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Wasserman JS, Faezov B, Patel KR, Kurimchak AM, Palacio SM, Glass DJ, Fowle H, McEwan BC, Xu Q, Zhao Z, Cressey L, Johnson N, Duncan JS, Kettenbach AN, Dunbrack RL, Graña X. FAM122A ensures cell cycle interphase progression and checkpoint control by inhibiting B55α/PP2A through helical motifs. Nat Commun 2024; 15:5776. [PMID: 38982062 PMCID: PMC11233601 DOI: 10.1038/s41467-024-50015-7] [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: 03/05/2023] [Accepted: 06/26/2024] [Indexed: 07/11/2024] Open
Abstract
The Ser/Thr protein phosphatase 2 A (PP2A) regulates the dephosphorylation of many phosphoproteins. Substrate recognition are mediated by B regulatory subunits. Here, we report the identification of a substrate conserved motif [RK]-V-x-x-[VI]-R in FAM122A, an inhibitor of B55α/PP2A. This motif is necessary for FAM122A binding to B55α, and computational structure prediction suggests the motif, which is helical, blocks substrate docking to the same site. In this model, FAM122A also spatially constrains substrate access by occluding the catalytic subunit. Consistently, FAM122A functions as a competitive inhibitor as it prevents substrate binding and dephosphorylation of CDK substrates by B55α/PP2A in cell lysates. FAM122A deficiency in human cell lines reduces the proliferation rate, cell cycle progression, and hinders G1/S and intra-S phase cell cycle checkpoints. FAM122A-KO in HEK293 cells attenuates CHK1 and CHK2 activation in response to replication stress. Overall, these data strongly suggest that FAM122A is a short helical motif (SHeM)-dependent, substrate-competitive inhibitor of B55α/PP2A that suppresses multiple functions of B55α in the DNA damage response and in timely progression through the cell cycle interphase.
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Affiliation(s)
- Jason S Wasserman
- Fels Cancer Institute for Personalized Medicine. Temple University Lewis Katz School of Medicine, Philadelphia, PA, USA
| | - Bulat Faezov
- Fox Chase Cancer Center, Temple Health, Philadelphia, PA, USA
- Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan, Russian Federation
| | - Kishan R Patel
- Fels Cancer Institute for Personalized Medicine. Temple University Lewis Katz School of Medicine, Philadelphia, PA, USA
| | | | - Seren M Palacio
- Fels Cancer Institute for Personalized Medicine. Temple University Lewis Katz School of Medicine, Philadelphia, PA, USA
| | - David J Glass
- Fox Chase Cancer Center, Temple Health, Philadelphia, PA, USA
| | - Holly Fowle
- Fels Cancer Institute for Personalized Medicine. Temple University Lewis Katz School of Medicine, Philadelphia, PA, USA
| | - Brennan C McEwan
- Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth, Medical Center Drive, Lebanon, NH, USA
| | - Qifang Xu
- Fox Chase Cancer Center, Temple Health, Philadelphia, PA, USA
| | - Ziran Zhao
- Fels Cancer Institute for Personalized Medicine. Temple University Lewis Katz School of Medicine, Philadelphia, PA, USA
| | - Lauren Cressey
- Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth, Medical Center Drive, Lebanon, NH, USA
| | - Neil Johnson
- Fox Chase Cancer Center, Temple Health, Philadelphia, PA, USA
| | - James S Duncan
- Fox Chase Cancer Center, Temple Health, Philadelphia, PA, USA
| | - Arminja N Kettenbach
- Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth, Medical Center Drive, Lebanon, NH, USA
| | | | - Xavier Graña
- Fels Cancer Institute for Personalized Medicine. Temple University Lewis Katz School of Medicine, Philadelphia, PA, USA.
- Fox Chase Cancer Center, Temple Health, Philadelphia, PA, USA.
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Chen H, Li J, Pi C, Guo D, Zhang D, Zhou X, Xie J. FGF19 induces the cell cycle arrest at G2-phase in chondrocytes. Cell Death Discov 2023; 9:250. [PMID: 37454120 DOI: 10.1038/s41420-023-01543-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2022] [Revised: 06/13/2023] [Accepted: 07/04/2023] [Indexed: 07/18/2023] Open
Abstract
Fibroblast growth factor 19 (FGF19) has appeared as a new possible avenue in the treatment of skeletal metabolic disorders. However, the role of FGF19 on cell cycle progression in skeletal system is poorly understood. Here we demonstrated that FGF19 had the ability to reduce the proliferation of chondrocytes and cause cell cycle G2 phase arrest through its interaction with β-Klotho (KLB), an important accessory protein that helps FGF19 link to its receptor. FGF19-mediated cell cycle arrest by regulating the expressions of cdk1/cylinb1, chk1 and gadd45a. We then confirmed that the binding of FGF19 to the membrane receptor FGFR4 was necessary for FGF19-mediated cell cycle arrest, and further proved that FGF19-mediated cell cycle arrest was via activation of p38/MAPK signaling. Through inhibitor experiments, we discovered that inhibition of FGFR4 led to down-regulation of p38 signaling even in the presence of FGF19. Meanwhile, inhibiting p38 signaling reduced the cell cycle arrest of chondrocytes induced by FGF19. Furthermore, blocking p38 signaling facilitated to retain the expression of cdk1 and cyclinb1 that had been reduced in chondrocytes by FGF19 and decreased the expression of chk1 and gadd45a that had been enhanced by FGF19 in chondrocytes. Taking together, this study is the first to demonstrate that FGF19 induces cell cycle arrest at G2 phase via FGFR4-p38/MAPK axis and enlarges our understanding about the role of FGF19 on cell cycle progression in chondrocytes.
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Affiliation(s)
- Hao Chen
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, 610041, Chengdu, China
| | - Jiazhou Li
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, 610041, Chengdu, China
| | - Caixia Pi
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, 610041, Chengdu, China
| | - Daimo Guo
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, 610041, Chengdu, China
| | - Demao Zhang
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, 610041, Chengdu, China
| | - Xuedong Zhou
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, 610041, Chengdu, China.
- National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, 610041, Chengdu, China.
- Department of Cariology and Endodontics, West China Hospital of Stomatology, Sichuan University, 610041, Chengdu, China.
| | - Jing Xie
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, 610041, Chengdu, China.
- National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, 610041, Chengdu, China.
