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Siddiq MM, Johnson NP, Zorina Y, Yadaw AS, Toro CA, Hansen J, Rabinovich V, Gregorich SM, Xiong Y, Tolentino RE, Hannila SS, Kaplan E, Blitzer RD, Filbin MT, Cardozo CP, Passaglia CL, Iyengar R. A spatially specified systems pharmacology therapy for axonal recovery after injury. Front Pharmacol 2023; 14:1225759. [PMID: 37799971 PMCID: PMC10547904 DOI: 10.3389/fphar.2023.1225759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Accepted: 09/06/2023] [Indexed: 10/07/2023] Open
Abstract
There are no known drugs or drug combinations that promote substantial central nervous system axonal regeneration after injury. We used systems pharmacology approaches to model pathways underlying axonal growth and identify a four-drug combination that regulates multiple subcellular processes in the cell body and axons using the optic nerve crush model in rats. We intravitreally injected agonists HU-210 (cannabinoid receptor-1) and IL-6 (interleukin 6 receptor) to stimulate retinal ganglion cells for axonal growth. We applied, in gel foam at the site of nerve injury, Taxol to stabilize growing microtubules, and activated protein C to clear the debris field since computational models predicted that this drug combination regulating two subcellular processes at the growth cone produces synergistic growth. Physiologically, drug treatment restored or preserved pattern electroretinograms and some of the animals had detectable visual evoked potentials in the brain and behavioral optokinetic responses. Morphology experiments show that the four-drug combination protects axons or promotes axonal regrowth to the optic chiasm and beyond. We conclude that spatially targeted drug treatment is therapeutically relevant and can restore limited functional recovery.
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Affiliation(s)
- Mustafa M. Siddiq
- Department of Pharmacological Sciences, Mount Sinai Institute for Systems Biomedicine, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Nicholas P. Johnson
- Department of Pharmacological Sciences, Mount Sinai Institute for Systems Biomedicine, Icahn School of Medicine at Mount Sinai, New York, NY, United States
- Departments of Chemical and Biomedical Engineering, University of South Florida, Tampa, FL, United States
- National Center for the Medical Consequences of Spinal Cord Injury, James J. Peters VA Medical Center, New York, NY, United States
| | - Yana Zorina
- Department of Pharmacological Sciences, Mount Sinai Institute for Systems Biomedicine, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Arjun Singh Yadaw
- Department of Pharmacological Sciences, Mount Sinai Institute for Systems Biomedicine, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Carlos A. Toro
- National Center for the Medical Consequences of Spinal Cord Injury, James J. Peters VA Medical Center, New York, NY, United States
- Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Jens Hansen
- Department of Pharmacological Sciences, Mount Sinai Institute for Systems Biomedicine, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Vera Rabinovich
- Department of Pharmacological Sciences, Mount Sinai Institute for Systems Biomedicine, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Sarah M. Gregorich
- Departments of Chemical and Biomedical Engineering, University of South Florida, Tampa, FL, United States
| | - Yuguang Xiong
- Department of Pharmacological Sciences, Mount Sinai Institute for Systems Biomedicine, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Rosa E. Tolentino
- Department of Pharmacological Sciences, Mount Sinai Institute for Systems Biomedicine, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Sari S. Hannila
- Department of Human Anatomy and Cell Science, Basic Medical Sciences Building, Winnipeg, NM, United States
| | - Ehud Kaplan
- Department of Pharmacological Sciences, Mount Sinai Institute for Systems Biomedicine, Icahn School of Medicine at Mount Sinai, New York, NY, United States
- Department of Philosophy of Science, Prague and the National Institute of Mental Health, Charles University, Prague, CZ, United States
| | - Robert D. Blitzer
- Department of Pharmacological Sciences, Mount Sinai Institute for Systems Biomedicine, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Marie T. Filbin
- Department of Biological Sciences, Hunter College, City University of New York, New York, NY, United States
| | - Christopher P. Cardozo
- National Center for the Medical Consequences of Spinal Cord Injury, James J. Peters VA Medical Center, New York, NY, United States
- Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, United States
- Department of Rehabilitation Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Christopher L. Passaglia
- Departments of Chemical and Biomedical Engineering, University of South Florida, Tampa, FL, United States
| | - Ravi Iyengar
- Department of Pharmacological Sciences, Mount Sinai Institute for Systems Biomedicine, Icahn School of Medicine at Mount Sinai, New York, NY, United States
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2
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Siddiq MM, Hannila SS, Zorina Y, Nikulina E, Rabinovich V, Hou J, Huq R, Richman EL, Tolentino RE, Hansen J, Velenosi A, Kwon BK, Tsirka SE, Maze I, Sebra R, Beaumont KG, Toro CA, Cardozo CP, Iyengar R, Filbin MT. Extracellular histones, a new class of inhibitory molecules of CNS axonal regeneration. Brain Commun 2022; 3:fcab271. [PMID: 34993473 PMCID: PMC8728726 DOI: 10.1093/braincomms/fcab271] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 08/05/2021] [Accepted: 08/30/2021] [Indexed: 12/26/2022] Open
Abstract
Axonal regeneration in the mature CNS is limited by extracellular inhibitory factors. Triple knockout mice lacking the major myelin-associated inhibitors do not display spontaneous regeneration after injury, indicating the presence of other inhibitors. Searching for such inhibitors, we have detected elevated levels of histone H3 in human CSF 24 h after spinal cord injury. Following dorsal column lesions in mice and optic nerve crushes in rats, elevated levels of extracellular histone H3 were detected at the injury site. Similar to myelin-associated inhibitors, these extracellular histones induced growth cone collapse and inhibited neurite outgrowth. Histones mediate inhibition through the transcription factor Y-box-binding protein 1 and Toll-like receptor 2, and these effects are independent of the Nogo receptor. Histone-mediated inhibition can be reversed by the addition of activated protein C in vitro, and activated protein C treatment promotes axonal regeneration in the crushed optic nerve in vivo. These findings identify extracellular histones as a new class of nerve regeneration-inhibiting molecules within the injured CNS.
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Affiliation(s)
- Mustafa M Siddiq
- Department of Biological Sciences, Hunter College, City University of New York, New York, NY 10065, USA.,Department of Pharmacological Sciences and Institute for Systems Biomedicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Sari S Hannila
- Department of Biological Sciences, Hunter College, City University of New York, New York, NY 10065, USA.,Department of Human Anatomy and Cell Science, University of Manitoba, Winnipeg, Manitoba R3E 0J9, Canada
| | - Yana Zorina
- Department of Pharmacological Sciences and Institute for Systems Biomedicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA.,Gene Editing and Screening Core Facility, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Elena Nikulina
- Department of Biological Sciences, Hunter College, City University of New York, New York, NY 10065, USA.,Department of Physiology and Pharmacology, SUNY Downstate Health Science University, Brooklyn, NY 11203, USA
| | - Vera Rabinovich
- Department of Pharmacological Sciences and Institute for Systems Biomedicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Jianwei Hou
- Department of Biological Sciences, Hunter College, City University of New York, New York, NY 10065, USA
| | - Rumana Huq
- Department of Pharmacological Sciences and Institute for Systems Biomedicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Erica L Richman
- Department of Biological Sciences, Hunter College, City University of New York, New York, NY 10065, USA
| | - Rosa E Tolentino
- Department of Pharmacological Sciences and Institute for Systems Biomedicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Jens Hansen
- Department of Pharmacological Sciences and Institute for Systems Biomedicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | | | - Brian K Kwon
- International Collaboration on Repair Discoveries, University of British Columbia (UBC), Vancouver, BC, Canada
| | - Stella E Tsirka
- Department of Pharmacological Sciences, Renaissance School of Medicine at Stony Brook University, Stony Brook, NY 11794-8651, USA
| | - Ian Maze
- Department of Neuroscience and Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Robert Sebra
- Department of Genetics and Genomic Studies, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA.,Icahn Institute for Data Science and Genomic Technology, Black Family Stem Cell Institute, New York, NY 10029, USA.,Sema4, a Mount Sinai Venture, Stamford, CT, USA
| | - Kristin G Beaumont
- Department of Genetics and Genomic Studies, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA.,Icahn Institute for Data Science and Genomic Technology, Black Family Stem Cell Institute, New York, NY 10029, USA
| | - Carlos A Toro
- National Center for the Medical Consequences of Spinal Cord Injury, James J. Peters VA Medical Center, New York, NY 10468, USA.,Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Christopher P Cardozo
- National Center for the Medical Consequences of Spinal Cord Injury, James J. Peters VA Medical Center, New York, NY 10468, USA.,Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA.,Department of Rehabilitation Medicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Ravi Iyengar
- Department of Pharmacological Sciences and Institute for Systems Biomedicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Marie T Filbin
- Department of Biological Sciences, Hunter College, City University of New York, New York, NY 10065, USA
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Nikulina E, Gkioka V, Siddiq MM, Mellado W, Hilaire M, Cain CR, Hannila SS, Filbin MT. Myelin-associated glycoprotein inhibits neurite outgrowth through inactivation of the small GTPase Rap1. FEBS Lett 2020; 594:1389-1402. [PMID: 31985825 DOI: 10.1002/1873-3468.13740] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 01/08/2020] [Accepted: 01/09/2020] [Indexed: 11/05/2022]
Abstract
Rap1 is a small GTPase that has been implicated in dendritic development and plasticity. In this study, we investigated the role of Rap1 in axonal growth and its activation in response to neurotrophins and myelin-associated inhibitors. We report that Rap1 is activated by brain-derived neurotrophic factor and that this activation can be blocked by myelin-associated glycoprotein (MAG) or central nervous system myelin, which also induced increases in Rap1GAP1 levels. In addition, we demonstrate that adenoviral overexpression of Rap1 enhances neurite outgrowth in the presence of MAG and myelin, while inhibition of Rap1 activity through overexpression of Rap1GAP1 blocks neurite outgrowth. These findings suggest that Rap1GAP1 negatively regulates neurite outgrowth, making it a potential therapeutic target to promote axonal regeneration.
