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Molyneaux K, Laggner C, Vincent J, Brady-Kalnay S. Small molecule antagonists of PTPmu identified by artificial intelligence-based computational screening block glioma cell migration and growth. PLoS One 2023; 18:e0288980. [PMID: 37494327 PMCID: PMC10370706 DOI: 10.1371/journal.pone.0288980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Accepted: 07/07/2023] [Indexed: 07/28/2023] Open
Abstract
PTPmu (PTPμ) is a member of the receptor protein tyrosine phosphatase IIb family that participates in both homophilic cell-cell adhesion and signaling. PTPmu is proteolytically downregulated in glioblastoma generating extracellular and intracellular fragments that have oncogenic activity. The intracellular fragments, in particular, are known to accumulate in the cytoplasm and nucleus where they interact with inappropriate binding partners/substrates generating signals required for glioma cell migration and growth. Thus, interfering with these fragments is an attractive therapeutic strategy. To develop agents that target these fragments, we used the AI-based AtomNetⓇ model, a drug design and discovery tool, to virtually screen molecular libraries for compounds able to target a binding pocket bordered by the wedge domain, a known regulatory motif located within the juxtamembrane portion of the protein. Seventy-four high-scoring and chemically diverse virtual hits were then screened in multiple cell-based assays for effects on glioma cell motility (scratch assays) and growth in 3D culture (sphere assays), and PTPmu-dependent adhesion (Sf9 aggregation). We identified three inhibitors (247678835, 247682206, 247678791) that affected the motility of multiple glioma cell lines (LN229, U87MG, and Gli36delta5), the growth of LN229 and Gli36 spheres, and PTPmu-dependent Sf9 aggregation. Compound 247678791 was further shown to suppress PTPmu enzymatic activity in an in vitro phosphatase assay, and 247678835 was able to inhibit the growth of human glioma tumors in mice. We propose that these three compounds are PTPmu-targeting agents with therapeutic potential for treating glioblastoma.
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Affiliation(s)
- Kathleen Molyneaux
- Department of Molecular Biology & Microbiology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | | | - Jason Vincent
- Department of Molecular Biology & Microbiology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Susann Brady-Kalnay
- Department of Molecular Biology & Microbiology, Case Western Reserve University, Cleveland, Ohio, United States of America
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2
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Zhang X, Yang S, Li X, Zhu P, Xie E, Li Z. Expression, purification, and characterization of a novel acid phosphatase that displays protein tyrosine phosphatases activity from Metarhizium anisopliae strain CQMa102. Biosci Biotechnol Biochem 2017; 81:2292-2300. [DOI: 10.1080/09168451.2017.1378087] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Abstract
The protein tyrosine phosphatase (PTPase) plays an important role in insect immune system. Our group has purified a type of acid phosphatase that could specifically dephosphorylate trans-Golgi p230 in vitro. In order to study this phosphatase further, we have identified and cloned the phosphatase gene from a locust specific Metarhizium anisopliae Strain CQMa102. The CQMa102 phosphatase was expressed in Pichia pastoris to verify its protease activity. The molecular weight (MW) and the isoelectric point (pI) of the phosphatase were about 85 kDa and 6.15, respectively. Substrate specificity evaluation showed that the purified enzyme exhibited high activity on O-phospho-L-tyrosine. At its optimal pH of 6.5 and optimum temperature of 70 °C, the protein showed the highest activity respectively. It can be activated by Ca2+, Mg2+, Mn2+, Ba2+, Co2+ and phosphate analogs, but inhibited by Zn2+, Cu2+, fluoride, dithiothreitol, β-mercaptoethanol and N-ethylmaleimide.
