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Cheron G, Ristori D, Marquez-Ruiz J, Cebolla AM, Ris L. Electrophysiological alterations of the Purkinje cells and deep cerebellar neurons in a mouse model of Alzheimer disease (electrophysiology on cerebellum of AD mice). Eur J Neurosci 2022; 56:5547-5563. [PMID: 35141975 DOI: 10.1111/ejn.15621] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Revised: 12/16/2021] [Accepted: 12/19/2021] [Indexed: 12/14/2022]
Abstract
Alzheimer's disease is histopathologically well defined by the presence of amyloid deposits and tau-related neurofibrillary tangles in crucial regions of the brain. Interest is growing in revealing and determining possible pathological markers also in the cerebellum as its involvement in cognitive functions is now well supported. Despite the central position of the Purkinje cell in the cerebellum, its electrophysiological behaviour in mouse models of Alzheimer's disease is scarce in the literature. Our first aim was here to focus on the electrophysiological behaviour of the cerebellum in awake mouse model of Alzheimer's disease (APPswe/PSEN1dE9) and the related performance on the water-maze test classically used in behavioural studies. We found prevalent signs of electrophysiological alterations in both Purkinje cells and deep cerebellar nuclei neurons which might explain the behavioural deficits reported during the water-maze test. The alterations of neurons firing were accompanied by a dual (~16 and ~228 Hz) local field potential's oscillation in the Purkinje cell layer of Alzheimer's disease mice which was concomitant to an important increase of both the simple and the complex spikes. In addition, β-amyloid deposits were present in the molecular layer of the cerebellum. These results highlight the importance of the output firing modification of the AD cerebellum that may indirectly impact the activity of its subcortical and cortical targets.
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Affiliation(s)
- Guy Cheron
- Laboratory of Neurophysiology and Movement Biomechanics, Université Libre de Bruxelles, Brussels, Belgium.,ULB Neuroscience Institut, Université Libre de Bruxelles, Brussels, Belgium.,Laboratory of Neuroscience, Université de Mons, Mons, Belgium
| | - Dominique Ristori
- Laboratory of Neurophysiology and Movement Biomechanics, Université Libre de Bruxelles, Brussels, Belgium
| | - Javier Marquez-Ruiz
- Department of Physiology, Anatomy and Cell Biology, Pablo de Olavide University, Seville, Spain
| | - Anna-Maria Cebolla
- Laboratory of Neurophysiology and Movement Biomechanics, Université Libre de Bruxelles, Brussels, Belgium
| | - Laurence Ris
- Laboratory of Neuroscience, Université de Mons, Mons, Belgium.,UMONS Research Institut for health and technology, Université de Mons, Mons, Belgium
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2
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Liu W, Lao W, Zhang R, Zhu H. Altered expression of voltage gated sodium channel Nav1.1 is involved in motor ability in MPTP-treated mice. Brain Res Bull 2021; 170:187-198. [PMID: 33610724 DOI: 10.1016/j.brainresbull.2021.02.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 01/12/2021] [Accepted: 02/16/2021] [Indexed: 11/25/2022]
Abstract
Parkinson's disease (PD) is a motor disabling disorder owing to the progressive degeneration of dopaminergic neurons in the substantia nigra (SN). The mechanisms causing motor deficits remain debated. High synchronized oscillations in the basal ganglia (BG) were proposed to be associated with motor symptoms in PD patients and animal models of PD. Voltage-gated sodium channels play a vital role in the initiation and propagation of action potentials. Here, we investigated the expression patterns of a VGSC subtype Nav1.1 in the BG of a PD animal model induced by MPTP intraperitoneal injection. The results showed that Nav1.1 was significantly reduced in tyrosine hydroxylase (TH) positive dopaminergic neurons of the SN. Moreover, Nav1.1 expression was significantly increased in calcium binding protein parvalbumin (PV) positive neurons of the globus pallidus (GP) in MPTP-treated mice compared to the rarely undetectable expression of Nav1.1 in the control GP. Furthermore, the administration of phenytoin, a VGSCs blocker, can effectively improve motor disabilities and reduce the synchronous oscillations in the BG of MPTP-treated mice. These findings suggested that the alterations of Nav1.1 expression may be associated with the high synchronous oscillations in the BG of PD animals.
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Affiliation(s)
- Weitang Liu
- School of Life Science, Shanghai University, Shanghai, China
| | - Wenwen Lao
- School of Life Science, Shanghai University, Shanghai, China
| | - Renxing Zhang
- School of Life Science, Shanghai University, Shanghai, China
| | - Hongyan Zhu
- School of Life Science, Shanghai University, Shanghai, China.
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3
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Bhardwaj P, Kulasiri D, Samarasinghe S. Modeling protein-protein interactions in axon initial segment to understand their potential impact on action potential initiation. Neural Regen Res 2021; 16:700-706. [PMID: 33063731 PMCID: PMC8067952 DOI: 10.4103/1673-5374.295332] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The axon initial segment (AIS) region is crucial for action potential initiation due to the presence of high-density AIS protein voltage-gated sodium channels (Nav). Nav channels comprise several serine residues responsible for the recruitment of Nav channels into the structure of AIS through interactions with ankyrin-G (AnkG). In this study, a series of computational experiments are performed to understand the role of AIS proteins casein kinase 2 and AnkG on Nav channel recruitment into the AIS. The computational simulation results using Virtual cell software indicate that Nav channels with all serine sites available for phosphorylation bind to AnkG with strong affinity. At the low initial concentration of AnkG and casein kinase 2, the concentration of Nav channels reduces significantly, suggesting the importance of casein kinase 2 and AnkG in the recruitment of Nav channels.
