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Hausott B, Glueckert R, Schrott-Fischer A, Klimaschewski L. Signal Transduction Regulators in Axonal Regeneration. Cells 2022; 11:cells11091537. [PMID: 35563843 PMCID: PMC9104247 DOI: 10.3390/cells11091537] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 04/27/2022] [Accepted: 04/28/2022] [Indexed: 11/16/2022] Open
Abstract
Intracellular signal transduction in response to growth factor receptor activation is a fundamental process during the regeneration of the nervous system. In this context, intracellular inhibitors of neuronal growth factor signaling have become of great interest in the recent years. Among them are the prominent signal transduction regulators Sprouty (SPRY) and phosphatase and tensin homolog deleted on chromosome 10 (PTEN), which interfere with major signaling pathways such as extracellular signal-regulated kinase (ERK) or phosphoinositide 3-kinase (PI3K)/Akt in neurons and glial cells. Furthermore, SPRY and PTEN are themselves tightly regulated by ubiquitin ligases such as c-casitas b-lineage lymphoma (c-CBL) or neural precursor cell expressed developmentally down-regulated protein 4 (NEDD4) and by different microRNAs (miRs) including miR-21 and miR-222. SPRY, PTEN and their intracellular regulators play an important role in the developing and the lesioned adult central and peripheral nervous system. This review will focus on the effects of SPRY and PTEN as well as their regulators in various experimental models of axonal regeneration in vitro and in vivo. Targeting these signal transduction regulators in the nervous system holds great promise for the treatment of neurological injuries in the future.
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Affiliation(s)
- Barbara Hausott
- Institute of Neuroanatomy, Medical University Innsbruck, 6020 Innsbruck, Austria;
- Correspondence:
| | - Rudolf Glueckert
- Department of Otorhinolaryngology, Medical University Innsbruck, 6020 Innsbruck, Austria; (R.G.); (A.S.-F.)
| | - Anneliese Schrott-Fischer
- Department of Otorhinolaryngology, Medical University Innsbruck, 6020 Innsbruck, Austria; (R.G.); (A.S.-F.)
| | - Lars Klimaschewski
- Institute of Neuroanatomy, Medical University Innsbruck, 6020 Innsbruck, Austria;
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Hausott B, Klimaschewski L. Promotion of Peripheral Nerve Regeneration by Stimulation of the Extracellular Signal-Regulated Kinase (ERK) Pathway. Anat Rec (Hoboken) 2019; 302:1261-1267. [PMID: 30951263 PMCID: PMC6767477 DOI: 10.1002/ar.24126] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Revised: 12/06/2018] [Accepted: 01/11/2019] [Indexed: 12/19/2022]
Abstract
Peripherally projecting neurons undergo significant morphological changes during development and regeneration. This neuroplasticity is controlled by growth factors, which bind specific membrane bound kinase receptors that in turn activate two major intracellular signal transduction cascades. Besides the PI3 kinase/AKT pathway, activated extracellular signal‐regulated kinase (ERK) plays a key role in regulating the mode and speed of peripheral axon outgrowth in the adult stage. Cell culture studies and animal models revealed that ERK signaling is mainly involved in elongative axon growth in vitro and long‐distance nerve regeneration in vivo. Here, we review ERK dependent morphological plasticity in adult peripheral neurons and evaluate the therapeutic potential of interfering with regulators of ERK signaling to promote nerve regeneration. Anat Rec, 302:1261–1267, 2019. © 2019 Wiley Periodicals, Inc.
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Affiliation(s)
- Barbara Hausott
- Department of Anatomy, Histology and Embryology, Division of Neuroanatomy, Medical University Innsbruck, Innsbruck, Austria
| | - Lars Klimaschewski
- Department of Anatomy, Histology and Embryology, Division of Neuroanatomy, Medical University Innsbruck, Innsbruck, Austria
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3
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Pannese E. Biology and Pathology of Perineuronal Satellite Cells in Sensory Ganglia. BIOLOGY AND PATHOLOGY OF PERINEURONAL SATELLITE CELLS IN SENSORY GANGLIA 2018. [DOI: 10.1007/978-3-319-60140-3_1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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4
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Huang HT, Sun ZG, Liu HW, Ma JT, Hu M. ERK/MAPK and PI3K/AKT signal channels simultaneously activated in nerve cell and axon after facial nerve injury. Saudi J Biol Sci 2017; 24:1853-1858. [PMID: 29551935 PMCID: PMC5851917 DOI: 10.1016/j.sjbs.2017.11.027] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Revised: 11/09/2017] [Accepted: 11/09/2017] [Indexed: 01/05/2023] Open
Abstract
Background The in-vitro study indicated that ERK/MAPK and PI3K/AKT signal channels may play an important role in reparative regeneration process after peripheral nerve injury. But, relevant in-vivo study was infrequent. In particular, there has been no report on simultaneous activation of ERK/MAPK and PI3K/AKT signal channels in facial nerve cell and axon after facial nerve injury. Results The expression of P-ERK enhanced in nerve cells at the injury side on the 1 d after the rat facial nerve was cut and kept on a higher level until 14 d, but decreased on 28 d. The expression of P-AKT enhanced in nerve cells at the injury side on 1 d after injury, and kept on a higher level until 28 d. The expression of P-ERK enhanced at the near and far sections of the injured axon on 1 d, then increased gradually and reached the maximum on 7 d, but decreased on 14 d, until down to the level before the injury on 28 d. The expression of P-AKT obviously enhanced in the injured axon on 1 d, especially in the axon of the rear section, but decreased in the axon of the rear section on 7 d, while the expression of axon in the far section increased to the maximum and kept on till 14 d. On 28 d, the expression of P-AKT decreased in both rear and far sections of the axon. Conclusion The facial nerve simultaneously activated ERK/MAPK and PI3K/AKT signal channels in facial nerve cells and axons after the cut injury, but the expression levels of P-ERK and P-AKT varied as the function of the time. In particular, they were quite different in axon of the far section. It has been speculated that two signal channels might have different functions after nerve injury. However, their specific regulating effects should still be testified by further studies in regenerative process of peripheral nerve injury.