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Affiliation(s)
- Xue Zhang
- Chongqing Key Laboratory of Soil Multi-scale Interfacial Process, College of Resources and Environment, Southwest University, Chongqing, China
| | - Shuiying Yang
- College of Plant Protection, Southwest University, Chongqing, China
| | - Xinqiang Li
- Chongqing Key Laboratory of Soil Multi-scale Interfacial Process, College of Resources and Environment, Southwest University, Chongqing, China
| | - Pei Zhu
- Chongqing Key Laboratory of Soil Multi-scale Interfacial Process, College of Resources and Environment, Southwest University, Chongqing, China
| | - Enyu Xie
- Chongqing Key Laboratory of Soil Multi-scale Interfacial Process, College of Resources and Environment, Southwest University, Chongqing, China
| | - Zhenlun Li
- Chongqing Key Laboratory of Soil Multi-scale Interfacial Process, College of Resources and Environment, Southwest University, Chongqing, China
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3
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Phillips-Mason PJ, Craig SEL, Brady-Kalnay SM. A protease storm cleaves a cell-cell adhesion molecule in cancer: multiple proteases converge to regulate PTPmu in glioma cells. J Cell Biochem 2015; 115:1609-23. [PMID: 24771611 DOI: 10.1002/jcb.24824] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Accepted: 04/24/2014] [Indexed: 01/15/2023]
Abstract
Cleavage of the cell-cell adhesion molecule, PTPµ, occurs in human glioblastoma multiforme brain tumor tissue and glioma cell lines. PTPµ cleavage is linked to increased cell motility and growth factor independent survival of glioma cells in vitro. Previously, PTPµ was shown to be cleaved by furin in the endoplasmic reticulum to generate membrane associated E- (extracellular) and P- (phosphatase) subunits, and by ADAMs and the gamma secretase complex at the plasma membrane. We also identified the presence of additional extracellular and intracellular PTPµ fragments in brain tumors. We set out to biochemically analyze PTPµ cleavage in cancer cells. We determined that, in addition to the furin-processed form of PTPµ, a pool of 200 kDa full-length PTPµ exists at the plasma membrane that is cleaved directly by ADAM to generate a larger shed form of the PTPµ extracellular segment. Notably, in glioma cells, full-length PTPµ is also subject to calpain cleavage, which generates novel PTPµ fragments not found in other immortalized cells. We also observed glycosylation and phosphorylation differences in the cancer cells. Our data suggest that an additional serine protease also contributes to PTPµ shedding in glioma cells. We hypothesize that a "protease storm" occurs in cancer cells whereby multiple proteases converge to reduce the presence of cell-cell adhesion molecules at the plasma membrane and to generate protein fragments with unique biological functions. As a consequence, the "protease storm" could promote the migration and invasion of tumor cells.
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Affiliation(s)
- Polly J Phillips-Mason
- Department of Molecular Biology and Microbiology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, 44106-4960
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Li Z, Wang Z, Peng G, Yin Y, Zhao H, Cao Y, Xia Y. Purification and Characterization of a Novel Thermostable Extracellular Protein Tyrosine Phosphatase fromMetarhizium anisopliaeStrain CQMa102. Biosci Biotechnol Biochem 2014; 70:1961-8. [PMID: 16926509 DOI: 10.1271/bbb.60136] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
An extracellular phosphatase was purified to homogeneity from the entomopathogenic fungus Metarhizium anisopliae with a 41.0% yield. The molecular mass and isoelectric point of the purified enzyme were about 82.5 kDa and 9.5 respectively. The optimum pH and temperature were about 5.5 and 75 degrees C when using O-phospho-L-tyrosine as substrate. The protein displayed high stability in a pH range 3.0-9.5 at 30 degrees C and was remarkably thermostable at 70 degrees C. The purified enzyme showed high activity on O-phospho-L-tyrosine and protein tyrosine phosphatase substrate monophosphate (a specific substrate of protein tyrosine phosphatase). Although one peptide of the phosphatase shared identity with one alkaline phosphatase of Neurospora crassa, its substrate specificity and inhibitor sensitivity indicate that the enzyme is a protein tyrosine phosphatase.