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Affiliation(s)
- Elena Nikulina
- Department of Biological Sciences, Hunter College, City University of New York, NY, USA
| | - Vasiliki Gkioka
- Department of Biological Sciences, Hunter College, City University of New York, NY, USA
| | - Mustafa M Siddiq
- Icahn Medical Institute 12-52, Pharmacology and Systems Therapeutics, Mount Sinai School of Medicine, New York, NY, USA
| | | | - Melissa Hilaire
- Department of Biological Sciences, Hunter College, City University of New York, NY, USA
| | - Christine R Cain
- Department of Biological Sciences, Hunter College, City University of New York, NY, USA
| | - Sari S Hannila
- Department of Human Anatomy and Cell Science, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada
| | - Marie T Filbin
- Department of Biological Sciences, Hunter College, City University of New York, NY, USA
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4
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Li H, Kuwajima T, Oakley D, Nikulina E, Hou J, Yang WS, Lowry ER, Lamas NJ, Amoroso MW, Croft GF, Hosur R, Wichterle H, Sebti S, Filbin MT, Stockwell B, Henderson CE. Protein Prenylation Constitutes an Endogenous Brake on Axonal Growth. Cell Rep 2016; 16:545-558. [PMID: 27373155 DOI: 10.1016/j.celrep.2016.06.013] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Revised: 01/31/2016] [Accepted: 05/28/2016] [Indexed: 01/11/2023] Open
Abstract
Suboptimal axonal regeneration contributes to the consequences of nervous system trauma and neurodegenerative disease, but the intrinsic mechanisms that regulate axon growth remain unclear. We screened 50,400 small molecules for their ability to promote axon outgrowth on inhibitory substrata. The most potent hits were the statins, which stimulated growth of all mouse- and human-patient-derived neurons tested, both in vitro and in vivo, as did combined inhibition of the protein prenylation enzymes farnesyltransferase (PFT) and geranylgeranyl transferase I (PGGT-1). Compensatory sprouting of motor axons may delay clinical onset of amyotrophic lateral sclerosis (ALS). Accordingly, elevated levels of PGGT1B, which would be predicted to reduce sprouting, were found in motor neurons of early- versus late-onset ALS patients postmortem. The mevalonate-prenylation pathway therefore constitutes an endogenous brake on axonal growth, and its inhibition provides a potential therapeutic approach to accelerate neuronal regeneration in humans.
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Affiliation(s)
- Hai Li
- Center for Motor Neuron Biology and Disease, Columbia Stem Cell Initiative, Columbia Translational Neuroscience Initiative, Columbia University, New York, NY 10032, USA; Department of Pathology and Cell Biology, Neurology, and Neuroscience, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
| | - Takaaki Kuwajima
- Center for Motor Neuron Biology and Disease, Columbia Stem Cell Initiative, Columbia Translational Neuroscience Initiative, Columbia University, New York, NY 10032, USA; Department of Pathology and Cell Biology, Neurology, and Neuroscience, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
| | - Derek Oakley
- Project A.L.S./Jenifer Estess Laboratory for Stem Cell Research, New York, NY 10032, USA
| | - Elena Nikulina
- Department of Biological Sciences, Hunter College, City University of New York, NY 10065, USA
| | - Jianwei Hou
- Department of Biological Sciences, Hunter College, City University of New York, NY 10065, USA
| | - Wan Seok Yang
- Center for Motor Neuron Biology and Disease, Columbia Stem Cell Initiative, Columbia Translational Neuroscience Initiative, Columbia University, New York, NY 10032, USA; Howard Hughes Medical Institute and Department of Biological Sciences and Department of Chemistry, Columbia University, New York, NY 10027, USA
| | - Emily Rhodes Lowry
- Project A.L.S./Jenifer Estess Laboratory for Stem Cell Research, New York, NY 10032, USA
| | - Nuno Jorge Lamas
- Department of Pathology and Cell Biology, Neurology, and Neuroscience, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA; Project A.L.S./Jenifer Estess Laboratory for Stem Cell Research, New York, NY 10032, USA; Life and Health Sciences Research Institute, School of Health Sciences, University of Minho, 4710-057 Braga, Minho, Portugal
| | | | - Gist F Croft
- Project A.L.S./Jenifer Estess Laboratory for Stem Cell Research, New York, NY 10032, USA
| | | | - Hynek Wichterle
- Center for Motor Neuron Biology and Disease, Columbia Stem Cell Initiative, Columbia Translational Neuroscience Initiative, Columbia University, New York, NY 10032, USA; Department of Pathology and Cell Biology, Neurology, and Neuroscience, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA; Project A.L.S./Jenifer Estess Laboratory for Stem Cell Research, New York, NY 10032, USA
| | - Said Sebti
- Moffitt Cancer Center and Research Institute, University of South Florida, Tampa, FL 33612, USA
| | - Marie T Filbin
- Department of Biological Sciences, Hunter College, City University of New York, NY 10065, USA
| | - Brent Stockwell
- Center for Motor Neuron Biology and Disease, Columbia Stem Cell Initiative, Columbia Translational Neuroscience Initiative, Columbia University, New York, NY 10032, USA; Howard Hughes Medical Institute and Department of Biological Sciences and Department of Chemistry, Columbia University, New York, NY 10027, USA
| | - Christopher E Henderson
- Center for Motor Neuron Biology and Disease, Columbia Stem Cell Initiative, Columbia Translational Neuroscience Initiative, Columbia University, New York, NY 10032, USA; Department of Rehabilitation and Regenerative Medicine, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA; Department of Pathology and Cell Biology, Neurology, and Neuroscience, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA; Project A.L.S./Jenifer Estess Laboratory for Stem Cell Research, New York, NY 10032, USA; Target ALS Foundation, New York, NY 10032, USA.
