1
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Wachter F, Nowak RP, Ficarro S, Marto J, Fischer ES. Structural characterization of methylation-independent PP2A assembly guides alphafold2Multimer prediction of family-wide PP2A complexes. J Biol Chem 2024; 300:107268. [PMID: 38582449 PMCID: PMC11087950 DOI: 10.1016/j.jbc.2024.107268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 03/31/2024] [Accepted: 04/02/2024] [Indexed: 04/08/2024] Open
Abstract
Dysregulation of phosphorylation-dependent signaling is a hallmark of tumorigenesis. Protein phosphatase 2 (PP2A) is an essential regulator of cell growth. One scaffold subunit (A) binds to a catalytic subunit (C) to form a core AC heterodimer, which together with one of many regulatory (B) subunits forms the active trimeric enzyme. The combinatorial number of distinct PP2A complexes is large, which results in diverse substrate specificity and subcellular localization. The detailed mechanism of PP2A assembly and regulation remains elusive and reports about an important role of methylation of the carboxy terminus of PP2A C are conflicting. A better understanding of the molecular underpinnings of PP2A assembly and regulation is critical to dissecting PP2A function in physiology and disease. Here, we combined biochemical reconstitution, mass spectrometry, X-ray crystallography, and functional assays to characterize the assembly of trimeric PP2A. In vitro studies demonstrated that methylation of the carboxy-terminus of PP2A C was dispensable for PP2A assembly in vitro. To corroborate these findings, we determined the X-ray crystal structure of the unmethylated PP2A Aα-B56ε-Cα trimer complex to 3.1 Å resolution. The experimental structure superimposed well with an Alphafold2Multimer prediction of the PP2A trimer. We then predicted models of all canonical PP2A complexes providing a framework for structural analysis of PP2A. In conclusion, methylation was dispensable for trimeric PP2A assembly and integrative structural biology studies of PP2A offered predictive models for all canonical PP2A complexes.
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Affiliation(s)
- Franziska Wachter
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA; Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, USA
| | - Radosław P Nowak
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, USA
| | - Scott Ficarro
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA
| | - Jarrod Marto
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA
| | - Eric S Fischer
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, USA.
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2
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Padi SKR, Vos MR, Godek RJ, Fuller JR, Kruse T, Hein JB, Nilsson J, Kelker MS, Page R, Peti W. Cryo-EM structures of PP2A:B55-FAM122A and PP2A:B55-ARPP19. Nature 2024; 625:195-203. [PMID: 38123684 PMCID: PMC10765524 DOI: 10.1038/s41586-023-06870-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Accepted: 11/15/2023] [Indexed: 12/23/2023]
Abstract
Progression through the cell cycle is controlled by regulated and abrupt changes in phosphorylation1. Mitotic entry is initiated by increased phosphorylation of mitotic proteins, a process driven by kinases2, whereas mitotic exit is achieved by counteracting dephosphorylation, a process driven by phosphatases, especially PP2A:B553. Although the role of kinases in mitotic entry is well established, recent data have shown that mitosis is only successfully initiated when the counterbalancing phosphatases are also inhibited4. Inhibition of PP2A:B55 is achieved by the intrinsically disordered proteins ARPP195,6 and FAM122A7. Despite their critical roles in mitosis, the mechanisms by which they achieve PP2A:B55 inhibition is unknown. Here, we report the single-particle cryo-electron microscopy structures of PP2A:B55 bound to phosphorylated ARPP19 and FAM122A. Consistent with our complementary NMR spectroscopy studies, both intrinsically disordered proteins bind PP2A:B55, but do so in highly distinct manners, leveraging multiple distinct binding sites on B55. Our extensive structural, biophysical and biochemical data explain how substrates and inhibitors are recruited to PP2A:B55 and provide a molecular roadmap for the development of therapeutic interventions for PP2A:B55-related diseases.
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Affiliation(s)
- Sathish K R Padi
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT, USA
| | - Margaret R Vos
- Department of Cell Biology, University of Connecticut Health Center, Farmington, CT, USA
| | - Rachel J Godek
- Department of Cell Biology, University of Connecticut Health Center, Farmington, CT, USA
| | | | - Thomas Kruse
- The Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Copenhagen, Denmark
| | - Jamin B Hein
- The Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Copenhagen, Denmark
| | - Jakob Nilsson
- The Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Copenhagen, Denmark
| | | | - Rebecca Page
- Department of Cell Biology, University of Connecticut Health Center, Farmington, CT, USA.
| | - Wolfgang Peti
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT, USA.
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3
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Padi SK, Vos MR, Godek RJ, Fuller JR, Kruse T, Hein JB, Nilsson J, Kelker MS, Page R, Peti W. Cryo-EM structures of PP2A:B55-FAM122A and PP2A:B55-ARPP19. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.31.555365. [PMID: 37693408 PMCID: PMC10491220 DOI: 10.1101/2023.08.31.555365] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/12/2023]
Abstract
Progression through the cell cycle is controlled by regulated and abrupt changes in phosphorylation.1 Mitotic entry is initiated by increased phosphorylation of mitotic proteins, a process driven by kinases,2 while mitotic exit is achieved by counteracting dephosphorylation, a process driven by phosphatases, especially PP2A:B55.3 While the role of kinases in mitotic entry is well-established, recent data have shown that mitosis is only successfully initiated when the counterbalancing phosphatases are also inhibited.4 For PP2A:B55, inhibition is achieved by the two intrinsically disordered proteins (IDPs), ARPP19 (phosphorylation-dependent)6,7 and FAM122A5 (inhibition is phosphorylation-independent). Despite their critical roles in mitosis, the mechanisms by which they achieve PP2A:B55 inhibition is unknown. Here, we report the cryo-electron microscopy structures of PP2A:B55 bound to phosphorylated ARPP19 and FAM122A. Consistent with our complementary NMR spectroscopy studies both IDPs bind PP2A:B55, but do so in highly distinct manners, unexpectedly leveraging multiple distinct binding sites on B55. Our extensive structural, biophysical and biochemical data explain how substrates and inhibitors are recruited to PP2A:B55 and provides a molecular roadmap for the development of therapeutic interventions for PP2A:B55 related diseases.
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Affiliation(s)
- Sathish K.R. Padi
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, USA
| | - Margaret R. Vos
- Department of Cell Biology, University of Connecticut Health Center, Farmington, USA
| | - Rachel J. Godek
- Department of Cell Biology, University of Connecticut Health Center, Farmington, USA
| | | | - Thomas Kruse
- The Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Copenhagen, Denmark
| | - Jamin B. Hein
- The Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Copenhagen, Denmark
| | - Jakob Nilsson
- The Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Copenhagen, Denmark
| | | | - Rebecca Page
- Department of Cell Biology, University of Connecticut Health Center, Farmington, USA
| | - Wolfgang Peti
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, USA
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4
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Rasool RU, O'Connor CM, Das CK, Alhusayan M, Verma BK, Islam S, Frohner IE, Deng Q, Mitchell-Velasquez E, Sangodkar J, Ahmed A, Linauer S, Mudrak I, Rainey J, Zawacki KP, Suhan TK, Callahan CG, Rebernick R, Natesan R, Siddiqui J, Sauter G, Thomas D, Wang S, Taylor DJ, Simon R, Cieslik M, Chinnaiyan AM, Busino L, Ogris E, Narla G, Asangani IA. Loss of LCMT1 and biased protein phosphatase 2A heterotrimerization drive prostate cancer progression and therapy resistance. Nat Commun 2023; 14:5253. [PMID: 37644036 PMCID: PMC10465527 DOI: 10.1038/s41467-023-40760-6] [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: 01/03/2023] [Accepted: 08/09/2023] [Indexed: 08/31/2023] Open
Abstract
Loss of the tumor suppressive activity of the protein phosphatase 2A (PP2A) is associated with cancer, but the underlying molecular mechanisms are unclear. PP2A holoenzyme comprises a heterodimeric core, a scaffolding A subunit and a catalytic C subunit, and one of over 20 distinct substrate-directing regulatory B subunits. Methylation of the C subunit regulates PP2A heterotrimerization, affecting B subunit binding and substrate specificity. Here, we report that the leucine carboxy methyltransferase (LCMT1), which methylates the L309 residue of the C subunit, acts as a suppressor of androgen receptor (AR) addicted prostate cancer (PCa). Decreased methyl-PP2A-C levels in prostate tumors is associated with biochemical recurrence and metastasis. Silencing LCMT1 increases AR activity and promotes castration-resistant prostate cancer growth. LCMT1-dependent methyl-sensitive AB56αCme heterotrimers target AR and its critical coactivator MED1 for dephosphorylation, resulting in the eviction of the AR-MED1 complex from chromatin and loss of target gene expression. Mechanistically, LCMT1 is regulated by S6K1-mediated phosphorylation-induced degradation requiring the β-TRCP, leading to acquired resistance to anti-androgens. Finally, feedforward stabilization of LCMT1 by small molecule activator of phosphatase (SMAP) results in attenuation of AR-signaling and tumor growth inhibition in anti-androgen refractory PCa. These findings highlight methyl-PP2A-C as a prognostic marker and that the loss of LCMT1 is a major determinant in AR-addicted PCa, suggesting therapeutic potential for AR degraders or PP2A modulators in prostate cancer treatment.
