1
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Nadel G, Yao Z, Hacohen-Lev-Ran A, Wainstein E, Maik-Rachline G, Ziv T, Naor Z, Admon A, Seger R. Phosphorylation of PP2Ac by PKC is a key regulatory step in the PP2A-switch-dependent AKT dephosphorylation that leads to apoptosis. Cell Commun Signal 2024; 22:154. [PMID: 38419089 PMCID: PMC10900696 DOI: 10.1186/s12964-024-01536-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Accepted: 02/17/2024] [Indexed: 03/02/2024] Open
Abstract
BACKGROUND Although GqPCR activation often leads to cell survival by activating the PI3K/AKT pathway, it was previously shown that in several cell types AKT activity is reduced and leads to JNK activation and apoptosis. The mechanism of AKT inactivation in these cells involves an IGBP1-coupled PP2Ac switch that induces the dephosphorylation and inactivation of both PI3K and AKT. However, the machinery involved in the initiation of PP2A switch is not known. METHODS We used phospho-mass spectrometry to identify the phosphorylation site of PP2Ac, and raised specific antibodies to follow the regulation of this phosphorylation. Other phosphorylations were monitored by commercial antibodies. In addition, we used coimmunoprecipitation and proximity ligation assays to follow protein-protein interactions. Apoptosis was detected by a TUNEL assay as well as PARP1 cleavage using SDS-PAGE and Western blotting. RESULTS We identified Ser24 as a phosphorylation site in PP2Ac. The phosphorylation is mediated mainly by classical PKCs (PKCα and PKCβ) but not by novel PKCs (PKCδ and PKCε). By replacing the phosphorylated residue with either unphosphorylatable or phosphomimetic residues (S24A and S24E), we found that this phosphorylation event is necessary and sufficient to mediate the PP2A switch, which ultimately induces AKT inactivation, and a robust JNK-dependent apoptosis. CONCLUSION Our results show that the PP2A switch is induced by PKC-mediated phosphorylation of Ser24-PP2Ac and that this phosphorylation leads to apoptosis upon GqPCR induction of various cells. We propose that this mechanism may provide an unexpected way to treat some cancer types or problems in the endocrine machinery.
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Affiliation(s)
- Guy Nadel
- Department of Immunology and Regenerative Biology, the Weizmann Institute of Science, Rehovot, Israel
| | - Zhong Yao
- Department of Immunology and Regenerative Biology, the Weizmann Institute of Science, Rehovot, Israel
| | - Avital Hacohen-Lev-Ran
- Department of Immunology and Regenerative Biology, the Weizmann Institute of Science, Rehovot, Israel
| | - Ehud Wainstein
- Department of Immunology and Regenerative Biology, the Weizmann Institute of Science, Rehovot, Israel
| | - Galia Maik-Rachline
- Department of Immunology and Regenerative Biology, the Weizmann Institute of Science, Rehovot, Israel
| | - Tamar Ziv
- Smoler Proteomic Center, Technion-Israel Institute of Technology, Haifa, Israel
| | - Zvi Naor
- Department of Biochemistry and Molecular Biology, Tel Aviv University, Tel Aviv, Israel
| | - Arie Admon
- Faculty of Biology, Technion-Israel Institute of Technology, Haifa, Israel
| | - Rony Seger
- Department of Immunology and Regenerative Biology, the Weizmann Institute of Science, Rehovot, Israel.
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2
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Kolesnikov AV, Luu J, Jin H, Palczewski K, Kefalov VJ. Deletion of Protein Phosphatase 2A Accelerates Retinal Degeneration in GRK1- and Arr1-Deficient Mice. Invest Ophthalmol Vis Sci 2022; 63:18. [PMID: 35861670 PMCID: PMC9315073 DOI: 10.1167/iovs.63.8.18] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose Light detection in retinal rod photoreceptors is initiated by activation of the visual pigment rhodopsin. A critical, yet often-overlooked, step enabling efficient perception of light is rhodopsin dephosphorylation mediated by protein phosphatase 2A (PP2A). PP2A deficiency has been reported to impair rhodopsin regeneration after phosphorylation by G protein receptor kinase 1 (GRK1) and binding of arrestin (Arr1), thereby delaying rod dark adaptation. However, its effects on the viability of photoreceptors in the absence of GRK1 and Arr1 remain unclear. Here, we investigated the effects of PP2A deficiency in the absence of GRK1 or Arr1, both of which have been implicated in Oguchi disease, a form of night blindness. Methods Rod-specific mice lacking the predominant catalytic Cα-subunit of PP2A were crossed with the Grk1−/− or Arr1−/− strains to obtain double knockout lines. Rod photoreceptor viability was analyzed in histological cross-sections of the retina stained with hematoxylin and eosin, and rod function was evaluated by ex vivo electroretinography. Results PP2A deficiency alone did not impair photoreceptor viability up to 12 months of age. Retinal degeneration was more pronounced in rods lacking GRK1 compared to rods lacking Arr1, and degeneration was accelerated in both Grk1−/− or Arr1−/− strains where PP2A was also deleted. In Arr1−/− mice, rod maximal photoresponse amplitudes were reduced by 80% at 3 months, and this diminution was enhanced further with concomitant PP2A deficiency. Conclusions These results suggest that although PP2A is not required for the survival of rods, its deletion accelerates the degeneration induced by the absence of either GRK1 or Arr1.
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Affiliation(s)
- Alexander V Kolesnikov
- Gavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine, California, United States
| | - Jennings Luu
- Gavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine, California, United States.,Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio, United States
| | - Hui Jin
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio, United States
| | - Krzysztof Palczewski
- Gavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine, California, United States.,Department of Physiology & Biophysics, University of California, Irvine, California, United States.,Department of Chemistry, University of California, Irvine, California, United States.,Department of Molecular Biology and Biochemistry, University of California, Irvine, California, United States
| | - Vladimir J Kefalov
- Gavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine, California, United States.,Department of Physiology & Biophysics, University of California, Irvine, California, United States
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3
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Haslem L, Hays JM, Hays FA. p66Shc in Cardiovascular Pathology. Cells 2022; 11:cells11111855. [PMID: 35681549 PMCID: PMC9180016 DOI: 10.3390/cells11111855] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Revised: 05/30/2022] [Accepted: 06/01/2022] [Indexed: 02/06/2023] Open
Abstract
p66Shc is a widely expressed protein that governs a variety of cardiovascular pathologies by generating, and exacerbating, pro-apoptotic ROS signals. Here, we review p66Shc’s connections to reactive oxygen species, expression, localization, and discuss p66Shc signaling and mitochondrial functions. Emphasis is placed on recent p66Shc mitochondrial function discoveries including structure/function relationships, ROS identity and regulation, mechanistic insights, and how p66Shc-cyt c interactions can influence p66Shc mitochondrial function. Based on recent findings, a new p66Shc mitochondrial function model is also put forth wherein p66Shc acts as a rheostat that can promote or antagonize apoptosis. A discussion of how the revised p66Shc model fits previous findings in p66Shc-mediated cardiovascular pathology follows.
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Affiliation(s)
- Landon Haslem
- Biochemistry and Molecular Biology Department, College of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (L.H.); (J.M.H.)
| | - Jennifer M. Hays
- Biochemistry and Molecular Biology Department, College of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (L.H.); (J.M.H.)
| | - Franklin A. Hays
- Biochemistry and Molecular Biology Department, College of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (L.H.); (J.M.H.)
- Stephenson Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
- Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
- Correspondence:
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4
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Pluteanu F, Boknik P, Heinick A, König C, Müller FU, Weidlich A, Kirchhefer U. Activation of PKC results in improved contractile effects and Ca cycling by inhibition of PP2A-B56α. Am J Physiol Heart Circ Physiol 2022; 322:H427-H441. [PMID: 35119335 DOI: 10.1152/ajpheart.00539.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Protein phosphatase 2A (PP2A) represents a heterotrimer that is responsible for the dephosphorylation of important regulatory myocardial proteins. The present study was aimed to test whether the phosphorylation of PP2A-B56α at Ser41 by PKC is involved in the regulation of myocyte Ca2+ cycling and contraction. For this purpose, heart preparations of wild-type (WT) and transgenic mice overexpressing the non-phosphorylatable S41A mutant form (TG) were stimulated by administration of the direct PKC activator phorbol 12-myristate 13-acetate (PMA), and functional effects were studied. PKC activation was accompanied by the inhibition of PP2A activity in WT cardiomyocytes, whereas this effect was absent in TG. Consistently, the increase in the sarcomere length shortening and the peak amplitude of Ca2+ transients after PMA administration in WT cardiomyocytes was attenuated in TG. However, the co-stimulation with 1 µM isoprenaline was able to offset these functional deficits. Moreover, TG hearts did not show an increase in the phosphorylation of the myosin-binding protein C after administration of PMA but was detected in corresponding WT. PMA modulated voltage-dependent activation of the L-type Ca2+ channel (LTCC) differently in the two genotypes, shifting V1/2a by +1.5 mV in TG and by 2.4 mV in WT. In the presence of PMA, ICaL inactivation remained unchanged in TG, whereas it was slower in corresponding WT. Our data suggest that PKC-activated enhancement of myocyte contraction and intracellular Ca2+ signaling is mediated by phosphorylation of B56α at Ser41, leading to a decrease in PP2A activity.
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Affiliation(s)
- Florentina Pluteanu
- Department of Anatomy, Animal Physiology and Biophysics, University of Bucharest, Bucharest, Romania
| | - Peter Boknik
- Institute of Pharmacology and Toxicology, University of Münster, Münster, Germany
| | - Alexander Heinick
- Institute of Pharmacology and Toxicology, University of Münster, Münster, Germany
| | - Christiane König
- Institute of Pharmacology and Toxicology, University of Münster, Münster, Germany
| | - Frank U Müller
- Institute of Pharmacology and Toxicology, University of Münster, Münster, Germany
| | - Adam Weidlich
- 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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5
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Nadel G, Yao Z, Wainstein E, Cohen I, Ben-Ami I, Schajnovitz A, Maik-Rachline G, Naor Z, Horwitz BA, Seger R. GqPCR-stimulated dephosphorylation of AKT is induced by an IGBP1-mediated PP2A switch. Cell Commun Signal 2022; 20:5. [PMID: 34998390 PMCID: PMC8742922 DOI: 10.1186/s12964-021-00805-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 11/18/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND G protein-coupled receptors (GPCRs) usually regulate cellular processes via activation of intracellular signaling pathways. However, we have previously shown that in several cell lines, GqPCRs induce immediate inactivation of the AKT pathway, which leads to JNK-dependent apoptosis. This apoptosis-inducing AKT inactivation is essential for physiological functions of several GqPCRs, including those for PGF2α and GnRH. METHODS Here we used kinase activity assays of PI3K and followed phosphorylation state of proteins using specific antibodies. In addition, we used coimmunoprecipitation and proximity ligation assays to follow protein-protein interactions. Apoptosis was detected by TUNEL assay and PARP1 cleavage. RESULTS We identified the mechanism that allows the unique stimulated inactivation of AKT and show that the main regulator of this process is the phosphatase PP2A, operating with the non-canonical regulatory subunit IGBP1. In resting cells, an IGBP1-PP2Ac dimer binds to PI3K, dephosphorylates the inhibitory pSer608-p85 of PI3K and thus maintains its high basal activity. Upon GqPCR activation, the PP2Ac-IGBP1 dimer detaches from PI3K and thus allows the inhibitory dephosphorylation. At this stage, the free PP2Ac together with IGBP1 and PP2Aa binds to AKT, causing its dephosphorylation and inactivation. CONCLUSION Our results show a stimulated shift of PP2Ac from PI3K to AKT termed "PP2A switch" that represses the PI3K/AKT pathway, providing a unique mechanism of GPCR-stimulated dephosphorylation. Video Abstract.
