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Chen X, Li Y, Xu J, Cui Y, Wu Q, Yin H, Li Y, Gao C, Jiang L, Wang H, Wen Z, Yao Z, Wu Z. Styxl2 regulates de novo sarcomere assembly by binding to non-muscle myosin IIs and promoting their degradation. eLife 2024; 12:RP87434. [PMID: 38829202 PMCID: PMC11147509 DOI: 10.7554/elife.87434] [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: 06/05/2024] Open
Abstract
Styxl2, a poorly characterized pseudophosphatase, was identified as a transcriptional target of the Jak1-Stat1 pathway during myoblast differentiation in culture. Styxl2 is specifically expressed in vertebrate striated muscles. By gene knockdown in zebrafish or genetic knockout in mice, we found that Styxl2 plays an essential role in maintaining sarcomere integrity in developing muscles. To further reveal the functions of Styxl2 in adult muscles, we generated two inducible knockout mouse models: one with Styxl2 being deleted in mature myofibers to assess its role in sarcomere maintenance, and the other in adult muscle satellite cells (MuSCs) to assess its role in de novo sarcomere assembly. We find that Styxl2 is not required for sarcomere maintenance but functions in de novo sarcomere assembly during injury-induced muscle regeneration. Mechanistically, Styxl2 interacts with non-muscle myosin IIs, enhances their ubiquitination, and targets them for autophagy-dependent degradation. Without Styxl2, the degradation of non-muscle myosin IIs is delayed, which leads to defective sarcomere assembly and force generation. Thus, Styxl2 promotes de novo sarcomere assembly by interacting with non-muscle myosin IIs and facilitating their autophagic degradation.
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Affiliation(s)
- Xianwei Chen
- Division of Life Science, Hong Kong University of Science & TechnologyHong KongChina
| | - Yanfeng Li
- Division of Life Science, Hong Kong University of Science & TechnologyHong KongChina
| | - Jin Xu
- Division of Life Science, Hong Kong University of Science & TechnologyHong KongChina
| | - Yong Cui
- School of Life Sciences, Chinese University of Hong KongHong KongChina
| | - Qian Wu
- Department of Applied Biology and Chemical Technology, Hong Kong Polytechnic UniversityHong KongChina
| | - Haidi Yin
- Department of Applied Biology and Chemical Technology, Hong Kong Polytechnic UniversityHong KongChina
| | - Yuying Li
- Department of Orthopaedics and Traumatology, Li Ka Shing Institute of Health Sciences, Chinese University of Hong KongHong KongChina
| | - Chuan Gao
- Division of Life Science, Hong Kong University of Science & TechnologyHong KongChina
| | - Liwen Jiang
- School of Life Sciences, Chinese University of Hong KongHong KongChina
| | - Huating Wang
- Department of Orthopaedics and Traumatology, Li Ka Shing Institute of Health Sciences, Chinese University of Hong KongHong KongChina
| | - Zilong Wen
- Division of Life Science, Hong Kong University of Science & TechnologyHong KongChina
| | - Zhongping Yao
- Department of Applied Biology and Chemical Technology, Hong Kong Polytechnic UniversityHong KongChina
| | - Zhenguo Wu
- Division of Life Science, Hong Kong University of Science & TechnologyHong KongChina
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2
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Hinton SD. Understanding Pseudophosphatase Function Through Biochemical Interactions. Methods Mol Biol 2024; 2743:21-41. [PMID: 38147206 DOI: 10.1007/978-1-0716-3569-8_2] [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] [Indexed: 12/27/2023]
Abstract
Pseudophosphatases have been solidified as important signaling molecules that regulate signal transduction cascades. However, their mechanisms of action remain enigmatic. Reflecting this mystery, the prototypical pseudophosphatase STYX (phospho-serine-threonine/tyrosine-binding protein) was named with allusion to the river of the dead in Greek mythology to emphasize that these molecules are "dead" phosphatases. Although proteins with STYX domains do not catalyze dephosphorylation, this does not preclude their having other functions, including as integral elements of signaling networks. Thus, understanding their roles may mark them as potential novel drug targets. This chapter outlines common strategies used to characterize the functions of pseudophosphatases, using as an example MK-STYX [MAPK (mitogen-activated protein kinase) phospho-serine-threonine/tyrosine-binding], which has been linked to tumorigenesis, hepatocellular carcinoma, glioblastoma, apoptosis, and neuronal differentiation. We start with the importance of "restoring" (when possible) phosphatase activity in a pseudophosphatase, so the active mutant may be used as a comparison control throughout immunoprecipitation and mass spectrometry analyses. To this end, we provide protocols for site-directed mutagenesis, mammalian cell transfection, co-immunoprecipitation, phosphatase activity assays, and immunoblotting that we have used to investigate MK-STYX and the active mutant MK-STYXactive. We also highlight the importance of utilizing RNA interference (RNAi) "knockdown" technology to determine a cellular phenotype in various cell lines. Therefore, we outline our protocols for introducing short hairpin RNA (shRNA) expression plasmids into mammalian cells and quantifying knockdown of gene expression with real-time quantitative PCR (qPCR). We also provide a bioinformatic approach to investigating MK-STYX and MK-STYX(active mutant). These bioinformatic approaches can stand alone experimentally but also complement and enhance "wet" bench approaches such as binding assays and/or activity assays. A combination of cellular, molecular, biochemical, proteomic, and bioinformatic techniques has been a powerful tool in identifying novel functions of MK-STYX. Likewise, the information provided here should be a helpful guide to elucidating the functions of other pseudophosphatases.