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Affiliation(s)
- Piyush Bhardwaj
- Centre of Advanced Computational Solutions (C-fACS); Department of Molecular Biosciences, Lincoln University, Christchurch, New Zealand
| | - Don Kulasiri
- Centre of Advanced Computational Solutions (C-fACS); Department of Molecular Biosciences, Lincoln University, Christchurch, New Zealand
| | - Sandhya Samarasinghe
- Centre of Advanced Computational Solutions (C-fACS), Lincoln University, Christchurch, New Zealand
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4
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Wadsworth PA, Singh AK, Nguyen N, Dvorak NM, Tapia CM, Russell WK, Stephan C, Laezza F. JAK2 regulates Nav1.6 channel function via FGF14 Y158 phosphorylation. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2020; 1867:118786. [PMID: 32599005 PMCID: PMC7984254 DOI: 10.1016/j.bbamcr.2020.118786] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Revised: 06/18/2020] [Accepted: 06/20/2020] [Indexed: 12/15/2022]
Abstract
BACKGROUND Protein interactions between voltage-gated sodium (Nav) channels and accessory proteins play an essential role in neuronal firing and plasticity. However, a surprisingly limited number of kinases have been identified as regulators of these molecular complexes. We hypothesized that numerous as-of-yet unidentified kinases indirectly regulate the Nav channel via modulation of the intracellular fibroblast growth factor 14 (FGF14), an accessory protein with numerous unexplored phosphomotifs and required for channel function in neurons. METHODS Here we present results from an in-cell high-throughput screening (HTS) against the FGF14: Nav1.6 complex using >3000 diverse compounds targeting an extensive range of signaling pathways. Regulation by top kinase targets was then explored using in vitro phosphorylation, biophysics, mass-spectrometry and patch-clamp electrophysiology. RESULTS Compounds targeting Janus kinase 2 (JAK2) were over-represented among HTS hits. Phosphomotif scans supported by mass spectrometry revealed FGF14Y158, a site previously shown to mediate both FGF14 homodimerization and interactions with Nav1.6, as a JAK2 phosphorylation site. Following inhibition of JAK2, FGF14 homodimerization increased in a manner directly inverse to FGF14:Nav1.6 complex formation, but not in the presence of the FGF14Y158A mutant. Patch-clamp electrophysiology revealed that through Y158, JAK2 controls FGF14-dependent modulation of Nav1.6 channels. In hippocampal CA1 pyramidal neurons, the JAK2 inhibitor Fedratinib reduced firing by a mechanism that is dependent upon expression of FGF14. CONCLUSIONS These studies point toward a novel mechanism by which levels of JAK2 in neurons could directly influence firing and plasticity by controlling the FGF14 dimerization equilibrium, and thereby the availability of monomeric species for interaction with Nav1.6.
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Affiliation(s)
- Paul A Wadsworth
- Department of Biochemistry and Molecular Biology, The University of Texas Medical Branch, Galveston, TX, USA; Department of Pharmacology & Toxicology, The University of Texas Medical Branch, Galveston, TX, USA
| | - Aditya K Singh
- Department of Pharmacology & Toxicology, The University of Texas Medical Branch, Galveston, TX, USA
| | - Nghi Nguyen
- HTS Screening Core, Center for Translational Cancer Research, Texas A&M Health Science Center: Institute of Biosciences and Technology, Houston, TX, USA
| | - Nolan M Dvorak
- Department of Pharmacology & Toxicology, The University of Texas Medical Branch, Galveston, TX, USA
| | - Cynthia M Tapia
- Department of Pharmacology & Toxicology, The University of Texas Medical Branch, Galveston, TX, USA
| | - William K Russell
- Department of Biochemistry and Molecular Biology, The University of Texas Medical Branch, Galveston, TX, USA
| | - Clifford Stephan
- HTS Screening Core, Center for Translational Cancer Research, Texas A&M Health Science Center: Institute of Biosciences and Technology, Houston, TX, USA
| | - Fernanda Laezza
- Department of Pharmacology & Toxicology, The University of Texas Medical Branch, Galveston, TX, USA; Center for Addiction Research, The University of Texas Medical Branch, Galveston, TX, USA.
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5
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Manduca JD, Thériault RK, Perreault ML. Glycogen synthase kinase-3: The missing link to aberrant circuit function in disorders of cognitive dysfunction? Pharmacol Res 2020; 157:104819. [PMID: 32305493 DOI: 10.1016/j.phrs.2020.104819] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Revised: 02/10/2020] [Accepted: 04/07/2020] [Indexed: 12/15/2022]
Abstract
Elevated GSK-3 activity has been implicated in cognitive dysfunction associated with various disorders including Alzheimer's disease, schizophrenia, type 2 diabetes, traumatic brain injury, major depressive disorder and bipolar disorder. Further, aberrant neural oscillatory activity in, and between, cortical regions and the hippocampus is consistently present within these same cognitive disorders. In this review, we will put forth the idea that increased GSK-3 activity serves as a pathological convergence point across cognitive disorders, inducing similar consequent impacts on downstream signaling mechanisms implicated in the maintenance of processes critical to brain systems communication and normal cognitive functioning. In this regard we suggest that increased activation of GSK-3 and neuronal oscillatory dysfunction are early pathological changes that may be functionally linked. Mechanistic commonalities between these disorders of cognitive dysfunction will be discussed and potential downstream targets of GSK-3 that may contribute to neuronal oscillatory dysfunction identified.
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Affiliation(s)
- Joshua D Manduca
- Department of Molecular and Cellular Biology, University of Guelph, ON, Canada
| | | | - Melissa L Perreault
- Department of Molecular and Cellular Biology, University of Guelph, ON, Canada.