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Affiliation(s)
- Hai-Tao Huang
- Department of Stomatology, Chinese PLA General Hospital, Beijing 100853, China.,Department of Maxillofacial Surgery, The 1st Affiliated Hospital of Dalian Medical University, Dalian 116011, China
| | - Zhi-Gang Sun
- Department of Pathology, The 1st Affiliated Hospital of Dalian Medical University, Dalian 116011, China
| | - Hua-Wei Liu
- Department of Stomatology, Chinese PLA General Hospital, Beijing 100853, China
| | - Jun-Tao Ma
- Department of Stomatology, Chinese PLA General Hospital, Beijing 100853, China.,Department of Maxillofacial Surgery, The 1st Affiliated Hospital of Dalian Medical University, Dalian 116011, China
| | - Min Hu
- Department of Stomatology, Chinese PLA General Hospital, Beijing 100853, China
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5
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Huang H, Liu H, Yan R, Hu M. PI3K/Akt and ERK/MAPK Signaling Promote Different Aspects of Neuron Survival and Axonal Regrowth Following Rat Facial Nerve Axotomy. Neurochem Res 2017; 42:3515-3524. [DOI: 10.1007/s11064-017-2399-1] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Revised: 07/27/2017] [Accepted: 09/02/2017] [Indexed: 11/28/2022]
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6
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Yang T, Massa SM, Tran KC, Simmons DA, Rajadas J, Zeng AY, Jang T, Carsanaro S, Longo FM. A small molecule TrkB/TrkC neurotrophin receptor co-activator with distinctive effects on neuronal survival and process outgrowth. Neuropharmacology 2016; 110:343-361. [PMID: 27334657 DOI: 10.1016/j.neuropharm.2016.06.015] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Revised: 05/28/2016] [Accepted: 06/16/2016] [Indexed: 01/16/2023]
Abstract
Neurotrophin (NT) receptors are coupled to numerous signaling networks that play critical roles in neuronal survival and plasticity. Several non-peptide small molecule ligands have recently been reported that bind to and activate specific tropomyosin-receptor kinase (Trk) NT receptors, stimulate their downstream signaling, and cause biologic effects similar to, though not completely overlapping, those of the native NT ligands. Here, in silico screening, coupled with low-throughput neuronal survival screening, identified a compound, LM22B-10, that, unlike prior small molecule Trk ligands, binds to and activates TrkB as well as TrkC. LM22B-10 increased cell survival and strongly accelerated neurite outgrowth, superseding the effects of brain-derived neurotrophic factor (BDNF), NT-3 or the two combined. Additionally, unlike the NTs, LM22B-10 supported substantial early neurite outgrowth in the presence of inhibiting glycoproteins. Examination of the mechanisms of these actions suggested contributions of the activation of both Trks and differential interactions with p75(NTR), as well as a requirement for involvement of the Trk extracellular domain. In aged mice, LM22B-10 activated hippocampal and striatal TrkB and TrkC, and their downstream signaling, and increased hippocampal dendritic spine density. Thus, LM22B-10 may constitute a new tool for the study of TrkB and TrkC signaling and their interactions with p75(NTR), and provides groundwork for the development of ligands that stimulate unique combinations of Trk receptors and activity patterns for application to selected neuronal populations and deficits present in various disease states.
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Affiliation(s)
- Tao Yang
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Stephen M Massa
- Department of Neurology and Laboratory for Computational Neurochemistry and Drug Discovery, San Francisco Veterans Affairs Medical Center, and Dept. of Neurology, University of California, San Francisco, CA 94121, USA.
| | - Kevin C Tran
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Danielle A Simmons
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Jayakumar Rajadas
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Anne Y Zeng
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Taichang Jang
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Sara Carsanaro
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Frank M Longo
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA.
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Marvaldi L, Thongrong S, Kozłowska A, Irschick R, Pritz CO, Bäumer B, Ronchi G, Geuna S, Hausott B, Klimaschewski L. Enhanced axon outgrowth and improved long-distance axon regeneration in sprouty2 deficient mice. Dev Neurobiol 2014; 75:217-31. [PMID: 25104556 DOI: 10.1002/dneu.22224] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Revised: 07/16/2014] [Accepted: 08/06/2014] [Indexed: 12/31/2022]
Abstract
Sprouty (Spry) proteins are negative feedback inhibitors of receptor tyrosine kinase signaling. Downregulation of Spry2 has been demonstrated to promote elongative axon growth of cultured peripheral and central neurons. Here, we analyzed Spry2 global knockout mice with respect to axon outgrowth in vitro and peripheral axon regeneration in vivo. Neurons dissociated from adult Spry2 deficient sensory ganglia revealed stronger extracellular signal-regulated kinase activation and enhanced axon outgrowth. Prominent axon elongation was observed in heterozygous Spry2(+/-) neuron cultures, whereas homozygous Spry2(-/-) neurons predominantly exhibited a branching phenotype. Following sciatic nerve crush, Spry2(+/-) mice recovered faster in motor but not sensory testing paradigms (Spry2(-/-) mice did not tolerate anesthesia required for nerve surgery). We attribute the improvement in the rotarod test to higher numbers of myelinated fibers in the regenerating sciatic nerve, higher densities of motor endplates in hind limb muscles and increased levels of GAP-43 mRNA, a downstream target of extracellular regulated kinase signaling. Conversely, homozygous Spry2(-/-) mice revealed enhanced mechanosensory function (von Frey's test) that was accompanied by an increased innervation of the epidermis, elevated numbers of nonmyelinated axons and more IB4-positive neurons in dorsal root ganglia. The present results corroborate the functional significance of receptor tyrosine kinase signaling inhibitors for axon outgrowth during development and nerve regeneration and propose Spry2 as a novel potential target for pharmacological inhibition to accelerate long-distance axon regeneration in injured peripheral nerves.
