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Kruglova NA, Mazurov DV, Filatov AV. Lymphocyte Phosphatase-Associated Phosphoprotein (LPAP) as a CD45 Protein Stability Regulator. BIOCHEMISTRY. BIOKHIMIIA 2024; 89:912-922. [PMID: 38880651 DOI: 10.1134/s0006297924050110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2023] [Revised: 01/14/2024] [Accepted: 01/16/2024] [Indexed: 06/18/2024]
Abstract
Lymphocyte phosphatase-associated phosphoprotein (LPAP) is a binding partner of the phosphatase CD45, but its function remains poorly understood. Its close interaction with CD45 suggests that LPAP may potentially regulate CD45, but direct biochemical evidence for this has not yet been obtained. We found that in the Jurkat lymphoid cells the levels of LPAP and CD45 proteins are interrelated and well correlated with each other. Knockout of LPAP leads to the decrease in the surface expression of CD45, while its overexpression, on the contrary, caused its increase. No such correlation was found in the non-lymphoid K562 cells. We hypothesize that LPAP regulates expression level of CD45 and thus can affect lymphocyte activation.
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Affiliation(s)
- Natalia A Kruglova
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Institute of Gene Biology, Russian Academy of Sciences, Moscow, 119334, Russia
| | - Dmitriy V Mazurov
- National Research Center Institute of Immunology, Federal Medical Biological Agency of Russia, Moscow, 115522, Russia
| | - Alexander V Filatov
- National Research Center Institute of Immunology, Federal Medical Biological Agency of Russia, Moscow, 115522, Russia.
- Department of Immunology, Faculty of Biology, Lomonosov Moscow State University, Moscow, 119234, Russia
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2
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Yang C, Wang X, To KKW, Cui C, Luo M, Wu S, Huang L, Fu K, Pan C, Liu Z, Fan T, Yang C, Wang F, Fu L. Circulating tumor cells shielded with extracellular vesicle-derived CD45 evade T cell attack to enable metastasis. Signal Transduct Target Ther 2024; 9:84. [PMID: 38575583 PMCID: PMC10995208 DOI: 10.1038/s41392-024-01789-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 01/09/2024] [Accepted: 03/05/2024] [Indexed: 04/06/2024] Open
Abstract
Circulating tumor cells (CTCs) are precursors of distant metastasis in a subset of cancer patients. A better understanding of CTCs heterogeneity and how these CTCs survive during hematogenous dissemination could lay the foundation for therapeutic prevention of cancer metastasis. It remains elusive how CTCs evade immune surveillance and elimination by immune cells. In this study, we unequivocally identified a subpopulation of CTCs shielded with extracellular vesicle (EVs)-derived CD45 (termed as CD45+ CTCs) that resisted T cell attack. A higher percentage of CD45+ CTCs was found to be closely correlated with higher incidence of metastasis and worse prognosis in cancer patients. Moreover, CD45+ tumor cells orchestrated an immunosuppressive milieu and CD45+ CTCs exhibited remarkably stronger metastatic potential than CD45- CTCs in vivo. Mechanistically, CD45 expressing on tumor surfaces was shown to form intercellular CD45-CD45 homophilic interactions with CD45 on T cells, thereby preventing CD45 exclusion from TCR-pMHC synapse and leading to diminished TCR signaling transduction and suppressed immune response. Together, these results pointed to an underappreciated capability of EVs-derived CD45-dressed CTCs in immune evasion and metastasis, providing a rationale for targeting EVs-derived CD45 internalization by CTCs to prevent cancer metastasis.
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Affiliation(s)
- Chuan Yang
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, 510060, P.R. China
| | - Xueping Wang
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, 510060, P.R. China
| | - Kenneth K W To
- School of Pharmacy, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
| | - Caimei Cui
- LABVIV Technology (Shenzhen) Co., Ltd, Shenzhen, 518057, China
| | - Min Luo
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, 510060, P.R. China
| | - Shaocong Wu
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, 510060, P.R. China
| | - Lamei Huang
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, 510060, P.R. China
| | - Kai Fu
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, 510060, P.R. China
| | - Can Pan
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, 510060, P.R. China
| | - Zeyu Liu
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, 510060, P.R. China
| | - Teng Fan
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, 510060, P.R. China
| | - Caibo Yang
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, 510060, P.R. China
| | - Fang Wang
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, 510060, P.R. China.
| | - Liwu Fu
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, 510060, P.R. China.
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Rizzo S, Thévenin D. Identifying Transmembrane Interactions in Receptor Protein Tyrosine Phosphatase Homodimerization and Heterodimerization. Methods Mol Biol 2024; 2743:195-209. [PMID: 38147217 PMCID: PMC10785008 DOI: 10.1007/978-1-0716-3569-8_13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2023]
Abstract
Receptor protein tyrosine phosphatases (RPTPs) are one of the key regulators of receptor tyrosine kinases (RTKs) and therefore play a critical role in modulating signal transduction. While the structure-function relationship of RTKs has been widely studied, the mechanisms modulating the activity of RPTPs still need to be fully understood. On the other hand, homodimerization has been shown to antagonize RPTP catalytic activity and appears to be a general feature of the entire family. Conversely, their documented ability to physically interact with RTKs is integral to their negative regulation of RTKs, but there is a yet-to-be proposed common model. However, specific transmembrane (TM) domain interactions and residues have been shown to be essential in regulating RPTP homodimerization, interactions with RTK substrates, and activity. Therefore, elucidating the contribution of the TM domains in RPTP regulation can provide significant insights into how these receptors function, interact, and eventually be modulated. This chapter describes the dominant-negative AraC-based transcriptional reporter (DN-AraTM) assay to identify specific TM interactions essential to homodimerization and heteroassociation with other membrane receptors, such as RTKs.
