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Chambel SS, Cruz CD. Axonal growth inhibitors and their receptors in spinal cord injury: from biology to clinical translation. Neural Regen Res 2023; 18:2573-2581. [PMID: 37449592 DOI: 10.4103/1673-5374.373674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/18/2023] Open
Abstract
Axonal growth inhibitors are released during traumatic injuries to the adult mammalian central nervous system, including after spinal cord injury. These molecules accumulate at the injury site and form a highly inhibitory environment for axonal regeneration. Among these inhibitory molecules, myelin-associated inhibitors, including neurite outgrowth inhibitor A, oligodendrocyte myelin glycoprotein, myelin-associated glycoprotein, chondroitin sulfate proteoglycans and repulsive guidance molecule A are of particular importance. Due to their inhibitory nature, they represent exciting molecular targets to study axonal inhibition and regeneration after central injuries. These molecules are mainly produced by neurons, oligodendrocytes, and astrocytes within the scar and in its immediate vicinity. They exert their effects by binding to specific receptors, localized in the membranes of neurons. Receptors for these inhibitory cues include Nogo receptor 1, leucine-rich repeat, and Ig domain containing 1 and p75 neurotrophin receptor/tumor necrosis factor receptor superfamily member 19 (that form a receptor complex that binds all myelin-associated inhibitors), and also paired immunoglobulin-like receptor B. Chondroitin sulfate proteoglycans and repulsive guidance molecule A bind to Nogo receptor 1, Nogo receptor 3, receptor protein tyrosine phosphatase σ and leucocyte common antigen related phosphatase, and neogenin, respectively. Once activated, these receptors initiate downstream signaling pathways, the most common amongst them being the RhoA/ROCK signaling pathway. These signaling cascades result in actin depolymerization, neurite outgrowth inhibition, and failure to regenerate after spinal cord injury. Currently, there are no approved pharmacological treatments to overcome spinal cord injuries other than physical rehabilitation and management of the array of symptoms brought on by spinal cord injuries. However, several novel therapies aiming to modulate these inhibitory proteins and/or their receptors are under investigation in ongoing clinical trials. Investigation has also been demonstrating that combinatorial therapies of growth inhibitors with other therapies, such as growth factors or stem-cell therapies, produce stronger results and their potential application in the clinics opens new venues in spinal cord injury treatment.
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Affiliation(s)
- Sílvia Sousa Chambel
- Experimental Biology Unit, Department of Biomedicine, Faculty of Medicine of Porto; Translational NeuroUrology, Instituto de Investigação e Inovação em Saúde-i3S and IBMC, Universidade do Porto, Porto, Portugal
| | - Célia Duarte Cruz
- Experimental Biology Unit, Department of Biomedicine, Faculty of Medicine of Porto; Translational NeuroUrology, Instituto de Investigação e Inovação em Saúde-i3S and IBMC, Universidade do Porto, Porto, Portugal
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Davis-Lunn M, Goult BT, Andrews MR. Clutching at Guidance Cues: The Integrin-FAK Axis Steers Axon Outgrowth. BIOLOGY 2023; 12:954. [PMID: 37508384 PMCID: PMC10376711 DOI: 10.3390/biology12070954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 06/27/2023] [Accepted: 06/30/2023] [Indexed: 07/30/2023]
Abstract
Integrin receptors are essential contributors to neurite outgrowth and axon elongation. Activated integrins engage components of the extracellular matrix, enabling the growth cone to form point contacts, which connect the extracellular substrate to dynamic intracellular protein complexes. These adhesion complexes facilitate efficient growth cone migration and neurite extension. Major signalling pathways mediated by the adhesion complex are instigated by focal adhesion kinase (FAK), whilst axonal guidance molecules present in vivo promote growth cone turning or retraction by local modulation of FAK activity. Activation of FAK is marked by phosphorylation following integrin engagement, and this activity is tightly regulated during neurite outgrowth. FAK inhibition slows neurite outgrowth by reducing point contact turnover; however, mutant FAK constructs with enhanced activity stimulate aberrant outgrowth. Importantly, FAK is a major structural component of maturing adhesion sites, which provide the platform for actin polymerisation to drive leading edge advance. In this review, we discuss the coordinated signalling of integrin receptors and FAK, as well as their role in regulating neurite outgrowth and axon elongation. We also discuss the importance of the integrin-FAK axis in vivo, as integrin expression and activation are key determinants of successful axon regeneration following injury.
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Affiliation(s)
- Mathew Davis-Lunn
- Faculty of Environmental and Life Sciences, University of Southampton, Southampton SO17 1BJ, UK
| | - Benjamin T Goult
- School of Biosciences, University of Kent, Canterbury CT2 7NJ, UK
| | - Melissa R Andrews
- Faculty of Environmental and Life Sciences, University of Southampton, Southampton SO17 1BJ, UK
- Centre for Human Development, Stem Cells and Regeneration, School of Biological Sciences, University of Southampton, Southampton SO17 1BJ, UK
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Siddiqui SS. Non-canonical roles of Siglecs: Beyond sialic acid-binding and immune cell modulation. Mol Aspects Med 2023; 90:101145. [PMID: 36153172 DOI: 10.1016/j.mam.2022.101145] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 08/11/2022] [Accepted: 09/13/2022] [Indexed: 02/08/2023]
Abstract
Siglecs (Sialic acid-binding immunoglobulin-type lectins) are I-type lectins that bind with sialic acid ligands (Sia). Most are expressed on the surface of leukocytes and are involved in immune regulation and possess immune tyrosine-based inhibitory motif (ITIM) in the intracellular domain, thus leading to inhibition of the immune response. This signaling is instrumental in maintaining quiescence under physiological conditions and acts as a brake for inflammatory cascades. By contrast, activating Siglecs carry positively charged residues in the transmembrane domain and interact with immune tyrosine-based activating motif (ITAM)-containing proteins, a DNAX-activating protein of 10-12 kDa (DAP10/12), to activate immune cells. There are various characteristics of Siglecs that do not fit within the classification of Siglec receptors as being either inhibitory or activating in nature. This review focuses on elucidating the non-canonical functions and interactions of Siglec receptors, which include Sia-independent interactions such as protein-protein interactions and interactions with lipids or other sugars. This review also summarizes Siglec expression and function on non-immune cells, and non-classical signaling of the receptor. Thus, this review will be beneficial to researchers interested in the field of Siglecs and sialic acid biology.
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Affiliation(s)
- Shoib Sarwar Siddiqui
- School of Life and Medical Sciences, University of Hertfordshire, College Lane Campus, Hatfield, AL10 9AB, United Kingdom.
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Chen L, Yu Z, Xie L, He X, Mu X, Chen C, Yang W, Tong X, Liu J, Gao Z, Sun S, Xu N, Lu Z, Zheng J, Zhang Y. ANGPTL2 binds MAG to efficiently enhance oligodendrocyte differentiation. Cell Biosci 2023; 13:42. [PMID: 36855057 PMCID: PMC9976406 DOI: 10.1186/s13578-023-00970-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Accepted: 01/23/2023] [Indexed: 03/02/2023] Open
Abstract
BACKGROUND Oligodendrocytes have robust regenerative ability and are key players in remyelination during physiological and pathophysiological states. However, the mechanisms of brain microenvironmental cue in regulation of the differentiation of oligodendrocytes still needs to be further investigated. RESULTS We demonstrated that myelin-associated glycoprotein (MAG) was a novel receptor for angiopoietin-like protein 2 (ANGPTL2). The binding of ANGPTL2 to MAG efficiently promoted the differentiation of oligodendrocytes in vitro, as evaluated in an HCN cell line. Angptl2-null mice had a markedly impaired myelination capacity in the early stage of oligodendrocyte development. These mice had notably decreased remyelination capacities and enhanced motor disability in a cuprizone-induced demyelinating mouse model, which was similar to the Mag-null mice. The loss of remyelination ability in Angptl2-null/Mag-null mice was similar to the Angptl2-WT/Mag-null mice, which indicated that the ANGPTL2-mediated oligodendrocyte differentiation effect depended on the MAG receptor. ANGPTL2 bound MAG to enhance its phosphorylation level and recruit Fyn kinase, which increased Fyn phosphorylation levels, followed by the transactivation of myelin regulatory factor (MYRF). CONCLUSION Our study demonstrated an unexpected cross-talk between the environmental protein (ANGPTL2) and its surface receptor (MAG) in the regulation of oligodendrocyte differentiation, which may benefit the treatment of many demyelination disorders, including multiple sclerosis.
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Affiliation(s)
- Lu Chen
- Hongqiao International Institute of Medicine, Shanghai Tongren Hospital/Faculty of Basic Medicine, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, 280 South Chongqing Road, Shanghai, 200025, China
| | - Zhuo Yu
- Hongqiao International Institute of Medicine, Shanghai Tongren Hospital/Faculty of Basic Medicine, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, 280 South Chongqing Road, Shanghai, 200025, China
| | - Li Xie
- Hongqiao International Institute of Medicine, Shanghai Tongren Hospital/Faculty of Basic Medicine, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, 280 South Chongqing Road, Shanghai, 200025, China
| | - Xiaoxiao He
- Hongqiao International Institute of Medicine, Shanghai Tongren Hospital/Faculty of Basic Medicine, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, 280 South Chongqing Road, Shanghai, 200025, China
| | - Xingmei Mu
- Hongqiao International Institute of Medicine, Shanghai Tongren Hospital/Faculty of Basic Medicine, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, 280 South Chongqing Road, Shanghai, 200025, China
| | - Chiqi Chen
- Hongqiao International Institute of Medicine, Shanghai Tongren Hospital/Faculty of Basic Medicine, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, 280 South Chongqing Road, Shanghai, 200025, China
| | - Wenqian Yang
- Hongqiao International Institute of Medicine, Shanghai Tongren Hospital/Faculty of Basic Medicine, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, 280 South Chongqing Road, Shanghai, 200025, China
| | - Xiaoping Tong
- Center for Brain Science, Shanghai Children's Medical Center, Department of Anatomy and Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Junling Liu
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory of Tumor Microenvironment and Inflammation, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Zhengliang Gao
- Yangzhi Rehabilitation Hospital (Shanghai Sunshine Rehabilitation Center), Tongji Univeirsity School of Medicine, Shanghai, China
| | - Suya Sun
- Department of Neurology and Institute of Neurology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - NanJie Xu
- Collaborative Innovation Center for Brain Science, Department of Anatomy and Physiology, Key Laboratory of Cell Differentiation and Apoptosis of the Chinese Ministry of Education, Shanghai Key Laboratory of Reproductive Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Zhigang Lu
- The Fifth People's Hospital of Shanghai, the Shanghai Key Laboratory of Medical Epigenetics, The International Co-Laboratory of Medical Epigenetics and Metabolism, Ministry of Science and Technology, Institutes of Biomedical Sciences, Shanghai Institute of Infectious Diseases and Biosecurity, Shanghai Medical College, Fudan University, Shanghai, China.
| | - Junke Zheng
- Hongqiao International Institute of Medicine, Shanghai Tongren Hospital/Faculty of Basic Medicine, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, 280 South Chongqing Road, Shanghai, 200025, China.
| | - Yaping Zhang
- Hongqiao International Institute of Medicine, Shanghai Tongren Hospital/Faculty of Basic Medicine, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, 280 South Chongqing Road, Shanghai, 200025, China.
