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Gadhia A, Barker E, Morgan A, Barclay JW. Functional analysis of epilepsy-associated GABA A receptor mutations using Caenorhabditis elegans. Epilepsia Open 2024; 9:1458-1466. [PMID: 38813985 PMCID: PMC11296113 DOI: 10.1002/epi4.12982] [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: 01/24/2024] [Revised: 05/03/2024] [Accepted: 05/18/2024] [Indexed: 05/31/2024] Open
Abstract
OBJECTIVE GABAA receptor subunit mutations pose a significant risk for genetic generalized epilepsy; however, there are over 150 identified variants, many with unknown or unvalidated pathogenicity. We aimed to develop in vivo models for testing GABAA receptor variants using the model organism, Caenorhabditis elegans. METHODS CRISPR-Cas9 gene editing was used to create a complete deletion of unc-49, a C. elegans GABAA receptor, and to create homozygous epilepsy-associated mutations in the endogenous unc-49 gene. The unc-49 deletion strain was rescued with transgenes for either the C. elegans unc-49B subunit or the α1, β3, and γ2 subunits for the human GABAA receptor. All newly created strains were analyzed for phenotype and compared against existing unc-49 mutations. RESULTS Nematodes with a full genetic deletion of the entire unc-49 locus were compared with existing unc-49 mutations in three separate phenotypic assays-coordinated locomotion, shrinker frequency and seizure-like convulsions. The full unc-49 deletion exhibited reduced locomotion and increased shrinker frequency and PTZ-induced convulsions, but were not found to be phenotypically stronger than existing unc-49 mutations. Rescue with the unc-49B subunit or creation of humanized worms for the GABAA receptor both showed partial phenotypic rescue for all three phenotypes investigated. Finally, two epilepsy-associated variants were analyzed and deemed to be loss of function, thus validating their pathogenicity. SIGNIFICANCE These findings establish C. elegans as a genetic model to investigate GABAA receptor mutations and delineate a platform for validating associated variants in any epilepsy-associated gene. PLAIN LANGUAGE SUMMARY Epilepsy is a complex human disease that can be caused by mutations in specific genes. Many possible mutations have been identified, but it is unknown for most of them whether they cause the disease. We tested the role of mutations in one specific gene using a small microscopic worm as an animal model. Our results establish this worm as a model for epilepsy and confirm that the two unknown mutations are likely to cause the disease.
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Affiliation(s)
- Ami Gadhia
- Department of Biochemistry, Cell and Systems Biology, ISMIBUniversity of LiverpoolLiverpoolUK
| | - Eleanor Barker
- Department of Biochemistry, Cell and Systems Biology, ISMIBUniversity of LiverpoolLiverpoolUK
| | - Alan Morgan
- Department of Biochemistry, Cell and Systems Biology, ISMIBUniversity of LiverpoolLiverpoolUK
| | - Jeff W. Barclay
- Department of Biochemistry, Cell and Systems Biology, ISMIBUniversity of LiverpoolLiverpoolUK
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Ewald CY, Pulous FE, Lok SWY, Pun FW, Aliper A, Ren F, Zhavoronkov A. TNIK's emerging role in cancer, metabolism, and age-related diseases. Trends Pharmacol Sci 2024; 45:478-489. [PMID: 38777670 DOI: 10.1016/j.tips.2024.04.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2024] [Revised: 04/12/2024] [Accepted: 04/28/2024] [Indexed: 05/25/2024]
Abstract
Traf2- and Nck-interacting kinase (TNIK) has emerged as a key regulator of pathological metabolic signaling in several diseases and is a promising drug target. Originally studied for its role in cell migration and proliferation, TNIK possesses several newly identified functions that drive the pathogenesis of multiple diseases. Specifically, we evaluate TNIK's newfound roles in cancer, metabolic disorders, and neuronal function. We emphasize the implications of TNIK signaling in metabolic signaling and evaluate the translational potential of these discoveries. We also highlight how TNIK's role in many biological processes converges upon several hallmarks of aging. We conclude by discussing the therapeutic landscape of TNIK-targeting drugs and the recent success of clinical trials targeting TNIK.
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Affiliation(s)
- Collin Y Ewald
- Laboratory of Extracellular Matrix Regeneration, Institute of Translational Medicine, Department of Health Sciences and Technology, ETH Zürich, Schwerzenbach CH-8603, Switzerland
| | - Fadi E Pulous
- Insilico Medicine US Inc., 345 Park Avenue South, 2nd Floor Suite 006, New York, NY 10010, USA
| | - Sarah Wing Yan Lok
- Insilico Medicine Hong Kong Ltd., Unit 310, 3/F, Building 8W, Hong Kong Science and Technology Park, Hong Kong, SAR, China
| | - Frank W Pun
- Insilico Medicine Hong Kong Ltd., Unit 310, 3/F, Building 8W, Hong Kong Science and Technology Park, Hong Kong, SAR, China
| | - Alex Aliper
- Insilico Medicine AI Limited, Level 6, Unit 08, Block A, IRENA HQ Building, Masdar City, Abu Dhabi, UAE
| | - Feng Ren
- Insilico Medicine Shanghai Ltd., Suite 902, Tower C, Changtai Plaza, 2889 Jinke Road, Pudong, Shanghai 201203, China
| | - Alex Zhavoronkov
- Insilico Medicine US Inc., 345 Park Avenue South, 2nd Floor Suite 006, New York, NY 10010, USA; Insilico Medicine Hong Kong Ltd., Unit 310, 3/F, Building 8W, Hong Kong Science and Technology Park, Hong Kong, SAR, China; Insilico Medicine AI Limited, Level 6, Unit 08, Block A, IRENA HQ Building, Masdar City, Abu Dhabi, UAE; Insilico Medicine Shanghai Ltd., Suite 902, Tower C, Changtai Plaza, 2889 Jinke Road, Pudong, Shanghai 201203, China; Buck Institute for Research on Aging, Novato, CA 94945, USA.