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Affiliation(s)
- Letizia Marvaldi
- Division of Neuroanatomy, Department of Anatomy and Histology, Medical University Innsbruck, 6020, Innsbruck, Austria
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Sharma R, Wu X, Rhodes SD, Chen S, He Y, Yuan J, Li J, Yang X, Li X, Jiang L, Kim ET, Stevenson DA, Viskochil D, Xu M, Yang FC. Hyperactive Ras/MAPK signaling is critical for tibial nonunion fracture in neurofibromin-deficient mice. Hum Mol Genet 2013; 22:4818-28. [PMID: 23863460 DOI: 10.1093/hmg/ddt333] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Neurofibromatosis type 1 (NF1) is a common genetic disorder affecting 1 in 3500 individuals. Patients with NF1 are predisposed to debilitating skeletal manifestations, including osteopenia/osteoporosis and long bone pseudarthrosis (nonunion fracture). Hyperactivation of the Ras/mitogen-activated protein kinase (MAPK) pathway in NF1 is known to underlie aberrant proliferation and differentiation in cell lineages, including osteoclast progenitors and mesenchymal stem cells (MSCs) also known as osteoblast progenitors (pro-OBLs). Our current study demonstrates the hyper Ras/MAPK as a critical pathway underlying the pathogenesis of NF1-associated fracture repair deficits. Nf1-deficient pro-OBLs exhibit Ras/MAPK hyperactivation. Introduction of the NF1 GTPase activating-related domain (NF1 GAP-related domain) in vitro is sufficient to rescue hyper Ras activity and enhance osteoblast (OBL) differentiation in Nf1(-/-) pro-OBLs and NF1 human (h) MSCs cultured from NF1 patients with skeletal abnormalities, including pseudarthrosis or scoliosis. Pharmacologic inhibition of mitogen-activated protein kinase kinase (MEK) signaling with PD98059 partially rescues aberrant Erk activation while enhancing OBL differentiation and expression of OBL markers, osterix and osteocalcin, in Nf1-deficient murine pro-OBLs. Similarly, MEK inhibition enhances OBL differentiation of hMSCs. In addition, PD98059 rescues aberrant osteoclast maturation in Nf1 haploinsufficient bone marrow mononuclear cells (BMMNCs). Importantly, MEK inhibitor significantly improves fracture healing in an NF1 murine model, Col2.3Cre;Nf1(flox/-). Collectively, these data indicate the Ras/MAPK cascade as a critical pathway in the pathogenesis of bone loss and pseudarthrosis related to NF1 mutations. These studies provide evidence for targeting the MAPK pathway to improve bone mass and treat pseudarthrosis in NF1.
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Klimaschewski L, Hausott B, Angelov DN. The pros and cons of growth factors and cytokines in peripheral axon regeneration. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2013; 108:137-71. [PMID: 24083434 DOI: 10.1016/b978-0-12-410499-0.00006-x] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Injury to a peripheral nerve induces a complex cellular and molecular response required for successful axon regeneration. Proliferating Schwann cells organize into chains of cells bridging the lesion site, which is invaded by macrophages. Approximately half of the injured neuron population sends out axons that enter the glial guidance channels in response to secreted neurotrophic factors and neuropoietic cytokines. These lesion-associated polypeptides create an environment that is highly supportive for axon regrowth, particularly after acute injury, and ensure that the vast majority of regenerating axons are directed toward the distal nerve stump. Unfortunately, most neurotrophic factors and neuropoietic cytokines are also strong stimulators of axonal sprouting. Although some of the axonal branches will withdraw at later stages, the sprouting effect contributes to the misdirection of reinnervation that results in the lack of functional recovery observed in many patients with peripheral nerve injuries. Here, we critically review the role of neuronal growth factors and cytokines during axon regeneration in the peripheral nervous system. Their differential effects on axon elongation and sprouting were elucidated in various studies on intraneuronal signaling mechanisms following nerve lesion. The present data define a goal for future therapeutic strategies, namely, to selectively stimulate a Ras/Raf/ERK-mediated axon elongation program over an intrinsic PI3K-dependent axonal sprouting program in lesioned motor and sensory neurons. Instead of modulating growth factor or cytokine levels at the lesion site, targeting specific intraneuronal molecules, such as the negative feedback inhibitors of ERK signaling, has been shown to promote long-distance regeneration while avoiding sprouting of regenerating axons until they have reached their target areas.
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Affiliation(s)
- Lars Klimaschewski
- Division of Neuroanatomy, Department of Anatomy and Histology, Innsbruck Medical University, Innsbruck, Austria
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10
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Large-scale in vivo femtosecond laser neurosurgery screen reveals small-molecule enhancer of regeneration. Proc Natl Acad Sci U S A 2010; 107:18342-7. [PMID: 20937901 DOI: 10.1073/pnas.1005372107] [Citation(s) in RCA: 104] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Discovery of molecular mechanisms and chemical compounds that enhance neuronal regeneration can lead to development of therapeutics to combat nervous system injuries and neurodegenerative diseases. By combining high-throughput microfluidics and femtosecond laser microsurgery, we demonstrate for the first time large-scale in vivo screens for identification of compounds that affect neurite regeneration. We performed thousands of microsurgeries at single-axon precision in the nematode Caenorhabditis elegans at a rate of 20 seconds per animal. Following surgeries, we exposed the animals to a hand-curated library of approximately one hundred small molecules and identified chemicals that significantly alter neurite regeneration. In particular, we found that the PKC kinase inhibitor staurosporine strongly modulates regeneration in a concentration- and neuronal type-specific manner. Two structurally unrelated PKC inhibitors produce similar effects. We further show that regeneration is significantly enhanced by the PKC activator prostratin.
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Cavaletti G, Miloso M, Nicolini G, Scuteri A, Tredici G. Emerging role of mitogen-activated protein kinases in peripheral neuropathies. J Peripher Nerv Syst 2007; 12:175-94. [PMID: 17868245 DOI: 10.1111/j.1529-8027.2007.00138.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Among the different families of intracellular molecules that can be modulated during cell damage and repair, mitogen-activated protein kinases (MAPKs) are particularly interesting because they are involved in several intracellular pathways activated by injury and regeneration signals. Despite most of the studies have been performed in non-neurological models, recently a causal role for MAPKs has been postulated in central nervous system disorders. However, also in some peripheral neuropathies, MAPK changes can occur and these modifications might be relevant in the pathogenesis of the damage as well as during regeneration and repair. In this review, the current knowledge on the role of MAPKs in peripheral neuropathies will be discussed.
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Affiliation(s)
- Guido Cavaletti
- Department of Neurosciences and Biomedical Technologies, University of Milano Bicocca, Monza, Italy.
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12
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Au E, Richter MW, Vincent AJ, Tetzlaff W, Aebersold R, Sage EH, Roskams AJ. SPARC from olfactory ensheathing cells stimulates Schwann cells to promote neurite outgrowth and enhances spinal cord repair. J Neurosci 2007; 27:7208-21. [PMID: 17611274 PMCID: PMC6794587 DOI: 10.1523/jneurosci.0509-07.2007] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2007] [Revised: 04/23/2007] [Accepted: 05/17/2007] [Indexed: 11/21/2022] Open
Abstract
Olfactory ensheathing cells (OECs) transplanted into the lesioned CNS can stimulate reportedly different degrees of regeneration, remyelination, and functional recovery, but little is known about the mechanisms OECs may use to stimulate endogenous repair. Here, we used a functional proteomic approach, isotope-coded affinity tagging and mass spectrometry, to identify active components of the OEC secreteome that differentially stimulate outgrowth. SPARC (secreted protein acidic rich in cysteine) (osteonectin) was identified as an OEC-derived matricellular protein that can indirectly enhance the ability of Schwann cells to stimulate dorsal root ganglion outgrowth in vitro. SPARC stimulates Schwann cell-mediated outgrowth by cooperative signal with laminin-1 and transforming growth factor beta. Furthermore, when SPARC-null OECs were transplanted into lesioned rat spinal cord, the absence of OEC-secreted SPARC results in an attenuation of outgrowth of specific subsets of sensory and supraspinal axons and changes the pattern of macrophage infiltration in response to the transplanted cells. These data provide the first evidence for a role for SPARC in modulating different aspects of CNS repair and indicate that SPARC can change the activation state of endogenous Schwann cells, resulting in the promotion of outgrowth in vitro, and in vivo.