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Affiliation(s)
- Shantá D Hinton
- Department of Biology, College of William and Mary, Williamsburg, VA, USA.
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3
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Pseudophosphatases as Regulators of MAPK Signaling. Int J Mol Sci 2021; 22:ijms222212595. [PMID: 34830476 PMCID: PMC8622459 DOI: 10.3390/ijms222212595] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 11/17/2021] [Accepted: 11/18/2021] [Indexed: 01/03/2023] Open
Abstract
Mitogen-activated protein kinase (MAPK) signaling pathways are highly conserved regulators of eukaryotic cell function. These enzymes regulate many biological processes, including the cell cycle, apoptosis, differentiation, protein biosynthesis, and oncogenesis; therefore, tight control of the activity of MAPK is critical. Kinases and phosphatases are well established as MAPK activators and inhibitors, respectively. Kinases phosphorylate MAPKs, initiating and controlling the amplitude of the activation. In contrast, MAPK phosphatases (MKPs) dephosphorylate MAPKs, downregulating and controlling the duration of the signal. In addition, within the past decade, pseudoenzymes of these two families, pseudokinases and pseudophosphatases, have emerged as bona fide signaling regulators. This review discusses the role of pseudophosphatases in MAPK signaling, highlighting the function of phosphoserine/threonine/tyrosine-interacting protein (STYX) and TAK1-binding protein (TAB 1) in regulating MAPKs. Finally, a new paradigm is considered for this well-studied cellular pathway, and signal transduction pathways in general.
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4
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Nitzsche A, Pietilä R, Love DT, Testini C, Ninchoji T, Smith RO, Ekvärn E, Larsson J, Roche FP, Egaña I, Jauhiainen S, Berger P, Claesson‐Welsh L, Hellström M. Paladin is a phosphoinositide phosphatase regulating endosomal VEGFR2 signalling and angiogenesis. EMBO Rep 2021; 22:e50218. [PMID: 33369848 PMCID: PMC7857541 DOI: 10.15252/embr.202050218] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 11/07/2020] [Accepted: 11/18/2020] [Indexed: 12/19/2022] Open
Abstract
Cell signalling governs cellular behaviour and is therefore subject to tight spatiotemporal regulation. Signalling output is modulated by specialized cell membranes and vesicles which contain unique combinations of lipids and proteins. The phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2 ), an important component of the plasma membrane as well as other subcellular membranes, is involved in multiple processes, including signalling. However, which enzymes control the turnover of non-plasma membrane PI(4,5)P2 , and their impact on cell signalling and function at the organismal level are unknown. Here, we identify Paladin as a vascular PI(4,5)P2 phosphatase regulating VEGFR2 endosomal signalling and angiogenesis. Paladin is localized to endosomal and Golgi compartments and interacts with vascular endothelial growth factor receptor 2 (VEGFR2) in vitro and in vivo. Loss of Paladin results in increased internalization of VEGFR2, over-activation of extracellular regulated kinase 1/2, and hypersprouting of endothelial cells in the developing retina of mice. These findings suggest that inhibition of Paladin, or other endosomal PI(4,5)P2 phosphatases, could be exploited to modulate VEGFR2 signalling and angiogenesis, when direct and full inhibition of the receptor is undesirable.