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Affiliation(s)
- Sophie Rizzo
- Department of Chemistry, Lehigh University, Bethlehem, PA, USA
| | - Damien Thévenin
- Department of Chemistry, Lehigh University, Bethlehem, PA, USA.
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4
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Reth M. Discovering immunoreceptor coupling and organization motifs. Front Immunol 2023; 14:1253412. [PMID: 37731510 PMCID: PMC10507400 DOI: 10.3389/fimmu.2023.1253412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Accepted: 08/11/2023] [Indexed: 09/22/2023] Open
Abstract
The recently determined cryo-EM structures of the T cell antigen receptor (TCR) and B cell antigen receptor (BCR) show in molecular details the interactions of the ligand-binding part with the signaling subunits but they do not reveal the signaling mechanism of these antigen receptors. Without knowing the molecular basis of antigen sensing by these receptors, a rational design of optimal vaccines is not possible. The existence of conserved amino acids (AAs) that are not involved in the subunit interaction suggests that antigen receptors form higher complexes and/or have lateral interactors that control their activity. Here, I describe evolutionary conserved leucine zipper (LZ) motifs within the transmembrane domains (TMD) of antigen and coreceptor components that are likely to be involved in the oligomerization and lateral interaction of antigen receptor complexes on T and B cells. These immunoreceptor coupling and organization motifs (ICOMs) are also found within the TMDs of other important receptor types and viral envelope proteins. This discovery suggests that antigen receptors do not function as isolated entities but rather as part of an ICOM-based interactome that controls their nanoscale organization on resting cells and their dynamic remodeling on activated lymphocytes.
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Affiliation(s)
- Michael Reth
- Department of Molecular Immunology, Biology III, Faculty of Biology, University of Freiburg, Freiburg, Germany
- Signaling Research Centers CIBSS and BIOSS, University of Freiburg, Freiburg, Germany
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5
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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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6
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Simulation of receptor triggering by kinetic segregation shows role of oligomers and close-contacts. Biophys J 2022; 121:1660-1674. [PMID: 35367423 PMCID: PMC9117938 DOI: 10.1016/j.bpj.2022.03.033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 01/07/2022] [Accepted: 03/28/2022] [Indexed: 11/23/2022] Open
Abstract
The activation of T cells, key players of the immune system, involves local evacuation of phosphatase CD45 from a region of the T cell's surface, segregating it from the T cell receptor. What drives this evacuation? In the presence of antigen, what ensures evacuation happens in the subsecond timescales necessary to initiate signaling? In the absence of antigen, what mechanisms ensure that evacuation does not happen spontaneously, which could cause signaling errors? Phenomena known to influence spatial organization of CD45 or similar surface molecules include diffusive motion in the lipid bilayer, oligomerization reactions, and mechanical compression against a nearby surface, such as that of the cell presenting the antigen. Computer simulations can investigate hypothesized spatiotemporal mechanisms of T cell signaling. The challenge to computational studies of evacuation is that the base process, spontaneous evacuation by simple diffusion, is in the extreme rare event limit, meaning direct stochastic simulation is unfeasible. Here, we combine particle-based spatial stochastic simulation with the weighted ensemble method for rare events to compute the mean first passage time for cell surface availability by surface reorganization of CD45. We confirm mathematical estimates that, at physiological concentrations, spontaneous evacuation is extremely rare, roughly 300 years. We find that dimerization decreases the time required for evacuation. A weak bimolecular interaction (dissociation constant estimate 460 μM) is sufficient for an order of magnitude reduction of spontaneous evacuation times, and oligomerization to hexamers reduces times to below 1 s. This introduces a mechanism whereby externally induced CD45 oligomerization could significantly modify T cell function. For large regions of close contact, such as those induced by large microvilli, molecular size and compressibility imply a nonzero reentry probability of 60%, decreasing evacuation times. Simulations show that these reduced evacuation times are still unrealistically long (even with a fourfold variation centered around previous estimates of parameters), suggesting that a yet-to-be-described mechanism, besides compressional exclusion at a close contact, drives evacuation.
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7
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O'Connell P, Blake MK, Godbehere S, Aldhamen YA, Amalfitano A. Absence of ERAP1 in B Cells Increases Susceptibility to Central Nervous System Autoimmunity, Alters B Cell Biology, and Mechanistically Explains Genetic Associations between ERAP1 and Multiple Sclerosis. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2021; 207:2952-2965. [PMID: 34810226 DOI: 10.4049/jimmunol.2100813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Accepted: 10/18/2021] [Indexed: 11/19/2022]
Abstract
Hundreds of genes have been linked to multiple sclerosis (MS); yet, the underlying mechanisms behind these associations have only been investigated in a fraction of cases. Endoplasmic reticulum aminopeptidase 1 (ERAP1) is an endoplasmic reticulum-localized aminopeptidase with important roles in trimming peptides destined for MHC class I and regulation of innate immune responses. As such, genetic polymorphisms in ERAP1 have been linked to multiple autoimmune diseases. In this study, we present, to our knowledge, the first mechanistic studies performed to uncover why polymorphisms in ERAP1 are associated with increased susceptibility to MS. Combining multiple mouse models of CNS autoimmunity with high-dimensional single-cell spectral cytometry, adoptive transfer studies, and integrative analysis of human single-cell RNA-sequencing datasets, we identify an intrinsic defect in B cells as being primarily responsible. Not only are mice lacking ERAP1 more susceptible to CNS autoimmunity, but adoptive transfer of B cells lacking ERAP1 into B cell-deficient mice recapitulates this susceptibility. We found B cells lacking ERAP1 display decreased proliferation in vivo and express higher levels of activation/costimulatory markers. Integrative analysis of single-cell RNA sequencing of B cells from 36 individuals revealed subset-conserved differences in gene expression and pathway activation in individuals harboring the MS-linked K528R ERAP1 single-nucleotide polymorphism. Finally, our studies also led us to create, to our knowledge, the first murine protein-level map of the CNS IL-10+ immune compartment at steady state and during neuroinflammation. These studies identify a role for ERAP1 in the modulation of B cells and highlight this as one reason why polymorphisms in this gene are linked to MS.