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Wasserman JS, Faezov B, Patel KR, Kurimchak AN, Palacio SM, Fowle H, McEwan BC, Xu Q, Zhao Z, Cressey L, Johnson N, Duncan JS, Kettenbach AN, Dunbrack RL, Graña X. FAM122A ensures cell cycle interphase progression and checkpoint control as a SLiM-dependent substrate-competitive inhibitor to the B55⍺/PP2A phosphatase. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.06.531310. [PMID: 36945596 PMCID: PMC10028791 DOI: 10.1101/2023.03.06.531310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/12/2023]
Abstract
The Ser/Thr protein phosphatase 2A (PP2A) is a highly conserved collection of heterotrimeric holoenzymes responsible for the dephosphorylation of many regulated phosphoproteins. Substrate recognition and the integration of regulatory cues are mediated by B regulatory subunits that are complexed to the catalytic subunit (C) by a scaffold protein (A). PP2A/B55 substrate recruitment was thought to be mediated by charge-charge interactions between the surface of B55α and its substrates. Challenging this view, we recently discovered a conserved SLiM [ RK ]- V -x-x-[ VI ]- R in a range of proteins, including substrates such as the retinoblastoma-related protein p107 and TAU (Fowle et al. eLife 2021;10:e63181). Here we report the identification of this SLiM in FAM122A, an inhibitor of B55α/PP2A. This conserved SLiM is necessary for FAM122A binding to B55α in vitro and in cells. Computational structure prediction with AlphaFold2 predicts an interaction consistent with the mutational and biochemical data and supports a mechanism whereby FAM122A uses the 'SLiM' in the form of a short α-helix to dock to the B55α top groove. In this model, FAM122A spatially constrains substrate access by occluding the catalytic subunit with a second α-helix immediately adjacent to helix 1. Consistently, FAM122A functions as a competitive inhibitor as it prevents binding of substrates in in vitro competition assays and the dephosphorylation of CDK substrates by B55α/PP2A in cell lysates. Ablation of FAM122A in human cell lines reduces the rate of proliferation, progression through cell cycle transitions and abrogates G1/S and intra-S phase cell cycle checkpoints. FAM122A-KO in HEK293 cells results in attenuation of CHK1 and CHK2 activation in response to replication stress. Overall, these data strongly suggest that FAM122A is a 'SLiM'-dependent, substrate-competitive inhibitor of B55α/PP2A that suppresses multiple functions of B55α in the DNA damage response and in timely progression through the cell cycle interphase.
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Doi K, Takeuchi H, Sakurai H. PP2A-B55 and its adapter proteins IER2 and IER5 regulate the activity of RB family proteins and the expression of cell cycle-related genes. FEBS J 2023; 290:745-762. [PMID: 36047562 DOI: 10.1111/febs.16612] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Revised: 08/05/2022] [Accepted: 08/30/2022] [Indexed: 02/04/2023]
Abstract
The retinoblastoma (RB) tumour suppressor protein regulates cell proliferation, motility, differentiation and apoptosis. The phosphorylation state of RB is modulated by kinases and phosphatases, and RB exhibits phosphorylation-sensitive interactions with E2F family transcription factors. Here, we characterize RB dephosphorylation by protein phosphatase 2A (PP2A). The growth factor-inducible immediate early response (IER) proteins IER2 and IER5 possess an adapter-like function in which IER proteins bind to both PP2A and its target proteins and enhance PP2A activity towards the proteins. IER2 interacts with RB and facilitates dephosphorylation of RB at T821/T826 by PP2A. In IER2 knockdown cells, elevated phosphorylation of RB resulted in reduced binding of RB to the promoters and derepression of cyclin D1 and p21. IER5 binds to both RB and RB-like 1 (p107/RBL1), enhances dephosphorylation of these proteins by PP2A and represses the expression of various cell cycle-related genes. However, IER2-regulated dephosphorylation at T821/T826 is not necessary for the repression function of RB in cell mobility-related gene expression. Our data identify PP2A adapter proteins as critical regulators of RB family proteins and suggest that the phosphorylation status of RB differentially affects gene expression.
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Affiliation(s)
- Kuriko Doi
- Division of Health Sciences, Graduate School of Medical Science, Kanazawa University, Japan
| | - Hiroto Takeuchi
- Division of Health Sciences, Graduate School of Medical Science, Kanazawa University, Japan
| | - Hiroshi Sakurai
- Division of Health Sciences, Graduate School of Medical Science, Kanazawa University, Japan
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de los Ríos C, Viejo L, Carretero VJ, Juárez NH, Cruz-Martins N, Hernández-Guijo JM. Promising Molecular Targets in Pharmacological Therapy for Neuronal Damage in Brain Injury. Antioxidants (Basel) 2023; 12:118. [PMID: 36670980 PMCID: PMC9854812 DOI: 10.3390/antiox12010118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Revised: 12/19/2022] [Accepted: 12/27/2022] [Indexed: 01/05/2023] Open
Abstract
The complex etiopathogenesis of brain injury associated with neurodegeneration has sparked a lot of studies in the last century. These clinical situations are incurable, and the currently available therapies merely act on symptoms or slow down the course of the diseases. Effective methods are being sought with an intent to modify the disease, directly acting on the properly studied targets, as well as to contribute to the development of effective therapeutic strategies, opening the possibility of refocusing on drug development for disease management. In this sense, this review discusses the available evidence for mitochondrial dysfunction induced by Ca2+ miscommunication in neurons, as well as how targeting phosphorylation events may be used to modulate protein phosphatase 2A (PP2A) activity in the treatment of neuronal damage. Ca2+ tends to be the catalyst for mitochondrial dysfunction, contributing to the synaptic deficiency seen in brain injury. Additionally, emerging data have shown that PP2A-activating drugs (PADs) suppress inflammatory responses by inhibiting different signaling pathways, indicating that PADs may be beneficial for the management of neuronal damage. In addition, a few bioactive compounds have also triggered the activation of PP2A-targeted drugs for this treatment, and clinical studies will help in the authentication of these compounds. If the safety profiles of PADs are proven to be satisfactory, there is a case to be made for starting clinical studies in the setting of neurological diseases as quickly as possible.
