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Jiang Y, Wu B, Zhang X, Yang L, Wang S, Li H, Zhou S, Qian Y, Wang H. Thirteen New Patients of PPP2R5D Gene Mutation and the Fine Profile of Genotype-Phenotype Correlation Unraveling the Pathogenic Mechanism Underlying Macrocephaly Phenotype. CHILDREN (BASEL, SWITZERLAND) 2024; 11:897. [PMID: 39201832 PMCID: PMC11352527 DOI: 10.3390/children11080897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/17/2024] [Revised: 07/21/2024] [Accepted: 07/22/2024] [Indexed: 09/03/2024]
Abstract
BACKGROUND Neurodevelopmental disorders (NDDs) are a group of diseases that severely affect the physical and mental health of children. The PPP2R5D gene encodes B56δ, the regulatory subunit of protein phosphatase 2A (PP2A). NDDs related to the PPP2R5D gene have recently been defined as Houge-Janssens syndrome 1. METHODS Clinical/whole exome sequencing was performed on approximately 3000 patients with NDDs from 2017 to 2023. In vitro experiments were performed to assess the impairment of variants to protein expression and the assembly of PP2A holoenzyme. The genetic information and phenotypes of the reported patients, as well as patients in this study, were summarized, and the genotype-phenotype relationship was analyzed. The probability of pathogenic missense variants in PPP2R5D was predicted using AlphaMissense (AM), and the relationship between certain phenotype and 3D protein structural features were analyzed. RESULTS Thirteen new patients carrying twelve PPP2R5D gene variants were detected, including five novel missense variants and one novel frameshift variant. In vitro experiments revealed that the frameshift variant p.H463Mfs*3 resulted in a ~50 kDa truncated protein with lower expression level. Except for E420K and T536R, other missense variants impaired holoenzyme assembly. Furthermore, we found that pathogenic/likely pathogenic (P/LP) variants that have been reported so far were all missense variants and clustered in three conserved regions, and the likelihood of P/LP mutations located in these conserved regions was extremely high. In addition, the macrocephaly phenotype was related to negatively charged residues involved in substrate recruitment. CONCLUSIONS We reported thirteen new patients with PPP2R5D gene variants and expanded the PPP2R5D variant spectrum. We confirmed the pathogenicity of novel variants through in vitro experiments. Our findings in genotype-phenotype relationship provide inspiration for genetic counseling and interpretation of variants. We also provide directions for further research on the mechanism of macrocephaly phenotype.
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Affiliation(s)
- Yinmo Jiang
- Center for Molecular Medicine, Pediatrics Research Institute, Children’s Hospital of Fudan University, National Children’s Medical Center, 399 Wanyuan Road, Shanghai 201102, China; (Y.J.); (X.Z.)
| | - Bingbing Wu
- Center for Molecular Medicine, Pediatrics Research Institute, Children’s Hospital of Fudan University, National Children’s Medical Center, 399 Wanyuan Road, Shanghai 201102, China; (Y.J.); (X.Z.)
| | - Xi Zhang
- Center for Molecular Medicine, Pediatrics Research Institute, Children’s Hospital of Fudan University, National Children’s Medical Center, 399 Wanyuan Road, Shanghai 201102, China; (Y.J.); (X.Z.)
| | - Lin Yang
- Center for Molecular Medicine, Pediatrics Research Institute, Children’s Hospital of Fudan University, National Children’s Medical Center, 399 Wanyuan Road, Shanghai 201102, China; (Y.J.); (X.Z.)
| | - Sujuan Wang
- Department of Rehabilitation, Children’s Hospital of Fudan University, Shanghai 201102, China
| | - Huiping Li
- Department of Child Health Care, Children’s Hospital of Fudan University, National Children’s Medical Center, 399 Wanyuan Road, Shanghai 201102, China
| | - Shuizhen Zhou
- Neurology Department, Children’s Hospital of Fudan University, National Children’s Medical Center, 399 Wanyuan Road, Shanghai 201102, China
| | - Yanyan Qian
- Center for Molecular Medicine, Pediatrics Research Institute, Children’s Hospital of Fudan University, National Children’s Medical Center, 399 Wanyuan Road, Shanghai 201102, China; (Y.J.); (X.Z.)
| | - Huijun Wang
- Center for Molecular Medicine, Pediatrics Research Institute, Children’s Hospital of Fudan University, National Children’s Medical Center, 399 Wanyuan Road, Shanghai 201102, China; (Y.J.); (X.Z.)
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Qi Y, Li L, Wei Y, Ma F. PP2A as a potential therapeutic target for breast cancer: Current insights and future perspectives. Biomed Pharmacother 2024; 173:116398. [PMID: 38458011 DOI: 10.1016/j.biopha.2024.116398] [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: 12/16/2023] [Revised: 02/28/2024] [Accepted: 03/06/2024] [Indexed: 03/10/2024] Open
Abstract
Breast cancer has become the most prevalent malignancy worldwide; however, therapeutic efficacy is far from satisfactory. To alleviate the burden of this disease, it is imperative to discover novel mechanisms and treatment strategies. Protein phosphatase 2 A (PP2A) comprises a family of mammalian serine/threonine phosphatases that regulate many cellular processes. PP2A is dysregulated in several human diseases, including oncological pathologies, and plays a pivotal role in the initiation and progression of tumours. The role of PP2A as a tumour suppressor has been extensively studied, and its regulation can serve as a target for anticancer therapy. Recent studies have shown that PP2A is a tumour promotor. PP2A-mediated anticancer therapy may involve two opposing mechanisms: activation and inhibition. In general, the contradictory roles of PP2A should not be overlooked, and more work is needed to determine the molecular mechanism by which PP2A affects in tumours. In this review, the literature on the role of PP2A in tumours, especially in breast cancer, was analysed. This review describes relevant targets of breast cancer, such as cell cycle control, DNA damage responses, epidermal growth factor receptor, immune modulation and cell death resistance, which may lead to effective therapeutic strategies or influence drug development in breast cancer.
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Affiliation(s)
- Yalong Qi
- Department of Medical Oncology, National Cancer Center, National Clinical Research Center for Cancer, Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Chaoyang District, Pan jia yuan nan Road 17, Beijing 100021, China
| | - Lixi Li
- Department of Medical Oncology, National Cancer Center, National Clinical Research Center for Cancer, Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Chaoyang District, Pan jia yuan nan Road 17, Beijing 100021, China
| | - Yuhan Wei
- Department of Medical Oncology, National Cancer Center, National Clinical Research Center for Cancer, Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Chaoyang District, Pan jia yuan nan Road 17, Beijing 100021, China
| | - Fei Ma
- Department of Medical Oncology, National Cancer Center, National Clinical Research Center for Cancer, Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Chaoyang District, Pan jia yuan nan Road 17, Beijing 100021, China.
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3
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Herting JR, König JH, Hadova K, Heinick A, Müller FU, Pauls P, Seidl MD, Soppa C, Kirchhefer U. Hypercontractile cardiac phenotype in mice overexpressing the regulatory subunit PR72 of protein phosphatase 2A. Front Cardiovasc Med 2023; 10:1239555. [PMID: 37868783 PMCID: PMC10590119 DOI: 10.3389/fcvm.2023.1239555] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Accepted: 09/22/2023] [Indexed: 10/24/2023] Open
Abstract
Background The activity, localization, and substrate specificity of the protein phosphatase 2A (PP2A) heterotrimer are controlled by various regulatory B subunits. PR72 belongs to the B'' gene family and has been shown to be upregulated in human heart failure. However, little is known about the functions of PR72 in the myocardium. Methods To address this issue, we generated a transgenic mouse model with heart-specific overexpression of PP2A-PR72. Biochemical and physiological methods were used to determine contractility, Ca2+ cycling parameters, and protein phosphorylation. Results A 2.5-fold increase in PR72 expression resulted in moderate cardiac hypertrophy. Maximal ventricular pressure was increased in catheterized transgenic mice (TG) compared to wild-type (WT) littermates. This was accompanied by an increased shortening of sarcomere length and faster relaxation at the single-cell level in TG. In parallel with these findings, the peak amplitude of Ca2+ transients was increased, and the decay in intracellular Ca2+ levels was shortened in TG compared to WT. The changes in Ca2+ cycling in TG were also evident from an increase in the full duration and width at half maximum of Ca2+ sparks. Consistent with the contractile data, phosphorylation of phospholamban at threonine-17 was higher in TG hearts. The lower expression of the Na+/Ca2+ exchanger may also contribute to the hypercontractile state in transgenic myocardium. Conclusion Our results suggest that PP2A-PR72 plays an important role in regulating cardiac contractile function and Ca2+ cycling, indicating that the upregulation of PR72 in heart failure is an attempt to compensate functionally.
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Affiliation(s)
- Julius R. Herting
- Institut für Pharmakologie und Toxikologie, Universitätsklinikum Münster, Universität Münster, Münster, Germany
| | - Jule H. König
- Institut für Pharmakologie und Toxikologie, Universitätsklinikum Münster, Universität Münster, Münster, Germany
| | - Katarina Hadova
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Comenius University in Bratislava, Bratislava, Slovakia
| | - Alexander Heinick
- Institut für Pharmakologie und Toxikologie, Universitätsklinikum Münster, Universität Münster, Münster, Germany
| | - Frank U. Müller
- Institut für Pharmakologie und Toxikologie, Universitätsklinikum Münster, Universität Münster, Münster, Germany
| | - Paul Pauls
- Institut für Pharmakologie und Toxikologie, Universitätsklinikum Münster, Universität Münster, Münster, Germany
| | - Matthias D. Seidl
- Institut für Pharmakologie und Toxikologie, Universitätsklinikum Münster, Universität Münster, Münster, Germany
| | - Carolina Soppa
- Institut für Pharmakologie und Toxikologie, Universitätsklinikum Münster, Universität Münster, Münster, Germany
| | - Uwe Kirchhefer
- Institut für Pharmakologie und Toxikologie, Universitätsklinikum Münster, Universität Münster, Münster, Germany
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Lacroix B, Lorca T, Castro A. Structural, enzymatic and spatiotemporal regulation of PP2A-B55 phosphatase in the control of mitosis. Front Cell Dev Biol 2022; 10:967909. [PMID: 36105360 PMCID: PMC9465306 DOI: 10.3389/fcell.2022.967909] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Accepted: 08/04/2022] [Indexed: 11/18/2022] Open
Abstract
Cells require major physical changes to induce a proper repartition of the DNA. Nuclear envelope breakdown, DNA condensation and spindle formation are promoted at mitotic entry by massive protein phosphorylation and reversed at mitotic exit by the timely and ordered dephosphorylation of mitotic substrates. This phosphorylation results from the balance between the activity of kinases and phosphatases. The role of kinases in the control of mitosis has been largely studied, however, the impact of phosphatases has long been underestimated. Recent data have now established that the regulation of phosphatases is crucial to confer timely and ordered cellular events required for cell division. One major phosphatase involved in this process is the phosphatase holoenzyme PP2A-B55. This review will be focused in the latest structural, biochemical and enzymatic insights provided for PP2A-B55 phosphatase as well as its regulators and mechanisms of action.
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Affiliation(s)
- Benjamin Lacroix
- Centre de Recherche en Biologie Cellulaire de Montpellier (CRBM), CNRS UMR5237, Université de Montpellier, CNRS UMR5237Montpellier, France
- Équipe Labellisée “Ligue Nationale Contre le Cancer”, Paris, France
| | - Thierry Lorca
- Centre de Recherche en Biologie Cellulaire de Montpellier (CRBM), CNRS UMR5237, Université de Montpellier, CNRS UMR5237Montpellier, France
- Équipe Labellisée “Ligue Nationale Contre le Cancer”, Paris, France
| | - Anna Castro
- Centre de Recherche en Biologie Cellulaire de Montpellier (CRBM), CNRS UMR5237, Université de Montpellier, CNRS UMR5237Montpellier, France
- Équipe Labellisée “Ligue Nationale Contre le Cancer”, Paris, France
- *Correspondence: Anna Castro,
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5
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Glaser D, Heinick A, Herting JR, Massing F, Müller FU, Pauls P, Rozhdestvensky TS, Schulte JS, Seidl MD, Skryabin BV, Stümpel F, Kirchhefer U. Impaired myocellular Ca 2+ cycling in protein phosphatase PP2A-B56α knockout mice is normalized by β-adrenergic stimulation. J Biol Chem 2022; 298:102362. [PMID: 35963431 PMCID: PMC9478386 DOI: 10.1016/j.jbc.2022.102362] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 07/25/2022] [Accepted: 07/26/2022] [Indexed: 11/24/2022] Open
Abstract
The activity of protein phosphatase 2A (PP2A) is determined by the expression and localization of the regulatory B-subunits. PP2A-B56α is the dominant isoform of the B′-family in the heart. Its role in regulating the cardiac response to β-adrenergic stimulation is not yet fully understood. We therefore generated mice deficient in B56α to test the functional cardiac effects in response to catecholamine administration versus corresponding WT mice. We found the decrease in basal PP2A activity in hearts of KO mice was accompanied by a counter-regulatory increase in the expression of B′ subunits (β and γ) and higher phosphorylation of sarcoplasmic reticulum Ca2+ regulatory and myofilament proteins. The higher phosphorylation levels were associated with enhanced intraventricular pressure and relaxation in catheterized KO mice. In contrast, at the cellular level, we detected depressed Ca2+ transient and sarcomere shortening parameters in KO mice at basal conditions. Consistently, the peak amplitude of the L-type Ca2+ current was reduced and the inactivation kinetics of ICaL were prolonged in KO cardiomyocytes. However, we show β-adrenergic stimulation resulted in a comparable peak amplitude of Ca2+ transients and myocellular contraction between KO and WT cardiomyocytes. Therefore, we propose higher isoprenaline-induced Ca2+ spark frequencies might facilitate the normalized Ca2+ signaling in KO cardiomyocytes. In addition, the application of isoprenaline was associated with unchanged L-type Ca2+ current parameters between both groups. Our data suggest an important influence of PP2A-B56α on the regulation of Ca2+ signaling and contractility in response to β-adrenergic stimulation in the myocardium.
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Affiliation(s)
- Dennis Glaser
- Institute of Pharmacology and Toxicology, University of Münster, Münster, Germany
| | - Alexander Heinick
- Institute of Pharmacology and Toxicology, University of Münster, Münster, Germany
| | - Julius R Herting
- Institute of Pharmacology and Toxicology, University of Münster, Münster, Germany
| | - Fabian Massing
- Institute of Pharmacology and Toxicology, University of Münster, Münster, Germany
| | - Frank U Müller
- Institute of Pharmacology and Toxicology, University of Münster, Münster, Germany
| | - Paul Pauls
- Institute of Pharmacology and Toxicology, University of Münster, Münster, Germany
| | - Timofey S Rozhdestvensky
- Department of Medicine, Core Facility Transgenic Animal and Genetic Engineering Models (TRAM), University of Münster, Münster, Germany
| | - Jan S Schulte
- Institute of Pharmacology and Toxicology, University of Münster, Münster, Germany
| | - Matthias D Seidl
- Institute of Pharmacology and Toxicology, University of Münster, Münster, Germany
| | - Boris V Skryabin
- Department of Medicine, Core Facility Transgenic Animal and Genetic Engineering Models (TRAM), University of Münster, Münster, Germany
| | - Frank Stümpel
- Institute of Pharmacology and Toxicology, University of Münster, Münster, Germany
| | - Uwe Kirchhefer
- Institute of Pharmacology and Toxicology, University of Münster, Münster, Germany.