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Affiliation(s)
- Patrick O'Connell
- Department of Microbiology and Molecular Genetics, College of Osteopathic Medicine, Michigan State University, East Lansing, MI; and
| | - Maja K Blake
- Department of Microbiology and Molecular Genetics, College of Osteopathic Medicine, Michigan State University, East Lansing, MI; and
| | - Sarah Godbehere
- Department of Microbiology and Molecular Genetics, College of Osteopathic Medicine, Michigan State University, East Lansing, MI; and
| | - Yasser A Aldhamen
- Department of Microbiology and Molecular Genetics, College of Osteopathic Medicine, Michigan State University, East Lansing, MI; and
| | - Andrea Amalfitano
- Department of Microbiology and Molecular Genetics, College of Osteopathic Medicine, Michigan State University, East Lansing, MI; and .,Department of Pediatrics, College of Osteopathic Medicine, Michigan State University, East Lansing, MI
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8
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T cell receptor signaling results in ERK-dependent Ser163 phosphorylation of lymphocyte phosphatase-associated phosphoprotein. Biochem Biophys Res Commun 2019; 519:559-565. [PMID: 31537385 DOI: 10.1016/j.bbrc.2019.09.041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Accepted: 09/11/2019] [Indexed: 11/22/2022]
Abstract
Lymphocyte phosphatase-associated phosphoprotein (LPAP) is a transmembrane protein tightly associated with the phosphatase CD45, which regulates antigen specific lymphocyte activation. Although LPAP is positioned in close proximity to key signaling molecules, its function remains unknown. In this study, we investigated signaling pathways involved in LPAP phosphorylation. Using phosphospecific antibodies generated in our laboratory, we analyzed changes in LPAP phosphorylation in response to various stimuli. Cross-linking with antibodies against TCR or BCR, as well as ionophores and Thapsigargin, resulted in rapid dephosphorylation at Ser172 and Ser99 followed by phosphorylation at Ser163. A panel of inhibitors allowed us to show that PMA and TCR cross-linkage engages the MEK-ERK pathway to drive phosphorylation of LPAP at Ser163. The ERK1/2 kinase was the most distal element in the cascade, which when inhibited prevented changes in LPAP phosphorylation. Supporting this, we found that ERK1 is capable of phosphorylating LPAP at Ser163 in vitro. Although the functional role of this event is yet to be revealed, we provide evidence for a new ERK1/2 target in lymphocytes, namely LPAP, representing a potential regulatory mechanism in the signaling cascade.
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9
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Bloch E, Sikorski EL, Pontoriero D, Day EK, Berger BW, Lazzara MJ, Thévenin D. Disrupting the transmembrane domain-mediated oligomerization of protein tyrosine phosphatase receptor J inhibits EGFR-driven cancer cell phenotypes. J Biol Chem 2019; 294:18796-18806. [PMID: 31676686 DOI: 10.1074/jbc.ra119.010229] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 10/21/2019] [Indexed: 12/19/2022] Open
Abstract
Receptor protein tyrosine phosphatases (RPTPs) play critical regulatory roles in mammalian signal transduction. However, the structural basis for the regulation of their catalytic activity is not fully understood, and RPTPs are generally not therapeutically targetable. This knowledge gap is partially due to the lack of known natural ligands or selective agonists of RPTPs. Contrary to what is known from structure-function studies of receptor tyrosine kinases (RTKs), RPTP activities have been reported to be suppressed by dimerization, which may prevent RPTPs from accessing their RTK substrates. We report here that homodimerization of protein tyrosine phosphatase receptor J (PTPRJ, also known as DEP-1) is regulated by specific transmembrane (TM) residues. We found that disrupting these interactions destabilizes homodimerization of full-length PTPRJ in cells, reduces the phosphorylation of the known PTPRJ substrate epidermal growth factor receptor (EGFR) and of other downstream signaling effectors, antagonizes EGFR-driven cell phenotypes, and promotes substrate access. We demonstrate these observations in human cancer cells using mutational studies and identified a peptide that binds to the PTPRJ TM domain and represents the first example of an allosteric agonist of RPTPs. The results of our study provide fundamental structural and functional insights into how PTPRJ activity is tuned by TM interactions in cells. Our findings also open up opportunities for developing peptide-based agents that could be used as tools to probe RPTPs' signaling mechanisms or to manage cancers driven by RTK signaling.
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Affiliation(s)
- Elizabeth Bloch
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015
| | - Eden L Sikorski
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015
| | - David Pontoriero
- Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia 22903
| | - Evan K Day
- Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia 22903
| | - Bryan W Berger
- Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia 22903
| | - Matthew J Lazzara
- Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia 22903
| | - Damien Thévenin
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015.
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10
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Kruglova NA, Kopylov AT, Filatov AV. Identification of the Molecular Partners of Lymphocyte Phosphatase-Associated Phosphoprotein (LPAP) That Are Involved in Human Lymphocyte Activation. Mol Biol 2019. [DOI: 10.1134/s002689331905011x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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11
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Yu ZH, Zhang ZY. Regulatory Mechanisms and Novel Therapeutic Targeting Strategies for Protein Tyrosine Phosphatases. Chem Rev 2018; 118:1069-1091. [PMID: 28541680 PMCID: PMC5812791 DOI: 10.1021/acs.chemrev.7b00105] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
An appropriate level of protein phosphorylation on tyrosine is essential for cells to react to extracellular stimuli and maintain cellular homeostasis. Faulty operation of signal pathways mediated by protein tyrosine phosphorylation causes numerous human diseases, which presents enormous opportunities for therapeutic intervention. While the importance of protein tyrosine kinases in orchestrating the tyrosine phosphorylation networks and in target-based drug discovery has long been recognized, the significance of protein tyrosine phosphatases (PTPs) in cellular signaling and disease biology has historically been underappreciated, due to a large extent to an erroneous assumption that they are largely constitutive and housekeeping enzymes. Here, we provide a comprehensive examination of a number of regulatory mechanisms, including redox modulation, allosteric regulation, and protein oligomerization, that control PTP activity. These regulatory mechanisms are integral to the myriad PTP-mediated biochemical events and reinforce the concept that PTPs are indispensable and specific modulators of cellular signaling. We also discuss how disruption of these PTP regulatory mechanisms can cause human diseases and how these diverse regulatory mechanisms can be exploited for novel therapeutic development.