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Kingston R, Amin D, Misra S, Gross JM, Kuwajima T. Serotonin transporter-mediated molecular axis regulates regional retinal ganglion cell vulnerability and axon regeneration after nerve injury. PLoS Genet 2021; 17:e1009885. [PMID: 34735454 PMCID: PMC8594818 DOI: 10.1371/journal.pgen.1009885] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 11/16/2021] [Accepted: 10/17/2021] [Indexed: 11/19/2022] Open
Abstract
Molecular insights into the selective vulnerability of retinal ganglion cells (RGCs) in optic neuropathies and after ocular trauma can lead to the development of novel therapeutic strategies aimed at preserving RGCs. However, little is known about what molecular contexts determine RGC susceptibility. In this study, we show the molecular mechanisms underlying the regional differential vulnerability of RGCs after optic nerve injury. We identified RGCs in the mouse peripheral ventrotemporal (VT) retina as the earliest population of RGCs susceptible to optic nerve injury. Mechanistically, the serotonin transporter (SERT) is upregulated on VT axons after injury. Utilizing SERT-deficient mice, loss of SERT attenuated VT RGC death and led to robust retinal axon regeneration. Integrin β3, a factor mediating SERT-induced functions in other systems, is also upregulated in RGCs and axons after injury, and loss of integrin β3 led to VT RGC protection and axon regeneration. Finally, RNA sequencing analyses revealed that loss of SERT significantly altered molecular signatures in the VT retina after optic nerve injury, including expression of the transmembrane protein, Gpnmb. GPNMB is rapidly downregulated in wild-type, but not SERT- or integrin β3-deficient VT RGCs after injury, and maintaining expression of GPNMB in RGCs via AAV2 viruses even after injury promoted VT RGC survival and axon regeneration. Taken together, our findings demonstrate that the SERT-integrin β3-GPNMB molecular axis mediates selective RGC vulnerability and axon regeneration after optic nerve injury.
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Affiliation(s)
- Rody Kingston
- Department of Ophthalmology, The Louis J. Fox Center for Vision Restoration, Pittsburgh, Pennsylvania, United States of America
| | - Dwarkesh Amin
- Department of Ophthalmology, The Louis J. Fox Center for Vision Restoration, Pittsburgh, Pennsylvania, United States of America
| | - Sneha Misra
- Department of Ophthalmology, The Louis J. Fox Center for Vision Restoration, Pittsburgh, Pennsylvania, United States of America
| | - Jeffrey M. Gross
- Department of Ophthalmology, The Louis J. Fox Center for Vision Restoration, Pittsburgh, Pennsylvania, United States of America
- Department of Developmental Biology, The McGowan Institute for Regenerative Medicine, The University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Takaaki Kuwajima
- Department of Ophthalmology, The Louis J. Fox Center for Vision Restoration, Pittsburgh, Pennsylvania, United States of America
- * E-mail:
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Ko E, Poon MLS, Park E, Cho Y, Shin JH. Engineering 3D Cortical Spheroids for an In Vitro Ischemic Stroke Model. ACS Biomater Sci Eng 2021; 7:3845-3860. [PMID: 34275269 DOI: 10.1021/acsbiomaterials.1c00406] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Three-dimensional (3D) spheroids composed of brain cells have shown great potential to mimic the pathophysiology of the brain. However, a 3D spheroidal brain-disease model for cerebral ischemia has not been reported. This study investigated an ultralow attachment (ULA) surface-mediated formation of 3D cortical spheroids using primary rat cortical cells to recapitulate the cerebral ischemic responses in stroke by oxygen-glucose deprivation-reoxygenation (OGD-R) treatment. Comparison between two-dimensional (2D) and 3D cell culture models confirmed the better performance of the 3D cortical spheroids as normal brain models. The cortical cells cultured in 3D maintained their healthy physiological morphology of a less activated state and suppressed mRNA expressions of pathological stroke markers, S100B, IL-1β, and MBP, selected based on in vivo stroke model. Interestingly, the spheroids formed on the ULA surface exhibited striking aggregation dynamics involving active cell-substrate interactions, whereas those formed on the agarose surface aggregated passively by the convective flow of the media. Accordingly, ULA spheroids manifested a layered arrangement of neurons and astrocytes with higher expressions of integrin β1, integrin α5, N-cadherin, and fibronectin than the agarose spheroids. OGD-R-induced stroke model of the ULA spheroids successfully mimicked the ischemic response as evidenced by the upregulated mRNA expressions of the key markers for stroke, S100B, IL-1β, and MBP. Our study suggested that structurally and functionally distinct cortical spheroids could be generated by simply tuning the cell-substrate binding activities during dynamic spheroidal formation, which should be an essential factor to consider in establishing a brain-disease model.
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Affiliation(s)
- Eunmin Ko
- Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, 291, Daehak-ro, Daejeon 34141, Republic of Korea
| | - Mong Lung Steve Poon
- Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, 291, Daehak-ro, Daejeon 34141, Republic of Korea
| | - Eunyoung Park
- Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, 291, Daehak-ro, Daejeon 34141, Republic of Korea
| | - Youngbin Cho
- Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, 291, Daehak-ro, Daejeon 34141, Republic of Korea
| | - Jennifer H Shin
- Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, 291, Daehak-ro, Daejeon 34141, Republic of Korea
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One Raft to Guide Them All, and in Axon Regeneration Inhibit Them. Int J Mol Sci 2021; 22:ijms22095009. [PMID: 34066896 PMCID: PMC8125918 DOI: 10.3390/ijms22095009] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 04/30/2021] [Accepted: 05/05/2021] [Indexed: 12/15/2022] Open
Abstract
Central nervous system damage caused by traumatic injuries, iatrogenicity due to surgical interventions, stroke and neurodegenerative diseases is one of the most prevalent reasons for physical disability worldwide. During development, axons must elongate from the neuronal cell body to contact their precise target cell and establish functional connections. However, the capacity of the adult nervous system to restore its functionality after injury is limited. Given the inefficacy of the nervous system to heal and regenerate after damage, new therapies are under investigation to enhance axonal regeneration. Axon guidance cues and receptors, as well as the molecular machinery activated after nervous system damage, are organized into lipid raft microdomains, a term typically used to describe nanoscale membrane domains enriched in cholesterol and glycosphingolipids that act as signaling platforms for certain transmembrane proteins. Here, we systematically review the most recent findings that link the stability of lipid rafts and their composition with the capacity of axons to regenerate and rebuild functional neural circuits after damage.
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8
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Fernández-Suárez D, Krapacher FA, Andersson A, Ibáñez CF, Kisiswa L. MAG induces apoptosis in cerebellar granule neurons through p75 NTR demarcating granule layer/white matter boundary. Cell Death Dis 2019; 10:732. [PMID: 31570696 PMCID: PMC6768859 DOI: 10.1038/s41419-019-1970-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2019] [Revised: 08/01/2019] [Accepted: 09/09/2019] [Indexed: 01/01/2023]
Abstract
MAG (Myelin-associated glycoprotein) is a type I transmembrane glycoprotein expressed by Schwann cells and oligodendrocytes, that has been implicated in the control of axonal growth in many neuronal populations including cerebellar granule neurons (CGNs). However, it is unclear whether MAG has other functions in central nervous system, in particular, in cerebellar development and patterning. We find that MAG expression in the cerebellum is compartmentalised resulting in increased MAG protein levels in the cerebellar white matter. MAG induces apoptosis in developing CGNs through p75NTR signalling. Deletion of p75NTR in vivo reduced the number of apoptotic neurons in cerebellar white matter during development leading to reduction in the size of white matter in the adulthood. Furthermore, we show that MAG impairs CGNs neurite outgrowth as consequence of MAG-induced apoptosis in CGNs. Mechanistically, we find that MAG/NgR1-induced cell death is dependent of p75NTR-mediated activation of JNK/cell death signalling pathway. Together, these findings identify the mechanisms by which MAG induces CGNs apoptotic activity, a crucial event that facilitates cerebellar layer refinement during development.
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Affiliation(s)
| | - Favio A Krapacher
- Department of Neuroscience, Karolinska Institute, S-17177, Stockholm, Sweden
| | - Annika Andersson
- Department of Neuroscience, Karolinska Institute, S-17177, Stockholm, Sweden
| | - Carlos F Ibáñez
- Department of Neuroscience, Karolinska Institute, S-17177, Stockholm, Sweden.,Department of Physiology, National University of Singapore, Singapore, 117597, Singapore.,Life Sciences Institute, National University of Singapore, Singapore, 117456, Singapore
| | - Lilian Kisiswa
- Department of Physiology, National University of Singapore, Singapore, 117597, Singapore.
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9
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Hor CHH, Goh ELK. Rab23 Regulates Radial Migration of Projection Neurons via N-cadherin. Cereb Cortex 2019; 28:1516-1531. [PMID: 29420702 PMCID: PMC6093454 DOI: 10.1093/cercor/bhy018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Indexed: 01/12/2023] Open
Abstract
Radial migration of cortical projection neurons is a prerequisite for shaping a distinct multilayered cerebral cortex during mammalian corticogenesis. Members of Rab GTPases family were reported to regulate radial migration. Here, in vivo conditional knockout or in utero knockdown (KD) of Rab23 in mice neocortex causes aberrant polarity and halted migration of cortical projection neurons. Further investigation of the underlying mechanism reveals down-regulation of N-cadherin in the Rab23-deficient neurons, which is a cell adhesion protein previously known to modulate radial migration. (Shikanai M, Nakajima K, Kawauchi T. 2011. N-cadherin regulates radial glial fiber-dependent migration of cortical locomoting neurons. Commun Integr Biol. 4:326–330.) Interestingly, pharmacological inhibition of extracellular signal-regulated kinases (ERK1/2) also decreases the expression of N-cadherin, implicating an upstream effect of ERK1/2 on N-cadherin and also suggesting a link between Rab23 and ERK1/2. Further biochemical studies show that silencing of Rab23 impedes activation of ERK1/2 via perturbed platelet-derived growth factor-alpha (PDGFRα) signaling. Restoration of the expression of Rab23 or N-cadherin in Rab23-KD neurons could reverse neuron migration defects, indicating that Rab23 modulates migration through N-cadherin. These studies suggest that cortical neuron migration is mediated by a molecular hierarchy downstream of Rab23 via N-cadherin.
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Affiliation(s)
- Catherine H H Hor
- Neuroscience Academic Clinical Programme, Duke-NUS Medical School, Singapore 169857, Singapore.,Department of Research, National Neuroscience Institute, Singapore 308433, Singapore
| | - Eyleen L K Goh
- Neuroscience Academic Clinical Programme, Duke-NUS Medical School, Singapore 169857, Singapore.,Department of Research, National Neuroscience Institute, Singapore 308433, Singapore.,Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, 8 Medical Drive, Singapore 117597, Singapore.,KK Research Center, KK Women's and Children's Hospital, Singapore 229899, Singapore
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10
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Autocrine Mfge8 Signaling Prevents Developmental Exhaustion of the Adult Neural Stem Cell Pool. Cell Stem Cell 2018; 23:444-452.e4. [PMID: 30174295 DOI: 10.1016/j.stem.2018.08.005] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2017] [Revised: 06/01/2018] [Accepted: 08/06/2018] [Indexed: 12/21/2022]
Abstract
Adult neurogenesis, arising from quiescent radial-glia-like neural stem cells (RGLs), occurs throughout life in the dentate gyrus. How neural stem cells are maintained throughout development to sustain adult mammalian neurogenesis is not well understood. Here, we show that milk fat globule-epidermal growth factor (EGF) 8 (Mfge8), a known phagocytosis factor, is highly enriched in quiescent RGLs in the dentate gyrus. Mfge8-null mice exhibit decreased adult dentate neurogenesis, and furthermore, adult RGL-specific deletion of Mfge8 leads to RGL overactivation and depletion. Similarly, loss of Mfge8 promotes RGL activation in the early postnatal dentate gyrus, resulting in a decreased number of label-retaining RGLs in adulthood. Mechanistically, loss of Mfge8 elevates mTOR1 signaling in RGLs, inhibition of which by rapamycin returns RGLs to quiescence. Together, our study identifies a neural-stem-cell-enriched niche factor that maintains quiescence and prevents developmental exhaustion of neural stem cells to sustain continuous neurogenesis in the adult mammalian brain.