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3
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Muñoz-Juan A, Benseny-Cases N, Guha S, Barba I, Caldwell KA, Caldwell GA, Agulló L, Yuste VJ, Laromaine A, Dalfó E. Caenorhabditis elegans RAC1/ced-10 mutants as a new animal model to study very early stages of Parkinson's disease. Prog Neurobiol 2024; 234:102572. [PMID: 38253120 DOI: 10.1016/j.pneurobio.2024.102572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 11/21/2023] [Accepted: 01/15/2024] [Indexed: 01/24/2024]
Abstract
Patients with Parkinson's disease (PD) display non-motor symptoms arising prior to the appearance of motor signs and before a clear diagnosis. Motor and non-motor symptoms correlate with progressive deposition of the protein alpha-synuclein (Asyn) both within and outside of the central nervous system, and its accumulation parallels neurodegeneration. The genome of Caenorhabditis elegans does not encode a homolog of Asyn, thus rendering this nematode an invaluable system with which to investigate PD-related mechanisms in the absence of interference from endogenous Asyn aggregation. CED-10 is the nematode homolog of human RAC1, a small GTPase needed to maintain the function and survival of dopaminergic neurons against human Asyn-induced toxicity in C. elegans. Here, we introduce C. elegans RAC1/ced-10 mutants as a predictive tool to investigate early PD symptoms before neurodegeneration occurs. Deep phenotyping of these animals reveals that, early in development, they displayed altered defecation cycles, GABAergic abnormalities and an increased oxidation index. Moreover, they exhibited altered lipid metabolism evidenced by the accumulation of lipid droplets. Lipidomic fingerprinting indicates that phosphatidylcholine and sphingomyelin, but not phosphatidylethanolamine or phosphatidylserine, were elevated in RAC1/ced-10 mutant nematodes. These collective characteristics reflect the non-motor dysfunction, GABAergic neurotransmission defects, upregulation of stress response mechanisms, and metabolic changes associated with early-onset PD. Thus, we put forward an easy-to-manipulate preclinical animal model to deepen our understanding of early-stage PD and accelerate the translational path for therapeutic target discovery.
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Affiliation(s)
- A Muñoz-Juan
- Group of Nanoparticles and Nanocomposites, Institut Ciència de Materials de Barcelona, ICMAB-CSIC, Campus UAB, 08193 Bellaterra, Barcelona, Spain
| | - N Benseny-Cases
- Biophysics Unit. Department of Biochemistry and Molecular Biology. Universitat Autònoma de Barcelona, Bellaterra 08193, Barcelona, Spain
| | - S Guha
- Nautilus Biotechnology, 835 Industrial Rd, San Carlos, CA 94070, USA
| | - I Barba
- Faculty of Medicine, University of Vic-Central University of Catalonia (UVic-UCC), Institute for Research and Innovation in Life Sciences and Health in Central Catalonia (IRIS-CC), Can Baumann, 08500 Vic, Spain
| | - K A Caldwell
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35487, USA; Department of Neurology, Center for Neurodegeneration and Experimental Therapeutics, and Nathan Shock Center of Excellence in the Basic Biology of Aging, University of Alabama at Birmingham Heersink School of Medicine, Birmingham, AL 35294, USA
| | - G A Caldwell
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35487, USA; Department of Neurology, Center for Neurodegeneration and Experimental Therapeutics, and Nathan Shock Center of Excellence in the Basic Biology of Aging, University of Alabama at Birmingham Heersink School of Medicine, Birmingham, AL 35294, USA
| | - L Agulló
- Faculty of Medicine, University of Vic-Central University of Catalonia (UVic-UCC), Institute for Research and Innovation in Life Sciences and Health in Central Catalonia (IRIS-CC), Can Baumann, 08500 Vic, Spain
| | - V J Yuste
- Department of Biochemistry and Molecular Biology, Institut de Neurociències, Faculty of Medicine, M2, Universitat Autònoma de Barcelona (UAB), Bellaterra Campus, Cerdanyola del Vallés, Barcelona, Spain
| | - A Laromaine
- Group of Nanoparticles and Nanocomposites, Institut Ciència de Materials de Barcelona, ICMAB-CSIC, Campus UAB, 08193 Bellaterra, Barcelona, Spain
| | - E Dalfó
- Faculty of Medicine, University of Vic-Central University of Catalonia (UVic-UCC), Institute for Research and Innovation in Life Sciences and Health in Central Catalonia (IRIS-CC), Can Baumann, 08500 Vic, Spain; Department of Biochemistry and Molecular Biology, Institut de Neurociències, Faculty of Medicine, M2, Universitat Autònoma de Barcelona (UAB), Bellaterra Campus, Cerdanyola del Vallés, Barcelona, Spain; Institute of Neurosciences, Faculty of Medicine, Universitat Autònoma de Barcelona (UAB), Campus UAB, 08193 Cerdanyola del Vallès, Spain.
