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Windheim M, Reubold TF, Aichane K, Gaestel M, Burgert HG. Enforced Dimerization of CD45 by the Adenovirus E3/49K Protein Inhibits T Cell Receptor Signaling. J Virol 2023; 97:e0189822. [PMID: 37125921 PMCID: PMC10231199 DOI: 10.1128/jvi.01898-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Accepted: 04/07/2023] [Indexed: 05/02/2023] Open
Abstract
Human adenoviruses (HAdVs) are widespread pathogens that generally cause mild infections in immunocompetent individuals but severe or even fatal diseases in immunocompromised patients. In order to counteract the host immune defenses, HAdVs encode various immunomodulatory proteins in the early transcription unit 3 (E3). The E3/49K protein is a highly glycosylated type I transmembrane protein uniquely expressed by species D HAdVs. Its N-terminal ectodomain sec49K is released by metalloprotease-mediated shedding at the cell surface and binds to the receptor-like protein tyrosine phosphatase CD45, a critical regulator of leukocyte activation and functions. It remained elusive which domains of CD45 and E3/49K are involved in the interaction and whether such an interaction can also occur on the cell surface with membrane-anchored full-length E3/49K. Here, we show that the two extracellular domains R1 and R2 of E3/49K bind to the same site in the domain d3 of CD45. This interaction enforces the dimerization of CD45, causing the inhibition of T cell receptor signaling. Intriguingly, the membrane-anchored E3/49K appears to be designed like a "molecular fishing rod" using an extended disordered region of E3/49K as a "fishing line" to bridge the distance between the plasma membrane of infected cells and the CD45 binding site on T cells to effectively position the domains R1 and R2 as baits for CD45 binding. This design strongly suggests that both secreted sec49K as well as membrane-anchored full-length E3/49K have immunomodulatory functions. The forced dimerization of CD45 may be applied as a therapeutic strategy in chronic inflammatory disorders and cancer. IMPORTANCE The battle between viruses and their hosts is an ongoing arms race. Whereas the host tries to detect and eliminate the virus, the latter counteracts such antiviral measures to replicate and spread. Adenoviruses have evolved various mechanisms to evade the human immune response. The E3/49K protein of species D adenoviruses mediates the inhibition of immune cell function via binding to the protein tyrosine phosphatase CD45. Here, we show that E3/49K triggers the dimerization of CD45 and thereby inhibits its phosphatase activity. Intriguingly, the membrane-anchored E3/49K seems to be designed like a "molecular fishing rod" with the two CD45 binding domains of E3/49K as baits positioned at the end of an extended disordered region reminiscent of a fishing line. The adenoviral strategy to inhibit CD45 activity by forced dimerization may be used for therapeutic intervention in autoimmune diseases or to prevent graft rejection after transplantation.
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Affiliation(s)
- Mark Windheim
- Institute of Cell Biochemistry, Hannover Medical School, Hannover, Germany
| | - Thomas F. Reubold
- Institute for Biophysical Chemistry, Hannover Medical School, Hannover, Germany
| | - Khadija Aichane
- Institute of Cell Biochemistry, Hannover Medical School, Hannover, Germany
| | - Matthias Gaestel
- Institute of Cell Biochemistry, Hannover Medical School, Hannover, Germany
| | - Hans-Gerhard Burgert
- Institute of Virology, University Medical Center, Albert-Ludwigs-University Freiburg, Freiburg, Germany
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2
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Abstract
Protein Tyrosine Phosphatases reverse cellular signals initiated by growth factors receptors and other tyrosine kinases by dephosphorylating phosphotyrosine on target proteins. The activity of these enzymes is crucial for maintaining cell homeostasis, yet these enzymes have been often dismissed as humble house-keeping proteins. Understandably, mutations and changes in expression patterns of Protein Tyrosine Phosphatases are implicated in tumorigenesis and various carcinomas. The conserved nature of their catalytic domains makes drug discovery a challenging pursuit. In this review, we focus on describing the various classes of Protein Tyrosine Phosphatases and their catalytic domains. We also summarize their role in cancer and neurodegenerative diseases using specific members as the model system. Finally, we explain the dichotomy in the biological role of catalytically active vs the pseudoenzyme forms of Protein Tyrosine Phosphatases in the context of their membrane bound receptor forms. This chapter aims to provide a current understanding of these proteins, in the background of their foundational past research.
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Affiliation(s)
- Colin L Welsh
- Department of Cell and Molecular Pharmacology & Experimental Therapeutics, College of Medicine, Medical University of South Carolina, Charleston, SC, United States
| | - Preeti Pandey
- Department of Cell and Molecular Pharmacology & Experimental Therapeutics, College of Medicine, Medical University of South Carolina, Charleston, SC, United States
| | - Lalima G Ahuja
- Department of Cell and Molecular Pharmacology & Experimental Therapeutics, College of Medicine, Medical University of South Carolina, Charleston, SC, United States; Hollings Cancer Center, Medical University of South Carolina, Charleston, SC, United States.
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3
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Zhang Z, Cai Z, Hou Y, Hu J, He Y, Chen J, Ji K. Enhanced sensitivity of capture IgE‑ELISA based on a recombinant Der f 1/2 fusion protein for the detection of IgE antibodies targeting house dust mite allergens. Mol Med Rep 2019; 19:3497-3504. [PMID: 30896856 PMCID: PMC6472038 DOI: 10.3892/mmr.2019.10050] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 03/06/2019] [Indexed: 12/20/2022] Open
Abstract
The detection of allergen‑specific immunoglobulin (Ig)E is an important method for the diagnosis of IgE‑mediated allergic diseases. The sensitivity of the indirect IgE‑ELISA method against allergen extracts is limited by interference from high IgG titers and low quantities of effectual allergen components in extracts. To overcome these limitations, a novel capture IgE‑ELISA based on a recombinant Der f 1/Der f 2 fusion protein (rDer f 1/2) was developed to enhance the sensitivity to IgEs that bind allergens from the house dust mite (HDM) species Dermatophagoides farina. pET28‑Der f 1/2 was constructed and expressed in Escherichia coli BL21 (DE3) pLysS. The purified fusion protein was evaluated by IgE western blotting, IgE dot blotting and indirect IgE‑ELISA. Capture‑ELISA was performed by coating wells with omalizumab and incubating in series with sera, biotinylated Der f 1/2, horseradish peroxidase‑conjugated streptavidin and 3,3,5,5‑tetramethylbenzidine. The relative sensitivities of indirect‑ELISA and capture‑ELISA for HDM allergen‑specific IgE binding were determined; sera from non‑allergic individuals were used as the control group. rDer f 1/2 was expressed in the form of inclusion bodies comprising refolded protein, which were then purified. It exhibited increased IgE‑specific binding (24/28, 85.8%) than rDer f 1 (21/28, 75.0%) or rDer f 2 (22/28, 78.6%) with HDM‑allergic sera. Furthermore, in a random sample of HDM‑allergic sera (n=71), capture‑ELISA (71/71, 100%) was more sensitive than indirect‑ELISA (68/71, 95.8%) for the detection of HDM‑specific IgEs (P<0.01), indicating that this novel method may be useful for the diagnosis of HDM allergy.
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Affiliation(s)
- Zhen Zhang
- Department of Biochemistry and Molecular Biology, Health Science Center of Shenzhen University, Shenzhen, Guangdong 518035, P.R. China
| | - Zelang Cai
- Department of Biochemistry and Molecular Biology, Health Science Center of Shenzhen University, Shenzhen, Guangdong 518035, P.R. China
| | - Yibo Hou
- Department of Biochemistry and Molecular Biology, Health Science Center of Shenzhen University, Shenzhen, Guangdong 518035, P.R. China
| | - Jiayun Hu
- Department of Biochemistry and Molecular Biology, Health Science Center of Shenzhen University, Shenzhen, Guangdong 518035, P.R. China
| | - Yongshen He
- Department of Biochemistry and Molecular Biology, Health Science Center of Shenzhen University, Shenzhen, Guangdong 518035, P.R. China
| | - Jiajie Chen
- Department of Biochemistry and Molecular Biology, Health Science Center of Shenzhen University, Shenzhen, Guangdong 518035, P.R. China
| | - Kunmei Ji
- Department of Biochemistry and Molecular Biology, Health Science Center of Shenzhen University, Shenzhen, Guangdong 518035, P.R. China
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Lorentzian A, Uzozie A, Lange PF. Origins and clinical relevance of proteoforms in pediatric malignancies. Expert Rev Proteomics 2019; 16:185-200. [PMID: 30700156 DOI: 10.1080/14789450.2019.1575206] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
INTRODUCTION Cancer changes the proteome in complex ways that reach well beyond simple changes in protein abundance. Genomic and transcriptional variations and post-translational protein modification create functional variants of a protein, known as proteoforms. Childhood cancers have fewer genomic alterations but show equally dramatic phenotypic changes as malignant cells in adults. Therefore, unraveling the complexities of the proteome is even more important in pediatric malignancies. Areas covered: In this review, the biological origins of proteoforms and technological advancements in the study of proteoforms are discussed. Particular emphasis is given to their implication in childhood malignancies and the critical role of cancer-specific proteoforms for the next generation of cancer therapies and diagnostics. Expert opinion: Recent advancements in technology have led to a better understanding of the underlying mechanisms of tumorigenesis. This has been critical for the development of more effective and less harmful treatments that are based on direct targeting of altered proteins and deregulated pathways. As proteome coverage and the ability to detect complex proteoforms increase, the most need for change is in data compilation and database availability to mediate high-level data analysis and allow for better functional annotation of proteoforms.