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5
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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6
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Siddiq MM, Hannila SS, Carmel JB, Bryson JB, Hou J, Nikulina E, Willis MR, Mellado W, Richman EL, Hilaire M, Hart RP, Filbin MT. Metallothionein-I/II Promotes Axonal Regeneration in the Central Nervous System. J Biol Chem 2015; 290:16343-56. [PMID: 25947372 DOI: 10.1074/jbc.m114.630574] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Indexed: 11/06/2022] Open
Abstract
The adult CNS does not spontaneously regenerate after injury, due in large part to myelin-associated inhibitors such as myelin-associated glycoprotein (MAG), Nogo-A, and oligodendrocyte-myelin glycoprotein. All three inhibitors can interact with either the Nogo receptor complex or paired immunoglobulin-like receptor B. A conditioning lesion of the sciatic nerve allows the central processes of dorsal root ganglion (DRG) neurons to spontaneously regenerate in vivo after a dorsal column lesion. After a conditioning lesion, DRG neurons are no longer inhibited by myelin, and this effect is cyclic AMP (cAMP)- and transcription-dependent. Using a microarray analysis, we identified several genes that are up-regulated both in adult DRGs after a conditioning lesion and in DRG neurons treated with cAMP analogues. One gene that was up-regulated under both conditions is metallothionein (MT)-I. We show here that treatment with two closely related isoforms of MT (MT-I/II) can overcome the inhibitory effects of both myelin and MAG for cortical, hippocampal, and DRG neurons. Intrathecal delivery of MT-I/II to adult DRGs also promotes neurite outgrowth in the presence of MAG. Adult DRGs from MT-I/II-deficient mice extend significantly shorter processes on MAG compared with wild-type DRG neurons, and regeneration of dorsal column axons does not occur after a conditioning lesion in MT-I/II-deficient mice. Furthermore, a single intravitreal injection of MT-I/II after optic nerve crush promotes axonal regeneration. Mechanistically, MT-I/II ability to overcome MAG-mediated inhibition is transcription-dependent, and MT-I/II can block the proteolytic activity of α-secretase and the activation of PKC and Rho in response to soluble MAG.
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Affiliation(s)
- Mustafa M Siddiq
- From the Department of Biological Sciences, Hunter College, City University of New York, New York 10065 and
| | - Sari S Hannila
- From the Department of Biological Sciences, Hunter College, City University of New York, New York 10065 and
| | - Jason B Carmel
- the W. M. Keck Center for Collaborative Neuroscience and Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, New Jersey 08854
| | - John B Bryson
- From the Department of Biological Sciences, Hunter College, City University of New York, New York 10065 and
| | - Jianwei Hou
- From the Department of Biological Sciences, Hunter College, City University of New York, New York 10065 and
| | - Elena Nikulina
- From the Department of Biological Sciences, Hunter College, City University of New York, New York 10065 and
| | - Matthew R Willis
- From the Department of Biological Sciences, Hunter College, City University of New York, New York 10065 and
| | - Wilfredo Mellado
- From the Department of Biological Sciences, Hunter College, City University of New York, New York 10065 and
| | - Erica L Richman
- From the Department of Biological Sciences, Hunter College, City University of New York, New York 10065 and
| | - Melissa Hilaire
- From the Department of Biological Sciences, Hunter College, City University of New York, New York 10065 and
| | - Ronald P Hart
- the W. M. Keck Center for Collaborative Neuroscience and Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, New Jersey 08854
| | - Marie T Filbin
- From the Department of Biological Sciences, Hunter College, City University of New York, New York 10065 and
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Wyatt LA, Filbin MT, Keirstead HS. PTEN inhibition enhances neurite outgrowth in human embryonic stem cell-derived neuronal progenitor cells. J Comp Neurol 2014; 522:2741-55. [PMID: 24610700 DOI: 10.1002/cne.23580] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Revised: 09/29/2013] [Accepted: 10/07/2013] [Indexed: 12/27/2022]
Abstract
We investigated the role of PTEN (phosphatase and tensin homolog deleted on chromosome 10) during neurite outgrowth of human embryonic stem cell (hESC)-derived neuronal progenitors. PTEN inhibits phosphoinositide 3-kinase (PI3K)/Akt signaling, a common and central outgrowth and survival pathway downstream of neuronal growth factors. It is known that PTEN inhibition, by either polymorphic mutation or gene deletion, can lead to the development of tumorigenesis (Stambolic et al., ; Tamura et al., ). However, temporary inhibition of PTEN, through pharmacological manipulation, could regulate signaling events such as the PI3K/Akt signaling pathway, leading to enhanced recovery of central nervous system (CNS) injury and disease. We demonstrate that pharmacological inhibition of PTEN in hESC-derived neuronal progenitors significantly increased neurite outgrowth in vitro in a dose- and time-dependent manner. Our results indicate that inhibition of PTEN augments neurite outgrowth beyond that of traditional methods such as elevation of intracellular cyclic adenosine monophosphate (cAMP) levels, and depends on upregulation of the PI3K/Akt signaling pathway and its downstream effectors, such as mammalian target of rapamycin (mTOR). PTEN inhibition also rescued neurite outgrowth over an inhibitory substrate in vitro. These findings indicate a remarkable impact on hESC-derived neuronal progenitor plasticity through PTEN inhibition. Overall, these findings identify a novel therapeutic strategy for neurite outgrowth in CNS injury and disease.
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Affiliation(s)
- Lindsey A Wyatt
- Department of Anatomy and Neurobiology, Sue and Bill Gross Stem Cell Research Center, Reeve-Irvine Research Center, School of Medicine, University of California at Irvine, Irvine, California, 92697-4292
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8
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Costa LM, Pereira JE, Filipe VM, Magalhães LG, Couto PA, Gonzalo-Orden JM, Raimondo S, Geuna S, Maurício AC, Nikulina E, Filbin MT, Varejão AS. Rolipram promotes functional recovery after contusive thoracic spinal cord injury in rats. Behav Brain Res 2013; 243:66-73. [DOI: 10.1016/j.bbr.2012.12.056] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2012] [Revised: 12/24/2012] [Accepted: 12/29/2012] [Indexed: 01/28/2023]
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Perdigoto AL, Chaudhry N, Barnes GN, Filbin MT, Carter BD. A novel role for PTEN in the inhibition of neurite outgrowth by myelin-associated glycoprotein in cortical neurons. Mol Cell Neurosci 2010; 46:235-44. [PMID: 20869442 DOI: 10.1016/j.mcn.2010.09.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2010] [Revised: 08/18/2010] [Accepted: 09/15/2010] [Indexed: 10/19/2022] Open
Abstract
Axonal regeneration in the central nervous system is prevented, in part, by inhibitory proteins expressed by myelin, including myelin-associated glycoprotein (MAG). Although injury to the corticospinal tract can result in permanent disability, little is known regarding the mechanisms by which MAG affects cortical neurons. Here, we demonstrate that cortical neurons plated on MAG expressing CHO cells, exhibit a striking reduction in process outgrowth. Interestingly, none of the receptors previously implicated in MAG signaling, including the p75 neurotrophin receptor or gangliosides, contributed significantly to MAG-mediated inhibition. However, blocking the small GTPase Rho or its downstream effector kinase, ROCK, partially reversed the effects of MAG on the neurons. In addition, we identified the lipid phosphatase PTEN as a mediator of MAG's inhibitory effects on neurite outgrowth. Knockdown or gene deletion of PTEN or overexpression of activated AKT in cortical neurons resulted in significant, although partial, rescue of neurite outgrowth on MAG-CHO cells. Moreover, MAG decreased the levels of phospho-Akt, suggesting that it activates PTEN in the neurons. Taken together, these results suggest a novel pathway activated by MAG in cortical neurons involving the PTEN/PI3K/AKT axis.