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p21-Activated kinase 1 (PAK1) in aging and longevity: An overview. Ageing Res Rev 2021; 71:101443. [PMID: 34390849 DOI: 10.1016/j.arr.2021.101443] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Revised: 07/26/2021] [Accepted: 08/10/2021] [Indexed: 02/08/2023]
Abstract
The p21-activated kinases (PAKs) belong to serine/threonine kinases family, regulated by ∼21 kDa small signaling G proteins RAC1 and CDC42. The mammalian PAK family comprises six members (PAK1-6) that are classified into two groups (I and II) based on their domain architecture and regulatory mechanisms. PAKs are implicated in a wide range of cellular functions. PAK1 has recently attracted increasing attention owing to its involvement in oncogenesis, tumor progression, and metastasis as well as several life-limiting diseases and pathological conditions. In Caenorhabditis elegans, PAK1 functions limit the lifespan under basal conditions by inhibiting forkhead transcription factor DAF-16. Interestingly, PAK depletion extended longevity and attenuated the onset of age-related phenotypes in a premature-aging mouse model and delayed senescence in mammalian fibroblasts. These observations implicate PAKs as not only oncogenic but also aging kinases. Therefore, PAK-targeting genetic and/or pharmacological interventions, particularly PAK1-targeting, could be a viable strategy for developing cancer therapies with relatively no side effects and promoting healthy longevity. This review describes PAK family proteins, their biological functions, and their role in regulating aging and longevity using C. elegans. Moreover, we discuss the effect of small-molecule PAK1 inhibitors on the lifespan and healthspan of C. elegans.
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Dong X, Jin S, Shao Z. Glia Promote Synaptogenesis through an IQGAP PES-7 in C. elegans. Cell Rep 2020; 30:2614-2626.e2. [PMID: 32101740 DOI: 10.1016/j.celrep.2020.01.102] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2019] [Revised: 11/11/2019] [Accepted: 01/29/2020] [Indexed: 11/25/2022] Open
Abstract
Synapses are fundamental to the normal function of the nervous system. Glia play a pivotal role in regulating synaptic formation. However, how presynaptic neurons assemble synaptic structure in response to the glial signals remains largely unexplored. To address this question, we use cima-1 mutant C. elegans as an in vivo model, in which the astrocyte-like VCSC glial processes ectopically reach an asynaptic neurite region and promote presynaptic formation there. Through an RNAi screen, we find that the Rho GTPase CDC-42 and IQGAP PES-7 are required in presynaptic neurons for VCSC glia-induced presynaptic formation. In addition, we find that cdc-42 and pes-7 are also required for normal synaptogenesis during postembryonic developmental stages. PES-7 activated by CDC-42 promotes presynaptic formation, most likely through regulating F-actin assembly. Given the evolutionary conservation of CDC-42 and IQGAPs, we speculate that our findings in C. elegans apply to vertebrates.
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Affiliation(s)
- Xiaohua Dong
- Department of Neurosurgery, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Zhongshan Hospital, Fudan University, Shanghai 200032, China
| | - Shuhan Jin
- Department of Neurosurgery, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Zhongshan Hospital, Fudan University, Shanghai 200032, China
| | - Zhiyong Shao
- Department of Neurosurgery, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Zhongshan Hospital, Fudan University, Shanghai 200032, China.
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Integrins Have Cell-Type-Specific Roles in the Development of Motor Neuron Connectivity. J Dev Biol 2019; 7:jdb7030017. [PMID: 31461926 PMCID: PMC6787651 DOI: 10.3390/jdb7030017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 08/11/2019] [Accepted: 08/22/2019] [Indexed: 01/16/2023] Open
Abstract
Formation of the nervous system requires a complex series of events including proper extension and guidance of neuronal axons and dendrites. Here we investigate the requirement for integrins, a class of transmembrane cell adhesion receptors, in regulating these processes across classes of C. elegans motor neurons. We show α integrin/ina-1 is expressed by both GABAergic and cholinergic motor neurons. Despite this, our analysis of hypomorphic ina-1(gm144) mutants indicates preferential involvement of α integrin/ina-1 in GABAergic commissural development, without obvious involvement in cholinergic commissural development. The defects in GABAergic commissures of ina-1(gm144) mutants included both premature termination and guidance errors and were reversed by expression of wild type ina-1 under control of the native ina-1 promoter. Our results also show that α integrin/ina-1 is important for proper outgrowth and guidance of commissures from both embryonic and post-embryonic born GABAergic motor neurons, indicating an ongoing requirement for integrin through two phases of GABAergic neuron development. Our findings provide insights into neuron-specific roles for integrin that would not be predicted based solely upon expression analysis.
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7
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Câmara DF, Machado ML, Arantes LP, Silva TC, Silveira TL, Leal JG, Dornelles L, Stefanello ST, Soares FAA. MPMT-OX up-regulates GABAergic transmission and protects against seizure-like behavior in Caenorhabditis elegans. Neurotoxicology 2019; 74:272-281. [PMID: 31415799 DOI: 10.1016/j.neuro.2019.08.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Revised: 08/02/2019] [Accepted: 08/02/2019] [Indexed: 11/17/2022]
Abstract
The signal transmission in the nervous system operates through a sensitive balance between excitatory (E) inputs and inhibitory (I) responses. Imbalances in this system contribute to the development of pathologies such as seizures. In Caenorhabditis elegans, the locomotor circuit operates via the coordinated activity of cholinergic excitatory (E) and GABAergic inhibitory (I) transmission. Changes in E/I inputs can cause uncontrolled electrical discharges, mimicking the physiology of seizures. Molecules derived from 1,3,4-oxadiazole have been found to exhibit diverse biological activities, including anticonvulsant effect. In this work, we study the activity of the compound 2-[(4-methoxyphenylselenyl)methylthio]-5-phenyl-1,3,4-oxadiazole (MPMT-OX) in the GABAergic and cholinergic systems. We demonstrate that MPMT-OX reduced the locomotor activity of C. elegans with a normal balance between the E/I systems and increased the resistance to paralysis in worms exposed to pentylenetetrazol and aldicarb. MPMT-OX increased seizure resistance and assisted in the recovery of locomotor activity in worms with deletions in the genes unc-46, which regulates the transport of GABA into vesicles, and unc-49, which encodes the GABAA receptor. C. elegans with deletions in the unc-25 and unc-47 genes did not respond to treatment. Therefore, we suggest that the compound MPMT-OX upregulates GABAergic signaling in a manner dependent on the unc-25 gene, which is responsible for GABA synthesis, and unc-47, which encodes the vesicular GABA transporter.