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Affiliation(s)
- Edmund Au
- Department of Zoology, Life Sciences Institute and
| | | | | | - Wolfram Tetzlaff
- Department of Zoology, Life Sciences Institute and
- International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3
| | - Ruedi Aebersold
- Institute for Systems Biology, Seattle, Washington 98103
- Molecular Systems Biology, Swiss Federal Institute of Technology of Zurich, CH-8092 Zurich, Switzerland, and
| | - E. Helene Sage
- Hope Heart Program, Benaroya Research Institute at Virginia Mason, Seattle, Washington 98101
| | - A. Jane Roskams
- Department of Zoology, Life Sciences Institute and
- International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3
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Ito H, Usuda N, Atsuzawa K, Iwamoto I, Sudo K, Katoh-Semba R, Mizutani K, Morishita R, Deguchi T, Nozawa Y, Asano T, Nagata KI. Phosphorylation by extracellular signal-regulated kinase of a multidomain adaptor protein, vinexin, at synapses. J Neurochem 2007; 100:545-54. [PMID: 17241162 DOI: 10.1111/j.1471-4159.2006.04222.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Vinexin is an adaptor protein that is supposed to play pivotal roles in cell adhesion, cytoskeletal organization and signaling. At least three splice variants, vinexinalpha, beta and gamma, have so far been reported. In spite of the possible importance of vinexin, the properties and functions of vinexin in neuronal cells are almost unknown. Here we show that vinexin isoforms are expressed in rat brain in a developmental stage-dependent manner, and that vinexinalpha is relatively abundant in the telencephalon regions of the adult rat brain. An immunohistochemical study showed the localization of vinexinalpha in neurons and glia in the rat brain. In primary cultured rat hippocampal neurons, vinexin was found to be present at synapses and filopodia in growth cones by immunofluorescent analyses. Biochemical fractionation revealed the distribution of vinexin in synaptosomes. Nerve terminal localization of vinexin was confirmed by electron microscopy. Vinexinbeta is reported to be phosphorylated by extracellular signal-regulated kinase (ERK) at Ser189, which is equivalent to Ser593 of vinexinalpha. We thus constructed a site- and phosphorylation state-specific antibody to monitor the ERK-mediated phosphorylation of vinexin. In immunofluorescent analyses, the phosphorylation was observed at synapses formed among cultured rat hippocampal neurons and it was reduced by treatment of the cells with PD98059. In an immunoelectron microscopic examination, the phosphorylation signal was mainly detected on the postsynaptic side of synapses in the rat hippocampal neurons. As active ERK was co-localized with vinexin in synapses, the ERK signal is likely to be involved in the regulation of vinexin-dependent cellular processes in synapses. On the other hand, the phosphorylation was hardly detected in neurons cultured for 3 days, suggesting the presence of a yet unidentified regulatory mechanism of vinexin at the growth cone.
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Affiliation(s)
- Hidenori Ito
- Department of Molecular Neurobiology, Institute for Developmental Research, Aichi Human Service Center, Kasugai, japan
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Nyíri G, Cserép C, Szabadits E, Mackie K, Freund TF. CB1 cannabinoid receptors are enriched in the perisynaptic annulus and on preterminal segments of hippocampal GABAergic axons. Neuroscience 2006; 136:811-22. [PMID: 16344153 DOI: 10.1016/j.neuroscience.2005.01.026] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2004] [Revised: 01/12/2005] [Accepted: 01/18/2005] [Indexed: 11/21/2022]
Abstract
Cannabinoids have been shown to modulate the inhibitory effect of cholecystokinin-containing GABAergic interneurons in the hippocampus via type 1 cannabinoid receptors (CB1 receptor). Although immunohistochemical studies, using pre-embedding techniques, have demonstrated that these receptors are abundant on GABAergic axon terminals, little is known about their exact location relative to the synapse. Here we used two recently developed antibodies against the CB1 receptor to study this question with the postembedding immunogold method, which allows the quantitative examination of receptor distribution along the axonal membrane, even within the synaptic active zone. CB1 receptor positive terminals target both the dendritic and somatic surface of neurons in the CA1 area of the rat hippocampus. We found no difference between these two populations of terminals either in their CB1 receptor density or in the distribution of receptors on their membrane. Recent studies suggest that endocannabinoids play a role in retrograde signaling at these synapses, i.e. signaling molecules diffuse from the postsynaptic membrane to nearby presynaptic terminals. Therefore, we examined the distribution of CB1 receptors on the terminal membranes. We found that they are rare in the synaptic active zone, but are enriched in the perisynaptic annulus, where they can directly influence synaptic calcium channels. Perisynaptic CB1 receptors represent about one tenth of all CB1 receptors in a terminal. In contrast, CB1 receptors have a lower density on the extrasynaptic membrane of terminals far from the postsynaptic cell. We estimated that these terminals contain exceptionally large numbers of CB1 receptors, i.e. a single axon terminal was usually labeled with more than 450 particles. An unexpected finding was that the density of CB1 receptors was significantly higher on preterminal axons than on synaptic terminals. These observations suggest that endocannabinoid signaling may subserve roles other than simply reducing transmitter release from axon terminals.
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Affiliation(s)
- G Nyíri
- Institute of Experimental Medicine, Hungarian Academy of Sciences, 1083, Szigony u. 43, Budapest, Hungary
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15
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Sapieha PS, Hauswirth WW, Di Polo A. Extracellular signal-regulated kinases 1/2 are required for adult retinal ganglion cell axon regeneration induced by fibroblast growth factor-2. J Neurosci Res 2006; 83:985-95. [PMID: 16493686 DOI: 10.1002/jnr.20803] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The intracellular signaling mechanisms used by neurotrophic factors to promote axon growth in the mature, injured central nervous system are not well understood. Here we investigated the signaling cascades that control fibroblast growth factor-2 (FGF-2)-mediated retinal ganglion cell (RGC) axon extension in vivo. For this purpose, a novel adeno-associated virus (AAV) was used to deliver the FGF-2 gene to RGCs, providing a sustained source of this neurotrophic factor. FGF-2 gene transfer led to an approximately ten-fold increase in the number of axons that extended past the lesion site compared with control nerves. Axon growth correlated with FGF-2-induced activation of the extracellular signal-regulated kinases 1/2 (Erk1/2), but not phosphoinositide 3-kinase or protein kinase C. Pharmacological inhibition of Erk1/2 activation resulted in an approximately 80% decrease in the number of axons that regenerated in the injured optic nerve. Our data demonstrate that the Erk1/2 pathway is an essential signaling component in FGF-2-mediated axon regeneration in the mature, injured visual system.