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6
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Dyson JJ, Abbasi F, Varadkar P, McCright B. Growth arrest of PPP2R5C and PPP2R5D double knockout mice indicates a genetic interaction and conserved function for these PP2A B subunits. FASEB Bioadv 2022; 4:273-282. [PMID: 35415460 PMCID: PMC8984082 DOI: 10.1096/fba.2021-00130] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 12/01/2021] [Accepted: 12/07/2021] [Indexed: 12/03/2022] Open
Abstract
Protein phosphatase 2A (PP2A) is a heterotrimeric phosphatase that controls a wide range of cellular functions. The catalytic activity and intracellular location of PP2A are modulated by its association with regulatory B subunits, including B56 proteins, which are encoded by five separate genes in humans and mice. The specific effects of each B56 protein on PP2A activity and function are largely unknown. As part of an effort to identify specific PP2A-B56 functions, we created knockout strains of B56β, B56δ, and B56ε using CRISPR/Cas9n. We found that none of the individual B56 genes are essential for mouse survival. However, mice that have both B56δ and B56γ inactivated (B56δγ-), arrest fetal development around Day E12. The hearts of B56δγ- mice have a single outflow vessel rather than having both an aorta and a pulmonary artery. Thus, there appears to be strong genetic interaction between B56δ and B56γ, and together they are necessary for heart development. Of note, both these proteins have been shown to localize to the nucleus and have the most related peptide sequences of the B56 family members. Our results suggest there are B56 subfamilies, which work in conjunction to regulate specific PP2A functions.
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Affiliation(s)
- Jade J. Dyson
- FDACenter for Biologics Evaluation and ResearchSilver SpringMarylandUSA
| | - Fatima Abbasi
- FDACenter for Biologics Evaluation and ResearchSilver SpringMarylandUSA
| | - Prajakta Varadkar
- FDACenter for Biologics Evaluation and ResearchSilver SpringMarylandUSA
| | - Brent McCright
- FDACenter for Biologics Evaluation and ResearchSilver SpringMarylandUSA
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Hein J, Cyert MS, Fordyce PM. MRBLE-pep Measurements Reveal Accurate Binding Affinities for B56, a PP2A Regulatory Subunit. ACS MEASUREMENT SCIENCE AU 2021; 1:56-64. [PMID: 35128539 PMCID: PMC8809670 DOI: 10.1021/acsmeasuresciau.1c00008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Signal transduction pathways rely on dynamic interactions between protein globular domains and short linear motifs (SLiMs). The weak affinities of these interactions are essential to allow fast rewiring of signaling pathways and downstream responses but also pose technical challenges for interaction detection and measurement. We recently developed a technique (MRBLE-pep) that leverages spectrally encoded hydrogel beads to measure binding affinities between a single protein of interest and 48 different peptide sequences in a single small volume. In prior work, we applied it to map the binding specificity landscape between calcineurin and the PxIxIT SLiM (Nguyen, H. Q. et al. Elife 2019, 8). Here, using peptide sequences known to bind the PP2A regulatory subunit B56α, we systematically compare affinities measured by MRBLE-pep or isothermal calorimetry (ITC) and confirm that MRBLE-pep accurately quantifies relative affinity over a wide dynamic range while using a fraction of the material required for traditional methods such as ITC.
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Affiliation(s)
- Jamin
B. Hein
- Department
of Biology, Stanford University, Stanford, California 94305, United States
- Department
of Bioengineering, Stanford University, Stanford, California 94305, United States
- The
Novo Nordisk Foundation Center for Protein Research, Faculty of Health
and Medical Sciences, University of Copenhagen, Blegdamsvej 3b, 2200 Copenhagen, Denmark
| | - Martha S. Cyert
- Department
of Biology, Stanford University, Stanford, California 94305, United States
| | - Polly M. Fordyce
- Department
of Bioengineering, Stanford University, Stanford, California 94305, United States
- Department
of Genetics, Stanford University, Stanford, California 94305, United States
- ChEM-H
Institute, Stanford University, Stanford, California 94305, United States
- Chan
Zuckerberg
Biohub, San Francisco, California 94110, United States
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8
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Song J, Merrill RA, Usachev AY, Strack S. The X-linked intellectual disability gene product and E3 ubiquitin ligase KLHL15 degrades doublecortin proteins to constrain neuronal dendritogenesis. J Biol Chem 2020; 296:100082. [PMID: 33199366 PMCID: PMC7948412 DOI: 10.1074/jbc.ra120.016210] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Revised: 10/27/2020] [Accepted: 11/16/2020] [Indexed: 11/13/2022] Open
Abstract
Proper brain development and function requires finely controlled mechanisms for protein turnover, and disruption of genes involved in proteostasis is a common cause of neurodevelopmental disorders. Kelch-like 15 (KLHL15) is a substrate adaptor for cullin3-containing E3 ubiquitin ligases, and KLHL15 gene mutations were recently described as a cause of severe X-linked intellectual disability. Here, we used a bioinformatics approach to identify a family of neuronal microtubule-associated proteins as KLHL15 substrates, which are themselves critical for early brain development. We biochemically validated doublecortin (DCX), also an X-linked disease protein, and doublecortin-like kinase 1 and 2 as bona fide KLHL15 interactors and mapped KLHL15 interaction regions to their tandem DCX domains. Shared with two previously identified KLHL15 substrates, a FRY tripeptide at the C-terminal edge of the second DCX domain is necessary for KLHL15-mediated ubiquitination of DCX and doublecortin-like kinase 1 and 2 and subsequent proteasomal degradation. Conversely, silencing endogenous KLHL15 markedly stabilizes these DCX domain-containing proteins and prolongs their half-life. Functionally, overexpression of KLHL15 in the presence of WT DCX reduces dendritic complexity of cultured hippocampal neurons, whereas neurons expressing FRY-mutant DCX are resistant to KLHL15. Collectively, our findings highlight the critical importance of the E3 ubiquitin ligase adaptor KLHL15 in proteostasis of neuronal microtubule-associated proteins and identify a regulatory network important for development of the mammalian nervous system.
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Affiliation(s)
- Jianing Song
- Department of Neuroscience and Pharmacology and the Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa, USA
| | - Ronald A Merrill
- Department of Neuroscience and Pharmacology and the Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa, USA
| | - Andrew Y Usachev
- Department of Neuroscience and Pharmacology and the Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa, USA
| | - Stefan Strack
- Department of Neuroscience and Pharmacology and the Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa, USA.
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Peroxynitrite promotes serine-62 phosphorylation-dependent stabilization of the oncoprotein c-Myc. Redox Biol 2020; 34:101587. [PMID: 32512497 PMCID: PMC7280771 DOI: 10.1016/j.redox.2020.101587] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 04/22/2020] [Accepted: 05/14/2020] [Indexed: 12/13/2022] Open
Abstract
Stabilization of c-Myc oncoprotein is dependent on post-translational modifications, especially its phosphorylation at serine-62 (S62), which enhances its tumorigenic potential. Herein we report that increase in intracellular superoxide induces phospho-stabilization and activation of c-Myc in cancer cells. Importantly, sustained phospho-S62 c-Myc was necessary for promoting superoxide dependent chemoresistance as non-phosphorylatable S62A c-Myc was insensitive to the redox impact when subjected to chemotherapeutic insults. This redox-dependent sustained S62 phosphorylation occurs through nitrative inhibition of phosphatase, PP2A, brought about by peroxynitrite, a reaction product of superoxide and nitric oxide. We identified a conserved tyrosine residue (Y238) in the c-Myc targeting subunit B56α of PP2A, which is selectively amenable to nitrative inhibition, further preventing holoenzyme assembly. In summary, we have established a novel mechanism wherein the pro-oxidant microenvironment stimulates a pro-survival milieu and reinforces tumor maintenance as a functional consequence of c-Myc activation through its sustained S62 phosphorylation via inhibition of phosphatase PP2A. Significance statement Increased peroxynitrite signaling in tumors causes sustained S62 c-Myc phosphorylation by PP2A inhibition. This is critical to promoting c-Myc stabilization and activation which promotes chemoresistance and provides significant proliferative and growth advantages to osteosarcomas.
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10
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Puhl SL, Weeks KL, Güran A, Ranieri A, Boknik P, Kirchhefer U, Müller FU, Avkiran M. Role of type 2A phosphatase regulatory subunit B56α in regulating cardiac responses to β-adrenergic stimulation in vivo. Cardiovasc Res 2020; 115:519-529. [PMID: 30203051 PMCID: PMC6383118 DOI: 10.1093/cvr/cvy230] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Revised: 07/26/2018] [Accepted: 09/07/2018] [Indexed: 12/11/2022] Open
Abstract
AIMS B56α is a protein phosphatase 2A (PP2A) regulatory subunit that is highly expressed in the heart. We previously reported that cardiomyocyte B56α localizes to myofilaments under resting conditions and translocates to the cytosol in response to acute β-adrenergic receptor (β-AR) stimulation. Given the importance of reversible protein phosphorylation in modulating cardiac function during sympathetic stimulation, we hypothesized that loss of B56α in mice with targeted disruption of the gene encoding B56α (Ppp2r5a) would impact on cardiac responses to β-AR stimulation in vivo. METHODS AND RESULTS Cardiac phenotype of mice heterozygous (HET) or homozygous (HOM) for the disrupted Ppp2r5a allele and wild type (WT) littermates was characterized under basal conditions and following acute β-AR stimulation with dobutamine (DOB; 0.75 mg/kg i.p.) or sustained β-AR stimulation by 2-week infusion of isoproterenol (ISO; 30 mg/kg/day s.c.). Left ventricular (LV) wall thicknesses, chamber dimensions and function were assessed by echocardiography, and heart tissue collected for gravimetric, histological, and biochemical analyses. Western blot analysis revealed partial and complete loss of B56α protein in hearts from HET and HOM mice, respectively, and no changes in the expression of other PP2A regulatory, catalytic or scaffolding subunits. PP2A catalytic activity was reduced in hearts of both HET and HOM mice. There were no differences in the basal cardiac phenotype between genotypes. Acute DOB stimulation induced the expected inotropic response in WT and HET mice, which was attenuated in HOM mice. In contrast, DOB-induced increases in heart rate were unaffected by B56α deficiency. In WT mice, ISO infusion increased LV wall thicknesses, cardiomyocyte area and ventricular mass, without LV dilation, systolic dysfunction, collagen deposition or foetal gene expression. The hypertrophic response to ISO was blunted in mice deficient for B56α. CONCLUSION These findings identify B56α as a potential regulator of cardiac structure and function during β-AR stimulation.
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Affiliation(s)
- Sarah-Lena Puhl
- School of Cardiovascular Medicine and Sciences, King's College London British Heart Foundation Centre of Research Excellence, St Thomas' Hospital, Westminster Bridge Road, London, UK.,Institute for Cardiovascular Prevention, Ludwig-Maximilians-University, Pettenkoferstrasse 9b, D-80336 Munich, Germany
| | - Kate L Weeks
- School of Cardiovascular Medicine and Sciences, King's College London British Heart Foundation Centre of Research Excellence, St Thomas' Hospital, Westminster Bridge Road, London, UK.,Baker Heart and Diabetes Institute, 75 Commercial Road, Melbourne, VIC, Australia
| | - Alican Güran
- School of Cardiovascular Medicine and Sciences, King's College London British Heart Foundation Centre of Research Excellence, St Thomas' Hospital, Westminster Bridge Road, London, UK
| | - Antonella Ranieri
- School of Cardiovascular Medicine and Sciences, King's College London British Heart Foundation Centre of Research Excellence, St Thomas' Hospital, Westminster Bridge Road, London, UK
| | - Peter Boknik
- Institut für Pharmakologie und Toxikologie, Universitätsklinikum Münster, Domagkstrasse 12, D-48149 Münster, Germany
| | - Uwe Kirchhefer
- Institut für Pharmakologie und Toxikologie, Universitätsklinikum Münster, Domagkstrasse 12, D-48149 Münster, Germany
| | - Frank U Müller
- Institut für Pharmakologie und Toxikologie, Universitätsklinikum Münster, Domagkstrasse 12, D-48149 Münster, Germany
| | - Metin Avkiran
- School of Cardiovascular Medicine and Sciences, King's College London British Heart Foundation Centre of Research Excellence, St Thomas' Hospital, Westminster Bridge Road, London, UK
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11
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Lear TB, Lockwood KC, Larsen M, Tuncer F, Kennerdell JR, Morse C, Valenzi E, Tabib T, Jurczak MJ, Kass DJ, Evankovich JW, Finkel T, Lafyatis R, Liu Y, Chen BB. Kelch-like protein 42 is a profibrotic ubiquitin E3 ligase involved in systemic sclerosis. J Biol Chem 2020; 295:4171-4180. [PMID: 32071084 PMCID: PMC7105301 DOI: 10.1074/jbc.ac119.012066] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 02/07/2020] [Indexed: 01/08/2023] Open
Abstract
Systemic scleroderma (SSc) is an autoimmune disease that affects over 2.5 million people globally. SSc results in dysfunctional connective tissues with excessive profibrotic signaling, affecting skin, cardiovascular, and particularly lung tissue. Over three-quarters of individuals with SSc develop pulmonary fibrosis within 5 years, the main cause of SSc mortality. No approved medicines to manage lung SSc currently exist. Recent research suggests that profibrotic signaling by transforming growth factor β (TGF-β) is directly tied to SSc. Previous studies have also shown that ubiquitin E3 ligases potently control TGF-β signaling through targeted degradation of key regulatory proteins; however, the roles of these ligases in SSc-TGF-β signaling remain unclear. Here we utilized primary SSc patient lung cells for high-throughput screening of TGF-β signaling via high-content imaging of nuclear translocation of the profibrotic transcription factor SMAD family member 2/3 (SMAD2/3). We screened an RNAi library targeting ubiquitin E3 ligases and observed that knockdown of the E3 ligase Kelch-like protein 42 (KLHL42) impairs TGF-β-dependent profibrotic signaling. KLHL42 knockdown reduced fibrotic tissue production and decreased TGF-β-mediated SMAD activation. Using unbiased ubiquitin proteomics, we identified phosphatase 2 regulatory subunit B'ϵ (PPP2R5ϵ) as a KLHL42 substrate. Mechanistic experiments validated ubiquitin-mediated control of PPP2R5ϵ stability through KLHL42. PPP2R5ϵ knockdown exacerbated TGF-β-mediated profibrotic signaling, indicating a role of PPP2R5ϵ in SSc. Our findings indicate that the KLHL42-PPP2R5ϵ axis controls profibrotic signaling in SSc lung fibroblasts. We propose that future studies could investigate whether chemical inhibition of KLHL42 may ameliorate profibrotic signaling in SSc.