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Zhu L, Chen L, Xu P, Lu D, Dai S, Zhong L, Han Y, Zhang M, Xiao B, Chang L, Wu Q. Genetic and molecular basis of epilepsy-related cognitive dysfunction. Epilepsy Behav 2020; 104:106848. [PMID: 32028124 DOI: 10.1016/j.yebeh.2019.106848] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 12/06/2019] [Accepted: 12/06/2019] [Indexed: 02/02/2023]
Abstract
Epilepsy is a common neurological disease characterized by recurrent seizures. About 70 million people were affected by epilepsy or epileptic seizures. Epilepsy is a complicated complex or symptomatic syndromes induced by structural, functional, and genetic causes. Meanwhile, several comorbidities are accompanied by epileptic seizures. Cognitive dysfunction is a long-standing complication associated with epileptic seizures, which severely impairs quality of life. Although the definitive pathogenic mechanisms underlying epilepsy-related cognitive dysfunction remain unclear, accumulating evidence indicates that multiple risk factors are probably involved in the development and progression of cognitive dysfunction in patients with epilepsy. These factors include the underlying etiology, recurrent seizures or status epilepticus, structural damage that induced secondary epilepsy, genetic variants, and molecular alterations. In this review, we summarize several theories that may explain the genetic and molecular basis of epilepsy-related cognitive dysfunction.
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Affiliation(s)
- Lin Zhu
- Department of Neurology, First Affiliated Hospital, Kunming Medical University, 295 Xi Chang Road, Kunming, Yunnan 650032, PR China
| | - Lu Chen
- Department of Neurology, First Affiliated Hospital, Kunming Medical University, 295 Xi Chang Road, Kunming, Yunnan 650032, PR China
| | - Puying Xu
- Department of Neurology, First Affiliated Hospital, Kunming Medical University, 295 Xi Chang Road, Kunming, Yunnan 650032, PR China
| | - Di Lu
- Biomedicine Engineering Research Center, Kunming Medical University, 1168 Chun Rong West Road, Kunming, Yunnan 650500, PR China
| | - Shujuan Dai
- Department of Neurology, First Affiliated Hospital, Kunming Medical University, 295 Xi Chang Road, Kunming, Yunnan 650032, PR China
| | - Lianmei Zhong
- Department of Neurology, First Affiliated Hospital, Kunming Medical University, 295 Xi Chang Road, Kunming, Yunnan 650032, PR China
| | - Yanbing Han
- Department of Neurology, First Affiliated Hospital, Kunming Medical University, 295 Xi Chang Road, Kunming, Yunnan 650032, PR China
| | - Mengqi Zhang
- Department of Neurology, Xiangya Hospital, Central South University, 87 Xiang Ya Road, Changsha, Hunan 410008, PR China
| | - Bo Xiao
- Department of Neurology, Xiangya Hospital, Central South University, 87 Xiang Ya Road, Changsha, Hunan 410008, PR China
| | - Lvhua Chang
- Department of Neurology, First Affiliated Hospital, Kunming Medical University, 295 Xi Chang Road, Kunming, Yunnan 650032, PR China.
| | - Qian Wu
- Department of Neurology, First Affiliated Hospital, Kunming Medical University, 295 Xi Chang Road, Kunming, Yunnan 650032, PR China.
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7
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MicroRNA-132 regulates total protein of Nav1.1 and Nav1.2 in the hippocampus and cortex of rat with chronic cerebral hypoperfusion. Behav Brain Res 2019; 366:118-125. [DOI: 10.1016/j.bbr.2019.03.026] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Revised: 03/14/2019] [Accepted: 03/14/2019] [Indexed: 11/23/2022]
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8
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Hu T, Xiao Z, Mao R, Chen B, Lu MN, Tong J, Mei R, Li SS, Xiao ZC, Zhang LF, Xiyang YB. Navβ2 knockdown improves cognition in APP/PS1 mice by partially inhibiting seizures and APP amyloid processing. Oncotarget 2017; 8:99284-99295. [PMID: 29245901 PMCID: PMC5725092 DOI: 10.18632/oncotarget.21849] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2017] [Accepted: 10/02/2017] [Indexed: 11/25/2022] Open
Abstract
Voltage-gated sodium channels beta 2 (Navβ2, encoded by SCN2B) is a substrate of β-site amyloid precursor protein cleaving enzyme 1 (BACE1) and regulates cell surface expression of channels in neurons. Previous studies reported enhanced Navβ2 processing by BACE1 in Alzheimer’s disease (AD) model and patients. We investigated whether changes in Navβ2 expression affect neuronal seizure and amyloid precursor protein (APP) processing in an AD mouse model. Our study used eight-month-old APP/presenilin 1 (PS1) mice and transgenic Navβ2 knockdown [by 61% vs. wild type (WT)] APP/PS1 mice (APP/PS1/Navβ2-kd), with age-matched WT and Navβ2 knockdown (Navβ2-kd) mice as controls. We found that Navβ2 knockdown in APP/PS1 mice partially reversed the abnormal Navβ2 cleavage and the changes in intracellular and total Nav1.1α expression. It also restored sodium currents density in hippocampal neurons and neuronal activity, as indicated by EEG tracing; improved Morris water maze performance; and shifted APP amyloidogenic metabolism towards non-amyloidogenic processing. There were no differences in these indicators between WT and Navβ2-kd mice. These results suggest Navβ2 knockdown may be a promising strategy for treating AD.