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Affiliation(s)
- Reyaz Ur Rasool
- Department of Cancer Biology, Perelman School of Medicine, University of Pennsylvania, 421 Curie Boulevard, BRBII/III, Philadelphia, PA, 19104, USA
| | - Caitlin M O'Connor
- Division of Genetic Medicine, Department of Internal Medicine, University of Michigan, Ann Arbor, MI, 48105, USA
- Rogel Cancer Center, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Chandan Kanta Das
- Department of Cancer Biology, Perelman School of Medicine, University of Pennsylvania, 421 Curie Boulevard, BRBII/III, Philadelphia, PA, 19104, USA
| | - Mohammed Alhusayan
- Department of Cancer Biology, Perelman School of Medicine, University of Pennsylvania, 421 Curie Boulevard, BRBII/III, Philadelphia, PA, 19104, USA
| | - Brijesh Kumar Verma
- Department of Cancer Biology, Perelman School of Medicine, University of Pennsylvania, 421 Curie Boulevard, BRBII/III, Philadelphia, PA, 19104, USA
| | - Sehbanul Islam
- Department of Cancer Biology, Perelman School of Medicine, University of Pennsylvania, 421 Curie Boulevard, BRBII/III, Philadelphia, PA, 19104, USA
| | - Ingrid E Frohner
- Center for Medical Biochemistry, Max Perutz Labs, Medical University of Vienna, Dr. Bohr-Gasse 9/2, Vienna, 1030, Austria
| | - Qu Deng
- Department of Cancer Biology, Perelman School of Medicine, University of Pennsylvania, 421 Curie Boulevard, BRBII/III, Philadelphia, PA, 19104, USA
| | - Erick Mitchell-Velasquez
- Department of Cancer Biology, Perelman School of Medicine, University of Pennsylvania, 421 Curie Boulevard, BRBII/III, Philadelphia, PA, 19104, USA
| | - Jaya Sangodkar
- Division of Genetic Medicine, Department of Internal Medicine, University of Michigan, Ann Arbor, MI, 48105, USA
- Rogel Cancer Center, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Aqila Ahmed
- Division of Genetic Medicine, Department of Internal Medicine, University of Michigan, Ann Arbor, MI, 48105, USA
- Rogel Cancer Center, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Sarah Linauer
- Center for Medical Biochemistry, Max Perutz Labs, Medical University of Vienna, Dr. Bohr-Gasse 9/2, Vienna, 1030, Austria
| | - Ingrid Mudrak
- Center for Medical Biochemistry, Max Perutz Labs, Medical University of Vienna, Dr. Bohr-Gasse 9/2, Vienna, 1030, Austria
| | - Jessica Rainey
- Department of Cancer Biology, Perelman School of Medicine, University of Pennsylvania, 421 Curie Boulevard, BRBII/III, Philadelphia, PA, 19104, USA
| | - Kaitlin P Zawacki
- Division of Genetic Medicine, Department of Internal Medicine, University of Michigan, Ann Arbor, MI, 48105, USA
- Rogel Cancer Center, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Tahra K Suhan
- Division of Genetic Medicine, Department of Internal Medicine, University of Michigan, Ann Arbor, MI, 48105, USA
- Rogel Cancer Center, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Catherine G Callahan
- Division of Genetic Medicine, Department of Internal Medicine, University of Michigan, Ann Arbor, MI, 48105, USA
- Rogel Cancer Center, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Ryan Rebernick
- Department of Pathology and Rogel Cancer Center, University of Michigan Medical School, Ann Arbor, MI, USA
- Michigan Center for Translational Pathology, University of Michigan, Ann Arbor, MI, USA
| | - Ramakrishnan Natesan
- Department of Cancer Biology, Perelman School of Medicine, University of Pennsylvania, 421 Curie Boulevard, BRBII/III, Philadelphia, PA, 19104, USA
| | - Javed Siddiqui
- Department of Pathology and Rogel Cancer Center, University of Michigan Medical School, Ann Arbor, MI, USA
- Michigan Center for Translational Pathology, University of Michigan, Ann Arbor, MI, USA
| | - Guido Sauter
- Institute of Pathology, University Medical Center Hamburg-Eppendorf, 20246, Hamburg, Germany
| | - Dafydd Thomas
- Michigan Center for Translational Pathology, University of Michigan, Ann Arbor, MI, USA
| | - Shaomeng Wang
- Departments of Internal Medicine, Pharmacology, and Medicinal Chemistry, University of Michigan, Ann Arbor, MI, USA
| | - Derek J Taylor
- Department of Biochemistry Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA
| | - Ronald Simon
- Institute of Pathology, University Medical Center Hamburg-Eppendorf, 20246, Hamburg, Germany
| | - Marcin Cieslik
- Department of Pathology and Rogel Cancer Center, University of Michigan Medical School, Ann Arbor, MI, USA
- Michigan Center for Translational Pathology, University of Michigan, Ann Arbor, MI, USA
| | - Arul M Chinnaiyan
- Department of Pathology and Rogel Cancer Center, University of Michigan Medical School, Ann Arbor, MI, USA
- Michigan Center for Translational Pathology, University of Michigan, Ann Arbor, MI, USA
| | - Luca Busino
- Department of Cancer Biology, Perelman School of Medicine, University of Pennsylvania, 421 Curie Boulevard, BRBII/III, Philadelphia, PA, 19104, USA
| | - Egon Ogris
- Center for Medical Biochemistry, Max Perutz Labs, Medical University of Vienna, Dr. Bohr-Gasse 9/2, Vienna, 1030, Austria.
| | - Goutham Narla
- Division of Genetic Medicine, Department of Internal Medicine, University of Michigan, Ann Arbor, MI, 48105, USA.
- Rogel Cancer Center, University of Michigan, Ann Arbor, MI, 48109, USA.
| | - Irfan A Asangani
- Department of Cancer Biology, Perelman School of Medicine, University of Pennsylvania, 421 Curie Boulevard, BRBII/III, Philadelphia, PA, 19104, USA.
- Abramson Family Cancer Research Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
- Epigenetics Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
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5
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Reinhardt R, Leonard TA. A critical evaluation of protein kinase regulation by activation loop autophosphorylation. eLife 2023; 12:e88210. [PMID: 37470698 PMCID: PMC10359097 DOI: 10.7554/elife.88210] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 07/07/2023] [Indexed: 07/21/2023] Open
Abstract
Phosphorylation of proteins is a ubiquitous mechanism of regulating their function, localization, or activity. Protein kinases, enzymes that use ATP to phosphorylate protein substrates are, therefore, powerful signal transducers in eukaryotic cells. The mechanism of phosphoryl-transfer is universally conserved among protein kinases, which necessitates the tight regulation of kinase activity for the orchestration of cellular processes with high spatial and temporal fidelity. In response to a stimulus, many kinases enhance their own activity by autophosphorylating a conserved amino acid in their activation loop, but precisely how this reaction is performed is controversial. Classically, kinases that autophosphorylate their activation loop are thought to perform the reaction in trans, mediated by transient dimerization of their kinase domains. However, motivated by the recently discovered regulation mechanism of activation loop cis-autophosphorylation by a kinase that is autoinhibited in trans, we here review the various mechanisms of autoregulation that have been proposed. We provide a framework for critically evaluating biochemical, kinetic, and structural evidence for protein kinase dimerization and autophosphorylation, and share some thoughts on the implications of these mechanisms within physiological signaling networks.