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Affiliation(s)
- Cristóbal de los Ríos
- Department of Pharmacology and Therapeutic and Teófilo Hernando Institute, Faculty of Medicine, University Autónoma de Madrid, C/. Arzobispo Morcillo 4, 28029 Madrid, Spain
- Departamento de Ciencias Básicas de la Salud, University Rey Juan Carlos, Avda. Atenas s/n, 28922 Alcorcón, Spain
| | - Lucía Viejo
- Department of Pharmacology and Therapeutic and Teófilo Hernando Institute, Faculty of Medicine, University Autónoma de Madrid, C/. Arzobispo Morcillo 4, 28029 Madrid, Spain
| | - Victoria Jiménez Carretero
- Department of Pharmacology and Therapeutic and Teófilo Hernando Institute, Faculty of Medicine, University Autónoma de Madrid, C/. Arzobispo Morcillo 4, 28029 Madrid, Spain
| | - Natalia Hernández Juárez
- Department of Pharmacology and Therapeutic and Teófilo Hernando Institute, Faculty of Medicine, University Autónoma de Madrid, C/. Arzobispo Morcillo 4, 28029 Madrid, Spain
| | - Natália Cruz-Martins
- Faculty of Medicine, Institute for Research and Innovation in Health (i3S), University of Porto, 4200-319 Porto, Portugal
- Institute for Research and Advanced Training in Health Sciences and Technologies, Rua Central de Gandra, 1317, 4585-116 Gandra, Portugal
| | - Jesús M. Hernández-Guijo
- Department of Pharmacology and Therapeutic and Teófilo Hernando Institute, Faculty of Medicine, University Autónoma de Madrid, C/. Arzobispo Morcillo 4, 28029 Madrid, Spain
- Ramón y Cajal Institute for Health Research, IRYCIS, Hospital Ramón y Cajal, Ctra. de Colmenar Viejo, Km. 9,100, 28029 Madrid, Spain
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6
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PP2A-B55: substrates and regulators in the control of cellular functions. Oncogene 2022; 41:1-14. [PMID: 34686773 DOI: 10.1038/s41388-021-02068-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 09/29/2021] [Accepted: 10/06/2021] [Indexed: 12/17/2022]
Abstract
PP2A is a major serine/threonine phosphatase class involved in the regulation of cell signaling through the removal of protein phosphorylation. This class of phosphatases is comprised of different heterotrimeric complexes displaying distinct substrate specificities. The present review will focus on one specific heterocomplex, the phosphatase PP2A-B55. Herein, we will report the direct substrates of this phosphatase identified to date, and its impact on different cell signaling cascades. We will additionally describe its negative regulation by its inhibitors Arpp19 and ENSA and their upstream kinase Greatwall. Finally, we will describe the essential molecular features defining PP2A-B55 substrate specificity that confer the correct temporal pattern of substrate dephosphorylation. The main objective of this review is to provide the reader with a unique source compiling all the knowledge of this particular holoenzyme that has evolved as a key enzyme for cell homeostasis and cancer development.
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7
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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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Fowle H, Zhao Z, Xu Q, Wasserman JS, Wang X, Adeyemi M, Feiser F, Kurimchak AN, Atar D, McEwan BC, Kettenbach AN, Page R, Peti W, Dunbrack RL, Graña X. PP2A/B55α substrate recruitment as defined by the retinoblastoma-related protein p107. eLife 2021; 10:e63181. [PMID: 34661528 PMCID: PMC8575462 DOI: 10.7554/elife.63181] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Accepted: 10/17/2021] [Indexed: 12/23/2022] Open
Abstract
Protein phosphorylation is a reversible post-translation modification essential in cell signaling. This study addresses a long-standing question as to how the most abundant serine/threonine protein phosphatase 2 (PP2A) holoenzyme, PP2A/B55α, specifically recognizes substrates and presents them to the enzyme active site. Here, we show how the PP2A regulatory subunit B55α recruits p107, a pRB-related tumor suppressor and B55α substrate. Using molecular and cellular approaches, we identified a conserved region 1 (R1, residues 615-626) encompassing the strongest p107 binding site. This enabled us to identify an 'HxRVxxV619-625' short linear motif (SLiM) in p107 as necessary for B55α binding and dephosphorylation of the proximal pSer-615 in vitro and in cells. Numerous B55α/PP2A substrates, including TAU, contain a related SLiM C-terminal from a proximal phosphosite, 'p[ST]-P-x(4,10)-[RK]-V-x-x-[VI]-R.' Mutation of conserved SLiM residues in TAU dramatically inhibits dephosphorylation by PP2A/B55α, validating its generality. A data-guided computational model details the interaction of residues from the conserved p107 SLiM, the B55α groove, and phosphosite presentation. Altogether, these data provide key insights into PP2A/B55α's mechanisms of substrate recruitment and active site engagement, and also facilitate identification and validation of new substrates, a key step towards understanding PP2A/B55α's role in multiple cellular processes.
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Affiliation(s)
- Holly Fowle
- Fels Cancer Institute for Personalized Medicine, Temple University Lewis Katz School of MedicinePhiladelphiaUnited States
| | - Ziran Zhao
- Fels Cancer Institute for Personalized Medicine, Temple University Lewis Katz School of MedicinePhiladelphiaUnited States
| | - Qifang Xu
- Institute for Cancer Research, Fox Chase Cancer CenterPhiladelphiaUnited States
| | - Jason S Wasserman
- Fels Cancer Institute for Personalized Medicine, Temple University Lewis Katz School of MedicinePhiladelphiaUnited States
| | - Xinru Wang
- Department of Chemistry and Biochemistry, University of ArizonaTucsonUnited States
| | - Mary Adeyemi
- Fels Cancer Institute for Personalized Medicine, Temple University Lewis Katz School of MedicinePhiladelphiaUnited States
| | - Felicity Feiser
- Fels Cancer Institute for Personalized Medicine, Temple University Lewis Katz School of MedicinePhiladelphiaUnited States
| | - Alison N Kurimchak
- Fels Cancer Institute for Personalized Medicine, Temple University Lewis Katz School of MedicinePhiladelphiaUnited States
| | - Diba Atar
- Fels Cancer Institute for Personalized Medicine, Temple University Lewis Katz School of MedicinePhiladelphiaUnited States
| | - Brennan C McEwan
- Department of Biochemistry and Cell Biology, Hitchcock Medical Center at DartmouthLebanonUnited States
| | - Arminja N Kettenbach
- Department of Biochemistry and Cell Biology, Hitchcock Medical Center at DartmouthLebanonUnited States
| | - Rebecca Page
- Department of Cell Biology, UConn HealthFarmingtonUnited States
| | - Wolfgang Peti
- Department of Molecular Biology and Biophysics, UConn HealthFarmingtonUnited States
| | - Roland L Dunbrack
- Institute for Cancer Research, Fox Chase Cancer CenterPhiladelphiaUnited States
| | - Xavier Graña
- Fels Cancer Institute for Personalized Medicine, Temple University Lewis Katz School of MedicinePhiladelphiaUnited States
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9
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Ventura E, Iannuzzi CA, Pentimalli F, Giordano A, Morrione A. RBL1/p107 Expression Levels Are Modulated by Multiple Signaling Pathways. Cancers (Basel) 2021; 13:cancers13195025. [PMID: 34638509 PMCID: PMC8507926 DOI: 10.3390/cancers13195025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 09/29/2021] [Accepted: 10/02/2021] [Indexed: 11/16/2022] Open
Abstract
The members of the retinoblastoma (RB) protein family, RB1/p105, retinoblastoma-like (RBL)1/p107 and RBL2/p130 are critical modulators of the cell cycle and their dysregulation has been associated with tumor initiation and progression. The activity of RB proteins is regulated by numerous pathways including oncogenic signaling, but the molecular mechanisms of these functional interactions are not fully defined. We previously demonstrated that RBL2/p130 is a direct target of AKT and it is a key mediator of the apoptotic process induced by AKT inhibition. Here we demonstrated that RBL1/p107 levels are only minorly modulated by the AKT signaling pathway. In contrast, we discovered that RBL1/p107 levels are regulated by multiple pathways linked directly or indirectly to Ca2+-dependent signaling. Inhibition of the multifunctional calcium/calmodulin-dependent kinases (CaMKs) significantly reduced RBL1/p107 expression levels and phosphorylation, increased RBL1/p107 nuclear localization and led to cell cycle arrest in G0/G1. Targeting the Ca2+-dependent endopeptidase calpain stabilized RBL1/p107 levels and counteracted the reduction of RBL1/p107 levels associated with CaMKs inhibition. Thus, these novel observations suggest a complex regulation of RBL1/p107 expression involving different components of signaling pathways controlled by Ca2+ levels, including CaMKs and calpain, pointing out a significant difference with the mechanisms modulating the close family member RBL2/p130.