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Affiliation(s)
- Zhenlun Li
- Genetic Engineering Research Center, Bioengineering College, Chongqing University, R. P. China
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5
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Köhn M, Gutierrez-Rodriguez M, Jonkheijm P, Wetzel S, Wacker R, Schroeder H, Prinz H, Niemeyer CM, Breinbauer R, Szedlacsek SE, Waldmann H. A microarray strategy for mapping the substrate specificity of protein tyrosine phosphatase. Angew Chem Int Ed Engl 2007; 46:7700-3. [PMID: 17726672 DOI: 10.1002/anie.200701601] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Maja Köhn
- Department of Chemical Biology, Max-Planck Institute für molekulare Physiologie, Otto Hahn Strasse 11, 44227 Dortmund, Germany
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6
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Noordman YE, Augustus ED, Schepens JTG, Chirivi RGS, Ríos P, Pulido R, Hendriks WJAJ. Multimerisation of receptor-type protein tyrosine phosphatases PTPBR7 and PTP-SL attenuates enzymatic activity. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2007; 1783:275-86. [PMID: 18068678 DOI: 10.1016/j.bbamcr.2007.10.023] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2007] [Revised: 10/22/2007] [Accepted: 10/30/2007] [Indexed: 11/16/2022]
Abstract
Dimerisation of receptor-type protein tyrosine phosphatases (RPTPs) represents an appealing mechanism to regulate their enzymatic activity. Studies thus far mostly concern the dimerisation behaviour of RPTPs possessing two tandemly oriented catalytic PTP domains. Mouse gene Ptprr encodes four different protein isoforms (i.e. PTPBR7, PTP-SL and PTPPBSgamma-42/37) that contain a single PTP domain. Using selective membrane permeabilisation we here demonstrate that PTP-SL, like PTPBR7, is a single membrane-spanning RPTP. Furthermore, these two receptor-type PTPs constitutively formed homo- and hetero-meric complexes as witnessed in chemical cross-linking and co-immunoprecipitation experiments, in sharp contrast to the cytosolic PTPPBSgamma-42 and PTPPBSgamma-37 PTPRR isoforms. This multimerisation occurs independently of the PTP domain and requires the transmembrane domain and/or the proximal hydrophobic region. Using overexpression of a PTPBR7 mutant that essentially lacks the intracellular PTP domain-containing segment, a monomer-mimicking state was forced upon full-length PTPBR7 immunoprecipitates. This resulted in a significant increase in the enzymatic activity of the PTPRR PTP domain, which strengthens the notion that multimerisation represents a general mechanism to tone down RPTP catalytic activity.
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Affiliation(s)
- Yvet E Noordman
- Department of Cell Biology, Radboud University Nijmegen Medical Centre, Geert Grooteplein 28, 6525 GA Nijmegen, The Netherlands
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Köhn M, Gutierrez-Rodriguez M, Jonkheijm P, Wetzel S, Wacker R, Schroeder H, Prinz H, Niemeyer C, Breinbauer R, Szedlacsek S, Waldmann H. Eine Mikroarray-Strategie zur Untersuchung der Substratspezifitäten von Protein-Tyrosin-Phosphatasen. Angew Chem Int Ed Engl 2007. [DOI: 10.1002/ange.200701601] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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8
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Aricescu AR, Hon WC, Siebold C, Lu W, van der Merwe PA, Jones EY. Molecular analysis of receptor protein tyrosine phosphatase mu-mediated cell adhesion. EMBO J 2006; 25:701-12. [PMID: 16456543 PMCID: PMC1383555 DOI: 10.1038/sj.emboj.7600974] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2005] [Accepted: 01/09/2006] [Indexed: 01/07/2023] Open
Abstract
Type IIB receptor protein tyrosine phosphatases (RPTPs) are bi-functional cell surface molecules. Their ectodomains mediate stable, homophilic, cell-adhesive interactions, whereas the intracellular catalytic regions can modulate the phosphorylation state of cadherin/catenin complexes. We describe a systematic investigation of the cell-adhesive properties of the extracellular region of RPTPmu, a prototypical type IIB RPTP. The crystal structure of a construct comprising its N-terminal MAM (meprin/A5/mu) and Ig domains was determined at 2.7 A resolution; this assigns the MAM fold to the jelly-roll family and reveals extensive interactions between the two domains, which form a rigid structural unit. Structure-based site-directed mutagenesis, serial domain deletions and cell-adhesion assays allowed us to identify the four N-terminal domains (MAM, Ig, fibronectin type III (FNIII)-1 and FNIII-2) as a minimal functional unit. Biophysical characterization revealed at least two independent types of homophilic interaction which, taken together, suggest that there is the potential for formation of a complex and possibly ordered array of receptor molecules at cell contact sites.