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Affiliation(s)
- Ana Luisa Perdigoto
- Department of Biochemistry and the Center for Molecular Neuroscience, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
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Kadoya K, Tsukada S, Lu P, Coppola G, Geschwind D, Filbin MT, Blesch A, Tuszynski MH. Combined intrinsic and extrinsic neuronal mechanisms facilitate bridging axonal regeneration one year after spinal cord injury. Neuron 2009; 64:165-72. [PMID: 19874785 DOI: 10.1016/j.neuron.2009.09.016] [Citation(s) in RCA: 173] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/24/2009] [Indexed: 02/07/2023]
Abstract
Despite advances in promoting axonal regeneration after acute spinal cord injury (SCI), elicitation of bridging axon regeneration after chronic SCI remains a formidable challenge. We report that combinatorial therapies administered 6 weeks, and as long as 15 months, after SCI promote axonal regeneration into and beyond a midcervical lesion site. Provision of peripheral nerve conditioning lesions, grafts of marrow stromal cells, and establishment of NT-3 gradients supports bridging regeneration. Controls receiving partial components of the full combination fail to exhibit bridging. Notably, intraneuronal molecular mechanisms recruited by delayed therapies mirror those of acute injury, including activation of transcriptional activators and regeneration-associated genes. Collectively, these findings provide evidence that regeneration is achievable at unprecedented postinjury time points.
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Affiliation(s)
- Ken Kadoya
- Department of Neurosciences, University of California, San Diego, La Jolla, CA 92093, USA
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11
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Abstract
Inhibitors of axonal regeneration in myelin are believed to be major contributors to the lack of regeneration in the adult CNS. Three of the four known myelin inhibitors, although very different structurally, interact with the same receptor, NgR. However, the absence of NgR has no effect on inhibition of neurite outgrowth in culture, and there is no improvement in CST regeneration in vivo. In a recent issue of Science, a second receptor for these myelin inhibitors was described, PirB, a receptor first described in the immune system. Will PirB be the answer to CST regeneration in vivo?
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Affiliation(s)
- Marie T Filbin
- Biology Department, Hunter College, 695 Park Avenue, New York, NY 10065, USA.
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12
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Spencer TK, Mellado W, Filbin MT. BDNF activates CaMKIV and PKA in parallel to block MAG-mediated inhibition of neurite outgrowth. Mol Cell Neurosci 2008; 38:110-6. [PMID: 18381242 DOI: 10.1016/j.mcn.2008.02.005] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2008] [Accepted: 02/13/2008] [Indexed: 12/12/2022] Open
Abstract
The environment of the adult CNS prevents axonal regeneration after injury. This inhibition of axonal regeneration can be blocked by elevating cAMP. Previously, we showed that the cAMP pathway can be activated via pre-treatment with neurotrophins and requires activation of several signaling pathways which converge at activation of the transcription factor, CREB. Here, we show that calcium/calmodulin-dependent kinase IV (CaMKIV) is necessary for the neurotrophin-induced phosphorylation of CREB and the block of myelin-mediated inhibition of axonal growth. Pharmacological inhibition of CaMKIV or over-expression of a dominant-negative mutant form of CaMKIV blocks the neurotrophin effect. Interestingly, CaMKIV activation is not necessary if cAMP levels is already elevated. Finally, calcium flux from intracellular stores is necessary for this CaMKIV signaling. These results demonstrate that CaMKIV is another player in the neurotrophin-induced signaling which leads to axonal regeneration and therefore, is a potential target for therapeutic intervention following injury to the adult CNS.
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Affiliation(s)
- Timothy K Spencer
- Department of Biological Sciences, Hunter College, City University of New York, New York, New York 10065, USA.
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13
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Cao Z, Qiu J, Domeniconi M, Hou J, Bryson JB, Mellado W, Filbin MT. The inhibition site on myelin-associated glycoprotein is within Ig-domain 5 and is distinct from the sialic acid binding site. J Neurosci 2007; 27:9146-54. [PMID: 17715351 PMCID: PMC6672207 DOI: 10.1523/jneurosci.2404-07.2007] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Myelin-associated glycoprotein (MAG) is a potent inhibitor of axonal regeneration. It contains five Ig-like domains and is a sialic binding protein. Previously, we showed that the sialic acid binding site on MAG maps to arginine 118 in Ig domain 1 (Kelm et al., 1994). However, sialic acid binding was neither necessary nor sufficient for MAG to bring about inhibition of neurite outgrowth. Consistent with this, we now map a distinct inhibition site on MAG to Ig domain 5 (Ig-5). We show that when a truncated form of MAG missing Ig domains 1 and 2 is expressed by Chinese hamster ovary (CHO) cells, it does not bind sialic acid, but still inhibits neurite outgrowth almost as effectively as full-length MAG. To determine whether the inhibition site mapped to Ig-3, Ig-4, or Ig-5, we made chimeric molecules of various combinations of these three MAG Ig domains fused to Ig domains from another Ig family member, sialoadhesin (Sn), which also binds to sialic acid in the same linkage as MAG. The MAG-Sn molecules were expressed in CHO cells and all contained five Ig domains and were able to bind sialic acid. However, only the chimeric molecules containing MAG Ig-5 inhibited neurite outgrowth. Furthermore, peptides corresponding to sequences in MAG Ig-5, but not Ig-4 or Sn Ig-5, are able to block inhibition of neurite outgrowth by both wild-type MAG and CNS myelin. We conclude that the inhibition site on MAG is carried by Ig domain 5 and that this site is distinct from the sialic-acid binding site.
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Affiliation(s)
- Zixuan Cao
- The Department of Biological Sciences, Hunter College, City University of New York, New York, New York 10021
| | - Jin Qiu
- The Department of Biological Sciences, Hunter College, City University of New York, New York, New York 10021
| | - Marco Domeniconi
- The Department of Biological Sciences, Hunter College, City University of New York, New York, New York 10021
| | - Jianwei Hou
- The Department of Biological Sciences, Hunter College, City University of New York, New York, New York 10021
| | - J. Barney Bryson
- The Department of Biological Sciences, Hunter College, City University of New York, New York, New York 10021
| | - Wilfredo Mellado
- The Department of Biological Sciences, Hunter College, City University of New York, New York, New York 10021
| | - Marie T. Filbin
- The Department of Biological Sciences, Hunter College, City University of New York, New York, New York 10021
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14
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Abstract
The failure of axons to regenerate after spinal cord injury remains one of the greatest challenges facing both medicine and neuroscience, but in the last 20 years there have been tremendous advances in the field of spinal cord injury repair. One of the most important of these has been the identification of inhibitory proteins in CNS myelin, and this has led to the development of strategies that will enable axons to overcome myelin inhibition. Elevation of intracellular cyclic AMP (cAMP) has been one of the most successful of these strategies, and in this review we examine how cAMP signaling promotes axonal regeneration in the CNS. Intracellular cAMP levels can be increased through a peripheral conditioning lesion, administration of cAMP analogues, priming with neurotrophins or treatment with the phosphodiesterase inhibitor rolipram, and each of these methods has been shown to overcome myelin inhibition both in vitro and in vivo. It is now known that the effects of cAMP are transcription dependent, and that cAMP-mediated activation of CREB leads to upregulated expression of genes such as arginase I and interleukin-6. The products of these genes have been shown to directly promote axonal regeneration, which raises the possibility that other cAMP-regulated genes could yield additional agents that would be beneficial in the treatment of spinal cord injury. Further study of these genes, in combination with human clinical trials of existing agents such as rolipram, would allow the therapeutic potential of cAMP to be fully realized.
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Affiliation(s)
| | - Marie T. Filbin
- Correspondence should be addressed to Dr. Marie T. Filbin at the above address.
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15
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Abstract
Numerous studies in the last two decades have resulted in significant progress in our understanding of the role of inhibitors on axonal regeneration and conditions that influence mature neurons to regrow in an inhibitory environment. These studies have revealed putative therapeutic targets and strategies to interfere in the inhibitory signaling cascade and promote axonal regeneration. Some agents that were successful in animal models are now being tested in human patients. All of these advances have raised hope of a cure for an injury that was once thought to be 'an ailment for which nothing is done' (Quote from Edwin Smith surgical papyrus, 1600BC).
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16
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Abstract
In the past decade there has been an explosion in our understanding, at the molecular level, of why axons in the adult, mammalian central nervous system (CNS) do not spontaneously regenerate while their younger counterparts do. Now a number of inhibitors of axonal regeneration have been described, some of the receptors they interact with to transduce the inhibitory signal are known, as are some of the steps in the signal transduction pathway that is responsible for inhibition. In addition, developmental changes in the environment and in the neurons themselves are also now better understood. This knowledge in turn reveals novel, putative sites for drug development and therapeutic intervention after injury to the brain and spinal cord. The challenge now is to determine which of these putative treatments are the most effective and if they would be better applied in combination rather than alone. In this review I will summarize what we have learnt about these molecules and how they signal. Importantly, I will also describe approaches that have been shown to block inhibitors and encourage regeneration in vivo. I will also speculate on what the differences are between the neonatal and adult CNS that allow the former to regenerate and the latter not to.
