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The age factor in axonal repair after spinal cord injury: A focus on neuron-intrinsic mechanisms. Neurosci Lett 2016; 652:41-49. [PMID: 27818358 DOI: 10.1016/j.neulet.2016.11.003] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Revised: 10/26/2016] [Accepted: 11/01/2016] [Indexed: 11/27/2022]
Abstract
Age is an important consideration for recovery and repair after spinal cord injury. Spinal cord injury is increasingly affecting the middle-aged and aging populations. Despite rapid progress in research to promote axonal regeneration and repair, our understanding of how age can modulate this repair is rather limited. In this review, we discuss the literature supporting the notion of an age-dependent decline in axonal growth after central nervous system (CNS) injury. While both neuron-intrinsic and extrinsic factors are involved in the control of axon growth after injury, here we focus on possible intrinsic mechanisms for this age-dependent decline.
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52
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Promotion of Functional Nerve Regeneration by Inhibition of Microtubule Detyrosination. J Neurosci 2016; 36:3890-902. [PMID: 27053198 DOI: 10.1523/jneurosci.4486-15.2016] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Accepted: 02/26/2016] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Functional recovery of injured peripheral neurons often remains incomplete, but the clinical outcome can be improved by increasing the axonal growth rate. Adult transgenic GSK3α(S/A)/β(S/A) knock-in mice with sustained GSK3 activity show markedly accelerated sciatic nerve regeneration. Here, we unraveled the molecular mechanism underlying this phenomenon, which led to a novel pharmacological approach for the promotion of functional recovery after nerve injury.In vitroandin vivoanalysis of GSK3 single knock-in mice revealed the unexpected contribution of GSK3α in addition to GSK3β, as both GSK3(S/A) knock-ins improved axon regeneration. Moreover, growth stimulation depended on overall GSK3 activity, correlating with increased phosphorylation of microtubule-associated protein 1B and reduced microtubule detyrosination in axonal tips. Pharmacological inhibition of detyrosination by parthenolide or cnicin mimicked this axon growth promotion in wild-type animals, although it had no effect in GSK3α(S/A)/β(S/A) mice. These results support the conclusion that sustained GSK3 activity primarily targets microtubules in growing axons, maintaining them in a more dynamic state to facilitate growth. Accordingly, further manipulation of microtubule stability using either paclitaxel or nocodazole compromised the effects of parthenolide. Strikingly, either local or systemic application of parthenolide in wild-type mice dose-dependently acceleratedin vivoaxon regeneration and functional recovery similar to GSK3α(S/A)/β(S/A) mice. Thus, reducing microtubule detyrosination in axonal tips may be a novel, clinically suitable strategy to treat nerve damage. SIGNIFICANCE STATEMENT Peripheral nerve regeneration often remains incomplete, due to an insufficient growth rate of injured axons. Transgenic mice with sustained GSK3 activity showed markedly accelerated nerve regeneration upon injury. Here, we identified the molecular mechanism underlying this phenomenon and provide a novel therapeutic principle for promoting nerve repair. Analysis of transgenic mice revealed a dependence on overall GSK3 activity and reduction of microtubule detyrosination in axonal tips. Pharmacological inhibition of detyrosination by parthenolide fully mimicked this axon growth promotion in wild-type mice. Strikingly, local or systemic treatment with parthenolidein vivomarkedly accelerated axon regeneration and functional recovery. Thus, pharmacological inhibition of microtubule detyrosination may be a novel, clinically suitable strategy for nerve repair with potential relevance for human patients.
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53
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Zuo YC, Xiong NX, Zhao HY. Stereotactic injection of shrna GSK-3β-AAV promotes axonal regeneration after spinal cord injury. ACTA ACUST UNITED AC 2016; 36:548-553. [PMID: 27465331 DOI: 10.1007/s11596-016-1623-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Accepted: 06/25/2016] [Indexed: 01/14/2023]
Abstract
Evidence suggested that glycogen synthase kinase-3β (GSK-3β) is involved in Nogo-66 inhibiting axonal regeneration in vitro, but its effect in vivo was poorly understood. We showed that stereotactic injection of shRNA GSK-3β-adeno associated virus (GSK-3β-AAV) diminished syringomyelia and promoted axonal regeneration after spinal cord injury (SCI), using stereotactic injection of shRNA GSK-3β-AAV (tested with Western blotting and RT-PCR) into the sensorimotor cortex of rats with SCI and by the detection of biotin dextran amine (BDA)-labeled axonal regeneration. We also determined the right position to inject into the sensorimotor cortex. Our findings consolidate the hypothesis that downregulation of GSK-3β promotes axonal regeneration after SCI.