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Affiliation(s)
- Zhi-Hong Yu
- Department of Medicinal Chemistry and Molecular Pharmacology, Department of Chemistry, Center for Cancer Research, and Institute for Drug Discovery, Purdue University, 720 Clinic Drive, West Lafayette, IN 47907
| | - Zhong-Yin Zhang
- Department of Medicinal Chemistry and Molecular Pharmacology, Department of Chemistry, Center for Cancer Research, and Institute for Drug Discovery, Purdue University, 720 Clinic Drive, West Lafayette, IN 47907
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12
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Kruglova NA, Meshkova TD, Kopylov AT, Mazurov DV, Filatov AV. Constitutive and activation-dependent phosphorylation of lymphocyte phosphatase-associated phosphoprotein (LPAP). PLoS One 2017; 12:e0182468. [PMID: 28827793 PMCID: PMC5565103 DOI: 10.1371/journal.pone.0182468] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2017] [Accepted: 07/19/2017] [Indexed: 12/15/2022] Open
Abstract
Lymphocyte phosphatase-associated phosphoprotein (LPAP) is a small transmembrane protein expressed exclusively in lymphocytes. LPAP is a component of a supramolecular complex composed of the phosphatase CD45, the co-receptor CD4, and the kinase Lck. In contrast to its immunologically important partners, the function of LPAP is unknown. We hypothesized that the biological role of LPAP may be determined by analyzing LPAP phosphorylation. In the present study, we identified LPAP phosphorylation sites by site-directed mutagenesis, phospho-specific antibodies, and protein immunoprecipitation coupled to mass spectrometry analysis. Our results confirmed previous reports that Ser-99, Ser-153, and Ser-163 are phosphorylated, as well as provided evidence for the phosphorylation of Ser-172. Using various SDS-PAGE techniques, we detected and quantified a set of LPAP phosphoforms that were assigned to a combination of particular phosphorylation events. The phosphorylation of LPAP appears to be a tightly regulated process. Our results support the model: following phorbol 12-myristate 13-acetate (PMA) or TCR/CD3 activation of T cells, LPAP is rapidly dephosphorylated at Ser-99 and Ser-172 and slowly phosphorylated at Ser-163. Ser-153 exhibited a high basal level of phosphorylation in both resting and activated cells. Therefore, we suggest that LPAP may function as a co-regulator of T-cell signaling.
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13
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Hojyo S, Fukada T. Zinc transporters and signaling in physiology and pathogenesis. Arch Biochem Biophys 2016; 611:43-50. [DOI: 10.1016/j.abb.2016.06.020] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Revised: 06/23/2016] [Accepted: 06/28/2016] [Indexed: 12/11/2022]
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14
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Roles of Zinc Signaling in the Immune System. J Immunol Res 2016; 2016:6762343. [PMID: 27872866 PMCID: PMC5107842 DOI: 10.1155/2016/6762343] [Citation(s) in RCA: 148] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Accepted: 08/11/2016] [Indexed: 02/07/2023] Open
Abstract
Zinc (Zn) is an essential micronutrient for basic cell activities such as cell growth, differentiation, and survival. Zn deficiency depresses both innate and adaptive immune responses. However, the precise physiological mechanisms of the Zn-mediated regulation of the immune system have been largely unclear. Zn homeostasis is tightly controlled by the coordinated activity of Zn transporters and metallothioneins, which regulate the transport, distribution, and storage of Zn. There is growing evidence that Zn behaves like a signaling molecule, facilitating the transduction of a variety of signaling cascades in response to extracellular stimuli. In this review, we highlight the emerging functional roles of Zn and Zn transporters in immunity, focusing on how crosstalk between Zn and immune-related signaling guides the normal development and function of immune cells.
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15
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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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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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Kleiman E, Salyakina D, De Heusch M, Hoek KL, Llanes JM, Castro I, Wright JA, Clark ES, Dykxhoorn DM, Capobianco E, Takeda A, Renauld JC, Khan WN. Distinct Transcriptomic Features are Associated with Transitional and Mature B-Cell Populations in the Mouse Spleen. Front Immunol 2015; 6:30. [PMID: 25717326 PMCID: PMC4324157 DOI: 10.3389/fimmu.2015.00030] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 01/15/2015] [Indexed: 11/30/2022] Open
Abstract
Splenic transitional B-cells (T1 and T2) are selected to avoid self-reactivity and to safeguard against autoimmunity, then differentiate into mature follicular (FO-I and FO-II) and marginal zone (MZ) subsets. Transcriptomic analysis by RNA-seq of the five B-cell subsets revealed T1 cell signature genes included RAG suggesting a potential for receptor revision. T1 to T2 B-cell differentiation was marked by a switch from Myb to Myc, increased expression of the PI3K adapter DAP10 and MHC class II. FO-II may be an intermediate in FO-I differentiation and may also become MZ B-cells as suggested by principle component analysis. MZ B-cells possessed the most distinct transcriptome including down-regulation of CD45 phosphatase-associated protein (CD45-AP/PTPRC-AP), as well as upregulation of IL-9R and innate molecules TLR3, TLR7, and bactericidal Perforin-2 (MPEG1). Among the endosomal TLRs, stimulation via TLR3 further enhanced Perforin-2 expression exclusively in MZ B-cells. Using gene-deleted and overexpressing transgenic mice we show that IL-9/IL-9R interaction resulted in rapid activation of STAT1, 3, and 5, primarily in MZ B-cells. Importantly, CD45-AP mutant mice had reduced transitional and increased mature MZ and FO B-cells, suggesting that it prevents premature entry of transitional B-cells to the mature B-cell pool or their survival and proliferation. Together, these findings suggest, developmental plasticity among splenic B-cell subsets, potential for receptor revision in peripheral tolerance whereas enhanced metabolism coincides with T2 to mature B-cell differentiation. Further, unique core transcriptional signatures in MZ B-cells may control their innate features.