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Affiliation(s)
- Amanda Lorentzian
- a Department of Cell and Developmental Biology , University of British Columbia , Vancouver , BC , Canada.,b Michael Cuccione Childhood Cancer Research Program , BC Children's Hospital Research Institute , Vancouver , BC , Canada
| | - Anuli Uzozie
- b Michael Cuccione Childhood Cancer Research Program , BC Children's Hospital Research Institute , Vancouver , BC , Canada.,c Department of Pathology and Laboratory Medicine , University of British Columbia , Vancouver , BC , Canada
| | - Philipp F Lange
- a Department of Cell and Developmental Biology , University of British Columbia , Vancouver , BC , Canada.,b Michael Cuccione Childhood Cancer Research Program , BC Children's Hospital Research Institute , Vancouver , BC , Canada.,c Department of Pathology and Laboratory Medicine , University of British Columbia , Vancouver , BC , Canada
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5
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Heil HS, Schreiber B, Götz R, Emmerling M, Dabauvalle MC, Krohne G, Höfling S, Kamp M, Sauer M, Heinze KG. Sharpening emitter localization in front of a tuned mirror. LIGHT, SCIENCE & APPLICATIONS 2018; 7:99. [PMID: 30534368 PMCID: PMC6279778 DOI: 10.1038/s41377-018-0104-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Revised: 11/13/2018] [Accepted: 11/13/2018] [Indexed: 05/23/2023]
Abstract
Single-molecule localization microscopy (SMLM) aims for maximized precision and a high signal-to-noise ratio1. Both features can be provided by placing the emitter in front of a metal-dielectric nanocoating that acts as a tuned mirror2-4. Here, we demonstrate that a higher photon yield at a lower background on biocompatible metal-dielectric nanocoatings substantially improves SMLM performance and increases the localization precision by up to a factor of two. The resolution improvement relies solely on easy-to-fabricate nanocoatings on standard glass coverslips and is spectrally and spatially tunable by the layer design and wavelength, as experimentally demonstrated for dual-color SMLM in cells.
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Affiliation(s)
- Hannah S. Heil
- Rudolf Virchow Center, Research Center for Experimental Biomedicine, University of Würzburg, Josef-Schneider-Str.2, 97080 Würzburg, Germany
| | - Benjamin Schreiber
- Rudolf Virchow Center, Research Center for Experimental Biomedicine, University of Würzburg, Josef-Schneider-Str.2, 97080 Würzburg, Germany
| | - Ralph Götz
- Department of Biotechnology and Biophysics, Biozentrum, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Monika Emmerling
- Technische Physik, Physikalisches Institut and Wilhelm Conrad Röntgen-Center for Complex Material Systems, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Marie-Christine Dabauvalle
- Division of Electron Microscopy, Biozentrum, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Georg Krohne
- Division of Electron Microscopy, Biozentrum, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Sven Höfling
- Technische Physik, Physikalisches Institut and Wilhelm Conrad Röntgen-Center for Complex Material Systems, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS UK
| | - Martin Kamp
- Technische Physik, Physikalisches Institut and Wilhelm Conrad Röntgen-Center for Complex Material Systems, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Markus Sauer
- Department of Biotechnology and Biophysics, Biozentrum, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Katrin G. Heinze
- Rudolf Virchow Center, Research Center for Experimental Biomedicine, University of Würzburg, Josef-Schneider-Str.2, 97080 Würzburg, Germany
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6
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CD45 in human physiology and clinical medicine. Immunol Lett 2018; 196:22-32. [PMID: 29366662 DOI: 10.1016/j.imlet.2018.01.009] [Citation(s) in RCA: 135] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Revised: 01/18/2018] [Accepted: 01/19/2018] [Indexed: 01/20/2023]
Abstract
CD45 is an evolutionary highly conserved receptor protein tyrosine phosphatase exclusively expressed on all nucleated cells of the hematopoietic system. It is characterized by the expression of several isoforms, specific to a certain cell type and the developmental or activation status of the cell. CD45 is one of the key players in the initiation of T cell receptor signaling by controlling the activation of the Src family protein-tyrosine kinases Lck and Fyn. CD45 deficiency results in T- and B-lymphocyte dysfunction in the form of severe combined immune deficiency. It also plays a significant role in autoimmune diseases and cancer as well as in infectious diseases including fungal infections. The knowledge collected on CD45 biology is rather vast, but it remains unclear whether all findings in rodent immune cells also apply to human CD45. This review focuses on human CD45 expression and function and provides an overview on its ligands and role in human pathology.
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7
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Abrie JA, Molero C, Ariño J, Strauss E. Complex stability and dynamic subunit interchange modulates the disparate activities of the yeast moonlighting proteins Hal3 and Vhs3. Sci Rep 2015; 5:15774. [PMID: 26514574 PMCID: PMC4626798 DOI: 10.1038/srep15774] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Accepted: 10/05/2015] [Indexed: 11/17/2022] Open
Abstract
Saccharomyces cerevisiae Hal3 and Vhs3 are moonlighting proteins, acting both as inhibitors of the serine/threonine protein phosphatase Ppz1 and as subunits (together with Cab3) of the unique heterotrimeric phosphopantothenoylcysteine decarboxylase (PPCDC) enzyme of Hemiascomycetous yeast. Both these roles are essential: PPCDC catalyses the third step of coenzyme A biosynthesis, while Ppz1 inhibition is required for regulation of monovalent cation homeostasis. However, the mechanisms by which these proteins’ disparate activities are regulated are not well understood. The PPCDC domains (PDs) of Hal3, Vhs3 and Cab3 constitute the minimum requirement for these proteins to show both PPCDC activity and, in the case of Hal3 and Vhs3, to bind to Ppz1. Using these PD proteins as a model system to study the possibility of dynamic interchange between these roles, we provide evidence that Hal3 binds Ppz1 as a monomer (1:1 stoichiometry), requiring it to de-oligomerize from its usual homo- and heterotrimeric states (the latter having PPCDC activity). This de-oligomerization is made possible by structural features that set Hal3 apart from Vhs3, increasing its ability to undergo monomer exchange. These findings suggest that oligomer interchange may be a significant factor in the functional regulation of these proteins and their various unrelated (moonlighting) functions.
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Affiliation(s)
- J Albert Abrie
- Department of Biochemistry, Stellenbosch University, South Africa
| | - Cristina Molero
- Institut de Biotecnologia i Biomedicina and Departament de Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona, Spain
| | - Joaquín Ariño
- Institut de Biotecnologia i Biomedicina and Departament de Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona, Spain
| | - Erick Strauss
- Department of Biochemistry, Stellenbosch University, South Africa
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8
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Filatov AV, Meshkova TD, Mazurov DV. Epitope mapping of lymphocyte phosphatase-associated phosphoprotein. BIOCHEMISTRY (MOSCOW) 2015; 79:1397-404. [PMID: 25716735 DOI: 10.1134/s0006297914120153] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Lymphocyte phosphatase-associated phosphoprotein (LPAP) is a transmembrane protein with unknown function. The available data on its close association with phosphatase CD45 and its phosphorylation depending on cell activation suggest that LPAP can play a significant role in the antigenic stimulation of lymphocytes. We have localized three antigenic epitopes of the LPAP molecule that can be detected using monoclonal antibodies prepared earlier. Experiments on reactions of antibodies with point mutants and shortened forms of the LPAP protein revealed regions of the amino acid sequence that correspond to the epitopes recognized by the antibodies.
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Affiliation(s)
- A V Filatov
- Institute of Immunology, Federal Medical-Biological Agency, Moscow, 115478, Russia.
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9
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Filatov A, Kruglova N, Meshkova T, Mazurov D. Lymphocyte phosphatase-associated phosphoprotein proteoforms analyzed using monoclonal antibodies. Clin Transl Immunology 2015; 4:e44. [PMID: 26682052 PMCID: PMC4673442 DOI: 10.1038/cti.2015.22] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Revised: 09/03/2015] [Accepted: 09/03/2015] [Indexed: 11/09/2022] Open
Abstract
Phosphatase CD45 regulates the activation of lymphocytes by controlling the level of receptor and signal molecule phosphorylation. However, it remains unknown which molecules mediate the phosphatase activity of CD45. A candidate for such a molecule is a small transmembrane adapter protein called lymphocyte phosphatase-associated phosphoprotein (LPAP). LPAP forms a supramolecular complex that consists of not only CD45 molecule but also CD4 and Lck kinase. The function of LPAP has not been defined clearly. In our study, we determined the pattern of LPAP expression in various cell types and characterized its proteoforms using new monoclonal antibodies generated against the intracellular portion of the protein. We show that LPAP is a pan-lymphocyte marker, and its expression in cells correlates with the expression of CD45. The majority of T, B and NK cells express high levels of LPAP, whereas monocytes, granulocytes, monocyte-derived dendritic cells, platelets and red blood cells are negative for LPAP. Using one- and two-dimensional protein gel electrophoresis, we demonstrate that LPAP has at least four sites of phosphorylation. The resting cells express at least six different LPAP phosphoforms representing mono-, di- and tri-phosphorylated LPAP. T and B cells differ in the distribution of the protein between phosphoforms. The activation of lymphocytes with PMA reduces the diversity of phosphorylated forms. Our experiments on Lck-deficient Jurkat cells show that Lck kinase is not involved in LPAP phosphorylation. Thus, LPAP is a dynamically phosphorylated protein, the function of which can be understood, when all phosphosites and kinases involved in its phosphorylation will be identified.