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Affiliation(s)
- Yu-Chao Zuo
- Department of Neurosurgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China.,Department of Neurosurgery, the First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, China
| | - Nan-Xiang Xiong
- Department of Neurosurgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China.
| | - Hong-Yang Zhao
- Department of Neurosurgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China.
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54
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Nagai J, Takaya R, Piao W, Goshima Y, Ohshima T. Deletion of Crmp4 attenuates CSPG-induced inhibition of axonal growth and induces nociceptive recovery after spinal cord injury. Mol Cell Neurosci 2016; 74:42-8. [PMID: 26995506 DOI: 10.1016/j.mcn.2016.03.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 03/15/2016] [Indexed: 01/01/2023] Open
Abstract
The capacity for regeneration in the injured adult mammalian central nervous system (CNS) is largely limited by potent inhibitory barriers. Chondroitin sulfate proteoglycans (CSPGs) are major inhibitors of axonal regeneration/sprouting and accumulate at lesion sites after CNS trauma. Despite extensive research during the two decades since their discovery, the molecular mechanisms remain elusive, including intracellular phosphorylation events. Collapsin response mediator protein 4 (CRMP4) is known to directly regulate cytoskeletal dynamics and neurite extension, while phosphorylated CRMP4 loses its binding affinity for cytoskeletal proteins. We have previously found that spinal cord injury (SCI) induces CRMP4 upregulation and phosphorylation and that CRMP4 knockout (Crmp4-/-) mice show behavioral recovery of locomotor function after SCI. However, the role of CRMP4 in the recovery of other forms of physiological function such as sensation remains largely unknown. We here have demonstrated CRMP4 involvement in CSPG-induced inhibitory signaling and nociceptive recovery in Crmp4-/- mice after SCI. We cultured dorsal root ganglion (DRG) neurons on CSPG-coated dishes; Crmp4 deletion overrode CSPG-induced inhibition of axon growth in vitro. CRMP4 levels were increased in DRGs in vivo after SCI. Crmp4-/- mice exhibited axonal growth of sensory neurons and recovery of nociceptive function after spinal transection. These results support Crmp4 deletion as a therapeutic target in the treatment of SCI.
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Affiliation(s)
- Jun Nagai
- Department of Life Science and Medical Bioscience, Graduate School of Advanced Science and Engineering, Waseda University, TWIns, Tokyo 162-8480, Japan; Research Fellow of Japan Society for the Promotion of Science, Japan
| | - Ryosuke Takaya
- Department of Life Science and Medical Bioscience, Graduate School of Advanced Science and Engineering, Waseda University, TWIns, Tokyo 162-8480, Japan
| | - Wenhui Piao
- Department of Life Science and Medical Bioscience, Graduate School of Advanced Science and Engineering, Waseda University, TWIns, Tokyo 162-8480, Japan
| | - Yoshio Goshima
- Department of Molecular Pharmacology and Neurobiology, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Toshio Ohshima
- Department of Life Science and Medical Bioscience, Graduate School of Advanced Science and Engineering, Waseda University, TWIns, Tokyo 162-8480, Japan.
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55
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Nagai J, Baba R, Ohshima T. CRMPs Function in Neurons and Glial Cells: Potential Therapeutic Targets for Neurodegenerative Diseases and CNS Injury. Mol Neurobiol 2016; 54:4243-4256. [PMID: 27339876 DOI: 10.1007/s12035-016-0005-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2016] [Accepted: 06/14/2016] [Indexed: 12/19/2022]
Abstract
Neurodegeneration in the adult mammalian central nervous system (CNS) is fundamentally accelerated by its intrinsic neuronal mechanisms, including its poor regenerative capacity and potent extrinsic inhibitory factors. Thus, the treatment of neurodegenerative diseases faces many obstacles. The degenerative processes, consisting of axonal/dendritic structural disruption, abnormal axonal transport, release of extracellular factors, and inflammation, are often controlled by the cytoskeleton. From this perspective, regulators of the cytoskeleton could potentially be a therapeutic target for neurodegenerative diseases and CNS injury. Collapsin response mediator proteins (CRMPs) are known to regulate the assembly of cytoskeletal proteins in neurons, as well as control axonal growth and neural circuit formation. Recent studies have provided some novel insights into the roles of CRMPs in several inhibitory signaling pathways of neurodegeneration, in addition to its functions in neurological disorders and CNS repair. Here, we summarize the roles of CRMPs in axon regeneration and its emerging functions in non-neuronal cells, especially in inflammatory responses. We also discuss the direct and indirect targeting of CRMPs as a novel therapeutic strategy for neurological diseases.