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Affiliation(s)
- Daniela F Câmara
- Departamento de Bioquímica e Biologia Molecular, CCNE, Universidade Federal de Santa Maria, CEP 97.105-900 Santa Maria, RS, Brazil
| | - Marina L Machado
- Departamento de Bioquímica e Biologia Molecular, CCNE, Universidade Federal de Santa Maria, CEP 97.105-900 Santa Maria, RS, Brazil
| | - Leticia P Arantes
- Departamento de Bioquímica e Biologia Molecular, CCNE, Universidade Federal de Santa Maria, CEP 97.105-900 Santa Maria, RS, Brazil
| | - Thayanara C Silva
- Departamento de Bioquímica e Biologia Molecular, CCNE, Universidade Federal de Santa Maria, CEP 97.105-900 Santa Maria, RS, Brazil
| | - Tássia L Silveira
- Departamento de Bioquímica e Biologia Molecular, CCNE, Universidade Federal de Santa Maria, CEP 97.105-900 Santa Maria, RS, Brazil
| | - Julliano G Leal
- Departamento de Bioquímica e Biologia Molecular, CCNE, Universidade Federal de Santa Maria, CEP 97.105-900 Santa Maria, RS, Brazil
| | - Luciano Dornelles
- Departamento de Bioquímica e Biologia Molecular, CCNE, Universidade Federal de Santa Maria, CEP 97.105-900 Santa Maria, RS, Brazil
| | - Sílvio T Stefanello
- Departamento de Bioquímica e Biologia Molecular, CCNE, Universidade Federal de Santa Maria, CEP 97.105-900 Santa Maria, RS, Brazil
| | - Félix A A Soares
- Departamento de Bioquímica e Biologia Molecular, CCNE, Universidade Federal de Santa Maria, CEP 97.105-900 Santa Maria, RS, Brazil.
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Qu L, Pan C, He SM, Lang B, Gao GD, Wang XL, Wang Y. The Ras Superfamily of Small GTPases in Non-neoplastic Cerebral Diseases. Front Mol Neurosci 2019; 12:121. [PMID: 31213978 PMCID: PMC6555388 DOI: 10.3389/fnmol.2019.00121] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Accepted: 04/25/2019] [Indexed: 12/22/2022] Open
Abstract
The small GTPases from the Ras superfamily play crucial roles in basic cellular processes during practically the entire process of neurodevelopment, including neurogenesis, differentiation, gene expression, membrane and protein traffic, vesicular trafficking, and synaptic plasticity. Small GTPases are key signal transducing enzymes that link extracellular cues to the neuronal responses required for the construction of neuronal networks, as well as for synaptic function and plasticity. Different subfamilies of small GTPases have been linked to a number of non-neoplastic cerebral diseases such as Alzheimer’s disease (AD), Parkinson’s disease (PD), intellectual disability, epilepsy, drug addiction, Huntington’s disease (HD), amyotrophic lateral sclerosis (ALS) and a large number of idiopathic cerebral diseases. Here, we attempted to make a clearer illustration of the relationship between Ras superfamily GTPases and non-neoplastic cerebral diseases, as well as their roles in the neural system. In future studies, potential treatments for non-neoplastic cerebral diseases which are based on small GTPase related signaling pathways should be explored further. In this paper, we review all the available literature in support of this possibility.
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Affiliation(s)
- Liang Qu
- Department of Neurosurgery, Tangdu Hospital, Air Force Military Medical University, Xi'an, China
| | - Chao Pan
- Beijing Institute of Biotechnology, Beijing, China
| | - Shi-Ming He
- Department of Neurosurgery, Tangdu Hospital, Air Force Military Medical University, Xi'an, China.,Department of Neurosurgery, Xi'an International Medical Center, Xi'an, China
| | - Bing Lang
- The School of Medicine, Medical Sciences and Nutrition, Institute of Medical Sciences, University of Aberdeen, Aberdeen, United Kingdom.,Department of Psychiatry, The Second Xiangya Hospital, Central South University, Changsha, China
| | - Guo-Dong Gao
- Department of Neurosurgery, Tangdu Hospital, Air Force Military Medical University, Xi'an, China
| | - Xue-Lian Wang
- Department of Neurosurgery, Tangdu Hospital, Air Force Military Medical University, Xi'an, China
| | - Yuan Wang
- Department of Neurosurgery, Tangdu Hospital, Air Force Military Medical University, Xi'an, China
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Refai O, Blakely RD. Blockade and reversal of swimming-induced paralysis in C. elegans by the antipsychotic and D2-type dopamine receptor antagonist azaperone. Neurochem Int 2018; 123:59-68. [PMID: 29800604 DOI: 10.1016/j.neuint.2018.05.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2018] [Revised: 05/21/2018] [Accepted: 05/21/2018] [Indexed: 10/16/2022]
Abstract
The catecholamine neurotransmitter dopamine (DA) exerts powerful modulatory control of physiology and behavior across phylogeny. Perturbations of DA signaling in humans are associated with multiple neurodegenerative and behavioral disorders, including Parkinson's disease, attention-deficit/hyperactivity disorder, addiction and schizophrenia. In the nematode C. elegans, DA signaling regulates mating behavior, learning, food seeking and locomotion. Previously, we demonstrated that loss of function mutations in the dat-1 gene that encodes the presynaptic DA transporter (DAT-1) results in a rapid cessation of movement when animals are placed in water, termed Swimming Induced Paralysis (Swip). Loss of function mutations in genes that support DA biosynthesis, DA vesicular packaging and DA action at the extrasynaptic D2-type DA receptor DOP-3 suppress Swip in dat-1 animals, consistent with paralysis as arising from excessive DA signaling. Although animals grown on the vesicular monoamine transporter antagonist reserpine diminish Swip, the drug must be applied chronically, can impact the signaling of multiple biogenic amines, and has been reported to have penetrant, off-target actions. Here, we demonstrate that the antipsychotic drug azaperone potently and rapidly suppresses Swip behavior in either dat-1 mutants, as well as in wildtype animals treated with the DAT-1 antagonist nisoxetine, with genetic experiments consistent with DOP-3 antagonism as the mechanism of Swip suppression. Reversal of Swip in previously paralyzed dat-1 animals by azaperone application demonstrates an otherwise functionally-intact swimming circuit in these mutants. Finally, whereas azaperone suppresses DA-dependent Swip, the drug fails to attenuate the DA-independent paralysis induced by βPEA, aldicarb or genetic disruption of γ-aminobutyric acid (GABA) signaling. We discuss our findings with respect to the use of azaperone as a potent and selective tool in the identification and analysis of presynaptic mechanisms that regulate DA signaling.