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Affiliation(s)
- Guy Nadel
- Departments of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel
| | - Zhong Yao
- Departments of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel
| | - Ehud Wainstein
- Departments of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel
| | - Izel Cohen
- Departments of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel
| | - Ido Ben-Ami
- Departments of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel.,IVF and Fertility Unit, Department of OB/GYN, Shaare Zedek Medical Center and The Hebrew University Medical School, Jerusalem, Israel
| | - Amir Schajnovitz
- Departments of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel
| | - Galia Maik-Rachline
- Departments of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel
| | - Zvi Naor
- Department of Biochemistry and Molecular Biology, Tel Aviv University, Tel Aviv, Israel
| | - Benjamin A Horwitz
- Departments of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel.,Faculty of Biology, Technion-Israel Institute of Technology, Haifa, Israel
| | - Rony Seger
- Departments of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel.
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6
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Sergienko NM, Donner DG, Delbridge LMD, McMullen JR, Weeks KL. Protein phosphatase 2A in the healthy and failing heart: New insights and therapeutic opportunities. Cell Signal 2021; 91:110213. [PMID: 34902541 DOI: 10.1016/j.cellsig.2021.110213] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 12/02/2021] [Accepted: 12/07/2021] [Indexed: 02/06/2023]
Abstract
Protein phosphatases have emerged as critical regulators of phosphoprotein homeostasis in settings of health and disease. Protein phosphatase 2A (PP2A) encompasses a large subfamily of enzymes that remove phosphate groups from serine/threonine residues within phosphoproteins. The heterogeneity in PP2A structure, which arises from the grouping of different catalytic, scaffolding and regulatory subunit isoforms, creates distinct populations of catalytically active enzymes (i.e. holoenzymes) that localise to different parts of the cell. This structural complexity, combined with other regulatory mechanisms, such as interaction of PP2A heterotrimers with accessory proteins and post-translational modification of the catalytic and/or regulatory subunits, enables PP2A holoenzymes to target phosphoprotein substrates in a highly specific manner. In this review, we summarise the roles of PP2A in cardiac physiology and disease. PP2A modulates numerous processes that are vital for heart function including calcium handling, contractility, β-adrenergic signalling, metabolism and transcription. Dysregulation of PP2A has been observed in human cardiac disease settings, including heart failure and atrial fibrillation. Efforts are underway, particularly in the cancer field, to develop therapeutics targeting PP2A activity. The development of small molecule activators of PP2A (SMAPs) and other compounds that selectively target specific PP2A holoenzymes (e.g. PP2A/B56α and PP2A/B56ε) will improve understanding of the function of different PP2A species in the heart, and may lead to the development of therapeutics for normalising aberrant protein phosphorylation in settings of cardiac remodelling and dysfunction.
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Affiliation(s)
- Nicola M Sergienko
- Baker Heart and Diabetes Institute, Melbourne VIC 3004, Australia; Central Clinical School, Monash University, Clayton VIC 3800, Australia
| | - Daniel G Donner
- Baker Heart and Diabetes Institute, Melbourne VIC 3004, Australia; Baker Department of Cardiometabolic Health, The University of Melbourne, Parkville VIC 3010, Australia
| | - Lea M D Delbridge
- Department of Anatomy and Physiology, The University of Melbourne, Parkville VIC 3010, Australia
| | - Julie R McMullen
- Baker Heart and Diabetes Institute, Melbourne VIC 3004, Australia; Baker Department of Cardiometabolic Health, The University of Melbourne, Parkville VIC 3010, Australia; Department of Physiology and Department of Medicine Alfred Hospital, Monash University, Clayton VIC 3800, Australia; Department of Physiology, Anatomy and Microbiology, La Trobe University, Bundoora VIC 3086, Australia; Department of Diabetes, Central Clinical School, Monash University, Clayton VIC 3800, Australia.
| | - Kate L Weeks
- Baker Heart and Diabetes Institute, Melbourne VIC 3004, Australia; Department of Anatomy and Physiology, The University of Melbourne, Parkville VIC 3010, Australia; Baker Department of Cardiometabolic Health, The University of Melbourne, Parkville VIC 3010, Australia; Department of Diabetes, Central Clinical School, Monash University, Clayton VIC 3800, Australia.
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7
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Du M, Yuan L, Zhang Z, Zhang C, Zhu M, Zhang Z, Li R, Zhao X, Liang H, Li Y, Jiang H, Qiao J, Yin Y. PPP2R1B is modulated by ubiquitination and is essential for spermatogenesis. FASEB J 2021; 35:e21564. [PMID: 33913576 DOI: 10.1096/fj.202002810r] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 03/05/2021] [Accepted: 03/16/2021] [Indexed: 01/20/2023]
Abstract
The serine-threonine protein phosphatase 2A (PP2A) is a heterotrimeric enzyme complex that regulates many fundamental cellular processes. PP2A is involved in tumorigenesis because mutations in the scaffold subunit, PPP2R1B, were found in several types of cancers. However, the biological function of PPP2R1B remains largely unknown. We report here that homozygous deletion of Ppp2r1b in Mus musculus impairs meiotic recombination and causes meiotic arrest in spermatocytes. Consistently, male mice lacking Ppp2r1b are characterized with infertility. Furthermore, heterozygous missense mutations in the Homo sapiens PPP2R1B gene, which encodes PPP2R1B, are identified in azoospermia patients with meiotic arrest. We found that PPP2R1B mutants are susceptible to degradation by an E3 ligase CRL4ADCAF6 , and resistant to de-polyubiquitylation by ubiquitin-specific protease 5 (USP5). In addition, heterozygous mutations in PPP2R1B reduce stability of the wild-type PPP2R1B. Our results demonstrate an essential role of PPP2R1B in spermatogenesis and identify upstream regulators of PPP2R1B.
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Affiliation(s)
- Mufeng Du
- Institute of Systems Biomedicine, Department of Pathology, School of Basic Medical Sciences, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Peking University Health Science Center, Beijing, China
| | - Lin Yuan
- Institute of Systems Biomedicine, Department of Pathology, School of Basic Medical Sciences, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Peking University Health Science Center, Beijing, China.,Institute of Precision Medicine, Peking University Shenzhen Hospital, Shenzhen, China
| | - Zhong Zhang
- Institute of Systems Biomedicine, Department of Pathology, School of Basic Medical Sciences, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Peking University Health Science Center, Beijing, China
| | - Cong Zhang
- Institute of Systems Biomedicine, Department of Pathology, School of Basic Medical Sciences, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Peking University Health Science Center, Beijing, China
| | - Minglu Zhu
- Institute of Systems Biomedicine, Department of Pathology, School of Basic Medical Sciences, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Peking University Health Science Center, Beijing, China
| | - Zhe Zhang
- Depatment of Urology, Peking University Third Hospital, Beijing, China
| | - Ridong Li
- Institute of Systems Biomedicine, Department of Pathology, School of Basic Medical Sciences, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Peking University Health Science Center, Beijing, China
| | - Xuyang Zhao
- Institute of Systems Biomedicine, Department of Pathology, School of Basic Medical Sciences, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Peking University Health Science Center, Beijing, China
| | - Hui Liang
- Institute of Systems Biomedicine, Department of Pathology, School of Basic Medical Sciences, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Peking University Health Science Center, Beijing, China
| | - Yuhua Li
- Institute of Systems Biomedicine, Department of Pathology, School of Basic Medical Sciences, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Peking University Health Science Center, Beijing, China
| | - Hui Jiang
- Depatment of Urology, Peking University Third Hospital, Beijing, China
| | - Jie Qiao
- Department of Obstetrics and Gynecology, Center for Reproductive Medicine, Peking University Third Hospital, Beijing, China
| | - Yuxin Yin
- Institute of Systems Biomedicine, Department of Pathology, School of Basic Medical Sciences, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Peking University Health Science Center, Beijing, China.,Institute of Precision Medicine, Peking University Shenzhen Hospital, Shenzhen, China
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8
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Protein Phosphatase 2A (PP2A) mutations in brain function, development, and neurologic disease. Biochem Soc Trans 2021; 49:1567-1588. [PMID: 34241636 DOI: 10.1042/bst20201313] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Revised: 06/09/2021] [Accepted: 06/11/2021] [Indexed: 12/15/2022]
Abstract
By removing Ser/Thr-specific phosphorylations in a multitude of protein substrates in diverse tissues, Protein Phosphatase type 2A (PP2A) enzymes play essential regulatory roles in cellular signalling and physiology, including in brain function and development. Here, we review current knowledge on PP2A gene mutations causally involved in neurodevelopmental disorders and intellectual disability, focusing on PPP2CA, PPP2R1A and PPP2R5D. We provide insights into the impact of these mutations on PP2A structure, substrate specificity and potential function in neurobiology and brain development.
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9
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Zheng H, Qi Y, Hu S, Cao X, Xu C, Yin Z, Chen X, Li Y, Liu W, Li J, Wang J, Wei G, Liang K, Chen FX, Xu Y. Identification of Integrator-PP2A complex (INTAC), an RNA polymerase II phosphatase. Science 2020; 370:370/6520/eabb5872. [DOI: 10.1126/science.abb5872] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 07/09/2020] [Accepted: 09/23/2020] [Indexed: 12/12/2022]
Affiliation(s)
- Hai Zheng
- Fudan University Shanghai Cancer Center, Institutes of Biomedical Sciences, State Key Laboratory of Genetic Engineering and Shanghai Key Laboratory of Medical Epigenetics, Shanghai Medical College of Fudan University, Shanghai 200032, China
- The International Co-laboratory of Medical Epigenetics and Metabolism, Ministry of Science and Technology, China, Department of Systems Biology for Medicine, School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai 200032, China
| | - Yilun Qi
- Fudan University Shanghai Cancer Center, Institutes of Biomedical Sciences, State Key Laboratory of Genetic Engineering and Shanghai Key Laboratory of Medical Epigenetics, Shanghai Medical College of Fudan University, Shanghai 200032, China
| | - Shibin Hu
- Fudan University Shanghai Cancer Center, Institutes of Biomedical Sciences, State Key Laboratory of Genetic Engineering and Shanghai Key Laboratory of Medical Epigenetics, Shanghai Medical College of Fudan University, Shanghai 200032, China
| | - Xuan Cao
- CAS Key Laboratory of Computational Biology, CAS-MPG Partner Institute for Computational Biology, Shanghai Institute of Nutrition and Health, Shanghai Institutes for Biological Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Congling Xu
- Fudan University Shanghai Cancer Center, Institutes of Biomedical Sciences, State Key Laboratory of Genetic Engineering and Shanghai Key Laboratory of Medical Epigenetics, Shanghai Medical College of Fudan University, Shanghai 200032, China
| | - Zhinang Yin
- Department of Pathophysiology, School of Basic Medical Sciences, Wuhan University, Wuhan 430071, China
| | - Xizi Chen
- Fudan University Shanghai Cancer Center, Institutes of Biomedical Sciences, State Key Laboratory of Genetic Engineering and Shanghai Key Laboratory of Medical Epigenetics, Shanghai Medical College of Fudan University, Shanghai 200032, China
| | - Yan Li
- Fudan University Shanghai Cancer Center, Institutes of Biomedical Sciences, State Key Laboratory of Genetic Engineering and Shanghai Key Laboratory of Medical Epigenetics, Shanghai Medical College of Fudan University, Shanghai 200032, China
| | - Weida Liu
- Fudan University Shanghai Cancer Center, Institutes of Biomedical Sciences, State Key Laboratory of Genetic Engineering and Shanghai Key Laboratory of Medical Epigenetics, Shanghai Medical College of Fudan University, Shanghai 200032, China
| | - Jie Li
- Fudan University Shanghai Cancer Center, Institutes of Biomedical Sciences, State Key Laboratory of Genetic Engineering and Shanghai Key Laboratory of Medical Epigenetics, Shanghai Medical College of Fudan University, Shanghai 200032, China
| | - Jiawei Wang
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, 100084 Beijing, China
| | - Gang Wei
- CAS Key Laboratory of Computational Biology, CAS-MPG Partner Institute for Computational Biology, Shanghai Institute of Nutrition and Health, Shanghai Institutes for Biological Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Kaiwei Liang
- Department of Pathophysiology, School of Basic Medical Sciences, Wuhan University, Wuhan 430071, China
| | - Fei Xavier Chen
- Fudan University Shanghai Cancer Center, Institutes of Biomedical Sciences, State Key Laboratory of Genetic Engineering and Shanghai Key Laboratory of Medical Epigenetics, Shanghai Medical College of Fudan University, Shanghai 200032, China
| | - Yanhui Xu
- Fudan University Shanghai Cancer Center, Institutes of Biomedical Sciences, State Key Laboratory of Genetic Engineering and Shanghai Key Laboratory of Medical Epigenetics, Shanghai Medical College of Fudan University, Shanghai 200032, China
- The International Co-laboratory of Medical Epigenetics and Metabolism, Ministry of Science and Technology, China, Department of Systems Biology for Medicine, School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai 200032, China
- Human Phenome Institute, Collaborative Innovation Center of Genetics and Development, School of Life Sciences, Fudan University, Shanghai 200433, China
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10
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Qadri M, ElSayed S, Elsaid KA. Fingolimod Phosphate (FTY720-P) Activates Protein Phosphatase 2A in Human Monocytes and Inhibits Monosodium Urate Crystal-Induced Interleukin-1 β Production. J Pharmacol Exp Ther 2020; 376:222-230. [PMID: 33239408 DOI: 10.1124/jpet.120.000321] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Accepted: 11/20/2020] [Indexed: 12/27/2022] Open
Abstract
Gout is a chronic inflammatory arthritis caused by monosodium urate monohydrate (MSU) crystal deposits in joints of lower limbs. Phagocytic uptake of MSU crystals by joint-resident macrophages and recruited circulating monocytes results in IL-1β expression and production. Current acute gout treatments have serious toxicities and suffer suboptimal clinical outcomes. Protein phosphatase 2A (PP2A) plays an important role in regulating signaling pathways relevant to inflammation. We hypothesized that innate immune danger signals, e.g., lipopolysaccharide (LPS) and soluble uric acid (sUA), prime human monocytes toward MSU crystal phagocytosis and that increased IL-1β production mediated by a reduction in PP2A activity and restoring PP2A activity exerts an anti-inflammatory effect in this setting. Priming monocytes with LPS + sUA increased cytosolic pro-IL-1β and mature IL-1β and enhanced MSU crystal phagocytosis and its downstream IL-1β expression (P < 0.001). A combination of LPS + sUA priming and MSU crystals reduced PP2A activity in monocytes by 60% (P = 0.013). PP2A catalytic subunit gene knockdown reduced PP2A activity and exacerbated MSU crystal-induced IL-1β expression and secretion (P < 0.0001). Fingolimod (FTY720) and its active metabolite, fingolimod phosphate (FTY720-P), were evaluated for their ability to activate PP2A in human monocytes over 24 hours. FTY720 and FTY720-P activated PP2A to a similar extent, and maximal enzyme activity occurred at 24 hours for FTY720 and at 6 hours for FTY720-P. FTY720-P (2.5 μM) reduced pro-IL-1β production and IL-1β secretion in primed and MSU crystal-stimulated monocytes (P < 0.0001) without changing the magnitude of crystal phagocytosis. We conclude that PP2A is a promising new target in acute gout. SIGNIFICANCE STATEMENT: The activity of protein phosphatase 2A (PP2A) is implicated in the enhanced expression and production of IL-1β by human monocytes in response to priming with soluble uric acid and lipopolysaccharide and phagocytosis of monosodium urate monohydrate (MSU) crystals. Fingolimod phosphate activates PP2A in human monocytes and reduces cytosolic pro-IL-1β content and its conversion to biologically active IL-1β in human monocytes exposed to MSU crystals.