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Affiliation(s)
- Ronja Reinhardt
- Max Perutz Labs, Vienna Biocenter Campus (VBC)ViennaAustria
- Medical University of Vienna, Center for Medical BiochemistryViennaAustria
| | - Thomas A Leonard
- Max Perutz Labs, Vienna Biocenter Campus (VBC)ViennaAustria
- Medical University of Vienna, Center for Medical BiochemistryViennaAustria
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6
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Eteläinen TS, Silva MC, Uhari-Väänänen JK, De Lorenzo F, Jäntti MH, Cui H, Chavero-Pieres M, Kilpeläinen T, Mechtler C, Svarcbahs R, Seppälä E, Savinainen JR, Puris E, Fricker G, Gynther M, Julku UH, Huttunen HJ, Haggarty SJ, Myöhänen TT. A prolyl oligopeptidase inhibitor reduces tau pathology in cellular models and in mice with tauopathy. Sci Transl Med 2023; 15:eabq2915. [PMID: 37043557 DOI: 10.1126/scitranslmed.abq2915] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/14/2023]
Abstract
Tauopathies are neurodegenerative diseases that are characterized by accumulation of hyperphosphorylated tau protein, higher-order aggregates, and tau filaments. Protein phosphatase 2A (PP2A) is a major tau dephosphorylating phosphatase, and a decrease in its activity has been demonstrated in tauopathies, including Alzheimer's disease. Prolyl oligopeptidase is a serine protease that is associated with neurodegeneration, and its inhibition normalizes PP2A activity without toxicity under pathological conditions. Here, we assessed whether prolyl oligopeptidase inhibition could protect against tau-mediated toxicity in cellular models in vitro and in the PS19 transgenic mouse model of tauopathy carrying the human tau-P301S mutation. We show that inhibition of prolyl oligopeptidase with the inhibitor KYP-2047 reduced tau aggregation in tau-transfected HEK-293 cells and N2A cells as well as in human iPSC-derived neurons carrying either the P301L or tau-A152T mutation. Treatment with KYP-2047 resulted in increased PP2A activity and activation of autophagic flux in HEK-293 cells and N2A cells and in patient-derived iNeurons, as indicated by changes in autophagosome and autophagy receptor markers; this contributed to clearance of insoluble tau. Furthermore, treatment of PS19 transgenic mice for 1 month with KYP-2047 reduced tau burden in the brain and cerebrospinal fluid and slowed cognitive decline according to several behavioral tests. In addition, a reduction in an oxidative stress marker was seen in mouse brains after KYP-2047 treatment. This study suggests that inhibition of prolyl oligopeptidase could help to ameliorate tau-dependent neurodegeneration.
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Affiliation(s)
- Tony S Eteläinen
- Division of Pharmacology and Pharmacotherapy/Drug Research Program, Faculty of Pharmacy, University of Helsinki, Helsinki 00014, Finland
| | - M Catarina Silva
- Chemical Neurobiology Laboratory, Departments of Neurology and Psychiatry, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Johanna K Uhari-Väänänen
- Division of Pharmacology and Pharmacotherapy/Drug Research Program, Faculty of Pharmacy, University of Helsinki, Helsinki 00014, Finland
| | - Francesca De Lorenzo
- Division of Pharmacology and Pharmacotherapy/Drug Research Program, Faculty of Pharmacy, University of Helsinki, Helsinki 00014, Finland
| | - Maria H Jäntti
- Division of Pharmacology and Pharmacotherapy/Drug Research Program, Faculty of Pharmacy, University of Helsinki, Helsinki 00014, Finland
| | - Hengjing Cui
- School of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, Kuopio 70211, Finland
| | - Marta Chavero-Pieres
- Division of Pharmacology and Pharmacotherapy/Drug Research Program, Faculty of Pharmacy, University of Helsinki, Helsinki 00014, Finland
| | - Tommi Kilpeläinen
- Division of Pharmacology and Pharmacotherapy/Drug Research Program, Faculty of Pharmacy, University of Helsinki, Helsinki 00014, Finland
| | - Christina Mechtler
- Division of Pharmacology and Pharmacotherapy/Drug Research Program, Faculty of Pharmacy, University of Helsinki, Helsinki 00014, Finland
| | - Reinis Svarcbahs
- Division of Pharmacology and Pharmacotherapy/Drug Research Program, Faculty of Pharmacy, University of Helsinki, Helsinki 00014, Finland
| | - Erin Seppälä
- School of Medicine / Biomedicine, Faculty of Health Sciences, University of Eastern Finland, Kuopio 70211, Finland
| | - Juha R Savinainen
- School of Medicine / Biomedicine, Faculty of Health Sciences, University of Eastern Finland, Kuopio 70211, Finland
| | - Elena Puris
- Institute of Pharmacy and Molecular Biotechnology, Ruprecht Karls University, Heidelberg D-69120, Germany
| | - Gert Fricker
- Institute of Pharmacy and Molecular Biotechnology, Ruprecht Karls University, Heidelberg D-69120, Germany
| | - Mikko Gynther
- Institute of Pharmacy and Molecular Biotechnology, Ruprecht Karls University, Heidelberg D-69120, Germany
| | - Ulrika H Julku
- Division of Pharmacology and Pharmacotherapy/Drug Research Program, Faculty of Pharmacy, University of Helsinki, Helsinki 00014, Finland
| | - Henri J Huttunen
- Neuroscience Center, University of Helsinki, Helsinki 00014, Finland
- Herantis Pharma Plc., Espoo 02600, Finland
| | - Stephen J Haggarty
- Chemical Neurobiology Laboratory, Departments of Neurology and Psychiatry, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Timo T Myöhänen
- Division of Pharmacology and Pharmacotherapy/Drug Research Program, Faculty of Pharmacy, University of Helsinki, Helsinki 00014, Finland
- School of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, Kuopio 70211, Finland
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7
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Xing J, Chen K, Gao S, Pousse M, Ying Y, Wang B, Chen L, Wang C, Wang L, Hu W, Lu Y, Gilson E, Ye J. Protein phosphatase 2A activators reverse age-related behavioral changes by targeting neural cell senescence. Aging Cell 2023; 22:e13780. [PMID: 36644807 PMCID: PMC10014060 DOI: 10.1111/acel.13780] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Revised: 12/04/2022] [Accepted: 12/19/2022] [Indexed: 01/17/2023] Open
Abstract
The contribution of cellular senescence to the behavioral changes observed in the elderly remains elusive. Here, we observed that aging is associated with a decline in protein phosphatase 2A (PP2A) activity in the brains of zebrafish and mice. Moreover, drugs activating PP2A reversed age-related behavioral changes. We developed a transgenic zebrafish model to decrease PP2A activity in the brain through knockout of the ppp2r2c gene encoding a regulatory subunit of PP2A. Mutant fish exhibited the behavioral phenotype observed in old animals and premature accumulation of neural cells positive for markers of cellular senescence, including senescence-associated β-galactosidase, elevated levels cdkn2a/b, cdkn1a, senescence-associated secretory phenotype gene expression, and an increased level of DNA damage signaling. The behavioral and cell senescence phenotypes were reversed in mutant fish through treatment with the senolytic ABT263 or diverse PP2A activators as well as through cdkn1a or tp53 gene ablation. Senomorphic function of PP2A activators was demonstrated in mouse primary neural cells with downregulated Ppp2r2c. We conclude that PP2A reduction leads to neural cell senescence thereby contributing to age-related behavioral changes and that PP2A activators have senotherapeutic properties against deleterious behavioral effects of brain aging.