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Affiliation(s)
- Alexander Filatov
- Laboratory of Immunochemistry, Institute of Immunology , Moscow, Russia
| | - Natalia Kruglova
- Faculty of Biology, Lomonosov Moscow State University , Moscow, Russia
| | - Tatiana Meshkova
- Faculty of Biology, Lomonosov Moscow State University , Moscow, Russia
| | - Dmitriy Mazurov
- Laboratory of Immunochemistry, Institute of Immunology , Moscow, Russia
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10
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Ahuja LG, Gopal B. Bi-domain protein tyrosine phosphatases reveal an evolutionary adaptation to optimize signal transduction. Antioxid Redox Signal 2014; 20:2141-59. [PMID: 24206235 DOI: 10.1089/ars.2013.5721] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
SIGNIFICANCE The bi-domain protein tyrosine phosphatases (PTPs) exemplify functional evolution in signaling proteins for optimal spatiotemporal signal transduction. Bi-domain PTPs are products of gene duplication. The catalytic activity, however, is often localized to one PTP domain. The inactive PTP domain adopts multiple functional roles. These include modulation of catalytic activity, substrate specificity, and stability of the bi-domain enzyme. In some cases, the inactive PTP domain is a receptor for redox stimuli. Since multiple bi-domain PTPs are concurrently active in related cellular pathways, a stringent regulatory mechanism and selective cross-talk is essential to ensure fidelity in signal transduction. RECENT ADVANCES The inactive PTP domain is an activator for the catalytic PTP domain in some cases, whereas it reduces catalytic activity in other bi-domain PTPs. The relative orientation of the two domains provides a conformational rationale for this regulatory mechanism. Recent structural and biochemical data reveal that these PTP domains participate in substrate recruitment. The inactive PTP domain has also been demonstrated to undergo substantial conformational rearrangement and oligomerization under oxidative stress. CRITICAL ISSUES AND FUTURE DIRECTIONS The role of the inactive PTP domain in coupling environmental stimuli with catalytic activity needs to be further examined. Another aspect that merits attention is the role of this domain in substrate recruitment. These aspects have been poorly characterized in vivo. These lacunae currently restrict our understanding of neo-functionalization of the inactive PTP domain in the bi-domain enzyme. It appears likely that more data from these research themes could form the basis for understanding the fidelity in intracellular signal transduction.
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Affiliation(s)
- Lalima Gagan Ahuja
- 1 Molecular Biophysics Unit, Indian Institute of Science , Bangalore, India
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11
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Böhmer F, Szedlacsek S, Tabernero L, Ostman A, den Hertog J. Protein tyrosine phosphatase structure-function relationships in regulation and pathogenesis. FEBS J 2013; 280:413-31. [PMID: 22682070 DOI: 10.1111/j.1742-4658.2012.08655.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Protein phosphorylation on tyrosine residues is tightly controlled by protein tyrosine phosphatases (PTPs) at multiple levels: spatio-temporal expression, subcellular localization and post-translational modification. Structural and functional analysis of the PTP domains has provided insight into catalysis and regulatory mechanisms that control the enzymatic activity. Understanding the molecular basis of PTP regulation is of fundamental importance to dissect the pleiotropic effect of these enzymes in both health and disease. Here, we review recent insights into the regulation of receptor-like PTPs by extracellular ligands and into regulation by reversible oxidation that impairs catalysis directly. The physiological roles of PTPs are essential in homeostasis in eukaryotic cells and pertubation of their functional attributes causes different disease states. As an example, we discuss recent findings indicating how inappropriate oxidation of PTPs in cancer cells may contribute to cell transformation. On the other hand, PTPs from many pathogens are key virulence factors and manipulate signalling pathways in the host cells to promote invasion and survival of the microorganisms. This research area has received relatively little attention but has advanced remarkably. We review the structural features of pathogenic PTPs, their similarities and differences with eukaryotic PTPs, and the possible exploitation of this knowledge for therapeutic intervention.
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Affiliation(s)
- Frank Böhmer
- Center for Molecular Biomedicine, Jena University Hospital, Jena, Germany
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12
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Mohebiany AN, Nikolaienko RM, Bouyain S, Harroch S. Receptor-type tyrosine phosphatase ligands: looking for the needle in the haystack. FEBS J 2012; 280:388-400. [PMID: 22682003 DOI: 10.1111/j.1742-4658.2012.08653.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Reversible protein phosphorylation plays a pivotal role in intercellular communication. Together with protein tyrosine kinases, protein tyrosine phosphatases (PTPs) are involved in the regulation of key cellular processes by controlling the phosphorylation levels of diverse effectors. Among PTPs, receptor-like protein tyrosine phosphatases (RPTPs) are involved in important developmental processes, particularly in the formation of the nervous system. Until recently, few ligands had been identified for RPTPs, making it difficult to grasp the effects these receptors have on cellular processes, as well as the mechanisms through which their functions are mediated. However, several potential RPTP ligands have now been identified to provide us with unparalleled insights into RPTP function. In this review, we focus on the nature and biological outcomes of these extracellular interactions between RPTPs and their associated ligands.
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Affiliation(s)
- Alma N Mohebiany
- Department of Neuroscience, Institut Pasteur de Paris, Paris, France
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13
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Hower AE, Beltran PJ, Bixby JL. Dimerization of tyrosine phosphatase PTPRO decreases its activity and ability to inactivate TrkC. J Neurochem 2009; 110:1635-47. [PMID: 19573017 DOI: 10.1111/j.1471-4159.2009.06261.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Receptor-protein tyrosine phosphatases (RPTPs), like receptor tyrosine kinases, regulate neuronal differentiation. While receptor tyrosine kinases are dimerized and activated by extracellular ligands, the extent to which RPTPs dimerize, and the effects of dimerization on phosphatase activity, are poorly understood. We have examined a neuronal type III RPTP, PTPRO; we find that PTPRO can form dimers in living cells, and that disulfide linkages in PTPROs intracellular domain likely regulate dimerization. Dimerization of PTPROs transmembrane and intracellular domains, achieved by ligand binding to a chimeric fusion protein, decreases activity toward artificial peptides and toward a putative substrate, tropomyosin-related kinase C (TrkC). Dephosphorylation of TrkC by PTPRO may be physiologically relevant, as it is efficient, and TrkC and PTPRO can be co-precipitated from transfected cells. Inhibition of PTPROs phosphatase activity by dimerization is interesting, as dimerization of a related RPTP, CD148/PTPRJ, increases activity. Thus, our results suggest a complex relationship between dimerization and activity in type III RPTPs.
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14
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Hermiston ML, Zikherman J, Zhu JW. CD45, CD148, and Lyp/Pep: critical phosphatases regulating Src family kinase signaling networks in immune cells. Immunol Rev 2009; 228:288-311. [PMID: 19290935 PMCID: PMC2739744 DOI: 10.1111/j.1600-065x.2008.00752.x] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Reciprocal regulation of tyrosine phosphorylation by protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs) is central to normal immune cell function. Disruption of the equilibrium between PTK and PTP activity can result in immunodeficiency, autoimmunity, or malignancy. Src family kinases (SFKs) play a central role in both immune cell function and disease due to their proximal position in numerous signal transduction cascades including those emanating from integrin, T and B-cell antigen receptors, Fc, growth factor, and cytokine receptors. Given that tight regulation of SFKs activity is critical for appropriate responses to stimulation of these various signaling pathways, it is perhaps not surprising that multiple PTPs are involved in their regulation. Here, we focus on the role of three phosphatases, CD45, CD148, and LYP/PEP, which are critical regulators of SFKs in hematopoietic cells. We review our current understanding of their structures, expression, functions in different hematopoietic cell subsets, regulation, and putative roles in disease. Finally, we discuss remaining questions that must be addressed if we are to have a clearer understanding of the coordinated regulation of tyrosine phosphorylation and signaling networks in hematopoietic cells and how they could potentially be manipulated therapeutically in disease.