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Affiliation(s)
- Marwa Qadri
- Department of Pharmacology, College of Pharmacy, Jazan University, Jazan, Kingdom of Saudi Arabia (M.Q.) and Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Rinker Health Sciences Campus, Irvine, California (S.E., K.A.E.)
| | - Sandy ElSayed
- Department of Pharmacology, College of Pharmacy, Jazan University, Jazan, Kingdom of Saudi Arabia (M.Q.) and Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Rinker Health Sciences Campus, Irvine, California (S.E., K.A.E.)
| | - Khaled A Elsaid
- Department of Pharmacology, College of Pharmacy, Jazan University, Jazan, Kingdom of Saudi Arabia (M.Q.) and Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Rinker Health Sciences Campus, Irvine, California (S.E., K.A.E.)
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11
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Quinlan MA, Robson MJ, Ye R, Rose KL, Schey KL, Blakely RD. Ex vivo Quantitative Proteomic Analysis of Serotonin Transporter Interactome: Network Impact of the SERT Ala56 Coding Variant. Front Mol Neurosci 2020; 13:89. [PMID: 32581705 PMCID: PMC7295033 DOI: 10.3389/fnmol.2020.00089] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Accepted: 04/28/2020] [Indexed: 12/15/2022] Open
Abstract
Altered serotonin (5-HT) signaling is associated with multiple brain disorders, including major depressive disorder (MDD), obsessive-compulsive disorder (OCD), and autism spectrum disorder (ASD). The presynaptic, high-affinity 5-HT transporter (SERT) tightly regulates 5-HT clearance after release from serotonergic neurons in the brain and enteric nervous systems, among other sites. Accumulating evidence suggests that SERT is dynamically regulated in distinct activity states as a result of environmental and intracellular stimuli, with regulation perturbed by disease-associated coding variants. Our lab identified a rare, hypermorphic SERT coding substitution, Gly56Ala, in subjects with ASD, finding that the Ala56 variant stabilizes a high-affinity outward-facing conformation (SERT∗) that leads to elevated 5-HT uptake in vitro and in vivo. Hyperactive SERT Ala56 appears to preclude further activity enhancements by p38α mitogen-activated protein kinase (MAPK) and can be normalized by pharmacological p38α MAPK inhibition, consistent with SERT Ala56 mimicking, constitutively, a high-activity conformation entered into transiently by p38α MAPK activation. We hypothesize that changes in SERT-interacting proteins (SIPs) support the shift of SERT into the SERT∗ state which may be captured by comparing the composition of SERT Ala56 protein complexes with those of wildtype (WT) SERT, defining specific interactions through comparisons of protein complexes recovered using preparations from SERT–/– (knockout; KO) mice. Using quantitative proteomic-based approaches, we identify a total of 459 SIPs, that demonstrate both SERT specificity and sensitivity to the Gly56Ala substitution, with a striking bias being a loss of SIP interactions with SERT Ala56 compared to WT SERT. Among this group are previously validated SIPs, such as flotillin-1 (FLOT1) and protein phosphatase 2A (PP2A), whose functions are believed to contribute to SERT microdomain localization and regulation. Interestingly, our studies nominate a number of novel SIPs implicated in ASD, including fragile X mental retardation 1 protein (FMR1) and SH3 and multiple ankyrin repeat domains protein 3 (SHANK3), of potential relevance to long-standing evidence of serotonergic contributions to ASD. Further investigation of these SIPs, and the broader networks they engage, may afford a greater understanding of ASD as well as other brain and peripheral disorders associated with perturbed 5-HT signaling.
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Affiliation(s)
- Meagan A Quinlan
- Department of Psychiatry and Behavioral Sciences, University of Washington, Seattle, WA, United States.,Department of Pharmacology, Vanderbilt University, Nashville, TN, United States.,Department of Biomedical Science, Charles E. Schmidt College of Medicine, Florida Atlantic University, Jupiter, FL, United States
| | - Matthew J Robson
- Division of Pharmaceutical Sciences, James L. Winkle College of Pharmacy, University of Cincinnati, Cincinnati, OH, United States
| | - Ran Ye
- Department of Pharmacology, Vanderbilt University, Nashville, TN, United States
| | - Kristie L Rose
- Department of Biochemistry, Vanderbilt University, Nashville, TN, United States
| | - Kevin L Schey
- Department of Biochemistry, Vanderbilt University, Nashville, TN, United States
| | - Randy D Blakely
- Department of Pharmacology, Vanderbilt University, Nashville, TN, United States.,Brain Institute, Florida Atlantic University, Jupiter, FL, United States
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12
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Keating L, Touati SA, Wassmann K. A PP2A-B56-Centered View on Metaphase-to-Anaphase Transition in Mouse Oocyte Meiosis I. Cells 2020; 9:E390. [PMID: 32046180 PMCID: PMC7072534 DOI: 10.3390/cells9020390] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Revised: 02/04/2020] [Accepted: 02/05/2020] [Indexed: 12/12/2022] Open
Abstract
Meiosis is required to reduce to haploid the diploid genome content of a cell, generating gametes-oocytes and sperm-with the correct number of chromosomes. To achieve this goal, two specialized cell divisions without intermediate S-phase are executed in a time-controlled manner. In mammalian female meiosis, these divisions are error-prone. Human oocytes have an exceptionally high error rate that further increases with age, with significant consequences for human fertility. To understand why errors in chromosome segregation occur at such high rates in oocytes, it is essential to understand the molecular players at work controlling these divisions. In this review, we look at the interplay of kinase and phosphatase activities at the transition from metaphase-to-anaphase for correct segregation of chromosomes. We focus on the activity of PP2A-B56, a key phosphatase for anaphase onset in both mitosis and meiosis. We start by introducing multiple roles PP2A-B56 occupies for progression through mitosis, before laying out whether or not the same principles may apply to the first meiotic division in oocytes, and describing the known meiosis-specific roles of PP2A-B56 and discrepancies with mitotic cell cycle regulation.
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Affiliation(s)
- Leonor Keating
- Mammalian Oocyte Meiosis (MOM) UMR7622, Institut de Biologie Paris Seine, Sorbonne Université, 75005 Paris, France; (L.K.); (S.A.T.)
- CNRS UMR7622 Developmental Biology Lab, Sorbonne Université, 75005 Paris, France
| | - Sandra A. Touati
- Mammalian Oocyte Meiosis (MOM) UMR7622, Institut de Biologie Paris Seine, Sorbonne Université, 75005 Paris, France; (L.K.); (S.A.T.)
- CNRS UMR7622 Developmental Biology Lab, Sorbonne Université, 75005 Paris, France
| | - Katja Wassmann
- Mammalian Oocyte Meiosis (MOM) UMR7622, Institut de Biologie Paris Seine, Sorbonne Université, 75005 Paris, France; (L.K.); (S.A.T.)
- CNRS UMR7622 Developmental Biology Lab, Sorbonne Université, 75005 Paris, France
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13
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Brautigan DL, Shenolikar S. Protein Serine/Threonine Phosphatases: Keys to Unlocking Regulators and Substrates. Annu Rev Biochem 2019; 87:921-964. [PMID: 29925267 DOI: 10.1146/annurev-biochem-062917-012332] [Citation(s) in RCA: 110] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Protein serine/threonine phosphatases (PPPs) are ancient enzymes, with distinct types conserved across eukaryotic evolution. PPPs are segregated into types primarily on the basis of the unique interactions of PPP catalytic subunits with regulatory proteins. The resulting holoenzymes dock substrates distal to the active site to enhance specificity. This review focuses on the subunit and substrate interactions for PPP that depend on short linear motifs. Insights about these motifs from structures of holoenzymes open new opportunities for computational biology approaches to elucidate PPP networks. There is an expanding knowledge base of posttranslational modifications of PPP catalytic and regulatory subunits, as well as of their substrates, including phosphorylation, acetylation, and ubiquitination. Cross talk between these posttranslational modifications creates PPP-based signaling. Knowledge of PPP complexes, signaling clusters, as well as how PPPs communicate with each other in response to cellular signals should unlock the doors to PPP networks and signaling "clouds" that orchestrate and coordinate different aspects of cell physiology.
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Affiliation(s)
- David L Brautigan
- Center for Cell Signaling and Department of Microbiology, Immunology and Cancer Biology, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA;
| | - Shirish Shenolikar
- Signature Research Programs in Cardiovascular and Metabolic Disorders and Neuroscience and Behavioral Disorders, Duke-NUS Medical School, Singapore 169857
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14
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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: 30] [Impact Index Per Article: 6.0] [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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15
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Moura M, Conde C. Phosphatases in Mitosis: Roles and Regulation. Biomolecules 2019; 9:E55. [PMID: 30736436 PMCID: PMC6406801 DOI: 10.3390/biom9020055] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Revised: 01/31/2019] [Accepted: 02/01/2019] [Indexed: 02/07/2023] Open
Abstract
Mitosis requires extensive rearrangement of cellular architecture and of subcellular structures so that replicated chromosomes can bind correctly to spindle microtubules and segregate towards opposite poles. This process originates two new daughter nuclei with equal genetic content and relies on highly-dynamic and tightly regulated phosphorylation of numerous cell cycle proteins. A burst in protein phosphorylation orchestrated by several conserved kinases occurs as cells go into and progress through mitosis. The opposing dephosphorylation events are catalyzed by a small set of protein phosphatases, whose importance for the accuracy of mitosis is becoming increasingly appreciated. This review will focus on the established and emerging roles of mitotic phosphatases, describe their structural and biochemical properties, and discuss recent advances in understanding the regulation of phosphatase activity and function.