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Affiliation(s)
- Jun Xing
- Geriatric Department, Geriatric Medical Center, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,International Laboratory in Cancer, Aging and Hematology, Shanghai Jiao Tong University School of Medicine/Ruijin Hospital/CNRS/Inserm/Côte d'Azur University, Shanghai, China
| | - Kehua Chen
- Geriatric Department, Geriatric Medical Center, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,International Laboratory in Cancer, Aging and Hematology, Shanghai Jiao Tong University School of Medicine/Ruijin Hospital/CNRS/Inserm/Côte d'Azur University, Shanghai, China
| | - Shuaiyun Gao
- Geriatric Department, Geriatric Medical Center, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,International Laboratory in Cancer, Aging and Hematology, Shanghai Jiao Tong University School of Medicine/Ruijin Hospital/CNRS/Inserm/Côte d'Azur University, Shanghai, China
| | - Mélanie Pousse
- International Laboratory in Cancer, Aging and Hematology, Shanghai Jiao Tong University School of Medicine/Ruijin Hospital/CNRS/Inserm/Côte d'Azur University, Shanghai, China.,IRCAN, Côte d'Azur University, CNRS, Inserm, Nice, France
| | - Yilin Ying
- Geriatric Department, Geriatric Medical Center, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,International Laboratory in Cancer, Aging and Hematology, Shanghai Jiao Tong University School of Medicine/Ruijin Hospital/CNRS/Inserm/Côte d'Azur University, Shanghai, China.,IRCAN, Côte d'Azur University, CNRS, Inserm, Nice, France
| | - Bo Wang
- Geriatric Department, Geriatric Medical Center, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,International Laboratory in Cancer, Aging and Hematology, Shanghai Jiao Tong University School of Medicine/Ruijin Hospital/CNRS/Inserm/Côte d'Azur University, Shanghai, China
| | - Lianxiang Chen
- Geriatric Department, Geriatric Medical Center, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,International Laboratory in Cancer, Aging and Hematology, Shanghai Jiao Tong University School of Medicine/Ruijin Hospital/CNRS/Inserm/Côte d'Azur University, Shanghai, China
| | - Cuicui Wang
- Geriatric Department, Geriatric Medical Center, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,International Laboratory in Cancer, Aging and Hematology, Shanghai Jiao Tong University School of Medicine/Ruijin Hospital/CNRS/Inserm/Côte d'Azur University, Shanghai, China
| | - Lei Wang
- Geriatric Department, Geriatric Medical Center, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Weiguo Hu
- Geriatric Department, Geriatric Medical Center, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yiming Lu
- Geriatric Department, Geriatric Medical Center, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,International Laboratory in Cancer, Aging and Hematology, Shanghai Jiao Tong University School of Medicine/Ruijin Hospital/CNRS/Inserm/Côte d'Azur University, Shanghai, China
| | - Eric Gilson
- International Laboratory in Cancer, Aging and Hematology, Shanghai Jiao Tong University School of Medicine/Ruijin Hospital/CNRS/Inserm/Côte d'Azur University, Shanghai, China.,IRCAN, Côte d'Azur University, CNRS, Inserm, Nice, France.,Department of Genetics, CHU, Nice, France
| | - Jing Ye
- Geriatric Department, Geriatric Medical Center, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,International Laboratory in Cancer, Aging and Hematology, Shanghai Jiao Tong University School of Medicine/Ruijin Hospital/CNRS/Inserm/Côte d'Azur University, Shanghai, China
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8
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Waury K, Willemse EAJ, Vanmechelen E, Zetterberg H, Teunissen CE, Abeln S. Bioinformatics tools and data resources for assay development of fluid protein biomarkers. Biomark Res 2022; 10:83. [DOI: 10.1186/s40364-022-00425-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2022] [Accepted: 10/25/2022] [Indexed: 11/16/2022] Open
Abstract
AbstractFluid protein biomarkers are important tools in clinical research and health care to support diagnosis and to monitor patients. Especially within the field of dementia, novel biomarkers could address the current challenges of providing an early diagnosis and of selecting trial participants. While the great potential of fluid biomarkers is recognized, their implementation in routine clinical use has been slow. One major obstacle is the often unsuccessful translation of biomarker candidates from explorative high-throughput techniques to sensitive antibody-based immunoassays. In this review, we propose the incorporation of bioinformatics into the workflow of novel immunoassay development to overcome this bottleneck and thus facilitate the development of novel biomarkers towards clinical laboratory practice. Due to the rapid progress within the field of bioinformatics many freely available and easy-to-use tools and data resources exist which can aid the researcher at various stages. Current prediction methods and databases can support the selection of suitable biomarker candidates, as well as the choice of appropriate commercial affinity reagents. Additionally, we examine methods that can determine or predict the epitope - an antibody’s binding region on its antigen - and can help to make an informed choice on the immunogenic peptide used for novel antibody production. Selected use cases for biomarker candidates help illustrate the application and interpretation of the introduced tools.
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9
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Kokot T, Köhn M. Emerging insights into serine/threonine-specific phosphoprotein phosphatase function and selectivity. J Cell Sci 2022; 135:277104. [DOI: 10.1242/jcs.259618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
ABSTRACT
Protein phosphorylation on serine and threonine residues is a widely distributed post-translational modification on proteins that acts to regulate their function. Phosphoprotein phosphatases (PPPs) contribute significantly to a plethora of cellular functions through the accurate dephosphorylation of phosphorylated residues. Most PPPs accomplish their purpose through the formation of complex holoenzymes composed of a catalytic subunit with various regulatory subunits. PPP holoenzymes then bind and dephosphorylate substrates in a highly specific manner. Despite the high prevalence of PPPs and their important role for cellular function, their mechanisms of action in the cell are still not well understood. Nevertheless, substantial experimental advancements in (phospho-)proteomics, structural and computational biology have contributed significantly to a better understanding of PPP biology in recent years. This Review focuses on recent approaches and provides an overview of substantial new insights into the complex mechanism of PPP holoenzyme regulation and substrate selectivity.
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Affiliation(s)
- Thomas Kokot
- Signalling Research Centres BIOSS and CIBSS, University of Freiburg 1 , Freiburg 79104 , Germany
- University of Freiburg, 2 Faculty of Biology , Freiburg 79104 , Germany
| | - Maja Köhn
- Signalling Research Centres BIOSS and CIBSS, University of Freiburg 1 , Freiburg 79104 , Germany
- University of Freiburg, 2 Faculty of Biology , Freiburg 79104 , Germany
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10
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Ripamonti M, Lamarca A, Davey NE, Tonoli D, Surini S, de Curtis I. A functional interaction between liprin-α1 and B56γ regulatory subunit of protein phosphatase 2A supports tumor cell motility. Commun Biol 2022; 5:1025. [PMID: 36171301 PMCID: PMC9519923 DOI: 10.1038/s42003-022-03989-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2022] [Accepted: 09/13/2022] [Indexed: 11/25/2022] Open
Abstract
Scaffold liprin-α1 is required to assemble dynamic plasma membrane-associated platforms (PMAPs) at the front of migrating breast cancer cells, to promote protrusion and invasion. We show that the N-terminal region of liprin-α1 contains an LxxIxE motif interacting with B56 regulatory subunits of serine/threonine protein phosphatase 2A (PP2A). The specific interaction of B56γ with liprin-α1 requires an intact motif, since two point mutations strongly reduce the interaction. B56γ mediates the interaction of liprin-α1 with the heterotrimeric PP2A holoenzyme. Most B56γ protein is recovered in the cytosolic fraction of invasive MDA-MB-231 breast cancer cells, where B56γ is complexed with liprin-α1. While mutation of the short linear motif (SLiM) does not affect localization of liprin-α1 to PMAPs, localization of B56γ at these sites specifically requires liprin-α1. Silencing of B56γ or liprin-α1 inhibits to similar extent cell spreading on extracellular matrix, invasion, motility and lamellipodia dynamics in migrating MDA-MB-231 cells, suggesting that B56γ/PP2A is a novel component of the PMAPs machinery regulating tumor cell motility. In this direction, inhibition of cell spreading by silencing liprin-α1 is not rescued by expression of B56γ binding-defective liprin-α1 mutant. We propose that liprin-α1-mediated recruitment of PP2A via B56γ regulates cell motility by controlling protrusion in migrating MDA-MB-231 cells.
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Affiliation(s)
- Marta Ripamonti
- San Raffaele Scientific Institute and Università Vita-Salute San Raffaele, Milano, Italy
| | - Andrea Lamarca
- San Raffaele Scientific Institute and Università Vita-Salute San Raffaele, Milano, Italy
| | - Norman E Davey
- Division of Cancer Biology, The Institute of Cancer Research, 237 Fulham Road, London, SW3 6JB, UK
| | - Diletta Tonoli
- San Raffaele Scientific Institute and Università Vita-Salute San Raffaele, Milano, Italy
| | - Sara Surini
- San Raffaele Scientific Institute and Università Vita-Salute San Raffaele, Milano, Italy
| | - Ivan de Curtis
- San Raffaele Scientific Institute and Università Vita-Salute San Raffaele, Milano, Italy.
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11
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Skolnick J, Zhou H. Implications of the Essential Role of Small Molecule Ligand Binding Pockets in Protein-Protein Interactions. J Phys Chem B 2022; 126:6853-6867. [PMID: 36044742 PMCID: PMC9484464 DOI: 10.1021/acs.jpcb.2c04525] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 08/18/2022] [Indexed: 11/28/2022]
Abstract
Protein-protein interactions (PPIs) and protein-metabolite interactions play a key role in many biochemical processes, yet they are often viewed as being independent. However, the fact that small molecule drugs have been successful in inhibiting PPIs suggests a deeper relationship between protein pockets that bind small molecules and PPIs. We demonstrate that 2/3 of PPI interfaces, including antibody-epitope interfaces, contain at least one significant small molecule ligand binding pocket. In a representative library of 50 distinct protein-protein interactions involving hundreds of mutations, >75% of hot spot residues overlap with small molecule ligand binding pockets. Hence, ligand binding pockets play an essential role in PPIs. In representative cases, evolutionary unrelated monomers that are involved in different multimeric interactions yet share the same pocket are predicted to bind the same metabolites/drugs; these results are confirmed by examples in the PDB. Thus, the binding of a metabolite can shift the equilibrium between monomers and multimers. This implicit coupling of PPI equilibria, termed "metabolic entanglement", was successfully employed to suggest novel functional relationships among protein multimers that do not directly interact. Thus, the current work provides an approach to unify metabolomics and protein interactomics.