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Affiliation(s)
- Tao Hu
- Institute of Neuroscience, Basic Medical College, Kunming Medical University, Kunming, Yunnan, PR China.,Department of Laboratory Medicine, The Third People's Hospital of Yunnan Province, Kunming, Yunnan, PR China
| | - Zhangang Xiao
- Laboratory of Molecular Pharmacology, Department of Pharmacology, School of Pharmacy, Southwest Medical University, Luzhou, Sichuan, PR China.,Key Laboratory of Medical Electrophysiology, Ministry of Education, School of Pharmacy, Southwest Medical University, Luzhou, Sichuan, PR China
| | - Rui Mao
- School of Stomatology, Kunming Medical University, Kunming, Yunnan, PR China
| | - Bo Chen
- Experiment Center for Medical Science Research, Kunming Medical University, Kunming, Yunnan, PR China
| | - Min-Nan Lu
- Experiment Center for Medical Science Research, Kunming Medical University, Kunming, Yunnan, PR China
| | - Jun Tong
- Physical Education Department, Kunming Medical University, Kunming, Yunnan, PR China
| | - Rong Mei
- Department of Neurology, The First People's Hospital of Yunnan Province, Kunming, Yunnan, PR China
| | - Shan-Shan Li
- Basic Medical College, Kunming Medical University, Kunming, Yunnan, PR China
| | - Zhi-Cheng Xiao
- Institute of Molecular and Clinical Medicine, Kunming Medical University, Kunming, Yunnan, PR China.,Monash Immunology and Stem Cell Laboratories (MISCL), Monash University, Clayton, VIC, Australia
| | - Lian-Feng Zhang
- Key Laboratory of Human Diseases Comparative Medicine, Ministry of Health, Institute of Laboratory Animal Science, Chinese Academy of Medical Sciences(CAMS) & Comparative Medicine Centre, Peking Union Medical College (PUMC), Beijing, China
| | - Yan-Bin Xiyang
- Institute of Neuroscience, Basic Medical College, Kunming Medical University, Kunming, Yunnan, PR China
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Terragni B, Scalmani P, Franceschetti S, Cestèle S, Mantegazza M. Post-translational dysfunctions in channelopathies of the nervous system. Neuropharmacology 2017; 132:31-42. [PMID: 28571716 DOI: 10.1016/j.neuropharm.2017.05.028] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Revised: 05/12/2017] [Accepted: 05/26/2017] [Indexed: 12/23/2022]
Abstract
Channelopathies comprise various diseases caused by defects of ion channels. Modifications of their biophysical properties are common and have been widely studied. However, ion channels are heterogeneous multi-molecular complexes that are extensively modulated and undergo a maturation process comprising numerous steps of structural modifications and intracellular trafficking. Perturbations of these processes can give rise to aberrant channels that cause pathologies. Here we review channelopathies of the nervous system associated with dysfunctions at the post-translational level (folding, trafficking, degradation, subcellular localization, interactions with associated proteins and structural post-translational modifications). We briefly outline the physiology of ion channels' maturation and discuss examples of defective mechanisms, focusing in particular on voltage-gated sodium channels, which are implicated in numerous neurological disorders. We also shortly introduce possible strategies to develop therapeutic approaches that target these processes. This article is part of the Special Issue entitled 'Channelopathies.'
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Affiliation(s)
- Benedetta Terragni
- U.O. Neurophysiology and Diagnostic Epileptology, Foundation IRCCS Neurological Institute C. Besta, 20133 Milan, Italy
| | - Paolo Scalmani
- U.O. Neurophysiology and Diagnostic Epileptology, Foundation IRCCS Neurological Institute C. Besta, 20133 Milan, Italy
| | - Silvana Franceschetti
- U.O. Neurophysiology and Diagnostic Epileptology, Foundation IRCCS Neurological Institute C. Besta, 20133 Milan, Italy
| | - Sandrine Cestèle
- Institute of Molecular and Cellular Pharmacology (IPMC), CNRS UMR7275, 06560, Valbonne-Sophia Antipolis, France; University Côte d'Azur (UCA), 06560, Valbonne-Sophia Antipolis, France
| | - Massimo Mantegazza
- Institute of Molecular and Cellular Pharmacology (IPMC), CNRS UMR7275, 06560, Valbonne-Sophia Antipolis, France; University Côte d'Azur (UCA), 06560, Valbonne-Sophia Antipolis, France.
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10
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Lehnert S, Hartmann S, Hessler S, Adelsberger H, Huth T, Alzheimer C. Ion channel regulation by β-secretase BACE1 - enzymatic and non-enzymatic effects beyond Alzheimer's disease. Channels (Austin) 2016; 10:365-378. [PMID: 27253079 DOI: 10.1080/19336950.2016.1196307] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
β-site APP-cleaving enzyme 1 (BACE1) has become infamous for its pivotal role in the pathogenesis of Alzheimer's disease (AD). Consequently, BACE1 represents a prime target in drug development. Despite its detrimental involvement in AD, it should be quite obvious that BACE1 is not primarily present in the brain to drive mental decline. In fact, additional functions have been identified. In this review, we focus on the regulation of ion channels, specifically voltage-gated sodium and KCNQ potassium channels, by BACE1. These studies provide evidence for a highly unexpected feature in the functional repertoire of BACE1. Although capable of cleaving accessory channel subunits, BACE1 exerts many of its physiologically significant effects through direct, non-enzymatic interactions with main channel subunits. We discuss how the underlying mechanisms can be conceived and develop scenarios how the regulation of ion conductances by BACE1 might shape electric activity in the intact and diseased brain and heart.