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Affiliation(s)
- Travis B Lear
- Department of Environmental and Occupational Health, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania 15261; Aging Institute, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15213
| | - Karina C Lockwood
- Aging Institute, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15213
| | - Mads Larsen
- Aging Institute, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15213
| | - Ferhan Tuncer
- Aging Institute, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15213
| | - Jason R Kennerdell
- Aging Institute, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15213
| | - Christina Morse
- Division of Rheumatology and Clinical Immunology, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15213
| | - Eleanor Valenzi
- Division of Rheumatology and Clinical Immunology, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15213
| | - Tracy Tabib
- Division of Rheumatology and Clinical Immunology, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15213
| | - Michael J Jurczak
- Division of Endocrinology and Metabolism, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15213
| | - Daniel J Kass
- Dorothy P. and Richard P. Simmons Center for Interstitial Lung Disease, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15213
| | - John W Evankovich
- Aging Institute, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15213; Acute Lung Injury Center of Excellence, Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15213
| | - Toren Finkel
- Aging Institute, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15213; Division of Cardiology, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15213
| | - Robert Lafyatis
- Division of Rheumatology and Clinical Immunology, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15213
| | - Yuan Liu
- Aging Institute, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15213; Acute Lung Injury Center of Excellence, Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15213.
| | - Bill B Chen
- Aging Institute, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15213; Acute Lung Injury Center of Excellence, Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15213; Vascular Medicine Institute, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15213.
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12
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Elgenaidi IS, Spiers JP. Regulation of the phosphoprotein phosphatase 2A system and its modulation during oxidative stress: A potential therapeutic target? Pharmacol Ther 2019; 198:68-89. [PMID: 30797822 DOI: 10.1016/j.pharmthera.2019.02.011] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Accepted: 02/15/2019] [Indexed: 02/06/2023]
Abstract
Phosphoprotein phosphatases are of growing interest in the pathophysiology of many diseases and are often the neglected partner of protein kinases. One family member, PP2A, accounts for dephosphorylation of ~55-70% of all serine/threonine phosphosites. Interestingly, dysregulation of kinase signalling is a hallmark of many diseases in which an increase in oxidative stress is also noted. With this in mind, we assess the evidence to support oxidative stress-mediated regulation of the PP2A system In this article, we first present an overview of the PP2A system before providing an analysis of the regulation of PP2A by endogenous inhibitors, post translational modification, and miRNA. Next, a detailed critique of data implicating reactive oxygen species, ischaemia, ischaemia-reperfusion, and hypoxia in regulating the PP2A holoenzyme and associated regulators is presented. Finally, the pharmacological targeting of PP2A, its endogenous inhibitors, and enzymes responsible for its post-translational modification are covered. There is extensive evidence that oxidative stress modulates multiple components of the PP2A system, however, most of the data pertains to the catalytic subunit of PP2A. Irrespective of the underlying aetiology, free radical-mediated attenuation of PP2A activity is an emerging theme. However, in many instances, a dichotomy exists, which requires clarification and mechanistic insight. Nevertheless, this raises the possibility that pharmacological activation of PP2A, either through small molecule activators of PP2A or CIP2A/SET antagonists may be beneficial in modulating the cellular response to oxidative stress. A better understanding of which, will have wide ranging implications for cancer, heart disease and inflammatory conditions.
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Affiliation(s)
- I S Elgenaidi
- Department of Pharmacology and Therapeutics, Trinity College Dublin, Ireland
| | - J P Spiers
- Department of Pharmacology and Therapeutics, Trinity College Dublin, Ireland.
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13
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Zhao H, Li D, Zhang B, Qi Y, Diao Y, Zhen Y, Shu X. PP2A as the Main Node of Therapeutic Strategies and Resistance Reversal in Triple-Negative Breast Cancer. Molecules 2017; 22:molecules22122277. [PMID: 29261144 PMCID: PMC6149800 DOI: 10.3390/molecules22122277] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Revised: 12/07/2017] [Accepted: 12/19/2017] [Indexed: 12/31/2022] Open
Abstract
Triple negative breast cancer (TNBC), is defined as a type of tumor lacking the expression of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2). The ER, PR and HER2 are usually the molecular therapeutic targets for breast cancers, but they are ineffective for TNBC because of their negative expressions, so chemotherapy is currently the main treatment strategy in TNBC. However, drug resistance remains a major impediment to TNBC chemotherapeutic treatment. Recently, the protein phosphatase 2A (PP2A) has been found to regulate the phosphorylation of some substrates involved in the relevant target of TNBC, such as cell cycle control, DNA damage responses, epidermal growth factor receptor, immune modulation and cell death resistance, which may be the effective therapeutic strategies or influence drug sensitivity to TNBCs. Furthermore, PP2A has also been found that could induce ER re-expression in ER-negative breast cancer cells, and which suggests PP2A could promote the sensitivity of tamoxifen to TNBCs as a resistance reversal agent. In this review, we will summarize the potential therapeutic value of PP2A as the main node in developing targeting agents, disrupting resistance or restoring drug sensitivity in TNBC.
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Affiliation(s)
- Henan Zhao
- Department of Pathophysiology, Dalian Medical University, Dalian 116044, China.
| | - Duojiao Li
- Kamp Pharmaceutical Co. Ltd., Changsha 410008, China.
| | - Baojing Zhang
- College of Pharmacy, Dalian Medical University, Dalian 116044, China.
| | - Yan Qi
- College of Pharmacy, Dalian Medical University, Dalian 116044, China.
| | - Yunpeng Diao
- College of Pharmacy, Dalian Medical University, Dalian 116044, China.
| | - Yuhong Zhen
- College of Pharmacy, Dalian Medical University, Dalian 116044, China.
| | - Xiaohong Shu
- College of Pharmacy, Dalian Medical University, Dalian 116044, China.
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14
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Heim A, Rymarczyk B, Mayer TU. Regulation of Cell Division. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 953:83-116. [PMID: 27975271 DOI: 10.1007/978-3-319-46095-6_3] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The challenging task of mitotic cell divisions is to generate two genetically identical daughter cells from a single precursor cell. To accomplish this task, a complex regulatory network evolved, which ensures that all events critical for the duplication of cellular contents and their subsequent segregation occur in the correct order, at specific intervals and with the highest possible fidelity. Transitions between cell cycle stages are triggered by changes in the phosphorylation state and levels of components of the cell cycle machinery. Entry into S-phase and M-phase are mediated by cyclin-dependent kinases (Cdks), serine-threonine kinases that require a regulatory cyclin subunit for their activity. Resetting the system to the interphase state is mediated by protein phosphatases (PPs) that counteract Cdks by dephosphorylating their substrates. To avoid futile cycles of phosphorylation and dephosphorylation, Cdks and PPs must be regulated in a manner such that their activities are mutually exclusive.
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Affiliation(s)
- Andreas Heim
- Department of Biology and Konstanz Research School Chemical Biology (KoRS-CB), University of Konstanz, Universitätsstr. 10, 78457, Konstanz, Germany
| | - Beata Rymarczyk
- Department of Biology and Konstanz Research School Chemical Biology (KoRS-CB), University of Konstanz, Universitätsstr. 10, 78457, Konstanz, Germany
| | - Thomas U Mayer
- Department of Biology and Konstanz Research School Chemical Biology (KoRS-CB), University of Konstanz, Universitätsstr. 10, 78457, Konstanz, Germany.
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15
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Lai TY, Yen CJ, Tsai HW, Yang YS, Hong WF, Chiang CW. The B56γ3 regulatory subunit-containing protein phosphatase 2A outcompetes Akt to regulate p27KIP1 subcellular localization by selectively dephosphorylating phospho-Thr157 of p27KIP1. Oncotarget 2016; 7:4542-58. [PMID: 26684356 PMCID: PMC4826225 DOI: 10.18632/oncotarget.6609] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Accepted: 12/02/2015] [Indexed: 01/01/2023] Open
Abstract
The B56γ-containing protein phosphatase 2A (PP2A-B56γ) has been postulated to have tumor suppressive functions. Here, we report regulation of p27KIP1 subcellular localization by PP2A-B56γ3. B56γ3 overexpression enhanced nuclear localization of p27KIP1, whereas knockdown of B56γ3 decreased p27KIP1 nuclear localization. B56γ3 overexpression decreased phosphorylation at Thr157 (phospho-Thr157), whose phosphorylation promotes cytoplasmic localization of p27KIP1, whereas B56γ3 knockdown significantly increased the level of phospho-Thr157. In vitro, PP2A-B56γ3 catalyzed dephosphorylation of phospho-Thr157 in a dose-dependent and okadaic acid-sensitive manner. B56γ3 did not increase p27KIP1 nuclear localization by down-regulating the upstream kinase Akt activity and outcompeted a myristoylated constitutively active Akt (Aktca) in regulating Thr157 phosphorylation and subcellular localization of p27KIP1. In addition, results of interaction domain mapping revealed that both the N-terminal and C-terminal domains of p27 and a domain at the C-terminus of B56γ3 are required for interaction between p27 and B56γ3. Furthermore, we demonstrated that p27KIP1 levels are positively correlated with B56γ levels in both non-tumor and tumor parts of a set of human colon tissue specimens. However, positive correlation between nuclear p27KIP1 levels and B56γ levels was found only in the non-tumor parts, but not in tumor parts of these tissues, implicating a dysregulation in PP2A-B56γ3-regulated p27KIP1 nuclear localization in these tumor tissues. Altogether, this study provides a new mechanism by which the PP2A-B56γ3 holoenzyme plays its tumor suppressor role.
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Affiliation(s)
- Tai-Yu Lai
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Chia-Jui Yen
- Department of Internal Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Institute of Clinical Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Hung-Wen Tsai
- Department of Pathology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Yu-San Yang
- Institute of Molecular Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Wei-Fu Hong
- Institute of Molecular Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Chi-Wu Chiang
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Institute of Molecular Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Center for Infectious Disease and Signaling Research, National Cheng Kung University, Tainan, Taiwan
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16
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Lorenzen-Schmidt I, Clarke SB, Pyle WG. The neglected messengers: Control of cardiac myofilaments by protein phosphatases. J Mol Cell Cardiol 2016; 101:81-89. [PMID: 27721025 DOI: 10.1016/j.yjmcc.2016.10.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Revised: 10/03/2016] [Accepted: 10/05/2016] [Indexed: 01/21/2023]
Abstract
Cardiac myofilaments act as the central contractile apparatus of heart muscle cells. Covalent modification of constituent proteins through phosphorylation is a rapid and powerful mechanism to control myofilament function, and is increasingly seen as a mechanism of disease. While the relationship between protein kinases and cardiac myofilaments has been widely examined, the impact of protein dephosphorylation by protein phosphatases is poorly understood. This review outlines the mechanisms by which the mostly widely expressed protein phosphatases in cardiac myocytes regulate myofilament function, and the emerging role of myofilament-associated protein phosphatases in heart failure. The importance of regulatory subunits and subcellular compartmentalization in determining the functional impact of protein phosphatases on myofilament and myocardial function is also discussed, as are discrepancies about the roles of protein phosphatases in regulating myofilament function. The potential for targeting these molecular messengers in the treatment of heart failure is discussed as a key future direction.
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Affiliation(s)
- Ilka Lorenzen-Schmidt
- Centre for Cardiovascular Investigations, Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Samantha B Clarke
- Centre for Cardiovascular Investigations, Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - W Glen Pyle
- Centre for Cardiovascular Investigations, Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, ON N1G 2W1, Canada.
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17
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Wu J, Wang J, Zeng X, Chen Y, Xia J, Wang S, Huang Z, Chen W, Shen Z. Protein phosphatase 2A regulatory subunit B56β modulates erythroid differentiation. Biochem Biophys Res Commun 2016; 478:1179-84. [PMID: 27544028 DOI: 10.1016/j.bbrc.2016.08.090] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 08/16/2016] [Indexed: 11/29/2022]
Abstract
Anemia due to attenuated erythroid terminal differentiation is one of the most common hematological disorders occurring at all stages of life. We previously demonstrated that catalytic subunit α of protein phosphatase 2A (PP2Acα) modulates fetal liver erythropoiesis. However the corresponding PP2A regulatory subunit in this process remains unknown. In this study, we report that chemical inhibition of PP2A activity with okadaic acid impairs hemin-induced erythroid differentiation. Interestingly, B56 family member B56β is the only regulatory subunit whose expression is induced by both erythropoietin in fetal liver cells and hemin in erythroleukemia K562 cells. Finally, knockdown of B56β attenuates hemin-induced K562 erythroid differentiation. Collectively, our data identify B56β as the potential functional regulatory subunit of PP2A in erythroid differentiation, shedding light on new target for precise modulation of PP2A activity for treatment of anemia and related diseases.
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Affiliation(s)
- Jianping Wu
- Orthopedic Department of the Second Affiliated Hospital of Soochow University, Suzhou 215000, China
| | - Jun Wang
- Emergency Department of the First Affiliated Hospital of Soochow University, Suzhou 215006, China
| | - Xiansheng Zeng
- Department of Cardiology of the First Affiliated Hospital, Soochow University, Suzhou 215006, China
| | - Yueqiu Chen
- Institute for Cardiovascular Science & Department of Cardiovascular Surgery of the First Affiliated Hospital, Soochow University, Suzhou 215006, China
| | - Jun Xia
- Institute for Cardiovascular Science & Department of Cardiovascular Surgery of the First Affiliated Hospital, Soochow University, Suzhou 215006, China
| | - Shizhen Wang
- Institute for Cardiovascular Science & Department of Cardiovascular Surgery of the First Affiliated Hospital, Soochow University, Suzhou 215006, China
| | - Zan Huang
- Jiangsu Province Key Laboratory of Gastrointestinal Nutrition and Animal Health, College of Animal Science and Technology, Nanjing Agriculture University, Nanjing 210000, China.
| | - Weiqian Chen
- Institute for Cardiovascular Science & Department of Cardiovascular Surgery of the First Affiliated Hospital, Soochow University, Suzhou 215006, China.
| | - Zhenya Shen
- Department of Cardiovascular Surgery of the First Affiliated Hospital & Institute for Cardiovascular Science, Soochow University, Suzhou 215006, China.