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Affiliation(s)
- Przemyslaw S Sapieha
- Department of Pathology and Cell Biology, Université de Montréal, Montreal, Quebec, Canada
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16
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Malik-Hall M, Dina OA, Levine JD. Primary afferent nociceptor mechanisms mediating NGF-induced mechanical hyperalgesia. Eur J Neurosci 2005; 21:3387-94. [PMID: 16026476 DOI: 10.1111/j.1460-9568.2005.04173.x] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The underlying mechanism for nerve growth factor (NGF) evoked pain and long-lasting mechanical hyperalgesia remains poorly understood. Using intrathecal antisense against the NGF receptor, receptor tyrosine kinase (TrkA), we found NGF to act at the primary afferent nociceptor directly in the Sprague-Dawley rat. Inhibitors of the three major pathways for TrkA receptor signalling, extracellular signal-related kinase (ERK)/mitogen-activated protein kinase kinase (MEK) (ERK/MEK), phosphatidylinositol 3-kinase (PI3K), and phospholipase Cgamma (PLCgamma) all attenuate NGF-induced hyperalgesia. Although inhibitors of kinases downstream of PI3K and PLCgamma[glycogen synthetase kinase 3 (GSK3), calmodulin-dependent protein kinase II (CAMII-K) or protein kinase C (PKC)] do not reduce mechanical hyperalgesia, hyperalgesia induced by activation of PI3K was blocked by ERK/MEK inhibitors, suggesting cross-talk from the PI3K to the ERK/MEK signalling pathway. As integrins have been shown to modulate epinephrine and prostaglandin E(2)-induced hyperalgesia, we also evaluated a role for integrins in NGF-induced mechanical hyperalgesia using beta(1)-integrin-specific antisense or antibodies.
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Affiliation(s)
- Misbah Malik-Hall
- NIH Pain Center (UCSF), Division of Neuroscience and Biomedical Sciences Program, University of California at San Francisco, 521 Parnassus Avenue, San Francisco, CA 94143, USA
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17
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Abstract
Current information indicates that glial cells participate in all the normal and pathological processes of the central nervous system. Although much less is known about satellite glial cells (SGCs) in sensory ganglia, it appears that these cells share many characteristics with their central counterparts. This review presents information that has been accumulated recently on the physiology and pharmacology of SGCs. It appears that SGCs carry receptors for numerous neuroactive agents (e.g., ATP, bradykinin) and can therefore receive signals from other cells and respond to changes in their environment. Activation of SGCs might in turn influence neighboring neurons. Thus SGCs are likely to participate in signal processing and transmission in sensory ganglia. Damage to the axons of sensory ganglia is known to contribute to neuropathic pain. Such damage also affects SGCs, and it can be proposed that these cells have a role in pathological changes in the ganglia.
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Affiliation(s)
- Menachem Hanani
- Laboratory of Experimental Surgery, Hadassah University Hospital, Mount Scopus, Jerusalem 91240, Israel
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18
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Pernet V, Hauswirth WW, Di Polo A. Extracellular signal-regulated kinase 1/2 mediates survival, but not axon regeneration, of adult injured central nervous system neurons in vivo. J Neurochem 2005; 93:72-83. [PMID: 15773907 DOI: 10.1111/j.1471-4159.2005.03002.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Neurotrophins play important roles in the response of adult neurons to injury. The intracellular signaling mechanisms used by neurotrophins to regulate survival and axon growth in the mature CNS in vivo are not well understood. The goal of this study was to define the role of the extracellular signal-regulated kinases 1/2 (Erk1/2) pathway in the survival and axon regeneration of adult rat retinal ganglion cells (RGCs), a prototypical central neuron population. We used recombinant adeno-associated virus (AAV) to selectively transduce RGCs with genes encoding constitutively active or wild-type mitogen-activated protein kinase kinase 1 (MEK1), the upstream activator of Erk1/2. In combination with anterograde and retrograde tracing techniques, we monitored neuronal survival and axon regeneration in vivo. MEK1 gene delivery led to robust and selective transgene expression in multiple RGC compartments including cell bodies, dendrites, axons and targets in the brain. Furthermore, MEK1 activation induced in vivo phosphorylation of Erk1/2 in RGC bodies and axons. Quantitative analysis of cell survival demonstrated that Erk1/2 activation promoted robust RGC neuroprotection after optic nerve injury. In contrast, stimulation of the Erk1/2 pathway was not sufficient to induce RGC axon growth beyond the lesion site. We conclude that the Erk1/2 pathway plays a key role in the survival of axotomized mammalian RGCs in vivo, and that activation of other signaling components is required for axon regeneration in the growth inhibitory CNS environment.
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Affiliation(s)
- Vincent Pernet
- Department of Pathology and Cell Biology, Université de Montréal, Montreal, Quebec, Canada
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19
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Shi GX, Andres DA. Rit contributes to nerve growth factor-induced neuronal differentiation via activation of B-Raf-extracellular signal-regulated kinase and p38 mitogen-activated protein kinase cascades. Mol Cell Biol 2005; 25:830-46. [PMID: 15632082 PMCID: PMC543422 DOI: 10.1128/mcb.25.2.830-846.2005] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Rit is one of the original members of a novel Ras GTPase subfamily that uses distinct effector pathways to transform NIH 3T3 cells and induce pheochromocytoma cell (PC6) differentiation. In this study, we find that stimulation of PC6 cells by growth factors, including nerve growth factor (NGF), results in rapid and prolonged Rit activation. Ectopic expression of active Rit promotes PC6 neurite outgrowth that is morphologically distinct from that promoted by oncogenic Ras (evidenced by increased neurite branching) and stimulates activation of both the extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein (MAP) kinase signaling pathways. Furthermore, Rit-induced differentiation is dependent upon both MAP kinase cascades, since MEK inhibition blocked Rit-induced neurite outgrowth, while p38 blockade inhibited neurite elongation and branching but not neurite initiation. Surprisingly, while Rit was unable to stimulate ERK activity in NIH 3T3 cells, it potently activated ERK in PC6 cells. This cell type specificity is explained by the finding that Rit was unable to activate C-Raf, while it bound and stimulated the neuronal Raf isoform, B-Raf. Importantly, selective down-regulation of Rit gene expression in PC6 cells significantly altered NGF-dependent MAP kinase cascade responses, inhibiting both p38 and ERK kinase activation. Moreover, the ability of NGF to promote neuronal differentiation was attenuated by Rit knockdown. Thus, Rit is implicated in a novel pathway of neuronal development and regeneration by coupling specific trophic factor signals to sustained activation of the B-Raf/ERK and p38 MAP kinase cascades.