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11
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Nieuwenhuis B, Haenzi B, Andrews MR, Verhaagen J, Fawcett JW. Integrins promote axonal regeneration after injury of the nervous system. Biol Rev Camb Philos Soc 2018; 93:1339-1362. [PMID: 29446228 PMCID: PMC6055631 DOI: 10.1111/brv.12398] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Revised: 12/23/2017] [Accepted: 01/11/2018] [Indexed: 12/13/2022]
Abstract
Integrins are cell surface receptors that form the link between extracellular matrix molecules of the cell environment and internal cell signalling and the cytoskeleton. They are involved in several processes, e.g. adhesion and migration during development and repair. This review focuses on the role of integrins in axonal regeneration. Integrins participate in spontaneous axonal regeneration in the peripheral nervous system through binding to various ligands that either inhibit or enhance their activation and signalling. Integrin biology is more complex in the central nervous system. Integrins receptors are transported into growing axons during development, but selective polarised transport of integrins limits the regenerative response in adult neurons. Manipulation of integrins and related molecules to control their activation state and localisation within axons is a promising route towards stimulating effective regeneration in the central nervous system.
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Affiliation(s)
- Bart Nieuwenhuis
- John van Geest Centre for Brain Repair, Department of Clinical NeurosciencesUniversity of CambridgeCambridgeCB2 0PYU.K.
- Laboratory for Regeneration of Sensorimotor SystemsNetherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences (KNAW)1105 BAAmsterdamThe Netherlands
| | - Barbara Haenzi
- John van Geest Centre for Brain Repair, Department of Clinical NeurosciencesUniversity of CambridgeCambridgeCB2 0PYU.K.
| | | | - Joost Verhaagen
- Laboratory for Regeneration of Sensorimotor SystemsNetherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences (KNAW)1105 BAAmsterdamThe Netherlands
- Centre for Neurogenomics and Cognitive Research, Amsterdam NeuroscienceVrije Universiteit Amsterdam1081 HVAmsterdamThe Netherlands
| | - James W. Fawcett
- John van Geest Centre for Brain Repair, Department of Clinical NeurosciencesUniversity of CambridgeCambridgeCB2 0PYU.K.
- Centre of Reconstructive NeuroscienceInstitute of Experimental Medicine142 20Prague 4Czech Republic
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12
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Al-Bashir N, Mellado W, Filbin MT. Sialic Acid Is Required for Neuronal Inhibition by Soluble MAG but not for Membrane Bound MAG. Front Mol Neurosci 2016; 9:21. [PMID: 27065798 PMCID: PMC4817280 DOI: 10.3389/fnmol.2016.00021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2015] [Accepted: 03/14/2016] [Indexed: 11/13/2022] Open
Abstract
Myelin-Associated Glycoprotein (MAG), a major inhibitor of axonal growth, is a member of the immunoglobulin (Ig) super-family. Importantly, MAG (also known as Siglec-4) is a member of the Siglec family of proteins (sialic acid-binding, immunoglobulin-like lectins), MAG binds to complex gangliosides, specifically GD1a and/or GT1b. Therefore, it has been proposed as neuronal receptors for MAG inhibitory effect of axonal growth. Previously, we showed that MAG binds sialic acid through domain 1 at Arg118 and is able to inhibit axonal growth through domain 5. We developed a neurite outgrowth (NOG) assay, in which both wild type MAG and mutated MAG (MAG Arg118) are expressed on cells. In addition we also developed a soluble form NOG in which we utilized soluble MAG-Fc and mutated MAG (Arg118-Fc). Only MAG-Fc is able to inhibit NOG, but not mutated MAG (Arg118)-Fc that has been mutated at its sialic acid binding site. However, both forms of membrane bound MAG- and MAG (Arg118)- expressing cells still inhibit NOG. Here, we review various results from different groups regarding MAG’s inhibition of axonal growth. Also, we propose a model in which the sialic acid binding is not necessary for the inhibition induced by the membrane form of MAG, but it is necessary for the soluble form of MAG. This finding highlights the importance of understanding the different mechanisms by which MAG inhibits NOG in both the soluble fragmented form and the membrane-bound form in myelin debris following CNS damage.
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Affiliation(s)
- Najat Al-Bashir
- Biology Department, Hunter College, City University of New York New York, NY, USA
| | - Wilfredo Mellado
- Biology Department, Hunter College, City University of New YorkNew York, NY, USA; Burke-Cornell Medical Research Institute White Plains, NY, USA
| | - Marie T Filbin
- Biology Department, Hunter College, City University of New York New York, NY, USA
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Lim YS, Tang BL. A role for Rab23 in the trafficking of Kif17 to the primary cilium. J Cell Sci 2015; 128:2996-3008. [PMID: 26136363 DOI: 10.1242/jcs.163964] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Accepted: 06/25/2015] [Indexed: 01/07/2023] Open
Abstract
The small GTPase Rab23 is an antagonist of sonic hedgehog (Shh) signaling during mouse development. Given that modulation of Shh signaling depends on the normal functioning of the primary cilium, and overexpression of Evi5L, a putative Rab23 GTPase-activating protein (GAP), leads to reduced ciliogenesis, Rab23 could have a role at the primary cilium. Here, we found that wild-type Rab23 and the constitutively active Rab23 Q68L mutant were enriched at the primary cilium. Therefore, we tested the role of Rab23 in the ciliary targeting of known cargoes and found that ciliary localization of the kinesin-2 motor protein Kif17 was disrupted in Rab23-depleted cells. Co-immunoprecipitation and affinity-binding studies revealed that Rab23 exists in a complex with Kif17 and importin β2 (the putative Kif17 ciliary import carrier), implying that Kif17 needs to bind to regulatory proteins like Rab23 for its ciliary transport. Although a ciliary-cytoplasmic gradient of nuclear Ran is necessary to regulate the ciliary transport of Kif17, Rab23 and Ran appear to have differing roles in regulating the ciliary entry of Kif17. Our findings have uncovered a hitherto unknown effector of Rab23 and demonstrate how Rab23 could mediate the transport of Kif17 to the primary cilium.
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Affiliation(s)
- Yi Shan Lim
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University Health System, 8 Medical Drive, 117597 Singapore
| | - Bor Luen Tang
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University Health System, 8 Medical Drive, 117597 Singapore National University of Singapore Graduate School of Integrative Sciences and Engineering, National University of Singapore, 28 Medical Drive, 117456 Singapore
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14
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Suenaga T, Matsumoto M, Arisawa F, Kohyama M, Hirayasu K, Mori Y, Arase H. Sialic Acids on Varicella-Zoster Virus Glycoprotein B Are Required for Cell-Cell Fusion. J Biol Chem 2015; 290:19833-43. [PMID: 26105052 DOI: 10.1074/jbc.m114.635508] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Indexed: 12/28/2022] Open
Abstract
Varicella-zoster virus (VZV) is a member of the human Herpesvirus family that causes varicella (chicken pox) and zoster (shingles). VZV latently infects sensory ganglia and is also responsible for encephalomyelitis. Myelin-associated glycoprotein (MAG), a member of the sialic acid (SA)-binding immunoglobulin-like lectin family, is mainly expressed in neural tissues. VZV glycoprotein B (gB) associates with MAG and mediates membrane fusion during VZV entry into host cells. The SA requirements of MAG when associating with its ligands vary depending on the specific ligand, but it is unclear whether the SAs on gB are involved in the association with MAG. In this study, we found that SAs on gB are essential for the association with MAG as well as for membrane fusion during VZV infection. MAG with a point mutation in the SA-binding site did not bind to gB and did not mediate cell-cell fusion or VZV entry. Cell-cell fusion and VZV entry mediated by the gB-MAG interaction were blocked by sialidase treatment. N-glycosylation or O-glycosylation inhibitors also inhibited the fusion and entry mediated by gB-MAG interaction. Furthermore, gB with mutations in N-glycosylation sites, i.e. asparagine residues 557 and 686, did not associate with MAG, and the cell-cell fusion efficiency was low. Fusion between the viral envelope and cellular membrane is essential for host cell entry by herpesviruses. Therefore, these results suggest that SAs on gB play important roles in MAG-mediated VZV infection.
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Affiliation(s)
- Tadahiro Suenaga
- From the Department of Immunochemistry, Research Institute for Microbial Diseases and Laboratory of Immunochemistry, WPI Immunology Frontier Research Center, Osaka University, Suita, Osaka 565-0871, Japan, and
| | - Maki Matsumoto
- From the Department of Immunochemistry, Research Institute for Microbial Diseases and Laboratory of Immunochemistry, WPI Immunology Frontier Research Center, Osaka University, Suita, Osaka 565-0871, Japan, and
| | - Fuminori Arisawa
- From the Department of Immunochemistry, Research Institute for Microbial Diseases and
| | - Masako Kohyama
- From the Department of Immunochemistry, Research Institute for Microbial Diseases and Laboratory of Immunochemistry, WPI Immunology Frontier Research Center, Osaka University, Suita, Osaka 565-0871, Japan, and
| | - Kouyuki Hirayasu
- From the Department of Immunochemistry, Research Institute for Microbial Diseases and Laboratory of Immunochemistry, WPI Immunology Frontier Research Center, Osaka University, Suita, Osaka 565-0871, Japan, and
| | - Yasuko Mori
- the Division of Clinical Virology, Center for Infectious Diseases, Kobe University Graduate School of Medicine, Kobe, Hyogo, 650-0017, Japan
| | - Hisashi Arase
- From the Department of Immunochemistry, Research Institute for Microbial Diseases and Laboratory of Immunochemistry, WPI Immunology Frontier Research Center, Osaka University, Suita, Osaka 565-0871, Japan, and
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15
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Baldwin KT, Giger RJ. Insights into the physiological role of CNS regeneration inhibitors. Front Mol Neurosci 2015; 8:23. [PMID: 26113809 PMCID: PMC4462676 DOI: 10.3389/fnmol.2015.00023] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Accepted: 05/26/2015] [Indexed: 12/14/2022] Open
Abstract
The growth inhibitory nature of injured adult mammalian central nervous system (CNS) tissue constitutes a major barrier to robust axonal outgrowth and functional recovery following trauma or disease. Prototypic CNS regeneration inhibitors are broadly expressed in the healthy and injured brain and spinal cord and include myelin-associated glycoprotein (MAG), the reticulon family member NogoA, oligodendrocyte myelin glycoprotein (OMgp), and chondroitin sulfate proteoglycans (CSPGs). These structurally diverse molecules strongly inhibit neurite outgrowth in vitro, and have been most extensively studied in the context of nervous system injury in vivo. The physiological role of CNS regeneration inhibitors in the naïve, or uninjured, CNS remains less well understood, but has received growing attention in recent years and is the focus of this review. CNS regeneration inhibitors regulate myelin development and axon stability, consolidate neuronal structure shaped by experience, and limit activity-dependent modification of synaptic strength. Altered function of CNS regeneration inhibitors is associated with neuropsychiatric disorders, suggesting crucial roles in brain development and health.