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18
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The broken "Off" switch in cancer signaling: PP2A as a regulator of tumorigenesis, drug resistance, and immune surveillance. BBA CLINICAL 2016; 6:87-99. [PMID: 27556014 PMCID: PMC4986044 DOI: 10.1016/j.bbacli.2016.08.002] [Citation(s) in RCA: 112] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/02/2016] [Revised: 08/01/2016] [Accepted: 08/02/2016] [Indexed: 12/31/2022]
Abstract
Aberrant activation of signal transduction pathways can transform a normal cell to a malignant one and can impart survival properties that render cancer cells resistant to therapy. A diverse set of cascades have been implicated in various cancers including those mediated by serine/threonine kinases such RAS, PI3K/AKT, and PKC. Signal transduction is a dynamic process involving both "On" and "Off" switches. Activating mutations of RAS or PI3K can be viewed as the switch being stuck in the "On" position resulting in continued signaling by a survival and/or proliferation pathway. On the other hand, inactivation of protein phosphatases such as the PP2A family can be seen as the defective "Off" switch that similarly can activate these pathways. A problem for therapeutic targeting of PP2A is that the enzyme is a hetero-trimer and thus drug targeting involves complex structures. More importantly, since PP2A isoforms generally act as tumor suppressors one would want to activate these enzymes rather than suppress them. The elucidation of the role of cellular inhibitors like SET and CIP2A in cancer suggests that targeting these proteins can have therapeutic efficacy by mechanisms involving PP2A activation. Furthermore, drugs such as FTY-720 can activate PP2A isoforms directly. This review will cover the current state of knowledge of PP2A role as a tumor suppressor in cancer cells and as a mediator of processes that can impact drug resistance and immune surveillance.
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19
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Haesen D, Abbasi Asbagh L, Derua R, Hubert A, Schrauwen S, Hoorne Y, Amant F, Waelkens E, Sablina A, Janssens V. Recurrent PPP2R1A Mutations in Uterine Cancer Act through a Dominant-Negative Mechanism to Promote Malignant Cell Growth. Cancer Res 2016; 76:5719-5731. [PMID: 27485451 DOI: 10.1158/0008-5472.can-15-3342] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 07/14/2016] [Indexed: 11/16/2022]
Abstract
Somatic missense mutations in the Ser/Thr protein phosphatase 2A (PP2A) Aα scaffold subunit gene PPP2R1A are among the few genomic alterations that occur frequently in serous endometrial carcinoma (EC) and carcinosarcoma, two clinically aggressive subtypes of uterine cancer with few therapeutic options. Previous studies reported that cancer-associated Aα mutants exhibit defects in binding to other PP2A subunits and contribute to cancer development by a mechanism of haploinsufficiency. Here we report on the functional significance of the most recurrent PPP2R1A mutations in human EC, which cluster in Aα HEAT repeats 5 and 7. Beyond predicted loss-of-function effects on the formation of a subset of PP2A holoenzymes, we discovered that Aα mutants behave in a dominant-negative manner due to gain-of-function interactions with the PP2A inhibitor TIPRL1. Dominant-negative Aα mutants retain binding to specific subunits of the B56/B' family and form substrate trapping complexes with impaired phosphatase activity via increased recruitment of TIPRL1. Accordingly, overexpression of the Aα mutants in EC cells harboring wild-type PPP2R1A increased anchorage-independent growth and tumor formation, and triggered hyperphosphorylation of oncogenic PP2A-B56/B' substrates in the GSK3β, Akt, and mTOR/p70S6K signaling pathways. TIPRL1 silencing restored GSK3β phosphorylation and rescued the EC cell growth advantage. Our results reveal how PPP2R1A mutations affect PP2A function and oncogenic signaling, illuminating the genetic basis for serous EC development and its potential control by rationally targeted therapies. Cancer Res; 76(19); 5719-31. ©2016 AACR.
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Affiliation(s)
- Dorien Haesen
- Laboratory of Protein Phosphorylation and Proteomics, Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium
| | - Layka Abbasi Asbagh
- VIB Center for the Biology of Disease, Department of Human Genetics, KU Leuven, Leuven, Belgium
| | - Rita Derua
- Laboratory of Protein Phosphorylation and Proteomics, Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium
| | - Antoine Hubert
- Laboratory of Protein Phosphorylation and Proteomics, Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium
| | - Stefanie Schrauwen
- Laboratory of Gynaecological Oncology, Department of Oncology, KU Leuven, Leuven, Belgium
| | - Yana Hoorne
- Laboratory of Protein Phosphorylation and Proteomics, Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium
| | - Frédéric Amant
- Laboratory of Gynaecological Oncology, Department of Oncology, KU Leuven, Leuven, Belgium
| | - Etienne Waelkens
- Laboratory of Protein Phosphorylation and Proteomics, Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium
| | - Anna Sablina
- VIB Center for the Biology of Disease, Department of Human Genetics, KU Leuven, Leuven, Belgium
| | - Veerle Janssens
- Laboratory of Protein Phosphorylation and Proteomics, Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium.
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20
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Schmoll M, Dattenböck C, Carreras-Villaseñor N, Mendoza-Mendoza A, Tisch D, Alemán MI, Baker SE, Brown C, Cervantes-Badillo MG, Cetz-Chel J, Cristobal-Mondragon GR, Delaye L, Esquivel-Naranjo EU, Frischmann A, Gallardo-Negrete JDJ, García-Esquivel M, Gomez-Rodriguez EY, Greenwood DR, Hernández-Oñate M, Kruszewska JS, Lawry R, Mora-Montes HM, Muñoz-Centeno T, Nieto-Jacobo MF, Nogueira Lopez G, Olmedo-Monfil V, Osorio-Concepcion M, Piłsyk S, Pomraning KR, Rodriguez-Iglesias A, Rosales-Saavedra MT, Sánchez-Arreguín JA, Seidl-Seiboth V, Stewart A, Uresti-Rivera EE, Wang CL, Wang TF, Zeilinger S, Casas-Flores S, Herrera-Estrella A. The Genomes of Three Uneven Siblings: Footprints of the Lifestyles of Three Trichoderma Species. Microbiol Mol Biol Rev 2016; 80:205-327. [PMID: 26864432 PMCID: PMC4771370 DOI: 10.1128/mmbr.00040-15] [Citation(s) in RCA: 121] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The genus Trichoderma contains fungi with high relevance for humans, with applications in enzyme production for plant cell wall degradation and use in biocontrol. Here, we provide a broad, comprehensive overview of the genomic content of these species for "hot topic" research aspects, including CAZymes, transport, transcription factors, and development, along with a detailed analysis and annotation of less-studied topics, such as signal transduction, genome integrity, chromatin, photobiology, or lipid, sulfur, and nitrogen metabolism in T. reesei, T. atroviride, and T. virens, and we open up new perspectives to those topics discussed previously. In total, we covered more than 2,000 of the predicted 9,000 to 11,000 genes of each Trichoderma species discussed, which is >20% of the respective gene content. Additionally, we considered available transcriptome data for the annotated genes. Highlights of our analyses include overall carbohydrate cleavage preferences due to the different genomic contents and regulation of the respective genes. We found light regulation of many sulfur metabolic genes. Additionally, a new Golgi 1,2-mannosidase likely involved in N-linked glycosylation was detected, as were indications for the ability of Trichoderma spp. to generate hybrid galactose-containing N-linked glycans. The genomic inventory of effector proteins revealed numerous compounds unique to Trichoderma, and these warrant further investigation. We found interesting expansions in the Trichoderma genus in several signaling pathways, such as G-protein-coupled receptors, RAS GTPases, and casein kinases. A particularly interesting feature absolutely unique to T. atroviride is the duplication of the alternative sulfur amino acid synthesis pathway.
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Affiliation(s)
- Monika Schmoll
- Austrian Institute of Technology, Department Health and Environment, Bioresources Unit, Tulln, Austria
| | - Christoph Dattenböck
- Austrian Institute of Technology, Department Health and Environment, Bioresources Unit, Tulln, Austria
| | | | | | - Doris Tisch
- Research Division Biotechnology and Microbiology, Institute of Chemical Engineering, TU Wien, Vienna, Austria
| | - Mario Ivan Alemán
- Cinvestav, Department of Genetic Engineering, Irapuato, Guanajuato, Mexico
| | - Scott E Baker
- Pacific Northwest National Laboratory, Richland, Washington, USA
| | - Christopher Brown
- University of Otago, Department of Biochemistry and Genetics, Dunedin, New Zealand
| | | | - José Cetz-Chel
- LANGEBIO, National Laboratory of Genomics for Biodiversity, Cinvestav-Irapuato, Guanajuato, Mexico
| | | | - Luis Delaye
- Cinvestav, Department of Genetic Engineering, Irapuato, Guanajuato, Mexico
| | | | - Alexa Frischmann
- Research Division Biotechnology and Microbiology, Institute of Chemical Engineering, TU Wien, Vienna, Austria
| | | | - Monica García-Esquivel
- LANGEBIO, National Laboratory of Genomics for Biodiversity, Cinvestav-Irapuato, Guanajuato, Mexico
| | | | - David R Greenwood
- The University of Auckland, School of Biological Sciences, Auckland, New Zealand
| | - Miguel Hernández-Oñate
- LANGEBIO, National Laboratory of Genomics for Biodiversity, Cinvestav-Irapuato, Guanajuato, Mexico
| | - Joanna S Kruszewska
- Polish Academy of Sciences, Institute of Biochemistry and Biophysics, Laboratory of Fungal Glycobiology, Warsaw, Poland
| | - Robert Lawry
- Lincoln University, Bio-Protection Research Centre, Lincoln, Canterbury, New Zealand
| | | | | | | | | | | | | | - Sebastian Piłsyk
- Polish Academy of Sciences, Institute of Biochemistry and Biophysics, Laboratory of Fungal Glycobiology, Warsaw, Poland
| | - Kyle R Pomraning
- Pacific Northwest National Laboratory, Richland, Washington, USA
| | - Aroa Rodriguez-Iglesias
- Austrian Institute of Technology, Department Health and Environment, Bioresources Unit, Tulln, Austria
| | | | | | - Verena Seidl-Seiboth
- Research Division Biotechnology and Microbiology, Institute of Chemical Engineering, TU Wien, Vienna, Austria
| | | | | | - Chih-Li Wang
- National Chung-Hsing University, Department of Plant Pathology, Taichung, Taiwan
| | - Ting-Fang Wang
- Academia Sinica, Institute of Molecular Biology, Taipei, Taiwan
| | - Susanne Zeilinger
- Research Division Biotechnology and Microbiology, Institute of Chemical Engineering, TU Wien, Vienna, Austria University of Innsbruck, Institute of Microbiology, Innsbruck, Austria
| | | | - Alfredo Herrera-Estrella
- LANGEBIO, National Laboratory of Genomics for Biodiversity, Cinvestav-Irapuato, Guanajuato, Mexico
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21
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Bidinosti M, Botta P, Krüttner S, Proenca CC, Stoehr N, Bernhard M, Fruh I, Mueller M, Bonenfant D, Voshol H, Carbone W, Neal SJ, McTighe SM, Roma G, Dolmetsch RE, Porter JA, Caroni P, Bouwmeester T, Lüthi A, Galimberti I. CLK2 inhibition ameliorates autistic features associated with SHANK3 deficiency. Science 2016; 351:1199-203. [PMID: 26847545 DOI: 10.1126/science.aad5487] [Citation(s) in RCA: 115] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Accepted: 01/22/2016] [Indexed: 12/17/2022]
Abstract
SH3 and multiple ankyrin repeat domains 3 (SHANK3) haploinsufficiency is causative for the neurological features of Phelan-McDermid syndrome (PMDS), including a high risk of autism spectrum disorder (ASD). We used unbiased, quantitative proteomics to identify changes in the phosphoproteome of Shank3-deficient neurons. Down-regulation of protein kinase B (PKB/Akt)-mammalian target of rapamycin complex 1 (mTORC1) signaling resulted from enhanced phosphorylation and activation of serine/threonine protein phosphatase 2A (PP2A) regulatory subunit, B56β, due to increased steady-state levels of its kinase, Cdc2-like kinase 2 (CLK2). Pharmacological and genetic activation of Akt or inhibition of CLK2 relieved synaptic deficits in Shank3-deficient and PMDS patient-derived neurons. CLK2 inhibition also restored normal sociability in a Shank3-deficient mouse model. Our study thereby provides a novel mechanistic and potentially therapeutic understanding of deregulated signaling downstream of Shank3 deficiency.
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Affiliation(s)
- Michael Bidinosti
- Developmental Molecular Pathways, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Paolo Botta
- Friedrich Miescher Institute, Basel, Switzerland
| | | | - Catia C Proenca
- Developmental Molecular Pathways, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Natacha Stoehr
- Developmental Molecular Pathways, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Mario Bernhard
- Developmental Molecular Pathways, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Isabelle Fruh
- Developmental Molecular Pathways, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Matthias Mueller
- Developmental Molecular Pathways, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Debora Bonenfant
- Analytical Sciences and Imaging, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Hans Voshol
- Analytical Sciences and Imaging, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Walter Carbone
- Developmental Molecular Pathways, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Sarah J Neal
- Neuroscience, Novartis Institutes for Biomedical Research, Cambridge, USA
| | | | - Guglielmo Roma
- Developmental Molecular Pathways, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | | | - Jeffrey A Porter
- Developmental Molecular Pathways, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Pico Caroni
- Friedrich Miescher Institute, Basel, Switzerland
| | - Tewis Bouwmeester
- Developmental Molecular Pathways, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | | | - Ivan Galimberti
- Developmental Molecular Pathways, Novartis Institutes for Biomedical Research, Basel, Switzerland.
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22
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Maertens GN. B'-protein phosphatase 2A is a functional binding partner of delta-retroviral integrase. Nucleic Acids Res 2015; 44:364-76. [PMID: 26657642 PMCID: PMC4705670 DOI: 10.1093/nar/gkv1347] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Accepted: 11/19/2015] [Indexed: 12/31/2022] Open
Abstract
To establish infection, a retrovirus must insert a DNA copy of its RNA genome into host chromatin. This reaction is catalysed by the virally encoded enzyme integrase (IN) and is facilitated by viral genus-specific host factors. Herein, cellular serine/threonine protein phosphatase 2A (PP2A) is identified as a functional IN binding partner exclusive to δ-retroviruses, including human T cell lymphotropic virus type 1 and 2 (HTLV-1 and HTLV-2) and bovine leukaemia virus (BLV). PP2A is a heterotrimer composed of a scaffold, catalytic and one of any of four families of regulatory subunits, and the interaction is specific to the B' family of the regulatory subunits. B'-PP2A and HTLV-1 IN display nuclear co-localization, and the B' subunit stimulates concerted strand transfer activity of δ-retroviral INs in vitro. The protein-protein interaction interface maps to a patch of highly conserved residues on B', which when mutated render B' incapable of binding to and stimulating HTLV-1 and -2 IN strand transfer activity.
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Affiliation(s)
- Goedele N Maertens
- Division of Infectious Diseases, St. Mary's campus, Imperial College London, Norfolk Place, London, W2 1PG, UK
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23
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Abstract
In 1975, tau protein was isolated as a microtubule-associated factor from the porcine brain. In the previous year, a paired helical filament (PHF) protein had been identified in neurofibrillary tangles in the brains of individuals with Alzheimer disease (AD), but it was not until 1986 that the PHF protein and tau were discovered to be one and the same. In the AD brain, tau was found to be abnormally hyperphosphorylated, and it inhibited rather than promoted in vitro microtubule assembly. Almost 80 disease-causing exonic missense and intronic silent mutations in the tau gene have been found in familial cases of frontotemporal dementia but, to date, no such mutation has been found in AD. The first phase I clinical trial of an active tau immunization vaccine in patients with AD was recently completed. Assays for tau levels in cerebrospinal fluid and plasma are now available, and tau radiotracers for PET are under development. In this article, we provide an overview of the pivotal discoveries in the tau research field over the past 40 years. We also review the current status of the field, including disease mechanisms and therapeutic approaches.