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Affiliation(s)
- Marie T Filbin
- Department of Biological Sciences, Hunter College, City University of New York, 695 Park Avenue, New York, NY 10021, USA.
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17
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Hannila SS, Siddiq MM, Filbin MT. Therapeutic Approaches to Promoting Axonal Regeneration in the Adult Mammalian Spinal Cord. International Review of Neurobiology 2007; 77:57-105. [PMID: 17178472 DOI: 10.1016/s0074-7742(06)77003-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Sari S Hannila
- Department of Biological Sciences, Hunter College, City University of New York, New York 10021, USA
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18
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19
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Cao Z, Gao Y, Bryson JB, Hou J, Chaudhry N, Siddiq M, Martinez J, Spencer T, Carmel J, Hart RB, Filbin MT. The cytokine interleukin-6 is sufficient but not necessary to mimic the peripheral conditioning lesion effect on axonal growth. J Neurosci 2006; 26:5565-73. [PMID: 16707807 PMCID: PMC6675293 DOI: 10.1523/jneurosci.0815-06.2006] [Citation(s) in RCA: 153] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Lesioning the peripheral branch of a dorsal root ganglion (DRG) neuron before injury of the central branch of the same neuron enables spontaneous regeneration of these spinal axons. This effect is cAMP and transcription dependent. Here, we show that the cytokine interleukin-6 (IL-6) is upregulated in DRG neurons after either a conditioning lesion or treatment with dibutyryl-cAMP. In culture, IL-6 allows neurons to grow in the presence of inhibitors of regeneration present in myelin. Importantly, intrathecal delivery of IL-6 to DRG neurons blocks inhibition by myelin both in vitro and in vivo, effectively mimicking the conditioning lesion. Blocking IL-6 signaling has no effect on the ability of cAMP to overcome myelin inhibitors. Consistent with this, IL-6-deficient mice respond to a conditioning lesion as effectively as wild-type mice. We conclude that IL-6 can mimic both the cAMP effect and the conditioning lesion effect but is not an essential component of either response.
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MESH Headings
- Animals
- Animals, Newborn
- Bucladesine/pharmacology
- CHO Cells
- Cells, Cultured
- Cricetinae
- Disease Models, Animal
- Female
- Ganglia, Spinal/cytology
- Ganglia, Spinal/drug effects
- Ganglia, Spinal/metabolism
- Growth Cones/drug effects
- Growth Cones/metabolism
- Growth Inhibitors/antagonists & inhibitors
- Growth Inhibitors/metabolism
- Interleukin-6/metabolism
- Interleukin-6/pharmacology
- Male
- Mice
- Mice, Knockout
- Myelin Proteins/antagonists & inhibitors
- Myelin Proteins/metabolism
- Nerve Regeneration/drug effects
- Nerve Regeneration/physiology
- Neurons, Afferent/cytology
- Neurons, Afferent/drug effects
- Neurons, Afferent/metabolism
- Peripheral Nerve Injuries
- Peripheral Nerves/cytology
- Peripheral Nerves/metabolism
- Rats
- Rats, Long-Evans
- Sciatic Neuropathy/drug therapy
- Sciatic Neuropathy/metabolism
- Sciatic Neuropathy/physiopathology
- Up-Regulation/drug effects
- Up-Regulation/physiology
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20
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Domeniconi M, Zampieri N, Spencer T, Hilaire M, Mellado W, Chao MV, Filbin MT. MAG Induces Regulated Intramembrane Proteolysis of the p75 Neurotrophin Receptor to Inhibit Neurite Outgrowth. Neuron 2005; 46:849-55. [PMID: 15953414 DOI: 10.1016/j.neuron.2005.05.029] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2004] [Revised: 12/12/2004] [Accepted: 05/31/2005] [Indexed: 12/16/2022]
Abstract
The three known inhibitors of axonal regeneration present in myelin--MAG, Nogo, and OMgp--all interact with the same receptor complex to effect inhibition via protein kinase C (PKC)-dependent activation of the small GTPase Rho. The transducing component of this receptor complex is the p75 neurotrophin receptor. Here we show that MAG binding to cerebellar neurons induces alpha- and then gamma-secretase proteolytic cleavage of p75, in a protein kinase C-dependent manner, and that this cleavage is necessary for both activation of Rho and inhibition of neurite outgrowth.
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Affiliation(s)
- Marco Domeniconi
- Biology Department, Hunter College, City University of New York, 695 Park Avenue, New York, New York 10021, USA
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21
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Abstract
The lack of axonal growth after injury in the adult central nervous system (CNS) is due to several factors including the formation of a glial scar, the absence of neurotrophic factors, the presence of growth-inhibitory molecules associated with myelin and the intrinsic growth-state of the neurons. To date, three inhibitors have been identified in myelin: Myelin-Associated Glycoprotein (MAG), Nogo-A, and Oligodendrocyte-Myelin glycoprotein (OMgp). In previous studies we reported that MAG inhibits axonal regeneration by high affinity interaction (K(D) 8 nM) with the Nogo66 receptor (NgR) and activation of a p75 neurotrophin receptor (p75NTR)-mediated signaling pathway. Similar to other axon guidance molecules, MAG is bifunctional. When cultured on MAG-expressing cells, dorsal root ganglia neurons (DRG) older than post-natal day 4 (PND4) extend neurites 50% shorter on average than when cultured on control cells. In contrast, MAG promotes neurite outgrowth from DRG neurons from animals younger than PND4. The response switch, which is also seen in retinal ganglia (RGC) and Raphe nucleus neurons, is concomitant with a developmental decrease in the endogenous neuronal cAMP levels. We report that artificially increasing cAMP levels in older neurons can alter their growth-state and induce axonal growth in the presence of myelin-associated inhibitors.
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Affiliation(s)
- Marco Domeniconi
- Hunter College of City University of New York, Department of Biological Sciences, 695 Park Avenue Room 807N, New York, NY 10021, USA
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22
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Gao Y, Deng K, Hou J, Bryson JB, Barco A, Nikulina E, Spencer T, Mellado W, Kandel ER, Filbin MT. Activated CREB is sufficient to overcome inhibitors in myelin and promote spinal axon regeneration in vivo. Neuron 2005; 44:609-21. [PMID: 15541310 DOI: 10.1016/j.neuron.2004.10.030] [Citation(s) in RCA: 264] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2003] [Revised: 06/07/2004] [Accepted: 10/14/2004] [Indexed: 10/25/2022]
Abstract
Inhibitors in myelin play a major role in preventing spontaneous axonal regeneration after CNS injury. Elevation of cAMP overcomes this inhibition, in a transcription-dependent manner, through the upregulation of Arginase I (Arg I) and increased synthesis of polyamines. Here, we show that the cAMP effect requires activation of the transcription factor cAMP response element binding protein (CREB) to overcome myelin inhibitors; a dominant-negative CREB abolishes the effect, and neurons expressing a constitutively active form of CREB are not inhibited. Activation of CREB is also required for cAMP to upregulate Arg I, and the ability of constitutively active CREB to overcome inhibition is blocked by an inhibitor of polyamine synthesis. Finally, expression of constitutively active CREB in DRG neurons is sufficient to promote regeneration of subsequently lesioned dorsal column axons. These results indicate that CREB plays a central role in overcoming myelin inhibitors and so encourages regeneration in vivo.