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Affiliation(s)
- Katherine T Baldwin
- Department of Cell and Developmental Biology, University of Michigan School of Medicine Ann Arbor, MI, USA ; Cellular and Molecular Biology Graduate Program, University of Michigan School of Medicine Ann Arbor, MI, USA
| | - Roman J Giger
- Department of Cell and Developmental Biology, University of Michigan School of Medicine Ann Arbor, MI, USA ; Department of Neurology, University of Michigan School of Medicine Ann Arbor, MI, USA
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16
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Ma D, Yoon SI, Yang CH, Marcy G, Zhao N, Leong WY, Ganapathy V, Han J, Van Dongen AMJ, Hsu KS, Ming GL, Augustine GJ, Goh ELK. Rescue of Methyl-CpG Binding Protein 2 Dysfunction-induced Defects in Newborn Neurons by Pentobarbital. Neurotherapeutics 2015; 12:477-90. [PMID: 25753729 PMCID: PMC4404443 DOI: 10.1007/s13311-015-0343-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Rett syndrome is a neurodevelopmental disorder that usually arises from mutations or deletions in methyl-CpG binding protein 2 (MeCP2), a transcriptional regulator that affects neuronal development and maturation without causing cell loss. Here, we show that silencing of MeCP2 decreased neurite arborization and synaptogenesis in cultured hippocampal neurons from rat fetal brains. These structural defects were associated with alterations in synaptic transmission and neural network activity. Similar retardation of dendritic growth was also observed in MeCP2-deficient newborn granule cells in the dentate gyrus of adult mouse brains in vivo, demonstrating direct and cell-autonomous effects on individual neurons. These defects, caused by MeCP2 deficiency, were reversed by treatment with the US Food and Drug Administration-approved drug, pentobarbital, in vitro and in vivo, possibly caused by modulation of γ-aminobutyric acid signaling. The results indicate that drugs modulating γ-aminobutyric acid signaling are potential therapeutics for Rett syndrome.
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Affiliation(s)
- Dongliang Ma
- Programme in Neuroscience and Behavioral Disorders, Duke-NUS Graduate Medical School, Singapore, Singapore
| | - Su-In Yoon
- Programme in Neuroscience and Behavioral Disorders, Duke-NUS Graduate Medical School, Singapore, Singapore
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Chih-Hao Yang
- Department of Pharmacology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Guillaume Marcy
- Programme in Neuroscience and Behavioral Disorders, Duke-NUS Graduate Medical School, Singapore, Singapore
| | - Na Zhao
- Programme in Neuroscience and Behavioral Disorders, Duke-NUS Graduate Medical School, Singapore, Singapore
- Department of Forensic Medicine, Key Laboratory of Health Ministry for Forensic Science, Xi’an Jiaotong University School of Medicine, Xi’an, Shaanxi People’s Republic of China
| | - Wan-Ying Leong
- Programme in Neuroscience and Behavioral Disorders, Duke-NUS Graduate Medical School, Singapore, Singapore
| | - Vinu Ganapathy
- Programme in Neuroscience and Behavioral Disorders, Duke-NUS Graduate Medical School, Singapore, Singapore
| | - Ju Han
- Programme in Neuroscience and Behavioral Disorders, Duke-NUS Graduate Medical School, Singapore, Singapore
| | - Antonius M. J. Van Dongen
- Programme in Neuroscience and Behavioral Disorders, Duke-NUS Graduate Medical School, Singapore, Singapore
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Kuei-Sen Hsu
- Department of Pharmacology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Guo-Li Ming
- Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD USA
| | - George J. Augustine
- Programme in Neuroscience and Behavioral Disorders, Duke-NUS Graduate Medical School, Singapore, Singapore
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
- Center for Functional Connectomics, Korea Institute of Science and Technology, Seoul, Republic of Korea
- Institute of Molecular and Cell Biology, A*STAR, Proteos, Singapore, Singapore
| | - Eyleen L. K. Goh
- Programme in Neuroscience and Behavioral Disorders, Duke-NUS Graduate Medical School, Singapore, Singapore
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
- KK Research Center, KK Women’s and Children’s Hospital, Singapore, Singapore
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17
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Gundimeda U, McNeill TH, Barseghian BA, Tzeng WS, Rayudu DV, Cadenas E, Gopalakrishna R. Polyphenols from green tea prevent antineuritogenic action of Nogo-A via 67-kDa laminin receptor and hydrogen peroxide. J Neurochem 2015; 132:70-84. [PMID: 25314656 DOI: 10.1111/jnc.12964] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Revised: 08/22/2014] [Accepted: 10/06/2014] [Indexed: 02/02/2023]
Abstract
Axonal regeneration after injury to the CNS is hampered by myelin-derived inhibitors, such as Nogo-A. Natural products, such as green tea, which are neuroprotective and safe for long-term therapy, would complement ongoing various pharmacological approaches. In this study, using nerve growth factor-differentiated neuronal-like Neuroscreen-1 cells, we show that extremely low concentrations of unfractionated green tea polyphenol mixture (GTPP) and its active ingredient, epigallocatechin-3-gallate (EGCG), prevent both the neurite outgrowth-inhibiting activity and growth cone-collapsing activity of Nogo-66 (C-terminal domain of Nogo-A). Furthermore, a synergistic interaction was observed among GTPP constituents. This preventive effect was dependent on 67-kDa laminin receptor (67LR) to which EGCG binds with high affinity. The antioxidants N-acetylcysteine and cell-permeable catalase abolished this preventive effect of GTPP and EGCG, suggesting the involvement of sublethal levels of H2 O2 in this process. Accordingly, exogenous sublethal concentrations of H2 O2 , added as a bolus dose (5 μM) or more effectively through a steady-state generation (1-2 μM), mimicked GTPP in counteracting the action of Nogo-66. Exogenous H2 O2 mediated this action by bypassing the requirement of 67LR. Taken together, these results show for the first time that GTPP and EGCG, acting through 67LR and elevating intracellular sublethal levels of H2 O2 , inhibit the antineuritogenic action of Nogo-A. Currently, several agents are being evaluated for overcoming axonal growth inhibitors to promote functional recovery after stroke and spinal cord injury. Epigallocatechin-3-gallate (EGCG), present in green tea polyphenol mixture (GTPP), prevents antineuritogenic activity of Nogo-A, a myelin-derived axonal growth inhibitor. The preventive action of EGCG involves the cell-surface-associated 67-kDa laminin receptor and H2 O2 . GTPP may complement ongoing efforts to treat neuronal injuries.>
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Affiliation(s)
- Usha Gundimeda
- Department of Cell and Neurobiology, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
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18
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Focal adhesion kinase function in neuronal development. Curr Opin Neurobiol 2014; 27:89-95. [DOI: 10.1016/j.conb.2014.03.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Revised: 02/17/2014] [Accepted: 03/09/2014] [Indexed: 11/21/2022]
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19
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Myelin-associated inhibitors in axonal growth after CNS injury. Curr Opin Neurobiol 2014; 27:31-8. [PMID: 24608164 DOI: 10.1016/j.conb.2014.02.012] [Citation(s) in RCA: 135] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2013] [Revised: 01/22/2014] [Accepted: 02/10/2014] [Indexed: 11/20/2022]
Abstract
There are multiple barriers to axonal growth after CNS injury. Myelin-associated inhibitors represent one group of barriers extrinsic to the injured neurons. Nogo, MAG and OMgp are three prototypical myelin inhibitors that signal through multiple neuronal receptors to exert growth inhibition. Targeting myelin inhibition alone modulates the compensatory sprouting of uninjured axons but the effect on the regeneration of injured axons is limited. Meanwhile, modulating sprouting, a naturally occurring repair mechanism, may be a more attainable therapeutic goal for promoting functional repair after CNS injury in the near term.
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20
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Awakening the stalled axon - surprises in CSPG gradients. Exp Neurol 2014; 254:12-7. [PMID: 24424282 DOI: 10.1016/j.expneurol.2013.12.025] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Revised: 12/23/2013] [Accepted: 12/25/2013] [Indexed: 01/11/2023]
Abstract
The remarkably poor regeneration of axons seen after injury of the brain and spinal cord can result in permanent loss of neural function. This failure of meaningful regeneration has been attributed to both a low intrinsic growth potential of CNS neurons and extrinsic factors that actively block axon growth in the adult CNS. Injury exacerbates this situation by increasing the expression of and exposure to proteins that actively block axonal growth in the CNS. Much experimental efforts have been aimed at overcoming the extrinsic growth inhibitory environment of the injured brain and spinal cord. A recent publication in Experimental Neurology from Kuboyama and colleagues shows that activation of protein kinase A signaling is responsible for the stalling of axon growth in gradients of CNS inhibitory molecules. This observation is unexpected given the role of cAMP signaling in supporting intrinsic growth mechanisms, emphasizing the need to consider spatial and temporal aspects of intracellular signaling in future strategies for neural repair.
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21
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Vajn K, Viljetić B, Degmečić IV, Schnaar RL, Heffer M. Differential distribution of major brain gangliosides in the adult mouse central nervous system. PLoS One 2013; 8:e75720. [PMID: 24098718 PMCID: PMC3787110 DOI: 10.1371/journal.pone.0075720] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Accepted: 08/16/2013] [Indexed: 11/24/2022] Open
Abstract
Gangliosides - sialic acid-bearing glycolipids - are major cell surface determinants on neurons and axons. The same four closely related structures, GM1, GD1a, GD1b and GT1b, comprise the majority of total brain gangliosides in mammals and birds. Gangliosides regulate the activities of proteins in the membranes in which they reside, and also act as cell-cell recognition receptors. Understanding the functions of major brain gangliosides requires knowledge of their tissue distribution, which has been accomplished in the past using biochemical and immunohistochemical methods. Armed with new knowledge about the stability and accessibility of gangliosides in tissues and new IgG-class specific monoclonal antibodies, we investigated the detailed tissue distribution of gangliosides in the adult mouse brain. Gangliosides GD1b and GT1b are widely expressed in gray and white matter. In contrast, GM1 is predominately found in white matter and GD1a is specifically expressed in certain brain nuclei/tracts. These findings are considered in relationship to the hypothesis that gangliosides GD1a and GT1b act as receptors for an important axon-myelin recognition protein, myelin-associated glycoprotein (MAG). Mediating axon-myelin interactions is but one potential function of the major brain gangliosides, and more detailed knowledge of their distribution may help direct future functional studies.
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Affiliation(s)
- Katarina Vajn
- Department of Medical Biology, University of Osijek School of Medicine, Osijek, Croatia
| | - Barbara Viljetić
- Department of Chemistry, Biochemistry and Clinical Chemistry, University of Osijek School of Medicine, Osijek, Croatia
| | | | - Ronald L. Schnaar
- Departments of Pharmacology and Neuroscience, The Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America
| | - Marija Heffer
- Department of Medical Biology, University of Osijek School of Medicine, Osijek, Croatia
- * E-mail:
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22
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Lemons ML, Abanto ML, Dambrouskas N, Clements CC, Deloughery Z, Garozzo J, Condic ML. Integrins and cAMP mediate netrin-induced growth cone collapse. Brain Res 2013; 1537:46-58. [PMID: 24001590 DOI: 10.1016/j.brainres.2013.08.045] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Revised: 08/20/2013] [Accepted: 08/25/2013] [Indexed: 12/27/2022]
Abstract
Growth cones integrate a remarkably complex concert of chemical cues to guide axons to their appropriate destinations. Recent work suggests that integrins contribute to axon guidance by interacting with a wide range of extracellular molecules including axon guidance molecules, by mechanisms that are not fully understood. Here, we describe an interaction between integrins and netrin-1 in growth cones that contributes to growth cone collapse. Our data show that netrin-1 causes growth cone collapse in a substratum-specific manner and is integrin-dependent. Netrin-1 causes collapse of cultured chick dorsal root ganglion (DRG) growth cones extending on high levels of laminin-1 (LN) but not growth cones extending on low levels of LN or on fibronectin. Blocking integrin function significantly decreases netrin-induced growth cone collapse on high LN. Netrin-1 and integrins interact on growth cones; netrin-1 causes integrin activation, a conformational shift to a high ligand-affinity state. Netrin-1 directly binds to integrin α3 and α6 peptides, further suggesting a netrin-integrin interaction. Interestingly, our data reveal that netrin-1 increases growth cone levels of cAMP in a substratum-specific manner and that netrin-induced growth cone collapse requires increased cAMP in combination with integrin activation. Manipulations that either decrease cAMP levels or integrin activation block netrin-induced collapse. These results imply a common mechanism for growth cone collapse and novel interactions between integrins, netrin-1 and cAMP that contribute to growth cone guidance.