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Affiliation(s)
- Sandra Lehnert
- a Institute of Physiology and Pathophysiology , Friedrich-Alexander-Universität Erlangen-Nürnberg , Erlangen , Germany
| | - Stephanie Hartmann
- a Institute of Physiology and Pathophysiology , Friedrich-Alexander-Universität Erlangen-Nürnberg , Erlangen , Germany
| | - Sabine Hessler
- b School of Psychology , University of Sussex , Brighton , UK
| | - Helmuth Adelsberger
- c Institute of Neuroscience, Technische Universität München , München , Germany
| | - Tobias Huth
- a Institute of Physiology and Pathophysiology , Friedrich-Alexander-Universität Erlangen-Nürnberg , Erlangen , Germany
| | - Christian Alzheimer
- a Institute of Physiology and Pathophysiology , Friedrich-Alexander-Universität Erlangen-Nürnberg , Erlangen , Germany
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11
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Sun LH, Yan ML, Hu XL, Peng LW, Che H, Bao YN, Guo F, Liu T, Chen X, Zhang R, Ban T, Wang N, Liu HL, Hou X, Ai J. MicroRNA-9 induces defective trafficking of Nav1.1 and Nav1.2 by targeting Navβ2 protein coding region in rat with chronic brain hypoperfusion. Mol Neurodegener 2015; 10:36. [PMID: 26259688 PMCID: PMC4530481 DOI: 10.1186/s13024-015-0032-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Accepted: 07/24/2015] [Indexed: 01/09/2023] Open
Abstract
Background Previous studies have demonstrated that the trafficking defects of Nav1.1/Nav1.2 are involved in the dementia pathophysiology. However, the detailed mechanisms are not fully understood. Moreover, whether the impaired miRNAs regulation linked to dementia is a key player in sodium channel trafficking disturbance remains unclear. The cognitive impairment induced by chronic cerebral ischemia through chronic brain hypoperfusion (CBH) is likely reason to precede dementia. Therefore, our goal in the present study was to examine the role of microRNA-9 (miR-9) in regulating Nav1.1/Nav1.2 trafficking under CBH generated by bilateral common carotid artery occlusion (2VO). Results The impairment of Nav1.1/Nav1.2 trafficking and decreased expression of Navβ2 were found in the hippocampi and cortices of rats following CBH generated by bilateral 2VO. MiR-9 was increased in both the hippocampi and cortices of rats following CBH by qRT-PCR. Intriguingly, miR-9 suppressed, while AMO-miR-9 enhanced, the trafficking of Nav1.1/Nav1.2 from cytoplasm to cell membrane. Further study showed that overexpression of miR-9 inhibited the Navβ2 expression by targeting on its coding sequence (CDS) domain by dual luciferase assay. However, binding-site mutation or miR-masks failed to influence Navβ2 expression as well as Nav1.1/Nav1.2 trafficking process, indicating that Navβ2 is a potential target for miR-9. Lentivirus-mediated miR-9 overexpression also inhibited Navβ2 expression and elicited translocation deficits to cell membrane of Nav1.1/Nav1.2 in rats, whereas injection of lentivirus-mediated miR-9 knockdown could reverse the impaired trafficking of Nav1.1/Nav1.2 triggered by 2VO. Conclusions We conclude that miR-9 may play a key role in regulating the process of Nav1.1/Nav1.2 trafficking via targeting on Navβ2 protein in 2VO rats at post-transcriptional level, and inhibition of miR-9 may be a potentially valuable approach to prevent Nav1.1/Nav1.2 trafficking disturbance induced by CBH.
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Affiliation(s)
- Li-Hua Sun
- Department of Pharmacology, Harbin Medical University, No.157 Baojian Road, Nangang District,Harbin, Heilongjiang Province, 15008, China.
| | - Mei-Ling Yan
- Department of Pharmacology, Harbin Medical University, No.157 Baojian Road, Nangang District,Harbin, Heilongjiang Province, 15008, China
| | - Xue-Ling Hu
- Department of Pharmacology, Harbin Medical University, No.157 Baojian Road, Nangang District,Harbin, Heilongjiang Province, 15008, China
| | - Li-Wei Peng
- Department of Pharmacology, Harbin Medical University, No.157 Baojian Road, Nangang District,Harbin, Heilongjiang Province, 15008, China
| | - Hui Che
- Department of Pharmacology, Harbin Medical University, No.157 Baojian Road, Nangang District,Harbin, Heilongjiang Province, 15008, China
| | - Ya-Nan Bao
- Department of Pharmacology, Harbin Medical University, No.157 Baojian Road, Nangang District,Harbin, Heilongjiang Province, 15008, China
| | - Fei Guo
- Department of Pharmacology, Harbin Medical University, No.157 Baojian Road, Nangang District,Harbin, Heilongjiang Province, 15008, China
| | - Tong Liu
- Department of Pharmacology, Harbin Medical University, No.157 Baojian Road, Nangang District,Harbin, Heilongjiang Province, 15008, China
| | - Xin Chen
- Department of Pharmacology, Harbin Medical University, No.157 Baojian Road, Nangang District,Harbin, Heilongjiang Province, 15008, China
| | - Rong Zhang
- Department of Pharmacology, Harbin Medical University, No.157 Baojian Road, Nangang District,Harbin, Heilongjiang Province, 15008, China
| | - Tao Ban
- Department of Pharmacology, Harbin Medical University, No.157 Baojian Road, Nangang District,Harbin, Heilongjiang Province, 15008, China
| | - Ning Wang
- Department of Pharmacology, Harbin Medical University, No.157 Baojian Road, Nangang District,Harbin, Heilongjiang Province, 15008, China
| | - Huai-Lei Liu
- Department of Neurosurgery, The First Affiliated Hospital of Harbin Medical University, No.157 Baojian Road, Nangang District, Harbin, Heilongjiang Province, 150081, China
| | - Xu Hou
- Department of Neurosurgery, The First Affiliated Hospital of Harbin Medical University, No.157 Baojian Road, Nangang District, Harbin, Heilongjiang Province, 150081, China
| | - Jing Ai
- Department of Pharmacology, Harbin Medical University, No.157 Baojian Road, Nangang District,Harbin, Heilongjiang Province, 15008, China.
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12
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Kandalepas PC, Vassar R. The normal and pathologic roles of the Alzheimer's β-secretase, BACE1. Curr Alzheimer Res 2015; 11:441-9. [PMID: 24893886 DOI: 10.2174/1567205011666140604122059] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Revised: 01/15/2014] [Accepted: 01/25/2014] [Indexed: 01/18/2023]
Abstract
As the most common neurodegenerative disease, therapeutic avenues for the treatment and prevention of Alzheimer's Disease are highly sought after. The aspartic protease BACE1 is the initiator enzyme for the formation of Aβ, a major constituent of amyloid plaques that represent one of the hallmark pathological features of this disorder. Thus, targeting BACE1 for disease-modifying AD therapies represents a rationale approach. The collective knowledge acquired from investigations of BACE1 deletion mutants and characterization of BACE1 substrates has downstream significance not only for the discovery of AD drug therapies but also for predicting side effects of BACE1 inhibition. Here we discuss the identification and validation of BACE1 as the β-secretase implicated in AD, in addition to information regarding BACE1 cell biology, localization, substrates and potential physiological functions derived from BACE1 knockout models.
