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Kranz TM, Grimm O. Update on genetics of attention deficit/hyperactivity disorder: current status 2023. Curr Opin Psychiatry 2023; 36:257-262. [PMID: 36728054 DOI: 10.1097/yco.0000000000000852] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
PURPOSE OF REVIEW Attention deficit/hyperactivity disorder (ADHD) shows consistently high heritability in genetic research. In this review article, we give an overview of the analysis of common and rare variants and some insight into current genetic methodology and their link to clinical practice. RECENT FINDINGS The heritability of about 80% is also high in comparison to other psychiatric diseases. However, recent studies estimate the proportion of heritability based on single nucleotide variants at 22%. The hidden heritability is an ongoing question in ADHD genetics. Common variants derived from mega genome-wide association analyses (GWAS) and subsequent meta-analyses usually display small effect sizes and explain only a small fraction of phenotypic variance. Rare variants, on the contrary, not only display large effect sizes but also rather explain, due to their rareness, a small fraction on phenotypic variance. Applying polygenic risk score (PRS) analysis is an improved approach of combining effect sizes of many common variants with clinically relevant measures in ADHD. SUMMARY We provide a concise overview on how genetic analysis, with a focus on GWAS and PRS, can help explain different behavioural phenotypes in ADHD and how they can be used for diagnosis and therapy prediction. Increased sample sizes of GWAS, meta-analyses and use of PRS is increasingly informative and sets the course for a new era in genetics of ADHD.
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Affiliation(s)
- Thorsten M Kranz
- Department of Psychiatry, Psychosomatic Medicine and Psychotherapy, University Hospital, Goethe University, Frankfurt, Germany
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Kawakami J, Brooks D, Zalmai R, Hartson SD, Bouyain S, Geisbrecht ER. Complex protein interactions mediate Drosophila Lar function in muscle tissue. PLoS One 2022; 17:e0269037. [PMID: 35622884 PMCID: PMC9140312 DOI: 10.1371/journal.pone.0269037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Accepted: 05/12/2022] [Indexed: 11/28/2022] Open
Abstract
The type IIa family of receptor protein tyrosine phosphatases (RPTPs), including Lar, RPTPσ and RPTPδ, are well-studied in coordinating actin cytoskeletal rearrangements during axon guidance and synaptogenesis. To determine whether this regulation is conserved in other tissues, interdisciplinary approaches were utilized to study Lar-RPTPs in the Drosophila musculature. Here we find that the single fly ortholog, Drosophila Lar (Dlar), is localized to the muscle costamere and that a decrease in Dlar causes aberrant sarcomeric patterning, deficits in larval locomotion, and integrin mislocalization. Sequence analysis uncovered an evolutionarily conserved Lys-Gly-Asp (KGD) signature in the extracellular region of Dlar. Since this tripeptide sequence is similar to the integrin-binding Arg-Gly-Asp (RGD) motif, we tested the hypothesis that Dlar directly interacts with integrin proteins. However, structural analyses of the fibronectin type III domains of Dlar and two vertebrate orthologs that include this conserved motif indicate that this KGD tripeptide is not accessible and thus unlikely to mediate physical interactions with integrins. These results, together with the proteomics identification of basement membrane (BM) proteins as potential ligands for type IIa RPTPs, suggest a complex network of protein interactions in the extracellular space that may mediate Lar function and/or signaling in muscle tissue.
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Affiliation(s)
- Jessica Kawakami
- Department of Cell and Molecular Biology and Biochemistry, University of Missouri-Kansas City, Kansas City, MO, United States of America
| | - David Brooks
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas, United States of America
| | - Rana Zalmai
- Department of Cell and Molecular Biology and Biochemistry, University of Missouri-Kansas City, Kansas City, MO, United States of America
| | - Steven D. Hartson
- Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK, United States of America
| | - Samuel Bouyain
- Department of Cell and Molecular Biology and Biochemistry, University of Missouri-Kansas City, Kansas City, MO, United States of America
| | - Erika R. Geisbrecht
- Department of Cell and Molecular Biology and Biochemistry, University of Missouri-Kansas City, Kansas City, MO, United States of America
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas, United States of America
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3
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Cornejo F, Cortés BI, Findlay GM, Cancino GI. LAR Receptor Tyrosine Phosphatase Family in Healthy and Diseased Brain. Front Cell Dev Biol 2021; 9:659951. [PMID: 34966732 PMCID: PMC8711739 DOI: 10.3389/fcell.2021.659951] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Accepted: 11/17/2021] [Indexed: 11/23/2022] Open
Abstract
Protein phosphatases are major regulators of signal transduction and they are involved in key cellular mechanisms such as proliferation, differentiation, and cell survival. Here we focus on one class of protein phosphatases, the type IIA Receptor-type Protein Tyrosine Phosphatases (RPTPs), or LAR-RPTP subfamily. In the last decade, LAR-RPTPs have been demonstrated to have great importance in neurobiology, from neurodevelopment to brain disorders. In vertebrates, the LAR-RPTP subfamily is composed of three members: PTPRF (LAR), PTPRD (PTPδ) and PTPRS (PTPσ), and all participate in several brain functions. In this review we describe the structure and proteolytic processing of the LAR-RPTP subfamily, their alternative splicing and enzymatic regulation. Also, we review the role of the LAR-RPTP subfamily in neural function such as dendrite and axon growth and guidance, synapse formation and differentiation, their participation in synaptic activity, and in brain development, discussing controversial findings and commenting on the most recent studies in the field. Finally, we discuss the clinical outcomes of LAR-RPTP mutations, which are associated with several brain disorders.
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Affiliation(s)
- Francisca Cornejo
- Center for Integrative Biology, Facultad de Ciencias, Universidad Mayor, Santiago, Chile
| | - Bastián I Cortés
- Center for Integrative Biology, Facultad de Ciencias, Universidad Mayor, Santiago, Chile
| | - Greg M Findlay
- MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Gonzalo I Cancino
- Center for Integrative Biology, Facultad de Ciencias, Universidad Mayor, Santiago, Chile.,Escuela de Biotecnología, Facultad de Ciencias, Universidad Mayor, Santiago, Chile
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Emperador-Melero J, de Nola G, Kaeser PS. Intact synapse structure and function after combined knockout of PTPδ, PTPσ, and LAR. eLife 2021; 10:e66638. [PMID: 33656439 PMCID: PMC7963474 DOI: 10.7554/elife.66638] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Accepted: 02/28/2021] [Indexed: 12/18/2022] Open
Abstract
It has long been proposed that leukocyte common antigen-related receptor protein tyrosine phosphatases (LAR-RPTPs) are cell-adhesion proteins that control synapse assembly. Their synaptic nanoscale localization, however, is not established, and synapse fine structure after knockout of the three vertebrate LAR-RPTPs (PTPδ, PTPσ, and LAR) has not been tested. Here, superresolution microscopy reveals that PTPδ localizes to the synaptic cleft precisely apposed to postsynaptic scaffolds of excitatory and inhibitory synapses. We next assessed synapse structure in newly generated triple-conditional-knockout mice for PTPδ, PTPσ, and LAR, complementing a recent independent study of synapse function after LAR-RPTP ablation (Sclip and Südhof, 2020). While mild effects on synaptic vesicle clustering and active zone architecture were detected, synapse numbers and their overall structure were unaffected, membrane anchoring of the active zone persisted, and vesicle docking and release were normal. Hence, despite their localization at synaptic appositions, LAR-RPTPs are dispensable for presynapse structure and function.