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Affiliation(s)
- Jun Nagai
- Department of Life Science and Medical Bioscience, Graduate School of Advanced Science and Engineering, Waseda University, TWIns, 2-2 Wakamatsu-cho Shinjuku-ku, Tokyo, 162-8480, Japan.,Research Fellow of Japan Society for the Promotion of Science, Tokyo, Japan
| | - Rina Baba
- Department of Life Science and Medical Bioscience, Graduate School of Advanced Science and Engineering, Waseda University, TWIns, 2-2 Wakamatsu-cho Shinjuku-ku, Tokyo, 162-8480, Japan
| | - Toshio Ohshima
- Department of Life Science and Medical Bioscience, Graduate School of Advanced Science and Engineering, Waseda University, TWIns, 2-2 Wakamatsu-cho Shinjuku-ku, Tokyo, 162-8480, Japan.
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56
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Wu C, Cui Z, Liu Y, Zhang J, Ding W, Wang S, Bao G, Xu G, Sun Y, Chen J. The importance of EHD1 in neurite outgrowth contributing to the functional recovery after spinal cord injury. Int J Dev Neurosci 2016; 52:24-32. [PMID: 27211346 DOI: 10.1016/j.ijdevneu.2016.05.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2016] [Revised: 05/11/2016] [Accepted: 05/18/2016] [Indexed: 11/15/2022] Open
Affiliation(s)
- Chunshuai Wu
- Department of Spine Surgery, The Second Affiliated Hospital of Nantong University, Nantong University, Haier Lane North Road No. 6, Nantong, 226001, Jiangsu, People's Republic of China; Jiangsu Province Key Laboratory for Inflammation and Molecular Drug Target, Medical College, Nantong University, Nantong, 226001, Jiangsu, People's Republic of China
| | - Zhiming Cui
- Department of Spine Surgery, The Second Affiliated Hospital of Nantong University, Nantong University, Haier Lane North Road No. 6, Nantong, 226001, Jiangsu, People's Republic of China; Jiangsu Province Key Laboratory for Inflammation and Molecular Drug Target, Medical College, Nantong University, Nantong, 226001, Jiangsu, People's Republic of China.
| | - Yonghua Liu
- Jiangsu Province Key Laboratory for Inflammation and Molecular Drug Target, Medical College, Nantong University, Nantong, 226001, Jiangsu, People's Republic of China
| | - Jinlong Zhang
- Department of Spine Surgery, The Second Affiliated Hospital of Nantong University, Nantong University, Haier Lane North Road No. 6, Nantong, 226001, Jiangsu, People's Republic of China
| | - Wensen Ding
- Jiangsu Province Key Laboratory for Inflammation and Molecular Drug Target, Medical College, Nantong University, Nantong, 226001, Jiangsu, People's Republic of China
| | - Song Wang
- Department of Spine Surgery, The Second Affiliated Hospital of Nantong University, Nantong University, Haier Lane North Road No. 6, Nantong, 226001, Jiangsu, People's Republic of China; Jiangsu Province Key Laboratory for Inflammation and Molecular Drug Target, Medical College, Nantong University, Nantong, 226001, Jiangsu, People's Republic of China
| | - Guofeng Bao
- Department of Spine Surgery, The Second Affiliated Hospital of Nantong University, Nantong University, Haier Lane North Road No. 6, Nantong, 226001, Jiangsu, People's Republic of China
| | - Guanhua Xu
- Department of Spine Surgery, The Second Affiliated Hospital of Nantong University, Nantong University, Haier Lane North Road No. 6, Nantong, 226001, Jiangsu, People's Republic of China
| | - Yuyu Sun
- Department of Spine Surgery, The Second Affiliated Hospital of Nantong University, Nantong University, Haier Lane North Road No. 6, Nantong, 226001, Jiangsu, People's Republic of China
| | - Jiajia Chen
- Department of Spine Surgery, The Second Affiliated Hospital of Nantong University, Nantong University, Haier Lane North Road No. 6, Nantong, 226001, Jiangsu, People's Republic of China
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57
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Eira J, Silva CS, Sousa MM, Liz MA. The cytoskeleton as a novel therapeutic target for old neurodegenerative disorders. Prog Neurobiol 2016; 141:61-82. [PMID: 27095262 DOI: 10.1016/j.pneurobio.2016.04.007] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Revised: 04/13/2016] [Accepted: 04/13/2016] [Indexed: 12/12/2022]
Abstract
Cytoskeleton defects, including alterations in microtubule stability, in axonal transport as well as in actin dynamics, have been characterized in several unrelated neurodegenerative conditions. These observations suggest that defects of cytoskeleton organization may be a common feature contributing to neurodegeneration. In line with this hypothesis, drugs targeting the cytoskeleton are currently being tested in animal models and in human clinical trials, showing promising effects. Drugs that modulate microtubule stability, inhibitors of posttranslational modifications of cytoskeletal components, specifically compounds affecting the levels of tubulin acetylation, and compounds targeting signaling molecules which regulate cytoskeleton dynamics, constitute the mostly addressed therapeutic interventions aiming at preventing cytoskeleton damage in neurodegenerative disorders. In this review, we will discuss in a critical perspective the current knowledge on cytoskeleton damage pathways as well as therapeutic strategies designed to revert cytoskeleton-related defects mainly focusing on the following neurodegenerative disorders: Alzheimer's Disease, Parkinson's Disease, Huntington's Disease, Amyotrophic Lateral Sclerosis and Charcot-Marie-Tooth Disease.