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Affiliation(s)
- Osama Refai
- Department of Biomedical Science, Charles E. Schmidt College of Medicine, Florida Atlantic University, FL, USA
| | - Randy D Blakely
- Department of Biomedical Science, Charles E. Schmidt College of Medicine, Florida Atlantic University, FL, USA; Brain Institute, Florida Atlantic University, Jupiter, FL, 33458, USA.
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10
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Zhang S, Glukhova SA, Caldwell KA, Caldwell GA. NCEH-1 modulates cholesterol metabolism and protects against α-synuclein toxicity in a C. elegans model of Parkinson's disease. Hum Mol Genet 2018; 26:3823-3836. [PMID: 28934392 DOI: 10.1093/hmg/ddx269] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Accepted: 07/06/2017] [Indexed: 02/03/2023] Open
Abstract
Parkinson's disease (PD) is an aging-associated neurodegenerative disease affecting millions worldwide. Misfolding, oligomerization and accumulation of the human α-synuclein protein is a key pathological hallmark of PD and is associated with the progressive loss of dopaminergic neurons over the course of aging. Lifespan extension via the suppression of IGF-1/insulin-like signaling (IIS) offers a possibility to retard disease onset through induction of metabolic changes that provide neuroprotection. The nceh-1 gene of Caenorhabditis elegans encodes an ortholog of neutral cholesterol ester hydrolase 1 (NCEH-1), an IIS downstream protein that was identified in a screen as a modulator of α-synuclein accumulation in vivo. The mechanism whereby cholesterol metabolism functionally impacts neurodegeneration induced by α-synuclein is undefined. Here we report that NCEH-1 protects dopaminergic neurons from α-synuclein-dependent neurotoxicity in C. elegans via a mechanism that is independent of lifespan extension. We discovered that the presence of cholesterol, LDLR-mediated cholesterol endocytosis, and cholesterol efflux are all essential to NCEH-1-mediated neuroprotection. In protecting from α-synuclein neurotoxicity, NCEH-1 also stimulates cholesterol-derived neurosteroid formation and lowers cellular reactive oxygen species in mitochondria. Collectively, this study augments our understanding of how cholesterol metabolism can modulate a neuroprotective mechanism that attenuates α-synuclein neurotoxicity, thereby pointing toward regulation of neuronal cholesterol turnover as a potential therapeutic avenue for PD.
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Affiliation(s)
- Siyuan Zhang
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35487, USA
| | - Samantha A Glukhova
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35487, USA
| | - Kim A Caldwell
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35487, USA.,Departments of Neurology and Neurobiology, Center for Neurodegeneration and Experimental Therapeutics, The University of Alabama School of Medicine at Birmingham, Birmingham, AL 35294, USA
| | - Guy A Caldwell
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35487, USA.,Departments of Neurology and Neurobiology, Center for Neurodegeneration and Experimental Therapeutics, The University of Alabama School of Medicine at Birmingham, Birmingham, AL 35294, USA
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11
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Kautu BB, Phillips J, Steele K, Mengarelli MS, Nord EA. A Behavioral Survey of the Effects of Kavalactones on Caenorhabditis elegans Neuromuscular Transmission. J Exp Neurosci 2017; 11:1179069517705384. [PMID: 28615969 PMCID: PMC5462554 DOI: 10.1177/1179069517705384] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Accepted: 03/23/2017] [Indexed: 12/16/2022] Open
Abstract
Kava is a plant root extract that is widely consumed by Pacific Islanders. Kava contains a class of lactone compounds called kavalactones. The sedative and anxiolytic effects of kava are likely attributed to the efficacies of kavalactones on the nervous system. Although some studies have implicated the potencies of certain kavalactone species on γ-aminobutyric acid transmission, evidence supporting the action of kavalactones on the eukaryotic neuromuscular junction (NMJ) and acetylcholine (ACh) transmission is scant. Here, we used behavioral assays to demonstrate the effects of kavalactones at the Caenorhabditis elegans NMJ. Our results suggest that kavalactones disrupt the inhibitory-excitatory balance at the NMJ. Such perturbation of NMJ activity is likely due to excess or prolonged ACh transmission. In addition, we found that kavain, a major constituent of kava, induced worm paralysis but not convulsions. Hence, the modulatory action of kavain could be distinct from the other kavalactone species.