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Affiliation(s)
- Anja Nitzsche
- Science for Life LaboratoryThe Rudbeck LaboratoryDepartment of Immunology, Genetics and PathologyUppsala UniversityUppsalaSweden
- Present address:
Université de ParisParis Cardiovascular Research CenterINSERM U970ParisFrance
| | - Riikka Pietilä
- Science for Life LaboratoryThe Rudbeck LaboratoryDepartment of Immunology, Genetics and PathologyUppsala UniversityUppsalaSweden
| | - Dominic T Love
- Science for Life LaboratoryThe Rudbeck LaboratoryDepartment of Immunology, Genetics and PathologyUppsala UniversityUppsalaSweden
| | - Chiara Testini
- Science for Life LaboratoryThe Rudbeck LaboratoryDepartment of Immunology, Genetics and PathologyUppsala UniversityUppsalaSweden
- Present address:
Division of NephrologyDepartment of MedicineBoston Children’s HospitalBostonMAUSA
| | - Takeshi Ninchoji
- Science for Life LaboratoryThe Rudbeck LaboratoryDepartment of Immunology, Genetics and PathologyUppsala UniversityUppsalaSweden
| | - Ross O Smith
- Science for Life LaboratoryThe Rudbeck LaboratoryDepartment of Immunology, Genetics and PathologyUppsala UniversityUppsalaSweden
| | - Elisabet Ekvärn
- Science for Life LaboratoryThe Rudbeck LaboratoryDepartment of Immunology, Genetics and PathologyUppsala UniversityUppsalaSweden
- Present address:
Cepheid ABSolnaSweden
| | - Jimmy Larsson
- Science for Life LaboratoryThe Rudbeck LaboratoryDepartment of Immunology, Genetics and PathologyUppsala UniversityUppsalaSweden
- Present address:
Department of Cell and Molecular BiologyUppsala UniversityUppsalaSweden
| | - Francis P Roche
- Science for Life LaboratoryThe Rudbeck LaboratoryDepartment of Immunology, Genetics and PathologyUppsala UniversityUppsalaSweden
| | - Isabel Egaña
- Science for Life LaboratoryThe Rudbeck LaboratoryDepartment of Immunology, Genetics and PathologyUppsala UniversityUppsalaSweden
| | - Suvi Jauhiainen
- Science for Life LaboratoryThe Rudbeck LaboratoryDepartment of Immunology, Genetics and PathologyUppsala UniversityUppsalaSweden
| | - Philipp Berger
- Laboratory of Nanoscale BiologyPaul‐Scherrer InstituteVilligenSwitzerland
| | - Lena Claesson‐Welsh
- Science for Life LaboratoryThe Rudbeck LaboratoryDepartment of Immunology, Genetics and PathologyUppsala UniversityUppsalaSweden
| | - Mats Hellström
- Science for Life LaboratoryThe Rudbeck LaboratoryDepartment of Immunology, Genetics and PathologyUppsala UniversityUppsalaSweden
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5
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Chen MJ, Dixon JE, Manning G. Genomics and evolution of protein phosphatases. Sci Signal 2017; 10:10/474/eaag1796. [DOI: 10.1126/scisignal.aag1796] [Citation(s) in RCA: 110] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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6
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Gulerez I, Funato Y, Wu H, Yang M, Kozlov G, Miki H, Gehring K. Phosphocysteine in the PRL-CNNM pathway mediates magnesium homeostasis. EMBO Rep 2016; 17:1890-1900. [PMID: 27856537 DOI: 10.15252/embr.201643393] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Revised: 10/07/2016] [Accepted: 10/13/2016] [Indexed: 01/10/2023] Open
Abstract
PRLs (phosphatases of regenerating liver) are frequently overexpressed in human cancers and are prognostic markers of poor survival. Despite their potential as therapeutic targets, their mechanism of action is not understood in part due to their weak enzymatic activity. Previous studies revealed that PRLs interact with CNNM ion transporters and prevent CNNM4-dependent Mg2+ transport, which is important for energy metabolism and tumor progression. Here, we report that PRL-CNNM complex formation is regulated by the formation of phosphocysteine. We show that cysteine in the PRL catalytic site is endogenously phosphorylated as part of the catalytic cycle and that phosphocysteine levels change in response to Mg2+ levels. Phosphorylation blocks PRL binding to CNNM Mg2+ transporters, and mutations that block the PRL-CNNM interaction prevent regulation of Mg2+ efflux in cultured cells. The crystal structure of the complex of PRL2 and the CBS-pair domain of the Mg2+ transporter CNNM3 reveals the molecular basis for the interaction. The identification of phosphocysteine as a regulatory modification opens new perspectives for signaling by protein phosphatases.