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Affiliation(s)
- Khalid Iqbal
- Department of Neurochemistry, New York State Institute for Basic Research in Developmental Disabilities, Inge Grundke-Iqbal Research Floor, 1050 Forest Hill Road, Staten Island, New York 10314, USA
| | - Fei Liu
- Department of Neurochemistry, New York State Institute for Basic Research in Developmental Disabilities, Inge Grundke-Iqbal Research Floor, 1050 Forest Hill Road, Staten Island, New York 10314, USA
| | - Cheng-Xin Gong
- Department of Neurochemistry, New York State Institute for Basic Research in Developmental Disabilities, Inge Grundke-Iqbal Research Floor, 1050 Forest Hill Road, Staten Island, New York 10314, USA
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24
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Yu VZ, Wong VCL, Dai W, Ko JMY, Lam AKY, Chan KW, Samant RS, Lung HL, Shuen WH, Law S, Chan YP, Lee NPY, Tong DKH, Law TT, Lee VHF, Lung ML. Nuclear Localization of DNAJB6 Is Associated With Survival of Patients With Esophageal Cancer and Reduces AKT Signaling and Proliferation of Cancer Cells. Gastroenterology 2015; 149:1825-1836.e5. [PMID: 26302489 DOI: 10.1053/j.gastro.2015.08.025] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Revised: 07/14/2015] [Accepted: 08/19/2015] [Indexed: 12/02/2022]
Abstract
BACKGROUND & AIMS The DnaJ (Hsp40) homolog, subfamily B, member 6 (DNAJB6) is part of a family of proteins that regulates chaperone activities. One of its isoforms, DNAJB6a, contains a nuclear localization signal and regulates β-catenin signaling during breast cancer development. We investigated the role of DNAJB6 in the pathogenesis of esophageal squamous cell carcinoma (ESCC). METHODS We performed immunohistochemical analyses of primary ESCC samples and lymph node metastases from a cohort of 160 patients who underwent esophagectomy with no preoperative chemoradiotherapy at Hong Kong Queen Mary Hospital. Data were collected on patient outcomes over a median time of 12.1 ± 2.9 months. Retrospective survival association analyses were performed. Wild-type and mutant forms of DNAJB6a were overexpressed in cancer cell lines (KYSE510, KYSE 30TSI, KYSE140, and KYSE70TS), which were analyzed in proliferation and immunoblot assays, or injected subcutaneously into nude mice. Levels of DNAJB6 were knocked down in ESCC cell lines (KYSE450 and T.Tn), immortalized normal esophageal epithelial cell lines (NE3 and NE083), and other cells with short hairpin RNAs, or by genome engineering. Bimolecular fluorescence complementation was used to study interactions between proteins in living cells. RESULTS In primary ESCC samples, patients whose tumors had high nuclear levels of DNAJB6 had longer overall survival times (19.2 ± 1.8 months; 95% confidence interval [CI], 15.6-22.8 mo) than patients whose tumors had low nuclear levels of DNAJB6 (12.6 ± 1.4 mo; 95% CI, 9.8-15.4 mo; P = .004, log-rank test). Based on Cox regression analysis, patients whose tumors had high nuclear levels of DNAJB6 had a lower risk of death than patients with low levels (hazard ratio, 0.562; 95% CI, 0.379-0.834; P = .004). Based on log-rank analysis and Cox regression analysis, the combination of the nuclear level of DNAJB6 and the presence of lymph node metastases at diagnosis could be used to stratify patients into groups with good or bad outcomes (P < .0005 for both analyses). There was a negative association between the nuclear level of DNAJB6 and the presence of lymph node metastases (P = .022; Pearson χ(2) test). Cancer cell lines that overexpressed DNAJB6a formed tumors more slowly in nude mice than control cells or cells that expressed a mutant form of DNAJB6a that did not localize to the nucleus. DNAJB6 knockdown in cancer cell lines promoted their growth as xenograft tumors in mice. A motif of histidine, proline, and aspartic acid in the J domain of DNAJB6a was required for its tumor-suppressive effects and signaling via AKT1. Loss of DNAJB6a resulted in up-regulation of AKT signaling in cancer cell lines and immortalized esophageal epithelial cells. Expression of a constitutively active form of AKT1 restored proliferation to tumor cells that overexpressed DNAJB6a, and DNAJB6a formed a complex with AKT1 in living cells. The expression of DNAJB6a reduced the sensitivity of ESCC to AKT inhibitors; the expression level of DNAJB6a affected AKT signaling in multiple cancer cell lines. CONCLUSIONS Nuclear localization of DNAJB6 is associated with longer survival times of patients with ESCC. DNAJB6a reduces AKT signaling, and DNAJB6 expression in cancer cells reduces their proliferation and growth of xenograft tumors in mice. DNAJB6a might be developed as a biomarker for progression of ESCC.
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Affiliation(s)
- Valen Zhuoyou Yu
- Department of Clinical Oncology, University of Hong Kong Li Ka Shing Faculty of Medicine, Pokfulam, Hong Kong, Special Administrative Region
| | - Victor Chun-Lam Wong
- Department of Clinical Oncology, University of Hong Kong Li Ka Shing Faculty of Medicine, Pokfulam, Hong Kong, Special Administrative Region
| | - Wei Dai
- Department of Clinical Oncology, University of Hong Kong Li Ka Shing Faculty of Medicine, Pokfulam, Hong Kong, Special Administrative Region
| | - Josephine Mun-Yee Ko
- Department of Clinical Oncology, University of Hong Kong Li Ka Shing Faculty of Medicine, Pokfulam, Hong Kong, Special Administrative Region
| | - Alfred King-Yin Lam
- Department of Cancer Molecular Pathology, Griffith Medical School and Menzies Health Institute Queensland, Griffith University, Gold Coast, Australia
| | - Kwok Wah Chan
- Department of Pathology, University of Hong Kong Li Ka Shing Faculty of Medicine, Pokfulam, Hong Kong, Special Administrative Region; Center for Cancer Research, University of Hong Kong Li Ka Shing Faculty of Medicine, Pokfulam, Hong Kong, Special Administrative Region
| | - Rajeev S Samant
- Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama
| | - Hong Lok Lung
- Department of Clinical Oncology, University of Hong Kong Li Ka Shing Faculty of Medicine, Pokfulam, Hong Kong, Special Administrative Region; Center for Cancer Research, University of Hong Kong Li Ka Shing Faculty of Medicine, Pokfulam, Hong Kong, Special Administrative Region
| | - Wai Ho Shuen
- Department of Clinical Oncology, University of Hong Kong Li Ka Shing Faculty of Medicine, Pokfulam, Hong Kong, Special Administrative Region
| | - Simon Law
- Center for Cancer Research, University of Hong Kong Li Ka Shing Faculty of Medicine, Pokfulam, Hong Kong, Special Administrative Region; Department of Surgery, University of Hong Kong Li Ka Shing Faculty of Medicine, Pokfulam, Hong Kong, Special Administrative Region
| | - Yuen Piu Chan
- Department of Pathology, University of Hong Kong Li Ka Shing Faculty of Medicine, Pokfulam, Hong Kong, Special Administrative Region
| | - Nikki Pui-Yue Lee
- Center for Cancer Research, University of Hong Kong Li Ka Shing Faculty of Medicine, Pokfulam, Hong Kong, Special Administrative Region; Department of Surgery, University of Hong Kong Li Ka Shing Faculty of Medicine, Pokfulam, Hong Kong, Special Administrative Region
| | - Daniel King Hung Tong
- Department of Surgery, University of Hong Kong Li Ka Shing Faculty of Medicine, Pokfulam, Hong Kong, Special Administrative Region
| | - Tsz Ting Law
- Department of Surgery, University of Hong Kong Li Ka Shing Faculty of Medicine, Pokfulam, Hong Kong, Special Administrative Region
| | - Victor Ho-Fun Lee
- Department of Clinical Oncology, University of Hong Kong Li Ka Shing Faculty of Medicine, Pokfulam, Hong Kong, Special Administrative Region; Center for Cancer Research, University of Hong Kong Li Ka Shing Faculty of Medicine, Pokfulam, Hong Kong, Special Administrative Region
| | - Maria Li Lung
- Department of Clinical Oncology, University of Hong Kong Li Ka Shing Faculty of Medicine, Pokfulam, Hong Kong, Special Administrative Region; Center for Cancer Research, University of Hong Kong Li Ka Shing Faculty of Medicine, Pokfulam, Hong Kong, Special Administrative Region.
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25
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Shang L, Henderson LB, Cho MT, Petrey DS, Fong CT, Haude KM, Shur N, Lundberg J, Hauser N, Carmichael J, Innis J, Schuette J, Wu YW, Asaikar S, Pearson M, Folk L, Retterer K, Monaghan KG, Chung WK. De novo missense variants in PPP2R5D are associated with intellectual disability, macrocephaly, hypotonia, and autism. Neurogenetics 2015; 17:43-9. [PMID: 26576547 DOI: 10.1007/s10048-015-0466-9] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Accepted: 10/22/2015] [Indexed: 12/19/2022]
Abstract
Protein phosphatase 2A (PP2A) is a heterotrimeric protein serine/threonine phosphatase and is involved in a broad range of cellular processes. PPP2R5D is a regulatory B subunit of PP2A and plays an important role in regulating key neuronal and developmental regulation processes such as PI3K/AKT and glycogen synthase kinase 3 beta (GSK3β)-mediated cell growth, chromatin remodeling, and gene transcriptional regulation. Using whole-exome sequencing (WES), we identified four de novo variants in PPP2R5D in a total of seven unrelated individuals with intellectual disability (ID) and other shared clinical characteristics, including autism spectrum disorder, macrocephaly, hypotonia, seizures, and dysmorphic features. Among the four variants, two have been previously reported and two are novel. All four amino acids are highly conserved among the PP2A subunit family, and all change a negatively charged acidic glutamic acid (E) to a positively charged basic lysine (K) and are predicted to disrupt the PP2A subunit binding and impair the dephosphorylation capacity. Our data provides further support for PPP2R5D as a genetic cause of ID.
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Affiliation(s)
- Linshan Shang
- Department of Pediatrics, Columbia University Medical Center, New York, NY, USA
| | | | | | - Donald S Petrey
- Department of Biochemistry and Molecular Biophysics, Columbia University Medical Center, New York, NY, USA
| | - Chin-To Fong
- University of Rochester Medical Center, Rochester, NY, USA
| | | | | | | | | | | | - Jeffrey Innis
- Division of Pediatric Genetics, University of Michigan Health System, Ann Arbor, MI, USA
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Jane Schuette
- Division of Pediatric Genetics, University of Michigan Health System, Ann Arbor, MI, USA
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Yvonne W Wu
- Departments of Neurology and Pediatrics, University of California San Francisco, San Francisco, CA, USA
| | | | | | | | | | | | - Wendy K Chung
- Department of Pediatrics, Columbia University Medical Center, New York, NY, USA.
- Department of Medicine, Columbia University Medical Center, New York, NY, USA.
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26
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Liu X, Xiong X, Yang J, Zhou L, Yang B, Ai H, Ma H, Xie X, Huang Y, Fang S, Xiao S, Ren J, Ma J, Huang L. Genome-wide association analyses for meat quality traits in Chinese Erhualian pigs and a Western Duroc × (Landrace × Yorkshire) commercial population. Genet Sel Evol 2015; 47:44. [PMID: 25962760 PMCID: PMC4427942 DOI: 10.1186/s12711-015-0120-x] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Accepted: 04/09/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Understanding the genetic mechanisms that underlie meat quality traits is essential to improve pork quality. To date, most quantitative trait loci (QTL) analyses have been performed on F2 crosses between outbred pig strains and have led to the identification of numerous QTL. However, because linkage disequilibrium is high in such crosses, QTL mapping precision is unsatisfactory and only a few QTL have been found to segregate within outbred strains, which limits their use to improve animal performance. To detect QTL in outbred pig populations of Chinese and Western origins, we performed genome-wide association studies (GWAS) for meat quality traits in Chinese purebred Erhualian pigs and a Western Duroc × (Landrace × Yorkshire) (DLY) commercial population. METHODS Three hundred and thirty six Chinese Erhualian and 610 DLY pigs were genotyped using the Illumina PorcineSNP60K Beadchip and evaluated for 20 meat quality traits. After quality control, 35 985 and 56 216 single nucleotide polymorphisms (SNPs) were available for the Chinese Erhualian and DLY datasets, respectively, and were used to perform two separate GWAS. We also performed a meta-analysis that combined P-values and effects of 29 516 SNPs that were common to Erhualian, DLY, F2 and Sutai pig populations. RESULTS We detected 28 and nine suggestive SNPs that surpassed the significance level for meat quality in Erhualian and DLY pigs, respectively. Among these SNPs, ss131261254 on pig chromosome 4 (SSC4) was the most significant (P = 7.97E-09) and was associated with drip loss in Erhualian pigs. Our results suggested that at least two QTL on SSC12 and on SSC15 may have pleiotropic effects on several related traits. All the QTL that were detected by GWAS were population-specific, including 12 novel regions. However, the meta-analysis revealed seven novel QTL for meat characteristics, which suggests the existence of common underlying variants that may differ in frequency across populations. These QTL regions contain several relevant candidate genes. CONCLUSIONS These findings provide valuable insights into the molecular basis of convergent evolution of meat quality traits in Chinese and Western breeds that show divergent phenotypes. They may contribute to genetic improvement of purebreds for crossbred performance.