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Affiliation(s)
| | - Giovanni de Nola
- Department of Neurobiology, Harvard Medical SchoolBostonUnited States
| | - Pascal S Kaeser
- Department of Neurobiology, Harvard Medical SchoolBostonUnited States
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Dyck S, Kataria H, Alizadeh A, Santhosh KT, Lang B, Silver J, Karimi-Abdolrezaee S. Perturbing chondroitin sulfate proteoglycan signaling through LAR and PTPσ receptors promotes a beneficial inflammatory response following spinal cord injury. J Neuroinflammation 2018; 15:90. [PMID: 29558941 PMCID: PMC5861616 DOI: 10.1186/s12974-018-1128-2] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Accepted: 03/12/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Traumatic spinal cord injury (SCI) results in upregulation of chondroitin sulfate proteoglycans (CSPGs) by reactive glia that impedes repair and regeneration in the spinal cord. Degradation of CSPGs is known to be beneficial in promoting endogenous repair mechanisms including axonal sprouting/regeneration, oligodendrocyte replacement, and remyelination, and is associated with improvements in functional outcomes after SCI. Recent evidence suggests that CSPGs may regulate secondary injury mechanisms by modulating neuroinflammation after SCI. To date, the role of CSPGs in SCI neuroinflammation remains largely unexplored. The recent discovery of CSPG-specific receptors, leukocyte common antigen-related (LAR) and protein tyrosine phosphatase-sigma (PTPσ), allows unraveling the cellular and molecular mechanisms of CSPGs in SCI. In the present study, we have employed parallel in vivo and in vitro approaches to dissect the role of CSPGs and their receptors LAR and PTPσ in modulating the inflammatory processes in the acute and subacute phases of SCI. METHODS In a clinically relevant model of compressive SCI in female Sprague Dawley rats, we targeted LAR and PTPσ by two intracellular functionally blocking peptides, termed ILP and ISP, respectively. We delivered ILP and ISP treatment intrathecally to the injured spinal cord in a sustainable manner by osmotic mini-pumps for various time-points post-SCI. We employed flow cytometry, Western blotting, and immunohistochemistry in rat SCI, as well as complementary in vitro studies in primary microglia cultures to address our questions. RESULTS We provide novel evidence that signifies a key immunomodulatory role for LAR and PTPσ receptors in SCI. We show that blocking LAR and PTPσ reduces the population of classically activated M1 microglia/macrophages, while promoting alternatively activated M2 microglia/macrophages and T regulatory cells. This shift was associated with a remarkable elevation in pro-regenerative immune mediators, interleukin-10 (IL-10), and Arginase-1. Our parallel in vitro studies in microglia identified that while CSPGs do not induce an M1 phenotype per se, they promote a pro-inflammatory phenotype. Interestingly, inhibiting LAR and PTPσ in M1 and M2 microglia positively modulates their inflammatory response in the presence of CSPGs, and harnesses their ability for phagocytosis and mobilization. Interestingly, our findings indicate that CSPGs regulate microglia, at least in part, through the activation of the Rho/ROCK pathway downstream of LAR and PTPσ. CONCLUSIONS We have unveiled a novel role for LAR and PTPσ in regulating neuroinflammation in traumatic SCI. Our findings provide new insights into the mechanisms by which manipulation of CSPG signaling can promote recovery from SCI. More importantly, this work introduces the potential of ILP/ISP as a viable strategy for modulating the immune response following SCI and other neuroinflammatory conditions of the central nervous system.
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Affiliation(s)
- Scott Dyck
- Department of Physiology and Pathophysiology, the Regenerative Medicine Program, the Spinal Cord Research Center, University of Manitoba, 629-Basic Medical Sciences Building, 745 Bannatyne Avenue, Winnipeg, MB, R3E 0J9, Canada
| | - Hardeep Kataria
- Department of Physiology and Pathophysiology, the Regenerative Medicine Program, the Spinal Cord Research Center, University of Manitoba, 629-Basic Medical Sciences Building, 745 Bannatyne Avenue, Winnipeg, MB, R3E 0J9, Canada
| | - Arsalan Alizadeh
- Department of Physiology and Pathophysiology, the Regenerative Medicine Program, the Spinal Cord Research Center, University of Manitoba, 629-Basic Medical Sciences Building, 745 Bannatyne Avenue, Winnipeg, MB, R3E 0J9, Canada
| | - Kallivalappil T Santhosh
- Department of Physiology and Pathophysiology, the Regenerative Medicine Program, the Spinal Cord Research Center, University of Manitoba, 629-Basic Medical Sciences Building, 745 Bannatyne Avenue, Winnipeg, MB, R3E 0J9, Canada
| | - Bradley Lang
- Department of Neuroscience, Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA
| | - Jerry Silver
- Department of Neuroscience, Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA
| | - Soheila Karimi-Abdolrezaee
- Department of Physiology and Pathophysiology, the Regenerative Medicine Program, the Spinal Cord Research Center, University of Manitoba, 629-Basic Medical Sciences Building, 745 Bannatyne Avenue, Winnipeg, MB, R3E 0J9, Canada.
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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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Dyck SM, Karimi-Abdolrezaee S. Chondroitin sulfate proteoglycans: Key modulators in the developing and pathologic central nervous system. Exp Neurol 2015; 269:169-87. [PMID: 25900055 DOI: 10.1016/j.expneurol.2015.04.006] [Citation(s) in RCA: 123] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Revised: 04/11/2015] [Accepted: 04/14/2015] [Indexed: 12/15/2022]
Abstract
Chondroitin Sulfate Proteoglycans (CSPGs) are a major component of the extracellular matrix in the central nervous system (CNS) and play critical role in the development and pathophysiology of the brain and spinal cord. Developmentally, CSPGs provide guidance cues for growth cones and contribute to the formation of neuronal boundaries in the developing CNS. Their presence in perineuronal nets plays a crucial role in the maturation of synapses and closure of critical periods by limiting synaptic plasticity. Following injury to the CNS, CSPGs are dramatically upregulated by reactive glia which form a glial scar around the lesion site. Increased level of CSPGs is a hallmark of all CNS injuries and has been shown to limit axonal plasticity, regeneration, remyelination, and conduction after injury. Additionally, CSPGs create a non-permissive milieu for cell replacement activities by limiting cell migration, survival and differentiation. Mounting evidence is currently shedding light on the potential benefits of manipulating CSPGs in combination with other therapeutic strategies to promote spinal cord repair and regeneration. Moreover, the recent discovery of multiple receptors for CSPGs provides new therapeutic targets for targeted interventions in blocking the inhibitory properties of CSPGs following injury. Here, we will provide an in depth discussion on the impact of CSPGs in normal and pathological CNS. We will also review the recent preclinical therapies that have been developed to target CSPGs in the injured CNS.
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Affiliation(s)
- Scott M Dyck
- Regenerative Medicine Program, Department of Physiology and the Spinal Cord Research Centre, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Soheila Karimi-Abdolrezaee
- Regenerative Medicine Program, Department of Physiology and the Spinal Cord Research Centre, University of Manitoba, Winnipeg, Manitoba, Canada.
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8
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Stoker AW. RPTPs in axons, synapses and neurology. Semin Cell Dev Biol 2014; 37:90-7. [PMID: 25234542 DOI: 10.1016/j.semcdb.2014.09.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Revised: 09/04/2014] [Accepted: 09/05/2014] [Indexed: 01/06/2023]
Abstract
Receptor-like protein tyrosine phosphatases represent a large protein family related to cell adhesion molecules, with diverse roles throughout neural development in vertebrates and invertebrates. This review focuses on their roles in axon growth, guidance and repair, as well as more recent findings demonstrating their key roles in pre-synaptic and post-synaptic maturation and function. These enzymes have been linked to memory and neuropsychiatric defects in loss-of-function rodent models, highlighting their potential as future drug targets.
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Affiliation(s)
- Andrew W Stoker
- Institute of Child Health, University College London, United Kingdom.
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9
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Ohtake Y, Li S. Molecular mechanisms of scar-sourced axon growth inhibitors. Brain Res 2014; 1619:22-35. [PMID: 25192646 DOI: 10.1016/j.brainres.2014.08.064] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 08/21/2014] [Indexed: 12/29/2022]
Abstract
Astrogliosis is a defense response of the CNS to minimize primary damage and to repair injured tissues, but it ultimately generates harmful effects by upregulating inhibitory molecules to suppress neuronal elongation and forming potent barriers to axon regeneration. Chondroitin sulfate proteoglycans (CSPGs) are highly expressed by reactive scars and are potent contributors to the non-permissive environment in mature CNS. Surmounting strong inhibition by CSPG-rich scar is an important therapeutic goal for achieving functional recovery after CNS injuries. Currently, enzymatic digestion of CSPGs with locally applied chondroitinase ABC is the main in vivo approach to overcome scar inhibition, but several disadvantages may prevent using this bacterial enzyme as a therapeutic option for patients. A better understanding of molecular mechanisms underlying CSPG function may facilitate development of new effective therapies to overcome scar-mediated inhibition. Previous studies support that CSPGs act by non-specifically hindering the binding of matrix molecules to their cell surface receptors through steric interactions, but two members of the leukocyte common antigen related (LAR) phosphatase subfamily, protein tyrosine phosphatase σ and LAR, are functional receptors that bind CSPGs with high affinity and mediate CSPG inhibition. CSPGs may also act by binding two receptors for myelin-associated growth inhibitors, Nogo receptors 1 and 3. Thus, CSPGs inhibit axon growth through multiple mechanisms, making them especially potent and difficult therapeutic targets. Identification of CSPG receptors is not only important for understanding the scar-mediated growth suppression, but also for developing novel and selective therapies to promote axon sprouting and/or regeneration after CNS injuries. This article is part of a Special Issue entitled SI: Spinal cord injury.