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Affiliation(s)
- Eden Kleiman
- Department of Microbiology and Immunology, Miller School of Medicine, University of Miami , Miami, FL , USA
| | - Daria Salyakina
- Center for Computational Science, University of Miami , Miami, FL , USA
| | - Magali De Heusch
- Ludwig Institute for Cancer Research, Brussels Branch , Brussels , Belgium ; de Duve Institute, Université Catholique de Louvain , Brussels , Belgium
| | - Kristen L Hoek
- Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine , Nashville, TN , USA
| | - Joan M Llanes
- Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine , Nashville, TN , USA
| | - Iris Castro
- Department of Microbiology and Immunology, Miller School of Medicine, University of Miami , Miami, FL , USA
| | - Jacqueline A Wright
- Department of Microbiology and Immunology, Miller School of Medicine, University of Miami , Miami, FL , USA
| | - Emily S Clark
- Department of Microbiology and Immunology, Miller School of Medicine, University of Miami , Miami, FL , USA
| | - Derek M Dykxhoorn
- Hussman Institute for Human Genomics, University of Miami , Miami, FL , USA
| | - Enrico Capobianco
- Center for Computational Science, University of Miami , Miami, FL , USA
| | - Akiko Takeda
- Department of Pathology and Immunology, Washington University School of Medicine in St. Louis , St. Louis, MO , USA
| | - Jean-Christophe Renauld
- Ludwig Institute for Cancer Research, Brussels Branch , Brussels , Belgium ; de Duve Institute, Université Catholique de Louvain , Brussels , Belgium
| | - Wasif N Khan
- Department of Microbiology and Immunology, Miller School of Medicine, University of Miami , Miami, FL , USA
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18
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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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19
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Gaudreau MC, Heyd F, Bastien R, Wilhelm B, Möröy T. Alternative splicing controlled by heterogeneous nuclear ribonucleoprotein L regulates development, proliferation, and migration of thymic pre-T cells. THE JOURNAL OF IMMUNOLOGY 2012; 188:5377-88. [PMID: 22523384 DOI: 10.4049/jimmunol.1103142] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The regulation of posttranscriptional modifications of pre-mRNA by alternative splicing is important for cellular function, development, and immunity. The receptor tyrosine phosphatase CD45, which is expressed on all hematopoietic cells, is known for its role in the development and activation of T cells. CD45 is known to be alternatively spliced, a process that is partially regulated by heterogeneous nuclear ribonucleoprotein (hnRNP) L. To investigate the role of hnRNP L further, we have generated conditional hnRNP L knockout mice and found that LckCre-mediated deletion of hnRNP L results in a decreased thymic cellularity caused by a partial block at the transition stage between double-negative 4 and double-positive cells. In addition, hnRNP L(-/-) thymocytes express aberrant levels of the CD45RA splice isoforms and show high levels of phosphorylated Lck at the activator tyrosine Y394, but lack phosphorylation of the inhibitory tyrosine Y505. This indicated an increased basal Lck activity and correlated with higher proliferation rates of double-negative 4 cells in hnRNP L(-/-) mice. Deletion of hnRNP L also blocked the migration and egress of single-positive thymocytes to peripheral lymphoid organs in response to sphingosine-1-phosphate and the chemokines CCL21 and CXCL12 very likely as a result of aberrant splicing of genes encoding GTPase regulators and proteins affecting cytoskeletal organization. Our results indicate that hnRNP L regulates T cell differentiation and migration by regulating pre-TCR and chemokine receptor signaling.
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20
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Tremper-Wells B, Resnick RJ, Zheng X, Holsinger LJ, Shalloway D. Extracellular domain dependence of PTPalpha transforming activity. Genes Cells 2010; 15:711-724. [PMID: 20545765 DOI: 10.1111/j.1365-2443.2010.01410.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Two isoforms of the transmembrane protein tyrosine phosphatase PTPalpha, which differ by nine amino acids in their extracellular regions, are expressed in a tissue-specific manner. Over-expression of the shorter isoform transforms rodent cells, and it has previously been reasonable to assume that this was a direct consequence of its dephosphorylation and activation of Src. Transformation by the longer wild-type isoform has not previously been studied. We tested the activities of both isoforms in NIH3T3 cells and found that, while both dephosphorylated and activated Src similarly, only the shorter isoform induced focus formation or anchorage-independent growth. Differences in phosphorylation of PTPalpha at its known regulatory sites, Grb2 binding to PTPalpha, phosphorylation level of focal adhesion kinase by PTPalpha, or overall localization were excluded as possible explanations for the differences in transforming activities. The results suggest that transformation by PTPalpha involves at least one function other than, or in addition to, its activation of Src and that this depends on PTPalpha's extracellular domain. Previous studies have suggested that PTPalpha might be a useful target in breast and colon cancer therapy, and the results presented here suggest that it may be advantageous to develop isoform-specific therapeutic reagents.