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Affiliation(s)
- Xianxian Liu
- Key Laboratory for Animal Biotechnology of Jiangxi Province and the Ministry of Agriculture of China, Jiangxi Agricultural University, Nanchang, 330045, China.
| | - Xinwei Xiong
- Key Laboratory for Animal Biotechnology of Jiangxi Province and the Ministry of Agriculture of China, Jiangxi Agricultural University, Nanchang, 330045, China.
| | - Jie Yang
- Key Laboratory for Animal Biotechnology of Jiangxi Province and the Ministry of Agriculture of China, Jiangxi Agricultural University, Nanchang, 330045, China.
| | - Lisheng Zhou
- Key Laboratory for Animal Biotechnology of Jiangxi Province and the Ministry of Agriculture of China, Jiangxi Agricultural University, Nanchang, 330045, China.
| | - Bin Yang
- Key Laboratory for Animal Biotechnology of Jiangxi Province and the Ministry of Agriculture of China, Jiangxi Agricultural University, Nanchang, 330045, China.
| | - Huashui Ai
- Key Laboratory for Animal Biotechnology of Jiangxi Province and the Ministry of Agriculture of China, Jiangxi Agricultural University, Nanchang, 330045, China.
| | - Huanban Ma
- Key Laboratory for Animal Biotechnology of Jiangxi Province and the Ministry of Agriculture of China, Jiangxi Agricultural University, Nanchang, 330045, China.
| | - Xianhua Xie
- Key Laboratory for Animal Biotechnology of Jiangxi Province and the Ministry of Agriculture of China, Jiangxi Agricultural University, Nanchang, 330045, China.
| | - Yixuan Huang
- Key Laboratory for Animal Biotechnology of Jiangxi Province and the Ministry of Agriculture of China, Jiangxi Agricultural University, Nanchang, 330045, China.
| | - Shaoming Fang
- Key Laboratory for Animal Biotechnology of Jiangxi Province and the Ministry of Agriculture of China, Jiangxi Agricultural University, Nanchang, 330045, China.
| | - Shijun Xiao
- Key Laboratory for Animal Biotechnology of Jiangxi Province and the Ministry of Agriculture of China, Jiangxi Agricultural University, Nanchang, 330045, China.
| | - Jun Ren
- Key Laboratory for Animal Biotechnology of Jiangxi Province and the Ministry of Agriculture of China, Jiangxi Agricultural University, Nanchang, 330045, China.
| | - Junwu Ma
- Key Laboratory for Animal Biotechnology of Jiangxi Province and the Ministry of Agriculture of China, Jiangxi Agricultural University, Nanchang, 330045, China.
| | - Lusheng Huang
- Key Laboratory for Animal Biotechnology of Jiangxi Province and the Ministry of Agriculture of China, Jiangxi Agricultural University, Nanchang, 330045, China.
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27
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Ma J, Feng Y, Xie W, Li X. PP2A (PR65) in Silver Carp: cDNA Cloning and Expression Analysis. J Biochem Mol Toxicol 2015; 29:399-409. [DOI: 10.1002/jbt.21706] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Revised: 02/07/2015] [Accepted: 03/01/2015] [Indexed: 12/27/2022]
Affiliation(s)
- Junguo Ma
- College of Life Science; Henan Normal University; Xinxiang Henan 453007 China
| | - Yiyi Feng
- College of Life Science; Henan Normal University; Xinxiang Henan 453007 China
| | - Wenjie Xie
- College of Life Science; Henan Normal University; Xinxiang Henan 453007 China
| | - Xiaoyu Li
- College of Life Science; Henan Normal University; Xinxiang Henan 453007 China
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28
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Cheong JK, Zhang F, Chua PJ, Bay BH, Thorburn A, Virshup DM. Casein kinase 1α-dependent feedback loop controls autophagy in RAS-driven cancers. J Clin Invest 2015; 125:1401-18. [PMID: 25798617 DOI: 10.1172/jci78018] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Accepted: 01/28/2015] [Indexed: 12/17/2022] Open
Abstract
Activating mutations in the RAS oncogene are common in cancer but are difficult to therapeutically target. RAS activation promotes autophagy, a highly regulated catabolic process that metabolically buffers cells in response to diverse stresses. Here we report that casein kinase 1α (CK1α), a ubiquitously expressed serine/threonine kinase, is a key negative regulator of oncogenic RAS-induced autophagy. Depletion or pharmacologic inhibition of CK1α enhanced autophagic flux in oncogenic RAS-driven human fibroblasts and multiple cancer cell lines. FOXO3A, a master longevity mediator that transcriptionally regulates diverse autophagy genes, was a critical target of CK1α, as depletion of CK1α reduced levels of phosphorylated FOXO3A and increased expression of FOXO3A-responsive genes. Oncogenic RAS increased CK1α protein abundance via activation of the PI3K/AKT/mTOR pathway. In turn, elevated levels of CK1α increased phosphorylation of nuclear FOXO3A, thereby inhibiting transactivation of genes critical for RAS-induced autophagy. In both RAS-driven cancer cells and murine xenograft models, pharmacologic CK1α inactivation synergized with lysosomotropic agents to inhibit growth and promote tumor cell death. Together, our results identify a kinase feedback loop that influences RAS-dependent autophagy and suggest that targeting CK1α-regulated autophagy offers a potential therapeutic opportunity to treat oncogenic RAS-driven cancers.
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29
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Ruvolo PP. The Interplay between PP2A and microRNAs in Leukemia. Front Oncol 2015; 5:43. [PMID: 25750899 PMCID: PMC4335100 DOI: 10.3389/fonc.2015.00043] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Accepted: 02/05/2015] [Indexed: 12/19/2022] Open
Abstract
Protein phosphatase 2A (PP2A) is a serine/threonine phosphatase family whose members have been implicated in tumor suppression in many cancer models. In many cancers, loss of PP2A activity has been associated with tumorigenesis and drug resistance. Loss of PP2A results in failure to turn off survival signaling cascades that drive drug resistance such as those regulated by protein kinase B. PP2A is responsible for modulating function and controlling expression of tumor suppressors such as p53 and oncogenes such as BCL2 and MYC. Thus, PP2A has diverse functions regulating cell survival. The importance of microRNAs (miRs) is emerging in cancer biology. A role for miR regulation of PP2A is not well understood; however, recent studies suggest a number of clinically significant miRs such as miR-155 and miR-19 may include PP2A targets. We have recently found that a PP2A B subunit (B55α) can regulate a number of miRs in acute myeloid leukemia cells. The identification of a miR/PP2A axis represents a novel regulatory pathway in cellular homeostasis. The ability of miRs to suppress specific PP2A targets and for PP2A to control such miRs can add an extra level of control in signaling that could be used as a rheostat for many signaling cascades that maintain cellular homeostasis. As such, loss of PP2A or expression of miRs relevant for PP2A function could promote tumorigenesis or at least result in drug resistance. In this review, we will cover the current state of miR regulation of PP2A with a focus on leukemia. We will also briefly discuss what is known of PP2A regulation of miR expression.
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Affiliation(s)
- Peter P Ruvolo
- Department of Leukemia, University of Texas MD Anderson Cancer Center , Houston, TX , USA
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30
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Mo ST, Chiang SJ, Lai TY, Cheng YL, Chung CE, Kuo SCH, Reece KM, Chen YC, Chang NS, Wadzinski BE, Chiang CW. Visualization of subunit interactions and ternary complexes of protein phosphatase 2A in mammalian cells. PLoS One 2014; 9:e116074. [PMID: 25536081 PMCID: PMC4275284 DOI: 10.1371/journal.pone.0116074] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 12/01/2014] [Indexed: 11/18/2022] Open
Abstract
Protein phosphatase 2A (PP2A) is a ubiquitous phospho-serine/threonine phosphatase that controls many diverse cellular functions. The predominant form of PP2A is a heterotrimeric holoenzyme consisting of a scaffolding A subunit, a variable regulatory B subunit, and a catalytic C subunit. The C subunit also associates with other interacting partners, such as α4, to form non-canonical PP2A complexes. We report visualization of PP2A complexes in mammalian cells. Bimolecular fluorescence complementation (BiFC) analysis of PP2A subunit interactions demonstrates that the B subunit plays a key role in directing the subcellular localization of PP2A, and confirms that the A subunit functions as a scaffold in recruiting the B and C subunits to form a heterotrimeric holoenzyme. BiFC analysis also reveals that α4 promotes formation of the AC core dimer. Furthermore, we demonstrate visualization of specific ABC holoenzymes in cells by combining BiFC and fluorescence resonance energy transfer (BiFC-FRET). Our studies not only provide direct imaging data to support previous biochemical observations on PP2A complexes, but also offer a promising approach for studying the spatiotemporal distribution of individual PP2A complexes in cells.
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Affiliation(s)
- Shu-Ting Mo
- Institute of Molecular Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Shang-Ju Chiang
- Institute of Molecular Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Tai-Yu Lai
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Yu-Ling Cheng
- Institute of Molecular Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Cheng-En Chung
- Institute of Molecular Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Spencer C. H. Kuo
- Department of Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Kelie M. Reece
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN, United States of America
| | - Yung-Cheng Chen
- Institute of Molecular Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Nan-Shan Chang
- Institute of Molecular Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan
- Center for Infectious Disease and Signaling Research, National Cheng Kung University, Tainan, Taiwan
| | - Brian E. Wadzinski
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN, United States of America
- * E-mail: (CWC); (BEW)
| | - Chi-Wu Chiang
- Institute of Molecular Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan
- Center for Infectious Disease and Signaling Research, National Cheng Kung University, Tainan, Taiwan
- * E-mail: (CWC); (BEW)
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Kirchhefer U, Brekle C, Eskandar J, Isensee G, Kučerová D, Müller FU, Pinet F, Schulte JS, Seidl MD, Boknik P. Cardiac function is regulated by B56α-mediated targeting of protein phosphatase 2A (PP2A) to contractile relevant substrates. J Biol Chem 2014; 289:33862-73. [PMID: 25320082 DOI: 10.1074/jbc.m114.598938] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dephosphorylation of important myocardial proteins is regulated by protein phosphatase 2A (PP2A), representing a heterotrimer that is comprised of catalytic, scaffolding, and regulatory (B) subunits. There is a multitude of B subunit family members directing the PP2A holoenzyme to different myocellular compartments. To gain a better understanding of how these B subunits contribute to the regulation of cardiac performance, we generated transgenic (TG) mice with cardiomyocyte-directed overexpression of B56α, a phosphoprotein of the PP2A-B56 family. The 2-fold overexpression of B56α was associated with an enhanced PP2A activity that was localized mainly in the cytoplasm and myofilament fraction. Contractility was enhanced both at the whole heart level and in isolated cardiomyocytes of TG compared with WT mice. However, peak amplitude of [Ca]i did not differ between TG and WT cardiomyocytes. The basal phosphorylation of cardiac troponin inhibitor (cTnI) and the myosin-binding protein C was reduced by 26 and 35%, respectively, in TG compared with WT hearts. The stimulation of β-adrenergic receptors by isoproterenol (ISO) resulted in an impaired contractile response of TG hearts. At a depolarizing potential of -5 mV, the ICa,L current density was decreased by 28% after administration of ISO in TG cardiomyocytes. In addition, the ISO-stimulated phosphorylation of phospholamban at Ser(16) was reduced by 27% in TG hearts. Thus, the increased PP2A-B56α activity in TG hearts is localized to specific subcellular sites leading to the dephosphorylation of important contractile proteins. This may result in higher myofilament Ca(2+) sensitivity and increased basal contractility in TG hearts. These effects were reversed by β-adrenergic stimulation.
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Affiliation(s)
- Uwe Kirchhefer
- From the Institut für Pharmakologie und Toxikologie, Universitätsklinikum Münster, D-48149 Münster, Germany and
| | - Christiane Brekle
- From the Institut für Pharmakologie und Toxikologie, Universitätsklinikum Münster, D-48149 Münster, Germany and
| | - John Eskandar
- From the Institut für Pharmakologie und Toxikologie, Universitätsklinikum Münster, D-48149 Münster, Germany and
| | - Gunnar Isensee
- From the Institut für Pharmakologie und Toxikologie, Universitätsklinikum Münster, D-48149 Münster, Germany and
| | - Dana Kučerová
- From the Institut für Pharmakologie und Toxikologie, Universitätsklinikum Münster, D-48149 Münster, Germany and
| | - Frank U Müller
- From the Institut für Pharmakologie und Toxikologie, Universitätsklinikum Münster, D-48149 Münster, Germany and
| | - Florence Pinet
- INSERM, U744, Institut Pasteur de Lille, 59019 Lille, France
| | - Jan S Schulte
- From the Institut für Pharmakologie und Toxikologie, Universitätsklinikum Münster, D-48149 Münster, Germany and
| | - Matthias D Seidl
- From the Institut für Pharmakologie und Toxikologie, Universitätsklinikum Münster, D-48149 Münster, Germany and
| | - Peter Boknik
- From the Institut für Pharmakologie und Toxikologie, Universitätsklinikum Münster, D-48149 Münster, Germany and
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32
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Protein phosphatase 2A (PP2A) regulatory subunits ParA and PabA orchestrate septation and conidiation and are essential for PP2A activity in Aspergillus nidulans. EUKARYOTIC CELL 2014; 13:1494-506. [PMID: 25280816 DOI: 10.1128/ec.00201-14] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Protein phosphatase 2A (PP2A) is a major intracellular protein phosphatase that regulates multiple aspects of cell growth and metabolism. Different activities of PP2A and subcellular localization are determined by its regulatory subunits. Here we identified and characterized the functions of two protein phosphatase regulatory subunit homologs, ParA and PabA, in Aspergillus nidulans. Our results demonstrate that ParA localizes to the septum site and that deletion of parA causes hyperseptation, while overexpression of parA abolishes septum formation; this suggests that ParA may function as a negative regulator of septation. In comparison, PabA displays a clear colocalization pattern with 4',6-diamidino-2-phenylindole (DAPI)-stained nuclei, and deletion of pabA induces a remarkable delayed-septation phenotype. Both parA and pabA are required for hyphal growth, conidiation, and self-fertilization, likely to maintain normal levels of PP2A activity. Most interestingly, parA deletion is capable of suppressing septation defects in pabA mutants, suggesting that ParA counteracts PabA during the septation process. In contrast, double mutants of parA and pabA led to synthetic defects in colony growth, indicating that ParA functions synthetically with PabA during hyphal growth. Moreover, unlike the case for PP2A-Par1 and PP2A-Pab1 in yeast (which are negative regulators that inactivate the septation initiation network [SIN]), loss of ParA or PabA fails to suppress defects of temperature-sensitive mutants of the SEPH kinase of the SIN. Thus, our findings support the previously unrealized evidence that the B-family subunits of PP2A have comprehensive functions as partners of heterotrimeric enzyme complexes of PP2A, both spatially and temporally, in A. nidulans.
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Park M, Choi YA, Lee HG, Kim KI, Lim JS, Lee MS, Oh KS, Yang Y. Dephosphorylation of CCAAT/enhancer-binding protein β by protein phosphatase 2A containing B56δ is required at the early time of adipogenesis. Biochim Biophys Acta Mol Cell Biol Lipids 2014; 1841:1608-18. [PMID: 25152162 DOI: 10.1016/j.bbalip.2014.08.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Revised: 07/26/2014] [Accepted: 08/12/2014] [Indexed: 12/11/2022]
Abstract
It is known that protein phosphatase 2A (PP2A) expression is increased in high-fat diet (HFD)-induced obese mice, but the role of PP2A in adipogenesis as well as obesity remains to be addressed. In this study, the role of PP2A in adipogenesis was explored. Preadipocytes were treated with okadaic acid (OA) during adipogenesis and the degree of adipogenesis was determined. The OA treatment blocked adipogenesis at the early time of adipogenesis, but not at the late time. In the early time of adipogenesis, CCAAT/enhancer-binding protein β (C/EBPβ) activation is preceded by the expression of key adipogenic transcription factors including PPARγ and C/EBPα, which function at the late time of adipogenesis, and then C/EBPβ is degraded. However, the inhibition of PP2A by OA treatment sustained phosphorylation of C/EBPβ and delayed its degradation. In turn, PPARγ and C/EBPα activation was altered. Among the various regulatory B56 subunits consisting of PP2A holoenzyme, B56δ was directly bound to C/EBPβ and was responsible for the dephosphorylation of C/EBPβ by PP2A. Taken together, these findings suggest that the phosphorylation of C/EBPβ after hormonal induction has to be inactivated by PP2A containing B56δ at the early time of adipogenesis to allow the completion of adipogenesis.