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Affiliation(s)
- Elisa Ventura
- Sbarro Institute for Cancer Research and Molecular Medicine, Center for Biotechnology, College of Science and Technology, Temple University, Philadelphia, PA 19122, USA; (E.V.); (A.G.)
| | - Carmelina Antonella Iannuzzi
- Cell Biology and Biotherapy Unit, Istituto Nazionale Tumori, IRCCS, Fondazione G. Pascale, I-80131 Napoli, Italy; (C.A.I.); (F.P.)
| | - Francesca Pentimalli
- Cell Biology and Biotherapy Unit, Istituto Nazionale Tumori, IRCCS, Fondazione G. Pascale, I-80131 Napoli, Italy; (C.A.I.); (F.P.)
| | - Antonio Giordano
- Sbarro Institute for Cancer Research and Molecular Medicine, Center for Biotechnology, College of Science and Technology, Temple University, Philadelphia, PA 19122, USA; (E.V.); (A.G.)
- Department of Medical Biotechnologies, University of Siena, I-53100 Siena, Italy
| | - Andrea Morrione
- Sbarro Institute for Cancer Research and Molecular Medicine, Center for Biotechnology, College of Science and Technology, Temple University, Philadelphia, PA 19122, USA; (E.V.); (A.G.)
- Correspondence: ; Tel.: +215-204-2450
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10
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Dudek M, Angelucci C, Pathiranage D, Wang P, Mallikarjun V, Lawless C, Swift J, Kadler KE, Boot-Handford RP, Hoyland JA, Lamande SR, Bateman JF, Meng QJ. Circadian time series proteomics reveals daily dynamics in cartilage physiology. Osteoarthritis Cartilage 2021; 29:739-749. [PMID: 33610821 PMCID: PMC8113022 DOI: 10.1016/j.joca.2021.02.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 01/28/2021] [Accepted: 02/08/2021] [Indexed: 02/02/2023]
Abstract
OBJECTIVE Cartilage in joints such as the hip and knee experiences repeated phases of heavy loading and low load recovery during the 24-h day/night cycle. Our previous work has shown 24 h rhythmic changes in gene expression at transcript level between night and day in wild type mouse cartilage which is lost in a circadian clock knock-out mouse model. However, it remains unknown to what extent circadian rhythms also regulate protein level gene expression in this matrix rich tissue. METHODS We investigated daily changes of protein abundance in mouse femoral head articular cartilage by performing a 48-h time-series LC-MS/MS analysis. RESULTS Out of the 1,177 proteins we identified across all time points, 145 proteins showed rhythmic changes in their abundance within the femoral head cartilage. Among these were molecules that have been implicated in key cartilage functions, including CTGF, MATN1, PAI-1 and PLOD1 & 2. Pathway analysis revealed that protein synthesis, cytoskeleton and glucose metabolism exhibited time-of-day dependent functions. Analysis of published cartilage proteomics datasets revealed that a significant portion of rhythmic proteins were dysregulated in osteoarthritis and/or ageing. CONCLUSIONS Our circadian proteomics study reveals that articular cartilage is a much more dynamic tissue than previously thought, with chondrocytes driving circadian rhythms not only in gene transcription but also in protein abundance. Our results clearly call for the consideration of circadian timing mechanisms not only in cartilage biology, but also in the pathogenesis, treatment strategies and biomarker detection in osteoarthritis.
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Affiliation(s)
- M Dudek
- Wellcome Centre for Cell Matrix Research, Division of Cell Matrix Biology and Regenerative Medicine, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Oxford Road, Manchester, UK
| | - C Angelucci
- Murdoch Children's Research Institute and University of Melbourne, Parkville, Victoria, Australia
| | - D Pathiranage
- Wellcome Centre for Cell Matrix Research, Division of Cell Matrix Biology and Regenerative Medicine, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Oxford Road, Manchester, UK
| | - P Wang
- Division of Cell Matrix Biology and Regenerative Medicine, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester, UK
| | - V Mallikarjun
- Wellcome Centre for Cell Matrix Research, Division of Cell Matrix Biology and Regenerative Medicine, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Oxford Road, Manchester, UK
| | - C Lawless
- Wellcome Centre for Cell Matrix Research, Division of Cell Matrix Biology and Regenerative Medicine, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Oxford Road, Manchester, UK
| | - J Swift
- Wellcome Centre for Cell Matrix Research, Division of Cell Matrix Biology and Regenerative Medicine, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Oxford Road, Manchester, UK
| | - K E Kadler
- Wellcome Centre for Cell Matrix Research, Division of Cell Matrix Biology and Regenerative Medicine, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Oxford Road, Manchester, UK
| | - R P Boot-Handford
- Wellcome Centre for Cell Matrix Research, Division of Cell Matrix Biology and Regenerative Medicine, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Oxford Road, Manchester, UK
| | - J A Hoyland
- Division of Cell Matrix Biology and Regenerative Medicine, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester, UK; NIHR Manchester Biomedical Research Centre, Central Manchester Foundation Trust, Manchester Academic Health Science Centre, Manchester, United Kingdom
| | - S R Lamande
- Murdoch Children's Research Institute and University of Melbourne, Parkville, Victoria, Australia
| | - J F Bateman
- Murdoch Children's Research Institute and University of Melbourne, Parkville, Victoria, Australia
| | - Q-J Meng
- Wellcome Centre for Cell Matrix Research, Division of Cell Matrix Biology and Regenerative Medicine, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Oxford Road, Manchester, UK.