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Affiliation(s)
- Yosuke Ohtake
- Shriners Hospitals Pediatric Research Center and Department of Anatomy and Cell Biology, Temple University School of Medicine, 3500N. Broad Street, Philadelphia 19140, PA, USA
| | - Shuxin Li
- Shriners Hospitals Pediatric Research Center and Department of Anatomy and Cell Biology, Temple University School of Medicine, 3500N. Broad Street, Philadelphia 19140, PA, USA.
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Joshi CS, Khan SA, Khole VV. Regulation of acrosome reaction by Liprin α3, LAR and its ligands in mouse spermatozoa. Andrology 2013; 2:165-74. [PMID: 24327330 DOI: 10.1111/j.2047-2927.2013.00167] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2013] [Revised: 11/01/2013] [Accepted: 11/04/2013] [Indexed: 11/30/2022]
Abstract
Zona pellucida-based induction of acrosome reaction (AR) is a popular and well-accepted hypothesis. However, this hypothesis is being challenged in recent years and it has been proposed that the cumulus cells might be the site of AR. In our previous study, we reported the presence of a synaptic protein Liprin α3 on sperm acrosome, and proposed its role in AR. This study was designed to understand the role of Liprin α3 and its interacting proteins in regulation of AR. It is observed that the presence of anti-Liprin α3 antibody inhibits the process of AR. Colocalization experiments demonstrate the coexistence of leucocyte antigen related (LAR) protein, Rab-interacting molecule (RIM) and Liprin α3 on sperm acrosome thereby completing the identification of all the members of RIM/MUNC/Rab3A/liprinα complex required for membrane fusion. This study demonstrates the effect of LAR ligands such as Syndecans, Nidogens and LAR wedge domain peptide on AR. We could see an increase in AR in presence of these ligands. On the basis of these data, we speculate that in presence of ligands or wedge peptide, LAR undergoes dimerization leading to inhibition of phosphatase activity and increase in AR. The presence of one of the ligands Syndecan-1 on cumulus cells led us to hypothesize that it is Syndecan which induces AR in vivo and thus another site of AR could lie in cumulus.
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Affiliation(s)
- C S Joshi
- Department of Gamete Immunobiology, National Institute for Research in Reproductive Health, Mumbai, India
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Sharma K, Selzer ME, Li S. Scar-mediated inhibition and CSPG receptors in the CNS. Exp Neurol 2012; 237:370-8. [PMID: 22836147 PMCID: PMC5454774 DOI: 10.1016/j.expneurol.2012.07.009] [Citation(s) in RCA: 136] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Accepted: 07/14/2012] [Indexed: 11/21/2022]
Abstract
Severed axons in adult mammals do not regenerate appreciably after central nervous system (CNS) injury due to developmentally determined reductions in neuron-intrinsic growth capacity and extracellular environment for axon elongation. Chondroitin sulfate proteoglycans (CSPGs), which are generated by reactive scar tissues, are particularly potent contributors to the growth-limiting environment in mature CNS. Thus, surmounting the strong inhibition by CSPG-rich scar is an important therapeutic goal for achieving functional recovery after CNS injuries. As of now, the main in vivo approach to overcoming inhibition by CSPGs is enzymatic digestion with locally applied chondroitinase ABC (ChABC), but several disadvantages may prevent using this bacterial enzyme as a therapeutic option for patients. A better understanding of the molecular mechanisms underlying CSPG action is needed in order to develop more effective therapies to overcome CSPG-mediated inhibition of axon regeneration and/or sprouting. Because of their large size and dense negative charges, CSPGs were thought to act by non-specifically hindering the binding of matrix molecules to their cell surface receptors through steric interactions. Although this may be true, recent studies indicate that two members of the leukocyte common antigen related (LAR) phosphatase subfamily, protein tyrosine phosphatase σ (PTPσ) and LAR, are functional receptors that bind CSPGs with high affinity and mediate CSPG inhibitory effects. CSPGs also may act by binding to two receptors for myelin-associated growth inhibitors, Nogo receptors 1 and 3 (NgR1 and NgR3). If confirmed, it would suggest that CSPGs have multiple mechanisms by which they inhibit axon growth, making them especially potent and difficult therapeutic targets. Identification of CSPG receptors is not only important for understanding the scar-mediated growth suppression, but also for developing novel and selective therapies to promote axon sprouting and/or regeneration after CNS injuries, including spinal cord injury (SCI).
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Affiliation(s)
- Kartavya Sharma
- Department of Neurology and Neuroscience Graduate Program, UT Southwestern Medical Center, Dallas, Texas 75390-8813, USA
| | - Michael E. Selzer
- Shriners Hospitals Pediatric Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania 19140
| | - Shuxin Li
- Department of Neurology and Neuroscience Graduate Program, UT Southwestern Medical Center, Dallas, Texas 75390-8813, USA
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Receptor type protein tyrosine phosphatases (RPTPs) - roles in signal transduction and human disease. J Cell Commun Signal 2012; 6:125-38. [PMID: 22851429 DOI: 10.1007/s12079-012-0171-5] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Accepted: 07/12/2012] [Indexed: 01/06/2023] Open
Abstract
Protein tyrosine phosphorylation is a fundamental regulatory mechanism controlling cell proliferation, differentiation, communication, and adhesion. Disruption of this key regulatory mechanism contributes to a variety of human diseases including cancer, diabetes, and auto-immune diseases. Net protein tyrosine phosphorylation is determined by the dynamic balance of the activity of protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs). Mammals express many distinct PTKs and PTPs. Both of these families can be sub-divided into non-receptor and receptor subtypes. Receptor protein tyrosine kinases (RPTKs) comprise a large family of cell surface proteins that initiate intracellular tyrosine phosphorylation-dependent signal transduction in response to binding of extracellular ligands, such as growth factors and cytokines. Receptor-type protein tyrosine phosphatases (RPTPs) are enzymatic and functional counterparts of RPTKs. RPTPs are a family of integral cell surface proteins that possess intracellular PTP activity, and extracellular domains that have sequence homology to cell adhesion molecules. In comparison to extensively studied RPTKs, much less is known about RPTPs, especially regarding their substrate specificities, regulatory mechanisms, biological functions, and their roles in human diseases. Based on the structure of their extracellular domains, the RPTP family can be grouped into eight sub-families. This article will review one representative member from each RPTP sub-family.
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Identification of novel, less toxic PTP-LAR inhibitors using in silico strategies: pharmacophore modeling, SADMET-based virtual screening and docking. J Mol Model 2011; 18:187-201. [PMID: 21523550 DOI: 10.1007/s00894-011-1037-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2010] [Accepted: 03/10/2011] [Indexed: 12/31/2022]
Abstract
Human leukocyte antigen-related (PTP-LAR) is a receptor-like transmembrane phosphatase and a potential target for diabetes, obesity and cancer. In the present study, a sequence of in silico strategies (pharmacophore mapping, a 3D database searching, SADMET screening, and docking and toxicity studies) was performed to identify eight novel nontoxic PTP-LAR inhibitors. Twenty different pharmacophore hypotheses were generated using two methods; the best (hypothesis 2) consisted of three hydrogen-bond acceptor (A), one ring aromatic (R), and one hydrophobic aliphatic (Z) features. This hypothesis was used to screen molecules from several databases, such as Specs, IBS, MiniMaybridge, NCI, and an in-house PTP inhibitor database. In order to overcome the general bioavailability problem associated with phosphatases, the hits obtained were filtered by Lipinski's rule of five and SADMET properties and validated by molecular docking studies using the available crystal structure 1LAR. These docking studies suggested the ligand binding pattern and interactions required for LAR inhibition. The docking analysis also revealed that sulfonylurea derivatives with an isoquinoline or naphthalene scaffold represent potential LAR drugs. The screening protocol was further validated using ligand pharmacophore mapping studies, which showed that the abovementioned interactions are indeed crucial and that the screened molecules can be presumed to possess potent inhibitory activities.