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Affiliation(s)
- Ying Gao
- Biology Department, Hunter College, City University of New York, 695 Park Avenue, New York, NY 10021, USA
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23
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Lu P, Yang H, Jones LL, Filbin MT, Tuszynski MH. Combinatorial therapy with neurotrophins and cAMP promotes axonal regeneration beyond sites of spinal cord injury. J Neurosci 2004; 24:6402-9. [PMID: 15254096 PMCID: PMC6729552 DOI: 10.1523/jneurosci.1492-04.2004] [Citation(s) in RCA: 302] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Previous attempts to promote regeneration after spinal cord injury have succeeded in stimulating axonal growth into or around lesion sites but rarely beyond them. We tested whether a combinatorial approach of stimulating the neuronal cell body with cAMP and the injured axon with neurotrophins would propel axonal growth into and beyond sites of spinal cord injury. A preconditioning stimulus to sensory neuronal cell bodies was delivered by injecting cAMP into the L4 dorsal root ganglion, and a postinjury stimulus to the injured axon was administered by injecting neurotrophin-3 (NT-3) within and beyond a cervical spinal cord lesion site grafted with autologous bone marrow stromal cells. One to 3 months later, long-projecting dorsal-column sensory axons regenerated into and beyond the lesion. Regeneration beyond the lesion did not occur after treatment with cAMP or NT-3 alone. Thus, clear axonal regeneration beyond spinal cord injury sites can be achieved by combinatorial approaches that stimulate both the neuronal soma and the axon, representing a major advance in strategies to enhance spinal cord repair.
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Affiliation(s)
- Paul Lu
- Department of Neurosciences, University of California at San Diego, La Jolla, California 92093-0626, USA
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24
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Nikulina E, Tidwell JL, Dai HN, Bregman BS, Filbin MT. The phosphodiesterase inhibitor rolipram delivered after a spinal cord lesion promotes axonal regeneration and functional recovery. Proc Natl Acad Sci U S A 2004; 101:8786-90. [PMID: 15173585 PMCID: PMC423273 DOI: 10.1073/pnas.0402595101] [Citation(s) in RCA: 255] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2004] [Indexed: 01/24/2023] Open
Abstract
Although there is no spontaneous regeneration of mammalian spinal axons after injury, they can be enticed to grow if cAMP is elevated in the neuronal cell bodies before the spinal axons are cut. Prophylactic injection of cAMP, however, is useless as therapy for spinal injuries. We now show that the phosphodiesterase 4 (PDE4) inhibitor rolipram (which readily crosses the blood-brain barrier) overcomes inhibitors of regeneration in myelin in culture and promotes regeneration in vivo. Two weeks after a hemisection lesion at C3/4, with embryonic spinal tissue implanted immediately at the lesion site, a 10-day delivery of rolipram results in considerable axon regrowth into the transplant and a significant improvement in motor function. Surprisingly, in rolipram-treated animals, there was also an attenuation of reactive gliosis. Hence, because rolipram promotes axon regeneration, attenuates the formation of the glial scar, and significantly enhances functional recovery, and because it is effective when delivered s.c., as well as post-injury, it is a strong candidate as a useful therapy subsequent to spinal cord injury.
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Affiliation(s)
- Elena Nikulina
- Biology Department, Hunter College, City University of New York, New York, NY 10024, USA
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25
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Pearse DD, Pereira FC, Marcillo AE, Bates ML, Berrocal YA, Filbin MT, Bunge MB. cAMP and Schwann cells promote axonal growth and functional recovery after spinal cord injury. Nat Med 2004; 10:610-6. [PMID: 15156204 DOI: 10.1038/nm1056] [Citation(s) in RCA: 529] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2004] [Accepted: 05/10/2004] [Indexed: 12/14/2022]
Abstract
Central neurons regenerate axons if a permissive environment is provided; after spinal cord injury, however, inhibitory molecules are present that make the local environment nonpermissive. A promising new strategy for inducing neurons to overcome inhibitory signals is to activate cAMP signaling. Here we show that cAMP levels fall in the rostral spinal cord, sensorimotor cortex and brainstem after spinal cord contusion. Inhibition of cAMP hydrolysis by the phosphodiesterase IV inhibitor rolipram prevents this decrease and when combined with Schwann cell grafts promotes significant supraspinal and proprioceptive axon sparing and myelination. Furthermore, combining rolipram with an injection of db-cAMP near the graft not only prevents the drop in cAMP levels but increases them above those in uninjured controls. This further enhances axonal sparing and myelination, promotes growth of serotonergic fibers into and beyond grafts, and significantly improves locomotion. These findings show that cAMP levels are key for protection, growth and myelination of injured CNS axons in vivo and recovery of function.
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Affiliation(s)
- Damien D Pearse
- The Miami Project to Cure Paralysis, University of Miami School of Medicine, 1095 NW 14th Terrace, Miami, Florida 33136, USA.
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26
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Abstract
Injury to the adult mammalian central nervous system (CNS) often results in permanent loss of sensory and motor function. This is due to the failure of injured axons to regenerate. The inhibitory nature of the CNS can be attributed to several factors, including formation of the glial scar, the presence of several molecules, associated with myelin, which inhibit axonal regrowth, and the intrinsic growth state of these neurons. Encouraging regeneration in the adult mammalian CNS therefore will require targeting one or all of these factors following injury. Here we illustrate recent work from our laboratory that identifies some of the signalling components involved in modulation of the intrinsic growth state of adult neurons. When activated, these signalling pathways can induce axonal regeneration in the presence of the myelin-associated inhibitors both in vitro and in vivo.
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Affiliation(s)
- Tim Spencer
- Department of Biological Sciences, Hunter College, The City University of New York, NY 10021, USA
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27
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Gao Y, Nikulina E, Mellado W, Filbin MT. Neurotrophins elevate cAMP to reach a threshold required to overcome inhibition by MAG through extracellular signal-regulated kinase-dependent inhibition of phosphodiesterase. J Neurosci 2003; 23:11770-7. [PMID: 14684879 PMCID: PMC6740960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/27/2023] Open
Abstract
Inhibitors of regeneration in myelin, such as myelin-associated glycoprotein (MAG), play an important role in preventing regeneration after CNS injury. Elevation of cAMP, either with dibutyryl-cAMP (db-cAMP) or by priming with a variety of neurotrophins, overcomes inhibition by MAG and myelin. However, activation of cAMP is not generally regarded as a signaling pathway for neurotrophins. Here we show that the NGF-like neurotrophins overcome inhibition by MAG by activating tyrosine kinase receptors. We also show that activation of extracellular signal-regulated kinase (Erk) by BDNF is required to overcome inhibition by MAG, and that activated Erk transiently inhibits phosphodiesterase 4 (PDE4), the enzyme that hydrolyzes cAMP. Inhibition of PDE4 then allows cAMP to increase and so initiates the pathway to overcome inhibition. Furthermore, we also show that basal levels of Erk activation and basal cAMP levels contribute to the effects of db-cAMP by pushing the combined levels of cAMP above a threshold required to overcome inhibition. Together, these results not only show how NGF-like neurotrophins can elevate cAMP and overcome inhibition but also point to a novel mechanism of cross talk in neurons from the Erk to the cAMP signaling pathways.
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Affiliation(s)
- Ying Gao
- Department of Biological Sciences, Hunter College, City University of New York, New York, New York 10021, USA
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28
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Affiliation(s)
- Marie T Filbin
- Department of Biological Sciences, Hunter College, City University of New York, 695 Park Avenue, New York, New York 10021, USA.
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29
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Abstract
The past year has yielded many insights and a few surprises in the field of axonal regeneration. The identification of oligodendrocyte-myelin glycoprotein as an inhibitor of axonal growth, and the discovery that the three major myelin-associated inhibitors of CNS regeneration share the same functional receptor, has launched a new wave of studies that aim to identify the signaling components of these inhibitory pathways. These findings also offer new avenues of research directed toward blocking possible therapeutic targets that inhibit regeneration and toward encouraging axonal regeneration in the CNS after injury.