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Affiliation(s)
| | - Robert Vassar
- Northwestern University, Feinberg School of Medicine, Department of Cell & Molecular Biology, 300 E. Superior, Tarry 8-713, IL 60611, Chicago.
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Genetic suppression of transgenic APP rescues Hypersynchronous network activity in a mouse model of Alzeimer's disease. J Neurosci 2014; 34:3826-40. [PMID: 24623762 DOI: 10.1523/jneurosci.5171-13.2014] [Citation(s) in RCA: 128] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Alzheimer's disease (AD) is associated with an elevated risk for seizures that may be fundamentally connected to cognitive dysfunction. Supporting this link, many mouse models for AD exhibit abnormal electroencephalogram (EEG) activity in addition to the expected neuropathology and cognitive deficits. Here, we used a controllable transgenic system to investigate how network changes develop and are maintained in a model characterized by amyloid β (Aβ) overproduction and progressive amyloid pathology. EEG recordings in tet-off mice overexpressing amyloid precursor protein (APP) from birth display frequent sharp wave discharges (SWDs). Unexpectedly, we found that withholding APP overexpression until adulthood substantially delayed the appearance of epileptiform activity. Together, these findings suggest that juvenile APP overexpression altered cortical development to favor synchronized firing. Regardless of the age at which EEG abnormalities appeared, the phenotype was dependent on continued APP overexpression and abated over several weeks once transgene expression was suppressed. Abnormal EEG discharges were independent of plaque load and could be extinguished without altering deposited amyloid. Selective reduction of Aβ with a γ-secretase inhibitor has no effect on the frequency of SWDs, indicating that another APP fragment or the full-length protein was likely responsible for maintaining EEG abnormalities. Moreover, transgene suppression normalized the ratio of excitatory to inhibitory innervation in the cortex, whereas secretase inhibition did not. Our results suggest that APP overexpression, and not Aβ overproduction, is responsible for EEG abnormalities in our transgenic mice and can be rescued independently of pathology.
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Southan C, Hancock JM. A tale of two drug targets: the evolutionary history of BACE1 and BACE2. Front Genet 2013; 4:293. [PMID: 24381583 PMCID: PMC3865767 DOI: 10.3389/fgene.2013.00293] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2013] [Accepted: 11/29/2013] [Indexed: 11/22/2022] Open
Abstract
The beta amyloid (APP) cleaving enzyme (BACE1) has been a drug target for Alzheimer's Disease (AD) since 1999 with lead inhibitors now entering clinical trials. In 2011, the paralog, BACE2, became a new target for type II diabetes (T2DM) having been identified as a TMEM27 secretase regulating pancreatic β cell function. However, the normal roles of both enzymes are unclear. This study outlines their evolutionary history and new opportunities for functional genomics. We identified 30 homologs (UrBACEs) in basal phyla including Placozoans, Cnidarians, Choanoflagellates, Porifera, Echinoderms, Annelids, Mollusks and Ascidians (but not Ecdysozoans). UrBACEs are predominantly single copy, show 35-45% protein sequence identity with mammalian BACE1, are ~100 residues longer than cathepsin paralogs with an aspartyl protease domain flanked by a signal peptide and a C-terminal transmembrane domain. While multiple paralogs in Trichoplax and Monosiga pre-date the nervous system, duplication of the UrBACE in fish gave rise to BACE1 and BACE2 in the vertebrate lineage. The latter evolved more rapidly as the former maintained the emergent neuronal role. In mammals, Ka/Ks for BACE2 is higher than BACE1 but low ratios for both suggest purifying selection. The 5' exons show higher Ka/Ks than the catalytic section. Model organism genomes show the absence of certain BACE human substrates when the UrBACE is present. Experiments could thus reveal undiscovered substrates and roles. The human protease double-target status means that evolutionary trajectories and functional shifts associated with different substrates will have implications for the development of clinical candidates for both AD and T2DM. A rational basis for inhibition specificity ratios and assessing target-related side effects will be facilitated by a more complete picture of BACE1 and BACE2 functions informed by their evolutionary context.
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Affiliation(s)
- Christopher Southan
- IUPHAR Database and Guide to Pharmacology Web Portal Group, University/BHF Centre for Cardiovascular Science, Queen's Medical Research Institute, University of EdinburghEdinburgh, UK
| | - John M. Hancock
- Department of Physiology, Development and Neuroscience, University of CambridgeCambridge, UK
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Kim DY, Wertz MH, Gautam V, D'Avanzo C, Bhattacharyya R, Kovacs DM. The E280A presenilin mutation reduces voltage-gated sodium channel levels in neuronal cells. NEURODEGENER DIS 2013; 13:64-68. [PMID: 24217025 DOI: 10.1159/000354669] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Accepted: 07/24/2013] [Indexed: 01/28/2023] Open
Abstract
BACKGROUND Familial Alzheimer's disease (FAD) mutations in presenilin (PS) modulate PS/γ-secretase activity and therefore contribute to AD pathogenesis. Previously, we found that PS/γ-secretase cleaves voltage-gated sodium channel β2-subunits (Navβ2), releases the intracellular domain of Navβ2 (β2-ICD), and thereby, increases intracellular sodium channel α-subunit Nav1.1 levels. Here, we tested whether FAD-linked PS1 mutations modulate Navβ2 cleavages and Nav1.1 levels. OBJECTIVE It was the aim of this study to analyze the effects of PS1-linked FAD mutations on Navβ2 processing and Nav1.1 levels in neuronal cells. METHODS We first generated B104 rat neuroblastoma cells stably expressing Navβ2 and wild-type PS1 (wtPS1), PS1 with one of three FAD mutations (E280A, M146L or ΔE9), or PS1 with a non-FAD mutation (D333G). Navβ2 processing and Nav1.1 protein and mRNA levels were then analyzed by Western blot and real-time RT-PCR, respectively. RESULTS The FAD-linked E280A mutation significantly decreased PS/γ-secretase-mediated processing of Navβ2 as compared to wtPS1 controls, both in cells and in a cell-free system. Nav1.1 mRNA and protein levels, as well as the surface levels of Nav channel α-subunits, were also significantly reduced in PS1(E280A) cells. CONCLUSION Our data indicate that the FAD-linked PS1(E280A) mutation decreases Nav channel levels by partially inhibiting the PS/γ-secretase-mediated cleavage of Navβ2 in neuronal cells.