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14
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Baker MW, Macagno ER. Expression levels of a LAR-like receptor protein tyrosine phosphatase correlate with neuronal branching and arbor density in the medicinal leech. Dev Biol 2010; 344:346-57. [PMID: 20541541 DOI: 10.1016/j.ydbio.2010.06.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2009] [Revised: 05/28/2010] [Accepted: 06/03/2010] [Indexed: 12/24/2022]
Abstract
LAR-like receptor protein tyrosine phosphatases (RPTPs), which are reported to be highly expressed in the nervous systems of most bilaterian animals, have been implicated in the regulation of critical developmental processes, such as neuronal pathfinding, cell adhesion and synaptogenesis. Here we report that two LAR-like RPTPs in the medicinal leech, HmLAR1 and HmLAR2, play roles in regulating the size and density of neuronal arbors within the developing nervous system and in the body wall. Employing single-cell RNAi knockdown and transgene expression techniques, we demonstrate that the expression level of HmLAR1 is directly correlated with the density of an identified neuron's arborization. Knocking down HmLAR1 mRNA levels in the mechanosensory pressure (P) neurons produces a reduced central arbor and a smaller arbor in the peripheral body wall, with fewer terminal branches. By contrast, overexpression of this receptor in a P cell leads to extensive neuronal sprouting, including many supernumerary neurites and terminal branches as well as, in some instances, the normal monopolar morphology of the P cell becoming multipolar. We also report that induced neuronal sprouting requires the expression of the receptor's membrane tethered ectodomain, including the NH(2)-Ig domains, but not of the intracellular phosphatase domains of the receptor. Interestingly, sprouting could be elicited upon ectopic expression of HmLAR1 and the related RPTP, HmLAR2 in the P and other neurons, including those that do not normally express either RPTP, suggesting that the substrates involved in HmLAR-induced sprouting are present in most neurons irrespective of whether they normally express these LAR-like RPTPs. Our data are consistent with the hypothesis that the receptors' ectodomains promote an adhesive interaction that enhances the maintenance of new processes.
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Affiliation(s)
- Michael W Baker
- Division of Biology, University of California, San Diego, CA 92093, USA.
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15
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Massa SM, Yang T, Xie Y, Shi J, Bilgen M, Joyce JN, Nehama D, Rajadas J, Longo FM. Small molecule BDNF mimetics activate TrkB signaling and prevent neuronal degeneration in rodents. J Clin Invest 2010; 120:1774-85. [PMID: 20407211 DOI: 10.1172/jci41356] [Citation(s) in RCA: 301] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Accepted: 02/17/2010] [Indexed: 02/01/2023] Open
Abstract
Brain-derived neurotrophic factor (BDNF) activates the receptor tropomyosin-related kinase B (TrkB) with high potency and specificity, promoting neuronal survival, differentiation, and synaptic function. Correlations between altered BDNF expression and/or function and mechanism(s) underlying numerous neurodegenerative conditions, including Alzheimer disease and traumatic brain injury, suggest that TrkB agonists might have therapeutic potential. Using in silico screening with a BDNF loop-domain pharmacophore, followed by low-throughput in vitro screening in mouse fetal hippocampal neurons, we have efficiently identified small molecules with nanomolar neurotrophic activity specific to TrkB versus other Trk family members. Neurotrophic activity was dependent on TrkB and its downstream targets, although compound-induced signaling activation kinetics differed from those triggered by BDNF. A selected prototype compound demonstrated binding specificity to the extracellular domain of TrkB. In in vitro models of neurodegenerative disease, it prevented neuronal degeneration with efficacy equal to that of BDNF, and when administered in vivo, it caused hippocampal and striatal TrkB activation in mice and improved motor learning after traumatic brain injury in rats. These studies demonstrate the utility of loop modeling in drug discovery and reveal what we believe to be the first reported small molecules derived from a targeted BDNF domain that specifically activate TrkB.We propose that these compounds constitute a novel group of tools for the study of TrkB signaling and may provide leads for developing new therapeutic agents for neurodegenerative diseases.
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Affiliation(s)
- Stephen M Massa
- Department of Neurology and Laboratory for Computational Neurochemistry and Drug Discovery, UCSF, San Francisco, California, USA
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16
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Fry EJ, Chagnon MJ, López-Vales R, Tremblay ML, David S. Corticospinal tract regeneration after spinal cord injury in receptor protein tyrosine phosphatase sigma deficient mice. Glia 2010; 58:423-33. [PMID: 19780196 DOI: 10.1002/glia.20934] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Receptor protein tyrosine phosphatase sigma (RPTPsigma) plays a role in inhibiting axon growth during development. It has also been shown to slow axon regeneration after peripheral nerve injury and inhibit axon regeneration in the optic nerve. Here, we assessed the ability of the corticospinal tract (CST) axons to regenerate after spinal hemisection and contusion injury in RPTPsigma deficient (RPTPsigma(-/-)) mice. We show that damaged CST fibers in RPTPsigma(-/-) mice regenerate and appear to extend for long distances after a dorsal hemisection or contusion injury of the thoracic spinal cord. In contrast, no long distance axon regeneration of CST fibers is seen after similar lesions in wild-type mice. In vitro experiments indicate that cerebellar granule neurons from RPTPsigma(-/-) mice have reduced sensitivity to the inhibitory effects of chondroitin sulfate proteoglycan (CSPG) substrate, but not myelin, which may contribute to the growth of CST axons across the CSPG-rich glial scar. Our data suggest that RPTPsigma may function to prevent axonal growth after injury in the adult mammalian spinal cord and could be a target for promoting long distance regeneration after spinal cord injury.
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Affiliation(s)
- Elizabeth J Fry
- Centre for Research in Neuroscience, The Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada
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17
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The receptor protein tyrosine phosphatase LAR promotes R7 photoreceptor axon targeting by a phosphatase-independent signaling mechanism. Proc Natl Acad Sci U S A 2009; 106:19399-404. [PMID: 19889974 DOI: 10.1073/pnas.0903961106] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Receptor protein tyrosine phosphatases (RPTPs) control many aspects of nervous system development. At the Drosophila neuromuscular junction (NMJ), regulation of synapse growth and maturation by the RPTP LAR depends on catalytic phosphatase activity and on the extracellular ligands Syndecan and Dally-like. We show here that the function of LAR in controlling R7 photoreceptor axon targeting in the visual system differs in several respects. The extracellular domain of LAR important for this process is distinct from the domains known to bind Syndecan and Dally-like, suggesting the involvement of a different ligand. R7 targeting does not require LAR phosphatase activity, but instead depends on the phosphatase activity of another RPTP, PTP69D. In addition, a mutation that prevents dimerization of the intracellular domain of LAR interferes with its ability to promote R7 targeting, although it does not disrupt phosphatase activity or neuromuscular synapse growth. We propose that LAR function in R7 is independent of its phosphatase activity, but requires structural features that allow dimerization and may promote the assembly of downstream effectors.
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18
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Woo J, Kwon SK, Kim E. The NGL family of leucine-rich repeat-containing synaptic adhesion molecules. Mol Cell Neurosci 2009; 42:1-10. [PMID: 19467332 DOI: 10.1016/j.mcn.2009.05.008] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2009] [Accepted: 05/14/2009] [Indexed: 10/20/2022] Open
Abstract
Cell adhesion molecules at neuronal synapses regulate diverse aspects of synaptic development, including axo-dendritic contact establishment, early synapse formation, and synaptic maturation. Recent studies have identified several synaptogenic adhesion molecules. The NGL (netrin-G ligand; LRRC4) family of synaptic cell adhesion molecules belongs to the superfamily of leucine-rich repeat (LRR) proteins. The three known members of the NGL family, NGL-1, NGL-2, and NGL-3, are mainly localized to the postsynaptic side of excitatory synapses, and interact with the presynaptic ligands, netrin-G1, netrin-G2, and LAR, respectively. NGLs interact with the abundant postsynaptic density (PSD) protein, PSD-95, and other postsynaptic proteins, including NMDA receptors. These interactions are thought to couple synaptic adhesion events to the assembly of synaptic proteins. In addition, NGL proteins regulate axonal outgrowth and lamina-specific dendritic segmentation, suggesting that the NGL-dependent adhesion system is important for the development of axons, dendrites, and synapses. Consistent with these functions, defects in NGLs and their ligands are associated with impaired learning and memory, hyperactivity, and an abnormal acoustic startle response in transgenic mice, and schizophrenia, bipolar disorder, and Rett syndrome in human patients.
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Affiliation(s)
- Jooyeon Woo
- National Creative Research Initiative Center for Synaptogenesis, Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Republic of Korea
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19
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Trans-synaptic adhesion between NGL-3 and LAR regulates the formation of excitatory synapses. Nat Neurosci 2009; 12:428-37. [PMID: 19252495 DOI: 10.1038/nn.2279] [Citation(s) in RCA: 162] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2008] [Accepted: 01/22/2009] [Indexed: 12/11/2022]
Abstract
Synaptic adhesion molecules regulate multiple steps of synapse formation and maturation. The great diversity of neuronal synapses predicts the presence of a large number of adhesion molecules that control synapse formation through trans-synaptic and heterophilic adhesion. We identified a previously unknown trans-synaptic interaction between netrin-G ligand-3 (NGL-3), a postsynaptic density (PSD) 95-interacting postsynaptic adhesion molecule, and leukocyte common antigen-related (LAR), a receptor protein tyrosine phosphatase. NGL-3 and LAR expressed in heterologous cells induced pre- and postsynaptic differentiation in contacting axons and dendrites of cocultured rat hippocampal neurons, respectively. Neuronal overexpression of NGL-3 increased presynaptic contacts on dendrites of transfected neurons. Direct aggregation of NGL-3 on dendrites induced coclustering of excitatory postsynaptic proteins. Knockdown of NGL-3 reduced the number and function of excitatory synapses. Competitive inhibition by soluble LAR reduced NGL-3-induced presynaptic differentiation. These results suggest that the trans-synaptic adhesion between NGL-3 and LAR regulates excitatory synapse formation in a bidirectional manner.