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Affiliation(s)
| | | | - Kellie Steele
- Department of Biology, Greenville College, Greenville, IL, USA
| | | | - Eric A Nord
- Department of Biology, Greenville College, Greenville, IL, USA
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12
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Risley MG, Kelly SP, Jia K, Grill B, Dawson-Scully K. Modulating Behavior in C. elegans Using Electroshock and Antiepileptic Drugs. PLoS One 2016; 11:e0163786. [PMID: 27668426 PMCID: PMC5036823 DOI: 10.1371/journal.pone.0163786] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 09/14/2016] [Indexed: 12/14/2022] Open
Abstract
The microscopic nematode Caenorhabditis elegans has emerged as a valuable model for understanding the molecular and cellular basis of neurological disorders. The worm offers important physiological similarities to mammalian models such as conserved neuron morphology, ion channels, and neurotransmitters. While a wide-array of behavioral assays are available in C. elegans, an assay for electroshock/electroconvulsion remains absent. Here, we have developed a quantitative behavioral method to assess the locomotor response following electric shock in C. elegans. Electric shock impairs normal locomotion, and induces paralysis and muscle twitching; after a brief recovery period, shocked animals resume normal locomotion. We tested electric shock responses in loss-of-function mutants for unc-25, which encodes the GABA biosynthetic enzyme GAD, and unc-49, which encodes the GABAA receptor. unc-25 and unc-49 mutants have decreased inhibitory GABAergic transmission to muscles, and take significantly more time to recover normal locomotion following electric shock compared to wild-type. Importantly, increased sensitivity of unc-25 and unc-49 mutants to electric shock is rescued by treatment with antiepileptic drugs, such as retigabine. Additionally, we show that pentylenetetrazol (PTZ), a GABAA receptor antagonist and proconvulsant in mammalian and C. elegans seizure models, increases susceptibility of worms to electric shock.
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Affiliation(s)
- Monica G. Risley
- Department of Biological Sciences, Florida Atlantic University, Boca Raton, Florida, United States of America
| | - Stephanie P. Kelly
- Department of Biological Sciences, Florida Atlantic University, Boca Raton, Florida, United States of America
| | - Kailiang Jia
- Department of Biological Sciences, Florida Atlantic University, Boca Raton, Florida, United States of America
| | - Brock Grill
- Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, Florida, United States of America
| | - Ken Dawson-Scully
- Department of Biological Sciences, Florida Atlantic University, Boca Raton, Florida, United States of America
- * E-mail:
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Zhang Y, Liu J, Luan G, Wang X. Inhibition of the small GTPase Cdc42 in regulation of epileptic-seizure in rats. Neuroscience 2015; 289:381-91. [PMID: 25595978 DOI: 10.1016/j.neuroscience.2014.12.059] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Revised: 12/16/2014] [Accepted: 12/16/2014] [Indexed: 11/28/2022]
Abstract
Altered expression of neuronal cytoskeletal proteins are known to play an important role in hyper-excitability of neurons in patients and animal models of epilepsy. Our previous work showed that cell division cycle 42 GTP-binding protein (Cdc42), a small GTPase of the Rho-subfamily, is significantly increased in the brain tissue of patients with temporal lobe epilepsy (TLE) and in the brain tissues of the epileptic model of rats. However, whether inhibition of Cdc42 can modify epileptic seizures has not been investigated. In this study, using a pilocarpine-induced epileptic model, we found that pretreatment with ML141, a specific inhibitor of Cdc42, reduces seizure severity. Whole-cell patch-clamp recording on CA1 pyramidal neurons in hippocampal slices from pilocarpine-induced epileptic model demonstrated that ML141 significantly inhibits the frequency of action potentials (APs), increases the amplitude and frequency of miniature inhibitory postsynaptic currents (mIPSCs), and increases the amplitude of evoked inhibitory postsynaptic currents (eIPSCs). However, ML141 did not have an impact on the miniature excitatory postsynaptic currents (mEPSCs). Our results are the first to indicate that Cdc42 plays an important role in the onset and progression of epileptic-seizures by regulating synaptic inhibition.
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Affiliation(s)
- Y Zhang
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, 1 Youyi Road, Chongqing 400016, China
| | - J Liu
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, 1 Youyi Road, Chongqing 400016, China
| | - G Luan
- Center of Epilepsy, Beijing Institute for Brain Disorders, China
| | - X Wang
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, 1 Youyi Road, Chongqing 400016, China.
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14
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VAV-1 acts in a single interneuron to inhibit motor circuit activity in Caenorhabditis elegans. Nat Commun 2014; 5:5579. [PMID: 25412913 PMCID: PMC4241504 DOI: 10.1038/ncomms6579] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2014] [Accepted: 10/15/2014] [Indexed: 11/09/2022] Open
Abstract
The complex molecular and cellular mechanisms underlying neuronal control of animal movement are not well understood. Locomotion of Caenorhabditis elegans is mediated by a neuronal circuit that produces coordinated sinusoidal movement. Here we utilize this simple, yet elegant, behaviour to show that VAV-1, a conserved guanine nucleotide exchange factor for Rho-family GTPases, negatively regulates motor circuit activity and the rate of locomotion. While vav-1 is expressed in a small subset of neurons, we find that VAV-1 function is required in a single interneuron, ALA, to regulate motor neuron circuit activity. Furthermore, we show by genetic and optogenetic manipulation of ALA that VAV-1 is required for the excitation and activation of this neuron. We find that ALA signalling inhibits command interneuron activity by abrogating excitatory signalling in the command interneurons, which is responsible for promoting motor neuron circuit activity. Together, our data describe a novel neuromodulatory role for VAV-1-dependent signalling in the regulation of motor circuit activity and locomotion.