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Affiliation(s)
- Irina Gulerez
- Department of Biochemistry and Groupe de recherche axé sur la structure des protéines, McGill University, Montreal, Quebec, Canada
| | - Yosuke Funato
- Department of Cellular Regulation, Research Institute for Microbial Diseases Osaka University, Suita, Osaka, Japan
| | - Howie Wu
- Department of Biochemistry and Groupe de recherche axé sur la structure des protéines, McGill University, Montreal, Quebec, Canada
| | - Meng Yang
- Department of Biochemistry and Groupe de recherche axé sur la structure des protéines, McGill University, Montreal, Quebec, Canada
| | - Guennadi Kozlov
- Department of Biochemistry and Groupe de recherche axé sur la structure des protéines, McGill University, Montreal, Quebec, Canada
| | - Hiroaki Miki
- Department of Cellular Regulation, Research Institute for Microbial Diseases Osaka University, Suita, Osaka, Japan
| | - Kalle Gehring
- Department of Biochemistry and Groupe de recherche axé sur la structure des protéines, McGill University, Montreal, Quebec, Canada
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7
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Abstract
Pseudophosphatases regulate signal transduction cascades, but their mechanisms of action remain enigmatic. Reflecting this mystery, the prototypical pseudophosphatase STYX (phospho-serine-threonine/tyrosine-binding protein) was named with allusion to the river of the dead in Greek mythology to emphasize that these molecules are "dead" phosphatases. Although proteins with STYX domains do not catalyze dephosphorylation, this in no way precludes their having other functions as integral elements of signaling networks. Thus, understanding their roles in signaling pathways may mark them as potential novel drug targets. This chapter outlines common strategies used to characterize the functions of pseudophosphatases, using as an example MK-STYX [mitogen-activated protein kinase (MAPK) phospho-serine-threonine/tyrosine binding], which has been linked to tumorigenesis, apoptosis, and neuronal differentiation. We start with the importance of "restoring" (when possible) phosphatase activity in a pseudophosphatase so that the active mutant may be used as a comparison control throughout immunoprecipitation and mass spectrometry analyses. To this end, we provide protocols for site-directed mutagenesis, mammalian cell transfection, co-immunoprecipitation, phosphatase activity assays, and immunoblotting that we have used to investigate MK-STYX and the active mutant MK-STYXactive. We also highlight the importance of utilizing RNA interference (RNAi) "knockdown" technology to determine a cellular phenotype in various cell lines. Therefore, we outline our protocols for introducing short hairpin RNA (shRNA) expression plasmids into mammalians cells and quantifying knockdown of gene expression with real-time quantitative PCR (qPCR). A combination of cellular, molecular, biochemical, and proteomic techniques has served as powerful tools in identifying novel functions of the pseudophosphatase MK-STYX. Likewise, the information provided here should be a helpful guide to elucidating the function of other pseudophosphatases.
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Affiliation(s)
- Shantá D Hinton
- Department of Biology, 3045 Integrated Science Center, College of William and Mary, 540 Landrum Dr., Williamsburg, VA, 23187, USA.
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8
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Radha V. Use of Dominant-Negative/Substrate Trapping PTP Mutations to Search for PTP Interactors/Substrates. Methods Mol Biol 2016; 1447:243-65. [PMID: 27514810 DOI: 10.1007/978-1-4939-3746-2_14] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Phosphorylation of proteins on tyrosine residues is the consequence of coordinated action of tyrosine kinases (TKs), and protein tyrosine phosphatases (PTPs). Together, they regulate intermolecular interactions, subcellular localization, and activity of a variety of proteins. The level of total protein-associated tyrosine phosphorylation in eukaryotic cells is only a small fraction of the total phosphorylation. PTPs, which have high specific activity compared to tyrosine kinases, play an important role in maintaining the tyrosine phosphorylation state of proteins and regulate signal transduction pathways and cellular responses. PTPs depend on specific invariant residues that enable binding to substrates phosphorylated at tyrosine and aid catalytic activity. Identification of PTP substrates has helped understand their role in distinct intracellular signaling pathways. Because of their high specific activity, the interaction between tyrosine phosphatases and their substrates is often very transient in the cellular context, and therefore identification of physiological substrates has been difficult. Single-site mutations in the enzymes stabilize interaction between the enzyme and its targets and have been used extensively to identify substrates. The mutations are either of the catalytic cysteine (Cys) residue or other invariant residues and have been classified as substrate-trapping mutants (STMs). These mutants often serve as dominant negatives that can inactivate effector functions of a specific PTP within cells. Considering their association with human disorders, inhibiting specific PTPs is important therapeutically. Since the catalytic domains are largely conserved, developing small-molecule inhibitors to a particular enzyme has proven difficult and therefore alternate strategies to block functions of individual enzymes are seriously being investigated. We provide a description of methods that will be useful to design strategies of using dominant-negative and substrate-trapping mutants for identifying novel interacting partners and substrates of PTPs.