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11
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Zhao Z, Kurimchak A, Nikonova AS, Feiser F, Wasserman JS, Fowle H, Varughese T, Connors M, Johnson K, Makhov P, Lindskog C, Kolenko VM, Golemis EA, Duncan JS, Graña X. PPP2R2A prostate cancer haploinsufficiency is associated with worse prognosis and a high vulnerability to B55α/PP2A reconstitution that triggers centrosome destabilization. Oncogenesis 2019; 8:72. [PMID: 31822657 PMCID: PMC6904742 DOI: 10.1038/s41389-019-0180-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Revised: 11/18/2019] [Accepted: 11/20/2019] [Indexed: 12/12/2022] Open
Abstract
The PPP2R2A gene encodes the B55α regulatory subunit of PP2A. Here, we report that PPP2R2A is hemizygously lost in ~42% of prostate adenocarcinomas, correlating with reduced expression, poorer prognosis, and an increased incidence of hemizygous loss (>75%) in metastatic disease. Of note, PPP2R2A homozygous loss is less common (5%) and not increased at later tumor stages. Reduced expression of B55α is also seen in prostate tumor tissue and cell lines. Consistent with the possibility that complete loss of PPP2R2A is detrimental in prostate tumors, PPP2R2A deletion in cells with reduced but present B55α reduces cell proliferation by slowing progression through the cell cycle. Remarkably, B55α-low cells also appear addicted to lower B55α expression, as even moderate increases in B55α expression are toxic. Reconstitution of B55α expression in prostate cancer (PCa) cell lines with low B55α expression reduces proliferation, inhibits transformation and blocks xenograft tumorigenicity. Mechanistically, we show B55α reconstitution reduces phosphorylation of proteins essential for centrosomal maintenance, and induces centrosome collapse and chromosome segregation failure; a first reported link between B55α/PP2A and the vertebrate centrosome. These effects are dependent on a prolonged metaphase/anaphase checkpoint and are lethal to PCa cells addicted to low levels of B55α. Thus, we propose the reduction in B55α levels associated with hemizygous loss is necessary for centrosomal integrity in PCa cells, leading to selective lethality of B55α reconstitution. Such a vulnerability could be targeted therapeutically in the large pool of patients with hemizygous PPP2R2A deletions, using pharmacologic approaches that enhance PP2A/B55α activity.
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Affiliation(s)
- Ziran Zhao
- Fels Institute for Cancer Research and Molecular Biology, Temple University Lewis Katz School of Medicine, Philadelphia, PA, 19140, USA
| | - Alison Kurimchak
- Fels Institute for Cancer Research and Molecular Biology, Temple University Lewis Katz School of Medicine, Philadelphia, PA, 19140, USA.,Fox Chase Cancer Center, Philadelphia, PA, 19111, USA
| | | | - Felicity Feiser
- Fels Institute for Cancer Research and Molecular Biology, Temple University Lewis Katz School of Medicine, Philadelphia, PA, 19140, USA
| | - Jason S Wasserman
- Fels Institute for Cancer Research and Molecular Biology, Temple University Lewis Katz School of Medicine, Philadelphia, PA, 19140, USA
| | - Holly Fowle
- Fels Institute for Cancer Research and Molecular Biology, Temple University Lewis Katz School of Medicine, Philadelphia, PA, 19140, USA
| | - Tinsa Varughese
- Fels Institute for Cancer Research and Molecular Biology, Temple University Lewis Katz School of Medicine, Philadelphia, PA, 19140, USA
| | - Megan Connors
- Fels Institute for Cancer Research and Molecular Biology, Temple University Lewis Katz School of Medicine, Philadelphia, PA, 19140, USA
| | | | - Petr Makhov
- Fox Chase Cancer Center, Philadelphia, PA, 19111, USA
| | - Cecilia Lindskog
- Department of Immunology, Genetics and Pathology, Uppsala University, 752 36, Uppsala, Sweden
| | | | | | | | - Xavier Graña
- Fels Institute for Cancer Research and Molecular Biology, Temple University Lewis Katz School of Medicine, Philadelphia, PA, 19140, USA.
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12
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Xin Y, Malick A, Hu M, Liu C, Batah H, Xu H, Duan C. Cell-autonomous regulation of epithelial cell quiescence by calcium channel Trpv6. eLife 2019; 8:48003. [PMID: 31526479 PMCID: PMC6764821 DOI: 10.7554/elife.48003] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Accepted: 09/13/2019] [Indexed: 12/14/2022] Open
Abstract
Epithelial homeostasis and regeneration require a pool of quiescent cells. How the quiescent cells are established and maintained is poorly understood. Here, we report that Trpv6, a cation channel responsible for epithelial Ca2+ absorption, functions as a key regulator of cellular quiescence. Genetic deletion and pharmacological blockade of Trpv6 promoted zebrafish epithelial cells to exit from quiescence and re-enter the cell cycle. Reintroducing Trpv6, but not its channel dead mutant, restored the quiescent state. Ca2+ imaging showed that Trpv6 is constitutively open in vivo. Mechanistically, Trpv6-mediated Ca2+ influx maintained the quiescent state by suppressing insulin-like growth factor (IGF)-mediated Akt-Tor and Erk signaling. In zebrafish epithelia and human colon carcinoma cells, Trpv6/TRPV6 elevated intracellular Ca2+ levels and activated PP2A, which down-regulated IGF signaling and promoted the quiescent state. Our findings suggest that Trpv6 mediates constitutive Ca2+ influx into epithelial cells to continuously suppress growth factor signaling and maintain the quiescent state.
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Affiliation(s)
- Yi Xin
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Allison Malick
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Meiqin Hu
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Chengdong Liu
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Heya Batah
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Haoxing Xu
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Cunming Duan
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, United States
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13
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Nagaprashantha LD, Singhal J, Chikara S, Gugiu G, Horne D, Awasthi S, Salgia R, Singhal SS. 2′-Hydroxyflavanone induced changes in the proteomic profile of breast cancer cells. J Proteomics 2019; 192:233-245. [DOI: 10.1016/j.jprot.2018.09.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Revised: 09/03/2018] [Accepted: 09/10/2018] [Indexed: 12/12/2022]
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14
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Abstract
Fibroblast growth factors (FGFs) and their receptors (FGFRs) are expressed throughout all stages of skeletal development. In the limb bud and in cranial mesenchyme, FGF signaling is important for formation of mesenchymal condensations that give rise to bone. Once skeletal elements are initiated and patterned, FGFs regulate both endochondral and intramembranous ossification programs. In this chapter, we review functions of the FGF signaling pathway during these critical stages of skeletogenesis, and explore skeletal malformations in humans that are caused by mutations in FGF signaling molecules.
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Affiliation(s)
- David M Ornitz
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, United States.
| | - Pierre J Marie
- UMR-1132 Inserm (Institut national de la Santé et de la Recherche Médicale) and University Paris Diderot, Sorbonne Paris Cité, Hôpital Lariboisière, Paris, France
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15
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Fowle H, Zhao Z, Graña X. PP2A holoenzymes, substrate specificity driving cellular functions and deregulation in cancer. Adv Cancer Res 2019; 144:55-93. [PMID: 31349904 PMCID: PMC9994639 DOI: 10.1016/bs.acr.2019.03.009] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
PP2A is a highly conserved eukaryotic serine/threonine protein phosphatase of the PPP family of phosphatases with fundamental cellular functions. In cells, PP2A targets specific subcellular locations and substrates by forming heterotrimeric holoenzymes, where a core dimer consisting of scaffold (A) and catalytic (C) subunits complexes with one of many B regulatory subunits. PP2A plays a key role in positively and negatively regulating a myriad of cellular processes, as it targets a very sizable fraction of the cellular substrates phosphorylated on Ser/Thr residues. This review focuses on insights made toward the understanding on how the subunit composition and structure of PP2A holoenzymes mediates substrate specificity, the role of substrate modulation in the signaling of cellular division, growth, and differentiation, and its deregulation in cancer.