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Affiliation(s)
- Margarida Moura
- IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135 Porto, Portugal.
- i3S-Instituto de Investigação e Inovação em Saúde da Universidade do Porto, 4200-135, Porto, Portugal.
- Programa Doutoral em Biologia Molecular e Celular (MCbiology), Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto, 4050-313 Porto, Portugal.
| | - Carlos Conde
- IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135 Porto, Portugal.
- i3S-Instituto de Investigação e Inovação em Saúde da Universidade do Porto, 4200-135, Porto, Portugal.
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16
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Physiologic functions of PP2A: Lessons from genetically modified mice. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1866:31-50. [DOI: 10.1016/j.bbamcr.2018.07.010] [Citation(s) in RCA: 71] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Revised: 07/11/2018] [Accepted: 07/14/2018] [Indexed: 01/03/2023]
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17
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Lai D, Chen M, Su J, Liu X, Rothe K, Hu K, Forrest DL, Eaves CJ, Morin GB, Jiang X. PP2A inhibition sensitizes cancer stem cells to ABL tyrosine kinase inhibitors in BCR-ABL
+
human leukemia. Sci Transl Med 2018; 10. [DOI: 10.1126/scitranslmed.aan8735] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/30/2023]
Abstract
PP2A inhibitors and BCR-ABL inhibitors synergize to kill drug-insensitive leukemia cells.
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Affiliation(s)
- Damian Lai
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, British Columbia V5Z 1L3, Canada
- Department of Medicine, University of British Columbia, Vancouver, British Columbia V5Z 1M9, Canada
| | - Min Chen
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, British Columbia V5Z 1L3, Canada
| | - Jiechuang Su
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, British Columbia V5Z 1L3, Canada
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia V6H 3N1, Canada
| | - Xiaohu Liu
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, British Columbia V5Z 1L3, Canada
- Department of Medicine, University of British Columbia, Vancouver, British Columbia V5Z 1M9, Canada
| | - Katharina Rothe
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, British Columbia V5Z 1L3, Canada
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia V6H 3N1, Canada
| | - Kaiji Hu
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, British Columbia V5Z 1L3, Canada
| | - Donna L. Forrest
- Department of Medicine, University of British Columbia, Vancouver, British Columbia V5Z 1M9, Canada
- Leukemia/Bone Marrow Transplant Program of British Columbia, Vancouver, British Columbia V5Z 1M9, Canada
| | - Connie J. Eaves
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, British Columbia V5Z 1L3, Canada
- Department of Medicine, University of British Columbia, Vancouver, British Columbia V5Z 1M9, Canada
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia V6H 3N1, Canada
| | - Gregg B. Morin
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia V6H 3N1, Canada
- Michael Smith Genome Sciences Centre, British Columbia Cancer Agency, Vancouver, British Columbia V5Z 1L3, Canada
| | - Xiaoyan Jiang
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, British Columbia V5Z 1L3, Canada
- Department of Medicine, University of British Columbia, Vancouver, British Columbia V5Z 1M9, Canada
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia V6H 3N1, Canada
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18
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Rajala A, Wang Y, Abcouwer SF, Gardner TW, Rajala RV. Developmental and light regulation of tumor suppressor protein PP2A in the retina. Oncotarget 2018; 9:1505-1523. [PMID: 29416710 PMCID: PMC5788578 DOI: 10.18632/oncotarget.23351] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Accepted: 11/28/2017] [Indexed: 02/07/2023] Open
Abstract
Protein phosphatases are a group of universal enzymes that are responsible for the dephosphorylation of various proteins and enzymes in cells. Cellular signal transduction events are largely governed by the phosphorylation of key proteins. The length of cellular response depends on the activation of protein phosphatase that dephosphorylates the phosphate groups to halt a biological response, and fine-tune the defined cellular outcome. Dysregulation of these phosphatase(s) results in various disease phenotypes. The retina is a post-mitotic tissue, and oncogenic tyrosine and serine/ threonine kinase activities are important for retinal neuron survival. Aberrant activation of protein phosphatase(s) may have a negative effect on retinal neurons. In the current study, we characterized tumor suppressor protein phosphatase 2 (PP2A), a major serine/ threonine kinase with a broad substrate specificity. Our data suggest that PP2A is developmentally regulated in the retina, localized predominantly in the inner retina, and expressed in photoreceptor inner segments. Our findings indicate that PKCα and mTOR may serve as PP2A substrates. We found that light regulates PP2A activity. Our studies also suggest that rhodopsin regulates PP2A and its substrate(s) dephosphorylation. PP2A substrate phosphorylation is increased in mice lacking the A-subunit of PP2A. However, there is no accompanying effect on retina structure and function. Together, our findings suggest that controlling the activity of PP2A in the retina may be neuroprotective.
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Affiliation(s)
- Ammaji Rajala
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
- Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
| | - Yuhong Wang
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
- Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
| | - Steven F. Abcouwer
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, USA
- W.K. Kellogg Eye Center, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Thomas W. Gardner
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, USA
- W.K. Kellogg Eye Center, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Raju V.S. Rajala
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
- Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
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19
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Eleftheriadou O, Boguslavskyi A, Longman MR, Cowan J, Francois A, Heads RJ, Wadzinski BE, Ryan A, Shattock MJ, Snabaitis AK. Expression and regulation of type 2A protein phosphatases and alpha4 signalling in cardiac health and hypertrophy. Basic Res Cardiol 2017; 112:37. [PMID: 28526910 PMCID: PMC5438423 DOI: 10.1007/s00395-017-0625-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Accepted: 05/02/2017] [Indexed: 01/25/2023]
Abstract
Cardiac physiology and hypertrophy are regulated by the phosphorylation status of many proteins, which is partly controlled by a poorly defined type 2A protein phosphatase-alpha4 intracellular signalling axis. Quantitative PCR analysis revealed that mRNA levels of the type 2A catalytic subunits were differentially expressed in H9c2 cardiomyocytes (PP2ACβ > PP2ACα > PP4C > PP6C), NRVM (PP2ACβ > PP2ACα = PP4C = PP6C), and adult rat ventricular myocytes (PP2ACα > PP2ACβ > PP6C > PP4C). Western analysis confirmed that all type 2A catalytic subunits were expressed in H9c2 cardiomyocytes; however, PP4C protein was absent in adult myocytes and only detectable following 26S proteasome inhibition. Short-term knockdown of alpha4 protein expression attenuated expression of all type 2A catalytic subunits. Pressure overload-induced left ventricular (LV) hypertrophy was associated with an increase in both PP2AC and alpha4 protein expression. Although PP6C expression was unchanged, expression of PP6C regulatory subunits (1) Sit4-associated protein 1 (SAP1) and (2) ankyrin repeat domain (ANKRD) 28 and 44 proteins was elevated, whereas SAP2 expression was reduced in hypertrophied LV tissue. Co-immunoprecipitation studies demonstrated that the interaction between alpha4 and PP2AC or PP6C subunits was either unchanged or reduced in hypertrophied LV tissue, respectively. Phosphorylation status of phospholemman (Ser63 and Ser68) was significantly increased by knockdown of PP2ACα, PP2ACβ, or PP4C protein expression. DNA damage assessed by histone H2A.X phosphorylation (γH2A.X) in hypertrophied tissue remained unchanged. However, exposure of cardiomyocytes to H2O2 increased levels of γH2A.X which was unaffected by knockdown of PP6C expression, but was abolished by the short-term knockdown of alpha4 expression. This study illustrates the significance and altered activity of the type 2A protein phosphatase-alpha4 complex in healthy and hypertrophied myocardium.
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Affiliation(s)
- Olga Eleftheriadou
- School of Life Sciences, Pharmacy and Chemistry, Faculty of Science Engineering and Computing, Kingston University, Penrhyn Road, Kingston-upon-Thames, Surrey, KT1 2EE, UK
| | - Andrii Boguslavskyi
- Cardiovascular Division, King's College London British Heart Foundation Centre, The Rayne Institute, St Thomas' Hospital, London, SE1 7EH, UK
| | - Michael R Longman
- School of Life Sciences, Pharmacy and Chemistry, Faculty of Science Engineering and Computing, Kingston University, Penrhyn Road, Kingston-upon-Thames, Surrey, KT1 2EE, UK
| | - Jonathan Cowan
- School of Life Sciences, Pharmacy and Chemistry, Faculty of Science Engineering and Computing, Kingston University, Penrhyn Road, Kingston-upon-Thames, Surrey, KT1 2EE, UK
| | - Asvi Francois
- Cardiovascular Division, King's College London British Heart Foundation Centre, The Rayne Institute, St Thomas' Hospital, London, SE1 7EH, UK
| | - Richard J Heads
- Cardiovascular Division, King's College London British Heart Foundation Centre, The Rayne Institute, St Thomas' Hospital, London, SE1 7EH, UK
| | - Brian E Wadzinski
- Department of Pharmacology, Vanderbilt University, Nashville, TN, USA
| | - Ali Ryan
- School of Life Sciences, Pharmacy and Chemistry, Faculty of Science Engineering and Computing, Kingston University, Penrhyn Road, Kingston-upon-Thames, Surrey, KT1 2EE, UK
| | - Michael J Shattock
- Cardiovascular Division, King's College London British Heart Foundation Centre, The Rayne Institute, St Thomas' Hospital, London, SE1 7EH, UK
| | - Andrew K Snabaitis
- School of Life Sciences, Pharmacy and Chemistry, Faculty of Science Engineering and Computing, Kingston University, Penrhyn Road, Kingston-upon-Thames, Surrey, KT1 2EE, UK.
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20
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Regulation of protein phosphatase 2A (PP2A) tumor suppressor function by PME-1. Biochem Soc Trans 2016; 44:1683-1693. [DOI: 10.1042/bst20160161] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Revised: 08/06/2016] [Accepted: 09/09/2016] [Indexed: 02/06/2023]
Abstract
Protein phosphatase 2A (PP2A) plays a major role in maintaining cellular signaling homeostasis by dephosphorylation of a variety of signaling proteins and acts as a tumor suppressor. Protein phosphatase methylesterase-1 (PME-1) negatively regulates PP2A activity by highly complex mechanisms that are reviewed here. Importantly, recent studies have shown that PME-1 promotes oncogenic MAPK/ERK and AKT pathway activities in various cancer types. In human glioma, high PME-1 expression correlates with tumor progression and kinase inhibitor resistance. We discuss the emerging cancer-associated function of PME-1 and its potential clinical relevance.
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21
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A subset of RAB proteins modulates PP2A phosphatase activity. Sci Rep 2016; 6:32857. [PMID: 27611305 PMCID: PMC5017145 DOI: 10.1038/srep32857] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Accepted: 08/16/2016] [Indexed: 02/06/2023] Open
Abstract
Protein phosphatase 2A (PP2A) is one of the most abundant serine-threonine phosphatases in mammalian cells. PP2A is a hetero-trimeric holoenzyme participating in a variety of physiological processes whose deregulation is often associated to cancer. The specificity and activity of this phosphatase is tightly modulated by a family of regulatory B subunits that dock the catalytic subunit to the substrates. Here we characterize a novel and unconventional molecular mechanism controlling the activity of the tumor suppressor PP2A. By applying a mass spectrometry-based interactomics approach, we identified novel PP2A interacting proteins. Unexpectedly we found that a significant number of RAB proteins associate with the PP2A scaffold subunit (PPP2R1A), but not with the catalytic subunit (PPP2CA). Such interactions occur in vitro and in vivo in specific subcellular compartments. Notably we demonstrated that one of these RAB proteins, RAB9, competes with the catalytic subunit PPP2CA in binding to PPP2R1A. This competitive association has an important role in controlling the PP2A catalytic activity, which is compromised in several solid tumors and leukemias.