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Affiliation(s)
- M L Lemons
- Department of Natural Sciences, Assumption College, Worcester MA 01609, United States; Department of Neurobiology and Anatomy, University of Utah School of Medicine, 401 MREB, 20 North 1900 East, Salt Lake City, UT 84132, United States.
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23
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Ng T, Ryu JR, Sohn JH, Tan T, Song H, Ming GL, Goh ELK. Class 3 semaphorin mediates dendrite growth in adult newborn neurons through Cdk5/FAK pathway. PLoS One 2013; 8:e65572. [PMID: 23762397 PMCID: PMC3677868 DOI: 10.1371/journal.pone.0065572] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Accepted: 04/26/2013] [Indexed: 01/09/2023] Open
Abstract
Class 3 semaphorins are well-known axonal guidance cues during the embryonic development of mammalian nervous system. However, their activity on postnatally differentiated neurons in neurogenic regions of adult brains has not been characterized. We found that silencing of semaphorin receptors neuropilins (NRP) 1 or 2 in neural progenitors at the adult mouse dentate gyrus resulted in newly differentiated neurons with shorter dendrites and simpler branching in vivo. Tyrosine phosphorylation (Tyr 397) and serine phosphorylation (Ser 732) of FAK were essential for these effects. Semaphorin 3A and 3F mediate serine phosphorylation of FAK through the activation of Cdk5. Silencing of either Cdk5 or FAK in newborn neurons phenocopied the defects in dendritic development seen upon silencing of NRP1 or NRP2. Furthermore, in vivo overexpression of Cdk5 or FAK rescued the dendritic phenotypes seen in NRP1 and NRP2 deficient neurons. These results point to a novel role for class 3 semaphorins in promoting dendritic growth and branching during adult hippocampal neurogenesis through the activation of Cdk5-FAK signaling pathway.
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Affiliation(s)
- Teclise Ng
- Program in Neuroscience and Behavioral Disorder, Duke-NUS Graduate Medical School, Singapore, Singapore
| | - Jae Ryun Ryu
- Program in Neuroscience and Behavioral Disorder, Duke-NUS Graduate Medical School, Singapore, Singapore
| | - Jae Ho Sohn
- Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Terence Tan
- Program in Neuroscience and Behavioral Disorder, Duke-NUS Graduate Medical School, Singapore, Singapore
| | - Hongjun Song
- Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Guo-li Ming
- Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Eyleen L. K. Goh
- Program in Neuroscience and Behavioral Disorder, Duke-NUS Graduate Medical School, Singapore, Singapore
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
- * E-mail:
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24
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Mironova YA, Giger RJ. Where no synapses go: gatekeepers of circuit remodeling and synaptic strength. Trends Neurosci 2013; 36:363-73. [PMID: 23642707 DOI: 10.1016/j.tins.2013.04.003] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Revised: 04/01/2013] [Accepted: 04/01/2013] [Indexed: 02/07/2023]
Abstract
Growth inhibitory molecules in the adult mammalian central nervous system (CNS) have been implicated in the blocking of axonal sprouting and regeneration following injury. Prominent CNS regeneration inhibitors include Nogo-A, oligodendrocyte myelin glycoprotein (OMgp), and chondroitin sulfate proteoglycans (CSPGs), and a key question concerns their physiological role in the naïve CNS. Emerging evidence suggests novel functions in dendrites and at synapses of glutamatergic neurons. CNS regeneration inhibitors target the neuronal actin cytoskeleton to regulate dendritic spine maturation, long-term synapse stability, and Hebbian forms of synaptic plasticity. This is accomplished in part by antagonizing plasticity-promoting signaling pathways activated by neurotrophic factors. Altered function of CNS regeneration inhibitors is associated with mental illness and loss of long-lasting memory, suggesting unexpected and novel physiological roles for these molecules in brain health.
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Affiliation(s)
- Yevgeniya A Mironova
- Department of Cell and Developmental Biology, University of Michigan School of Medicine, 3065 BSRB, 109 Zina Pitcher Place, Ann Arbor, MI 48109-2200, USA
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25
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Stiles TL, Dickendesher TL, Gaultier A, Fernandez-Castaneda A, Mantuano E, Giger RJ, Gonias SL. LDL receptor-related protein-1 is a sialic-acid-independent receptor for myelin-associated glycoprotein that functions in neurite outgrowth inhibition by MAG and CNS myelin. J Cell Sci 2012; 126:209-20. [PMID: 23132925 DOI: 10.1242/jcs.113191] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
In the injured adult mammalian central nervous system (CNS), products are generated that inhibit neuronal sprouting and regeneration. In recent years, most attention has focused on the myelin-associated inhibitory proteins (MAIs) Nogo-A, OMgp, and myelin-associated glycoprotein (MAG). Binding of MAIs to neuronal cell-surface receptors leads to activation of RhoA, growth cone collapse, and neurite outgrowth inhibition. In the present study, we identify low-density lipoprotein (LDL) receptor-related protein-1 (LRP1) as a high-affinity, endocytic receptor for MAG. In contrast with previously identified MAG receptors, binding of MAG to LRP1 occurs independently of terminal sialic acids. In primary neurons, functional inactivation of LRP1 with receptor-associated protein, depletion by RNA interference (RNAi) knock-down, or LRP1 gene deletion is sufficient to significantly reverse MAG and myelin-mediated inhibition of neurite outgrowth. Similar results are observed when LRP1 is antagonized in PC12 and N2a cells. By contrast, inhibiting LRP1 does not attenuate inhibition of neurite outgrowth caused by chondroitin sulfate proteoglycans. Mechanistic studies in N2a cells showed that LRP1 and p75NTR associate in a MAG-dependent manner and that MAG-mediated activation of RhoA may involve both LRP1 and p75NTR. LRP1 derivatives that include the complement-like repeat clusters CII and CIV bind MAG and other MAIs. When CII and CIV were expressed as Fc-fusion proteins, these proteins, purified full-length LRP1 and shed LRP1 all attenuated the inhibition of neurite outgrowth caused by MAG and CNS myelin in primary neurons. Collectively, our studies identify LRP1 as a novel MAG receptor that functions in neurite outgrowth inhibition.
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Affiliation(s)
- Travis L Stiles
- Department of Pathology, University of California San Diego, La Jolla, CA 92093, USA
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26
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Abstract
After central nervous system (CNS) insults, such as spinal cord injury or traumatic brain injury, neurons encounter a complex microenvironment where mechanisms that promote regeneration compete with inhibitory processes. Sprouting and axonal re-growth are key components of functional recovery, but are often counteracted by inhibitory molecules. Several strategies are being pursued whereby these inhibitory molecules are either being neutralized with blocking antibodies, with enzymatic degradation or downstream signaling events are being interfered with. Two recent studies ( 1) (,) ( 2) show that activating integrin signaling in dorsal root ganglion (DRG) neurons renders them able to overcome inhibitory signals, and could possibly lead to new strategies to improve neuronal regeneration.
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Affiliation(s)
- Stefan Plantman
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
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27
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Shivaraj MC, Marcy G, Low G, Ryu JR, Zhao X, Rosales FJ, Goh ELK. Taurine induces proliferation of neural stem cells and synapse development in the developing mouse brain. PLoS One 2012; 7:e42935. [PMID: 22916184 PMCID: PMC3423436 DOI: 10.1371/journal.pone.0042935] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Accepted: 07/15/2012] [Indexed: 12/13/2022] Open
Abstract
Taurine is a sulfur-containing amino acid present in high concentrations in mammalian tissues. It has been implicated in several processes involving brain development and neurotransmission. However, the role of taurine in hippocampal neurogenesis during brain development is still unknown. Here we show that taurine regulates neural progenitor cell (NPC) proliferation in the dentate gyrus of the developing brain as well as in cultured early postnatal (P5) hippocampal progenitor cells and hippocampal slices derived from P5 mice brains. Taurine increased cell proliferation without having a significant effect on neural differentiation both in cultured P5 NPCs as well as cultured hippocampal slices and in vivo. Expression level analysis of synaptic proteins revealed that taurine increases the expression of Synapsin 1 and PSD 95. We also found that taurine stimulates the phosphorylation of ERK1/2 indicating a possible role of the ERK pathway in mediating the changes that we observed, especially in proliferation. Taken together, our results demonstrate a role for taurine in neural stem/progenitor cell proliferation in developing brain and suggest the involvement of the ERK1/2 pathways in mediating these actions. Our study also shows that taurine influences the levels of proteins associated with synapse development. This is the first evidence showing the effect of taurine on early postnatal neuronal development using a combination of in vitro, ex-vivo and in vivo systems.
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Affiliation(s)
- Mattu Chetana Shivaraj
- Program in Neuroscience and Behavioral Disorder, Duke-NUS Graduate Medical School, Singapore, Singapore
| | - Guillaume Marcy
- Program in Neuroscience and Behavioral Disorder, Duke-NUS Graduate Medical School, Singapore, Singapore
| | - Guoliang Low
- Program in Neuroscience and Behavioral Disorder, Duke-NUS Graduate Medical School, Singapore, Singapore
| | - Jae Ryun Ryu
- Program in Neuroscience and Behavioral Disorder, Duke-NUS Graduate Medical School, Singapore, Singapore
| | - Xianfeng Zhao
- Cognition Center of Excellence, Abbott Nutrition Research & Development, Asia Pacific Center, Singapore, Singapore
| | - Francisco J. Rosales
- Cognition Center of Excellence, Abbott Nutrition Research & Development, Asia Pacific Center, Singapore, Singapore
| | - Eyleen L. K. Goh
- Program in Neuroscience and Behavioral Disorder, Duke-NUS Graduate Medical School, Singapore, Singapore
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
- A*STAR-Duke-NUS Neuroscience Research Partnership, Proteos, Singapore, Singapore
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Myers JP, Robles E, Ducharme-Smith A, Gomez TM. Focal adhesion kinase modulates Cdc42 activity downstream of positive and negative axon guidance cues. J Cell Sci 2012; 125:2918-29. [PMID: 22393238 DOI: 10.1242/jcs.100107] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
There is biochemical, imaging and functional evidence that Rho GTPase signaling is a crucial regulator of actin-based structures such as lamellipodia and filopodia. However, although Rho GTPases are believed to serve similar functions in growth cones, the spatiotemporal dynamics of Rho GTPase signaling has not been examined in living growth cones in response to known axon guidance cues. Here we provide the first measurements of Cdc42 activity in living growth cones acutely stimulated with both growth-promoting and growth-inhibiting axon-guidance cues. Interestingly, we find that both permissive and repulsive factors can work by modulating Cdc42 activity, but in opposite directions. We find that the growth-promoting factors laminin and BDNF activate Cdc42, whereas the inhibitor Slit2 reduces Cdc42 activity in growth cones. Remarkably, we find that regulation of focal adhesion kinase (FAK) activity is a common upstream modulator of Cdc42 by BDNF, laminin and Slit. These findings suggest that rapid modulation of Cdc42 signaling through FAK by receptor activation underlies changes in growth cone motility in response to permissive and repulsive guidance cues.