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Affiliation(s)
- Doo Yeon Kim
- Genetics and Aging Research Unit, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA
| | - Mary H Wertz
- Genetics and Aging Research Unit, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA
| | - Vivek Gautam
- Genetics and Aging Research Unit, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA
| | - Carla D'Avanzo
- Genetics and Aging Research Unit, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA
| | - Raja Bhattacharyya
- Genetics and Aging Research Unit, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA
| | - Dora M Kovacs
- Genetics and Aging Research Unit, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA
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Sodium channel cleavage is associated with aberrant neuronal activity and cognitive deficits in a mouse model of Alzheimer's disease. J Neurosci 2013; 33:7020-6. [PMID: 23595759 DOI: 10.1523/jneurosci.2325-12.2013] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
BACE1 is the rate-limiting enzyme that cleaves amyloid precursor protein (APP) to produce the amyloid β peptides that accumulate in Alzheimer's disease (AD). BACE1, which is elevated in AD patients and APP transgenic mice, also cleaves the β2-subunit of voltage-gated sodium channels (Navβ2). Although increased BACE1 levels are associated with Navβ2 cleavage in AD patients, whether Navβ2 cleavage occurs in APP mice had not yet been examined. Such a finding would be of interest because of its potential impact on neuronal activity: previous studies demonstrated that BACE1-overexpressing mice exhibit excessive cleavage of Navβ2 and reduced sodium current density, but the phenotype associated with loss of function mutations in either Navβ-subunits or pore-forming α-subunits is epilepsy. Because mounting evidence suggests that epileptiform activity may play an important role in the development of AD-related cognitive deficits, we examined whether enhanced cleavage of Navβ2 occurs in APP transgenic mice, and whether it is associated with aberrant neuronal activity and cognitive deficits. We found increased levels of BACE1 expression and Navβ2 cleavage fragments in cortical lysates from APP transgenic mice, as well as associated alterations in Nav1.1α expression and localization. Both pyramidal neurons and inhibitory interneurons exhibited evidence of increased Navβ2 cleavage. Moreover, the magnitude of alterations in sodium channel subunits was associated with aberrant EEG activity and impairments in the Morris water maze. Together, these results suggest that altered processing of voltage-gated sodium channels may contribute to aberrant neuronal activity and cognitive deficits in AD.
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Sachse CC, Kim YH, Agsten M, Huth T, Alzheimer C, Kovacs DM, Kim DY. BACE1 and presenilin/γ-secretase regulate proteolytic processing of KCNE1 and 2, auxiliary subunits of voltage-gated potassium channels. FASEB J 2013; 27:2458-67. [PMID: 23504710 DOI: 10.1096/fj.12-214056] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
BACE1 and presenilin (PS)/γ-secretase play a major role in Alzheimer's disease pathogenesis by regulating amyloid-β peptide generation. We recently showed that these secretases also regulate the processing of voltage-gated sodium channel auxiliary β-subunits and thereby modulate membrane excitability. Here, we report that KCNE1 and KCNE2, auxiliary subunits of voltage-gated potassium channels, undergo sequential cleavage mediated by either α-secretase and PS/γ-secretase or BACE1 and PS/γ-secretase in cells. Elevated α-secretase or BACE1 activities increased C-terminal fragment (CTF) levels of KCNE1 and 2 in human embryonic kidney (HEK293T) and rat neuroblastoma (B104) cells. KCNE-CTFs were then further processed by PS/γ-secretase to KCNE intracellular domains. These KCNE cleavages were specifically blocked by chemical inhibitors of the secretases in the same cell models. We also verified our results in mouse cardiomyocytes and cultured primary neurons. Endogenous KCNE1- and KCNE2-CTF levels increased by 2- to 4-fold on PS/γ-secretase inhibition or BACE1 overexpression in these cells. Furthermore, the elevated BACE1 activity increased KCNE1 processing and shifted KCNE1/KCNQ1 channel activation curve to more positive potentials in HEK cells. KCNE1/KCNQ1 channel is a cardiac potassium channel complex, and the positive shift would lead to a decrease in membrane repolarization during cardiac action potential. Together, these results clearly showed that KCNE1 and KCNE2 cleavages are regulated by BACE1 and PS/γ-secretase activities under physiological conditions. Our results also suggest a functional role of KCNE cleavage in regulating voltage-gated potassium channels.