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Affiliation(s)
- Holly Fowle
- Fels Institute for Cancer Research and Molecular Biology and Temple University Lewis Katz School of Medicine, Philadelphia, PA, United States
| | - Ziran Zhao
- Fels Institute for Cancer Research and Molecular Biology and Temple University Lewis Katz School of Medicine, Philadelphia, PA, United States
| | - Xavier Graña
- Fels Institute for Cancer Research and Molecular Biology and Temple University Lewis Katz School of Medicine, Philadelphia, PA, United States.
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16
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Meeusen B, Janssens V. Tumor suppressive protein phosphatases in human cancer: Emerging targets for therapeutic intervention and tumor stratification. Int J Biochem Cell Biol 2017; 96:98-134. [PMID: 29031806 DOI: 10.1016/j.biocel.2017.10.002] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2017] [Revised: 10/04/2017] [Accepted: 10/05/2017] [Indexed: 02/06/2023]
Abstract
Aberrant protein phosphorylation is one of the hallmarks of cancer cells, and in many cases a prerequisite to sustain tumor development and progression. Like protein kinases, protein phosphatases are key regulators of cell signaling. However, their contribution to aberrant signaling in cancer cells is overall less well appreciated, and therefore, their clinical potential remains largely unexploited. In this review, we provide an overview of tumor suppressive protein phosphatases in human cancer. Along their mechanisms of inactivation in defined cancer contexts, we give an overview of their functional roles in diverse signaling pathways that contribute to their tumor suppressive abilities. Finally, we discuss their emerging roles as predictive or prognostic markers, their potential as synthetic lethality targets, and the current feasibility of their reactivation with pharmacologic compounds as promising new cancer therapies. We conclude that their inclusion in clinical practice has obvious potential to significantly improve therapeutic outcome in various ways, and should now definitely be pushed forward.
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Affiliation(s)
- Bob Meeusen
- Laboratory of Protein Phosphorylation & Proteomics, Dept. of Cellular & Molecular Medicine, Faculty of Medicine, KU Leuven & Leuven Cancer Institute (LKI), KU Leuven, Belgium
| | - Veerle Janssens
- Laboratory of Protein Phosphorylation & Proteomics, Dept. of Cellular & Molecular Medicine, Faculty of Medicine, KU Leuven & Leuven Cancer Institute (LKI), KU Leuven, Belgium.
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17
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Karuppaiah K, Yu K, Lim J, Chen J, Smith C, Long F, Ornitz DM. FGF signaling in the osteoprogenitor lineage non-autonomously regulates postnatal chondrocyte proliferation and skeletal growth. Development 2016; 143:1811-22. [PMID: 27052727 DOI: 10.1242/dev.131722] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Accepted: 03/18/2016] [Indexed: 12/22/2022]
Abstract
Fibroblast growth factor (FGF) signaling is important for skeletal development; however, cell-specific functions, redundancy and feedback mechanisms regulating bone growth are poorly understood. FGF receptors 1 and 2 (Fgfr1 and Fgfr2) are both expressed in the osteoprogenitor lineage. Double conditional knockout mice, in which both receptors were inactivated using an osteoprogenitor-specific Cre driver, appeared normal at birth; however, these mice showed severe postnatal growth defects that include an ∼50% reduction in body weight and bone mass, and impaired longitudinal bone growth. Histological analysis showed reduced cortical and trabecular bone, suggesting cell-autonomous functions of FGF signaling during postnatal bone formation. Surprisingly, the double conditional knockout mice also showed growth plate defects and an arrest in chondrocyte proliferation. We provide genetic evidence of a non-cell-autonomous feedback pathway regulating Fgf9, Fgf18 and Pthlh expression, which led to increased expression and signaling of Fgfr3 in growth plate chondrocytes and suppression of chondrocyte proliferation. These observations show that FGF signaling in the osteoprogenitor lineage is obligately coupled to chondrocyte proliferation and the regulation of longitudinal bone growth.
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Affiliation(s)
- Kannan Karuppaiah
- Department of Developmental Biology, Washington University School of Medicine, St Louis, MO 63110, USA
| | - Kai Yu
- Department of Developmental Biology, Washington University School of Medicine, St Louis, MO 63110, USA Division of Craniofacial Medicine, Department of Pediatrics, University of Washington and Center for Developmental Biology and Regenerative Medicine, Seattle Children's Research Institute, Seattle, WA 98101, USA
| | - Joohyun Lim
- Departments of Orthopaedic Surgery and Medicine, Washington University School of Medicine, St Louis, MO 63110, USA
| | - Jianquan Chen
- Departments of Orthopaedic Surgery and Medicine, Washington University School of Medicine, St Louis, MO 63110, USA
| | - Craig Smith
- Department of Developmental Biology, Washington University School of Medicine, St Louis, MO 63110, USA
| | - Fanxin Long
- Departments of Orthopaedic Surgery and Medicine, Washington University School of Medicine, St Louis, MO 63110, USA
| | - David M Ornitz
- Department of Developmental Biology, Washington University School of Medicine, St Louis, MO 63110, USA
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18
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Kurimchak A, Graña X. PP2A: more than a reset switch to activate pRB proteins during the cell cycle and in response to signaling cues. Cell Cycle 2015; 14:18-30. [PMID: 25483052 PMCID: PMC4612414 DOI: 10.4161/15384101.2014.985069] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
In their active hypophosphorylated state, members of the retinoblastoma family of pocket proteins negatively regulate cell cycle progression at least in part by repressing expression of E2F-dependent genes. Mitogen-dependent activation of G1 and G1/S Cyclin Dependent Kinases (CDKs) results in coordinated hyperphosphorylation and inactivation of these proteins, which no longer bind and repress E2Fs. S and G2/M CDKs maintain pocket protein hyperphosphorylated through the end of mitosis. The inactivating action of inducible CDKs is opposed by the Ser/Thr protein phosphatases PP2A and PP1. Various trimeric PP2A holoenzymes have been implicated in dephosphorylation of pocket proteins in response to specific cellular signals and stresses or as part of an equilibrium with CDKs throughout the cell cycle. PP1 has specifically been implicated in dephosphorylation of pRB in late mitosis and early G1. This review is particularly focused on the emerging role of PP2A as a major hub for integration of growth suppressor signals that require rapid inactivation of pocket proteins. Of note, activation of particular PP2A holoenzymes triggers differential activation of pocket proteins in the presence of active CDKs.