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Affiliation(s)
- Michelle L. Hermiston
- Department of Pediatrics, University of California, San Francisco, San Francisco, CA 94143, Phone: 415-476-2413, Fax: 415-502-5127,
| | - Julie Zikherman
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, Phone: 415-476-4115, Fax: 502-5081, ;
| | - Jing W. Zhu
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, Phone: 415-476-4115, Fax: 502-5081, ;
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15
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Differential impact of the CD45 juxtamembrane wedge on central and peripheral T cell receptor responses. Proc Natl Acad Sci U S A 2009; 106:546-51. [PMID: 19129486 DOI: 10.1073/pnas.0811647106] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
The cooperative activity of protein tyrosine kinases and phosphatases plays a central role in regulation of T cell receptor (TCR) signal strength. Perturbing this balance, and thus the threshold for TCR signals, has profound impacts on T cell development and function. We previously generated mice containing a point mutation in the juxtamembrane wedge of the receptor-like protein tyrosine phosphatase CD45. Demonstrating the critical negative regulatory function of the wedge, the CD45 E613R (WEDGE) mutation led to a lymphoproliferative disorder (LPD) and a lupus-like autoimmune syndrome. Using genetic, cellular, and biochemical approaches, we now demonstrate that the CD45 wedge influences T cell development and function. Consistent with increased TCR signal strength, WEDGE mice have augmented positive selection and enhanced sensitivity to the CD4-mediated disease experimental autoimmune encephalitis (EAE). These correspond with hyperresponsive calcium and pERK responses to TCR stimulation in thymocytes, but surprisingly, not in peripheral T cells, where these responses are actually depressed. Together, the data support a role for the CD45 wedge in regulation of T cell responses in vivo and suggest that its effects depend on cellular context.
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Groen A, Overvoorde J, van der Wijk T, den Hertog J. Redox regulation of dimerization of the receptor protein-tyrosine phosphatases RPTPα, LAR, RPTPμ and CD45. FEBS J 2008; 275:2597-604. [DOI: 10.1111/j.1742-4658.2008.06407.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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17
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Abstract
Protein-tyrosine phosphatases are tightly controlled by various mechanisms, ranging from differential expression in specific cell types to restricted subcellular localization, limited proteolysis, post-translational modifications affecting intrinsic catalytic activity, ligand binding and dimerization. Here, we review the regulatory mechanisms found to control the classical protein-tyrosine phosphatases.
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Rayapureddi JP, Hegde RS. Branchio-oto-renal syndrome associated mutations in Eyes Absent 1 result in loss of phosphatase activity. FEBS Lett 2006; 580:3853-9. [PMID: 16797546 DOI: 10.1016/j.febslet.2006.06.009] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2006] [Revised: 05/30/2006] [Accepted: 06/01/2006] [Indexed: 11/30/2022]
Abstract
The Eyes Absent (Eya) proteins are tyrosine phosphatases and transcriptional activators involved in cell-fate determination and organ development. Mutations in the gene encoding Eya homologue 1 have been implicated in the multi-organ developmental disorder branchio-oto-renal syndrome (BOR) and in ocular defects. Here we report that BOR-associated mutations lead to a loss of phosphatase activity in Eya1 proteins, while mutations associated with ocular defects yield Eya1 proteins with near normal levels of phosphatase activity. Furthermore we demonstrate that the N-terminal domain attenuates the catalytic activity of Eya suggesting a mechanism of regulation.
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Affiliation(s)
- Jayanagendra P Rayapureddi
- Cincinnati Children's Hospital Medical Center, Division of Developmental Biology, University of Cincinnati School of Medicine, Department of Pediatrics, 3333 Burnet Avenue, Cincinnati, OH 45229, United States
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Hermiston ML, Tan AL, Gupta VA, Majeti R, Weiss A. The juxtamembrane wedge negatively regulates CD45 function in B cells. Immunity 2006; 23:635-47. [PMID: 16356861 DOI: 10.1016/j.immuni.2005.11.001] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2005] [Revised: 09/08/2005] [Accepted: 11/09/2005] [Indexed: 12/22/2022]
Abstract
CD45 is a receptor-like protein tyrosine phosphatase highly expressed on all nucleated hematopoietic cells. We previously generated mice containing a point mutation in the juxtamembrane wedge of CD45. Demonstrating the critical negative regulatory function of the wedge, the CD45 E613R mutation led to a lymphoproliferative disorder (LPD) and a lupus-like autoimmune syndrome. Here we show the central role of B cells in this phenotype. Genetic elimination of B cells, but not T cells, ablates the LPD. In contrast to CD45-deficient B cells, the E613R mutation generates hyperresponsive B cells. Comparison of CD45-deficient and CD45 E613R mice reveals dichotomous effects of these mutations on B cell development. Together, the results support a role for CD45 as a rheostat, with both positive and negative regulatory functions, that fine-tunes the signal transduction threshold at multiple checkpoints in B cell development.
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Affiliation(s)
- Michelle L Hermiston
- Department of Pediatrics, University of California, San Francisco, San Francisco, California 94143, USA
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20
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Suh HS, Kim MO, Lee SC. Inhibition of granulocyte-macrophage colony-stimulating factor signaling and microglial proliferation by anti-CD45RO: role of Hck tyrosine kinase and phosphatidylinositol 3-kinase/Akt. THE JOURNAL OF IMMUNOLOGY 2005; 174:2712-9. [PMID: 15728479 DOI: 10.4049/jimmunol.174.5.2712] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Increasing evidence suggests that CD45, a transmembrane protein tyrosine phosphatase, is an important modulator of macrophage activation. Microglia, resident brain macrophages, express CD45 and proliferate under pathologic conditions. In this study, we examined the role of CD45 in modulating GM-CSF-induced proliferation and signal transduction in primary human microglial cultures. Soluble, but not immobilized anti-CD45RO induced tyrosine phosphatase activity and inhibited GM-CSF-induced microglial proliferation. Microglial proliferation was also inhibited by PP2 (Src inhibitor), LY294002 (PI3K inhibitor), and U0126 (MEK inhibitor). GM-CSF induced phosphorylation of Jak2, Stat5, Hck (the myeloid-restricted Src kinase), Akt, Stat3, and Erk MAPKs in microglia. Of these, anti-CD45RO inhibited phosphorylation of Hck and Akt, and PP2 inhibited phosphorylation of Hck and Akt. In a macrophage cell line stably overexpressing wild-type or kinase-inactive Hck, GM-CSF increased proliferation of the control (empty vector) and wild-type but not kinase-inactive cells, and this was inhibited by anti-CD45RO. Together, these results demonstrate that, in macrophages, Hck tyrosine kinase is activated by GM-CSF, and that Hck plays a pivotal role in cell proliferation and survival by activating the PI3K/Akt pathway. Ab-mediated activation of macrophage and microglial CD45 tyrosine phosphatase may have therapeutic implications for CNS inflammatory diseases.
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Affiliation(s)
- Hyeon-Sook Suh
- Department of Pathology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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21
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Shimizu J, Iida R, Sato Y, Moriizumi E, Nishikawa A, Ishida Y. Cross-Linking of CD45 on Suppressive/Regulatory T Cells Leads to the Abrogation of Their Suppressive Activity In Vitro. THE JOURNAL OF IMMUNOLOGY 2005; 174:4090-7. [DOI: 10.4049/jimmunol.174.7.4090] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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22
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den Hertog J, Groen A, van der Wijk T. Redox regulation of protein-tyrosine phosphatases. Arch Biochem Biophys 2005; 434:11-5. [PMID: 15629103 DOI: 10.1016/j.abb.2004.05.024] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2004] [Revised: 05/12/2004] [Indexed: 10/26/2022]
Abstract
The protein-tyrosine phosphatases (PTPs) form a large family of signaling proteins with essential functions in embryonic development and adult physiology. The PTPs are characterized by an absolutely conserved catalytic site cysteine with a low pK(a) due to its microenvironment, making it vulnerable to oxidation. PTPs are differentially oxidized and inactivated in vitro and in living cells. Many cellular stimuli induce a shift in the cellular redox state towards oxidation and evidence is accumulating that at least part of the cellular responses to these stimuli are due to specific, transient inactivation of PTPs, indicating that PTPs are important sensors of the cellular redox state.
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Affiliation(s)
- Jeroen den Hertog
- Hubrecht Laboratory, Netherlands Institute for Developmental Biology, Uppsalalaan 8, 3584 CT Utrecht, The Netherlands.
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23
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McNeill L, Cassady RL, Sarkardei S, Cooper JC, Morgan G, Alexander DR. CD45 isoforms in T cell signalling and development. Immunol Lett 2004; 92:125-34. [PMID: 15081536 DOI: 10.1016/j.imlet.2003.10.018] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2003] [Accepted: 10/24/2003] [Indexed: 12/31/2022]
Abstract
The CD45 phosphotyrosine phosphatase is expressed on T cells as multiple isoforms due to alternative splicing. The panoply of isoforms expressed is tightly regulated during T cell development and on mature peripheral T cell subsets following activation. We describe the analysis of comparative CD45 isoform expression levels on thymic and T cell subsets from the C57BL/6 mouse. Only four isoforms were expressed at significant protein levels: CD45R0, CD45RB, CD45RBC and CD45RABC, although trace amounts of others may be present. The expression of CD45RBC was about nine-fold higher on CD8(+) than on CD4(+) peripheral T cells, whereas CD45R0 expression was higher on CD4(+) T cells. We provide a general overview of the current models that have been proposed to explain the molecular actions of the different CD45 isoforms. Achieving a thorough understanding of the biological reasons for the existence and tight regulation of CD45 isoform expression in immune cells remains one of the outstanding challenges in the CD45 research field.