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Affiliation(s)
- Jonathan P Myers
- Department of Neuroscience, Medical Scientist Training Program and Neuroscience Training Program, University of Wisconsin, Madison, WI 53706, USA
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29
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Combinatorial therapy stimulates long-distance regeneration, target reinnervation, and partial recovery of vision after optic nerve injury in mice. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2012; 106:153-72. [PMID: 23211463 DOI: 10.1016/b978-0-12-407178-0.00007-7] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The optic nerve has been widely studied for insights into mechanisms that suppress or promote axon regeneration after central nervous system injury. Following optic nerve damage in adult mammals, retinal ganglion cells (RGCs) normally fail to regenerate their axons, resulting in blindness in patients who suffer from neurodegenerative diseases such as glaucoma or who have sustained traumatic injury to the optic nerve. Over the past several decades, many groups have investigated the basis of regenerative failure in the hope of developing strategies to stimulate the regrowth of axons and restore visual function. New findings show that a combination of therapies that act synergistically to activate RGCs' intrinsic growth state enables these cells to regenerate their axons the full length of the optic nerve, across the optic chiasm, and into the brain, where they establish synapses in appropriate target zones and restore limited visual responses. These treatments involve the induction of a limited inflammatory response in the eye to increase levels of oncomodulin and other growth factors; elevation of intracellular cAMP; and deletion of the pten gene in RGCs. Although these methods cannot be applied in the clinic, they point to strategies that might be.
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30
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Focal adhesion kinase promotes integrin adhesion dynamics necessary for chemotropic turning of nerve growth cones. J Neurosci 2011; 31:13585-95. [PMID: 21940449 DOI: 10.1523/jneurosci.2381-11.2011] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The ability of extending axons to navigate using combinations of extracellular cues is essential for proper neural network formation. One intracellular signaling molecule that integrates convergent signals from both extracellular matrix (ECM) proteins and growth factors is focal adhesion kinase (FAK). Analysis of FAK function shows that it influences a variety of cellular activities, including cell motility, proliferation, and differentiation. Recent work in developing neurons has shown that FAK and Src function downstream of both attractive and repulsive growth factors, but little is known about the effectors or cellular mechanisms that FAK controls in growth cones on ECM proteins. We report that FAK functions downstream of brain-derived neurotrophic factor (BDNF) and laminin in the modulation of point contact dynamics, phosphotyrosine signaling at filopodial tips, and lamellipodial protrusion. BDNF stimulation accelerates paxillin-containing point contact turnover and formation. Knockdown of FAK function either with a FAK antisense morpholino or by expression of FRNK, a dominant-negative FAK isoform, blocks all aspects of the response to BDNF, including the acceleration of point contact dynamics. On the other hand, expression of specific FAK point mutants can selectively disrupt distinct aspects of the response to BDNF. We also show that growth cone turning depends on both signaling cascades tested here. Finally, we provide the first evidence that growth cone point contacts are asymmetrically regulated during turning to an attractive guidance cue.
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31
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Wilkinson AE, McCormick AM, Leipzig ND. Central Nervous System Tissue Engineering: Current Considerations and Strategies. ACTA ACUST UNITED AC 2011. [DOI: 10.2200/s00390ed1v01y201111tis008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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32
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Steinbach K, McDonald CL, Reindl M, Schweigreiter R, Bandtlow C, Martin R. Nogo-receptors NgR1 and NgR2 do not mediate regulation of CD4 T helper responses and CNS repair in experimental autoimmune encephalomyelitis. PLoS One 2011; 6:e26341. [PMID: 22096481 PMCID: PMC3214013 DOI: 10.1371/journal.pone.0026341] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2011] [Accepted: 09/25/2011] [Indexed: 11/28/2022] Open
Abstract
Myelin-associated inhibition of axonal regrowth after injury is considered one important factor that contributes to regeneration failure in the adult central nervous system (CNS). Blocking strategies targeting this pathway have been successfully applied in several nerve injury models, including experimental autoimmune encephalomyelitis (EAE), suggesting myelin-associated inhibitors (MAIs) and functionally related molecules as targets to enhance regeneration in multiple sclerosis. NgR1 and NgR2 were identified as interaction partners for the myelin proteins Nogo-A, MAG and OMgp and are probably mediating their growth-inhibitory effects on axons, although the in vivo relevance of this pathway is currently under debate. Recently, alternative functions of MAIs and NgRs in the regulation of immune cell migration and T cell differentiation have been described. Whether and to what extent NgR1 and NgR2 are contributing to Nogo and MAG-related inhibition of neuroregeneration or immunomodulation during EAE is currently unknown. Here we show that genetic deletion of both receptors does not promote functional recovery during EAE and that NgR1 and NgR2-mediated signals play a minor role in the development of CNS inflammation. Induction of EAE in Ngr1/2-double mutant mice resulted in indifferent disease course and tissue damage when compared to WT controls. Further, the development of encephalitogenic CD4+ Th1 and Th17 responses was unchanged. However, we observed a slightly increased leukocyte infiltration into the CNS in the absence of NgR1 and NgR2, indicating that NgRs might be involved in the regulation of immune cell migration in the CNS. Our study demonstrates the urgent need for a more detailed knowledge on the multifunctional roles of ligands and receptors involved in CNS regeneration failure.
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Affiliation(s)
- Karin Steinbach
- Institute for Neuroimmunology and Clinical MS-Research, Hamburg, Germany
| | - Claire L. McDonald
- Clinical Department of Neurology, Innsbruck Medical University, Innsbruck, Austria
| | - Markus Reindl
- Clinical Department of Neurology, Innsbruck Medical University, Innsbruck, Austria
| | | | - Christine Bandtlow
- Department of Neurobiochemistry, Innsbruck Medical University, Innsbruck, Austria
| | - Roland Martin
- Institute for Neuroimmunology and Clinical MS-Research, Hamburg, Germany
- * E-mail:
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33
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Myers JP, Santiago-Medina M, Gomez TM. Regulation of axonal outgrowth and pathfinding by integrin-ECM interactions. Dev Neurobiol 2011; 71:901-23. [PMID: 21714101 PMCID: PMC3192254 DOI: 10.1002/dneu.20931] [Citation(s) in RCA: 157] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Developing neurons use a combination of guidance cues to assemble a functional neural network. A variety of proteins immobilized within the extracellular matrix (ECM) provide specific binding sites for integrin receptors on neurons. Integrin receptors on growth cones associate with a number of cytosolic adaptor and signaling proteins that regulate cytoskeletal dynamics and cell adhesion. Recent evidence suggests that soluble growth factors and classic axon guidance cues may direct axon pathfinding by controlling integrin-based adhesion. Moreover, because classic axon guidance cues themselves are immobilized within the ECM and integrins modulate cellular responses to many axon guidance cues, interactions between activated receptors modulate cell signals and adhesion. Ultimately, growth cones control axon outgrowth and pathfinding behaviors by integrating distinct biochemical signals to promote the proper assembly of the nervous system. In this review, we discuss our current understanding how ECM proteins and their associated integrin receptors control neural network formation.
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Affiliation(s)
- Jonathan P Myers
- Department of Neuroscience, Neuroscience Training Program, University of Wisconsin, Madison, Wisconsin 53706, USA
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34
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Gardiner NJ. Integrins and the extracellular matrix: Key mediators of development and regeneration of the sensory nervous system. Dev Neurobiol 2011; 71:1054-72. [DOI: 10.1002/dneu.20950] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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35
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Monje FJ, Kim EJ, Pollak DD, Cabatic M, Li L, Baston A, Lubec G. Focal adhesion kinase regulates neuronal growth, synaptic plasticity and hippocampus-dependent spatial learning and memory. Neurosignals 2011; 20:1-14. [PMID: 21952616 DOI: 10.1159/000330193] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2011] [Accepted: 06/20/2011] [Indexed: 01/07/2023] Open
Abstract
The focal adhesion kinase (FAK) is a non-receptor tyrosine kinase abundantly expressed in the mammalian brain and highly enriched in neuronal growth cones. Inhibitory and facilitatory activities of FAK on neuronal growth have been reported and its role in neuritic outgrowth remains controversial. Unlike other tyrosine kinases, such as the neurotrophin receptors regulating neuronal growth and plasticity, the relevance of FAK for learning and memory in vivo has not been clearly defined yet. A comprehensive study aimed at determining the role of FAK in neuronal growth, neurotransmitter release and synaptic plasticity in hippocampal neurons and in hippocampus-dependent learning and memory was therefore undertaken using the mouse model. Gain- and loss-of-function experiments indicated that FAK is a critical regulator of hippocampal cell morphology. FAK mediated neurotrophin-induced neuritic outgrowth and FAK inhibition affected both miniature excitatory postsynaptic potentials and activity-dependent hippocampal long-term potentiation prompting us to explore the possible role of FAK in spatial learning and memory in vivo. Our data indicate that FAK has a growth-promoting effect, is importantly involved in the regulation of the synaptic function and mediates in vivo hippocampus-dependent spatial learning and memory.
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Affiliation(s)
- Francisco J Monje
- Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Vienna, Austria
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36
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Xu X, Warrington AE, Bieber AJ, Rodriguez M. Enhancing CNS repair in neurological disease: challenges arising from neurodegeneration and rewiring of the network. CNS Drugs 2011; 25:555-73. [PMID: 21699269 PMCID: PMC3140701 DOI: 10.2165/11587830-000000000-00000] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Repair of the central nervous system (CNS) constitutes an integral part of treating neurological disease and plays a crucial role in restoring CNS architecture and function. Distinct strategies have been developed to reconstruct the damaged neural tissue, with many tested preclinically in animal models. We review cell replacement-based repair strategies. By taking spinal cord injury, cerebral ischaemia and degenerative CNS disorders as examples for CNS repair, we discuss progress and potential problems in utilizing embryonic stem cells and adult neural/non-neural stem cells to repair cell loss in the CNS. Nevertheless, CNS repair is not simply a matter of cell transplantation. The major challenge is to induce regenerating neural cells to integrate into the neural network and compensate for damaged neural function. The neural cells confront an environment very different from that of the developmental stage in which these cells differentiate to form interwoven networks. During the repair process, one of the challenges is neurodegeneration, which can develop from interrupted innervations to/from the targets, chronic inflammation, ischaemia, aging or idiopathic neural toxicity. Neurodegeneration, which occurs on the basis of a characteristic vascular and neural web, usually presents as a chronically progressive process with unknown aetiology. Currently, there is no effective treatment to stop or slow down neurodegeneration. Pathological changes from patients with Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis indicate a broken homeostasis in the CNS. We discuss how the blood-brain barrier and neural networks are formed to maintain CNS homeostasis and their contribution to neurodegeneration in diseased conditions. Another challenge is that some inhibitors produced by CNS injury do not facilitate the regenerating neural cells to incorporate into a pre-existing network. We review glial responses to CNS injury. Of note, the reactive astrocytes not only encompass the lesions/pathogens but may also form glial scars to impede regenerating axons from traversing the lesions. In addition, myelin debris can prevent axon growth. Myelination enables saltatory transduction of electrical impulses along axonal calibers and actually provides trophic support to stabilize the axons. Therefore, repair strategies should be designed to promote axonal growth, myelination and modulate astrocytic responses. Finally, we discuss recent progress in developing human monoclonal IgMs that regulate CNS homeostasis and promote neural regeneration.