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Affiliation(s)
- Jessica Eira
- Neurodegeneration Group, IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200 Porto, Portugal; Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200 Porto, Portugal
| | - Catarina Santos Silva
- Neurodegeneration Group, IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200 Porto, Portugal; Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200 Porto, Portugal
| | - Mónica Mendes Sousa
- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200 Porto, Portugal; Nerve Regeneration Group, IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200 Porto, Portugal
| | - Márcia Almeida Liz
- Neurodegeneration Group, IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200 Porto, Portugal; Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200 Porto, Portugal.
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58
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Callahan A, Abeyruwan SW, Al-Ali H, Sakurai K, Ferguson AR, Popovich PG, Shah NH, Visser U, Bixby JL, Lemmon VP. RegenBase: a knowledge base of spinal cord injury biology for translational research. DATABASE-THE JOURNAL OF BIOLOGICAL DATABASES AND CURATION 2016; 2016:baw040. [PMID: 27055827 PMCID: PMC4823819 DOI: 10.1093/database/baw040] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 03/03/2016] [Indexed: 12/20/2022]
Abstract
Spinal cord injury (SCI) research is a data-rich field that aims to identify the biological mechanisms resulting in loss of function and mobility after SCI, as well as develop therapies that promote recovery after injury. SCI experimental methods, data and domain knowledge are locked in the largely unstructured text of scientific publications, making large scale integration with existing bioinformatics resources and subsequent analysis infeasible. The lack of standard reporting for experiment variables and results also makes experiment replicability a significant challenge. To address these challenges, we have developed RegenBase, a knowledge base of SCI biology. RegenBase integrates curated literature-sourced facts and experimental details, raw assay data profiling the effect of compounds on enzyme activity and cell growth, and structured SCI domain knowledge in the form of the first ontology for SCI, using Semantic Web representation languages and frameworks. RegenBase uses consistent identifier schemes and data representations that enable automated linking among RegenBase statements and also to other biological databases and electronic resources. By querying RegenBase, we have identified novel biological hypotheses linking the effects of perturbagens to observed behavioral outcomes after SCI. RegenBase is publicly available for browsing, querying and download. Database URL:http://regenbase.org
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Affiliation(s)
- Alison Callahan
- Stanford Center for Biomedical Informatics Research, Stanford University, Stanford, CA 94305
| | | | - Hassan Al-Ali
- Miami Project to Cure Paralysis, University of Miami School of Medicine, Miami, FL 33136
| | - Kunie Sakurai
- Miami Project to Cure Paralysis, University of Miami School of Medicine, Miami, FL 33136
| | - Adam R Ferguson
- Brain and Spinal Injury Center (BASIC), Department of Neurological Surgery, University of California, San Francisco; San Francisco Veterans Affairs Medical Center, San Francisco, CA 94143
| | - Phillip G Popovich
- Center for Brain and Spinal Cord Repair and the Department of Neuroscience, The Ohio State University, Columbus, OH 43210
| | - Nigam H Shah
- Stanford Center for Biomedical Informatics Research, Stanford University, Stanford, CA 94305
| | - Ubbo Visser
- Department of Computer Science, University of Miami, Coral Gables, FL 33146
| | - John L Bixby
- Miami Project to Cure Paralysis, University of Miami School of Medicine, Miami, FL 33136 Center for Computational Science, University of Miami, Coral Gables, FL 33146 Department of Cellular and Molecular Pharmacology, University of Miami School of Medicine, Miami, FL 33136, USA
| | - Vance P Lemmon
- Miami Project to Cure Paralysis, University of Miami School of Medicine, Miami, FL 33136 Center for Computational Science, University of Miami, Coral Gables, FL 33146
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59
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Guo X, Snider WD, Chen B. GSK3β regulates AKT-induced central nervous system axon regeneration via an eIF2Bε-dependent, mTORC1-independent pathway. eLife 2016; 5:e11903. [PMID: 26974342 PMCID: PMC4805534 DOI: 10.7554/elife.11903] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2015] [Accepted: 02/26/2016] [Indexed: 01/03/2023] Open
Abstract