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15
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Cunliffe VT, Baines RA, Giachello CNG, Lin WH, Morgan A, Reuber M, Russell C, Walker MC, Williams RSB. Epilepsy research methods update: Understanding the causes of epileptic seizures and identifying new treatments using non-mammalian model organisms. Seizure 2014; 24:44-51. [PMID: 25457452 DOI: 10.1016/j.seizure.2014.09.018] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Accepted: 09/23/2014] [Indexed: 12/31/2022] Open
Abstract
This narrative review is intended to introduce clinicians treating epilepsy and researchers familiar with mammalian models of epilepsy to experimentally tractable, non-mammalian research models used in epilepsy research, ranging from unicellular eukaryotes to more complex multicellular organisms. The review focuses on four model organisms: the social amoeba Dictyostelium discoideum, the roundworm Caenorhabditis elegans, the fruit fly Drosophila melanogaster and the zebrafish Danio rerio. We consider recent discoveries made with each model organism and discuss the importance of these advances for the understanding and treatment of epilepsy in humans. The relative ease with which mutations in genes of interest can be produced and studied quickly and cheaply in these organisms, together with their anatomical and physiological simplicity in comparison to mammalian species, are major advantages when researchers are trying to unravel complex disease mechanisms. The short generation times of most of these model organisms also mean that they lend themselves particularly conveniently to the investigation of drug effects or epileptogenic processes across the lifecourse.
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Affiliation(s)
- Vincent T Cunliffe
- Bateson Centre, Department of Biomedical Science, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, United Kingdom.
| | - Richard A Baines
- Faculty of Life Sciences, University of Manchester, AV Hill Building, Oxford Road, Manchester M13 9PT, United Kingdom.
| | - Carlo N G Giachello
- Faculty of Life Sciences, University of Manchester, AV Hill Building, Oxford Road, Manchester M13 9PT, United Kingdom
| | - Wei-Hsiang Lin
- Faculty of Life Sciences, University of Manchester, AV Hill Building, Oxford Road, Manchester M13 9PT, United Kingdom
| | - Alan Morgan
- Department of Molecular and Cellular Physiology, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool L69 3BX, United Kingdom.
| | - Markus Reuber
- Academic Neurology Unit, University of Sheffield, Royal Hallamshire Hospital, Glossop Road, Sheffield S10 2JF, United Kingdom.
| | - Claire Russell
- Department of Comparative Biomedical Sciences, Royal Veterinary College, Royal College Street, London NW1 0TU, United Kingdom.
| | - Matthew C Walker
- Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, Queen Square, London WC1N 3BG, United Kingdom.
| | - Robin S B Williams
- School of Biological Sciences, Royal Holloway College, University of London, Egham Hill, Egham, Surrey TW20 0EX, United Kingdom.
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Kowalski JR, Dube H, Touroutine D, Rush KM, Goodwin PR, Carozza M, Didier Z, Francis MM, Juo P. The Anaphase-Promoting Complex (APC) ubiquitin ligase regulates GABA transmission at the C. elegans neuromuscular junction. Mol Cell Neurosci 2014; 58:62-75. [PMID: 24321454 PMCID: PMC4036811 DOI: 10.1016/j.mcn.2013.12.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Revised: 11/23/2013] [Accepted: 12/02/2013] [Indexed: 01/05/2023] Open
Abstract
Regulation of both excitatory and inhibitory synaptic transmission is critical for proper nervous system function. Aberrant synaptic signaling, including altered excitatory to inhibitory balance, is observed in numerous neurological diseases. The ubiquitin enzyme system controls the abundance of many synaptic proteins and thus plays a key role in regulating synaptic transmission. The Anaphase-Promoting Complex (APC) is a multi-subunit ubiquitin ligase that was originally discovered as a key regulator of protein turnover during the cell cycle. More recently, the APC has been shown to function in postmitotic neurons, where it regulates diverse processes such as synapse development and synaptic transmission at glutamatergic synapses. Here we report that the APC regulates synaptic GABA signaling by acting in motor neurons to control the balance of excitatory (acetylcholine) to inhibitory (GABA) transmission at the Caenorhabditis elegans neuromuscular junction (NMJ). Loss-of-function mutants in multiple APC subunits have increased muscle excitation at the NMJ; this phenotype is rescued by expression of the missing subunit in GABA neurons. Quantitative imaging and electrophysiological analyses indicate that APC mutants have decreased GABA release but normal cholinergic transmission. Consistent with this, APC mutants exhibit convulsions in a seizure assay sensitive to reductions in GABA signaling. Previous studies in other systems showed that the APC can negatively regulate the levels of the active zone protein SYD-2 Liprin-α. Similarly, we found that SYD-2 accumulates in APC mutants at GABAergic presynaptic sites. Finally, we found that the APC subunit EMB-27 CDC16 can localize to presynapses in GABA neurons. Together, our data suggest a model in which the APC acts at GABAergic presynapses to promote GABA release and inhibit muscle excitation. These findings are the first evidence that the APC regulates transmission at inhibitory synapses and have implications for understanding nervous system pathologies, such as epilepsy, that are characterized by misregulated GABA signaling.
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Affiliation(s)
- Jennifer R Kowalski
- Department of Biological Sciences, Butler University, Indianapolis, IN 46208 USA.
| | - Hitesh Dube
- Department of Biological Sciences, Butler University, Indianapolis, IN 46208 USA.
| | - Denis Touroutine
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA.
| | - Kristen M Rush
- Department of Biological Sciences, Butler University, Indianapolis, IN 46208 USA.
| | - Patricia R Goodwin
- Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, Boston, MA 02111, USA.
| | - Marc Carozza
- Department of Biological Sciences, Butler University, Indianapolis, IN 46208 USA.
| | - Zachary Didier
- Department of Biological Sciences, Butler University, Indianapolis, IN 46208 USA.
| | - Michael M Francis
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA.
| | - Peter Juo
- Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, Boston, MA 02111, USA.