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Affiliation(s)
- Louise McNeill
- Laboratory of Lymphocyte Signalling and Development, The Babraham Institute, Babraham, Cambridge CB2 4AT, UK
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24
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Takeda A, Matsuda A, Paul RMJ, Yaseen NR. CD45-associated protein inhibits CD45 dimerization and up-regulates its protein tyrosine phosphatase activity. Blood 2004; 103:3440-7. [PMID: 14715639 DOI: 10.1182/blood-2003-06-2083] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractCD45, a receptor-like protein tyrosine phosphatase (PTP), plays an essential role in lymphocyte development and immune responses. Recent evidence suggests that dimerization of CD45 down-regulates its function. However, the mechanisms by which CD45 dimerization is regulated remain unclear, and there is no direct evidence that the PTP activity of CD45 dimers is less than that of monomers. CD45 in lymphocytes associates with CD45-AP (CD45-associated protein). Here we show that T cells from CD45-AP-null mice have a much higher level of CD45 dimers than those of wild-type mice, suggesting that CD45-AP inhibits CD45 dimer formation. This was confirmed with the use of a novel CD45-AP-null T-cell line, ALST-1, that we established from a spontaneous thymic tumor found in a CD45-AP-null mouse. Transfected CD45-AP inhibited CD45 dimer formation in ALST-1 cells in proportion to the amount of CD45-AP expressed. Finally, with the use of microsomal fractions from both mouse thymocytes and ALST-1 transfectants, the PTP activity of CD45 was found to be significantly lower in CD45-AP-negative cells than in CD45-AP-positive cells. Therefore, our results support a model in which binding of CD45-AP to inactive CD45 dimers converts them to active monomers. (Blood. 2004;103:3440-3447)
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Affiliation(s)
- Akiko Takeda
- Department of Pathology, Feinberg School of Medicine, Northwestern University, Ward 6-011, 303 E Chicago Ave, Chicago, IL 60611, USA.
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25
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Cismasiu VB, Denes SA, Reiländer H, Michel H, Szedlacsek SE. The MAM (meprin/A5-protein/PTPmu) domain is a homophilic binding site promoting the lateral dimerization of receptor-like protein-tyrosine phosphatase mu. J Biol Chem 2004; 279:26922-31. [PMID: 15084579 DOI: 10.1074/jbc.m313115200] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The MAM (meprin/A5-protein/PTPmu) domain is present in numerous proteins with diverse functions. PTPmu belongs to the MAM-containing subclass of protein-tyrosine phosphatases (PTP) able to promote cell-to-cell adhesion. Here we provide experimental evidence that the MAM domain is a homophilic binding site of PTPmu. We demonstrate that the MAM domain forms oligomers in solution and binds to the PTPmu ectodomain at the cell surface. The presence of two disulfide bridges in the MAM molecule was evidenced and their integrity was found to be essential for MAM homophilic interaction. Our data also indicate that PTPmu ectodomain forms oligomers and mediates the cellular adhesion, even in the absence of MAM domain homophilic binding. Reciprocally, MAM is able to interact homophilically in the absence of ectodomain trans binding. The MAM domain therefore contains independent cis and trans interaction sites and we predict that its main role is to promote lateral dimerization of PTPmu at the cell surface. This finding contributes to the understanding of the signal transduction mechanism in MAM-containing PTPs.
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Affiliation(s)
- Valeriu B Cismasiu
- Department of Enzymology, Institute of Biochemistry, Spl. Independentei 296, Bucharest 060031, Romania
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26
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Abstract
Regulation of tyrosine phosphorylation is a critical control point for integration of environmental signals into cellular responses. This regulation is mediated by the reciprocal actions of protein tyrosine kinases and phosphatases. CD45, the first and prototypic receptor-like protein tyrosine phosphatase, is expressed on all nucleated hematopoietic cells and plays a central role in this process. Studies of CD45 mutant cell lines, CD45-deficient mice, and CD45-deficient humans initially demonstrated the essential role of CD45 in antigen receptor signal transduction and lymphocyte development. It is now known that CD45 also modulates signals emanating from integrin and cytokine receptors. Recent work has focused on regulation of CD45 expression and alternative splicing, isoform-specific differences in signal transduction, and regulation of phosphatase activity. From these studies, a model is emerging in which CD45 affects cellular responses by controlling the relative threshold of sensitivity to external stimuli. Perturbation of this function may contribute to autoimmunity, immunodeficiency, and malignancy. Moreover, recent advances suggest that modulation of CD45 function can have therapeutic benefit in many disease states.
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van der Wijk T, Blanchetot C, Overvoorde J, den Hertog J. Redox-regulated rotational coupling of receptor protein-tyrosine phosphatase alpha dimers. J Biol Chem 2003; 278:13968-74. [PMID: 12582170 DOI: 10.1074/jbc.m300632200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Receptor protein-tyrosine phosphatase alpha (RPTP alpha) constitutively forms dimers in the membrane, and activity studies with forced dimer mutants of RPTP alpha revealed that rotational coupling of the dimer defines its activity. The hemagglutinin (HA) tag of wild type RPTP alpha and of constitutively dimeric, active RPTP alpha-F135C with a disulfide bond in the extracellular domain was not accessible for antibody, whereas the HA tag of constitutively dimeric, inactive RPTP alpha-P137C was. All three proteins were expressed on the plasma membrane to a similar extent, and the accessibility of their extracellular domains did not differ as determined by biotinylation studies. Dimerization was required for masking the HA tag, and we identified a region in the N terminus of RPTP alpha that was essential for the effect. Oxidative stress has been shown to induce a conformational change of the membrane distal PTP domain (RPTP alpha-D2). Here we report that H(2)O(2) treatment of cells induced a change in rotational coupling in RPTP alpha dimers as detected using accessibility of an HA tag in the extracellular domain as a read-out. The catalytic site Cys(723) in RPTP alpha-D2, which was required for the conformational change of RPTP alpha-D2 upon H(2)O(2) treatment, was essential for the H(2)O(2)-induced increase in accessibility. These results show for the first time that a conformational change in the intracellular domain of RPTP alpha led to a change in conformation of the extracellular domains, indicating that RPTPs have the capacity for inside-out signaling.
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Affiliation(s)
- Thea van der Wijk
- Hubrecht Laboratory, Netherland Institute for Developmental Biology, Uppsalalaan 8, Utrecht, 3584 CT, The Netherlands
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28
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Irles C, Symons A, Michel F, Bakker TR, van der Merwe PA, Acuto O. CD45 ectodomain controls interaction with GEMs and Lck activity for optimal TCR signaling. Nat Immunol 2003; 4:189-97. [PMID: 12496963 DOI: 10.1038/ni877] [Citation(s) in RCA: 137] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2002] [Accepted: 11/22/2002] [Indexed: 12/31/2022]
Abstract
The transmembrane phosphatase CD45 regulates both Lck activity and T cell receptor (TCR) signaling. Here we have tested whether the large ectodomain of CD45 has a role in this regulation. A CD45 chimera containing the large ectodomain of CD43 efficiently rescues TCR signaling in CD45-null T cells, whereas CD45 chimeras containing small ectodomains from other phosphatases do not. Both basal Lck activity in unstimulated cells and the TCR-induced increase in tyrosine phosphorylation of the TCR zeta-chain and in Lck activity depend on the expression of CD45 with a large ectodomain. Unlike CD45 chimeras containing small ectodomains, both the CD45 chimera with a large ectodomain and wild-type CD45 itself are partially localized to glycosphingolipid-enriched membranes (GEMs). Taken together, these data show that the large CD45 ectodomain is required for optimal TCR signaling.
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Affiliation(s)
- Claudine Irles
- Molecular Immunology Unit, Department of Immunology, Institut Pasteur, 25 rue du Dr. Roux, 75724 Paris Cedex 15, France
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29
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Szöllösi J, Alexander DR. The Application of Fluorescence Resonance Energy Transfer to the Investigation of Phosphatases. Methods Enzymol 2003; 366:203-24. [PMID: 14674251 DOI: 10.1016/s0076-6879(03)66017-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- János Szöllösi
- Department of Biophysics and Cell Biology, Faculty of Medicine, Medical and Health Science Center, University of Debrecen, Debrecen H-4012, Hungary
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30
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den Hertog J, van der Wijk T, Tertoolen LG, Blanchetot C. Receptor Protein-Tyrosine Phosphatase Dimerization. Methods Enzymol 2003; 366:224-40. [PMID: 14674252 DOI: 10.1016/s0076-6879(03)66018-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/28/2023]
Affiliation(s)
- Jeroen den Hertog
- Hubrecht Laboratory, Netherlands Institute for Developmental Biology, Uppsalalaan 8, Utrecht, 3584 CT, The Netherlands
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31
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Xu Z, Weiss A. Negative regulation of CD45 by differential homodimerization of the alternatively spliced isoforms. Nat Immunol 2002; 3:764-71. [PMID: 12134145 DOI: 10.1038/ni822] [Citation(s) in RCA: 212] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The regulation of receptor-like protein tyrosine phosphatases (RPTPs) is not well understood. Although CD45 can be negatively regulated by dimerization, how dimerization is modulated is unclear. Here we show that various isoforms of CD45 differentially homodimerize in T cells. The dimerization is modulated by the sialylation and O-glycosylation of alternatively spliced CD45 exons in the extracellular domain. Thus, the smallest isoform, CD45RO--which undergoes the least extracellular sialylation and O-glycosylation--homodimerizes with the highest efficiency, resulting in decreased signaling via the T cell receptor. Because CD45 is required for T cell activation, our findings may reveal a mechanism that contributes to the termination of the primary T cell response. Our results not only demonstrate the biological significance of alternative splicing in the immune system, but also suggest a model for regulating RPTP dimerization and function.