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Affiliation(s)
- Geng-Xian Shi
- Department of Molecular and Cellular Biochemistry, Room MS639, Chandler Medical Center, University of Kentucky College of Medicine, 800 Rose St., Lexington, KY 40536-0298, USA
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20
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ULUPINAR EMEL, ÜNAL NEDIM, ERZURUMLU REHAS. Morphometric analysis of embryonic rat trigeminal neurons treated with different neurotrophins. ACTA ACUST UNITED AC 2004; 277:396-407. [PMID: 15052666 PMCID: PMC4260803 DOI: 10.1002/ar.a.20029] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
In whole-mount explant cultures of the trigeminal ganglion (TG) with intact peripheral and brainstem targets, exogenous application of nerve growth factor (NGF) and neurotrophin-3 (NT-3) leads to elongation and precocious arborization of embryonic trigeminal axons, respectively. In addition, neurotrophins play a major role in survival and differentiation of distinct classes of TG neurons. In the present study, we conducted morphometric analyses of trigeminal neurons exposed to exogenous NGF or NT-3 in whole-mount explant cultures. Explants dissected from embryonic day (E) 13 and E15 rats were cultured in the presence of serum-free medium (SFM) or in SFM supplemented with NGF or NT-3 for 3 days. TG neurons were then retrogradely labeled with lipophilic tracer DiI and their soma size distributions were compared following different treatments. The mean diameters of E13 and E15 trigeminal neurons grown in the presence of NT-3 were similar to those grown in SFM. On the other hand, in cultures supplemented with NGF, the mean diameters of neurons were larger at E13, but smaller at E15. Double immunolabeling with TrkA and TrkC antibodies confirmed the presence of large-diameter TrkA-positive neurons in E13 TG, but not in E15 TG. At both ages, other large-diameter neurons expressed only TrkC. These results show that exposure to NGF leads to phenotypic changes in TrkA-expressing trigeminal neurons at early embryonic development, but selective survival of small diameter neurons at later ages.
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Affiliation(s)
- EMEL ULUPINAR
- Department of Anatomy, Osmangazi University Faculty of Medicine, Eskişehir, Turkey
| | - NEDIM ÜNAL
- Department of Anatomy, Osmangazi University Faculty of Medicine, Eskişehir, Turkey
| | - REHA S. ERZURUMLU
- Department of Cell Biology and Anatomy, Louisiana State University Health Sciences Center, New Orleans, Louisiana
- Correspondence to: Dr. Reha S. Erzurumlu, Department of Cell Biology and Anatomy, Louisiana State University Health Sciences Center, 1901 Perdido Street, New Orleans, LA, 70112. Fax: 504-568-4392.
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21
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Thompson J, Dolcet X, Hilton M, Tolcos M, Davies AM. HGF promotes survival and growth of maturing sympathetic neurons by PI-3 kinase- and MAP kinase-dependent mechanisms. Mol Cell Neurosci 2004; 27:441-52. [PMID: 15555922 DOI: 10.1016/j.mcn.2004.07.007] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2004] [Revised: 07/26/2004] [Accepted: 07/27/2004] [Indexed: 11/16/2022] Open
Abstract
Hepatocyte growth factor (HGF) is a pleiotrophic factor whose many functions include promoting neuronal survival and growth. Hitherto, these effects have been observed in the presence of other neurotrophic factors like NGF and CNTF, and this requirement for an accessory factor has made it difficult to elucidate the signaling pathways that mediate its survival and growth-enhancing effects. Here, we show that HGF promotes the survival of mature sympathetic neurons of the superior cervical ganglion (SCG) grown at low density in defined medium lacking other neurotrophic factors. This effect was first clearly observed in cultures established from postnatal day 20 (P20) mice and became maximal by P40. HGF also enhanced the growth of neurite arbors from neurons throughout postnatal development and in the adult. HGF treatment resulted in phosphorylation of Akt and ERK1/ERK2. Preventing Akt activation with the phosphatidylinositol-3 (PI-3) kinase inhibitor LY294002 blocked the HGF survival response, and inhibition of ERK activation with the MEK inhibitors PD98059 or U0126 reduced the HGF survival response and the neurite growth-promoting effects of HGF. These results indicate that HGF promotes the survival and growth of maturing sympathetic neurons by both PI-3 kinase- and MAP kinase-dependent mechanisms.
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Affiliation(s)
- Jane Thompson
- Department of Preclinical Veterinary Sciences, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh EH9 1QH, Scotland, United Kingdom.
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22
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Kim IJ, Drahushuk KM, Kim WY, Gonsiorek EA, Lein P, Andres DA, Higgins D. Extracellular signal-regulated kinases regulate dendritic growth in rat sympathetic neurons. J Neurosci 2004; 24:3304-12. [PMID: 15056710 PMCID: PMC6730016 DOI: 10.1523/jneurosci.3286-03.2004] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
NGF activates several signaling cascades in sympathetic neurons. We examined how activation of one of these cascades, the ERK/MAP (extracellular signal-regulated kinase/mitogen-activated protein) kinase pathway, affects dendritic growth in these cells. Dendritic growth was induced by exposure to NGF and BMP-7 (bone morphogenetic protein-7). Exposure to NGF increased phosphorylation of ERK1/2. Unexpectedly, two MEK (MAP kinase kinase) inhibitors (PD 98059 and U 0126) enhanced dendritic growth, and a ligand, basic FGF, that activates the ERK pathway inhibited the growth of these processes. The enhancement of dendritic growth by PD 98059 was associated with an increase in the number of axo-dendritic synapses, and it appeared to represent a specific morphogenic effect because neither axonal growth nor cell survival was affected. In addition, increased dendritic growth was not observed after exposure to inhibitors of other signaling pathways, including the phosphatidylinositol-3-kinase inhibitor LY 294002. Dendritic growth was also increased in cells transfected with dominant-negative mutants of MEK1 and ERK2 but not with dominant-negative mutants of MEK5 and ERK5, suggesting that ERK1/2 is the primary mediator of this effect. Exposure to BMP-7 induces nuclear translocation of Smad1 (Sma- and Mad-related protein 1), and PD 98059 treatment potentiated nuclear accumulation of Smad-1 induced by BMP-7 in sympathetic neurons, suggesting a direct enhancement of BMP signaling in cells treated with an MEK inhibitor. These observations indicate that one of the signaling cascades activated by NGF can act in an antagonistic manner in sympathetic neurons and reduce the dendritic growth induced by other NGF-sensitive pathways.