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Affiliation(s)
- Barbara Tremper-Wells
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Ross J Resnick
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Xinmin Zheng
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | | | - David Shalloway
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
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21
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A regulatory polymorphism at position -309 in PTPRCAP is associated with susceptibility to diffuse-type gastric cancer and gene expression. Neoplasia 2010; 11:1340-7. [PMID: 20019842 DOI: 10.1593/neo.91132] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2009] [Revised: 08/25/2009] [Accepted: 09/01/2009] [Indexed: 01/06/2023] Open
Abstract
PTPRCAP (CD45-AP) is a positive regulator of protein tyrosine phosphatase PTPRC (CD45), which activates Src family kinases implicated in tumorigenesis. Single-nucleotide polymorphism (SNP) rs869736 located at position -309 of the PTPRCAP promoter was associated with susceptibility to diffuse-type gastric cancer in the current case-control study. The minor-allele homozygote was significantly associated with a 2.5-fold increased susceptibility to diffuse-type gastric cancer (P = .0021, n = 252), but not to intestinal-type (P = .30, n = 178), versus the major-allele homozygote, when comparing unrelated Korean patients with healthy controls (n = 406). Nine other SNPs were in nearly perfect linkage disequilibrium (r(2) >or= 0.97) with this SNP, exhibiting the same association, and spread out for 26 kb on chromosome 11q13.1 covering RPS6KB2, PTPRCAP, CORO1B, and GPR152. Among the four genes, however, only PTPRCAP expression was affected by haplotypes of the 10 SNPs. Endogenous transcript levels of PTPRCAP were linearly correlated with copy numbers (0, 1, and 2) of the risk-haplotype (P = .0060) in 12 lymphoblastoid cells derived from blood samples, but those of the other three genes were not. Furthermore, the cancer-risk, minor-allele T of rs869736 increased both promoter activity and specific nuclear protein-binding affinity than the nonrisk, major-allele G in luciferase reporter and electrophoretic mobility shift assays, respectively. Accordingly, the minor allele of rs869736 in the PTPRCAP promoter is associated with increased susceptibility to diffuse-type gastric cancer by increasing PTPRCAP expression, possibly leading to activation of the oncogenic Src family kinases.
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22
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Ravine TJ, Polski JM, Jenkins J. Recognition of Naegleriae ameba surface protein epitopes by anti-human CD45 antibodies. Cytometry A 2010; 77:305-9. [PMID: 20151453 DOI: 10.1002/cyto.a.20865] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Phagocytosis is a highly conserved mechanism exhibited by both free-living amebas and mammalian blood cells. Similarities demonstrated by either cell type during engulfment of the same bacterial species may imply analogous surface proteins involved in receptor-mediated endocytosis. The increased availability of anti-human leukocyte antibodies or clusters of differentiation (CD) markers used in conjunction with flow cytometric (FCM) and/or immunohistochemical (IHC) analysis provides investigators with a relatively easy method to screen different cell populations for comparable plasma membrane proteins. In this study, we incubated Naegleria and Acanthamoeba amebas with several directly conjugated anti-human leukocyte monoclonal antibodies (mAb) for similarly recognized amebic epitopes. CD marker selection was based upon a recognized role of each mAb in phagocyte activation and/or uptake of bacteria. These included CD14, CD45, and CD206. In FCM, only one CD45 antibody demonstrated strong reactivity with both Naegleria fowleri and Naegleria gruberi that was not expressed in similarly tested Acanthamoeba species. Additional testing of N. gruberi by IHC demonstrated reactivity to a different CD45 antibody. Our results suggest a possible utility of using anti-human leukocyte antibodies to screen amebic cells for similarly expressed protein epitopes. In doing so, several important items must be considered when selecting potential mAbs for testing to increase the probability of a positive result.
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Affiliation(s)
- Terrence J Ravine
- Department of Biomedical Sciences, University of South Alabama, Mobile, Alabama 36688, USA.
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23
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Seki I, Suzuki M, Miyasaka N, Kohsaka H. Expression of CD45 isoforms correlates with differential proliferative responses of peripheral CD4+ and CD8+ T cells. Immunol Lett 2010; 129:39-46. [PMID: 20093141 DOI: 10.1016/j.imlet.2009.12.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2009] [Revised: 12/02/2009] [Accepted: 12/23/2009] [Indexed: 11/28/2022]
Abstract
CD4(+) T cells express IL-2 receptor complexes to the same level as CD8(+) T cells when the two T cell populations were stimulated simultaneously. However, the activation of downstream signaling molecules, such as Jaks, was increased in CD8(+) T cells. Although equivalent amounts of CD45, which acts as a Jak phosphatase, was expressed on the two T cell populations, those on the CD8(+) T cells have less protein tyrosine phosphatase activity than those on the CD4(+) T cells. Furthermore, we find that different CD45 isoforms dominate in the two populations; CD45RO on proliferating CD4(+) T cells and CD45RBC on proliferating CD8(+) T cells. In addition, NIH3T3 cells expressing the CD45RBC transgene had more phosphorylated Jak1 and grew faster than those with the CD45RO transgene. Thus, the expression of specific CD45 isoforms on T cells correlates with their proliferative response to IL-2, suggesting that controlling cells expressing specific CD45 isoforms could correct excessive or insufficient immune responses.