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Affiliation(s)
- Timothy Spencer
- Department of Biological Sciences, Hunter College, The City University of New York, 695 Park Avenue, New York, NY 10021, USA
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30
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Affiliation(s)
- Jin Qiu
- Biology Department, Hunter College, City University of New York, 695 Park Avenue, New York, NY 10021, USA
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31
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Cai D, Deng K, Mellado W, Lee J, Ratan RR, Filbin MT. Arginase I and polyamines act downstream from cyclic AMP in overcoming inhibition of axonal growth MAG and myelin in vitro. Neuron 2002; 35:711-9. [PMID: 12194870 DOI: 10.1016/s0896-6273(02)00826-7] [Citation(s) in RCA: 253] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Elevation of cAMP can overcome myelin inhibitors to encourage regeneration of the CNS. We show that a consequence of elevated cAMP is the synthesis of polyamines, resulting from an up-regulation of Arginase I, a key enzyme in their synthesis. Inhibiting polyamine synthesis blocks the cAMP effect on regeneration. Either over-expression of Arginase I or exogenous polyamines can overcome inhibition by MAG and by myelin in general. While MAG/myelin support the growth of young DRG neurons, they become inhibitory as DRGs mature. Endogenous Arginase I levels are high in young DRGs but drop spontaneously at an age that coincides with the switch from promotion to inhibition by MAG/myelin. Over-expressing Arginase I in maturing DRGs blocks that switch. Arginase I and polyamines are more specific targets than cAMP for intervention to encourage regeneration after CNS injury.
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Affiliation(s)
- Dongming Cai
- Biology Department, Hunter College, City University of New York, 695 Park Avenue, New York, NY 10024, USA
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32
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Abstract
Myelin inhibitors, including MAG, are major impediments to CNS regeneration. However, CNS axons of DRGs regenerate if the peripheral branch of these neurons is lesioned first. We show that 1 day post-peripheral-lesion, DRG-cAMP levels triple and MAG/myelin no longer inhibit growth, an effect that is PKA dependent. By 1 week post-lesion, DRG-cAMP returns to control, but growth on MAG/myelin improves and is now PKA independent. Inhibiting PKA in vivo blocks the post-lesion growth on MAG/myelin at 1 day and attenuates it at 1 week. Alone, injection of db-cAMP into the DRG mimics completely a conditioning lesion as DRGs grow on MAG/myelin, initially, in a PKA-dependent manner that becomes PKA independent. Importantly, DRG injection of db-cAMP results in extensive regeneration of dorsal column axons lesioned 1 week later. These results may be relevant to developing therapies for spinal cord injury.
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Affiliation(s)
- Jin Qiu
- Biology Department, Hunter College, City University of New York, 695 Park Avenue, New York, NY 10021, USA
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Tang S, Qiu J, Nikulina E, Filbin MT. Soluble myelin-associated glycoprotein released from damaged white matter inhibits axonal regeneration. Mol Cell Neurosci 2001; 18:259-69. [PMID: 11591127 DOI: 10.1006/mcne.2001.1020] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The adult, mammalian CNS does not regenerate after injury largely because of a glial scar and inhibitors of regeneration in myelin. To date, two myelin inhibitors, myelin-associated glycoprotein (MAG) and Nogo, both transmembrane proteins, have been identified. No secreted inhibitors of regeneration have been described. However, a proteolytic fragment of MAG (dMAG), consisting of the entire extracellular domain, is readily released from myelin and is found in vivo. Here, we show, first, that a soluble, chimeric form of MAG (MAG-Fc), when secreted from CHO cells in a collagen gel and hence in the absence of a fixed substrate, inhibits/deflects neurite outgrowth from P6 dorsal root ganglion (DRG) neurons. This inhibition was blocked when a MAG monoclonal antibody was included in the gel and a control chimera sialoadhesin-Fc (Sn-Fc), which, like MAG, binds neurons in a sialic acid-dependent manner but does not inhibit axonal growth, had no effect. Using the same assay system we showed that factors secreted from damaged white matter inhibited/deflected neurite outgrowth. This inhibition was neutralized when a MAG monoclonal antibody was included in the gel and there was no inhibition when white matter from a MAG knockout mouse was used. Factors secreted from damaged white matter from wild-type mice had no effect on neurite outgrowth from E18 DRG neurons. These results show that factors secreted from damaged white matter inhibit axonal regeneration and that the majority of inhibitory activity can be accounted for by dMAG. Thus, released dMAG is likely to play an important role in preventing regeneration, immediately after injury before the glial scar forms.
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Affiliation(s)
- S Tang
- Biology Department, Hunter College, 695 Park Avenue, New York, New York, 10021, USA
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Cai D, Qiu J, Cao Z, McAtee M, Bregman BS, Filbin MT. Neuronal cyclic AMP controls the developmental loss in ability of axons to regenerate. J Neurosci 2001; 21:4731-9. [PMID: 11425900 PMCID: PMC6762375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2001] [Revised: 03/21/2001] [Accepted: 04/17/2001] [Indexed: 02/20/2023] Open
Abstract
Unlike neonatal axons, mammalian adult axons do not regenerate after injury. Likewise, myelin, a major factor in preventing regeneration in the adult, inhibits regeneration from older but not younger neurons. Identification of the molecular events responsible for this developmental loss of regenerative capacity is believed key to devising strategies to encourage regeneration in adults after injury. Here, we report that the endogenous levels of the cyclic nucleotide, cAMP, are dramatically higher in young neurons in which axonal growth is promoted both by myelin in general and by a specific myelin component, myelin-associated glycoprotein (MAG), than in the same types of neurons that, when older, are inhibited by myelin-MAG. Inhibiting a downstream effector of cAMP [protein kinase A (PKA)] prevents myelin-MAG promotion from young neurons, and elevating cAMP blocks myelin-MAG inhibition of neurite outgrowth in older neurons. Importantly, developmental plasticity of spinal tract axons in neonatal rat pups in vivo is dramatically reduced by inhibition of PKA. Thus, the switch from promotion to inhibition by myelin-MAG, which marks the developmental loss of regenerative capacity, is mediated by a developmentally regulated decrease in endogenous neuronal cAMP levels.
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Affiliation(s)
- D Cai
- Department of Biological Sciences, Hunter College, City University of New York, New York, New York 10021, USA
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Lumsden A, Coutinho A, Hazan J, Schubert F, Mayford M, Hamann S, Reber PJ, Häusser M, Murthy VN, Wood JN, Bredt DS, Filbin MT, Qiu J, Chafee M, Merchant H, Ashe J, Goodwin S, Kyriacou B, Kempermann G, Winkler J. Neurobiology. Curr Opin Neurobiol 2001. [DOI: 10.1016/s0959-4388(00)00187-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Lumsden A, Chapman S, Schubert F, Toole L, Mayford M, Hamann S, Reber PJ, Häusser M, Murthy VN, Wood JN, Liman ER, Filbin MT, Qiu J, Ashe J, Chafee M, Goodwin S, Kyriacou B, Kempermann G, Winkler J. Neurobiology. Curr Opin Neurobiol 2001; 11:1-9. [PMID: 11179863 DOI: 10.1016/s0959-4388(00)00185-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- A Lumsden
- King's College London, Guy's Hospital, London, UK
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Previtali SC, Quattrini A, Fasolini M, Panzeri MC, Villa A, Filbin MT, Li W, Chiu SY, Messing A, Wrabetz L, Feltri ML. Epitope-tagged P(0) glycoprotein causes Charcot-Marie-Tooth-like neuropathy in transgenic mice. J Cell Biol 2000; 151:1035-46. [PMID: 11086005 PMCID: PMC2174348 DOI: 10.1083/jcb.151.5.1035] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In peripheral nerve myelin, the intraperiod line results from compaction of the extracellular space due to homophilic adhesion between extracellular domains (ECD) of the protein zero (P(0)) glycoprotein. Point mutations in this region of P(0) cause human hereditary demyelinating neuropathies such as Charcot-Marie-Tooth. We describe transgenic mice expressing a full-length P(0) modified in the ECD with a myc epitope tag. The presence of the myc sequence caused a dysmyelinating peripheral neuropathy similar to two distinct subtypes of Charcot-Marie-Tooth, with hypomyelination, altered intraperiod lines, and tomacula (thickened myelin). The tagged protein was incorporated into myelin and was associated with the morphological abnormalities. In vivo and in vitro experiments showed that P(0)myc retained partial adhesive function, and suggested that the transgene inhibits P(0)-mediated adhesion in a dominant-negative fashion. These mice suggest new mechanisms underlying both the pathogenesis of P(0) ECD mutants and the normal interactions of P(0) in the myelin sheath.