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20
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Yang T, Knowles JK, Lu Q, Zhang H, Arancio O, Moore LA, Chang T, Wang Q, Andreasson K, Rajadas J, Fuller GG, Xie Y, Massa SM, Longo FM. Small molecule, non-peptide p75 ligands inhibit Abeta-induced neurodegeneration and synaptic impairment. PLoS One 2008; 3:e3604. [PMID: 18978948 PMCID: PMC2575383 DOI: 10.1371/journal.pone.0003604] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2008] [Accepted: 10/09/2008] [Indexed: 11/19/2022] Open
Abstract
The p75 neurotrophin receptor (p75(NTR)) is expressed by neurons particularly vulnerable in Alzheimer's disease (AD). We tested the hypothesis that non-peptide, small molecule p75(NTR) ligands found to promote survival signaling might prevent Abeta-induced degeneration and synaptic dysfunction. These ligands inhibited Abeta-induced neuritic dystrophy, death of cultured neurons and Abeta-induced death of pyramidal neurons in hippocampal slice cultures. Moreover, ligands inhibited Abeta-induced activation of molecules involved in AD pathology including calpain/cdk5, GSK3beta and c-Jun, and tau phosphorylation, and prevented Abeta-induced inactivation of AKT and CREB. Finally, a p75(NTR) ligand blocked Abeta-induced hippocampal LTP impairment. These studies support an extensive intersection between p75(NTR) signaling and Abeta pathogenic mechanisms, and introduce a class of specific small molecule ligands with the unique ability to block multiple fundamental AD-related signaling pathways, reverse synaptic impairment and inhibit Abeta-induced neuronal dystrophy and death.
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Affiliation(s)
- Tao Yang
- Department of Neurology and Neurological Science, Stanford University, Stanford, California, United States of America
- Department of Neurology, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Juliet K. Knowles
- Department of Neurology and Neurological Science, Stanford University, Stanford, California, United States of America
- Department of Neurology, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Qun Lu
- Department of Anatomy and Cell Biology, The Brody School of Medicine at East Carolina University, Greenville, North Carolina, United States of America
| | - Hong Zhang
- Department of Pathology and Taub Institute, Columbia University, New York, New York, United States of America
| | - Ottavio Arancio
- Department of Pathology and Taub Institute, Columbia University, New York, New York, United States of America
| | - Laura A. Moore
- Department of Neurology, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Timothy Chang
- Department of Neurology and Neurological Science, Stanford University, Stanford, California, United States of America
| | - Qian Wang
- Department of Neurology and Neurological Science, Stanford University, Stanford, California, United States of America
| | - Katrin Andreasson
- Department of Neurology and Neurological Science, Stanford University, Stanford, California, United States of America
| | - Jayakumar Rajadas
- Department of Neurology and Neurological Science, Stanford University, Stanford, California, United States of America
- Department of Chemical Engineering, Stanford University, Stanford, California, United States of America
| | - Gerald G. Fuller
- Department of Chemical Engineering, Stanford University, Stanford, California, United States of America
| | - Youmei Xie
- Department of Neurology, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Stephen M. Massa
- Department of Neurology and Laboratory for Computational Neurochemistry and Drug Discovery, San Francisco Veterans Affairs Medical Center, and Department of Neurology, University of California San Francisco, San Francisco, California, United States of America
| | - Frank M. Longo
- Department of Neurology and Neurological Science, Stanford University, Stanford, California, United States of America
- Department of Neurology, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina, United States of America
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21
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Li J, Niu XL, Madamanchi NR. Leukocyte antigen-related protein tyrosine phosphatase negatively regulates hydrogen peroxide-induced vascular smooth muscle cell apoptosis. J Biol Chem 2008; 283:34260-72. [PMID: 18854310 DOI: 10.1074/jbc.m806087200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Reactive oxygen species (ROS) have been implicated in vascular smooth muscle cell (VSMC) apoptosis, a hallmark of advanced atherosclerotic lesions. Transient oxidation and inactivation of protein-tyrosine phosphatases play a critical role in cellular response to ROS production. However, the function of leukocyte antigen-related (LAR) protein-tyrosine phosphatase in ROS signaling is not known. To determine the expression of LAR in ROS-induced apoptosis, we investigated hydrogen peroxide-induced cell death and signaling in aortic VSMCs from wild-type and LAR(-/-) mice. Histone-associated DNA fragmentation and caspase-3/7 activity were significantly enhanced, mitochondrial membrane integrity was compromised, and cell viability was significantly decreased following H(2)O(2) treatment in LAR(-/-) VSMCs compared with wild-type cells. Stronger and sustained increase in autophosphorylation and activity of Fyn, an Src family tyrosine kinase, was observed in LAR(-/-) cells compared with wild-type cells following H(2)O(2) treatment. LAR binds to activated Fyn in H(2)O(2)-treated VSMCs, and recombinant LAR dephosphorylates phosphorylated-Fyn in vitro. In addition, LAR deficiency enhanced H(2)O(2)-induced phosphorylation of Janus kinase 2 (JAK2), signal transducer and activator of transcription 3 (STAT3), and p38 mitogen-activated protein kinase (MAPK). PP2, a Fyn-specific inhibitor, blocked JAK2, STAT3, and p38 MAPK activation and significantly attenuated apoptosis induced by H(2)O(2). AG490, a JAK2-specific inhibitor, significantly attenuated H(2)O(2)-induced apoptosis, and blocked H(2)O(2)-induced activation of STAT3, but not p38 MAPK in both wild-type and LAR(-/-) VSMCs. Attenuation of Fyn expression by short hairpin RNA significantly decreased H(2)O(2)-induced downstream signaling and apoptosis in VSMCs. Together, these data indicate that LAR regulates Fyn/JAK2/STAT3 and Fyn/p38 MAPK pathways involved in ROS-induced apoptosis.
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Affiliation(s)
- Juxiang Li
- Department of Medicine, Carolina Cardiovascular Biology Center, University of North Carolina, Chapel Hill, North Carolina 27599-7126, USA
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22
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Ling Q, Huang Y, Zhou Y, Cai Z, Xiong B, Zhang Y, Ma L, Wang X, Li X, Li J, Shen J. Illudalic acid as a potential LAR inhibitor: synthesis, SAR, and preliminary studies on the mechanism of action. Bioorg Med Chem 2008; 16:7399-409. [PMID: 18579388 DOI: 10.1016/j.bmc.2008.06.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2008] [Revised: 06/08/2008] [Accepted: 06/10/2008] [Indexed: 11/30/2022]
Abstract
A novel synthesis of the human leukocyte common antigen-related (LAR) phosphatase inhibitor, illudalic acid, has been achieved by a route more amenable to structure modifications. A series of simpler analogues of illudalic acid was synthesized and evaluated for potency in inhibiting LAR. The structure-activity relationship (SAR) study has shown that the 5-formyl group and the hemi-acetal lactone are crucial for effective inhibition of LAR activity, and are the key pharmacophores of illudalic acid. The fused dimethylcyclopentene ring moiety evidently helps to enhance the potency of illudalic acid against LAR. A preliminary study of the mechanism of action of illudalic acid against LAR was conducted using electrospray ionization mass spectrometry (ESI-MS) and molecular docking techniques. The results are in full agreement with the described mechanism.