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Affiliation(s)
- Iwao Seki
- Department of Medicine and Rheumatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
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24
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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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25
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Krotov GI, Krutikova MP, Zgoda VG, Filatov AV. Profiling of the CD4 receptor complex proteins. BIOCHEMISTRY (MOSCOW) 2007; 72:1216-24. [DOI: 10.1134/s0006297907110077] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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26
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Bijian K, Zhang L, Shen SH. Collagen-mediated survival signaling is modulated by CD45 in Jurkat T cells. Mol Immunol 2007; 44:3682-90. [PMID: 17524482 DOI: 10.1016/j.molimm.2007.04.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2007] [Revised: 04/03/2007] [Accepted: 04/06/2007] [Indexed: 11/20/2022]
Abstract
T cell activation is a critical step in the development of a proper immune response to infection and inflammation. This dynamic process requires efficient T cell receptor signaling, which in turn is modulated by integrin receptor activation and the actin cytoskeleton. CD45 is a key player in T cell receptor mediated signal transduction. However, its exact role in integrin mediated signaling in T cells remains to be elucidated. The present study addresses the relationship between CD45 and beta1-integrin mediated survival signaling in the human T leukemic cell line Jurkat, in which collagen receptors alpha1 beta1 and alpha2 beta1 integrins are localized. Wild type (WT)-Jurkat T cells treated with collagen demonstrated increased cell proliferation and survival. Monitoring the intracellular signaling pathways activated by collagen in WT-Jurkat cells revealed increased focal adhesion kinase (FAK) and extracellular signal-regulated kinase (ERK) activation. Moreover, examination of the actin cytoskeleton of WT-Jurkat T cells treated with collagen demonstrated the presence of an organized cortical actin structure, reminiscent of the survival phenotype. This is in contrast to CD45-deficient J45.01 T cells, where collagen treatment failed to enhance cell proliferation/survival and was unable to stimulate FAK and ERK activity. In addition, the actin cytoskeleton of collagen treated J45.01 T cells was disorganized with cortical actin aggregates present throughout. The importance of an organized actin cytoskeleton to proper cell signaling and survival was further demonstrated by the inability of collagen treated WT-Jurkat cells to activate the FAK and ERK survival pathway in the presence of cytochalasin D, a cytoskeleton-disrupting drug. Consistently, addition of the CD45 specific inhibitor abolished collagen-stimulated FAK and ERK activation in WT-Jurkat cells, further depicting CD45 as the key mediator. Furthermore, collagen-mediated T cell signaling alone was able to activate IL-2 gene transcription devoid of concomitant T cell receptor activation. Taken together, these results are the first to demonstrate that CD45 is important in promoting cell survival by modulating integrin-mediated FAK/ERK signaling in Jurkat T cells and is involved in a distinct signal transduction pathway, separate from T cell receptor signaling, influencing T cell immune responses. Hence, this study will help further our knowledge about beta1-integrin mediated signaling in T cells, which may prove to be essential for the regulation of various T cell mediated immune responses.
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Affiliation(s)
- Krikor Bijian
- Mammalian Cell Genetics Group, Biotechnology Research Institute, National Research Council of Canada, 6100 Royalmount av., Montreal, Quebec H4P 2R2, Canada
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27
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Leitenberg D, Falahati R, Lu DD, Takeda A. CD45-associated protein promotes the response of primary CD4 T cells to low-potency T-cell receptor (TCR) stimulation and facilitates CD45 association with CD3/TCR and lck. Immunology 2007; 121:545-54. [PMID: 17428310 PMCID: PMC2265975 DOI: 10.1111/j.1365-2567.2007.02602.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Although it is clear that the CD45 tyrosine phosphatase is required for efficient T-cell activation and T-cell development, the factors that regulate CD45 function remain uncertain. Previous data have indicated that there is an association of CD45 with CD4 and the T-cell receptor (TCR) complex controlled by the variable ectodomain of CD45 and, following activation, by high- and low-potency peptides. This suggests that controlling substrate access to CD45 may be an important regulatory mechanism during T-cell activation. In the present study we have examined the role of the transmembrane adapter-like molecule CD45-associated protein (CD45-AP) in regulating the association of CD45 with CD3/TCR and lck, and in regulating primary CD4(+) T-lymphocyte activation. In CD4(+) T cells from CD45-AP-deficient mice, coimmunoprecipitation of CD45 with the CD3/TCR complex, in addition to lck, is significantly reduced compared with wild-type T cells. Functionally, this correlates with a decreased proliferative response, a decrease in interleukin (IL)-2 production, and a decrease in calcium flux upon stimulation with a low-potency altered peptide ligand. However, the response of CD45-AP-deficient T cells to stimulation with a high-avidity agonist peptide was largely intact, except for a modest decrease in IL-2 production. These data suggest that CD45-AP promotes or stabilizes the association of CD45 with substrates and regulates the threshold of T-cell activation.
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Affiliation(s)
- David Leitenberg
- Department of Microbiology, Immunology and Tropical Medicine, George Washington University Medical Center, Washington, DC 20037, USA.
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28
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Lee S, Faux C, Nixon J, Alete D, Chilton J, Hawadle M, Stoker AW. Dimerization of protein tyrosine phosphatase sigma governs both ligand binding and isoform specificity. Mol Cell Biol 2006; 27:1795-808. [PMID: 17178832 PMCID: PMC1820468 DOI: 10.1128/mcb.00535-06] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Signaling through receptor protein tyrosine phosphatases (RPTPs) can influence diverse processes, including axon development, lymphocyte activation, and cell motility. The molecular regulation of these enzymes, however, is still poorly understood. In particular, it is not known if, or how, the dimerization state of RPTPs is related to the binding of extracellular ligands. Protein tyrosine phosphatase sigma (PTPsigma) is an RPTP with major isoforms that differ in their complements of fibronectin type III domains and in their ligand-binding specificities. In this study, we show that PTPsigma forms homodimers in the cell, interacting at least in part through the transmembrane region. Using this knowledge, we provide the first evidence that PTPsigma ectodomains must be presented as dimers in order to bind heterophilic ligands. We also provide evidence of how alternative use of fibronectin type III domain complements in two major isoforms of PTPsigma can alter the ligand binding specificities of PTPsigma ectodomains. The data suggest that the alternative domains function largely to change the rotational conformations of the amino-terminal ligand binding sites of the ectodomain dimers, thus imparting novel ligand binding properties. These findings have important implications for our understanding of how heterophilic ligands interact with, and potentially regulate, RPTPs.