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Affiliation(s)
- Zheng Xu
- Department of Medicine and the Howard Hughes Medical Institute, University of California, San Francisco, CA 94143-0795, USA
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32
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Dornan S, Sebestyen Z, Gamble J, Nagy P, Bodnar A, Alldridge L, Doe S, Holmes N, Goff LK, Beverley P, Szollosi J, Alexander DR. Differential association of CD45 isoforms with CD4 and CD8 regulates the actions of specific pools of p56lck tyrosine kinase in T cell antigen receptor signal transduction. J Biol Chem 2002; 277:1912-8. [PMID: 11694532 DOI: 10.1074/jbc.m108386200] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
An investigation into the role of CD45 isoforms in T cell antigen receptor signal transduction was carried out by transfecting CD45-negative CD4(+)CD8(+) HPB-ALL T cells with the CD45R0, CD45RBC, and CD45RABC isoforms. Fluorescence resonance energy transfer analysis showed that the CD45R0 isoform, but not the CD45RBC or CD45RABC isoforms, was found as homodimers and also preferentially associated with CD4 and CD8 at the cell-surface. A comparison was therefore made of T cell antigen receptor signaling between sub-clones expressing either CD45R0 or CD45RBC. Under basal conditions CD4-associated p56(lck) tyrosine kinase activity and cellular protein tyrosine phosphorylation levels were higher in the CD45R0(+) than in the CD45RBC(+) sub-clones. Upon CD3-CD4 ligation, TCR-zeta phosphorylation, ZAP-70 recruitment to the p21/p23 TCR-zeta phosphoisomers, ZAP-70 phosphorylation, as well as p56(lck), c-Cbl and Slp-76 phosphorylation, were all markedly increased in CD45R0(+) compared with CD45RBC(+) cells. T cell antigen receptor (TCR) stimulation alone also promoted c-Cbl phosphorylation in CD45R0(+) but not in CD45RBC(+) cells. Our results are consistent with a model in which association of CD45R0 with CD4 generates a more active pool of CD4-associated p56(lck) kinase molecules. Upon CD3-CD4 co-ligation, the active p56(lck) increases the intensity of T cell antigen receptor signal transduction coupling by promoting TCR-zeta chain phosphorylation and ZAP-70 recruitment.
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Affiliation(s)
- Saffron Dornan
- Laboratory of Lymphocyte Signalling and Development, Programme of Molecular Immunology, The Babraham Institute, Cambridge, CB2 4AT, United Kingdom
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33
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Hermiston ML, Xu Z, Majeti R, Weiss A. Reciprocal regulation of lymphocyte activation by tyrosine kinases and phosphatases. J Clin Invest 2002. [DOI: 10.1172/jci0214794] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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34
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Affiliation(s)
- R Majeti
- Department of Medicine, and the Howard Hughes Medical Institute, University of California, San Francisco, California 94143, USA
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35
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Jackson MD, Denu JM. Molecular reactions of protein phosphatases--insights from structure and chemistry. Chem Rev 2001; 101:2313-40. [PMID: 11749375 DOI: 10.1021/cr000247e] [Citation(s) in RCA: 168] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- M D Jackson
- Department of Biochemistry and Molecular Biology, Oregon Health Sciences University, 3181 SW Sam Jackson Park Road, Portland, Oregon 97201, USA
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36
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Tertoolen LGJ, Blanchetot C, Jiang G, Overvoorde J, Gadella TWJ, Hunter T, Hertog JD. Dimerization of receptor protein-tyrosine phosphatase alpha in living cells. BMC Cell Biol 2001; 2:8. [PMID: 11401727 PMCID: PMC32300 DOI: 10.1186/1471-2121-2-8] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2001] [Accepted: 06/01/2001] [Indexed: 01/06/2023] Open
Abstract
BACKGROUND Dimerization is an important regulatory mechanism of single membrane-spanning receptors. For instance, activation of receptor protein-tyrosine kinases (RPTKs) involves dimerization. Structural, functional and biochemical studies suggested that the enzymatic counterparts of RPTKs, the receptor protein-tyrosine phosphatases (RPTPs), are inhibited by dimerization, but whether RPTPs actually dimerize in living cells remained to be determined. RESULTS In order to assess RPTP dimerization, we have assayed Fluorescence Resonance Energy Transfer (FRET) between chimeric proteins of cyan- and yellow-emitting derivatives of green fluorescent protein, fused to RPTPalpha, using three different techniques: dual wavelength excitation, spectral imaging and fluorescence lifetime imaging. All three techniques suggested that FRET occurred between RPTPalpha -CFP and -YFP fusion proteins, and thus that RPTPalpha dimerized in living cells. RPTPalpha dimerization was constitutive, extensive and specific. RPTPalpha dimerization was consistent with cross-linking experiments, using a non-cell-permeable chemical cross-linker. Using a panel of deletion mutants, we found that the transmembrane domain was required and sufficient for dimerization. CONCLUSIONS We demonstrate here that RPTPalpha dimerized constitutively in living cells, which may be mediated by the transmembrane domain, providing strong support for the model that dimerization is involved in regulation of RPTPs.
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Affiliation(s)
- Leon GJ Tertoolen
- Hubrecht Laboratory, Netherlands Institute for Developmental Biology, Utrecht, The Netherlands
| | - Christophe Blanchetot
- Hubrecht Laboratory, Netherlands Institute for Developmental Biology, Utrecht, The Netherlands
| | - Guoqiang Jiang
- Molecular Biology and Virology Laboratory, The Salk Institute for Biological Studies, La Jolla, USA
- present address: Merck Research Laboratory, Rahway, USA
| | - John Overvoorde
- Hubrecht Laboratory, Netherlands Institute for Developmental Biology, Utrecht, The Netherlands
| | - Theodorus WJ Gadella
- Laboratory for Molecular Biology, Wageningen University, Wageningen, The Netherlands
| | - Tony Hunter
- Molecular Biology and Virology Laboratory, The Salk Institute for Biological Studies, La Jolla, USA
| | - Jeroen den Hertog
- Hubrecht Laboratory, Netherlands Institute for Developmental Biology, Utrecht, The Netherlands
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37
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Majeti R, Xu Z, Parslow TG, Olson JL, Daikh DI, Killeen N, Weiss A. An inactivating point mutation in the inhibitory wedge of CD45 causes lymphoproliferation and autoimmunity. Cell 2000; 103:1059-70. [PMID: 11163182 DOI: 10.1016/s0092-8674(00)00209-9] [Citation(s) in RCA: 201] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A model has been proposed for the regulation of CD45, and by homology other RPTPs, in which dimerization inhibits phosphatase activity through symmetrical interactions between an inhibitory structural wedge and the catalytic site. Here, we report the phenotype of mice with a single point mutation, glutamate 613 to arginine, that inactivates the inhibitory wedge of CD45. The CD45 E613R mutation causes polyclonal lymphocyte activation leading to lymphoproliferation and severe autoimmune nephritis with autoantibody production, resulting in death. Both homozygotes and heterozygotes develop pathology, indicating genetic dominance of CD45 E613R. The dramatic phenotype of CD45 E613R mice demonstrates the in vivo importance of negative regulation of CD45 by dimerization, supporting the model for regulation of CD45, and RPTPs in general.
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Affiliation(s)
- R Majeti
- Department of Medicine, University of California-San Francisco, San Francisco, CA 94143, USA
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Jiang G, den Hertog J, Hunter T. Receptor-like protein tyrosine phosphatase alpha homodimerizes on the cell surface. Mol Cell Biol 2000; 20:5917-29. [PMID: 10913175 PMCID: PMC86069 DOI: 10.1128/mcb.20.16.5917-5929.2000] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
We reported previously that the N-terminal D1 catalytic domain of receptor protein-tyrosine phosphatase alpha (RPTPalpha) forms a symmetrical, inhibited dimer in a crystal structure, in which a helix-turn-helix wedge element from one monomer is inserted into the catalytic cleft of the other monomer. Previous functional studies also suggested that dimerization inhibits the biological activity of a CD45 chimeric RPTP and the catalytic activity of an isolated RPTPsigma D1 catalytic domain. Most recently, we have also shown that enforced dimerization inhibits the biological activity of full-length RPTPalpha in a wedge-dependent manner. The physiological significance of such inhibition is unknown, due to a lack of understanding of how RPTPalpha dimerization is regulated in vivo. In this study, we show that transiently expressed cell surface RPTPalpha exists predominantly as homodimers, suggesting that dimerization-mediated inhibition of RPTPalpha biological activity is likely to be physiologically relevant. Consistent with our published and unpublished crystallographic data, we show that mutations in the wedge region of D1 catalytic domain and deletion of the entire D2 catalytic domain independently reduced but did not abolish RPTPalpha homodimerization, suggesting that both domains are critically involved but that neither is essential for homodimerization. Finally, we also provide evidence that both the RPTPalpha extracellular domain and the transmembrane domain were independently able to homodimerize. These results lead us to propose a zipper model in which inactive RPTPalpha dimers are stabilized by multiple, relatively weak dimerization interfaces. Dimerization in this manner would provide a potential mechanism for negative regulation of RPTPalpha. Such RPTPalpha dimers could be activated by extracellular ligands or intracellular binding proteins that induce monomerization or by intracellular signaling events that induce an open conformation of the dimer.