Axons fail to regenerate after central nervous system (CNS) injury. Modulation of the PTEN/mTORC1 pathway in retinal ganglion cells (RGCs) promotes axon regeneration after optic nerve injury. Here, we report that AKT activation, downstream of Pten deletion, promotes axon regeneration and RGC survival. We further demonstrate that GSK3β plays an indispensable role in mediating AKT-induced axon regeneration. Deletion or inactivation of GSK3β promotes axon regeneration independently of the mTORC1 pathway, whereas constitutive activation of GSK3β reduces AKT-induced axon regeneration. Importantly, we have identified eIF2Bε as a novel downstream effector of GSK3β in regulating axon regeneration. Inactivation of eIF2Bε reduces both GSK3β and AKT-mediated effects on axon regeneration. Constitutive activation of eIF2Bε is sufficient to promote axon regeneration. Our results reveal a key role of the AKT-GSK3β-eIF2Bε signaling module in regulating axon regeneration in the adult mammalian CNS. DOI:http://dx.doi.org/10.7554/eLife.11903.001 The central nervous system consists of the neurons that make up the brain, retina, and spinal cord. Neurons transmit electrical signals along a cable-like structure called an axon. However, an axon cannot regenerate itself, and so injuries that crush or sever the axons can lead to permanent damage. This happens for two reasons: neurons don’t have the same regenerative ability as other cells, and the environment in the central nervous system restricts cell growth. The optic nerve transmits visual information from the eye to the brain. Studies in mice with a damaged optic nerve show that it is possible to regenerate the axons of neurons that lack a protein known as PTEN. These studies revealed one molecular pathway by which eliminating PTEN helps to boost the regrowth of axons. Now, Guo et al. identify another independent pathway by which eliminating PTEN helps promote axon regeneration in damaged mouse optic nerves. This pathway starts with a growth-promoting enzyme called AKT, which is turned on in neurons that lack PTEN. Indeed, injecting mice with an active form of this enzyme caused the optic nerve fiber to regrow in mice whose optic nerve had been crushed. Further experiments revealed that AKT activates a pathway in which another enzyme called GSK3β acts on a protein called eIF2Bε. A future challenge is to simultaneously manipulate the different signaling pathways that have been linked to axon regrowth to investigate whether this combined approach could help repair damage to the central nervous system. DOI:http://dx.doi.org/10.7554/eLife.11903.002
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Affiliation(s)
- Xinzheng Guo
- Department of Ophthalmology and Visual Science, Yale University School of Medicine, New Haven, United States
| | - William D Snider
- UNC Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, United States
| | - Bo Chen
- Department of Ophthalmology and Visual Science, Yale University School of Medicine, New Haven, United States.,Department of Neurobiology, Yale University School of Medicine, New Haven, United States
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60
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Inhibition of CRMP2 phosphorylation repairs CNS by regulating neurotrophic and inhibitory responses. Exp Neurol 2016; 277:283-295. [PMID: 26795088 DOI: 10.1016/j.expneurol.2016.01.015] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2015] [Revised: 12/22/2015] [Accepted: 01/17/2016] [Indexed: 01/08/2023]
Abstract
Central nervous system (CNS) regeneration is restricted by both the lack of neurotrophic responses and the presence of inhibitory factors. As of yet, a common mediator of these two pathways has not been identified. Microtubule dynamics is responsible for several key processes after CNS injuries: intracellular trafficking of receptors for neurotrophic factors, axonal retraction by inhibitory factors, and secondary tissue damages by inflammation and scarring. Kinases regulating microtubule organization, such as Cdk5 or GSK3β, may play pivotal roles during CNS recovery, but the molecular mechanisms remain to be elucidated. Collapsin response mediator protein 2 (CRMP2) stabilizes cytoskeletal polymerization, while CRMP2 phosphorylation by Cdk5 and GSK3β loses its affinity for cytoskeleton proteins, leading to the inhibition of axonal growth. Here, we characterized CRMP2 phosphorylation as the first crucial factor regulating neurotrophic and inhibitory responses after spinal cord injury (SCI). We found that pharmacological inhibition of GSK3β enhanced brain-derived neurotrophic factor (BDNF)-induced axonal growth response in cultured dorsal root ganglion (DRG) neurons. DRG neurons from CRMP2 knock-in (Crmp2KI/KI) mice, where CRMP2 phosphorylation was eliminated, showed elevated sensitivity to BDNF as well. Additionally, cultured Crmp2KI/KI neurons exhibited suppressed axonal growth inhibition by chondroitin sulfate proteoglycan (CSPG). These data suggest a couple of new molecular insights: the BDNF/GSK3β/CRMP2 and CSPG/GSK3β/CRMP2 pathways. Next, we tested the significance of CRMP2 phosphorylation after CNS injury in vivo. The phosphorylation level of CRMP2 was enhanced in the injured spinal cord. Crmp2KI/KI mice exhibited prominent recovery of locomotive and nociceptive functions after SCI, which correlated with the enhanced axonal growth of the motor and sensory neurons. Neuroprotective effects against SCI, such as microtubule stabilization, reduced inflammation, and suppressed scarring were also observed by inhibiting CRMP2 phosphorylation. Therefore, inhibition of CRMP2 phosphorylation demonstrates the unique potential to repair SCI by both enhancing sensitivity to BDNF and reducing inhibitory responses.