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Affiliation(s)
- Simon Lee
- Neural Development Unit, UCL Institute of Child Health, 30 Guilford Street, London WC1N 1EH, United Kingdom
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29
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Maes ML, Davidson LB, McDonagh PF, Ritter LS. Comparison of sample fixation and the use of LDS-751 or anti-CD45 for leukocyte identification in mouse whole blood for flow cytometry. J Immunol Methods 2006; 319:79-86. [PMID: 17187818 PMCID: PMC1896319 DOI: 10.1016/j.jim.2006.10.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2006] [Revised: 10/19/2006] [Accepted: 10/23/2006] [Indexed: 11/26/2022]
Abstract
Flow cytometry methods used to measure leukocyte function often entail sample preparation procedures that cause artifactual cell activation. To avoid leukocyte activation by isolation techniques, some preparation methods use fluorescent markers to discriminate leukocytes from erythrocytes in whole blood. One of these markers, laser dye styryl-751(LDS-751), has been used to distinguish leukocytes by staining nucleic acid, but has been found to stain other blood cells and dead cells indiscriminately. Thus, LDS-751 may not be an appropriate reagent for leukocyte identification in whole blood. Fixing samples with formaldehydes increases cell permeability and causes surface protein cross-linking that may alter staining of both intra- and extracellular markers. The degree of this sample alteration by formaldehyde fixation, however, remains in question. In addition, little is known about flow cytometry and sample preparation methods in mouse whole blood. The purpose of this study was to determine if labeling leukocytes with a monoclonal antibody specific to leukocyte common antigen (CD45) was superior to labeling with LDS-751 and to determine the effect of sample fixation on a mouse whole blood preparation for flow cytometry. Samples were incubated with CD16/CD32 Fc receptor blocker, and either 10 microg/ml LDS-751 or phosphate buffered saline (PBS). The samples were then fixed with paraformaldehyde or diluted with PBS followed by incubation with 5 microg/ml PerCP-conjugated anti-CD45, 5 microg/ml FITC-conjugated anti-CD11b, or 80 microM dichlorofluorescein diacetate. We found that samples labeled with LDS-751 demonstrated decreased fluorescence intensity for granulocyte CD11b expression and ROS production compared to samples labeled with anti-CD45. In addition, sample fixation decreased mean fluorescence intensity in samples labeled with either LDS-751 or anti-CD45. We conclude that labeling leukocytes with monoclonal antibody CD45 in a mouse whole blood preparation is preferable, as it provides improved measurement of leukocyte indices compared to LDS-751. Also, while sample fixation prior to antibody staining caused a decrease in overall fluorescence; it can be used to successfully identify extra-cellular markers.
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Affiliation(s)
- Melissa L Maes
- College of Nursing, The University of Arizona, Tucson, Arizona 85724, USA.
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30
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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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Abstract
CD45 has been recognized as an important player in regulating signalling in lymphocytes. However, compared with tyrosine kinases, phosphatases are still poorly understood in terms of the details of their specificity and regulation. Here, the recent progress in understanding the biology of the first recognized receptor tyrosine phosphatase, CD45, is reviewed.
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Affiliation(s)
- Nick Holmes
- Division of Immunology, Department of Pathology, Cambridge University, UK.
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32
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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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Chin CN, Sachs JN, Engelman DM. Transmembrane homodimerization of receptor-like protein tyrosine phosphatases. FEBS Lett 2005; 579:3855-8. [PMID: 15978577 DOI: 10.1016/j.febslet.2005.05.071] [Citation(s) in RCA: 45] [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: 04/28/2005] [Accepted: 05/18/2005] [Indexed: 11/21/2022]
Abstract
Receptor-like protein tyrosine phosphatases (RPTPs) are type I integral membrane proteins. Together with protein tyrosine kinases, RPTPs regulate the phosphotyrosine levels in the cell. Studies of two RPTPs, CD45 and PTPalpha, have provided strong evidence that dimerization leads to inactivation of the receptors, and that the dimerization of PTPalpha involves interactions in the transmembrane domain (TMD). Using the TOXCAT assay, a genetic approach for analyzing TM interactions in Escherichia coli membranes, we show that the TMD of RPTPs interact in the membrane, albeit to different extents. Using fusion proteins of TMDs, we also observe an equilibrium between monomer and dimer in sodium dodecyl sulfate (SDS) micelles. Through a mutational study of the DEP1 TMD, we demonstrate that these interactions are specific. Taken together, our results define a subset of the RPTP family in which TM homodimerization may act as a mediator of protein function.
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Affiliation(s)
- Chen-Ni Chin
- Department of Molecular Biophysics and Biochemistry, School of Medicine, Yale University, 266 Whitney Avenue, P.O. Box 208114, New Haven, CT 06520-8114, United States
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34
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Li D, Brackenridge S, Screaton GR. A novel CD45 transcript involving the alternative splicing of a new exon is widely distributed in lymphoid tissues. Hum Immunol 2005; 65:1539-45. [PMID: 15603882 DOI: 10.1016/j.humimm.2004.08.181] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2004] [Revised: 07/19/2004] [Accepted: 08/17/2004] [Indexed: 11/19/2022]
Abstract
Protein tyrosine phosphatase CD45 is a key player in T-cell receptor signaling and lymphocyte development. Differential expression of multiple CD45 isoforms resulting from the alternative splicing of exons A, B, and C, which encode part of the extracellular domain, is an important feature of CD45 expression. We report a novel isoform that results from the alternative splicing of a previously undiscovered exon between the constitutively spliced exon 3 and the alternatively spliced exon A. This 123-bpâ€:#x0093:long exon encodes 41 amino acids and is unlikely to undergo te extensive glycosylation seen for the regions encoded by exons A, B, and C. Reverse transcriptase polymerase chain reaction demonstrates that this isoform is expressed in human peripheral blood mononuclear cells and cell lines of lymphoid origin, but with a clearly different pattern to that of the isoforms caused by exons A, B, and C, implying a different regulatory mechanism.
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Affiliation(s)
- Demin Li
- Nuffield Department of Medicine and MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Oxford University, Oxford, United Kingdom
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