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Affiliation(s)
- Alison Kurimchak
- a Fels Institute for Cancer Research and Molecular Biology and Department of Biochemistry; Temple University School of Medicine ; Philadelphia , PA USA
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19
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Sun D, Buttitta L. Protein phosphatase 2A promotes the transition to G0 during terminal differentiation in Drosophila. Development 2015; 142:3033-45. [PMID: 26253406 DOI: 10.1242/dev.120824] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Accepted: 07/28/2015] [Indexed: 12/22/2022]
Abstract
Protein phosphatase type 2A complex (PP2A) has been known as a tumor suppressor for over two decades, but it remains unclear exactly how it suppresses tumor growth. Here, we provide data indicating a novel role for PP2A in promoting the transition to quiescence upon terminal differentiation in vivo. Using Drosophila eyes and wings as a model, we find that compromising PP2A activity during the final cell cycle prior to a developmentally controlled cell cycle exit leads to extra cell divisions and delays entry into quiescence. By systematically testing the regulatory subunits of Drosophila PP2A, we find that the B56 family member widerborst (wdb) is required for the role of PP2A in promoting the transition to quiescence. Cells in differentiating tissues with compromised PP2A retain high Cdk2 activity when they should be quiescent, and genetic epistasis tests demonstrate that ectopic Cyclin E/Cdk2 activity is responsible for the extra cell cycles caused by PP2A inhibition. The loss of wdb/PP2A function cooperates with aberrantly high Cyclin E protein levels, allowing cells to bypass a robust G0 late in development. This provides an example of how loss of PP2A can cooperate with oncogenic mutations in cancer. We propose that the PP2A complex plays a novel role in differentiating tissues to promote developmentally controlled quiescence through the regulation of Cyclin E/Cdk2 activity.
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Affiliation(s)
- Dan Sun
- University of Michigan, Department of Molecular, Cellular and Developmental Biology, Ann Arbor, MI 48109, USA
| | - Laura Buttitta
- University of Michigan, Department of Molecular, Cellular and Developmental Biology, Ann Arbor, MI 48109, USA
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20
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Abstract
Fibroblast growth factor (FGF) signaling pathways are essential regulators of vertebrate skeletal development. FGF signaling regulates development of the limb bud and formation of the mesenchymal condensation and has key roles in regulating chondrogenesis, osteogenesis, and bone and mineral homeostasis. This review updates our review on FGFs in skeletal development published in Genes & Development in 2002, examines progress made on understanding the functions of the FGF signaling pathway during critical stages of skeletogenesis, and explores the mechanisms by which mutations in FGF signaling molecules cause skeletal malformations in humans. Links between FGF signaling pathways and other interacting pathways that are critical for skeletal development and could be exploited to treat genetic diseases and repair bone are also explored.
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Affiliation(s)
- David M Ornitz
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | - Pierre J Marie
- UMR-1132, Institut National de la Santé et de la Recherche Médicale, Hopital Lariboisiere, 75475 Paris Cedex 10, France; Université Paris Diderot, Sorbonne Paris Cité, 75475 Paris Cedex 10, France
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21
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Li X, Chen J, Liang W, Li H, Liu F, Weng X, Lin P, Chen W, Zheng C, Xu H, Liu X, Ye H. Bushen Zhuangjin Decoction promotes chondrocyte proliferation by stimulating cell cycle progression. Exp Ther Med 2015; 9:839-844. [PMID: 25667638 PMCID: PMC4316974 DOI: 10.3892/etm.2015.2214] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2014] [Accepted: 01/13/2015] [Indexed: 11/24/2022] Open
Abstract
Bushen Zhuangjin Decoction (BZD), a well-known formulation in Traditional Chinese Medicine, has been widely used for the treatment of osteoarthritis (OA). Due to the poor intrinsic repair capacity of chondrocytes, promoting the proliferation of chondrocytes is an efficient treatment to delay the progression of cartilage degradation. The present study, therefore, focused on the effect of BZD on chondrocyte proliferation, exploring the mechanism of BZD on the inhibition of cartilage degradation. Chondrocytes isolated from the knee articular cartilage of Sprague Dawley rats were cultured and identified by type II collagen immunohistochemistry. It was found that BZD promoted chondrocyte viability in a dose- and time-dependent manner. To investigate if BZD promoted the chondrocyte viability by stimulating the cell cycle progression a flow cytometer was used, and the results showed that the percentage proportion of G0/G1 cells was significantly lower, and the percentage proportion of S cells was significantly higher, in treated cells compared with that in untreated cells. To gain insight into the mechanism underlying the effect of BZD on the cell cycle progression, the mRNA and protein expression of cyclin D1, cyclin-dependent kinase 4 (CDK4), CDK6 and p21 was measured by reverse transcription-polymerase chain reaction and western blotting, respectively. The mRNA and protein expression of cyclin D1, CDK4 and CDK6 in the BZD-treated chondrocytes was significantly upregulated, while the mRNA and protein expression of p21 was significantly downregulated, compared with that in the untreated chondrocytes. These results suggested that BZD promoted chondrocyte proliferation by accelerating G1/S transition, indicating that BZD is a potential therapeutic agent for the treatment of OA.
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Affiliation(s)
- Xihai Li
- Academy of Integrative Medicine, Fujian University of Traditional Chinese Medicine, Fuzhou, Fujian 350122, P.R. China
| | - Jiashou Chen
- Academy of Integrative Medicine, Fujian University of Traditional Chinese Medicine, Fuzhou, Fujian 350122, P.R. China
| | - Wenna Liang
- Research Base of Traditional Chinese Medicine Syndrome, Fujian University of Traditional Chinese Medicine, Fuzhou, Fujian 350122, P.R. China
| | - Huiting Li
- Fujian Key Laboratory of Integrative Medicine on Geriatrics, Fujian University of Traditional Chinese Medicine, Fuzhou, Fujian 350122, P.R. China
| | - Fayuan Liu
- Academy of Integrative Medicine, Fujian University of Traditional Chinese Medicine, Fuzhou, Fujian 350122, P.R. China
| | - Xiaping Weng
- Academy of Integrative Medicine, Fujian University of Traditional Chinese Medicine, Fuzhou, Fujian 350122, P.R. China
| | - Pingdong Lin
- Fujian Key Laboratory of Integrative Medicine on Geriatrics, Fujian University of Traditional Chinese Medicine, Fuzhou, Fujian 350122, P.R. China
| | - Wenlie Chen
- Academy of Integrative Medicine, Fujian University of Traditional Chinese Medicine, Fuzhou, Fujian 350122, P.R. China
| | - Chunsong Zheng
- Academy of Integrative Medicine, Fujian University of Traditional Chinese Medicine, Fuzhou, Fujian 350122, P.R. China
| | - Huifeng Xu
- Academy of Integrative Medicine, Fujian University of Traditional Chinese Medicine, Fuzhou, Fujian 350122, P.R. China
| | - Xianxiang Liu
- Academy of Integrative Medicine, Fujian University of Traditional Chinese Medicine, Fuzhou, Fujian 350122, P.R. China
| | - Hongzhi Ye
- Academy of Integrative Medicine, Fujian University of Traditional Chinese Medicine, Fuzhou, Fujian 350122, P.R. China
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22
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Matta C, Mobasheri A, Gergely P, Zákány R. Ser/Thr-phosphoprotein phosphatases in chondrogenesis: neglected components of a two-player game. Cell Signal 2014; 26:2175-85. [PMID: 25007994 DOI: 10.1016/j.cellsig.2014.06.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Accepted: 06/27/2014] [Indexed: 12/13/2022]
Abstract
Protein phosphorylation plays a determining role in the regulation of chondrogenesis in vitro. While signalling pathways governed by protein kinases including PKA, PKC, and mitogen-activated protein kinases (MAPK) have been mapped in great details, published data relating to the specific role of phosphoprotein phosphatases (PPs) in differentiating chondroprogenitor cells or in mature chondrocytes is relatively sparse. This review discusses the known functions of Ser/Thr-specific PPs in the molecular signalling pathways of chondrogenesis. PPs are clearly equally important as protein kinases to counterbalance the effect of reversible protein phosphorylation. Of the main Ser/Thr PPs, some of the functions of PP1, PP2A and PP2B have been characterised in the context of chondrogenesis. While PP1 and PP2A appear to negatively regulate chondrogenic differentiation and maintenance of chondrocyte phenotype, calcineurin is an important stimulatory mediator during chondrogenesis but becomes inhibitory in mature chondrocytes. Furthermore, PPs are implicated to be mediators during the pathogenesis of osteoarthritis that makes them potential therapeutic targets to be exploited in the close future. Among the many yet unexplored targets of PPs, modulation of plasma membrane ion channel function and participation in mechanotransduction pathways are emerging novel aspects of signalling during chondrogenesis that should be further elucidated. Besides the regulation of cellular ion homeostasis, other potentially significant novel roles for PPs during the regulation of in vitro chondrogenesis are discussed.