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22
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Raynes R, Juarez C, Pomatto LCD, Sieburth D, Davies KJA. Aging and SKN-1-dependent Loss of 20S Proteasome Adaptation to Oxidative Stress in C. elegans. J Gerontol A Biol Sci Med Sci 2016; 72:143-151. [PMID: 27341854 DOI: 10.1093/gerona/glw093] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2016] [Accepted: 05/03/2016] [Indexed: 01/01/2023] Open
Abstract
Aging is marked by a collapse of protein homeostasis and deterioration of adaptive stress responses that often lead to disease. During aging, the induction of stress responses decline along with protein quality control. Here, we have shown that the ability to mount an adaptive response by pretreatment with minor oxidative stress is abrogated in aged Caenorhabditis elegans We have identified a defect in SKN-1 signaling sensitivity during aging and have also found an aging-related increase in basal proteasome expression and in vitro activity, however, adaptation of the 20S proteasome in response to stress is lost in old animals. Interestingly, increased activation of SKN-1 promotes stress resistance, but is unable to rescue declining adaptation during aging. Our data demonstrate that the aging-dependent decline in SKN-1 signaling negatively impacts adaptation of the 20S proteasome in response to acute oxidative stress.
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Affiliation(s)
| | | | | | - Derek Sieburth
- Zilkha Neurogenetic Institute, Keck School of Medicine, and
| | - Kelvin J A Davies
- Leonard Davis School of Gerontology, .,Division of Molecular and Computational Biology, Department of Biological Sciences of the Dornsife College of Letters, Arts, and Sciences, University of Southern California, Los Angeles
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Yabe R, Miura A, Usui T, Mudrak I, Ogris E, Ohama T, Sato K. Protein Phosphatase Methyl-Esterase PME-1 Protects Protein Phosphatase 2A from Ubiquitin/Proteasome Degradation. PLoS One 2015; 10:e0145226. [PMID: 26678046 PMCID: PMC4683032 DOI: 10.1371/journal.pone.0145226] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Accepted: 12/01/2015] [Indexed: 11/30/2022] Open
Abstract
Protein phosphatase 2A (PP2A) is a conserved essential enzyme that is implicated as a tumor suppressor based on its central role in phosphorylation-dependent signaling pathways. Protein phosphatase methyl esterase (PME-1) catalyzes specifically the demethylation of the C-terminal Leu309 residue of PP2A catalytic subunit (PP2Ac). It has been shown that PME-1 affects the activity of PP2A by demethylating PP2Ac, but also by directly binding to the phosphatase active site, suggesting loss of PME-1 in cells would enhance PP2A activity. However, here we show that PME-1 knockout mouse embryonic fibroblasts (MEFs) exhibit lower PP2A activity than wild type MEFs. Loss of PME-1 enhanced poly-ubiquitination of PP2Ac and shortened the half-life of PP2Ac protein resulting in reduced PP2Ac levels. Chemical inhibition of PME-1 and rescue experiments with wild type and mutated PME-1 revealed methyl-esterase activity was necessary to maintain PP2Ac protein levels. Our data demonstrate that PME-1 methyl-esterase activity protects PP2Ac from ubiquitin/proteasome degradation.
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Affiliation(s)
- Ryotaro Yabe
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, 753–8515, Japan
| | - Akane Miura
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, 753–8515, Japan
| | - Tatsuya Usui
- Laboratory of Veterinary Toxicology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, 753–8515, Japan
| | - Ingrid Mudrak
- Department of Medical Biochemistry, Max F. Perutz Laboratories, Medical University of Vienna, Vienna, 1030, Austria
| | - Egon Ogris
- Department of Medical Biochemistry, Max F. Perutz Laboratories, Medical University of Vienna, Vienna, 1030, Austria
| | - Takashi Ohama
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, 753–8515, Japan
- * E-mail:
| | - Koichi Sato
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, 753–8515, Japan
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24
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Oaks J, Ogretmen B. Regulation of PP2A by Sphingolipid Metabolism and Signaling. Front Oncol 2015; 4:388. [PMID: 25642418 PMCID: PMC4295541 DOI: 10.3389/fonc.2014.00388] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 12/27/2014] [Indexed: 12/21/2022] Open
Abstract
Protein phosphatase 2A (PP2A) is a serine/threonine phosphatase that is a primary regulator of cellular proliferation through targeting of proliferative kinases, cell cycle regulators, and apoptosis inhibitors. It is through the regulation of these regulatory elements that gives PP2A tumor suppressor functions. In addition to mutations on the regulatory subunits, the phosphatase/tumor suppressing activity of PP2A is also inhibited in several cancer types due to overexpression or modification of the endogenous PP2A inhibitors such as SET/I2PP2A. This review focuses on the current literature regarding the interactions between the lipid signaling molecules, selectively sphingolipids, and the PP2A inhibitor SET for the regulation of PP2A, and the therapeutic potential of sphingolipids as PP2A activators for tumor suppression via targeting SET oncoprotein.
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Affiliation(s)
- Joshua Oaks
- Department of Biochemistry and Molecular Biology, Hollings Cancer Center, Medical University of South Carolina , Charleston, SC , USA
| | - Besim Ogretmen
- Department of Biochemistry and Molecular Biology, Hollings Cancer Center, Medical University of South Carolina , Charleston, SC , USA
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25
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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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Haesen D, Sents W, Lemaire K, Hoorne Y, Janssens V. The Basic Biology of PP2A in Hematologic Cells and Malignancies. Front Oncol 2014; 4:347. [PMID: 25566494 PMCID: PMC4263090 DOI: 10.3389/fonc.2014.00347] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 11/20/2014] [Indexed: 12/30/2022] Open
Abstract
Reversible protein phosphorylation plays a crucial role in regulating cell signaling. In normal cells, phosphoregulation is tightly controlled by a network of protein kinases counterbalanced by several protein phosphatases. Deregulation of this delicate balance is widely recognized as a central mechanism by which cells escape external and internal self-limiting signals, eventually resulting in malignant transformation. A large fraction of hematologic malignancies is characterized by constitutive or unrestrained activation of oncogenic kinases. This is in part achieved by activating mutations, chromosomal rearrangements, or constitutive activation of upstream kinase regulators, in part by inactivation of their anti-oncogenic phosphatase counterparts. Protein phosphatase 2A (PP2A) represents a large family of cellular serine/threonine phosphatases with suspected tumor suppressive functions. In this review, we highlight our current knowledge about the complex structure and biology of these phosphatases in hematologic cells, thereby providing the rationale behind their diverse signaling functions. Eventually, this basic knowledge is a key to truly understand the tumor suppressive role of PP2A in leukemogenesis and to allow further rational development of therapeutic strategies targeting PP2A.
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Affiliation(s)
- Dorien Haesen
- Laboratory of Protein Phosphorylation and Proteomics, Department Cellular and Molecular Medicine, University of Leuven , Leuven , Belgium
| | - Ward Sents
- Laboratory of Protein Phosphorylation and Proteomics, Department Cellular and Molecular Medicine, University of Leuven , Leuven , Belgium
| | - Katleen Lemaire
- Gene Expression Unit, Department Cellular and Molecular Medicine, University of Leuven , Leuven , Belgium
| | - Yana Hoorne
- Laboratory of Protein Phosphorylation and Proteomics, Department Cellular and Molecular Medicine, University of Leuven , Leuven , Belgium
| | - Veerle Janssens
- Laboratory of Protein Phosphorylation and Proteomics, Department Cellular and Molecular Medicine, University of Leuven , Leuven , Belgium
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27
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Du H, Wu K, Didoronkute A, Levy MVA, Todi N, Shchelokova A, Massiah MA. MID1 catalyzes the ubiquitination of protein phosphatase 2A and mutations within its Bbox1 domain disrupt polyubiquitination of alpha4 but not of PP2Ac. PLoS One 2014; 9:e107428. [PMID: 25207814 PMCID: PMC4160256 DOI: 10.1371/journal.pone.0107428] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2014] [Accepted: 08/14/2014] [Indexed: 01/05/2023] Open
Abstract
MID1 is a microtubule-associated protein that belongs to the TRIM family. MID1 functions as an ubiquitin E3 ligase, and recently was shown to catalyze the polyubiquitination of, alpha4, a protein regulator of protein phosphatase 2A (PP2A). It has been hypothesized that MID1 regulates PP2A, requiring the intermediary interaction with alpha4. Here we report that MID1 catalyzes the in vitro ubiquitination of the catalytic subunit of PP2A (PP2Ac) in the absence of alpha4. In the presence of alpha4, the level of PP2Ac ubiquitination is reduced. Using the MID1 RING-Bbox1-Bbox2 (RB1B2) construct containing the E3 ligase domains, we investigate the functional effects of mutations within the Bbox domains that are identified in patients with X-linked Opitz G syndrome (XLOS). The RB1B2 proteins harboring the C142S, C145T, A130V/T mutations within the Bbox1 domain and C195F mutation within the Bbox2 domain maintain auto-polyubiquitination activity. Qualitatively, the RB1B2 proteins containing these mutations are able to catalyze the ubiquitination of PP2Ac. In contrast, the RB1B2 proteins with mutations within the Bbox1 domain are unable to catalyze the polyubiquitination of alpha4. These results suggest that unregulated alpha4 may be the direct consequence of these natural mutations in the Bbox1 domain of MID1, and hence alpha4 could play a greater role to account for the increased amount of PP2A observed in XLOS-derived fibroblasts.
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Affiliation(s)
- Haijuan Du
- Department of Chemistry, George Washington University, Washington, District of Columbia, United States of America
| | - Kuanlin Wu
- Department of Chemistry, George Washington University, Washington, District of Columbia, United States of America
| | - Alma Didoronkute
- Department of Chemistry, George Washington University, Washington, District of Columbia, United States of America
| | - Marcus V. A. Levy
- Department of Chemistry, George Washington University, Washington, District of Columbia, United States of America
| | - Nimish Todi
- Department of Chemistry, George Washington University, Washington, District of Columbia, United States of America
| | - Anna Shchelokova
- Department of Chemistry, George Washington University, Washington, District of Columbia, United States of America
| | - Michael A. Massiah
- Department of Chemistry, George Washington University, Washington, District of Columbia, United States of America
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28
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Hu MW, Wang ZB, Jiang ZZ, Qi ST, Huang L, Liang QX, Schatten H, Sun QY. Scaffold subunit Aalpha of PP2A is essential for female meiosis and fertility in mice. Biol Reprod 2014; 91:19. [PMID: 24899574 DOI: 10.1095/biolreprod.114.120220] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Ppp2r1a encodes the scaffold subunit Aalpha of protein phosphatase 2A (PP2A), which is an important and ubiquitously expressed serine threonine phosphatase family and plays a critical role in many fundamental cellular processes. To identify the physiological role of PP2A in female germ cell meiosis, we selectively disrupted Ppp2r1a expression in oocytes by using the Cre-Loxp conditional knockout system. Here we report for the first time that oocyte-specific deletion of Ppp2r1a led to severe female subfertility without affecting follicle survival, growth, and ovulation. PP2A-Aalpha was essential for regulating oocyte meiotic maturation because depletion of PP2A-Aalpha facilitated germinal vesicle breakdown, causing elongation of the MII spindle and precocious separation of sister chromatids. The resulting eggs had high risk of aneuploidy, though they could be fertilized, leading to defective embryonic development and thus subfertility. Our findings provide strong evidence that PP2A-Aalpha within the oocyte plays an indispensable role in oocyte meiotic maturation, though it is dispensable for folliculogenesis in the mouse ovary.