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Affiliation(s)
- Qing Ling
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, PR China
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23
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Haapasalo A, Kim DY, Carey BW, Turunen MK, Pettingell WH, Kovacs DM. Presenilin/gamma-secretase-mediated cleavage regulates association of leukocyte-common antigen-related (LAR) receptor tyrosine phosphatase with beta-catenin. J Biol Chem 2007; 282:9063-72. [PMID: 17259169 DOI: 10.1074/jbc.m611324200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Leukocyte-common antigen-related (LAR) receptor tyrosine phosphatase regulates cell adhesion and formation of functional synapses and neuronal networks. Here we report that LAR is sequentially cleaved by alpha- and presenilin (PS)/gamma-secretases, which also affect signaling and/or degradation of type-I membrane proteins including the Alzheimer disease-related beta-amyloid precursor protein. Similar to the previously characterized PS/gamma-secretase substrates, inhibition of gamma-secretase activity resulted in elevated LAR C-terminal fragment (LAR-CTF) levels in stably LAR-overexpressing Chinese hamster ovary (CHO) cells, human neuroglioma cells, and mouse cortical neurons endogenously expressing LAR. Furthermore, LAR-CTF levels increased in cells lacking functional PS, indicating that gamma-secretase-mediated cleavage of LAR was PS-dependent. Inhibition of alpha-secretase activity by TAPI-1 treatment blocked LAR-CTF accumulation, demonstrating that prior ectodomain shedding was prerequisite for PS/gamma-secretase-mediated cleavage of LAR. Moreover, we identified the product of PS/gamma-secretase cleavage, LAR intracellular domain (LICD), both in vitro and in cells overexpressing full-length (FL) LAR or LAR-CTFs. LAR localizes to cadherin-beta-catenin-based cellular junctions. Assembly and disassembly of these junctions are regulated by tyrosine phosphorylation. We found that endogenous tyrosine-phosphorylated beta-catenin coimmunoprecipitated with LAR in CHO cells. However, when PS/gamma-secretase activity was inhibited, the association between LAR and beta-catenin significantly diminished. In addition to cell adhesion, beta-catenin is involved in transcriptional regulation. We observed that LICD significantly decreased transcription of cyclin D1, one of the beta-catenin target genes. Thus, our results show that PS/gamma-secretase-mediated cleavage of LAR controls LAR-beta-catenin interaction, suggesting an essential role for PS/gamma-secretase in the regulation of LAR signaling.
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Affiliation(s)
- Annakaisa Haapasalo
- Neurobiology of Disease Laboratory, Genetics and Aging Research Unit, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129, USA
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24
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Yang T, Massa SM, Longo FM. LAR protein tyrosine phosphatase receptor associates with TrkB and modulates neurotrophic signaling pathways. ACTA ACUST UNITED AC 2007; 66:1420-36. [PMID: 17013927 DOI: 10.1002/neu.20291] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The identities of receptor protein tyrosine phosphatases (PTPs) that associate with Trk protein tyrosine kinase (PTK) receptors and modulate neurotrophic signaling are unknown. The leukocyte common antigen-related (LAR) receptor PTP is present in neurons expressing TrkB, and like TrkB is associated with caveolae and regulates survival and neurite outgrowth. We tested the hypothesis that LAR associates with TrkB and regulates neurotrophic signaling in embryonic hippocampal neurons. Coimmunoprecipitation and coimmunostaining demonstrated LAR interaction with TrkB that is increased by BDNF exposure. BDNF neurotrophic activity was reduced in LAR-/- and LAR siRNA-treated LAR+/+ neurons and was augmented in LAR-transfected neurons. In LAR-/- neurons, BDNF-induced activation of TrkB, Shc, AKT, ERK, and CREB was significantly decreased; while in LAR-transfected neurons, BDNF-induced CREB activation was augmented. Similarly, LAR+/+ neurons treated with LAR siRNA demonstrated decreased activation of Trk and AKT. LAR is known to activate the Src PTK by dephosphorylation of its negative regulatory domain and Src transactivates Trk. In LAR-/- neurons, or neurons treated with LAR siRNA, phosphorylation of the Src regulatory domain was increased (indicating Src inactivation), consistent with a role for Src in mediating LAR's ability to up-regulate neurotrophic signaling. Interactions between LAR, TrkB, and Src were further confirmed by the findings that Src coimmunoprecipitated with LAR, that the Src inhibitor PP2 blocked the ability of LAR to augment TrkB signaling, and that siRNA-induced depletion of Src decreased LAR interaction with TrkB. These studies demonstrate that receptor PTPs can associate with Trk complexes and promote neurotrophic signaling and point to receptor PTP-based strategies as a novel approach for modulating neurotrophin function.
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MESH Headings
- Animals
- Blotting, Western/methods
- Brain-Derived Neurotrophic Factor/metabolism
- Brain-Derived Neurotrophic Factor/pharmacology
- Cell Survival/drug effects
- Cells, Cultured
- Culture Media, Conditioned/pharmacology
- Dose-Response Relationship, Drug
- Embryo, Mammalian
- Enzyme Inhibitors/pharmacology
- Gene Expression Regulation/drug effects
- Gene Expression Regulation/genetics
- Gene Expression Regulation/physiology
- Hippocampus/cytology
- Immunoprecipitation/methods
- Mice
- Mice, Knockout
- Mutation/physiology
- Nerve Tissue Proteins/immunology
- Nerve Tissue Proteins/physiology
- Neurons/drug effects
- Neurons/metabolism
- Phosphorylation/drug effects
- Protein Tyrosine Phosphatases/chemistry
- Protein Tyrosine Phosphatases/deficiency
- Protein Tyrosine Phosphatases/genetics
- Protein Tyrosine Phosphatases/immunology
- Protein Tyrosine Phosphatases/physiology
- Pyrimidines/pharmacology
- RNA, Small Interfering/pharmacology
- Receptor, trkB/physiology
- Receptor-Like Protein Tyrosine Phosphatases, Class 2
- Receptor-Like Protein Tyrosine Phosphatases, Class 4
- Receptors, Cell Surface/chemistry
- Receptors, Cell Surface/deficiency
- Receptors, Cell Surface/genetics
- Receptors, Cell Surface/immunology
- Receptors, Cell Surface/physiology
- Signal Transduction/physiology
- Time Factors
- Transfection/methods
- Tyrosine/metabolism
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Affiliation(s)
- Tao Yang
- Department of Neurology, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina 27599, USA
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25
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Tonks NK. Protein tyrosine phosphatases: from genes, to function, to disease. Nat Rev Mol Cell Biol 2006; 7:833-46. [PMID: 17057753 DOI: 10.1038/nrm2039] [Citation(s) in RCA: 1210] [Impact Index Per Article: 67.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The protein tyrosine phosphatase (PTP) superfamily of enzymes functions in a coordinated manner with protein tyrosine kinases to control signalling pathways that underlie a broad spectrum of fundamental physiological processes. In this review, I describe recent breakthroughs in our understanding of the role of the PTPs in the regulation of signal transduction and the aetiology of human disease.
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Affiliation(s)
- Nicholas K Tonks
- Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, New York 11724, USA.
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26
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Siu R, Fladd C, Rotin D. N-cadherin is an in vivo substrate for protein tyrosine phosphatase sigma (PTPsigma) and participates in PTPsigma-mediated inhibition of axon growth. Mol Cell Biol 2006; 27:208-19. [PMID: 17060446 PMCID: PMC1800655 DOI: 10.1128/mcb.00707-06] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Protein tyrosine phosphatase sigma (PTPsigma) belongs to the LAR family of receptor tyrosine phosphatases and was previously shown to negatively regulate axon growth. The substrate for PTPsigma and the effector(s) mediating this inhibitory effect were unknown. Here we report the identification of N-cadherin as an in vivo substrate for PTPsigma. Using brain lysates from PTPsigma knockout mice, in combination with substrate trapping, we identified a hyper-tyrosine-phosphorylated protein of approximately 120 kDa in the knockout animals (relative to sibling controls), which was identified by mass spectrometry and immunoblotting as N-cadherin. beta-Catenin also precipitated in the complex and was also a substrate for PTPsigma. Dorsal root ganglion (DRG) neurons, which highly express endogenous N-cadherin and PTPsigma, exhibited a faster growth rate in the knockout mice than in the sibling controls when grown on laminin or N-cadherin substrata. However, when N-cadherin function was disrupted by an inhibitory peptide or lowering calcium concentrations, the differential growth rate between the knockout and sibling control mice was greatly diminished. These results suggest that the elevated tyrosine phosphorylation of N-cadherin in the PTPsigma(-/-) mice likely disrupted N-cadherin function, resulting in accelerated DRG nerve growth. We conclude that N-cadherin is a physiological substrate for PTPsigma and that N-cadherin (and likely beta-catenin) participates in PTPsigma-mediated inhibition of axon growth.