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61
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Berry M, Ahmed Z, Morgan-Warren P, Fulton D, Logan A. Prospects for mTOR-mediated functional repair after central nervous system trauma. Neurobiol Dis 2015; 85:99-110. [PMID: 26459109 DOI: 10.1016/j.nbd.2015.10.002] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Revised: 09/09/2015] [Accepted: 10/08/2015] [Indexed: 02/07/2023] Open
Abstract
Recent research has suggested that the growth of central nervous system (CNS) axons during development is mediated through the PI3K/Akt/mammalian target of rapamycin (mTOR) intracellular signalling axis and that suppression of activity in this pathway occurs during maturity as levels of the phosphatase and tensin homologue (PTEN) rise and inhibit PI3K activation of mTOR, accounting for the failure of axon regeneration in the injured adult CNS. This hypothesis is supported by findings confirming that suppression of PTEN in experimental adult animals promotes impressive axon regeneration in the injured visual and corticospinal motor systems. This review focuses on these recent developments, discussing the therapeutic potential of a mTOR-based treatment aimed at promoting functional recovery in CNS trauma patients, recognising that to fulfil this ambition, the new therapy should aim to promote not only axon regeneration but also remyelination of regenerated axons, neuronal survival and re-innervation of denervated targets through accurate axonal guidance and synaptogenesis, all with minimal adverse effects. The translational challenges presented by the implementation of this new axogenic therapy are also discussed.
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Affiliation(s)
- Martin Berry
- Neurotrauma Research Group, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Zubair Ahmed
- Neurotrauma Research Group, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
| | - Peter Morgan-Warren
- Neurotrauma Research Group, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Daniel Fulton
- Neurotrauma Research Group, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Ann Logan
- Neurotrauma Research Group, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
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62
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Jiang JJ, Liu CM, Zhang BY, Wang XW, Zhang M, Saijilafu, Zhang SR, Hall P, Hu YW, Zhou FQ. MicroRNA-26a supports mammalian axon regeneration in vivo by suppressing GSK3β expression. Cell Death Dis 2015; 6:e1865. [PMID: 26313916 PMCID: PMC4558520 DOI: 10.1038/cddis.2015.239] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Revised: 06/08/2015] [Accepted: 06/19/2015] [Indexed: 01/03/2023]
Abstract
MicroRNAs are emerging to be important epigenetic factors that control axon regeneration. Here, we report that microRNA-26a (miR-26a) is a physiological regulator of mammalian axon regeneration in vivo. We demonstrated that endogenous miR-26a acted to target specifically glycogen synthase kinase 3β (GSK3β) in adult mouse sensory neurons in vitro and in vivo. Inhibition of endogenous miR-26a in sensory neurons impaired axon regeneration in vitro and in vivo. Moreover, the regulatory effect of miR-26a was mediated by increased expression of GSK3β because downregulation or pharmacological inhibition of GSK3β fully rescued axon regeneration. Our results also suggested that the miR-26a-GSK3β pathway regulated axon regeneration at the neuronal soma by controlling gene expression. We provided biochemical and functional evidences that the regeneration-associated transcription factor Smad1 acted downstream of miR-26a and GSK3β to control sensory axon regeneration. Our study reveals a novel miR-26a-GSK3β-Smad1 signaling pathway in the regulation of mammalian axon regeneration. Moreover, we provide the first evidence that, in addition to inhibition of GSK3β kinase activity, maintaining a lower protein level of GSK3β in neurons by the microRNA is necessary for efficient axon regeneration.