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Affiliation(s)
- Meng-Wen Hu
- State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China University of Chinese Academy of Sciences, Beijing, China
| | - Zhen-Bo Wang
- State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Zong-Zhe Jiang
- State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China University of Chinese Academy of Sciences, Beijing, China
| | - Shu-Tao Qi
- State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Lin Huang
- State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Qiu-Xia Liang
- State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China University of Chinese Academy of Sciences, Beijing, China
| | - Heide Schatten
- Department of Veterinary Pathobiology, University of Missouri, Columbia, Missouri
| | - Qing-Yuan Sun
- State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
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29
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Bernal M, Zhurinsky J, Iglesias-Romero AB, Sanchez-Romero MA, Flor-Parra I, Tomas-Gallardo L, Perez-Pulido AJ, Jimenez J, Daga RR. Proteome-wide search for PP2A substrates in fission yeast. Proteomics 2014; 14:1367-80. [PMID: 24634168 DOI: 10.1002/pmic.201300136] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2013] [Revised: 02/19/2014] [Accepted: 03/07/2014] [Indexed: 11/10/2022]
Abstract
PP2A (protein phosphatase 2A) is a major phosphatase in eukaryotic cells that plays an essential role in many processes. PP2A mutations in Schizosaccharomyces pombe result in defects of cell cycle control, cytokinesis and morphogenesis. Which PP2A substrates are responsible for these changes is not known. In this work, we searched for PP2A substrates in S. pombe using two approaches, 2D-DIGE analysis of PP2A complex mutants and identification of PP2A interacting proteins. In both cases, we used MS to identify proteins of interest. In the DIGE experiment, we compared proteomes of wild-type S. pombe, deletion of pta2, the phosphoactivator of the PP2A catalytic subunit, and pab1-4, a mutant of B-type PP2A regulatory subunit. A total of 1742 protein spots were reproducibly resolved by 2D-DIGE and 51 spots demonstrated significant changes between PP2A mutants and the wild-type control. MS analysis of these spots identified 27 proteins that include key regulators of glycerol synthesis, carbon metabolism, amino acid biosyntesis, vitamin production, and protein folding. Importantly, we independently identified a subset of these proteins as PP2A binding partners by affinity precipitation, suggesting they may be direct targets of PP2A. We have validated our approach by demonstrating that phosphorylation of Gpd1, a key enzyme in glycerol biogenesis, is regulated by PP2A and that ability of cells to respond to osmotic stress by synthesizing glycerol is compromised in the PP2A mutants. Our work contributes to a better understanding of PP2A function and identifies potential PP2A substrates.
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Affiliation(s)
- Manuel Bernal
- Centro Andaluz de Biología del Desarrollo, Universidad Pablo de Olavide-Consejo Superior de Investigaciones Científicas, Junta de Andalucía, Sevilla, Spain
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30
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Longman MR, Ranieri A, Avkiran M, Snabaitis AK. Regulation of PP2AC carboxylmethylation and cellular localisation by inhibitory class G-protein coupled receptors in cardiomyocytes. PLoS One 2014; 9:e86234. [PMID: 24475092 PMCID: PMC3903491 DOI: 10.1371/journal.pone.0086234] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Accepted: 12/09/2013] [Indexed: 12/25/2022] Open
Abstract
The enzymatic activity of the type 2A protein phosphatase (PP2A) holoenzyme, a major serine/threonine phosphatase in the heart, is conferred by its catalytic subunit (PP2AC). PP2AC activity and subcellular localisation can be regulated by reversible carboxylmethylation of its C-terminal leucine309 (leu309) residue. Previous studies have shown that the stimulation of adenosine type 1 receptors (A1.Rs) induces PP2AC carboxylmethylation and altered subcellular distribution in adult rat ventricular myocytes (ARVM). In the current study, we show that the enzymatic components that regulate the carboxylmethylation status of PP2AC, leucine carboxylmethyltransferase-1 (LCMT-1) and phosphatase methylesterase-1 (PME-1) are abundantly expressed in, and almost entirely localised in the cytoplasm of ARVM. The stimulation of Gi-coupled A1.Rs with N6-cyclopentyladenosine (CPA), and of other Gi-coupled receptors such as muscarinic M2 receptors (stimulated with carbachol) and angiotensin II AT2 receptors (stimulated with CGP42112) in ARVM, induced PP2AC carboxylmethylation at leu309 in a concentration-dependent manner. Exposure of ARVM to 10 µM CPA increased the cellular association between PP2AC and its methyltransferase LCMT-1, but not its esterase PME-1. Stimulation of A1.Rs with 10 µM CPA increased the phosphorylation of protein kinase B at ser473, which was abolished by the PI3K inhibitor LY294002 (20 µM), thereby confirming that PI3K activity is upregulated in response to A1.R stimulation by CPA in ARVM. A1.R-induced PP2AC translocation to the particulate fraction was abrogated by adenoviral expression of the alpha subunit (Gαt1) coupled to the transducin G-protein coupled receptor. A similar inhibitory effect on A1.R-induced PP2AC translocation was also seen with LY294002 (20 µM). These data suggest that in ARVM, A1.R-induced PP2AC translocation to the particulate fraction occurs through a GiPCR-Gβγ-PI3K mediated intracellular signalling pathway, which may involve elevated PP2AC carboxylmethylation at leu309.
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Affiliation(s)
- Michael R. Longman
- School of Pharmacy and Chemistry, Faculty of Science, Engineering and Computing, Kingston University, Kingston-upon-Thames, Surrey, United Kingdom
| | - Antonella Ranieri
- King's College London British Heart Foundation Centre, Cardiovascular Division, The Rayne Institute, St Thomas' Hospital, London, United Kingdom
| | - Metin Avkiran
- King's College London British Heart Foundation Centre, Cardiovascular Division, The Rayne Institute, St Thomas' Hospital, London, United Kingdom
| | - Andrew K. Snabaitis
- School of Pharmacy and Chemistry, Faculty of Science, Engineering and Computing, Kingston University, Kingston-upon-Thames, Surrey, United Kingdom
- King's College London British Heart Foundation Centre, Cardiovascular Division, The Rayne Institute, St Thomas' Hospital, London, United Kingdom
- * E-mail:
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Impaired expression of protein phosphatase 2A subunits enhances metastatic potential of human prostate cancer cells through activation of AKT pathway. Br J Cancer 2013; 108:2590-600. [PMID: 23598299 PMCID: PMC3694226 DOI: 10.1038/bjc.2013.160] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Background: Protein phosphatase 2A (PP2A) is a dephosphorylating enzyme, loss of which can contribute to prostate cancer (PCa) pathogenesis. The aim of this study was to analyse the transcriptional and translational expression patterns of individual subunits of the PP2A holoenzyme during PCa progression. Methods: Immunohistochemistry (IHC), western blot, and real-time PCR was performed on androgen-dependent (AD) and androgen-independent (AI) PCa cells, and benign and malignant prostate tissues for all the three PP2A (scaffold, regulatory, and catalytic) subunits. Mechanistic and functional studies were performed using various biochemical and cellular techniques. Results: Through immunohistochemical analysis we observed significantly reduced levels of PP2A-A and -B′γ subunits (P<0.001 and P=0.0002) in PCa specimens compared with benign prostate. Contemporarily, there was no significant difference in PP2A-C subunit expression between benign and malignant tissues. Similar to the expression pattern observed in tissues, the endogenous levels of PP2A-A and B′γ subunits were abrogated from the low metastatic to high metastatic and AD to AI cell line models, without any change in the catalytic subunit expression. Furthermore, using in vitro studies we demonstrated that PP2A-Aα scaffold subunit has a role in dampening AKT, β-catenin, and FAK (focal adhesion kinase) signalling. Conclusion: We conclude that loss of expression of scaffold and regulatory subunits of PP2A is responsible for its altered function during PCa pathogenesis.
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The PP2A inhibitor I2PP2A is essential for sister chromatid segregation in oocyte meiosis II. Curr Biol 2013; 23:485-90. [PMID: 23434280 DOI: 10.1016/j.cub.2013.02.004] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2012] [Revised: 01/02/2013] [Accepted: 02/01/2013] [Indexed: 11/20/2022]
Abstract
Haploid gametes are generated through two consecutive meiotic divisions, with the segregation of chromosome pairs in meiosis I and sister chromatids in meiosis II. Separase-mediated stepwise removal of cohesion, first from chromosome arms and later from the centromere region, is a prerequisite for maintaining sister chromatids together until their separation in meiosis II [1]. In all model organisms, centromeric cohesin is protected from separase-dependent removal in meiosis I through the activity of PP2A-B56 phosphatase, which is recruited to centromeres by shugoshin/MEI-S332 (Sgo) [2-5]. How this protection of centromeric cohesin is removed in meiosis II is not entirely clear; we find that all the PP2A subunits remain colocalized with the cohesin subunit Rec8 at the centromere of metaphase II chromosomes. Here, we show that sister chromatid separation in oocytes depends on a PP2A inhibitor, namely I2PP2A. I2PP2A colocalizes with the PP2A enzyme at centromeres at metaphase II, independently of bipolar attachment. When I2PP2A is depleted, sister chromatids fail to segregate during meiosis II. Our findings demonstrate that in oocytes I2PP2A is essential for faithful sister chromatid segregation by mediating deprotection of centromeric cohesin in meiosis II.
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33
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Oberg EA, Nifoussi SK, Gingras AC, Strack S. Selective proteasomal degradation of the B'β subunit of protein phosphatase 2A by the E3 ubiquitin ligase adaptor Kelch-like 15. J Biol Chem 2012; 287:43378-89. [PMID: 23135275 DOI: 10.1074/jbc.m112.420281] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Protein phosphatase 2A (PP2A), a ubiquitous and pleiotropic regulator of intracellular signaling, is composed of a core dimer (AC) bound to a variable (B) regulatory subunit. PP2A is an enzyme family of dozens of heterotrimers with different subcellular locations and cellular substrates dictated by the B subunit. B'β is a brain-specific PP2A regulatory subunit that mediates dephosphorylation of Ca(2+)/calmodulin-dependent protein kinase II and tyrosine hydroxylase. Unbiased proteomic screens for B'β interactors identified Cullin3 (Cul3), a scaffolding component of E3 ubiquitin ligase complexes, and the previously uncharacterized Kelch-like 15 (KLHL15). KLHL15 is one of ∼40 Kelch-like proteins, many of which have been identified as adaptors for the recruitment of substrates to Cul3-based E3 ubiquitin ligases. Here, we report that KLHL15-Cul3 specifically targets B'β to promote turnover of the PP2A subunit by ubiquitylation and proteasomal degradation. Comparison of KLHL15 and B'β tissue expression profiles suggests that the E3 ligase adaptor contributes to selective expression of the PP2A/B'β holoenzyme in the brain. We mapped KLHL15 residues critical for homodimerization as well as interaction with Cul3 and B'β. Explaining PP2A subunit selectivity, the divergent N terminus of B'β was found necessary and sufficient for KLHL15-mediated degradation, with Tyr-52 having an obligatory role. Although KLHL15 can interact with the PP2A/B'β heterotrimer, it only degrades B'β, thus promoting exchange with other regulatory subunits. E3 ligase adaptor-mediated control of PP2A holoenzyme composition thereby adds another layer of regulation to cellular dephosphorylation events.
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Affiliation(s)
- Elizabeth A Oberg
- Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242, USA
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34
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Dephosphorylation of Cdc20 is required for its C-box-dependent activation of the APC/C. EMBO J 2012; 31:3351-62. [PMID: 22713866 DOI: 10.1038/emboj.2012.168] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2012] [Accepted: 05/29/2012] [Indexed: 01/01/2023] Open
Abstract
The anaphase-promoting complex/cyclosome (APC/C) ubiquitin ligase is tightly regulated to ensure programmed proteolysis in cells. The activity of the APC/C is positively controlled by cyclin-dependent kinase (CDK), but a second level of control must also exist because phosphorylation inactivates Cdc20, a mitotic APC/C co-activator. How Cdc20 is dephosphorylated specifically, when CDK is high, has remained unexplained. Here, we show that phosphatases are crucial to activate the APC/C. Cdc20 is phosphorylated at six conserved residues (S50/T64/T68/T79/S114/S165) by CDK in Xenopus egg extracts. When all the threonine residues are phosphorylated, Cdc20 binding to and activation of the APC/C are inhibited. Their dephosphorylation is regulated depending on the sites and protein phosphatase 2A, active in mitosis, is essential to dephosphorylate the threonine residues and activate the APC/C. Consistently, most of the Cdc20 bound to the APC/C in anaphase evades phosphorylation at T79. Furthermore, we show that the 'activation domain' of Cdc20 associates with the Apc6 and Apc8 core subunits. Our data suggest that dephosphorylation of Cdc20 is required for its loading and activation of the APC/C ubiquitin ligase.