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Affiliation(s)
- Alexandru Radu Aricescu
- Division of Structural Biology, Henry Wellcome Building of Genomic Medicine, University of Oxford, Oxford, UK
| | - Wai-Ching Hon
- Division of Structural Biology, Henry Wellcome Building of Genomic Medicine, University of Oxford, Oxford, UK
| | - Christian Siebold
- Division of Structural Biology, Henry Wellcome Building of Genomic Medicine, University of Oxford, Oxford, UK
| | - Weixian Lu
- Division of Structural Biology, Henry Wellcome Building of Genomic Medicine, University of Oxford, Oxford, UK
| | | | - Edith Yvonne Jones
- Division of Structural Biology, Henry Wellcome Building of Genomic Medicine, University of Oxford, Oxford, UK
- CR-UK Receptor Structure Research Group, Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK. Tel.: +44 1865 287546; Fax: +44 1865 287547; E-mail:
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9
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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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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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11
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Gross S, Blanchetot C, Schepens J, Albet S, Lammers R, den Hertog J, Hendriks W. Multimerization of the protein-tyrosine phosphatase (PTP)-like insulin-dependent diabetes mellitus autoantigens IA-2 and IA-2beta with receptor PTPs (RPTPs). Inhibition of RPTPalpha enzymatic activity. J Biol Chem 2002; 277:48139-45. [PMID: 12364328 DOI: 10.1074/jbc.m208228200] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Most receptor-type protein-tyrosine phosphatases (RPTPs) contain two tandem PTP domains. For some RPTPs the enzymatically inactive membrane-distal phosphatase domains (D2) were found to bind enzymatically active membrane proximal PTP (D1) domains, and oligomerization has been proposed as a general regulatory mechanism. The RPTP-like proteins IA-2 and IA-2beta, major autoantigens in insulin-dependent diabetes mellitus, contain just a single enzymatically inactive PTP-like domain. Their physiological role is as yet enigmatic. To investigate whether the catalytically inactive cytoplasmic domains of IA-2 and IA-2beta are involved in oligomerization, we exploited interaction trap assay in yeast and glutathione S-transferase pull-down and co-immunoprecipitation strategies on lysates of transfected COS-1 cells. The results show that IA-2 and IA-2beta are capable of homo- and heterodimerization to which both the juxtamembrane region and the phosphatase-like segment can contribute. Furthermore, they can form heterodimers with some other RPTP members, most notably RPTPalpha and RPTPepsilon, and down-regulate RPTPalpha enzymatic activity. Thus, in addition to homo-dimerization, the enzymatic activity of receptor-type PTPs can be regulated through heterodimerization with other RPTPs, including the catalytically inactive IA-2 and IA-2beta.
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Affiliation(s)
- Steffen Gross
- Department of Cell Biology, Nijmegen Center for Molecular Life Sciences, University of Nijmegen, The Netherlands
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12
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Blanchetot C, Tertoolen LG, Overvoorde J, den Hertog J. Intra- and intermolecular interactions between intracellular domains of receptor protein-tyrosine phosphatases. J Biol Chem 2002; 277:47263-9. [PMID: 12376545 DOI: 10.1074/jbc.m205810200] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The presence of two protein-tyrosine phosphatase (PTP) domains is a striking feature in most transmembrane receptor PTPs (RPTPs). The generally inactive membrane-distal PTP domains (RPTP-D2s) bind and are proposed to regulate the membrane-proximal PTP domains (RPTP-D1s). We set out to characterize the interactions between RPTP-D1s and RPTP-D2s in vivo by co-immunoprecipitation of hemagglutinin-tagged fusion proteins encoding the transmembrane domain and RPTP-D1 and myc-tagged RPTP-D2. Seven RPTPs from four different subfamilies were used: RPTPalpha, RPTPepsilon, LAR, RPTPvarsigma, RPTPdelta, CD45, and RPTP(mu). We found that RPTP-D2s bound to RPTPs with different affinities. The presence of intrinsic RPTP-D2 altered the binding specificity toward other RPTP-D2s positively or negatively, depending on the identity of the RPTPs. Furthermore, the C terminus of RPTP-D2s and the "wedge" in RPTP-D1s played a central role in binding specificity. Finally, full-length RPTPalpha and LAR heterodimerized in an oxidative stress-dependent manner. Like RPTPalpha-D2, the LAR-D2 conformation was affected by oxidative stress, suggesting a common regulatory mechanism for RPTP complex formation. Taken together, interactions between RPTP-D1s and RPTP-D2s are a common but specific mechanism that is likely to be regulated. The RPTP-D2s and the wedge structures are crucial determinants of binding specificity, thus regulating cross-talk between RPTPs.