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Affiliation(s)
- Jeffrey Skolnick
- Center for the Study of Systems
Biology, School of Biological Sciences, Georgia Institute of Technology, 950 Atlantic Drive, NW, Atlanta, Georgia 30332, United States
| | - Hongyi Zhou
- Center for the Study of Systems
Biology, School of Biological Sciences, Georgia Institute of Technology, 950 Atlantic Drive, NW, Atlanta, Georgia 30332, United States
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12
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Sontag JM, Schuhmacher D, Taleski G, Jordan A, Khan S, Hoffman A, Gomez RJ, Mazalouskas MD, Hanks SK, Spiller BW, Sontag E, Wadzinski BE. A new paradigm for regulation of protein phosphatase 2A function via Src and Fyn kinase-mediated tyrosine phosphorylation. J Biol Chem 2022; 298:102248. [PMID: 35820485 PMCID: PMC9396060 DOI: 10.1016/j.jbc.2022.102248] [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: 01/19/2022] [Revised: 07/01/2022] [Accepted: 07/04/2022] [Indexed: 12/01/2022] Open
Abstract
Protein phosphatase 2A (PP2A) is a major phospho-Ser/Thr phosphatase and a key regulator of cellular signal transduction pathways. While PP2A dysfunction has been linked to human cancer and neurodegenerative disorders such as Alzheimer’s disease (AD), PP2A regulation remains relatively poorly understood. It has been reported that the PP2A catalytic subunit (PP2Ac) is inactivated by a single phosphorylation at the Tyr307 residue by tyrosine kinases such as v-Src. However, multiple mass spectrometry studies have revealed the existence of other putative PP2Ac phosphorylation sites in response to activation of Src and Fyn, two major Src family kinases (SFKs). Here, using PP2Ac phosphomutants and novel phosphosite-specific PP2Ac antibodies, we show that cellular pools of PP2Ac are instead phosphorylated on both Tyr127 and Tyr284 upon Src activation, and on Tyr284 following Fyn activation. We found these phosphorylation events enhanced the interaction of PP2Ac with SFKs. In addition, we reveal SFK-mediated phosphorylation of PP2Ac at Y284 promotes dissociation of the regulatory Bα subunit, altering PP2A substrate specificity; the phosphodeficient Y127/284F and Y284F PP2Ac mutants prevented SFK-mediated phosphorylation of Tau at the CP13 (pSer202) epitope, a pathological hallmark of AD, and SFK-dependent activation of ERK, a major growth regulatory kinase upregulated in many cancers. Our findings demonstrate a novel PP2A regulatory mechanism that challenges the existing dogma on the inhibition of PP2A catalytic activity by Tyr307 phosphorylation. We propose dysregulation of SFK signaling in cancer and AD can lead to alterations in PP2A phosphorylation and subsequent deregulation of key PP2A substrates, including ERK and Tau.
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Affiliation(s)
- Jean-Marie Sontag
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia
| | - Diana Schuhmacher
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia
| | - Goce Taleski
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia
| | - Anthony Jordan
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Sarah Khan
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Alexander Hoffman
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia
| | - Rey J Gomez
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Matthew D Mazalouskas
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Steven K Hanks
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Benjamin W Spiller
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Estelle Sontag
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia.
| | - Brian E Wadzinski
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA.
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13
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Goswami S, Mani R, Nunes J, Chiang CL, Zapolnik K, Hu E, Frissora F, Mo X, Walker LA, Yan P, Bundschuh R, Beaver L, Devine R, Tsai YT, Ventura A, Xie Z, Chen M, Lapalombella R, Walker A, Mims A, Larkin K, Grieselhuber N, Bennett C, Phelps M, Hertlein E, Behbehani G, Vasu S, Byrd JC, Muthusamy N. PP2A is a therapeutically targetable driver of cell fate decisions via a c-Myc/p21 axis in human and murine acute myeloid leukemia. Blood 2022; 139:1340-1358. [PMID: 34788382 PMCID: PMC8900275 DOI: 10.1182/blood.2020010344] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2021] [Accepted: 10/30/2021] [Indexed: 11/20/2022] Open
Abstract
Dysregulated cellular differentiation is a hallmark of acute leukemogenesis. Phosphatases are widely suppressed in cancers but have not been traditionally associated with differentiation. In this study, we found that the silencing of protein phosphatase 2A (PP2A) directly blocks differentiation in acute myeloid leukemia (AML). Gene expression and mass cytometric profiling revealed that PP2A activation modulates cell cycle and transcriptional regulators that program terminal myeloid differentiation. Using a novel pharmacological agent, OSU-2S, in parallel with genetic approaches, we discovered that PP2A enforced c-Myc and p21 dependent terminal differentiation, proliferation arrest, and apoptosis in AML. Finally, we demonstrated that PP2A activation decreased leukemia-initiating stem cells, increased leukemic blast maturation, and improved overall survival in murine Tet2-/-Flt3ITD/WT and human cell-line derived xenograft AML models in vivo. Our findings identify the PP2A/c-Myc/p21 axis as a critical regulator of the differentiation/proliferation switch in AML that can be therapeutically targeted in malignancies with dysregulated maturation fate.
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Affiliation(s)
- Swagata Goswami
- The Ohio State University Comprehensive Cancer Center, The Ohio State University, Columbus, OH
- Molecular, Cellular, and Developmental Biology Graduate Program, The Ohio State University, Columbus, OH
| | | | - Jessica Nunes
- The Ohio State University Comprehensive Cancer Center, The Ohio State University, Columbus, OH
- Molecular, Cellular, and Developmental Biology Graduate Program, The Ohio State University, Columbus, OH
| | - Chi-Ling Chiang
- The Ohio State University Comprehensive Cancer Center, The Ohio State University, Columbus, OH
| | - Kevan Zapolnik
- The Ohio State University Comprehensive Cancer Center, The Ohio State University, Columbus, OH
| | - Eileen Hu
- The Ohio State University Comprehensive Cancer Center, The Ohio State University, Columbus, OH
| | - Frank Frissora
- The Ohio State University Comprehensive Cancer Center, The Ohio State University, Columbus, OH
| | - Xiaokui Mo
- Center for Biostatistics, The Ohio State University, Columbus, OH
| | - Logan A Walker
- Biophysics Graduate Program, University of Michigan, Ann Arbor, MI
| | - Pearlly Yan
- The Ohio State University Comprehensive Cancer Center, The Ohio State University, Columbus, OH
- Division of Hematology, Department of Internal Medicine, The Ohio State University, Columbus, OH
| | - Ralf Bundschuh
- Division of Hematology, Department of Internal Medicine, The Ohio State University, Columbus, OH
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH
- Department of Physics, The Ohio State University, Columbus, OH; and
| | - Larry Beaver
- The Ohio State University Comprehensive Cancer Center, The Ohio State University, Columbus, OH
| | - Raymond Devine
- The Ohio State University Comprehensive Cancer Center, The Ohio State University, Columbus, OH
| | - Yo-Ting Tsai
- The Ohio State University Comprehensive Cancer Center, The Ohio State University, Columbus, OH
| | - Ann Ventura
- The Ohio State University Comprehensive Cancer Center, The Ohio State University, Columbus, OH
| | - Zhiliang Xie
- The Ohio State University Comprehensive Cancer Center, The Ohio State University, Columbus, OH
| | - Min Chen
- College of Pharmacy, The Ohio State University, Columbus, OH
| | - Rosa Lapalombella
- The Ohio State University Comprehensive Cancer Center, The Ohio State University, Columbus, OH
- Division of Hematology, Department of Internal Medicine, The Ohio State University, Columbus, OH
| | - Alison Walker
- The Ohio State University Comprehensive Cancer Center, The Ohio State University, Columbus, OH
- Division of Hematology, Department of Internal Medicine, The Ohio State University, Columbus, OH
| | - Alice Mims
- The Ohio State University Comprehensive Cancer Center, The Ohio State University, Columbus, OH
- Division of Hematology, Department of Internal Medicine, The Ohio State University, Columbus, OH
| | - Karilyn Larkin
- The Ohio State University Comprehensive Cancer Center, The Ohio State University, Columbus, OH
- Division of Hematology, Department of Internal Medicine, The Ohio State University, Columbus, OH
| | - Nicole Grieselhuber
- The Ohio State University Comprehensive Cancer Center, The Ohio State University, Columbus, OH
- Division of Hematology, Department of Internal Medicine, The Ohio State University, Columbus, OH
| | - Chad Bennett
- The Ohio State University Comprehensive Cancer Center, The Ohio State University, Columbus, OH
| | - Mitch Phelps
- The Ohio State University Comprehensive Cancer Center, The Ohio State University, Columbus, OH
- College of Pharmacy, The Ohio State University, Columbus, OH
| | - Erin Hertlein
- The Ohio State University Comprehensive Cancer Center, The Ohio State University, Columbus, OH