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Affiliation(s)
- Roberta Siu
- Program in Cell Biology, The Hospital for Sick Children, 555 University Avenue, Toronto M5G 1X8, Ontario, Canada
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27
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Gonzalez-Brito MR, Bixby JL. Differential activities in adhesion and neurite growth of fibronectin type III repeats in the PTP-delta extracellular domain. Int J Dev Neurosci 2006; 24:425-9. [PMID: 17034983 PMCID: PMC1702485 DOI: 10.1016/j.ijdevneu.2006.08.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2006] [Revised: 07/20/2006] [Accepted: 08/29/2006] [Indexed: 01/01/2023] Open
Abstract
The full-length extracellular domain (ECD) of protein tyrosine phosphatase delta (PTP-delta) functions as a ligand to promote cell adhesion and neurite outgrowth; this ECD contains three immunoglobulin (Ig) repeats and eight fibronectin type III (FN III) repeats. However, it is not known which regions of the ECD regulate its ligand functions. Therefore, we constructed and expressed a fusion protein of the PTP-delta ECD lacking FN III repeats 4-8, and tested this protein for neuronal adhesion and neurite-promoting ability. Compared to the full-length isoform, the truncated ECD was poorer at promoting adhesion, but a more potent promoter of neurite growth. The results suggest that distal FN III repeats of PTP-delta are important in adhesive functions, but dispensable for neurite outgrowth promotion. As the predominant isoform of PTP-delta during neural development (type D) also lacks distal FN III repeats, the functional properties we observe may be relevant to periods of axon extension, suggesting that splice variants of receptor PTPs play distinct roles in neural development.
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Affiliation(s)
| | - John L. Bixby
- Molecular & Cellular Pharmacology
- Neurological Surgery, and
- Neuroscience Program The Miami Project to Cure Paralysis University of Miami Miller School of Medicine Lois Pope LIFE Center, Room 4-17 1095 NW 14th Terrace, Miami, Florida 33136
- Address correspondence to: John L. Bixby, The Miami Project to Cure Paralysis, LPLC 4-17, University of Miami School of Medicine, 1095 NW 14 Terrace, Miami, FL 33136, Phone number: 305-243-4874, Fax number: 305-243-3921, e-mail:
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Kirkham DL, Pacey LKK, Axford MM, Siu R, Rotin D, Doering LC. Neural stem cells from protein tyrosine phosphatase sigma knockout mice generate an altered neuronal phenotype in culture. BMC Neurosci 2006; 7:50. [PMID: 16784531 PMCID: PMC1570144 DOI: 10.1186/1471-2202-7-50] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2006] [Accepted: 06/19/2006] [Indexed: 02/07/2023] Open
Abstract
Background The LAR family Protein Tyrosine Phosphatase sigma (PTPσ) has been implicated in neuroendocrine and neuronal development, and shows strong expression in specific regions within the CNS, including the subventricular zone (SVZ). We established neural stem cell cultures, grown as neurospheres, from the SVZ of PTPσ knockout mice and sibling controls to determine if PTPσ influences the generation and the phenotype of the neuronal, astrocyte and oligodendrocyte cell lineages. Results The neurospheres from the knockout mice acquired heterogeneous developmental characteristics and they showed similar morphological characteristics to the age matched siblings. Although Ptprs expression decreases as a function of developmental age in vivo, it remains high with the continual renewal and passage of the neurospheres. Stem cells, progenitors and differentiated neurons, astrocytes and oligodendrocytes all express the gene. While no apparent differences were observed in developing neurospheres or in the astrocytes and oligodendrocytes from the PTPσ knockout mice, the neuronal migration patterns and neurites were altered when studied in culture. In particular, neurons migrated farther from the neurosphere centers and the neurite outgrowth exceeded the length of the neuronal processes from age matched sibling controls. Conclusion Our results imply a specific role for PTPσ in the neuronal lineage, particularly in the form of inhibitory influences on neurite outgrowth, and demonstrate a role for tyrosine phosphatases in neuronal stem cell differentiation.
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Affiliation(s)
- David L Kirkham
- Department of Pathology and Molecular Medicine, McMaster University, Hamilton Ontario, L8N 3Z5, Canada
| | - Laura KK Pacey
- Department of Pathology and Molecular Medicine, McMaster University, Hamilton Ontario, L8N 3Z5, Canada
| | - Michelle M Axford
- Department of Pathology and Molecular Medicine, McMaster University, Hamilton Ontario, L8N 3Z5, Canada
| | - Roberta Siu
- Cell Biology Program, The Hospital for Sick Children and Department of Biochemistry, University of Toronto, Toronto, Ontario, M5G 1X8, Canada
| | - Daniela Rotin
- Cell Biology Program, The Hospital for Sick Children and Department of Biochemistry, University of Toronto, Toronto, Ontario, M5G 1X8, Canada
| | - Laurie C Doering
- Department of Pathology and Molecular Medicine, McMaster University, Hamilton Ontario, L8N 3Z5, Canada
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Xie Y, Massa SM, Ensslen-Craig SE, Major DL, Yang T, Tisi MA, Derevyanny VD, Runge WO, Mehta BP, Moore LA, Brady-Kalnay SM, Longo FM. Protein-tyrosine phosphatase (PTP) wedge domain peptides: a novel approach for inhibition of PTP function and augmentation of protein-tyrosine kinase function. J Biol Chem 2006; 281:16482-92. [PMID: 16613844 DOI: 10.1074/jbc.m603131200] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Inhibition of protein-tyrosine phosphatases (PTPs) counterbalancing protein-tyrosine kinases (PTKs) offers a strategy for augmenting PTK actions. Conservation of PTP catalytic sites limits development of specific PTP inhibitors. A number of receptor PTPs, including the leukocyte common antigen-related (LAR) receptor and PTPmu, contain a wedge-shaped helix-loop-helix located near the first catalytic domain. Helix-loop-helix domains in other proteins demonstrate homophilic binding and inhibit function; therefore, we tested the hypothesis that LAR wedge domain peptides would exhibit homophilic binding, bind to LAR, and inhibit LAR function. Fluorescent beads coated with LAR or PTPmu wedge peptides demonstrated PTP-specific homophilic binding, and LAR wedge peptide-coated beads precipitated LAR protein. Administration of LAR wedge Tat peptide to PC12 cells resulted in increased proliferation, decreased cell death, increased neurite outgrowth, and augmented Trk PTK-mediated responses to nerve growth factor (NGF), a phenotype matching that found in PC12 cells with reduced LAR levels. PTPmu wedge Tat peptide had no effect on PC12 cells but blocked the PTPmu-dependent phenotype of neurite outgrowth of retinal ganglion neurons on a PTPmu substrate, whereas LAR wedge peptide had no effect. The survival- and neurite-promoting effect of the LAR wedge peptide was blocked by the Trk inhibitor K252a, and reciprocal co-immunoprecipitation demonstrated LAR/TrkA association. The addition of LAR wedge peptide inhibited LAR co-immunoprecipitation with TrkA, augmented NGF-induced activation of TrkA, ERK, and AKT, and in the absence of exogenous NGF, induced activation of TrkA, ERK, and AKT. PTP wedge domain peptides provide a unique PTP inhibition strategy and offer a novel approach for augmenting PTK function.
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Affiliation(s)
- Youmei Xie
- Department of Neurology, University of North Carolina, Chapel Hill, NC 27599, USA
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Bernabeu R, Yang T, Xie Y, Mehta B, Ma SY, Longo FM. Downregulation of the LAR protein tyrosine phosphatase receptor is associated with increased dentate gyrus neurogenesis and an increased number of granule cell layer neurons. Mol Cell Neurosci 2006; 31:723-38. [PMID: 16488625 DOI: 10.1016/j.mcn.2006.01.003] [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] [Received: 09/09/2005] [Revised: 12/16/2005] [Accepted: 01/03/2006] [Indexed: 11/18/2022] Open
Abstract
Growth factors stimulating neurogenesis act through protein tyrosine kinases which are counterbalanced by protein tyrosine phosphatases (PTPs); thus, downregulation of progenitor PTP function might provide a novel strategy for promoting neurogenesis. We tested the hypotheses that the leukocyte common antigen-related (LAR) PTP is present in adult dentate gyrus progenitors, and that its downregulation would promote neurogenesis. In adult mice, LAR immunostaining was present in Ki-67- and PCNA-positive subgranular zone cells. At 1 h post-BrdU administration, LAR-/- mice demonstrated an approximately 3-fold increase in BrdU- and PCNA-positive cells, indicating increased progenitor proliferation. At 1 day and 4 weeks following 6 days of BrdU administration, LAR-/- mice exhibited a significant increase in BrdU and NeuN colabeled cells consistent with increased neurogenesis. In association with increased neurogenesis in LAR-/- mice, stereological analysis revealed a significant 37% increase in the number of neurons present in the granule cell layer. In cultured progenitor clones derived from LAR+/+ mice, LAR immunostaining was present in PCNA- and BrdU-positive cells. Progenitor clones derived from adult LAR-/- hippocampus or LAR+/+ clones made LAR-deficient with LAR siRNA demonstrated increased proliferation and, under differentiation conditions, increased proportions of Tuj1- and MAP2-positive cells. These studies introduce LAR as the first PTP found to be expressed in dentate progenitors and point to inhibition of LAR as a potential strategy for promoting neurogenesis. These findings also provide a rare in vivo demonstration of an association between increased dentate neurogenesis and an expanded population of granule cell layer neurons.
