scatter gates based on size standards were drawn to identify the large population (1.4-4.5 microm), and the enrichment of each marker was quantified in preparations from fresh rat homogenates and from cryopreserved human cortex. RESULTS Gating on forward scatter resulted in an increase that was highly significant (P < 0.001) for all three markers examined. The calcein-AM-positive fraction in the large synaptosomes was 98% +/- 0.8, and 75% +/- 9.8 for rat and human, respectively. Of large particles, 90% +/- 2.7 in rat and 82% +/- 2.6 in human were positive for SNAP-25, indicating a relatively pure population of intact synaptosomes. A total of 76% +/- 2.9 of the large particles were positive for PSD-95 in rat. This compared to 36% +/- 3.0 in human tissue, and indicates that both presynaptic and postsynaptic elements may be analyzed with this methodology. CONCLUSIONS Most nonsynaptosomal elements can be excluded and the intact subpopulation of interest within the P-2 can be identified based on size. Size-based gating analysis provides a simple and cost-effective method to monitor fluorescence changes in synapse regions.
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Affiliation(s)
- Karen H Gylys
- UCLA School of Nursing and Brain Research Institute, UCLA School of Medicine, Los Angeles, California 90095, USA.
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Townsend M, Yoshii A, Mishina M, Constantine-Paton M. Developmental loss of miniature N-methyl-D-aspartate receptor currents in NR2A knockout mice. Proc Natl Acad Sci U S A 2003; 100:1340-5. [PMID: 12552130 PMCID: PMC298774 DOI: 10.1073/pnas.0335786100] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The N-methyl-d-aspartate (NMDA) glutamate receptor (NMDAR), long implicated in developmental plasticity, shows decay time kinetics that shorten postnatally as NR2A subunits are added to the receptor. Neither the mechanism nor immediate effect of this change is known. We studied developing NMDAR currents by using visual neurons in slices from NR2A knockout (NR2AKO) and WT mice. Both strains show increased dendritic levels of synaptic density scaffolding protein PSD-95 with age. Dendritic levels of NR2A increased at the same time in WT and immunoprecipitated with PSD-95. PSD-95NMDAR binding was significantly decreased in the NR2AKO. Moreover, NMDAR miniature currents (minis) were lost and rise times of NMDAR evoked currents increased in mutant mice. Age-matched WT cells showed NR2A-rich receptors predominating in minis, yet slow NR2B mediated currents persisted in evoked currents. Disrupting photoreceptor activation of retinal ganglion cells eliminated increases in PSD-95 and NR2A in superior collicular dendrites of WT mice and slowed the loss of miniature NMDAR currents in NR2AKOs. These data demonstrate that NMDARs that respond to single quantal events mature faster during development by expressing the NR2A subunit earlier than NMDARs that respond to evoked release. We hypothesize that NR2A-rich NMDARs may be localized to the center of developing synapses by an activity-dependent process that involves the targeting of PSD-95 to the postsynaptic density. Neonatal receptors become restricted to perisynpatic or extrasynaptic sites, where they participate primarily in evoked currents.
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Affiliation(s)
- Matthew Townsend
- Interdepartmental Neuroscience Program, Yale University, New Haven, CT 06520, USA
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50
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Abstract
gamma-Hydroxybutyric acid (GHB) is a naturally occurring metabolite of GABA that has been postulated to exert ubiquitous neuropharmacological effects through GABA(B) receptor (GABA(B)R)-mediated mechanisms. The alternative hypothesis that GHB acts via a GHB-specific, G protein-coupled presynaptic receptor that is different from the GABA(B)R was tested. The effect of GHB on regional and subcellular brain adenylyl cyclase in adult and developing rats was determined and compared with that of the GABA(B)R agonist (-)-baclofen. Also, using guanosine 5'-O:-(3-[(35)S]thiotriphosphate) ([(35)S]GTPgammaS) binding and low-K:(m) GTPase activity as markers the effects of GHB and (-)-baclofen on G protein activity in the brain were determined. Neither GHB nor baclofen had an effect on basal cyclic AMP (cAMP) levels. GHB significantly decreased forskolin-stimulated cAMP levels by 40-50% in cortex and hippocampus but not thalamus or cerebellum, whereas (-)-baclofen had an effect throughout the brain. The effect of GHB on adenylyl cyclase was observed in presynaptic and not postsynaptic subcellular tissue preparations, but the effect of baclofen was observed in both subcellular preparations. The GHB-induced alteration in forskolin-induced cAMP formation was blocked by a specific GHB antagonist but not a specific GABA(B)R antagonist. The (-)-baclofen-induced alteration in forskolin-induced cAMP formation was blocked by a specific GABA(B)R antagonist but not a specific GHB antagonist. The negative coupling of GHB to adenylyl cyclase appeared at postnatal day 21, a developmental time point that is concordant with the developmental appearance of [(3)H]GHB binding in cerebral cortex, but the effects of (-)-baclofen were present by postnatal day 14. GHB and baclofen both stimulated [(35)S]GTPgammaS binding and low-K:(m) GTPase activity by 40-50%. The GHB-induced effect was blocked by GHB antagonists but not by GABA(B)R antagonists and was seen only in cortex and hippocampus. The (-)-baclofen-induced effect was blocked by GABA(B)R antagonists but not by GHB antagonists and was observed throughout the brain. These data support the hypothesis that GHB induces a G protein-mediated decrease in adenylyl cyclase via a GHB-specific G protein-coupled presynaptic receptor that is different from the GABA(B)R.
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Affiliation(s)
- O C Snead
- Department of Pediatrics, Faculty of Medicine, University of Toronto, Ontario, Canada.
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