- Division of Hematology, Department of Internal Medicine, The Ohio State University, Columbus, OH
| | - Gregory Behbehani
- The Ohio State University Comprehensive Cancer Center, The Ohio State University, Columbus, OH
- Division of Hematology, Department of Internal Medicine, The Ohio State University, Columbus, OH
| | - Sumithira Vasu
- The Ohio State University Comprehensive Cancer Center, The Ohio State University, Columbus, OH
- Division of Hematology, Department of Internal Medicine, The Ohio State University, Columbus, OH
| | - John C Byrd
- The Ohio State University Comprehensive Cancer Center, The Ohio State University, Columbus, OH
- Division of Hematology, Department of Internal Medicine, The Ohio State University, Columbus, OH
- College of Pharmacy, The Ohio State University, Columbus, OH
| | - Natarajan Muthusamy
- The Ohio State University Comprehensive Cancer Center, The Ohio State University, Columbus, OH
- Division of Hematology, Department of Internal Medicine, The Ohio State University, Columbus, OH
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14
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PP2A activation targets AML stem cells. Blood 2022; 139:1267-1269. [PMID: 35238886 DOI: 10.1182/blood.2021014677] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 11/19/2021] [Indexed: 11/20/2022] Open
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15
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Sharifi MJ, Vakili E, Ilkhanipoor H, Zekavat OR, Bordbar M. Elevated CD9 expression as a potential biomarker for diagnosis of Bernard-Soulier syndrome. Blood Coagul Fibrinolysis 2022; 33:159-161. [PMID: 35165218 DOI: 10.1097/mbc.0000000000001117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Diagnosis of inherited platelet glycoprotein disorders is based on specific laboratory techniques such as aggregometry and flow cytometry. Flowcytometry is a powerful method, but equivocal results are produced in some cases. New cluster of differentiation markers could resolve the diagnostic dilemmas. Abnormal expression of CD9 in Bernard-Soulier syndrome (BSS) is recently reported. We aimed to determine the diagnostic significance of CD9 expression in a cohort of Iranian patients with inherited platelet glycoprotein defects. Twelve BSS, 21 Glanzmann thrombasthenia and 16 healthy controls were included in the present study. Flowcytometric diagnosis of BSS and Glanzmann thrombasthenia was made by analysis of CD41/61 and CD42a/42b CD markers. Moreover, phycoerythrin-labelled anti CD9 was examined in patients and healthy controls. The mean fluorescence intensity (MFI) of CD9 among the three groups was compared using suitable statistical methods and a P value of less than 0.05 considered statistically significant. Mean MFI of CD9 was 990.0 in BSS patients versus 421.2 and 317.3 in individuals with Glanzmann thrombasthenia and healthy controls, respectively (P < 0.05). Between the two-group comparison of means by the Mann--Whitney test revealed a P value of less than 0.001 for BSS group versus GT (2.4-fold) and BSS versus healthy controls (2.9-fold). CD9 molecule also expressed differently in patients with Glanzmann thrombasthenia in comparison with healthy controls (P < 0.001), although with a less magnitude (1.3-fold). According to our findings, CD9 is a potential biomarker for laboratory diagnosis of inherited glycoprotein defects, especially to elucidate the ambiguous results in BSS cases.
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Affiliation(s)
- Mohammad Jafar Sharifi
- Division of Laboratory Hematology and Blood Banking, Department of Medical Laboratory Sciences, School of Paramedical Sciences, Shiraz University of Medical Sciences Pediatric Department Pediatric Endocrinology and Metabolism Department, Shiraz University of Medical Sciences Hematology Research Center, Shiraz, Iran
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16
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Gunasekara H, Munaweera R, Novotná L, Lillemeier BF, Hu YS. Chaotropic Perturbation of Noncovalent Interactions of the Hemagglutinin Tag Monoclonal Antibody Fragment Enables Superresolution Molecular Census. ACS NANO 2022; 16:129-139. [PMID: 34797055 PMCID: PMC11196025 DOI: 10.1021/acsnano.1c04237] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Antibody-antigen interactions represent one of the most exploited biomolecular interactions in experimental biology. While numerous techniques harnessed immobilized antibodies for nanoscale fluorescence imaging, few utilized their reversible binding kinetics. Here, we investigated noncovalent interactions of the monoclonal hemagglutinin (HA) epitope tag antibody, 12CA5, in the fixed cellular environment. We observed that the use of a chaotropic agent, potassium thiocyanate (KSCN), promoted the dissociation of the 12CA5 antibody fragment (Fab), which already displayed faster dissociation compared to its immunoglobulin G (IgG) counterpart. Molecular dynamic simulations revealed notable root-mean-square deviations and destabilizations in the presence of KSCN, while the hydrogen-bonding network remained primarily unaffected at the antigen-binding site. The reversible interactions enabled us to achieve a superresolution molecular census of local populations of 3xHA tagged microtubule fibers with improved molecular quantification consistency compared to single-molecule localization microscopy (SMLM) techniques utilizing standard immunofluorescence staining for sample labeling. Our technique, termed superresolution census of molecular epitope tags (SR-COMET), highlights the utilization of reversible antibody-antigen interactions for SMLM-based quantitative superresolution imaging.
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Affiliation(s)
- Hirushi Gunasekara
- Department of Chemistry, College of Liberal Arts and Sciences, University of Illinois at Chicago, Chicago, IL, 60607-7061, United States
| | - Rangika Munaweera
- Department of Chemistry, College of Liberal Arts and Sciences, University of Illinois at Chicago, Chicago, IL, 60607-7061, United States
| | - Lucie Novotná
- Nomis Center for Immunobiology and Microbial Pathogenesis & Waitt Advanced Biophotonics Center, Salk Institute for Biological Studies, La Jolla, California 92037, United States
| | - Björn F. Lillemeier
- Nomis Center for Immunobiology and Microbial Pathogenesis & Waitt Advanced Biophotonics Center, Salk Institute for Biological Studies, La Jolla, California 92037, United States
- Faculty of Biology and Centre for Integrative Biological Signalling Studies (CIBSS), Albert-Ludwigs-University of Freiburg, Freiburg 79104, Germany
| | - Ying S. Hu
- Department of Chemistry, College of Liberal Arts and Sciences, University of Illinois at Chicago, Chicago, IL, 60607-7061, United States
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17
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Kemp BA, Howell NL, Gildea JJ, Keller SR, Brautigan DL, Carey RM. Renal AT 2 Receptors Mediate Natriuresis via Protein Phosphatase PP2A. Circ Res 2022; 130:96-111. [PMID: 34794320 PMCID: PMC8741733 DOI: 10.1161/circresaha.121.319519] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
BACKGROUND How signals from activated angiotensin type-2 receptors (AT2R) mediate inhibition of sodium ion (Na+) reabsorption in renal proximal tubule cells is currently unknown. Protein phosphatases including PP2A (protein phosphatase 2A) have been implicated in AT2R signaling in tissues other than kidney. We investigated whether inhibition of protein phosphatase PP2A reduced AT2R-mediated natriuresis and evaluated changes in PP2A activity and localization after renal AT2R activation in normal 4- and 10-week-old control Wistar-Kyoto rats and 4-week-old prehypertensive and 10-week-old hypertensive spontaneously hypertensive rats. METHODS AND RESULTS In Wistar-Kyoto rats, direct renal interstitial administration of selective AT2R nonpeptide agonist Compound-21 (C-21) increased renal interstitial cyclic GMP (cGMP) levels, urine Na+ excretion, and simultaneously increased PP2A activity ≈2-fold in homogenates of renal cortical tubules. The cyclic GMP and natriuretic responses were abolished by concurrent renal interstitial administration of protein phosphatase inhibitor calyculin A. In renal proximal tubule cells in response to C-21, PP2A subunits A, B55α and C, but not B56γ, were recruited to apical plasma membranes together with AT2Rs. Calyculin A treatment abolished C-21-induced translocation of both AT2R and PP2A regulatory subunit B55α to apical plasma membranes. Immunoprecipitation of AT2R solubilized from renal cortical homogenates demonstrated physical association of AT2R with PP2A A, B55α, and C but not B56γ subunits. In contrast, in spontaneously hypertensive rats, administration of C-21 did not alter urine Na+ excretion or PP2A activity and failed to translocate AT2Rs and PP2A subunits to apical plasma membranes. CONCLUSIONS In renal proximal tubule cells of Wistar-Kyoto rats, PP2A is activated and PP2A subunits AB55αC are recruited to C-21-activated AT2Rs during induction of natriuresis. This response is defective in prehypertensive and hypertensive spontaneously hypertensive rats, presenting a potential novel therapeutic target for treating renal Na+ retention and hypertension.