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17
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Using C. elegans to Decipher the Cellular and Molecular Mechanisms Underlying Neurodevelopmental Disorders. Mol Neurobiol 2013; 48:465-89. [DOI: 10.1007/s12035-013-8434-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2012] [Accepted: 02/26/2013] [Indexed: 10/27/2022]
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18
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Kautu BB, Carrasquilla A, Hicks ML, Caldwell KA, Caldwell GA. Valproic acid ameliorates C. elegans dopaminergic neurodegeneration with implications for ERK-MAPK signaling. Neurosci Lett 2013; 541:116-9. [PMID: 23485787 DOI: 10.1016/j.neulet.2013.02.026] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Revised: 12/31/2012] [Accepted: 02/13/2013] [Indexed: 10/27/2022]
Abstract
Parkinson's disease (PD) is a currently incurable neurodegenerative disorder that affects the aging population. The loss of dopaminergic neurons in the substantia nigra is one of the pathological features of PD. The precise causes of PD remain unresolved but evidence supports both environmental and genetic contributions. Current efforts for the treatment of PD are directed toward the discovery of compounds that show promise in impeding age-dependent neurodegeneration in PD patients. Alpha-synuclein (α-Syn) is a human protein that is mutated in specific populations of patients with familial PD. Overexpression of α-Syn in animal models of PD replicates key symptoms of PD, including neurodegeneration. Here, we use the nematode Caenorhabditis elegans as a model system, whereby α-Syn toxicity causes dopaminergic neurodegeneration, to test the capacity of valproic acid (VA) to protect neurons. The results of our study showed that treatment of nematodes with moderate concentrations of VA significantly protects dopaminergic neurons against α-Syn toxicity. Consistent with previously established knowledge related to the mechanistic action of VA in the cell, we showed through genetic analysis that the neuroprotection conferred by VA is inhibited by cell-specific depletion of the C. elegans ortholog of the MAP extracellular signal-regulated kinase (ERK), MPK-1, in the dopaminergic neurons. These findings suggest that VA may exert its neuroprotective effect via ERK-MAPK, or alternately could act with MAPK signaling to additively provide dopaminergic neuroprotection.
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Affiliation(s)
- Bwarenaba B Kautu
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35487, United States
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Jensen LT, Møller TH, Larsen SA, Jakobsen H, Olsen A. A new role for laminins as modulators of protein toxicity in Caenorhabditis elegans. Aging Cell 2012; 11:82-92. [PMID: 22051349 DOI: 10.1111/j.1474-9726.2011.00767.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Protein misfolding is a common theme in aging and several age-related diseases such as Alzheimer's and Parkinson's disease. The processes involved in the development of these diseases are many and complex. Here, we show that components of the basement membrane (BM), particularly laminin, affect protein integrity of the muscle cells they support. We knocked down gene expression of epi-1, a laminin α-chain, and found that this resulted in increased proteotoxicity in different Caenorhabditis elegans transgenic models, expressing aggregating proteins in the body wall muscle. The effect could partially be rescued by decreased insulin-like signaling, known to slow the aging process and the onset of various age-related diseases. Our data points to an underlying molecular mechanism involving proteasomal degradation and HSP-16 chaperone activity. Furthermore, epi-1-depleted animals had altered synaptic function and displayed hypersensitivity to both levamisole and aldicarb, an acetylcholine receptor agonist and an acetylcholinesterase inhibitor, respectively. Our results implicate the BM as an extracellular modulator of protein homeostasis in the adjacent muscle cells. This is in agreement with previous research showing that imbalance in neuromuscular signaling disturbs protein homeostasis in the postsynaptic cell. In our study, proteotoxicity may indeed be mediated by the neuromuscular junction which is part of the BM, where laminins are present in high concentration, ensuring the proper microenvironment for neuromuscular signaling. Laminins are evolutionarily conserved, and thus the BM may play a much more causal role in protein misfolding diseases than currently recognized.
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Affiliation(s)
- Louise T Jensen
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus C, Denmark
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GABAergic synaptic plasticity during a developmentally regulated sleep-like state in C. elegans. J Neurosci 2011; 31:15932-43. [PMID: 22049436 DOI: 10.1523/jneurosci.0742-11.2011] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Approximately one-fourth of the neurons in Caenorhabditis elegans adults are born during larval development, indicating tremendous plasticity in larval nervous system structure. Larval development shows cyclical expression of sleep-like quiescent behavior during lethargus periods, which occur at larval stage transitions. We studied plasticity at the neuromuscular junction during lethargus using the acetylcholinesterase inhibitor aldicarb. The rate of animal contraction when exposed to aldicarb is controlled by the balance between excitatory cholinergic and inhibitory GABAergic input on the muscle. During lethargus, there is an accelerated rate of contraction on aldicarb. Mutant analysis and optogenetic studies reveal that GABAergic synaptic transmission is reduced during lethargus. Worms in lethargus show partial resistance to GABA(A) receptor agonists, indicating that postsynaptic mechanisms contribute to lethargus-dependent plasticity. Using genetic manipulations that separate the quiescent state from the developmental stage, we show that the synaptic plasticity is dependent on developmental time and not on the behavioral state of the animal. We propose that the synaptic plasticity regulated by a developmental clock in C. elegans is analogous to synaptic plasticity regulated by the circadian clock in other species.
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