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Affiliation(s)
- G Jiang
- Molecular Biology and Virology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA
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39
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Feiken E, van Etten I, Gebbink MF, Moolenaar WH, Zondag GC. Intramolecular interactions between the juxtamembrane domain and phosphatase domains of receptor protein-tyrosine phosphatase RPTPmu. Regulation of catalytic activity. J Biol Chem 2000; 275:15350-6. [PMID: 10809770 DOI: 10.1074/jbc.275.20.15350] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
RPTPmu is a receptor-like protein-tyrosine phosphatase (RPTP) whose ectodomain mediates homotypic cell-cell interactions. The intracellular part of RPTPmu contains a relatively long juxtamembrane domain (158 amino acids; aa) and two conserved phosphatase domains (C1 and C2). The membrane-proximal C1 domain is responsible for the catalytic activity of RPTPmu, whereas the membrane-distal C2 domain serves an unknown function. The regulation of RPTP activity remains poorly understood, although dimerization has been proposed as a general mechanism of inactivation. Using the yeast two-hybrid system, we find that the C1 domain binds to an N-terminal noncatalytic region in RPTPmu, termed JM (aa 803-955), consisting of a large part of the juxtamembrane domain (120 aa) and a small part of the C1 domain (33 aa). When co-expressed in COS cells, the JM polypeptide binds to both the C1 and the C2 domain. Strikingly, the isolated JM polypeptide fails to interact with either full-length RPTPmu or with truncated versions of RPTPmu that contain the JM region, consistent with the JM-C1 and JM-C2 interactions being intramolecular rather than intermolecular. Furthermore, we find that large part of the juxtamembrane domain (aa 814-922) is essential for C1 to be catalytically active. Our findings suggest a model in which RPTPmu activity is regulated by the juxtamembrane domain undergoing intramolecular interactions with both the C1 and C2 domain.
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Affiliation(s)
- E Feiken
- Division of Cellular Biochemistry, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
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Jiang G, den Hertog J, Su J, Noel J, Sap J, Hunter T. Dimerization inhibits the activity of receptor-like protein-tyrosine phosphatase-alpha. Nature 1999; 401:606-10. [PMID: 10524630 DOI: 10.1038/44170] [Citation(s) in RCA: 153] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Protein-tyrosine phosphatases (PTPs) are vital for regulating tryosine phosphorylation in many processes, including growth and differentiation. The regulation of receptor-like PTP (RPTP) activity remains poorly understood, but based on the crystal structure of RPTPalpha domain 1 we have proposed that dimerization can negatively regulate activity, through the interaction of an inhibitory 'wedge' on one monomer with the catalytic cleft of domain 1 in the other monomer. Here we show that dimerization inhibits the activity of a full-length RPTP in vivo. We generated stable disulphide-bonded full-length RPTPalpha homodimers by expressing mutants with single cysteines at different positions in the ectodomain juxtamembrane region. Expression of wild-type RPTPalpha and Phe135Cys and Thr141Cys mutants in RPTPalpha-null mouse embryo cells increased dephosphorylation and activity of Tyr 529 in the protein tyrosine kinase c-Src; in contrast, expression of a Pro137Cys mutant did not. Mutation of Pro 210/211 to leucine in the inhibitory wedge of the Pro137Cys mutant restored its ability to activate c-Src, indicating that dimerization may inhibit full-length RPTPalpha activity in a manner stereochemically consistent with RPTPalpha crystal structures. Our results suggest that RPTPalpha activity can in principle be negatively regulated by dimerization in vivo.
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Affiliation(s)
- G Jiang
- Molecular Biology and Virology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA.
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Motoya S, Kitamura K, Matsuda A, Maizel AL, Yamamoto H, Takeda A. Interaction between CD45-AP and protein-tyrosine kinases involved in T cell receptor signaling. J Biol Chem 1999; 274:1407-14. [PMID: 9880514 DOI: 10.1074/jbc.274.3.1407] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
CD45-AP associates specifically with CD45, a protein-tyrosine phosphatase essential for antigen receptor-mediated signal transduction. CD45 modulates the activity of Src family protein-tyrosine kinases involved at the onset of antigen receptor-mediated signaling by dephosphorylating their regulatory tyrosyl residues. We have shown that lymphocyte responses to antigen receptor stimulation are impaired in CD45-AP-null mice. To examine the possibility that CD45-AP coordinates the interaction between CD45 and its substrates, we investigated the associations of CD45-AP with several protein-tyrosine kinases. Endogenous CD45-AP coimmunoprecipitated with Lck and ZAP-70 in both CD45-positive T cells and their CD45-negative variants after stimulation by antigen receptor ligation. Concomitantly, CD45 coimmunoprecipitated with Lck and ZAP-70 after T cell receptor-mediated stimulation of CD45-positive cells. Recombinant CD45-AP exhibited specific binding to Lck and ZAP-70 protein-tyrosine kinases, but not to Fyn or Csk, in lysates of both CD45-positive and -negative T cells. Specific interactions were demonstrated between the respective recombinant proteins as well. These results demonstrate that CD45-AP associates directly and selectively with Lck and ZAP-70 in response to T cell receptor-mediated stimulation. The associations of CD45-AP with Lck and ZAP-70 may mediate the functional interactions of these kinases with CD45 during antigen receptor stimulation.
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Affiliation(s)
- S Motoya
- Department of Pathology, Roger Williams Medical Center-Boston University, Providence, Rhode Island 02908, USA
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42
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Felberg J, Johnson P. Characterization of recombinant CD45 cytoplasmic domain proteins. Evidence for intramolecular and intermolecular interactions. J Biol Chem 1998; 273:17839-45. [PMID: 9651387 DOI: 10.1074/jbc.273.28.17839] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
CD45 is a transmembrane two-domain tyrosine phosphatase required for efficient signal transduction initiated by lymphocyte antigen receptors. As with most transmembrane two-domain phosphatases, the role of the second phosphatase domain is unclear. In this study, recombinant CD45 cytoplasmic domain proteins purified from bacteria were used to evaluate the function of the individual phosphatase domains. A recombinant protein expressing the membrane-proximal region, first phosphatase domain, and spacer region of CD45 (rD1) was catalytically active and found to exist primarily as a dimer. In contrast to this, a recombinant protein expressing the spacer region, the second phosphatase domain and the carboxy tail of CD45 (rD2) existed as a monomer and had no catalytic activity against any of the substrates tested. Comparison of rD1 with the recombinant protein expressing the entire cytoplasmic domain of CD45 (rD1/D2) indicated that rD1/D2 was 2-3-fold more catalytically active, was more thermostable, and existed primarily as a monomer. Limited trypsin digestion of rD1/D2 provided evidence for a noncovalent association between an N-terminal 27-kDa fragment and a C-terminal 53-kDa fragment, suggesting an intramolecular interaction. Furthermore, rD1 was found to specifically associate with rD2 in an in vitro binding assay. Taken together, these data provide evidence for an intramolecular interaction occurring in the cytoplasmic domain of CD45. In the absence of the C-terminal region containing the second phosphatase domain, intermolecular interactions occur, resulting in dimer formation.
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Affiliation(s)
- J Felberg
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada
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Matsuda A, Motoya S, Kimura S, McInnis R, Maizel AL, Takeda A. Disruption of lymphocyte function and signaling in CD45-associated protein-null mice. J Exp Med 1998; 187:1863-70. [PMID: 9607926 PMCID: PMC2212302 DOI: 10.1084/jem.187.11.1863] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/1997] [Revised: 03/04/1998] [Indexed: 11/04/2022] Open
Abstract
CD45-AP specifically associates with CD45, a protein tyrosine phosphatase essential for lymphocyte differentiation and antigen receptor-mediated signal transduction. CD45 is thought to mediate antigen receptor signaling by dephosphorylating regulatory tyrosine residues on Src family protein tyrosine kinases such as Lck. However, the mechanism for regulating CD45 protein tyrosine phosphatase activity remains unclear. CD45-AP-null mice were created to examine the role of CD45-AP in CD45-mediated signal transduction. T and B lymphocytes showed reduced proliferation in response to antigen receptor stimulation. Both mixed leukocyte reaction and cytotoxic T lymphocyte functions of T cells were also markedly decreased in CD45-AP-null mice. Interestingly, the interaction between CD45 and Lck was significantly reduced in CD45-AP-null T cells, indicating that CD45-AP directly or indirectly mediates the interaction of CD45 with Lck. Our data indicate that CD45-AP is required for normal antigen receptor signaling and function in lymphocytes.