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Affiliation(s)
- Christophe Blanchetot
- Hubrecht Laboratory, Netherlands Institute for Developmental Biology, Uppsalalaan 8, Utrecht 3584 CT, The Netherlands
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Blanchetot C, Tertoolen LG, den Hertog J. Regulation of receptor protein-tyrosine phosphatase alpha by oxidative stress. EMBO J 2002; 21:493-503. [PMID: 11847098 PMCID: PMC125870 DOI: 10.1093/emboj/21.4.493] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The presence of two protein-tyrosine phosphatase (PTP) domains is a striking feature in most transmembrane receptor PTPs (RPTPs). The function of the generally inactive membrane-distal PTP domain (RPTP-D2) is unknown. Here we report that an intramolecular interaction between the spacer region (Sp) and the C-terminus in RPTPalpha prohibited intermolecular interactions. Interestingly, stress factors such as H(2)O(2), UV and heat shock induced reversible, free radical-dependent, intermolecular interactions between RPTPalpha and RPTPalpha-SpD2, suggesting an inducible switch in conformation and binding. The catalytic site cysteine of RPTPalpha-SpD2, Cys723, was required for the H(2)O(2) effect on RPTPalpha. H(2)O(2) induced a rapid, reversible, Cys723-dependent conformational change in vivo, as detected by fluorescence resonance energy transfer, with cyan fluorescent protein (CFP) and yellow fluorescent protein (YFP) flanking RPTPalpha-SpD2 in a single chimeric protein. Importantly, H(2)O(2) treatment stabilized RPTPalpha dimers, resulting in inactivation. We propose a model in which oxidative stress induces a conformational change in RPTPalpha-D2, leading to stabilization of RPTPalpha dimers, and thus to inhibition of RPTPalpha activity.
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Affiliation(s)
| | | | - Jeroen den Hertog
- Hubrecht Laboratory, Netherlands Institute for Developmental Biology, Uppsalalaan 8, NL-3584 CT Utrecht, The Netherlands
Corresponding author e-mail:
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Szedlacsek SE, Aricescu AR, Fulga TA, Renault L, Scheidig AJ. Crystal structure of PTP-SL/PTPBR7 catalytic domain: implications for MAP kinase regulation. J Mol Biol 2001; 311:557-68. [PMID: 11493009 DOI: 10.1006/jmbi.2001.4890] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Protein tyrosine phosphatases PTP-SL and PTPBR7 are isoforms belonging to cytosolic membrane-associated and to receptor-like PTPs (RPTPs), respectively. They represent a new family of PTPs with a major role in activation and translocation of MAP kinases. Specifically, the complex formation between PTP-SL and ERK2 involves an unusual interaction leading to the phosphorylation of PTP-SL by ERK2 at Thr253 and the inactivating dephosphorylation of ERK2 by PTP-SL. This interaction is strictly dependent upon a kinase interaction motif (KIM) (residues 224-239) situated at the N terminus of the PTP-SL catalytic domain. We report the first crystal structure of the catalytic domain for a member of this family (PTP-SL, residues 254-549, identical with residues 361-656 of PTPBR7), providing an example of an RPTP with single cytoplasmic domain, which is monomeric, having an unhindered catalytic site. In addition to the characteristic PTP-core structure, PTP-SL has an N-terminal helix, possibly orienting the KIM motif upon interaction with the target ERK2. An unusual residue in the catalytically important WPD loop promotes formation of a hydrophobically and electrostatically stabilised clamp. This could induce increased rigidity to the WPD loop and therefore reduced catalytic activity, in agreement with our kinetic measurements. A docking model based on the PTP-SL structure suggests that, in the complex with ERK2, the phosphorylation of PTP-SL should be accomplished first. The subsequent dephosphorylation of ERK2 seems to be possible only if a conformational rearrangement of the two interacting partners takes place.
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Affiliation(s)
- S E Szedlacsek
- Department of Enzymology, Institute of Biochemistry, Spl. Independentei 296, Bucharest, 77700, Romania.
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