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Affiliation(s)
- S C Previtali
- Department of Neurology and Department of Biological and Technological Research (DIBIT), San Raffaele Scientific Institute, 20132 Milan, Italy
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Lumsden A, Chapman S, Coutinho A, Gilthorpe J, Halilagic A, Shubert F, Wingate R, Mayford M, Hamann S, Reber PJ, Häusser M, Murthy VN, Wood JN, Qiu J, Filbin MT, Ashe J, Chafee M, El Manira A, Goodwin S, Kyriacou B, Brandon EP, Gage FH, Kempermann G, Winkler J. Neurobiology. Curr Opin Neurobiol 2000. [DOI: 10.1016/s0959-4388(00)00106-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Abstract
The extracellular domains of myelin Po protein interact homophilically and hence hold myelin compact at the intraperiod line. The cytoplasmic domain of Po, however, can also affect the interactions of its extracellular sequences. Po is acylated, mostly with palmitic acid, at Cys 153, just at the transmembrane:cytoplasmic domain interface. Here we show that Po mutated at Cys 153 to alanine (C153A), is not acylated and is not adhesive. Like wild-type Po, C153A Po clusters within the membrane and seems to interact with the cytoskeleton. On the other hand, the rate of turnover of C153A Po in transfected Chinese hamster ovary cells is almost 4 times faster than wild-type Po. The increased instability of C153A Po compared to wild-type Po may account for its loss of adhesion.
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Affiliation(s)
- Y Gao
- Biology Department, Hunter College, The City University of New York, New York 10021, USA
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Lumsden A, Chapman S, Jungbluth S, Bell E, Coutinho A, Costandi M, Adams N, Dutton R, Hamann S, Reber PJ, Häusser M, Murthy VN, Wood JN, Assad JA, Liman ER, Sheng M, Filbin MT, Qiu J, Ashe J, Chafee M, El Manira A, Goodwin S, Kyriacou B, Brandon EP, Gage FH. Neurobiology. Curr Opin Neurobiol 2000. [DOI: 10.1016/s0959-4388(00)00102-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Abstract
Myelin is a potent inhibitor of axon regeneration, but has been viewed as just one of many factors that prevent regeneration after injury. So it comes as a surprise that immunization against myelin has been found to allow extensive axon regeneration after injury, without apparent autoimmune-induced demyelination.
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Affiliation(s)
- M T Filbin
- Department of Biology, Hunter College of the City University of New York, New York 10021, USA.
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Qiu J, Cai D, Filbin MT. Glial inhibition of nerve regeneration in the mature mammalian CNS. Glia 2000; 29:166-74. [PMID: 10625335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Abstract
The lack of axonal regeneration in the adult mammalian CNS is due to both unfavorable environmental glial factors and the intrinsic neuronal state. Inhibitors associated with myelin and the glial scar have been extensively studies and it has been shown that neutralizing at least some of the inhibitors can lead to improved growth. Meanwhile, important advances have also been made towards our understanding of the neuronal intrinsic state, particularly the intracellular levels of cyclic nucleotide, that influence the capacity of mature CNS neurons to initiate and maintain a regrowth response. It is well recognized that successful regeneration may only be achieved by application of a combination of strategies that both block glial inhibitors and enhance the intrinsic neuronal growth capacity.
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Affiliation(s)
- J Qiu
- Biology Department, Hunter College of CUNY, New York, New York 10021, USA
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Sheng M, Qiu J, Filbin MT, Lumsden A, Zeltser L, Chapman S, Schubert F, Gilthorpe J, Wingate R, Mayford M, Knowlton B, Jackson S, Häusser M, Murthy VN, Wood JN, Assad JA, Liman ER, Ashe J, El Manira A, Brandon EP, Gage FH. Neurobiology. Curr Opin Neurobiol 1999. [DOI: 10.1016/s0959-4388(99)00001-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Filbin MT, Zhang K, Li W, Gao Y. Characterization of the effect on adhesion of different mutations in myelin P0 protein. Ann N Y Acad Sci 1999; 883:160-7. [PMID: 10586242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/14/2023]
Abstract
Table 1 summarizes the results obtained from expressing in CHO cells C21A P0 and N93A P0 alone, and each with wild-type P0. As can be seen, each of these mutated proteins reach the cell surface when expressed alone, but neither is adhesive. Finally, when each of these mutated P0 molecules is expressed with the wild-type P0, wild-type P0 is no longer adhesive. Therefore, both C21A Po and N93A P0 each have a dominant negative effect on adhesion of wild-type P0. This approach to address the functional consequences of mutations in P0 can now be used to assess the effects of different mutations associated with CMT1B.
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Affiliation(s)
- M T Filbin
- Department of Biological Sciences, Hunter College of CUNY, New York 10021, USA.
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Affiliation(s)
- M T Filbin
- Department of Biological Sciences, Hunter College of the City University of New York, New York 10021, USA
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Abstract
Myelin-associated glycoprotein (MAG) is a potent inhibitor of axonal regeneration and also, depending on the age and type of neuron, can promote axonal growth. In addition, MAG influences stability of both myelin and the axon in the intact, mature nervous system. The identity of the neuron/axonal MAG-binding receptor responsible for effecting these responses is not known. Here we show that a soluble, chimeric form of MAG, MAG-Fc, can bind to the neuronal cell body and neurites equally well, in a sialic acid-dependent manner. Importantly, MAG-Fc specifically precipitates a number of surface proteins from post-natal cerebellar, dorsal root ganglion (DRG) and PC12 neurons. These proteins are not precipitated by a control Fc-containing chimera and are not apparent when a MAG antibody is included in the precipitation mix as a competitive inhibitor. Based on molecular weight, two prominent proteins of 190 and 250 kD are precipitated from all three neuron types. The 190 kD protein is a sialoglycoprotein, since it is not apparent in the precipitate from neurons which have been desialylated. Other proteins are precipitated but are less abundant and are different for each type of neuron. One or more of these proteins is/are likely to be the functional MAG receptor.
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Affiliation(s)
- M E De Bellard
- Biology Department, Hunter College of the City University of New York, New York 10021, USA
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Lumsden A, Ellies D, Tucker A, Dixon M, Schubert F, Bell E, Collignon J, Jungbluth S, Adams N, Knowlton B, Häusser M, Murthy VN, Wood JN, Assad JA, Liman ER, Sheng M, Filbin MT, Ashe J, El Manira A, Brandon EP, Gage FH. Neurobiology. Curr Opin Neurobiol 1999. [DOI: 10.1016/s0959-4388(99)80001-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Cai D, Shen Y, De Bellard M, Tang S, Filbin MT. Prior exposure to neurotrophins blocks inhibition of axonal regeneration by MAG and myelin via a cAMP-dependent mechanism. Neuron 1999; 22:89-101. [PMID: 10027292 DOI: 10.1016/s0896-6273(00)80681-9] [Citation(s) in RCA: 443] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
MAG is a potent inhibitor of axonal regeneration. Here, inhibition by MAG, and myelin in general, is blocked if neurons are exposed to neurotrophins before encountering the inhibitor; priming cerebellar neurons with BDNF or GDNF, but not NGF, or priming DRG neurons with any of these neurotrophins blocks inhibition by MAG/myelin. Dibutyryl cAMP also overcomes inhibition by MAG/myelin, and cAMP is elevated by neurotrophins. A PKA inhibitor present during priming abrogates the block of inhibition. Finally, if neurons are exposed to MAG/myelin and neurotrophins simultaneously, but with the Gi protein inhibitor, inhibition is blocked. We suggest that priming neurons with particular neurotrophins elevates cAMP and activates PKA, which blocks subsequent inhibition of regeneration and that priming is required because MAG/myelin activates a Gi protein, which blocks increases in cAMP. This is important for encouraging axons to regrow in vivo.
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Affiliation(s)
- D Cai
- Biology Department, Hunter College of the City University of New York, New York 10021, USA
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