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Affiliation(s)
- Vegesna Radha
- Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad, 500 007, India.
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9
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Alonso A, Pulido R. The extended human PTPome: a growing tyrosine phosphatase family. FEBS J 2015; 283:1404-29. [PMID: 26573778 DOI: 10.1111/febs.13600] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Revised: 10/02/2015] [Accepted: 11/13/2015] [Indexed: 12/13/2022]
Abstract
Tyr phosphatases are, by definition, enzymes that dephosphorylate phospho-Tyr (pTyr) from proteins. This activity is found in several structurally diverse protein families, including the protein Tyr phosphatase (PTP), arsenate reductase, rhodanese, haloacid dehalogenase (HAD) and His phosphatase (HP) families. Most of these families include members with substrate specificity for non-pTyr substrates, such as phospho-Ser/phospho-Thr, phosphoinositides, phosphorylated carbohydrates, mRNAs, or inorganic moieties. A Cys is essential for catalysis in PTPs, rhodanese and arsenate reductase enzymes, whereas this work is performed by an Asp in HAD phosphatases and by a His in HPs, via a catalytic mechanism shared by all of the different families. The category that contains most Tyr phosphatases is the PTP family, which, although it received its name from this activity, includes Ser, Thr, inositide, carbohydrate and RNA phosphatases, as well as some inactive pseudophosphatase proteins. Here, we propose an extended collection of human Tyr phosphatases, which we call the extended human PTPome. The addition of new members (SACs, paladin, INPP4s, TMEM55s, SSU72, and acid phosphatases) to the currently categorized PTP group of enzymes means that the extended human PTPome contains up to 125 proteins, of which ~ 40 are selective for pTyr. We set criteria to ascribe proteins to the extended PTPome, and summarize the more important features of the new PTPome members in the context of their phosphatase activity and their relationship with human disease.
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Affiliation(s)
- Andrés Alonso
- Instituto de Biología y Genética Molecular (IBGM), CSIC-Universidad de Valladolid, Valladolid, Spain
| | - Rafael Pulido
- Biocruces Health Research Institute, Barakaldo, Spain.,IKERBASQUE, Basque Foundation for Science, Bilbao, Spain
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10
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Reiterer V, Eyers PA, Farhan H. Day of the dead: pseudokinases and pseudophosphatases in physiology and disease. Trends Cell Biol 2014; 24:489-505. [PMID: 24818526 DOI: 10.1016/j.tcb.2014.03.008] [Citation(s) in RCA: 121] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Revised: 03/25/2014] [Accepted: 03/27/2014] [Indexed: 12/19/2022]
Abstract
Pseudophosphatases and pseudokinases are increasingly viewed as integral elements of signaling pathways, and there is mounting evidence that they have frequently retained the ability to interact with cellular 'substrates', and can exert important roles in different diseases. However, these pseudoenzymes have traditionally received scant attention compared to classical kinases and phosphatases. In this review we explore new findings in the emerging pseudokinase and pseudophosphatase fields, and discuss their different modes of action which include exciting new roles as scaffolds, anchors, spatial modulators, traps, and ligand-driven regulators of canonical kinases and phosphatases. Thus, it is now apparent that pseudokinases and pseudophosphatases both support and drive a panoply of signaling networks. Finally, we highlight recent evidence on their involvement in human pathologies, marking them as potential novel drug targets.
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Affiliation(s)
- Veronika Reiterer
- Biotechnology Institute Thurgau at the University of Konstanz, Kreuzlingen, Switzerland
| | - Patrick A Eyers
- Department of Biochemistry, Institute of Integrative Biology, University of Liverpool, Liverpool, UK.
| | - Hesso Farhan
- Biotechnology Institute Thurgau at the University of Konstanz, Kreuzlingen, Switzerland; Department of Biology, University of Konstanz, Konstanz, Germany.
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