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Affiliation(s)
- J-J Jiang
- Department of Anesthesiology, Shengjing Hospital of China Medical University, Shenyang, Liaoning 110004, People's Republic of China.,Department of Orthopaedic Surgery and Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - C-M Liu
- Department of Orthopaedic Surgery and Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA.,State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100190, People's Repubic of China
| | - B-Y Zhang
- Department of Orthopaedic Surgery and Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - X-W Wang
- Department of Orthopaedic Surgery and Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - M Zhang
- Department of Orthopaedic Surgery and Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - Saijilafu
- Department of Orthopaedic Surgery and Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA.,Department of Orthopaedics, the First Affiliated Hospital, Orthopaedic Institute, Soochow University, Suzhou 215123, Jiangsu, People's Republic of China
| | - S-R Zhang
- Department of Orthopaedic Surgery and Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - P Hall
- Department of Orthopaedic Surgery and Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - Y-W Hu
- Department of Orthopaedic Surgery and Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - F-Q Zhou
- Department of Orthopaedic Surgery and Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA.,The Solomon H Snyder Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore 21287, MD, USA
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Inhibitory Injury Signaling Represses Axon Regeneration After Dorsal Root Injury. Mol Neurobiol 2015; 53:4596-605. [PMID: 26298667 DOI: 10.1007/s12035-015-9397-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Accepted: 08/14/2015] [Indexed: 01/05/2023]
Abstract
Following injury to peripheral axons, besides increased cyclic adenosine monophosphate (cAMP), the positive injury signals extracellular-signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and signal transducer and activator of transcription 3 (STAT-3) are locally activated and retrogradely transported to the cell body, where they induce a pro-regenerative program. Here, to further understand the importance of injury signaling for successful axon regeneration, we used dorsal root ganglia (DRG) neurons that have a central branch without regenerative capacity and a peripheral branch that regrows after lesion. Although injury to the DRG central branch (dorsal root injury (DRI)) activated ERK, JNK, and STAT-3 and increased cAMP levels, it did not elicit gain of intrinsic growth capacity nor the ability to overcome myelin inhibition, as occurred after peripheral branch injury (sciatic nerve injury (SNI)). Besides, gain of growth capacity after SNI was independent of ERK and cAMP. Antibody microarrays of dynein-immunoprecipitated axoplasm from rats with either DRI or SNI revealed a broad differential activation and transport of signals after each injury type and further supported that ERK, JNK, STAT-3, and cAMP signaling pathways are minor contributors to the differential intrinsic axon growth capacity of both injury models. Increased levels of inhibitory injury signals including GSK3β and ROCKII were identified after DRI, not only in axons but also in DRG cell bodies. In summary, our work shows that activation and transport of positive injury signals are not sufficient to promote increased axon growth capacity and that differential modulation of inhibitory molecules may contribute to limited regenerative response.
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Gong X, Zhang L, Huang T, Lin TV, Miyares L, Wen J, Hsieh L, Bordey A. Activating the translational repressor 4E-BP or reducing S6K-GSK3β activity prevents accelerated axon growth induced by hyperactive mTOR in vivo. Hum Mol Genet 2015. [PMID: 26220974 DOI: 10.1093/hmg/ddv295] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Abnormal axonal connectivity and hyperactive mTOR complex 1 (mTORC1) are shared features of several neurological disorders. Hyperactive mTORC1 alters axon length and polarity of hippocampal neurons in vitro, but the impact of hyperactive mTORC1 on axon growth in vivo and the mechanisms underlying those effects remain unclear. Using in utero electroporation during corticogenesis, we show that increasing mTORC1 activity accelerates axon growth without multiple axon formation. This was prevented by counteracting mTORC1 signaling through p70S6Ks (S6K1/2) or eukaryotic initiation factor 4E-binding protein (4E-BP1/2), which both regulate translation. In addition to regulating translational targets, S6K1 indirectly signals through GSK3β, a regulator of axogenesis. Although blocking GSK3β activity did not alter axon growth under physiological conditions in vivo, blocking it using a dominant-negative mutant or lithium chloride prevented mTORC1-induced accelerated axon growth. These data reveal the contribution of translational and non-translational downstream effectors such as GSK3β to abnormal axon growth in neurodevelopmental mTORopathies and open new therapeutic options for restoring long-range connectivity.
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Affiliation(s)
- Xuan Gong
- Department of Neurosurgery, Xiangya Hospital, Central South University, 85 Xiangya Street, Changsha 410008, China, Department of Neurosurgery and Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520-8082, USA
| | - Longbo Zhang
- Department of Neurosurgery, Xiangya Hospital, Central South University, 85 Xiangya Street, Changsha 410008, China, Department of Neurosurgery and Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520-8082, USA
| | - Tianxiang Huang
- Department of Neurosurgery, Xiangya Hospital, Central South University, 85 Xiangya Street, Changsha 410008, China, Department of Neurosurgery and Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520-8082, USA
| | - Tiffany V Lin
- Department of Neurosurgery and Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520-8082, USA
| | - Laura Miyares
- Department of Neurosurgery and Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520-8082, USA
| | - John Wen
- Department of Neurosurgery and Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520-8082, USA
| | - Lawrence Hsieh
- Department of Neurosurgery and Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520-8082, USA
| | - Angélique Bordey
- Department of Neurosurgery and Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520-8082, USA
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Cho Y, Park D, Cavalli V. Filamin A is required in injured axons for HDAC5 activity and axon regeneration. J Biol Chem 2015; 290:22759-70. [PMID: 26157139 DOI: 10.1074/jbc.m115.638445] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Indexed: 11/06/2022] Open
Abstract
Microtubule dynamics are important for axon growth during development as well as axon regeneration after injury. We have previously identified HDAC5 as an injury-regulated tubulin deacetylase that functions at the injury site to promote axon regeneration. However, the mechanisms involved in the spatial control of HDAC5 activity remain poorly understood. Here we reveal that HDAC5 interacts with the actin binding protein filamin A via its C-terminal domain. Filamin A plays critical roles in HDAC5-dependent tubulin deacetylation because, in cells lacking filamin A, the levels of acetylated tubulin are elevated markedly. We found that nerve injury increases filamin A axonal expression in a protein synthesis-dependent manner. Reducing filamin A levels or interfering with the interaction between HDAC5 and filamin A prevents injury-induced tubulin deacetylation as well as HDAC5 localization at the injured axon tips. In addition, neurons lacking filamin A display reduced axon regeneration. Our findings suggest a model in which filamin A local translation following axon injury controls localized HDAC5 activity to promote axon regeneration.