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Affiliation(s)
- Carolyn C Sachse
- Neurobiology of Disease Laboratory, Genetics and Aging Research Unit, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA
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Focal Scn1a knockdown induces cognitive impairment without seizures. Neurobiol Dis 2013; 54:297-307. [PMID: 23318929 DOI: 10.1016/j.nbd.2012.12.021] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2012] [Revised: 12/05/2012] [Accepted: 12/21/2012] [Indexed: 11/23/2022] Open
Abstract
Cognitive impairment is a common comorbidity in pediatric epilepsy that can severely affect quality of life. In many cases, antiepileptic treatments fail to improve cognition. Therefore, a fundamental question is whether underlying brain abnormalities may contribute to cognitive impairment through mechanisms independent of seizures. Here, we examined the possible effects on cognition of Nav1.1 down-regulation, a sodium channel principally involved in Dravet syndrome but also implicated in other cognitive disorders, including autism and Alzheimer's disease. Using an siRNA approach to knockdown Nav1.1 selectively in the basal forebrain region, we were able to target a learning and memory network while avoiding the generation of spontaneous seizures. We show that reduction of Nav1.1 expression in the medial septum and diagonal band of Broca leads to a dysregulation of hippocampal oscillations in association with a spatial memory deficit. We propose that the underlying etiology responsible for Dravet syndrome may directly contribute to cognitive impairment in a manner that is independent from seizures.
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Dislich B, Lichtenthaler SF. The Membrane-Bound Aspartyl Protease BACE1: Molecular and Functional Properties in Alzheimer's Disease and Beyond. Front Physiol 2012; 3:8. [PMID: 22363289 PMCID: PMC3281277 DOI: 10.3389/fphys.2012.00008] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Accepted: 01/11/2012] [Indexed: 12/31/2022] Open
Abstract
The β-site APP cleaving enzyme 1 (BACE1) is a transmembrane aspartyl protease involved in Alzheimer’s disease (AD) pathogenesis and in myelination. BACE1 initiates the generation of the pathogenic amyloid β-peptide, which makes BACE1 a major drug target for AD. BACE1 also cleaves and activates neuregulin 1, thereby contributing to postnatal myelination, in particular in the peripheral nervous system. Additional proteins are also cleaved by BACE1, but less is known about the physiological consequences of their cleavage. Recently, new phenotypes were described in BACE1-deficient mice. Although it remains unclear through which BACE1 substrates they are mediated, the phenotypes suggest a versatile role of this protease for diverse physiological processes. This review summarizes the enzymatic and cellular properties of BACE1 as well as its regulation by lipids, by transcriptional, and by translational mechanisms. The main focus will be on the recent progress in understanding BACE1 function and its implication for potential mechanism-based side effects upon therapeutic inhibition.
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Affiliation(s)
- Bastian Dislich
- German Center for Neurodegenerative Diseases (DZNE) Munich, Germany
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Abstract
Prevention of epileptogenesis after brain trauma is an unmet medical challenge. Recent molecular profiling studies have provided an insight into molecular changes that contribute to formation of ictogenic neuronal networks, including genes regulating synaptic or neuronal plasticity, cell death, proliferation, and inflammatory or immune responses. These mechanisms have been targeted to prevent epileptogenesis in animal models. Favourable effects have been obtained using immunosuppressants, antibodies blocking adhesion of leucocytes to endothelial cells, gene therapy driving expression of neurotrophic factors, pharmacological neurostimulation, or even with conventional antiepileptic drugs by administering them before the appearance of genetic epilepsy. Further studies are needed to clarify the optimum time window and aetiological specificity of treatments. Questions related to adverse events also need further consideration. Encouragingly, the recent experimental studies emphasise that the complicated process of epileptogenesis can be favourably modified, and that antiepileptogenesis as a treatment indication might not be an impossible mission.
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Affiliation(s)
- Asla Pitkänen
- Department of Neurobiology, A I Virtanen Institute for Molecular Sciences, University of Eastern Finland, and Department of Neurology, Kuopio University Hospital, Kuopio, Finland.
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Gersbacher MT, Kim DY, Bhattacharyya R, Kovacs DM. Identification of BACE1 cleavage sites in human voltage-gated sodium channel beta 2 subunit. Mol Neurodegener 2010; 5:61. [PMID: 21182789 PMCID: PMC3022600 DOI: 10.1186/1750-1326-5-61] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2010] [Accepted: 12/23/2010] [Indexed: 11/10/2022] Open
Abstract
Background The voltage-gated sodium channel β2 subunit (Navβ2) is a physiological substrate of BACE1 (β-site APP cleaving enzyme) and γ-secretase, two proteolytic enzymes central to Alzheimer's disease pathogenesis. Previously, we have found that the processing of Navβ2 by BACE1 and γ-secretase regulates sodium channel metabolism in neuronal cells. In the current study we identified the BACE1 cleavage sites in human Navβ2. Results We found a major (147-148 L↓M, where ↓ indicates the cleavage site) and a minor (144145 L↓Q) BACE1 cleavage site in the extracellular domain of human Navβ2 using a cell-free BACE1 cleavage assay followed by mass spectrometry. Next, we introduced two different double mutations into the identified major BACE1 cleavage site in human Navβ2: 147LM/VI and 147LM/AA. Both mutations dramatically decreased the cleavage of human Navβ2 by endogenous BACE1 in cell-free BACE1 cleavage assays. Neither of the two mutations affected subcellular localization of Navβ2 as confirmed by confocal fluorescence microscopy and subcellular fractionation of cholesterol-rich domains. Finally, wildtype and mutated Navβ2 were expressed along BACE1 in B104 rat neuroblastoma cells. In spite of α-secretase still actively cleaving the mutant proteins, Navβ2 cleavage products decreased by ~50% in cells expressing Navβ2 (147LM/VI) and ~75% in cells expressing Navβ2 (147LM/AA) as compared to cells expressing wildtype Navβ2. Conclusion We identified a major (147-148 L↓M) and a minor (144-145 L↓Q) BACE1 cleavage site in human Navβ2. Our in vitro and cell-based results clearly show that the 147-148 L↓M is the major BACE1 cleavage site in human Navβ2. These findings expand our understanding of the role of BACE1 in voltage-gated sodium channel metabolism.
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Affiliation(s)
- Manuel T Gersbacher
- Neurobiology of Disease Laboratory, Genetics and Aging Research Unit, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA.
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