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Affiliation(s)
- Ramon Bernabeu
- UNC School of Medicine, Department of Neurology CB7025, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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Yang T, Yin W, Derevyanny VD, Moore LA, Longo FM. Identification of an ectodomain within the LAR protein tyrosine phosphatase receptor that binds homophilically and activates signalling pathways promoting neurite outgrowth. Eur J Neurosci 2006; 22:2159-70. [PMID: 16262654 DOI: 10.1111/j.1460-9568.2005.04403.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Elucidation of mechanisms by which receptor protein tyrosine phosphatases (PTPs) regulate neurite outgrowth will require characterization of ligand-receptor interactions and identification of ligand-induced signalling components mediating neurite outgrowth. The first identified ligand of the leucocyte common antigen-related (LAR) receptor PTP consists of a 99-residue ectodomain isoform, termed LARFN5C, which undergoes homophilic binding to LAR and promotes neurite outgrowth. We employed peptide mapping of LARFN5C to identify an active neurite-promoting domain of LAR. A peptide mimetic consisting of 37 residues (L59) and corresponding to the fifth LAR fibronectin type III (FNIII) domain prevented LARFN5C homophilic binding, demonstrated homophilic binding to itself and promoted neurite outgrowth of mouse E16-17 hippocampal neurons and of dorsal root ganglia explants. Response to L59 was partially lost when using neurons derived from LAR-deficient (-/-) mice or neurons treated with LAR siRNA, consistent with homophilic interaction of L59 with LAR. L59 neurite-promoting activity was decreased in the presence of inhibitors of Src, Trk, PLCgamma, PKC, PI3K and MAPK. L59 activated Src (a known substrate of LAR), FAK and TrkB and also activated downstream signalling intermediates including PKC, ERK, AKT and CREB. BDNF augmented the maximal neurite-promoting activity of L59, a finding consistent with the presence of shared and distinct signalling pathways activated by L59 with BDNF and L59 with TrkB. These studies are the first to identify an ectodomain of LAR (located within the fifth FNIII domain) capable of promoting neurite outgrowth and point to novel approaches for promotion of neurite outgrowth.
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Affiliation(s)
- Tao Yang
- Department of Neurology, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA
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Lorber B, Berry M, Hendriks W, den Hertog J, Pulido R, Logan A. Stimulated regeneration of the crushed adult rat optic nerve correlates with attenuated expression of the protein tyrosine phosphatases RPTPalpha, STEP, and LAR. Mol Cell Neurosci 2005; 27:404-16. [PMID: 15555919 DOI: 10.1016/j.mcn.2004.06.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2003] [Revised: 04/07/2004] [Accepted: 06/23/2004] [Indexed: 11/25/2022] Open
Abstract
We have evaluated the spatial and temporal expression patterns of three protein tyrosine phosphatases (PTPs), receptor PTPalpha (RPTPalpha), striatal enriched phosphatase (STEP), and leucocyte common antigen-related phosphatase (LAR), in the retina and optic nerve (ON) of adult rats in which the crushed ON was either regenerating after retinal ganglion cell (RGC) stimulation with intravitreal peripheral nerve (PN) grafting or lens injury (LI), or not regenerating (no treatment). In intact adult rats, all three PTPs were expressed by RGCs and ON glia. In both the regenerating and non-regenerating models, a postlesion rise in RPTPalpha, STEP, and LAR expression occurred in the RGC somata and in the ON. However, for RPTPalpha and LAR in the RGCs, and for RPTPalpha, STEP, and LAR in the ON, this postlesion increase was attenuated in the regenerating versus the non-regenerating models. ON PTP expression changes were localized to glia in the proximal and distal stumps, and to macrophages and extracellular matrix of the glial scar at the lesion site. Interestingly, neither RPTPalpha, STEP, nor LAR localized to intact or regenerating axons. One explanation of these findings is that RPTPalpha and LAR may modulate RGC survival, and that RPTPalpha, STEP, and LAR may modulate axon growth.
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Affiliation(s)
- Barbara Lorber
- Molecular Neuroscience, Department of Medicine, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom
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Sajnani G, Aricescu AR, Jones EY, Gallagher J, Alete D, Stoker A. PTPσ promotes retinal neurite outgrowth non-cell-autonomously. ACTA ACUST UNITED AC 2005; 65:59-71. [PMID: 16003721 DOI: 10.1002/neu.20175] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The receptor-like protein tyrosine phosphatase (RPTP) PTPsigma controls the growth and targeting of retinal axons, both in culture and in ovo. Although the principal actions of PTPsigma have been thought to be cell-autonomous, the possibility that RPTPs related to PTPsigma also have non-cell-autonomous signaling functions during axon development has also been supported genetically. Here we report that a cell culture substrate made from purified PTPsigma ectodomains supports retinal neurite outgrowth in cell culture. We show that a receptor for PTPsigma must exist on retinal axons and that binding of PTPsigma to this receptor does not require the known, heparin binding properties of PTPsigma. The neurite-promoting potential of PTPsigma ectodomains requires a basic amino acid domain, previously demonstrated in vitro as being necessary for ligand binding by PTPsigma. Furthermore, we demonstrate that heparin and oligosaccharide derivatives as short as 8mers, can specifically block neurite outgrowth on the PTPsigma substrate, by competing for binding to this same domain. This is the first direct evidence of a non-cell-autonomous, neurite-promoting function of PTPsigma and of a potential role for heparin-related oligosaccharides in modulating neurite promotion by an RPTP.
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Affiliation(s)
- Gustavo Sajnani
- Neural Development Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UK
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Ensslen-Craig SE, Brady-Kalnay SM. Receptor protein tyrosine phosphatases regulate neural development and axon guidance. Dev Biol 2004; 275:12-22. [PMID: 15464569 DOI: 10.1016/j.ydbio.2004.08.009] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2004] [Revised: 08/05/2004] [Accepted: 08/08/2004] [Indexed: 01/06/2023]
Abstract
The regulation of tyrosine phosphorylation is recognized as an important developmental mechanism. Both addition and removal of phosphate moieties on tyrosine residues are tightly regulated during development. Originally, most attention focused on the role of tyrosine kinases during development, but more recently, the developmental importance of tyrosine phosphatases has been gaining interest. Receptor protein tyrosine phosphatases (RPTPs) are of particular interest to developmental biologists because the extracellular domains of RPTPs are similar to those of cell adhesion molecules (CAMs). This suggests that RPTPs may have functions in development similar to CAMs. This review focuses on the role of RPTPs in development of the nervous system in processes such as axon guidance, synapse formation, and neural tissue morphogenesis.
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Affiliation(s)
- Sonya E Ensslen-Craig
- Department of Neurosciences, Case Western Reserve University, School of Medicine, Cleveland, OH 44106-4960, USA
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Chagnon MJ, Uetani N, Tremblay ML. Functional significance of the LAR receptor protein tyrosine phosphatase family in development and diseases. Biochem Cell Biol 2004; 82:664-75. [PMID: 15674434 DOI: 10.1139/o04-120] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The protein tyrosine phosphatases (PTPs) have emerged as critical players in diverse cellular functions. The focus of this review is the leukocyte common antigen-related (LAR) subfamily of receptor PTPs (RPTPs). This subfamily is composed of three vertebrate homologs, LAR, RPTP-sigma, and RPTP-delta, as well as few invertebrates orthologs such as Dlar. LAR-RPTPs have a predominant function in nervous system development that is conserved throughout evolution. Proteolytic cleavage of LAR-RPTP proproteins results in the noncovalent association of an extracellular domain resembling cell adhesion molecules and intracellular tandem PTPs domains, which is likely regulated via dimerization. Their receptor-like structures allow them to sense the extracellular environment and transduce signals intracellularly via their cytosolic PTP domains. Although many interacting partners of the LAR-RPTPs have been identified and suggest a role for the LAR-RPTPs in actin remodeling, very little is known about the mechanisms of action of RPTPs. LAR-RPTPs recently raised a lot of interest when they were shown to regulate neurite growth and nerve regeneration in transgenic animal models. In addition, LAR-RPTPs have also been implicated in metabolic regulation and cancer. This RPTP subfamily is likely to become important as drug targets in these various human pathologies, but further understanding of their complex signal transduction cascades will be required.Key words: protein tyrosine phosphatase, LAR, signal transduction, nervous system development.
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Affiliation(s)
- Mélanie J Chagnon
- McGill Cancer Centre and Department of Biochemistry, McGill University, McIntyre Medical Sciences Building, 3655 Promenade Sir-William-Osler, Room 701, Montréal, QC H3G 1Y6, Canada
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