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Affiliation(s)
- Xiaohua Xu
- Department of Neurology, Mayo Clinic and Foundation, Rochester, MN 55905
| | | | - Allan J. Bieber
- Department of Neurology, Mayo Clinic and Foundation, Rochester, MN 55905
| | - Moses Rodriguez
- Department of Neurology, Mayo Clinic and Foundation, Rochester, MN 55905, Department of Immunology, Mayo Clinic and Foundation, Rochester, MN 55905
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37
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Zaichick SV, Bohannon KP, Smith GA. Alphaherpesviruses and the cytoskeleton in neuronal infections. Viruses 2011; 3:941-81. [PMID: 21994765 PMCID: PMC3185784 DOI: 10.3390/v3070941] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Revised: 06/03/2011] [Accepted: 06/17/2011] [Indexed: 12/13/2022] Open
Abstract
Following infection of exposed peripheral tissues, neurotropic alphaherpesviruses invade nerve endings and deposit their DNA genomes into the nuclei of neurons resident in ganglia of the peripheral nervous system. The end result of these events is the establishment of a life-long latent infection. Neuroinvasion typically requires efficient viral transmission through a polarized epithelium followed by long-distance transport through the viscous axoplasm. These events are mediated by the recruitment of the cellular microtubule motor proteins to the intracellular viral particle and by alterations to the cytoskeletal architecture. The focus of this review is the interplay between neurotropic herpesviruses and the cytoskeleton.
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Affiliation(s)
- Sofia V Zaichick
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
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38
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Lee JK, Zheng B. Role of myelin-associated inhibitors in axonal repair after spinal cord injury. Exp Neurol 2011; 235:33-42. [PMID: 21596039 DOI: 10.1016/j.expneurol.2011.05.001] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2010] [Revised: 04/19/2011] [Accepted: 05/01/2011] [Indexed: 12/15/2022]
Abstract
Myelin-associated inhibitors of axon growth, including Nogo, MAG and OMgp, have been the subject of intense research. A myriad of experimental approaches have been applied to investigate the potential of targeting these molecules to promote axonal repair after spinal cord injury. However, there are still conflicting results on their role in axon regeneration and therefore a lack of a cohesive mechanism on how these molecules can be targeted to promote axon repair. One major reason may be the lack of a clear definition of axon regeneration in the first place. Nevertheless, recent data from genetic studies in mice indicate that the roles of these molecules in CNS axon repair may be more intricate than previously envisioned.
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Affiliation(s)
- Jae K Lee
- University of California San Diego, Department of Neurosciences, 9500 Gilman Drive, MC 0691, La Jolla, CA 92093-0691, USA.
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39
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Zai L, Ferrari C, Dice C, Subbaiah S, Havton LA, Coppola G, Geschwind D, Irwin N, Huebner E, Strittmatter SM, Benowitz LI. Inosine augments the effects of a Nogo receptor blocker and of environmental enrichment to restore skilled forelimb use after stroke. J Neurosci 2011; 31:5977-88. [PMID: 21508223 PMCID: PMC3101108 DOI: 10.1523/jneurosci.4498-10.2011] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2010] [Revised: 02/17/2011] [Accepted: 02/19/2011] [Indexed: 01/28/2023] Open
Abstract
Stroke is the leading cause of disability in much of the world, with few treatment options available. Following unilateral stroke in rats, inosine, a naturally occurring purine nucleoside, stimulates the growth of projections from the undamaged hemisphere into denervated areas of the spinal cord and improves skilled use of the impaired forelimb. Inosine augments neurons' intrinsic growth potential by activating Mst3b, a component of the signal transduction pathway through which trophic factors regulate axon outgrowth. The present study investigated whether inosine would complement the effects of treatments that promote plasticity through other mechanisms. Following unilateral stroke in the rat forelimb motor area, inosine combined with NEP1-40, a Nogo receptor antagonist, doubled the number of axon branches extending from neurons in the intact hemisphere into the denervated side of the spinal cord compared with either treatment alone, and restored rats' level of skilled reaching using the impaired forepaw to preoperative levels. Similar functional improvements were seen when inosine was combined with environmental enrichment (EE). The latter effect was associated with changes in gene expression in layer 5 pyramidal neurons of the undamaged cortex well beyond those seen with inosine or EE alone. Inosine is now in clinical trials for other indications, making it an attractive candidate for the treatment of stroke patients.
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Affiliation(s)
- Laila Zai
- Laboratories for Neuroscience Research in Neurosurgery and
- F. M. Kirby Neurobiology Center, Children's Hospital, Boston, Massachusetts 02115
- Department of Surgery, Harvard Medical School, Boston, Massachusetts 02115
| | | | - Carlie Dice
- Laboratories for Neuroscience Research in Neurosurgery and
| | - Sathish Subbaiah
- Laboratories for Neuroscience Research in Neurosurgery and
- Department of Surgery, Harvard Medical School, Boston, Massachusetts 02115
| | | | - Giovanni Coppola
- Department of Neurology and
- Neurogenetics Program, University of California, Los Angeles, Los Angeles, California 90095, and
| | - Daniel Geschwind
- Department of Neurology and
- Neurogenetics Program, University of California, Los Angeles, Los Angeles, California 90095, and
| | - Nina Irwin
- Laboratories for Neuroscience Research in Neurosurgery and
- F. M. Kirby Neurobiology Center, Children's Hospital, Boston, Massachusetts 02115
- Department of Surgery, Harvard Medical School, Boston, Massachusetts 02115
| | - Eric Huebner
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06520
| | | | - Larry I. Benowitz
- Laboratories for Neuroscience Research in Neurosurgery and
- F. M. Kirby Neurobiology Center, Children's Hospital, Boston, Massachusetts 02115
- Program in Neuroscience and
- Department of Surgery, Harvard Medical School, Boston, Massachusetts 02115
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40
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Second messengers and membrane trafficking direct and organize growth cone steering. Nat Rev Neurosci 2011; 12:191-203. [PMID: 21386859 DOI: 10.1038/nrn2996] [Citation(s) in RCA: 154] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Graded distributions of extracellular cues guide developing axons toward their targets. A network of second messengers - Ca(2+) and cyclic nucleotides - shapes cue-derived information into either attractive or repulsive signals that steer growth cones bidirectionally. Emerging evidence suggests that such guidance signals create a localized imbalance between exocytosis and endocytosis, which in turn redirects membrane, adhesion and cytoskeletal components asymmetrically across the growth cone to bias the direction of axon extension. These recent advances allow us to propose a unifying model of how the growth cone translates shallow gradients of environmental information into polarized activity of the steering machinery for axon guidance.
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Lopez PHH, Ahmad AS, Mehta NR, Toner M, Rowland EA, Zhang J, Doré S, Schnaar RL. Myelin-associated glycoprotein protects neurons from excitotoxicity. J Neurochem 2011; 116:900-8. [PMID: 21214567 DOI: 10.1111/j.1471-4159.2010.07069.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
In addition to supporting rapid nerve conduction, myelination nurtures and stabilizes axons and protects them from acute toxic insults. One myelin molecule that protects and sustains axons is myelin-associated glycoprotein (MAG). MAG is expressed on the innermost wrap of myelin, apposed to the axon surface, where it interacts with axonal receptors that reside in lateral membrane domains including gangliosides, the glycosylphosphatidylinositol-anchored Nogo receptors, and β1-integrin. We report here that MAG protection extends beyond the axon to the neurons from which those axons emanate, protecting them from excitotoxicity. Compared to wild type mice, Mag-null mice displayed markedly increased seizure activity in response to intraperitoneal injection of kainic acid, an excitotoxic glutamate receptor agonist. Mag-null mice also had larger lesion volumes in response to intrastriatal injection of the excitotoxin NMDA. Prior injection of a soluble form of MAG partially protected Mag-null mice from NMDA-induced lesions. Hippocampal neurons plated on proteins extracted from wild-type rat or mouse myelin were resistant to kainic acid-induced excitotoxicity, whereas neurons plated on proteins from Mag-null myelin were not. Protection was reversed by anti-MAG antibody and replicated by addition of soluble MAG. MAG-mediated protection from excitotoxicity was dependent on Nogo receptors and β1-integrin. We conclude that MAG engages membrane-domain resident neuronal receptors to protect neurons from excitotoxicity, and that soluble MAG mitigates excitotoxic damage in vivo.
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Affiliation(s)
- Pablo H H Lopez
- Department of Pharmacology and Molecular Sciences, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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Shypitsyna A, Málaga-Trillo E, Reuter A, Stuermer CAO. Origin of Nogo-A by domain shuffling in an early jawed vertebrate. Mol Biol Evol 2010; 28:1363-70. [PMID: 21098000 DOI: 10.1093/molbev/msq313] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Unlike mammals, fish are able to regenerate axons in their central nervous system. This difference has been partly attributed to the loss/acquisition of inhibitory proteins during evolution. Nogo-A--the longest isoform of the reticulon4 (rtn4) gene product--is commonly found in mammalian myelin where it acts as a potent inhibitor of axonal regeneration. Interestingly, fish RTN4 isoforms were previously reported to lack the most inhibitory Nogo-A-specific region (NSR). Nevertheless, fish axons collapse on contact with mammalian NSR, suggesting that fish possess a functional Nogo-A receptor but not its ligand. To reconcile these findings, we revisited the early evolution of rtn4. Mining of current genome databases established the unequivocal presence of NSR-coding sequences in fish rtn4 paralogues. Further comparative analyses indicate that the common ancestor of fish and tetrapods had an NSR-coding rtn4 gene, which underwent duplication and divergent evolution in bony fish. Our genomic survey also revealed that the cephalochordate Branchiostoma floridae contains a single rtn gene lacking the NSR. Hence, Nogo-A most probably arose independently in the rtn4 gene of a gnathostome ancestor before the split of the fish and tetrapod lineages. Close examination of the NSR uncovered clusters of structural and sequential similarities with neurocan (NCAN), an inhibitory proteoglycan of the glial scar. Notably, the shared presence of transposable elements in ncan and rtn4 genes suggests that Nogo-A originated via insertion of an ncan-like sequence into the rtn4 gene of an early jawed vertebrate with myelinated axons.
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Combined genetic attenuation of myelin and semaphorin-mediated growth inhibition is insufficient to promote serotonergic axon regeneration. J Neurosci 2010; 30:10899-904. [PMID: 20702718 DOI: 10.1523/jneurosci.2269-10.2010] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
After CNS injuries, axon growth inhibitors from the myelin and the scar tissue at the injury site are considered major impediments to axon regeneration. The presence of several classes of inhibitors with multiple members in each class suggests functional redundancy in growth inhibition. To test redundancy within the myelin inhibitory pathway, we analyzed raphe spinal serotonergic (5-HT) axon regeneration in mice deficient in two major myelin inhibitors, Nogo and MAG, and their common receptor NgR1 (or NgR). After a complete transection spinal cord injury, there was no significant enhancement of 5-HT axon regeneration beyond the injury site in either Nogo/MAG/NgR1 triple mutants or NgR1 single mutants. Occasional, genotype-independent traversal of 5-HT axons through GFAP-positive tissue bridges at the injury site implicates GFAP-negative lesion areas as especially inhibitory to 5-HT axons. To assess the contribution of class 3 Semaphorins that are expressed by GFAP-negative meningeal fibroblasts at the injury site, we analyzed mice deficient in PlexinA3 and PlexinA4, two key receptors for class 3 Semaphorins, with or without additional NgR1 deletion. No enhanced regeneration of 5-HT or corticospinal axons was detected in PlexinA3/PlexinA4 double mutants or PlexinA3/PlexinA4/NgR1 triple mutants through a complete transection injury. In contrast with previous reports, these data demonstrate that attenuating myelin or Semaphorin-mediated inhibition of axon growth is insufficient to promote 5-HT axon regeneration and further indicate that even attenuating both classes of inhibitory influences is insufficient to promote regeneration of injured axons through a complete transection spinal cord injury.