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Affiliation(s)
- Yongcheol Cho
- From the Department of Anatomy and Neurobiology, Washington University in St. Louis, School of Medicine, St. Louis, Missouri 63110 and
| | - Dongeun Park
- the School of Biological Sciences, Seoul National University, Seoul 151-742, Republic of Korea
| | - Valeria Cavalli
- From the Department of Anatomy and Neurobiology, Washington University in St. Louis, School of Medicine, St. Louis, Missouri 63110 and
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Ribeiro FF, Neves-Tomé R, Assaife-Lopes N, Santos TE, Silva RFM, Brites D, Ribeiro JA, Sousa MM, Sebastião AM. Axonal elongation and dendritic branching is enhanced by adenosine A2A receptors activation in cerebral cortical neurons. Brain Struct Funct 2015; 221:2777-99. [DOI: 10.1007/s00429-015-1072-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 05/27/2015] [Indexed: 01/09/2023]
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Jackson BC, Ivanova IA, Dagnino L. An ELMO2-RhoG-ILK network modulates microtubule dynamics. Mol Biol Cell 2015; 26:2712-25. [PMID: 25995380 PMCID: PMC4501367 DOI: 10.1091/mbc.e14-10-1444] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Accepted: 05/12/2015] [Indexed: 12/19/2022] Open
Abstract
Complexes that contain ELMO2, RhoG, and integrin-linked kinase are required to maintain microtubule stability. Mechanistically, these complexes are involved in activation of Rac1, which in turn interferes with the destabilizing activity of stathmin. In addition, these complexes also mediate activation of GSK-3β, which promotes CRMP2-mediated microtubule stabilization. ELMO2 belongs to a family of scaffold proteins involved in phagocytosis and cell motility. ELMO2 can simultaneously bind integrin-linked kinase (ILK) and RhoG, forming tripartite ERI complexes. These complexes are involved in promoting β1 integrin–dependent directional migration in undifferentiated epidermal keratinocytes. ELMO2 and ILK have also separately been implicated in microtubule regulation at integrin-containing focal adhesions. During differentiation, epidermal keratinocytes cease to express integrins, but ERI complexes persist. Here we show an integrin-independent role of ERI complexes in modulation of microtubule dynamics in differentiated keratinocytes. Depletion of ERI complexes by inactivating the Ilk gene in these cells reduces microtubule growth and increases the frequency of catastrophe. Reciprocally, exogenous expression of ELMO2 or RhoG stabilizes microtubules, but only if ILK is also present. Mechanistically, activation of Rac1 downstream from ERI complexes mediates their effects on microtubule stability. In this pathway, Rac1 serves as a hub to modulate microtubule dynamics through two different routes: 1) phosphorylation and inactivation of the microtubule-destabilizing protein stathmin and 2) phosphorylation and inactivation of GSK-3β, which leads to the activation of CRMP2, promoting microtubule growth. At the cellular level, the absence of ERI species impairs Ca2+-mediated formation of adherens junctions, critical to maintaining mechanical integrity in the epidermis. Our findings support a key role for ERI species in integrin-independent stabilization of the microtubule network in differentiated keratinocytes.
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Affiliation(s)
- Bradley C Jackson
- Department of Physiology and Pharmacology, Children's Health Research Institute, and Lawson Health Research Institute, University of Western Ontario, London, ON N6A 5C1, Canada
| | - Iordanka A Ivanova
- Department of Physiology and Pharmacology, Children's Health Research Institute, and Lawson Health Research Institute, University of Western Ontario, London, ON N6A 5C1, Canada
| | - Lina Dagnino
- Department of Physiology and Pharmacology, Children's Health Research Institute, and Lawson Health Research Institute, University of Western Ontario, London, ON N6A 5C1, Canada
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