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Affiliation(s)
- Miyoung Park
- Department of Life Science, Sookmyung Women's University, Seoul 140-742, Republic of Korea
| | - Yeon A Choi
- Department of Life Science, Sookmyung Women's University, Seoul 140-742, Republic of Korea
| | - Hee Gu Lee
- Korea Research Institute of Bioscience and Biotechnology, Daejon 305-333, Republic of Korea
| | - Keun Il Kim
- Department of Life Science, Sookmyung Women's University, Seoul 140-742, Republic of Korea
| | - Jong-Seok Lim
- Department of Life Science, Sookmyung Women's University, Seoul 140-742, Republic of Korea
| | - Myeong-Sok Lee
- Department of Life Science, Sookmyung Women's University, Seoul 140-742, Republic of Korea
| | - Ki-Sook Oh
- Department of Life Science, Sookmyung Women's University, Seoul 140-742, Republic of Korea
| | - Young Yang
- Department of Life Science, Sookmyung Women's University, Seoul 140-742, Republic of Korea.
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Xiao J, Li Y, Prandovszky E, Karuppagounder SS, Talbot CC, Dawson VL, Dawson TM, Yolken RH. MicroRNA-132 dysregulation in Toxoplasma gondii infection has implications for dopamine signaling pathway. Neuroscience 2014; 268:128-38. [PMID: 24657774 DOI: 10.1016/j.neuroscience.2014.03.015] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Revised: 03/05/2014] [Accepted: 03/10/2014] [Indexed: 12/12/2022]
Abstract
Congenital toxoplasmosis and toxoplasmic encephalitis can be associated with severe neuropsychiatric symptoms. However, which host cell processes are regulated and how Toxoplasma gondii affects these changes remain unclear. MicroRNAs (miRNAs) are small noncoding RNA sequences critical to neurodevelopment and adult neuronal processes by coordinating the activity of multiple genes within biological networks. We examined the expression of over 1000 miRNAs in human neuroepithelioma cells in response to infection with Toxoplasma. MiR-132, a cyclic AMP-responsive element binding (CREB)-regulated miRNA, was the only miRNA that was substantially upregulated by all three prototype Toxoplasma strains. The increased expression of miR-132 was also documented in mice following infection with Toxoplasma. To identify cellular pathways regulated by miR-132, we performed target prediction followed by pathway enrichment analysis in the transcriptome of Toxoplasma-infected mice. This led us to identify 20 genes and dopamine receptor signaling was their strongest associated pathway. We then examined myriad aspects of the dopamine pathway in the striatum of Toxoplasma-infected mice 5days after infection. Here we report decreased expression of D1-like dopamine receptors (DRD1, DRD5), metabolizing enzyme (MAOA) and intracellular proteins associated with the transduction of dopamine-mediated signaling (DARPP-32 phosphorylation at Thr34 and Ser97). Increased concentrations of dopamine and its metabolites, serotonin (5-HT) and 5-hydroxyindoleacetic acid were documented by HPLC analysis; however, the metabolism of dopamine was decreased and 5-HT metabolism was unchanged. Our data show that miR-132 is upregulated following infection with Toxoplasma and is associated with changes in dopamine receptor signaling. Our findings provide a possible mechanism for how the parasite contributes to the neuropathology of infection.
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Affiliation(s)
- J Xiao
- Stanley Division of Developmental Neurovirology, Department of Pediatrics, Johns Hopkins School of Medicine, Baltimore, MD 21287, USA.
| | - Y Li
- Stanley Division of Developmental Neurovirology, Department of Pediatrics, Johns Hopkins School of Medicine, Baltimore, MD 21287, USA; Department of Psychiatry, Renmin Hospital, Wuhan University, Wuhan, PR China
| | - E Prandovszky
- Stanley Division of Developmental Neurovirology, Department of Pediatrics, Johns Hopkins School of Medicine, Baltimore, MD 21287, USA
| | - S S Karuppagounder
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Department of Neurology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Adrienne Helis Malvin Medical Research Foundation, New Orleans, LA 70130-2685, USA
| | - C C Talbot
- Institute for Basic Biomedical Sciences, Johns Hopkins School of Medicine, Baltimore, MD 21287, USA
| | - V L Dawson
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Department of Neurology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Solomon H. Snyder Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Adrienne Helis Malvin Medical Research Foundation, New Orleans, LA 70130-2685, USA; Diana Helis Henry Medical Research Foundation, New Orleans, LA 70130-2685, USA
| | - T M Dawson
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Department of Neurology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Solomon H. Snyder Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Adrienne Helis Malvin Medical Research Foundation, New Orleans, LA 70130-2685, USA
| | - R H Yolken
- Stanley Division of Developmental Neurovirology, Department of Pediatrics, Johns Hopkins School of Medicine, Baltimore, MD 21287, USA
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Varadkar P, Despres D, Kraman M, Lozier J, Phadke A, Nagaraju K, Mccright B. The protein phosphatase 2A B56γ regulatory subunit is required for heart development. Dev Dyn 2014; 243:778-90. [PMID: 24425002 DOI: 10.1002/dvdy.24111] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Revised: 12/16/2013] [Accepted: 12/19/2013] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND Protein Phosphatase 2A (PP2A) function is controlled by regulatory subunits that modulate the activity of the catalytic subunit and direct the PP2A complex to specific intracellular locations. To study PP2A's role in signal transduction pathways that control growth and differentiation in vivo, a transgenic mouse lacking the B56γ regulatory subunit of PP2A was made. RESULTS Lack of PP2A activity specific to the PP2A-B56γ holoenzyme, resulted in the formation of an incomplete ventricular septum and a decrease in the number of ventricular cardiomyocytes. During cardiac development, B56γ is expressed in the nucleus of α-actinin-positive cardiomyocytes that contain Z-bands. The pattern of B56γ expression correlated with the cardiomyocyte apoptosis we observed in B56γ-deficient mice during mid to late gestation. In addition to the cardiac phenotypes, mice lacking B56γ have a decrease in locomotive coordination and gripping strength, indicating that B56γ has a role in controlling PP2A activity required for efficient neuromuscular function. CONCLUSIONS PP2A-B56γ activity is required for efficient cardiomyocyte maturation and survival. The PP2A B56γ regulatory subunit controls PP2A substrate specificity in vivo in a manner that cannot be fully compensated for by other B56 subunits.
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Affiliation(s)
- Prajakta Varadkar
- Division of Cellular and Gene Therapies, Center for Biologics Evaluation and Research, FDA, Bethesda, Maryland
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36
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Abstract
Protein phosphatase 2A (PP2A), one of the main serine-threonine phosphatases in mammalian cells, maintains cell homoeostasis by counteracting most of the kinase-driven intracellular signalling pathways. Unrestrained activation of oncogenic kinases together with inhibition of tumour suppressors is often required for development of cancer. PP2A has been shown to be genetically altered or functionally inactivated in many solid cancers and leukaemias, and is therefore a tumour suppressor. For example, the phosphatase activity of PP2A is suppressed in chronic myeloid leukaemia and other malignancies characterised by aberrant activity of oncogenic kinases. Preclinical studies show that pharmacological restoration of PP2A tumour-suppressor activity by PP2A-activating drugs (eg, FTY720) effectively antagonises cancer development and progression. Here, we discuss PP2A as a druggable tumour suppressor in view of the possible introduction of PP2A-activating drugs into anticancer therapeutic protocols.
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Affiliation(s)
- Danilo Perrotti
- Human Cancer Genetics Program, Department of Molecular Virology, Immunology, and Medical Genetics, and Comprehensive Cancer Center, Ohio State University, Columbus, OH 43210-2207, USA.
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37
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Kása A, Czikora I, Verin AD, Gergely P, Csortos C. Protein phosphatase 2A activity is required for functional adherent junctions in endothelial cells. Microvasc Res 2013; 89:86-94. [PMID: 23721711 DOI: 10.1016/j.mvr.2013.05.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Revised: 05/13/2013] [Accepted: 05/18/2013] [Indexed: 11/30/2022]
Abstract
Reversible Ser/Thr phosphorylation of cytoskeletal and adherent junction (AJ) proteins has a critical role in the regulation of endothelial cell (EC) barrier function. We have demonstrated earlier that protein phosphatase 2A (PP2A) activity is important in EC barrier integrity. In the present work, macro- and microvascular EC were examined and we provided further evidence on the significance of PP2A in the maintenance of EC cytoskeleton and barrier function with special focus on the Bα (regulatory) subunit of PP2A. Immunofluorescent staining revealed that the inhibition of PP2A results in changes in the organization of EC cytoskeleton as microtubule dissolution and actin re-arrangement were detected. Depletion of Bα regulatory subunit of PP2A had similar effect on the cytoskeleton structure of the cells. Furthermore, transendothelial electric resistance measurements demonstrated significantly slower barrier recovery of Bα depleted EC after thrombin treatment. AJ proteins, VE-cadherin and β-catenin, were detected along with Bα in pull-down assay. Also, the inhibition of PP2A (by okadaic acid or fostriecin) or depletion of Bα caused β-catenin translocation from the membrane to the cytoplasm in parallel with its phosphorylation on Ser552. In conclusion, our data suggest that the A/Bα/C holoenzyme form of PP2A is essential in EC barrier integrity both in micro- and macrovascular EC.
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Affiliation(s)
- Anita Kása
- Department of Medical Chemistry, University of Debrecen Medical and Health Science Center, Debrecen H-4032, Egyetem tér 1., Hungary
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Identification of transcriptional and phosphatase regulators as interaction partners of human ADA3, a component of histone acetyltransferase complexes. Biochem J 2013; 450:311-20. [PMID: 23167988 DOI: 10.1042/bj20120452] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
ADA (alteration/deficiency in activation) 3 is a conserved component of several transcriptional adaptor and HAT (histone acetyltransferase) complexes that regulate RNA polymerase II-mediated gene expression. Within the HAT complexes ADA3 is associated with ADA2 and the HAT GCN5 (general control non-repressed 5). ADA3 plays roles in diverse cellular processes and also in malignancies by modulating GCN5 catalytic activity and/or by interactions with other regulators. To gain a better understanding of ADA3 function, we used a yeast two-hybrid approach to screen a human fetal cDNA library for proteins that interacted with hADA3 (human ADA3). We identified three novel hADA3-interacting partners, a transcriptional regulator, AATF (apoptosis-antagonizing transcription factor), and regulatory subunits of the PP1 (protein phosphatase 1) and PP2A (protein phosphatase 2A) [PPP1R7 (PP1 regulatory subunit 7) and PPP2R5D (PP2A 56 kDa regulatory subunit δ isoform) respectively]. Analysis of truncated versions of hADA3 indicated that the C-terminal ADA2-interacting domain was not required for these interactions. Fluorescent microscopy analysis and co-immunoprecipitation provided support for the co-localization and interaction of hADA3 with these proteins in human cells. Expression of the interacting proteins altered expression of an hADA3-regulated reporter gene, suggesting functional consequences for the interactions. The detected interactions of hADA3 might extend the spectrum of mechanisms by which ADA3 can contribute to the regulation of gene expression and shed light on processes mediated by these newly identified ADA3 partners.
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Xu P, Raetz EA, Kitagawa M, Virshup DM, Lee SH. BUBR1 recruits PP2A via the B56 family of targeting subunits to promote chromosome congression. Biol Open 2013; 2:479-86. [PMID: 23789096 PMCID: PMC3654266 DOI: 10.1242/bio.20134051] [Citation(s) in RCA: 102] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Accepted: 02/26/2013] [Indexed: 02/01/2023] Open
Abstract
BUBR1 is a mitotic phosphoprotein essential for the maintenance of chromosome stability by promoting chromosome congression and proper kinetochore-microtubule (K-fiber) attachment, but the underlying mechanism(s) has remained elusive. Here we identify BUBR1 as a binding partner of the B56 family of Protein Phosphatase 2A regulatory subunits. The interaction between BUBR1 and the B56 family is required for chromosome congression, since point mutations in BUBR1 that block B56 binding abolish chromosome congression. The BUBR1:B56-PP2A complex opposes Aurora B kinase activity, since loss of the complex can be reverted by inhibiting Aurora B. Importantly, we show that the failure of BUBR1 to recruit B56-PP2A also contributes to the chromosome congression defects found in cells derived from patients with the Mosaic Variegated Aneuploidy (MVA) syndrome. Together, we propose that B56-PP2A is a key mediator of BUBR1's role in chromosome congression and functions by antagonizing Aurora B activity at the kinetochore for establishing stable kinetochore-microtubule attachment at the metaphase plate.
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Affiliation(s)
- Peng Xu
- Program in Cancer and Stem Cell Biology, Duke-NUS Graduate Medical School, 8 College Road , Singapore 169857 , Singapore ; NUS Graduate School for Integrative Sciences and Engineering , 28 Medical Drive Singapore 117456 , Singapore
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Fernández-Sánchez MT, Cabrera-García D, Ferrero-Gutierrez A, Pérez-Gómez A, Cruz PG, Daranas AH, Fernández JJ, Norte M, Novelli A. Comparative toxicological study of the novel protein phosphatase inhibitor 19-Epi-okadaic acid in primary cultures of rat cerebellar cells. Toxicol Sci 2013; 132:409-18. [PMID: 23335626 DOI: 10.1093/toxsci/kft006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Okadaic acid (OKA) and analogues are frequent contaminants of coastal waters and seafood. Structure analysis of the isolated OKA analogue 19-epi-OKA showed important conformation differences expected to result in lower protein phosphatase (PP) inhibitory potencies than OKA. However, 19-epi-OKA and OKA inhibitory activities versus PP2A were unexpectedly found to be virtually equipotent. To investigate the toxicological relevance of these findings, we tested the effects of 19-epi-OKA on cultured cerebellar cells and compared them with those of OKA and its isomer dinophysistoxin-2. 19-epi-OKA caused degeneration of neurites and neuronal death with much lower potency than its congeners. The concentration of 19-epi-OKA that reduced after 24h the maximum neuronal survival (EC5024) by 50% was ~300nM compared with ~2nM and ~8nM for OKA and dinophysistoxin-2, respectively. Exposure to 19-epi-OKA resulted also in less toxicity for cultured glial cells (EC5024,19-epi-OKA ~ 600nM; EC5024,OKA ~ 20nM). 19-epi-OKA induced apoptotic condensation and fragmentation of chromatin, activation of caspases, and activation of ERK1/2 MAP kinases, features previously reported for OKA and dinophysistoxin-2. Also, differential sensitivity to 19-epi-OKA was observed between neuronal and glial cells, a specific characteristic shared by OKA and dinophysistoxin-2 but not by other toxins. Our results are consistent with 19-epi-OKA being included among the group of toxins of OKA and derivatives and support the suitability of cellular bioassays for the detection of these compounds.