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Affiliation(s)
- In-Jung Kim
- Department of Pharmacology and Toxicology, State University of New York, Buffalo, New York 14214, USA
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23
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Jones DM, Tucker BA, Rahimtula M, Mearow KM. The synergistic effects of NGF and IGF-1 on neurite growth in adult sensory neurons: convergence on the PI 3-kinase signaling pathway. J Neurochem 2003; 86:1116-28. [PMID: 12911620 DOI: 10.1046/j.1471-4159.2003.01925.x] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Nerve growth factor (NGF) and insulin-like growth factor-1 (IGF-1) play an important role in promoting axonal growth from dorsal root ganglion (DRG) neurons. Adult DRG neurons exhibit neurotrophin-independent survival, providing an excellent system with which to study trophic factor effects on neurite growth in the absence of significant survival effects. Using young adult rat DRG neurons we have demonstrated a synergistic effect of NGF plus IGF (N + I), compared with either factor alone, in promoting neurite growth. Not only does the presence of NGF and IGF-1 enhance neurite initiation, it also significantly augments the extent of neurite branching and elongation. We have also examined potential mechanism(s) underlying this synergistic effect. Immunoblotting experiments of classical growth factor intermediary signalling pathways (PI 3-K-Akt-GSK-3 and Ras-Raf-MAPK) were performed using phospho-specific antibodies to assess activation state. We found that activation of Akt and MAPK correlated with neurite elongation and branching. However, using pharmacological inhibitors, we observed that a PI 3-K pathway involving both Akt and GSK-3 appeared to be more important for neurite extension and branching than MAPK-dependent signalling. In fact, inhibition of activation of MAPK with U0126 resulted in increased neuritic branching, possibly as a result of the concomitant increase observed in phospho-Akt. Furthermore, inhibition of GSK3 (which is negatively regulated by phosphorylation on S9/S21) also resulted in increased growth. Our data point to signalling convergence upon the PI 3-K-Akt-GSK-3 pathway that underlies the NGF plus IGF synergism. In addition, to our knowledge, this is the first report in primary neurons that inhibition of GSK3 results in an enhanced neurite growth.
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Affiliation(s)
- David M Jones
- Division of Basic Medical Sciences, Faculty of Medicine, Memorial University of Newfoundland, 300 Prince Philip Drive, St. John's, Newfoundland, Canada A1B 3V6
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24
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Purves TD, Tomlinson DR. Are mitogen-activated protein kinases glucose transducers for diabetic neuropathies? INTERNATIONAL REVIEW OF NEUROBIOLOGY 2003; 50:83-114. [PMID: 12198822 DOI: 10.1016/s0074-7742(02)50074-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/26/2023]
Affiliation(s)
- Tertia D Purves
- Neuroscience Division, University of Manchester, School of Biological Sciences, Manchester M13 9PT, United Kingdom
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25
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Tam J, Danilovich N, Nilsson K, Sairam MR, Maysinger D. Chronic estrogen deficiency leads to molecular aberrations related to neurodegenerative changes in follitropin receptor knockout female mice. Neuroscience 2002; 114:493-506. [PMID: 12204217 DOI: 10.1016/s0306-4522(02)00278-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The follitropin receptor knockout (FORKO) mouse undergoes ovarian failure, thereby providing an animal model to investigate the consequences of the depletion of circulating estrogen in females. The estrogen deficiency causes marked defects in the female reproductive system, obesity, and skeletal abnormalities. In light of estrogen's known pleiotropic effects in the nervous system, our study examined the effects of genetically induced estrogen-testosterone imbalance on this system in female FORKO mice. Circulating concentrations of 17-beta-estradiol (E2) in FORKO mice are significantly decreased (FORKO -/-: 1.13+/-0.34 pg/ml; wild-type +/+: 17.6+/-3.5 pg/ml, P<0.0001, n=32-41); in contrast, testosterone levels are increased (-/-: 37.7+/-2.3 pg/ml; wild-type +/+: 3.9+/-1.7 pg/ml, P<0.005, n=25-33). The focus was on the activities of key enzymes in the central cholinergic and peripheral nervous systems, on dorsal root ganglia (DRGs) capacity for neurite outgrowth, and on the phosphorylation state of structural neurofilament (NF) proteins. Choline acetyltransferase activity was decreased in several central cholinergic structures (striatum 50+/-3%, hippocampus 24+/-2%, cortex 12+/-3%) and in DRGs (11+/-6%). Moreover, we observed aberrations in the enzymatic activities of mitogen-activated protein kinases (extracellular-regulated kinase and c-Jun N-terminal kinase) in the hippocampus, DRGs, and sciatic nerves. Hippocampal and sensory ganglia samples from FORKO mice contained hyper-phosphorylated NFs. Finally, explanted ganglia of FORKO mice displayed decreased neurite outgrowth (20-50%) under non-treated conditions and when treated with E2 (10 nM). Our results demonstrate that genetic depletion of circulating estrogen leads to biochemical and morphological changes in central and peripheral neurons, and underlie the importance of estrogen in the normal development and functioning of the nervous system. In particular, the findings suggest that an early and persisting absence of the steroid leads to neurodegenerative changes and identify several key enzymes that may contribute to the process. This model provides a system to explore the consequences of circulating estrogen deprivation and other hormonal imbalances in the nervous system.