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Abstract
This review traces the historical origins and conceptual developments leading to the current state of knowledge of the three superfamilies of protein Ser/Thr phosphatases. 'PR enzyme' was identified as an enzyme that inactivates glycogen phosphorylase, although it took 10 years before this ugly duckling was recognized for its true identity as a protein Ser/Thr phosphatase. Ethanol denaturation for purification in the 1970s yielded a phosphatase that exhibited broad specificity, which was resolved into type-1 and type-2 phosphatases in the 1980s. More recent developments show that regulation and specificity are achieved through assembly of multisubunit holoenzymes, transient phosphorylation and the action of inhibitor proteins. Still not widely appreciated, there are hundreds of discrete protein Ser/Thr phosphatases available to counteract protein kinases, offering potential therapeutic targets. Signalling networks and modelling schemes need to incorporate the full gamut of protein Ser/Thr phosphatases and their interconnections.
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Affiliation(s)
- David L Brautigan
- Department of Microbiology, Immunology and Cancer Biology, Center for Cell Signaling, University of Virginia, School of Medicine, Charlottesville, VA 22908, USA.
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36
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Sents W, Ivanova E, Lambrecht C, Haesen D, Janssens V. The biogenesis of active protein phosphatase 2A holoenzymes: a tightly regulated process creating phosphatase specificity. FEBS J 2012; 280:644-61. [PMID: 22443683 DOI: 10.1111/j.1742-4658.2012.08579.x] [Citation(s) in RCA: 157] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Protein phosphatase type 2A (PP2A) enzymes constitute a large family of Ser/Thr phosphatases with multiple functions in cellular signaling and physiology. The composition of heterotrimeric PP2A holoenzymes, resulting from the combinatorial assembly of a catalytic C subunit, a structural A subunit, and regulatory B-type subunit, provides the essential determinants for substrate specificity, subcellular targeting, and fine-tuning of phosphatase activity, largely explaining why PP2A is functionally involved in so many diverse physiological processes, sometimes in seemingly opposing ways. In this review, we highlight how PP2A holoenzyme biogenesis and enzymatic activity are controlled by a sophisticatedly coordinated network of five PP2A modulators, consisting of α4, phosphatase 2A phosphatase activator (PTPA), leucine carboxyl methyl transferase 1 (LCMT1), PP2A methyl esterase 1 (PME-1) and, potentially, target of rapamycin signaling pathway regulator-like 1 (TIPRL1), which serve to prevent promiscuous phosphatase activity until the holoenzyme is completely assembled. Likewise, these modulators may come into play when PP2A holoenzymes are disassembled following particular cellular stresses. Malfunctioning of these cellular control mechanisms contributes to human disease. The potential therapeutic benefits or pitfalls of interfering with these regulatory mechanisms will be briefly discussed.
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Affiliation(s)
- Ward Sents
- Laboratory of Protein Phosphorylation & Proteomics, Department of Cellular and Molecular Medicine, University of Leuven, Leuven, Belgium
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Abstract
Alterations in the functional levels of cyclin-dependent kinase-8 (CDK8) or its partner, cyclin C, have been clearly associated with cancers, including colon cancer, melanoma, and osteosarcoma. Walleye dermal sarcoma virus encodes a retroviral cyclin (RV-cyclin) that localizes to interchromatin granule clusters and binds CDK8. It also binds to the Aα subunit (PR65) of protein phosphatase 2A (PP2A). Binding to the Aα subunit excludes the regulatory B subunit, but not the catalytic C subunit, in a manner similar to that of T antigens of the small DNA tumor viruses. The expression of the RV-cyclin enhances the activity of immune affinity-purified CDK8 in vitro for RNA polymerase II carboxy-terminal domain (CTD) and histone H3 substrates. PP2A also enhances CDK8 kinase activity in vitro for the CTD but not for histone H3. The PP2A enhancement of CDK8 is independent of RV-cyclin expression and likely plays a role in the normal regulation of CDK8. The manipulation of endogenous PP2A activity by inhibition, amendment, or depletion confirmed its role in CDK8 activation by triggering CDK8 autophosphorylation. Although RV-cyclin and PP2A both enhance CDK8 activity, their actions are uncoupled and additive in kinase reactions. PP2A may be recruited to CDK8 in the Mediator complex by a specific PP2A B subunit or additionally by the RV-cyclin in infected cells, but the RV-cyclin appears to activate CDK8 directly and in a manner independent of its physical association with PP2A.
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38
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Kimura T, Han W, Pagel P, Nairn AC, Caplan MJ. Protein phosphatase 2A interacts with the Na,K-ATPase and modulates its trafficking by inhibition of its association with arrestin. PLoS One 2011; 6:e29269. [PMID: 22242112 PMCID: PMC3248462 DOI: 10.1371/journal.pone.0029269] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2011] [Accepted: 11/23/2011] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND The P-type ATPase family constitutes a collection of ion pumps that form phosphorylated intermediates during ion transport. One of the best known members of this family is the Na⁺,K⁺-ATPase. The catalytic subunit of the Na⁺,K⁺-ATPase includes several functional domains that determine its enzymatic and trafficking properties. METHODOLOGY/PRINCIPAL FINDINGS Using the yeast two-hybrid system we found that protein phosphatase 2A (PP2A) catalytic C-subunit is a specific Na⁺,K⁺-ATPase interacting protein. PP-2A C-subunit interacted with the Na⁺,K⁺-ATPase, but not with the homologous sequences of the H⁺,K⁺-ATPase. We confirmed that the Na⁺,K⁺-ATPase interacts with a complex of A- and C-subunits in native rat kidney. Arrestins and G-protein coupled receptor kinases (GRKs) are important regulators of G-protein coupled receptor (GPCR) signaling, and they also regulate Na⁺,K⁺-ATPase trafficking through direct association. PP2A inhibits association between the Na⁺,K⁺-ATPase and arrestin, and diminishes the effect of arrestin on Na⁺,K⁺-ATPase trafficking. GRK phosphorylates the Na⁺,K⁺-ATPase and PP2A can at least partially reverse this phosphorylation. CONCLUSIONS/SIGNIFICANCE Taken together, these data demonstrate that the sodium pump belongs to a growing list of ion transport proteins that are regulated through direct interactions with the catalytic subunit of a protein phosphatase.
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Affiliation(s)
- Toru Kimura
- Department of Pharmacology and Toxicology, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
- Departments of Cellular & Molecular Physiology and
| | - WonSun Han
- Departments of Cellular & Molecular Physiology and
| | | | - Angus C. Nairn
- Psychiatry, Yale University School of Medicine New Haven, Connecticut, United States of America
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Du H, Massiah MA. NMR studies of the C-terminus of alpha4 reveal possible mechanism of its interaction with MID1 and protein phosphatase 2A. PLoS One 2011; 6:e28877. [PMID: 22194938 PMCID: PMC3237570 DOI: 10.1371/journal.pone.0028877] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2011] [Accepted: 11/16/2011] [Indexed: 12/17/2022] Open
Abstract
Alpha4 is a regulatory subunit of the protein phosphatase family of enzymes and plays an essential role in regulating the catalytic subunit of PP2A (PP2Ac) within the rapamycin-sensitive signaling pathway. Alpha4 also interacts with MID1, a microtubule-associated ubiquitin E3 ligase that appears to regulate the function of PP2A. The C-terminal region of alpha4 plays a key role in the binding interaction of PP2Ac and MID1. Here we report on the solution structure of a 45-amino acid region derived from the C-terminus of alpha4 (alpha45) that binds tightly to MID1. In aqueous solution, alpha45 has properties of an intrinsically unstructured peptide although chemical shift index and dihedral angle estimation based on chemical shifts of backbone atoms indicate the presence of a transient α-helix. Alpha45 adopts a helix-turn-helix HEAT-like structure in 1% SDS micelles, which may mimic a negatively charged surface for which alpha45 could bind. Alpha45 binds tightly to the Bbox1 domain of MID1 in aqueous solution and adopts a structure consistent with the helix-turn-helix structure observed in 1% SDS. The structure of alpha45 reveals two distinct surfaces, one that can interact with a negatively charged surface, which is present on PP2A, and one that interacts with the Bbox1 domain of MID1.
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Affiliation(s)
- Haijuan Du
- Department of Chemistry, George Washington University, Washington, D.C., United States of America
| | - Michael A. Massiah
- Department of Chemistry, George Washington University, Washington, D.C., United States of America
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40
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Guergnon J, Godet AN, Galioot A, Falanga PB, Colle JH, Cayla X, Garcia A. PP2A targeting by viral proteins: a widespread biological strategy from DNA/RNA tumor viruses to HIV-1. Biochim Biophys Acta Mol Basis Dis 2011; 1812:1498-507. [PMID: 21856415 DOI: 10.1016/j.bbadis.2011.07.001] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Revised: 06/22/2011] [Accepted: 07/05/2011] [Indexed: 12/27/2022]
Abstract
Protein phosphatase 2A (PP2A) is a large family of holoenzymes that comprises 1% of total cellular proteins and accounts for the majority of Ser/Thr phosphatase activity in eukaryotic cells. Although initially viewed as constitutive housekeeping enzymes, it is now well established that PP2A proteins represent a family of highly and sophistically regulated phosphatases. The past decade, multiple complementary studies have improved our knowledge about structural and functional regulation of PP2A holoenzymes. In this regard, after summarizing major cellular regulation, this review will mainly focus on discussing a particulate biological strategy, used by various viruses, which is based on the targeting of PP2A enzymes by viral proteins in order to specifically deregulate, for their own benefit, cellular pathways of their hosts. The impact of such PP2A targeting for research in human diseases, and in further therapeutic developments, is also discussed.
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Affiliation(s)
- Julien Guergnon
- Laboratoire E3 Phosphatases-Unité Signalisation Moléculaire et Activation Cellulaire, Institut Pasteur 25, rue du Dr Roux, 75015 Paris, France
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41
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Human cancer-associated mutations in the Aα subunit of protein phosphatase 2A increase lung cancer incidence in Aα knock-in and knockout mice. Mol Cell Biol 2011; 31:3832-44. [PMID: 21791616 DOI: 10.1128/mcb.05744-11] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Strong evidence has indicated that protein phosphatase 2A (PP2A) is a tumor suppressor, but a mouse model for testing the tumor suppressor activity was missing. The most abundant forms of trimeric PP2A holoenzyme consist of the scaffolding Aα subunit, one of several regulatory B subunits, and the catalytic Cα subunit. Aα mutations were discovered in a variety of human carcinomas. All carcinoma-associated mutant Aα subunits are defective in binding the B or B and C subunits. Here we describe two knock-in mice expressing cancer-associated Aα point mutants defective in binding B' subunits, one knockout mouse expressing truncated Aα defective in B and C subunit binding, and a floxed mouse for generating conditional Aα knockouts. We found that the cancer-associated Aα mutations increased the incidence of cancer by 50 to 60% in lungs of FVB mice treated with benzopyrene, demonstrating that PP2A acts as a tumor suppressor. We show that the effect of Aα mutation on cancer incidence is dependent on the tumor suppressor p53. The finding that the Aα mutation E64D, which was detected in a human lung carcinoma, increases the lung cancer incidence in mice suggests that this mutation also played a role in the development of the carcinoma in which it was discovered.
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42
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Rodgers JT, Vogel RO, Puigserver P. Clk2 and B56β mediate insulin-regulated assembly of the PP2A phosphatase holoenzyme complex on Akt. Mol Cell 2011; 41:471-9. [PMID: 21329884 DOI: 10.1016/j.molcel.2011.02.007] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2010] [Revised: 11/03/2010] [Accepted: 01/20/2011] [Indexed: 12/20/2022]
Abstract
Akt mediates important cellular decisions involved in growth, survival, and metabolism. The mechanisms by which Akt is phosphorylated and activated in response to growth factors or insulin have been extensively studied, but the molecular regulatory components and dynamics of Akt attenuation are poorly understood. Here we show that a downstream target of insulin-induced Akt activation, Clk2, triggers Akt dephosphorylation through the PP2A phosphatase complex. Clk2 phosphorylates the PP2A regulatory subunit B56β (PPP2R5B, B'β), which is a critical regulatory step in the assembly of the PP2A holoenzyme complex on Akt leading to dephosphorylation of both S473 and T308 Akt sites. Since Akt plays a pivotal role in cellular signaling, these results have important implications for our understanding of Akt regulation in many biological processes.