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Affiliation(s)
- A Matsuda
- Department of Pathology, Roger Williams Hospital-Brown University, Providence, Rhode Island 02908, USA
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44
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Walsh FS, Doherty P. Neural cell adhesion molecules of the immunoglobulin superfamily: role in axon growth and guidance. Annu Rev Cell Dev Biol 1998; 13:425-56. [PMID: 9442880 DOI: 10.1146/annurev.cellbio.13.1.425] [Citation(s) in RCA: 387] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
NCAM, L1, and DCC--immunoglobulin cell adhesion molecules (Ig CAMs)--are widely expressed during development. Many workers have dismissed a role for such molecules in the control of axonal growth and guidance because they do not show highly restricted expression patterns. Yet evidence from a number of model systems suggests all three CAMs play a role in the development of specific projections in the nervous system. For example, there is a reduction in mossy fiber tracts in the hippocampus of mice that lack NCAM, a requirement for DCC in the response of commissural neurons to a floor plate-derived chemoattractant, and a loss of corticospinal tracts in humans who carry mutations in the L1 gene. The above paradox might be explained by the observation that differential post-translational processing can modulate CAMs function and that alternative splicing can generate functionally distinct isoforms of a CAM. Activation of the FGF tyrosine kinase receptor is required for the responses stimulated by NCAM and L1, and the importance of regulated tyrosine phosphorylation for growth and guidance is underscored by the involvement of receptor tyrosine phosphatases in this process.
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Affiliation(s)
- F S Walsh
- Department of Neuroscience, Smith Kline Beecham Pharmaceuticals, New Frontiers Science Park, Harlow, Essex, United Kingdom.
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45
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Majeti R, Bilwes AM, Noel JP, Hunter T, Weiss A. Dimerization-induced inhibition of receptor protein tyrosine phosphatase function through an inhibitory wedge. Science 1998; 279:88-91. [PMID: 9417031 DOI: 10.1126/science.279.5347.88] [Citation(s) in RCA: 206] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The function and regulation of the receptorlike transmembrane protein tyrosine phosphatases (RPTPs) are not well understood. Ligand-induced dimerization inhibited the function of the epidermal growth factor receptor (EGFR)-RPTP CD45 chimera (EGFR-CD45) in T cell signal transduction. Properties of mutated EGFR-CD45 chimeras supported a general model for the regulation of RPTPs, derived from the crystal structure of the RPTPalpha membrane-proximal phosphatase domain. The phosphatase domain apparently forms a symmetrical dimer in which the catalytic site of one molecule is blocked by specific contacts with a wedge from the other.
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Affiliation(s)
- R Majeti
- Department of Microbiology, University of California, San Francisco, CA 94143, USA
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46
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Affiliation(s)
- L B Justement
- Department of Microbiology, University of Alabama at Birmingham 35294, USA
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47
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Altin JG, Sloan EK. The role of CD45 and CD45-associated molecules in T cell activation. Immunol Cell Biol 1997; 75:430-45. [PMID: 9429890 DOI: 10.1038/icb.1997.68] [Citation(s) in RCA: 135] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
CD45 (lymphocyte common antigen) is a receptor-linked protein tyrosine phosphatase that is expressed on all leucocytes, and which plays a crucial role in the function of these cells. On T cells the extracellular domain of CD45 is expressed in several different isoforms, and the particular isoform(s) expressed depends on the particular subpopulation of cell, their state of maturation, and whether or not they have previously been exposed to antigen. It has been established that the expression of CD45 is essential for the activation of T cells via the TCR, and that different CD45 isoforms display a different ability to support T cell activation. Although the tyrosine phosphatase activity of the intracellular region of CD45 has been shown to be crucial for supporting signal transduction from the TCR, the nature of the ligands for the different isoforms of CD45 have been elusive. Moreover, the precise mechanism by which potential ligands may regulate CD45 function is unclear. Interestingly, in T cells CD45 has been shown to associate with numerous molecules, both membrane associated and intracellular; these include components of the TCR-CD3 complex and CD4/CD8. In addition, CD45 is reported to associate with several intracellular protein tyrosine kinases including p56lck and p59fyn of the src family, and ZAP-70 of the Syk family, and with numerous proteins of 29-34 kDa. These CD45-associated molecules may play an important role in regulating CD45 tyrosine phosphatase activity and function. However, although the role of some of the CD45-associated molecules (e.g. CD45-AP and LPAP) has become better understood in recent years, the role of others still remains obscure. This review aims to summarize recent findings on the role of CD45 and CD45-associated molecules in T cell activation, and to highlight issues that seem relevant to ongoing research in this area.
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Affiliation(s)
- J G Altin
- Division of Biochemistry and Molecular Biology, School of Life Sciences, Faculty of Science, Australian National University, Canberra, Australia.
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48
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Lorenzo HK, Farber D, Germain V, Acuto O, Alzari PM. The MBP fusion protein restores the activity of the first phosphatase domain of CD45. FEBS Lett 1997; 411:231-5. [PMID: 9271211 DOI: 10.1016/s0014-5793(97)00703-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
CD45 is a receptor-like protein tyrosine phosphatase critically involved in the regulation of initial effector functions in B- and T-cells. The protein comprises two phosphatase (PTP) domains in its cytoplasmic region. However, whether each PTP domain has enzyme activity by itself or whether both domains are required to build up a functional enzyme is unclear. We have studied different constructions of human CD45 comprising the two PTP domains, both separately and as a single protein, fused to maltose-binding protein (MBP). In apparent contrast with previous studies, we show that the first PTP domain of CD45 (when fused to MBP) may be a viable phosphatase in the absence of the second domain. Phosphatase activity resides in the monomeric form of the protein and is lost after proteolytic cleavage of the fusion partner, indicating that MBP specifically activates the first PTP domain. Furthermore, changes in the optimal pH for activity with respect to wild-type CD45 suggest that protein-protein interactions involving residues in the neighbourhood of the catalytic site mediate enzyme activation.
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Affiliation(s)
- H K Lorenzo
- Unité d'Immunologie Structurale, Institut Pasteur, Paris, France
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49
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Bilwes AM, den Hertog J, Hunter T, Noel JP. Structural basis for inhibition of receptor protein-tyrosine phosphatase-alpha by dimerization. Nature 1996; 382:555-9. [PMID: 8700232 DOI: 10.1038/382555a0] [Citation(s) in RCA: 261] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Receptor-like protein-tyrosine phosphatases (RPTPs), like their non-receptor counterparts, regulate the level of phosphotyrosine-containing proteins derived from the action of protein-tyrosine kinases. RPTPs are type-I integral membrane proteins which contain one or two catalytic domains in their cytoplasmic region. It is not known whether extracellular ligands regulate the activity of RPTPs. Here we describe the crystal structure of the membrane-proximal catalytic domain (D1) of a typical RPTP, murine RPTP alpha. Significant structural deviations from the PTP1B fold reside within the amino-terminal helix-turn-helix segment of RPTPalphaD1 (residues 214 to 242) and a distinctive two-stranded beta-sheet formed between residues 211-213 and 458-461. The turn of the N-terminal segment inserts into the active site of a dyad-related D1 monomer. On the basis of two independent crystal structures, sequence alignments, and the reported biological activity of EGF receptor/CD45 chimaeras, we propose that dimerization and active-site blockage is a physiologically important mechanism for downregulating the catalytic activity of RPTPalpha and other RPTPs.
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Affiliation(s)
- A M Bilwes
- Structural Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA
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50
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Cahir McFarland ED, Thomas ML. CD45 protein-tyrosine phosphatase associates with the WW domain-containing protein, CD45AP, through the transmembrane region. J Biol Chem 1995; 270:28103-7. [PMID: 7499298 DOI: 10.1074/jbc.270.47.28103] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
CD45 is a transmembrane protein-tyrosine phosphatase required for antigen receptor signaling in lymphocytes. CD45 activates the Src family protein-tyrosine kinases, p56lck and p59fyn, by dephosphorylating a negative regulatory tyrosine in the carboxyl terminus. Immunoprecipitation of CD45 precipitates p56lck and CD45AP. Although the function of CD45AP is unknown, it has been proposed to be an adapter between p56lck and CD45. To assess the ability of CD45AP to function as an adapter, we determined the regions required for the interaction with CD45 by expressing chimeric proteins in HeLa cells. CD45AP has a region similar to a potential protein-protein interaction domain, the WW domain. Surprisingly, this domain was not necessary for the association with CD45. Rather, a 40-amino acid sequence encompassing the putative transmembrane domain of CD45AP was sufficient to mediate binding to CD45. Similarly, a 39-amino acid sequence encompassing the CD45 transmembrane region was sufficient to direct the interaction with CD45AP. Expression of p56lck with CD45AP resulted in an interaction that could only be detected by in vitro kinase reaction, suggesting that the association of p56lck and CD45AP is weak. These data support a model in which CD45AP links CD45 with other proteins but not necessarily p56lck.
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Affiliation(s)
- E D Cahir McFarland
- Howard Hughes Medical Institute, Department of Pathology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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