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Affiliation(s)
- Brandon A. Kemp
- Division of Endocrinology and Metabolism, Department of Medicine, University of Virginia School of Medicine, Charlottesville, VA
| | - Nancy L. Howell
- Division of Endocrinology and Metabolism, Department of Medicine, University of Virginia School of Medicine, Charlottesville, VA
| | - John J. Gildea
- Department of Pathology, University of Virginia School of Medicine, Charlottesville, VA
| | - Susanna R. Keller
- Division of Endocrinology and Metabolism, Department of Medicine, University of Virginia School of Medicine, Charlottesville, VA
| | - David L. Brautigan
- Department of Microbiology, Immunology & Cancer Biology, University of Virginia School of Medicine, Charlottesville, VA
| | - Robert M. Carey
- Division of Endocrinology and Metabolism, Department of Medicine, University of Virginia School of Medicine, Charlottesville, VA
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18
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Lyons SP, Greiner EC, Cressey LE, Adamo ME, Kettenbach AN. Regulation of PP2A, PP4, and PP6 holoenzyme assembly by carboxyl-terminal methylation. Sci Rep 2021; 11:23031. [PMID: 34845248 PMCID: PMC8630191 DOI: 10.1038/s41598-021-02456-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 11/15/2021] [Indexed: 12/16/2022] Open
Abstract
The family of Phosphoprotein Phosphatases (PPPs) is responsible for most cellular serine and threonine dephosphorylation. PPPs achieve substrate specificity and selectivity by forming multimeric holoenzymes. PPP holoenzyme assembly is tightly controlled, and changes in the cellular repertoire of PPPs are linked to human disease, including cancer and neurodegeneration. For PP2A, PP4, and PP6, holoenzyme formation is in part regulated by carboxyl (C)-terminal methyl-esterification (often referred to as "methylation"). Here, we use mass spectrometry-based proteomics, methylation-ablating mutations, and genome editing to elucidate the role of C-terminal methylation on PP2A, PP4, and PP6 holoenzyme assembly. We find that the catalytic subunits of PP2A, PP4, and PP6 are frequently methylated in cancer cells and that deletion of the C-terminal leucine faithfully recapitulates loss of methylation. We observe that loss of PP2A methylation consistently reduced B55, B56, and B72 regulatory subunit binding in cancer and non-transformed cell lines. However, Striatin subunit binding is only affected in non-transformed cells. For PP4, we find that PP4R1 and PP4R3β bind in a methylation-dependent manner. Intriguingly, loss of methylation does not affect PP6 holoenzymes. Our analyses demonstrate in an unbiased, comprehensive, and isoform-specific manner the crucial regulatory function of endogenous PPP methylation in transformed and non-transformed cell lines.
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Affiliation(s)
- Scott P Lyons
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH, USA
| | | | | | | | - Arminja N Kettenbach
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH, USA.
- Norris Cotton Cancer Center, Lebanon, NH, USA.
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19
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Brauer BL, Wiredu K, Mitchell S, Moorhead GB, Gerber SA, Kettenbach AN. Affinity-based profiling of endogenous phosphoprotein phosphatases by mass spectrometry. Nat Protoc 2021; 16:4919-4943. [PMID: 34518704 PMCID: PMC8822503 DOI: 10.1038/s41596-021-00604-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Accepted: 07/12/2021] [Indexed: 02/08/2023]
Abstract
Phosphoprotein phosphatases (PPPs) execute >90% of serine/threonine dephosphorylation in cells and tissues. While the role of PPPs in cell biology and diseases such as cancer, cardiac hypertrophy and Alzheimer's disease is well established, the molecular mechanisms governing and governed by PPPs still await discovery. Here we describe a chemical proteomic strategy, phosphatase inhibitor beads and mass spectrometry (PIB-MS), that enables the identification and quantification of PPPs and their posttranslational modifications in as little as 12 h. Using a specific but nonselective PPP inhibitor immobilized on beads, PIB-MS enables the efficient affinity-capture, identification and quantification of endogenous PPPs and associated proteins ('PPPome') from cells and tissues. PIB-MS captures functional, endogenous PPP subunit interactions and enables discovery of new binding partners. It performs PPP enrichment without exogenous expression of tagged proteins or specific antibodies. Because PPPs are among the most conserved proteins across evolution, PIB-MS can be employed in any cell line, tissue or organism.
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Affiliation(s)
- Brooke L Brauer
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH, USA
| | - Kwame Wiredu
- Department of Molecular and Systems Biology, Geisel School of Medicine at Dartmouth, Hanover, NH, USA
| | - Sierra Mitchell
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - Greg B Moorhead
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - Scott A Gerber
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH, USA
- Department of Molecular and Systems Biology, Geisel School of Medicine at Dartmouth, Hanover, NH, USA
- Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth, Lebanon, NH, USA
| | - Arminja N Kettenbach
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH, USA.
- Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth, Lebanon, NH, USA.
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20
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Frohner IE, Mudrak I, Schüchner S, Anrather D, Hartl M, Sontag JM, Sontag E, Wadzinski BE, Preglej T, Ellmeier W, Ogris E. PP2A C Phospho-Tyr 307 Antibodies Are Not Specific for this Modification but Are Sensitive to Other PP2A C Modifications Including Leu 309 Methylation. Cell Rep 2021; 30:3171-3182.e6. [PMID: 32130916 DOI: 10.1016/j.celrep.2020.02.035] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 12/03/2019] [Accepted: 02/07/2020] [Indexed: 02/06/2023] Open
Abstract
Protein phosphatase 2A (PP2A) is an important regulator of signal transduction pathways and a tumor suppressor. Phosphorylation of the PP2A catalytic subunit (PP2AC) at tyrosine 307 has been claimed to inactivate PP2A and was examined in more than 180 studies using commercial antibodies, but this modification was never identified using mass spectrometry. Here we show that the most cited pTyr307 monoclonal antibodies, E155 and F-8, are not specific for phosphorylated Tyr307 but instead are hampered by PP2AC methylation at leucine 309 or phosphorylation at threonine 304. Other pTyr307 antibodies are sensitive to PP2AC methylation as well, and some cross-react with pTyr residues in general, including phosphorylated hemagglutinin tags. We identify pTyr307 using targeted mass spectrometry after transient overexpression of PP2AC and Src kinase. Yet under such conditions, none of the tested antibodies show exclusive pTyr307 specificity. Thus, data generated using these antibodies need to be revisited, and the mechanism of PP2A inactivation needs to be redefined.
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Affiliation(s)
- Ingrid E Frohner
- Center for Medical Biochemistry, Max Perutz Labs, Medical University of Vienna, Dr. Bohr-Gasse 9, 1030 Vienna, Austria
| | - Ingrid Mudrak
- Center for Medical Biochemistry, Max Perutz Labs, Medical University of Vienna, Dr. Bohr-Gasse 9, 1030 Vienna, Austria
| | - Stefan Schüchner
- Center for Medical Biochemistry, Max Perutz Labs, Medical University of Vienna, Dr. Bohr-Gasse 9, 1030 Vienna, Austria
| | - Dorothea Anrather
- Mass Spectrometry Facility, Max Perutz Labs, Dr. Bohr-Gasse 9, 1030 Vienna, Austria
| | - Markus Hartl
- Mass Spectrometry Facility, Max Perutz Labs, Dr. Bohr-Gasse 9, 1030 Vienna, Austria
| | - Jean-Marie Sontag
- School of Biomedical Sciences and Pharmacy, The University of Newcastle, Callaghan, NSW 2308, Australia
| | - Estelle Sontag
- School of Biomedical Sciences and Pharmacy, The University of Newcastle, Callaghan, NSW 2308, Australia
| | - Brian E Wadzinski
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Teresa Preglej
- Division of Immunobiology, Institute of Immunology, Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, 1090 Vienna, Austria
| | - Wilfried Ellmeier
- Division of Immunobiology, Institute of Immunology, Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, 1090 Vienna, Austria
| | - Egon Ogris
- Center for Medical Biochemistry, Max Perutz Labs, Medical University of Vienna, Dr. Bohr-Gasse 9, 1030 Vienna, Austria.
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21
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Taleski G, Schuhmacher D, Su H, Sontag JM, Sontag E. Disturbances in PP2A methylation and one-carbon metabolism compromise Fyn distribution, neuritogenesis, and APP regulation. J Biol Chem 2021; 296:100237. [PMID: 33380425 PMCID: PMC7948947 DOI: 10.1074/jbc.ra120.016069] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 12/28/2020] [Accepted: 12/30/2020] [Indexed: 01/12/2023] Open
Abstract
The nonreceptor protein tyrosine kinase Fyn and protein Ser/Thr phosphatase 2A (PP2A) are major multifunctional signaling molecules. Deregulation of Fyn and altered PP2A methylation are implicated in cancer and Alzheimer's disease (AD). Here, we tested the hypothesis that the methylation state of PP2A catalytic subunit, which influences PP2A subunit composition and substrate specificity, can affect Fyn regulation and function. Using Neuro-2a (N2a) neuroblastoma cell models, we first show that methylated PP2A holoenzymes containing the Bα subunit coimmunoprecipitate and copurify with Fyn in membrane rafts. PP2A methylation status regulates Fyn distribution and Fyn-dependent neuritogenesis, likely in part by affecting actin dynamics. A methylation-incompetent PP2A mutant fails to interact with Fyn. It perturbs the normal partitioning of Fyn and amyloid precursor protein (APP) in membrane microdomains, which governs Fyn function and APP processing. This correlates with enhanced amyloidogenic cleavage of APP, a hallmark of AD pathogenesis. Conversely, enhanced PP2A methylation promotes the nonamyloidogenic cleavage of APP in a Fyn-dependent manner. Disturbances in one-carbon metabolic pathways that control cellular methylation are associated with AD and cancer. Notably, they induce a parallel loss of membrane-associated methylated PP2A and Fyn enzymes in N2a cells and acute mouse brain slices. One-carbon metabolism also modulates Fyn-dependent process outgrowth in N2a cells. Thus, our findings identify a novel methylation-dependent PP2A/Fyn signaling module. They highlight the underestimated importance of cross talks between essential metabolic pathways and signaling scaffolds that are involved in normal cell homeostasis and currently being targeted for cancer and AD treatment.