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Affiliation(s)
- J Tam
- Department of Pharmacology and Therapeutics, McGill University, 3655 Promenade Sir-William-Osler, Room 1314, McIntyre Medical Sciences Building, Montreal, Quebec, Canada H3G 1Y6
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26
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Wiklund P, Ekström PAR, Edström A. Mitogen-activated protein kinase inhibition reveals differences in signalling pathways activated by neurotrophin-3 and other growth-stimulating conditions of adult mouse dorsal root ganglia neurons. J Neurosci Res 2002; 67:62-8. [PMID: 11754081 DOI: 10.1002/jnr.10073] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
PD98059 blocks mitogen-activated protein kinase (MAPK) by inhibiting its activator, MAP kinase kinase (MEK). We have previously found that PD98059 only transiently inhibits spontaneous axonal outgrowth from adult mouse dorsal root ganglia (DRG) explants, whereas it causes sustained inhibition of nerve growth factor (NGF)-stimulated growth. Surprisingly, the present results showed that outgrowth stimulation by neurotrophin-3 (NT-3), interacting with another neuronal subgroup, was markedly enhanced by PD98059 and also by U0126, another inhibitor of MAPK activation. In contrast, the effects of glial cell line-derived neurotrophic factor (GDNF), which stimulates still another subgroup of DRG neurons, was opposed by PD98059. Axonal outgrowth in vitro can also be strongly increased by a prior axotomy in vivo. The increased outgrowth in preaxotomized explants was effectively inhibited by the presence of PD98059. Immunocytochemistry based on whole-mount labelling revealed the presence of neuronal MAPK, which was found to be activated by NGF, NT-3, and GDNF in separate axonal populations and by a prior axotomy in a majority of growing axons. The results suggest that there are important differences in the NGF and NT-3 signalling pathways, which may involve positive and negative control mechanisms by MAPK activation, respectively. Other findings indicate that GDNF exerts its growth effects by activation of MAPK and that expression of the conditioning effect in vitro in preaxotomized preparations also requires activation of MAPK.
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Affiliation(s)
- Peter Wiklund
- Department of Animal Physiology, University of Lund, Lund, Sweden
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27
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Averill S, Delcroix JD, Michael GJ, Tomlinson DR, Fernyhough P, Priestley JV. Nerve growth factor modulates the activation status and fast axonal transport of ERK 1/2 in adult nociceptive neurones. Mol Cell Neurosci 2001; 18:183-96. [PMID: 11520179 DOI: 10.1006/mcne.2001.1015] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Mature dorsal root ganglion cells respond to neurotrophins, and the intracellular signalling pathways activated by neurotrophins have been characterized in vitro. We have now used immunocytochemistry and Western blots to examine the expression and activation of extracellular signal-regulated protein kinase-1/2 (ERK) in rat dorsal root ganglion cells in vivo, using antisera to total (tERK) and phosphorylated (pERK) forms. This has revealed a number of novel findings. tERK immunoreactivity is present in most dorsal root ganglion cells but is expressed most strongly in small (nociceptive) cells and, surprisingly, is absent in a population of large cells that expressed trkB or trkC but mainly lack p75(NTR) immunoreactivity. In contrast pERK is prominent in a few trkA cells and in satellite glial cells, and is further increased by NGF treatment. tERK and pERK both undergo fast anterograde and retrograde axonal transport, indicated by accumulation at a sciatic nerve ligature, and NGF reduces the level of retrograde pERK transport.
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MESH Headings
- Aging/physiology
- Animals
- Axonal Transport/drug effects
- Axonal Transport/physiology
- Axons/drug effects
- Axons/enzymology
- Axons/ultrastructure
- Cell Size/physiology
- Ganglia, Spinal/cytology
- Ganglia, Spinal/drug effects
- Ganglia, Spinal/enzymology
- Gene Expression Regulation, Enzymologic/physiology
- Immunohistochemistry
- Ligation
- Male
- Mitogen-Activated Protein Kinases/drug effects
- Mitogen-Activated Protein Kinases/metabolism
- Nerve Growth Factor/metabolism
- Nerve Growth Factor/pharmacology
- Neurons, Afferent/cytology
- Neurons, Afferent/drug effects
- Neurons, Afferent/enzymology
- Nociceptors/cytology
- Nociceptors/drug effects
- Nociceptors/enzymology
- Phosphorylation
- Rats
- Rats, Wistar
- Receptor, Nerve Growth Factor
- Receptor, trkA/metabolism
- Receptor, trkB/metabolism
- Receptor, trkC/metabolism
- Receptors, Nerve Growth Factor/metabolism
- Sciatic Nerve/drug effects
- Sciatic Nerve/enzymology
- Sciatic Nerve/surgery
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Affiliation(s)
- S Averill
- Department of Neuroscience, St. Bartholomew's School of Medicine and Dentistry, Queen Mary University of London, London, UK
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28
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Lei S, Dryden WF, Smith PA. Nerve growth factor regulates sodium but not potassium channel currents in sympathetic B neurons of adult bullfrogs. J Neurophysiol 2001; 86:641-50. [PMID: 11495939 DOI: 10.1152/jn.2001.86.2.641] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The TTX-sensitive and -resistant components of the voltage-gated Na(+) current (TTX-s I(Na) and TTX-r I(Na)) are increased within 2 wk of cutting the axons of B-cells in bullfrog paravertebral sympathetic ganglia (BFSG). Axotomy also increases the noninactivating, voltage-activated K(+) current (M current I(M)), whereas delayed rectifier K(+) current (I(K)) is reduced. We found that similar effects were produced when BFSG B cells were dissociated from adult bullfrogs and maintained in a defined-medium, neuron-enriched, low-density, serum-free culture. Thus the density of TTX-s I(Na), TTX-r I(Na), and I(M) were transiently increased, whereas I(K) density was decreased. Reduction in voltage-sensitive, Ca(2+)-dependent K(+) current (I(C)) was attributed to previously documented decreases in Ca(2+) channel current (I(Ca)). To test whether axotomy- or culture-induced changes in ion channel function reflect loss of retrograde influence of nerve growth factor (NGF), we examined the effect of murine beta-NGF on TTX-s I(Na), TTX-r I(Na), I(K), and I(M). Culture of neurons for 15 days in the presence of NGF (200 ng/ml), more than doubled total I(Na) density but did not enhance neurite outgrowth. The TTX-r I(Na) density was increased about threefold and the TTX-s I(Na) density increased 2.4-fold. NGF did not affect the activation or inactivation kinetics of the total Na(+) conductance. Effects of NGF were blocked by the transcription inhibitors, cordycepin (20 microM) and actinomycin D (0.01 microg/ml). I(K) and I(M) were unaffected by NGF, and although I(C) was enhanced, this likely reflected the known effect of NGF on I(Ca) in BFSG neurons. Na(+) channel synthesis and/or expression in adult sympathetic neurons is therefore subject to selective regulation by NGF. Despite this, the increase in I(Na) and I(M) as well as the decrease in I(K) seen in BFSG neurons in culture or after axotomy cannot readily be explained in terms of alterations in the availability of target-derived NGF.
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Affiliation(s)
- S Lei
- Department of Pharmacology and University Centre for Neuroscience, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
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