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Wright K, Seabright R, Logan A, Lilly A, Khanim F, Bunce C, Johnson W. Extracellular Nm23H1 stimulates neurite outgrowth from dorsal root ganglia neurons in vitro independently of nerve growth factor supplementation or its nucleoside diphosphate kinase activity. Biochem Biophys Res Commun 2010; 398:79-85. [DOI: 10.1016/j.bbrc.2010.06.039] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2010] [Accepted: 06/09/2010] [Indexed: 10/19/2022]
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Hines JH, Abu-Rub M, Henley JR. Asymmetric endocytosis and remodeling of beta1-integrin adhesions during growth cone chemorepulsion by MAG. Nat Neurosci 2010; 13:829-37. [PMID: 20512137 DOI: 10.1038/nn.2554] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2010] [Accepted: 04/15/2010] [Indexed: 12/11/2022]
Abstract
Gradients of chemorepellent factors released from myelin may impair axon pathfinding and neuroregeneration after injury. We found that, analogously to the process of chemotaxis in invasive tumor cells, axonal growth cones of Xenopus spinal neurons modulate the functional distribution of integrin receptors during chemorepulsion induced by myelin-associated glycoprotein (MAG). A focal MAG gradient induced polarized endocytosis and concomitant asymmetric loss of beta(1)-integrin and vinculin-containing adhesions on the repellent side during repulsive turning. Loss of symmetrical beta(1)-integrin function was both necessary and sufficient for chemorepulsion, which required internalization by clathrin-mediated endocytosis. Induction of repulsive Ca(2+) signals was necessary and sufficient for the stimulated rapid endocytosis of beta(1)-integrin. Altogether, these findings identify beta(1)-integrin as an important functional cargo during Ca(2+)-dependent rapid endocytosis stimulated by a diffusible guidance cue. Such dynamic redistribution allows the growth cone to rapidly adjust adhesiveness across its axis, an essential feature for initiating chemotactic turning.
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Affiliation(s)
- Jacob H Hines
- Mayo Graduate School, Mayo Clinic, Rochester, Minnesota, USA
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Seira O, Gavín R, Gil V, Llorens F, Rangel A, Soriano E, del Río JA. Neurites regrowth of cortical neurons by GSK3beta inhibition independently of Nogo receptor 1. J Neurochem 2010; 113:1644-58. [PMID: 20374426 DOI: 10.1111/j.1471-4159.2010.06726.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Lesioned axons do not regenerate in the adult mammalian CNS, owing to the over-expression of inhibitory molecules such as myelin-derived proteins or chondroitin sulphate proteoglycans. In order to overcome axon inhibition, strategies based on extrinsic and intrinsic treatments have been developed. For myelin-associated inhibition, blockage with NEP1-40, receptor bodies or IN-1 antibodies has been used. In addition, endogenous blockage of cell signalling mechanisms induced by myelin-associated proteins is a potential tool for overcoming axon inhibitory signals. We examined the participation of glycogen synthase kinase 3beta (GSK3beta) and extracellular-related kinase (ERK) 1/2 in axon regeneration failure in lesioned cortical neurons. We also investigated whether pharmacological blockage of GSK3beta and ERK1/2 activities facilitates regeneration after myelin-directed inhibition in two models: (i) cerebellar granule cells and (ii) lesioned entorhino-hippocampal pathway in slice cultures, and whether the regenerative effects are mediated by Nogo Receptor 1 (NgR1). We demonstrate that, in contrast to ERK1/2 inhibition, the pharmacological treatment of GSK3beta inhibition strongly facilitated regrowth of cerebellar granule neurons over myelin independently of NgR1. Finally, these regenerative effects were corroborated in the lesioned entorhino-hippocampal pathway in NgR1-/- mutant mice. These results provide new findings for the development of new assays and strategies to enhance axon regeneration in injured cortical connections.
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Affiliation(s)
- Oscar Seira
- Molecular and Cellular Neurobiotechnology, Institute for Bioengineering of Catalonia, Barcelona, Spain
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Gao Y, Deng K, Cao Z, Graziani EI, Gilbert AM, Koehn FE, Wood A, Doherty P, Walsh FS. Amphotericin B, identified from a natural product screen, antagonizes CNS inhibitors to promote axon growth via activation of an Akt pathway in neurons. J Neurochem 2010; 113:1331-42. [PMID: 20345749 DOI: 10.1111/j.1471-4159.2010.06704.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
One of the major barriers to successful axon regeneration in the adult CNS is the presence of inhibitory molecules that originate from the myelin sheath and glial scar. So far, only a small number of pharmacological compounds have exhibited functional activity against CNS inhibitors in promoting axon regeneration after injury. To search for novel compounds that enhance neurite outgrowth in vitro, we initiated a screen of a collection of natural products. We identified four compounds with the potential to promote growth over a myelin substrate. Of these, Amphotericin B (AmB) was shown to enhance neurite outgrowth and antagonize activities of major myelin associated inhibitors and glial-scar-derived chondroitin sulfate proteoglycans. AmB was found to activate Akt and thereby suppress the activity of glycogen synthase kinase 3 beta. Also, a cell permeable peptide that inhibits Akt activity was shown to block the effect of AmB in promoting axonal growth, while another peptide that increases Akt activity stimulated axonal growth in the presence of the myelin associated inhibitors. Our results suggest that AmB can promote neurite outgrowth over a wide range of inhibitory substrates via a mechanism that involves activation of Akt.
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Affiliation(s)
- Ying Gao
- Discovery Neuroscience, Pfizer Research, Princeton, New Jersey, USA
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Mehta NR, Nguyen T, Bullen JW, Griffin JW, Schnaar RL. Myelin-associated glycoprotein (MAG) protects neurons from acute toxicity using a ganglioside-dependent mechanism. ACS Chem Neurosci 2010; 1:215-222. [PMID: 20436925 DOI: 10.1021/cn900029p] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Myelin-associated glycoprotein (MAG), a protein expressed on the innermost wrap of myelin, contributes to long-term axon stability as evidenced by progressive axon degeneration in Mag-null mice. Recently, MAG was also found to protect axons from acute toxic insults. In the current study, rat dorsal root ganglion neurons were cultured on control substrata and substrata adsorbed with myelin proteins. Neurons on myelin-adsorbed surfaces were resistant to acute degeneration of neurites induced by vincristine, a cancer chemotherapeutic agent with neuropathic side effects. Myelin-mediated protection was reversed by anti-MAG antibody and was absent when cells were cultured on extracts from Mag-null mouse myelin, confirming the protective role of MAG. Gangliosides (sialylated glycosphingolipids) are one functional class of axonal receptors for MAG. In the current studies, a direct role for gangliosides in mediating the acute protective effects of MAG was established. Treatment of neurons with sialidase, an enzyme that cleaves the terminal sialic acids required for MAG binding, reversed MAG's protective effect, as did treatment with (1R,2R)-1-phenyl-2-hexadecanoylamino-3-pyrrolidino-1-propanol, an inhibitor of glycosphingolipid biosynthesis. In contrast, treatment with phosphatidylinositol-specific phospholipase C, an enzyme that cleaves Nogo receptors (NgR, another class of MAG receptor), or with a peptide inhibitor of an NgR-associated signaling molecule p75(NTR), failed to diminish MAG-mediated protection. Inhibiting the Rho-associated protein kinase ROCK reversed protection. We conclude that MAG protects neurites from acute toxic insult via a ganglioside-mediated signaling pathway that involves activation of RhoA. Understanding MAG-mediated protection may provide opportunities to reduce axonal damage and loss.
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Schnaar RL, Lopez PHH. Myelin-associated glycoprotein and its axonal receptors. J Neurosci Res 2010; 87:3267-76. [PMID: 19156870 DOI: 10.1002/jnr.21992] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Myelin-associated glycoprotein (MAG) is expressed on the innermost myelin membrane wrap, directly apposed to the axon surface. Although it is not required for myelination, MAG enhances long-term axon-myelin stability, helps to structure nodes of Ranvier, and regulates the axon cytoskeleton. In addition to its role in axon-myelin stabilization, MAG inhibits axon regeneration after injury; MAG and a discrete set of other molecules on residual myelin membranes at injury sites actively signal axons to halt elongation. Both the stabilizing and the axon outgrowth inhibitory effects of MAG are mediated by complementary MAG receptors on the axon surface. Two MAG receptor families have been described, sialoglycans (specifically gangliosides GD1a and GT1b) and Nogo receptors (NgRs). Controversies remain about which receptor(s) mediates which of MAG's biological effects. Here we review the findings and challenges in associating MAG's biological effects with specific receptors.
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Affiliation(s)
- Ronald L Schnaar
- Department of Pharmacology, The Johns Hopkins School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205, USA.
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Hanke N, Kubis HP, Scheibe RJ, Berthold-Losleben M, Hüsing O, Meissner JD, Gros G. Passive mechanical forces upregulate the fast myosin heavy chain IId/x via integrin and p38 MAP kinase activation in a primary muscle cell culture. Am J Physiol Cell Physiol 2010; 298:C910-20. [PMID: 20071689 DOI: 10.1152/ajpcell.00265.2009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have studied the mechanism by which a previously described primary muscle culture growing on microcarriers predominantly expresses fast myosin heavy chain (MHC) IId/x. We have measured MHC IId/x mRNA and protein levels, mRNA of MHC I and markers of muscle metabolism, insulin-like growth factor (IGF)-1 and mechano-growth factor (MGF) transcripts, indicators of the activation of the Akt-mammalian target of rapamycin (mTOR) axis, the p38-, ERK1/2-, and JNK-mitogen-activated protein kinase (MAP) kinase pathways, and of protein phosphatase PP2A, and we have assessed the involvement of integrin. By placing the culture flasks on a rotary shaker, we induce a continuous motion of the culture medium in which the carrier-myotube aggregates are suspended. This motion exerts passive forces on the myotubes that are decisive for the predominance of MHC II expression. These forces act via integrin, which transduces the mechanical signal into activation of PP2A and of p38 MAP-Kinase. The latter presumably is directly responsible for a drastic upregulation of MHC IId/x, whereas MHC I and metabolic markers remain unaffected. At the same time, despite an elevated level of IGF-1 transcription under passive forces, the IGF-1 receptor-Akt-mTOR axis is switched off as evident from the lack of an effect of inhibition of the IGF-1 receptor and from the PP2A-mediated low degree of phosphorylation of Akt and 4E-BP1. Similarly, the ERK1/2- and JNK-MAP kinase pathways are repressed. We conclude that passive stretch exerted on the myotubes by the rotary fluid motion induces a rather selective upregulation of fast MHC II, which goes along with a mild muscle hypertrophy as judged from the amount of protein per cell and is caused by p38 MAP kinase activity elevated via integrin sensing. The direct link between passive stretch and MHC II expression constitutes a novel mechanism, which is expected to become effective physiologically under passive stretch and eccentric contractions of skeletal muscles.
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Affiliation(s)
- Nina Hanke
- Zentrum Physiologie, Vegetative Physiologie, Medizinische Hochschule Hannover, 30625 Hannover, Germany
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