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Affiliation(s)
- Goce Taleski
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia
| | - Diana Schuhmacher
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia
| | - Henry Su
- Department of Pathology, UT Southwestern Medical Center, Dallas, Texas, USA
| | - Jean-Marie Sontag
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia
| | - Estelle Sontag
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia.
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22
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Nasa I, Kettenbach AN. Effects of carboxyl-terminal methylation on holoenzyme function of the PP2A subfamily. Biochem Soc Trans 2020; 48:2015-2027. [PMID: 33125487 PMCID: PMC8380034 DOI: 10.1042/bst20200177] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 09/14/2020] [Accepted: 09/16/2020] [Indexed: 01/07/2023]
Abstract
Phosphoprotein Phosphatases (PPPs) are enzymes highly conserved from yeast and human and catalyze the majority of the serine and threonine dephosphorylation in cells. To achieve substrate specificity and selectivity, PPPs form multimeric holoenzymes consisting of catalytic, structural/scaffolding, and regulatory subunits. For the Protein Phosphatase 2A (PP2A)-subfamily of PPPs, holoenzyme assembly is at least in part regulated by an unusual carboxyl-terminal methyl-esterification, commonly referred to as 'methylation'. Carboxyl-terminal methylation is catalyzed by Leucine carboxyl methyltransferase-1 (LCMT1) that utilizes S-adenosyl-methionine (SAM) as the methyl donor and removed by protein phosphatase methylesterase 1 (PME1). For PP2A, methylation dictates regulatory subunit selection and thereby downstream phosphorylation signaling. Intriguingly, there are four families of PP2A regulatory subunits, each exhibiting different levels of methylation sensitivity. Thus, changes in PP2A methylation stoichiometry alters the complement of PP2A holoenzymes in cells and creates distinct modes of kinase opposition. Importantly, selective inactivation of PP2A signaling through the deregulation of methylation is observed in several diseases, most prominently Alzheimer's disease (AD). In this review, we focus on how carboxyl-terminal methylation of the PP2A subfamily (PP2A, PP4, and PP6) regulates holoenzyme function and thereby phosphorylation signaling, with an emphasis on AD.
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Affiliation(s)
- Isha Nasa
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth College, Hanover, NH, U.S.A
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center at Dartmouth, Lebanon, NH, U.S.A
| | - Arminja N Kettenbach
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth College, Hanover, NH, U.S.A
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center at Dartmouth, Lebanon, NH, U.S.A
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23
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Assi M, Pirlot B, Stroobant V, Thissen JP, Jacquemin P. A Novel KRAS Antibody Highlights a Regulation Mechanism of Post-Translational Modifications of KRAS during Tumorigenesis. Int J Mol Sci 2020; 21:ijms21176361. [PMID: 32887255 PMCID: PMC7504708 DOI: 10.3390/ijms21176361] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Revised: 08/27/2020] [Accepted: 08/31/2020] [Indexed: 12/17/2022] Open
Abstract
KRAS is a powerful oncogene responsible for the development of many cancers. Despite the great progress in understanding its function during the last decade, the study of KRAS expression, subcellular localization, and post-translational modifications remains technically challenging. Accordingly, many facets of KRAS biology are still unknown. Antibodies could be an effective and easy-to-use tool for in vitro and in vivo research on KRAS. Here, we generated a novel rabbit polyclonal antibody that allows immunolabeling of cells and tissues overexpressing KRAS. Cell transfection experiments with expression vectors for the members of the RAS family revealed a preferential specificity of this antibody for KRAS. In addition, KRAS was sensitively detected in a mouse tissue electroporated with an expression vector. Interestingly, our antibody was able to detect endogenous forms of unprenylated (immature) and prenylated (mature) KRAS in mouse organs. We found that KRAS prenylation was increased ex vivo and in vivo in a model of KRASG12D-driven tumorigenesis, which was concomitant with an induction of expression of essential KRAS prenylation enzymes. Therefore, our tool helped us to put the light on new regulations of KRAS activation during cancer initiation. The use of this tool by the RAS community could contribute to discovering novel aspects of KRAS biology.
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Affiliation(s)
- Mohamad Assi
- de Duve Institute, Université Catholique de Louvain, 1200 Brussels, Belgium
- Correspondence: (M.A.); (P.J.); Tel.: +32-2764-75-31 (M.A. & P.J.)
| | - Boris Pirlot
- Institut de Recherche Expérimentale et Clinique, Université catholique de Louvain, 1200 Brussels, Belgium; (B.P.); (J.-P.T.)
| | - Vincent Stroobant
- Ludwig Institute for Cancer Research, Université Catholique de Louvain, 1200 Brussels, Belgium;
| | - Jean-Paul Thissen
- Institut de Recherche Expérimentale et Clinique, Université catholique de Louvain, 1200 Brussels, Belgium; (B.P.); (J.-P.T.)
| | - Patrick Jacquemin
- de Duve Institute, Université Catholique de Louvain, 1200 Brussels, Belgium
- Correspondence: (M.A.); (P.J.); Tel.: +32-2764-75-31 (M.A. & P.J.)
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Human arylamine N-acetyltransferase 2 genotype-dependent protein expression in cryopreserved human hepatocytes. Sci Rep 2020; 10:7566. [PMID: 32372066 PMCID: PMC7200704 DOI: 10.1038/s41598-020-64508-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 04/16/2020] [Indexed: 01/08/2023] Open
Abstract
Human N-acetyltransferases (NAT; EC 2.3.1.5) catalyze the N-acetylation of arylamine and hydrazine drugs and the O-acetylation of N-hydroxylated metabolites of aromatic and heterocyclic amines. Two different isoforms of this protein, N-acetyltransferase 1 (NAT1) and N-acetyltransferase 2 (NAT2), are expressed in human hepatocytes. Both are encoded by a single 870-bp open reading frame that exhibits genetic polymorphisms in human populations. NAT1 and NAT2 share more than 85% gene and protein sequence, making it challenging to produce antibodies with high specificity for NAT1 or NAT2. In the present study, we compared methods for the quantification of immunoreactive NAT1 and NAT2 with seven different antibodies and investigated the relationship of NAT2 genotype to NAT2 mRNA and protein expression in cryopreserved human hepatocytes. Sulfamethazine (NAT2-selective substrate) and NAT2 protein expression differed significantly with NAT2 acetylator genotype (p < 0.0001). NAT2 protein expression and sulfamethazine NAT2 catalytic activity correlated highly across the cryopreserved human hepatocytes of rapid, intermediate, and slow acetylator NAT2 genotypes. In conclusion, our data describe a specific analytical method for the quantification of NAT1 and NAT2 protein expression. We showed that the NAT2 activity in human hepatocytes is directly correlated to expression levels of NAT2 protein but not mRNA.
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25
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Abstract
Monoclonal antibodies recognize epitopes so specifically that altering a single residue can disrupt binding. In this issue of Science Signaling, Schüchner et al and Frohner et al report that flanking amino acids and an underappreciated posttranslational modification perturb epitope affinity for two groups of widely used monoclonal antibodies.
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Affiliation(s)
- Kevin A Janes
- Departments of Biomedical Engineering and Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA 22908, USA.
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26
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Abstract
Parathyroid hormone (PTH), PTH-related peptide (PTHrP), PTHR, and their cognate G protein-coupled receptor play defining roles in the regulation of extracellular calcium and phosphate metabolism and in controlling skeletal growth and repair. Acting through complex signaling mechanisms that in many instances proceed in a tissue-specific manner, precise control of these processes is achieved. A variety of direct and indirect disease processes, along with genetic anomalies, can cause these schemes to become dysfunctional. Here, we review the basic components of this regulatory network and present both the well-established elements and emerging findings and concepts with the overall objective to provide a framework for understanding the elementary aspects of how PTH and PTHrP behave and as a call to encourage further investigation that will yield more comprehensive understanding of the physiological and pathological steps at play, with a goal toward novel therapeutic interventions.
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