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Affiliation(s)
- Joseph T Rodgers
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02115, USA
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43
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Xu H, Ginsburg KS, Hall DD, Zimmermann M, Stein IS, Zhang M, Tandan S, Hill JA, Horne MC, Bers D, Hell JW. Targeting of protein phosphatases PP2A and PP2B to the C-terminus of the L-type calcium channel Ca v1.2. Biochemistry 2010; 49:10298-307. [PMID: 21053940 PMCID: PMC3075818 DOI: 10.1021/bi101018c] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The L-type Ca(2+) channel Ca(v)1.2 forms macromolecular signaling complexes that comprise the β(2) adrenergic receptor, trimeric G(s) protein, adenylyl cyclase, and cAMP-dependent protein kinase (PKA) for efficient signaling in heart and brain. The protein phosphatases PP2A and PP2B are part of this complex. PP2A counteracts increase in Ca(v)1.2 channel activity by PKA and other protein kinases, whereas PP2B can either augment or decrease Ca(v)1.2 currents in cardiomyocytes depending on the precise experimental conditions. We found that PP2A binds to two regions in the C-terminus of the central, pore-forming α(1) subunit of Ca(v)1.2: one region spans residues 1795-1818 and the other residues 1965-1971. PP2B binds immediately downstream of residue 1971. Injection of a peptide that contained residues 1965-1971 and displaced PP2A but not PP2B from endogenous Ca(v)1.2 increased basal and isoproterenol-stimulated L-type Ca(2+) currents in acutely isolated cardiomyocytes. Together with our biochemical data, these physiological results indicate that anchoring of PP2A at this site of Ca(v)1.2 in the heart negatively regulates cardiac L-type currents, likely by counterbalancing basal and stimulated phosphorylation that is mediated by PKA and possibly other kinases.
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Affiliation(s)
- Hui Xu
- Department of Pharmacology, University of Iowa, Iowa City, IA 52242-1109, USA
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44
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Saha S, Kaur P, Ewing RM. The bait compatibility index: computational bait selection for interaction proteomics experiments. J Proteome Res 2010; 9:4972-81. [PMID: 20731387 DOI: 10.1021/pr100267t] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Protein interaction network maps have been generated for multiple species, making use of large-scale methods such as yeast two-hybrid (Y2H) and affinity purification mass spectrometry (AP-MS). These methods take fundamentally different approaches toward characterizing protein networks, and the resulting data sets provide complementary views of the protein interactome. The specific determinants of the outcome of Y2H and AP-MS experiments, in terms of detection of interacting proteins are, however, poorly understood. Here we show that a statistical model built using sequence- and annotation-based features of bait proteins is able to identify bait features that are significant determinants of the outcome of interaction proteomics experiments. We show that bait features are able to explain in part the disparities observed between Y2H and AP-MS constructed networks and can be used to derive the "bait compatibility index", a numeric score that assesses the compatibility of bait proteins with each technology. Aside from understanding the bias and limitations of interaction proteomics, our approach provides a rational, data-driven method for prioritization of baits for interaction proteomics experiments, an essential requirement for future proteome-wide applications of these technologies.
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Affiliation(s)
- Sudipto Saha
- Center for Proteomics and Bioinformatics, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
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45
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Ohama T, Brautigan DL. Endotoxin conditioning induces VCP/p97-mediated and inducible nitric-oxide synthase-dependent Tyr284 nitration in protein phosphatase 2A. J Biol Chem 2010; 285:8711-8. [PMID: 20100830 DOI: 10.1074/jbc.m109.099788] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Endotoxins activate Toll-like receptors and reprogram cells to be refractory to secondary exposure. Here we found that activation of different Toll-like receptors elicited a time- and dose-dependent increase in the levels of the protein phosphatase 2A catalytic subunit (PP2Ac) but not its partner A subunit. We purified the lipopolysaccharide-induced form of PP2A by chromatography plus immunoprecipitation and used mass spectrometry to identify VCP/p97 as a novel partner for PP2Ac. Endogenous VCP/p97 and PP2Ac were co-immunoprecipitated from primary murine macrophages and human lymphocytes. GST-VCP/p97 bound purified PP2A in pulldown assays, showing direct protein-protein interaction. Endotoxin conditioning of macrophages induced formation of 3-nitrotyrosine in the PP2Ac associated with VCP/p97, a response severely reduced in macrophages from iNOS knock-out mice. The reaction of purified PP2A with peroxynitrite dissociated the A subunit, and 3-nitro-Tyr(284) was identified in PP2Ac by mass spectrometry. Myc-PP2Ac (Y284F) expressed in cells was resistant to peroxynitrite-induced nitration and reduction of A subunit binding. Transient expression of either VCP/p97 or PP2Ac was sufficient to elevate levels of the dual specificity phosphatase DUSP1, reduce p38 MAPK activation, and suppress tumor necrosis factor-alpha release. We propose that VCP/p97-mediated Tyr nitration of PP2A increases the levels of phosphatases PP2A and DUSP1 to contribute to the refractory response of conditioned cells.
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Affiliation(s)
- Takashi Ohama
- Department of Microbiology, University of Virginia School of Medicine, Center for Cell Signaling, Charlottesville, Virginia 22908, USA
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46
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A nonhomologous end-joining pathway is required for protein phosphatase 2A promotion of DNA double-strand break repair. Neoplasia 2010; 11:1012-21. [PMID: 19794960 DOI: 10.1593/neo.09720] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2009] [Revised: 06/25/2009] [Accepted: 06/25/2009] [Indexed: 12/31/2022] Open
Abstract
Protein phosphatase 2A (PP2A) functions as a potent tumor suppressor, but its mechanism(s) remains enigmatic. Specific disruption of PP2A by either expression of SV40 small tumor antigen or depletion of endogenous PP2A/C by RNA interference inhibits Ku DNA binding and DNA-PK activities, which results in suppression of DNA double-strand break (DSB) repair and DNA end-joining in association with increased genetic instability (i.e., chromosomal and chromatid breaks). Overexpression of the PP2A catalytic subunit (PP2A/C) enhances Ku and DNA-PK activities with accelerated DSB repair. Camptothecin-induced DSBs promote PP2A to associate with Ku 70 and Ku 86. PP2A directly dephosphorylates Ku as well as the DNA-PK catalytic subunit (DNA-PKcs) in vitro and in vivo, which enhances the formation of a functional Ku/DNA-PKcs complex. Intriguingly, PP2A promotes DSB repair in wild type mouse embryonic fibroblast (MEF) cells but has no such effect in Ku-deficient MEF cells, suggesting that the Ku 70/86 heterodimer is required for PP2A promotion of DSB repair. Thus, PP2A promotion of DSB repair may occur in a novel mechanism by activating the nonhomologous end-joining pathway through direct dephosphorylation of Ku and DNA-PKcs, which may contribute to maintenance of genetic stability.
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48
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Castilho PV, Williams BC, Mochida S, Zhao Y, Goldberg ML. The M phase kinase Greatwall (Gwl) promotes inactivation of PP2A/B55delta, a phosphatase directed against CDK phosphosites. Mol Biol Cell 2009; 20:4777-89. [PMID: 19793917 DOI: 10.1091/mbc.e09-07-0643] [Citation(s) in RCA: 156] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
We have previously shown that Greatwall kinase (Gwl) is required for M phase entry and maintenance in Xenopus egg extracts. Here, we demonstrate that Gwl plays a crucial role in a novel biochemical pathway that inactivates, specifically during M phase, "antimitotic" phosphatases directed against phosphorylations catalyzed by cyclin-dependent kinases (CDKs). A major component of this phosphatase activity is heterotrimeric PP2A containing the B55delta regulatory subunit. Gwl is activated during M phase by Cdk1/cyclin B (MPF), but once activated, Gwl promotes PP2A/B55delta inhibition with no further requirement for MPF. In the absence of Gwl, PP2A/B55delta remains active even when MPF levels are high. The removal of PP2A/B55delta corrects the inability of Gwl-depleted extracts to enter M phase. These findings support the hypothesis that M phase requires not only high levels of MPF function, but also the suppression, through a Gwl-dependent mechanism, of phosphatase(s) that would otherwise remove MPF-driven phosphorylations.
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Affiliation(s)
- Priscila V Castilho
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
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49
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Mochida S, Ikeo S, Gannon J, Hunt T. Regulated activity of PP2A-B55 delta is crucial for controlling entry into and exit from mitosis in Xenopus egg extracts. EMBO J 2009; 28:2777-85. [PMID: 19696736 DOI: 10.1038/emboj.2009.238] [Citation(s) in RCA: 220] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2009] [Accepted: 07/15/2009] [Indexed: 11/09/2022] Open
Abstract
Entry into mitosis depends on the activity of cyclin-dependent kinases (CDKs). Conversely, exit from mitosis occurs when mitotic cyclins are degraded, thereby extinguishing CDK activity. Exit from mitosis must also require mitotic phosphoproteins to revert to their interphase hypophosphorylated forms, but there is a controversy about which phosphatase(s) is/are responsible for dephosphorylating the CDK substrates. We find that PP2A associated with a B55 delta subunit is relatively specific for a model mitotic CDK substrate in Xenopus egg extracts. The phosphatase activity measured by this substrate is regulated during the cell cycle--high in interphase and suppressed during mitosis. Depletion of PP2A-B55 delta (in interphase) from 'cycling' frog egg extracts accelerated their entry into mitosis and kept them indefinitely in mitosis. When PP2A-B55 delta was depleted from mitotic extracts, however, exit from mitosis was hardly delayed, showing that other phosphatase(s) are also required for mitotic exit. Increasing the concentration of PP2A-B55 delta in extracts by adding recombinant enzyme inhibited the entry into mitosis. This form of PP2A seems to be a key regulator of entry into and exit from mitosis.
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Affiliation(s)
- Satoru Mochida
- Cancer Research UK, London Research Institute, Clare Hall Laboratories, South Mimms, Herts, UK
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50
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Vigneron S, Brioudes E, Burgess A, Labbé JC, Lorca T, Castro A. Greatwall maintains mitosis through regulation of PP2A. EMBO J 2009; 28:2786-93. [PMID: 19680222 DOI: 10.1038/emboj.2009.228] [Citation(s) in RCA: 154] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2009] [Accepted: 07/20/2009] [Indexed: 11/10/2022] Open
Abstract
Greatwall (GW) is a new kinase that has an important function in the activation and the maintenance of cyclin B-Cdc2 activity. Although the mechanism by which it induces this effect is unknown, it has been suggested that GW could maintain cyclin B-Cdc2 activity by regulating its activation loop. Using Xenopus egg extracts, we show that GW depletion promotes mitotic exit, even in the presence of a high cyclin B-Cdc2 activity by inducing dephosphorylation of mitotic substrates. These results indicate that GW does not maintain the mitotic state by regulating the cyclin B-Cdc2 activation loop but by regulating a phosphatase. This phosphatase is PP2A; we show that (1) PP2A binds GW, (2) the inhibition or the specific depletion of this phosphatase from mitotic extracts rescues the phenotype induced by GW inactivation and (3) the PP2A-dependent dephosphorylation of cyclin B-Cdc2 substrates is increased in GW-depleted Xenopus egg extracts. These results suggest that mitotic entry and maintenance is not only mediated by the activation of cyclin B-Cdc2 but also by the regulation of PP2A by GW.
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Affiliation(s)
- Suzanne Vigneron
- Centre de Recherche de Biochimie Macromoléculaire, CNRS UMR 5237, IFR 122, Labellisée Ligue Nationale Contre le Cancer, Universités Montpellier 2 et 1, Montpellier, France
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