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Affiliation(s)
- Maria-Teresa Fernández-Sánchez
- Instituto Universitario de Biotecnología de Asturias, Departamento de Bioquímica y Biología Molecular, Universidad de Oviedo, Oviedo, Spain.
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Abstract
Protein phosphatases of the type 2A family (PP2A) represent a major fraction of cellular Ser/Thr phosphatase activity in any given human tissue. In this review, we describe how the holoenzymic nature of PP2A and the existence of several distinct PP2A composing subunits allow for the generation of multiple structurally and functionally different PP2A complexes, explaining why PP2A is involved in the regulation of so many diverse cell biological and physiological processes. Moreover, in human disease, most notably in several cancers and Alzheimer's Disease, PP2A expression and/or activity have been found significantly decreased, underscoring its important functions as a major tumor suppressor and tau phosphatase. Hence, several recent preclinical studies have demonstrated that pharmacological restoration of PP2A activity, as well as pharmacological PP2A inhibition, under certain conditions, may be of significant future therapeutic value.
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Activation of protein kinase C delta following cerebral ischemia leads to release of cytochrome C from the mitochondria via bad pathway. PLoS One 2011; 6:e22057. [PMID: 21789211 PMCID: PMC3137627 DOI: 10.1371/journal.pone.0022057] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Accepted: 06/14/2011] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND The release of cytochrome c from the mitochondria following cerebral ischemia is a key event leading to cell death. The goal of the present study was to determine the mechanisms involved in post-ischemic activation of protein kinase c delta (δPKC) that lead to cytochrome c release. METHODS/FINDINGS We used a rat model of cardiac arrest as an in vivo model, and an in vitro analog, oxygen glucose deprivation (OGD) in rat hippocampal synaptosomes. Cardiac arrest triggered translocation of δPKC to the mitochondrial fraction at 1 h reperfusion. In synaptosomes, the peptide inhibitor of δPKC blocked OGD-induced translocation to the mitochondria. We tested two potential pathways by which δPKC activation could lead to cytochrome c release: phosphorylation of phospholipid scramblase-3 (PLSCR3) and/or protein phosphatase 2A (PP2A). Cardiac arrest increased levels of phosphorlyated PLSCR3; however, inhibition of δPKC translocation failed to affect the OGD-induced increase in PLSCR3 in synaptosomal mitochondria suggesting the post-ischemic phosphorylation of PLSCR3 is not mediated by δPKC. Inhibition of either δPKC or PP2A decreased cytochrome c release from synaptosomal mitochondria. Cardiac arrest results in the dephosphorylation of Bad and Bax, both downstream targets of PP2A promoting apoptosis. Inhibition of δPKC or PP2A prevented OGD-induced Bad, but not Bax, dephosphorylation. To complement these studies, we used proteomics to identify novel mitochondrial substrates of δPKC. CONCLUSIONS We conclude that δPKC initiates cytochrome c release via phosphorylation of PP2A and subsequent dephosphorylation of Bad and identified δPKC, PP2A and additional mitochondrial proteins as potential therapeutic targets for ischemic neuroprotection.
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Low expression of PP2A regulatory subunit B55α is associated with T308 phosphorylation of AKT and shorter complete remission duration in acute myeloid leukemia patients. Leukemia 2011; 25:1711-7. [PMID: 21660042 PMCID: PMC3191228 DOI: 10.1038/leu.2011.146] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The regulation of Protein Kinase B (AKT) is a dynamic process that depends on the balance between phosphorylation by upstream kinases for activation and inactivation by dephosphorylation by protein phosphatases. Phosphorylated AKT is commonly found in acute myeloid leukemia (AML) and confers an unfavorable prognosis. Understanding the relative importance of upstream kinases and AKT phosphatase in the activation of AKT is relevant for the therapeutic targeting of this signaling axis in AML. The B55α subunit of Protein Phosphatase 2A (PP2A) has been implicated in AKT dephosphorylation but its role in regulating AKT in AML is unknown. We examined B55α protein expression in blast cells derived from 511 AML patients using Reverse Phase Protein Analysis (RPPA). B55α protein expression was lower in AML cells compared to normal CD34+ cells. B55α protein levels negatively correlated with T308 phosphorylation levels. Low levels of B55α were associated with shorter complete remission duration demonstrating that decreased expression is an adverse prognostic factor in AML. These findings suggest that decreased B55α expression in AML is at least partially responsible for increased AKT signaling in AML and suggests that therapeutic targeting of PP2A could counteract this.
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Cheong JK, Nguyen TH, Wang H, Tan P, Voorhoeve PM, Lee SH, Virshup DM. IC261 induces cell cycle arrest and apoptosis of human cancer cells via CK1δ/ɛ and Wnt/β-catenin independent inhibition of mitotic spindle formation. Oncogene 2011; 30:2558-69. [PMID: 21258417 PMCID: PMC3109269 DOI: 10.1038/onc.2010.627] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Casein kinase 1 delta and epsilon (CK1δ/ɛ) are key regulators of diverse cellular growth and survival processes including Wnt signaling, DNA repair and circadian rhythms. Recent studies suggest that they have an important role in oncogenesis. RNA interference screens identified CK1ɛ as a pro-survival factor in cancer cells in vitro and the CK1δ/ɛ-specific inhibitor IC261 is remarkably effective at selective, synthetic lethal killing of cancer cells. The recent development of the nanomolar CK1δ/ɛ-selective inhibitor, PF670462 (PF670) and the CK1ɛ-selective inhibitor PF4800567 (PF480) offers an opportunity to further test the role of CK1δ/ɛ in cancer. Unexpectedly, and unlike IC261, PF670 and PF480 were unable to induce cancer cell death. PF670 is a potent inhibitor of CK1δ/ɛ in cells; nanomolar concentrations are sufficient to inhibit CK1δ/ɛ activity as measured by repression of intramolecular autophosphorylation, phosphorylation of disheveled2 proteins and Wnt/β-catenin signaling. Likewise, small interfering RNA knockdown of CK1δ and CK1ɛ reduced Wnt/β-catenin signaling without affecting cell viability, further suggesting that CK1δ/ɛ inhibition may not be relevant to the IC261-induced cell death. Thus, while PF670 is a potent inhibitor of Wnt signaling, it only modestly inhibits cell proliferation. In contrast, while sub-micromolar concentrations of IC261 neither inhibited CK1δ/ɛ kinase activity nor blocked Wnt/β-catenin signaling in cancer cells, it caused a rapid induction of prometaphase arrest and subsequent apoptosis in multiple cancer cell lines. In a stepwise transformation model, IC261-induced killing required both overactive Ras and inactive p53. IC261 binds to tubulin with an affinity similar to colchicine and is a potent inhibitor of microtubule polymerization. This activity accounts for many of the diverse biological effects of IC261 and, most importantly, for its selective cancer cell killing.
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Affiliation(s)
- J K Cheong
- Cancer and Stem Cell Biology Program, Duke-NUS Graduate Medical School, Singapore
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Phosphorylation/dephosphorylation of human SULT4A1: Role of Erk1 and PP2A. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1813:231-7. [DOI: 10.1016/j.bbamcr.2010.09.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2010] [Revised: 09/17/2010] [Accepted: 09/21/2010] [Indexed: 01/19/2023]
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46
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Gharbi-Ayachi A, Labbé JC, Burgess A, Vigneron S, Strub JM, Brioudes E, Van-Dorsselaer A, Castro A, Lorca T. The substrate of Greatwall kinase, Arpp19, controls mitosis by inhibiting protein phosphatase 2A. Science 2010; 330:1673-1677. [PMID: 21164014 DOI: 10.1016/b978-0-12-374145-5.00168-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Initiation and maintenance of mitosis require the activation of protein kinase cyclin B-Cdc2 and the inhibition of protein phosphatase 2A (PP2A), which, respectively, phosphorylate and dephosphorylate mitotic substrates. The protein kinase Greatwall (Gwl) is required to maintain mitosis through PP2A inhibition. We describe how Gwl activation results in PP2A inhibition. We identified cyclic adenosine monophosphate-regulated phosphoprotein 19 (Arpp19) and α-Endosulfine as two substrates of Gwl that, when phosphorylated by this kinase, associate with and inhibit PP2A, thus promoting mitotic entry. Conversely, in the absence of Gwl activity, Arpp19 and α-Endosulfine are dephosphorylated and lose their capacity to bind and inhibit PP2A. Although both proteins can inhibit PP2A, endogenous Arpp19, but not α-Endosulfine, is responsible for PP2A inhibition at mitotic entry in Xenopus egg extracts.
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Affiliation(s)
- Aicha Gharbi-Ayachi
- Universités Montpellier 2 et 1, Centre de Recherche de Biochimie Macromoléculaire, CNRS UMR 5237, IFR 122, 1919 Route de Mende, 34293 Montpellier cedex 5, France
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47
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Kim JW, Jang SM, Kim CH, An JH, Kang EJ, Choi KH. Neural retina leucine-zipper regulates the expression of Ppp2r5c, the regulatory subunit of protein phosphatase 2A, in photoreceptor development. FEBS J 2010; 277:5051-60. [DOI: 10.1111/j.1742-4658.2010.07910.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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48
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Pitman MR, Barr RK, Gliddon BL, Magarey AM, Moretti PAB, Pitson SM. A critical role for the protein phosphatase 2A B'α regulatory subunit in dephosphorylation of sphingosine kinase 1. Int J Biochem Cell Biol 2010; 43:342-7. [PMID: 21075214 DOI: 10.1016/j.biocel.2010.11.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2010] [Revised: 10/20/2010] [Accepted: 11/05/2010] [Indexed: 12/15/2022]
Abstract
Sphingosine kinase 1 (SK1) is an important regulator of cellular signalling that has gained recent attention as a potential target for anti-cancer therapies. SK1 activity, subcellular localization and oncogenic function are regulated by phosphorylation and dephosphorylation at Ser225. ERK1/2 have been identified as the protein kinases responsible for phosphorylation and activation of SK1. Conversely, dephosphorylation and deactivation of SK1 occurs by protein phosphatase 2A (PP2A). Active PP2A, however, is a heterotrimer, composed of tightly associated catalytic and structural subunits that can interact with an array of regulatory subunits, which are critical for determining holoenzyme substrate specificity and subcellular localization. Thus, PP2A represents a large family of holoenzyme complexes with different activities and diverse substrate specificities. To date the regulatory subunit essential for targeting PP2A to SK1 has remained undefined. Here, we demonstrate a critical role for the B'α (B56α/PR61α/PPP2R5A) regulatory subunit of PP2A in SK1 dephosphorylation. B'α was found to interact with the c-terminus of SK1, and reduce SK1 phosphorylation when overexpressed, while having no effect on upstream ERK1/2 activation. siRNA-mediated knockdown of B'α increased SK1 phosphorylation, activity and membrane localization of endogenous SK1. Furthermore, overexpression of B'α blocked agonist-induced translocation of SK1 to the plasma membrane and abrogated SK1-induced neoplastic transformation of NIH3T3 fibroblasts. Thus, the PP2A-B'α holoenzyme appears to function as an important endogenous regulator of SK1.
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Affiliation(s)
- Melissa R Pitman
- Molecular Signalling Laboratory, Centre for Cancer Biology, SA Pathology, Frome Road, Adelaide, South Australia 5000, Australia
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Murgiano L, D’Alessandro A, Egidi MG, Crisà A, Prosperini G, Timperio AM, Valentini A, Zolla L. Proteomics and Transcriptomics Investigation on longissimus Muscles in Large White and Casertana Pig Breeds. J Proteome Res 2010; 9:6450-66. [DOI: 10.1021/pr100693h] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Leonardo Murgiano
- Dipartimento di Produzioni Animali, Università della Tuscia, Via de Lellis, 01100 Viterbo, Italy, and Dipartimento di Scienze Ambientali, Università della Tuscia, L.go dell’Università snc, 01100, Viterbo, Italy
| | - Angelo D’Alessandro
- Dipartimento di Produzioni Animali, Università della Tuscia, Via de Lellis, 01100 Viterbo, Italy, and Dipartimento di Scienze Ambientali, Università della Tuscia, L.go dell’Università snc, 01100, Viterbo, Italy
| | - Maria Giulia Egidi
- Dipartimento di Produzioni Animali, Università della Tuscia, Via de Lellis, 01100 Viterbo, Italy, and Dipartimento di Scienze Ambientali, Università della Tuscia, L.go dell’Università snc, 01100, Viterbo, Italy
| | - Alessandra Crisà
- Dipartimento di Produzioni Animali, Università della Tuscia, Via de Lellis, 01100 Viterbo, Italy, and Dipartimento di Scienze Ambientali, Università della Tuscia, L.go dell’Università snc, 01100, Viterbo, Italy
| | - Gianluca Prosperini
- Dipartimento di Produzioni Animali, Università della Tuscia, Via de Lellis, 01100 Viterbo, Italy, and Dipartimento di Scienze Ambientali, Università della Tuscia, L.go dell’Università snc, 01100, Viterbo, Italy
| | - Anna Maria Timperio
- Dipartimento di Produzioni Animali, Università della Tuscia, Via de Lellis, 01100 Viterbo, Italy, and Dipartimento di Scienze Ambientali, Università della Tuscia, L.go dell’Università snc, 01100, Viterbo, Italy
| | - Alessio Valentini
- Dipartimento di Produzioni Animali, Università della Tuscia, Via de Lellis, 01100 Viterbo, Italy, and Dipartimento di Scienze Ambientali, Università della Tuscia, L.go dell’Università snc, 01100, Viterbo, Italy
| | - Lello Zolla
- Dipartimento di Produzioni Animali, Università della Tuscia, Via de Lellis, 01100 Viterbo, Italy, and Dipartimento di Scienze Ambientali, Università della Tuscia, L.go dell’Università snc, 01100, Viterbo, Italy
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50
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Yang J, Phiel C. Functions of B56-containing PP2As in major developmental and cancer signaling pathways. Life Sci 2010; 87:659-66. [PMID: 20934435 DOI: 10.1016/j.lfs.2010.10.003] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2010] [Revised: 09/08/2010] [Accepted: 09/23/2010] [Indexed: 12/20/2022]
Abstract
Members of the B'/B56/PR61 family regulatory subunits of PP2A determine the subcellular localization, substrate specificity, and catalytic activity of PP2A in a wide range of biological processes. Here, we summarize the structure and intracellular localization of B56-containing PP2As and review functions of B56-containing PP2As in several major developmental/cancer signaling pathways.
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Affiliation(s)
- Jing Yang
- The Research Institute at Nationwide Children's Hospital, Department of Pediatrics, the Ohio State University, 700 Children's Dr., Columbus, OH, 43205, United States.
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