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Affiliation(s)
- Csaba Matta
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, Nagyerdei krt. 98, H-4032, Debrecen, Hungary; School of Veterinary Medicine, Faculty of Health and Medical Sciences, University of Surrey, Duke of Kent Building, Guildford, Surrey GU2 7XH, United Kingdom.
| | - Ali Mobasheri
- School of Veterinary Medicine, Faculty of Health and Medical Sciences, University of Surrey, Duke of Kent Building, Guildford, Surrey GU2 7XH, United Kingdom; Arthritis Research UK Centre for Sport, Exercise and Osteoarthritis, Arthritis Research UK Pain Centre, Medical Research Council and Arthritis Research UK Centre for Musculoskeletal Ageing Research, University of Nottingham, Queen's Medical Centre, Nottingham, NG7 2UH, United Kingdom; Center of Excellence in Genomic Medicine Research (CEGMR), King Fahd Medical Research Center (KFMRC), King AbdulAziz University, Jeddah, 21589, Kingdom of Saudi Arabia
| | - Pál Gergely
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Nagyerdei krt. 98, H-4032, Debrecen, Hungary
| | - Róza Zákány
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, Nagyerdei krt. 98, H-4032, Debrecen, Hungary
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23
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Abstract
Mammalian DREAM is a conserved protein complex that functions in cellular quiescence. DREAM contains an E2F, a retinoblastoma (RB)-family protein, and the MuvB core (LIN9, LIN37, LIN52, LIN54, and RBBP4). In mammals, MuvB can alternatively bind to BMYB to form a complex that promotes mitotic gene expression. Because BMYB-MuvB is essential for proliferation, loss-of-function approaches to study MuvB have generated limited insight into DREAM function. Here, we report a gene-targeted mouse model that is uniquely deficient for DREAM complex assembly. We have targeted p107 (Rbl1) to prevent MuvB binding and combined it with deficiency for p130 (Rbl2). Our data demonstrate that cells from these mice preferentially assemble BMYB-MuvB complexes and fail to repress transcription. DREAM-deficient mice show defects in endochondral bone formation and die shortly after birth. Micro-computed tomography and histology demonstrate that in the absence of DREAM, chondrocytes fail to arrest proliferation. Since DREAM requires DYRK1A (dual-specificity tyrosine phosphorylation-regulated protein kinase 1A) phosphorylation of LIN52 for assembly, we utilized an embryonic bone culture system and pharmacologic inhibition of (DYRK) kinase to demonstrate a similar defect in endochondral bone growth. This reveals that assembly of mammalian DREAM is required to induce cell cycle exit in chondrocytes.
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24
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Mui MZ, Kucharski M, Miron MJ, Hur WS, Berghuis AM, Blanchette P, Branton PE. Identification of the adenovirus E4orf4 protein binding site on the B55α and Cdc55 regulatory subunits of PP2A: Implications for PP2A function, tumor cell killing and viral replication. PLoS Pathog 2013; 9:e1003742. [PMID: 24244166 PMCID: PMC3828177 DOI: 10.1371/journal.ppat.1003742] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2013] [Accepted: 09/18/2013] [Indexed: 11/18/2022] Open
Abstract
Adenovirus E4orf4 protein induces the death of human cancer cells and Saccharomyces cerevisiae. Binding of E4orf4 to the B/B55/Cdc55 regulatory subunit of protein phosphatase 2A (PP2A) is required, and such binding inhibits PP2AB55 activity leading to dose-dependent cell death. We found that E4orf4 binds across the putative substrate binding groove predicted from the crystal structure of B55α such that the substrate p107 can no longer interact with PP2AB55α. We propose that E4orf4 inhibits PP2AB55 activity by preventing access of substrates and that at high E4orf4 levels this inhibition results in cell death through the failure to dephosphorylate substrates required for cell cycle progression. However, E4orf4 is expressed at much lower and less toxic levels during a normal adenovirus infection. We suggest that in this context E4orf4 largely serves to recruit novel substrates such as ASF/SF2/SRSF1 to PP2AB55 to enhance adenovirus replication. Thus E4orf4 toxicity probably represents an artifact of overexpression and does not reflect the evolutionary function of this viral product. The adenovirus E4orf4 protein when expressed alone at high levels induces the death of human cancer cells but not normal primary cells. It also is toxic in the yeast Saccharomyces cerevisiae, which we have used as a model system in some studies. Toxicity induced by the E4orf4 protein is largely dependent on its ability to associate with the highly conserved B/B55/Cdc55 class of regulatory subunits of protein phosphatase 2A (PP2A), of which the mammalian B55α species is best characterized structurally. We showed previously that binding to B55α appears to inhibit PP2A activity against at least some substrates. In the present study, we mapped the E4orf4 binding site on both yeast Cdc55 and mammalian B55α and propose how such binding may inhibit PP2A activity. The implications of E4orf4 binding on PP2A activity are of significant scientific interest in terms of the process by which PP2A recognizes and dephosphorylates its substrates. We also propose that E4orf4 binding in the context of viral replication serves the quite different function of introducing novel substrates for dephosphorylation by the PP2A holoenzyme.
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Affiliation(s)
- Melissa Z. Mui
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
| | - Michael Kucharski
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
| | | | - Woosuk Steve Hur
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
| | | | - Paola Blanchette
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
| | - Philip E. Branton
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
- Department of Oncology, McGill University, Montreal, Quebec, Canada
- The Rosalind and Morris Goodman Cancer Research Centre, McGill University, Montreal, Quebec, Canada
- * E-mail:
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