1
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Armanious GP, Lemieux MJ, Espinoza-Fonseca LM, Young HS. Missense variants in phospholamban and cardiac myosin binding protein identified in patients with a family history and clinical diagnosis of dilated cardiomyopathy. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2024; 1871:119699. [PMID: 38387507 DOI: 10.1016/j.bbamcr.2024.119699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 11/07/2023] [Accepted: 02/15/2024] [Indexed: 02/24/2024]
Abstract
As the genetic landscape of cardiomyopathies continues to expand, the identification of missense variants in disease-associated genes frequently leads to a classification of variant of uncertain significance (VUS). For the proper reclassification of such variants, functional characterization is an important contributor to the proper assessment of pathogenic potential. Several missense variants in the calcium transport regulatory protein phospholamban have been associated with dilated cardiomyopathy. However, >40 missense variants in this transmembrane peptide are currently known and most remain classified as VUS with little clinical information. Similarly, missense variants in cardiac myosin binding protein have been associated with hypertrophic cardiomyopathy. However, hundreds of variants are known and many have low penetrance and are often found in control populations. Herein, we focused on novel missense variants in phospholamban, an Ala15-Thr variant found in a 4-year-old female and a Pro21-Thr variant found in a 60-year-old female, both with a family history and clinical diagnosis of dilated cardiomyopathy. The patients also harbored a Val896-Met variant in cardiac myosin binding protein. The phospholamban variants caused defects in the function, phosphorylation, and dephosphorylation of this calcium transport regulatory peptide, and we classified these variants as potentially pathogenic. The variant in cardiac myosin binding protein alters the structure of the protein. While this variant has been classified as benign, it has the potential to be a low-risk susceptibility variant because of the structural change in cardiac myosin binding protein. Our studies provide new biochemical evidence for missense variants previously classified as benign or VUS.
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Affiliation(s)
- Gareth P Armanious
- Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
| | - M Joanne Lemieux
- Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
| | - L Michel Espinoza-Fonseca
- Center for Arrhythmia Research, Department of Internal Medicine, Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, MI 48109, USA
| | - Howard S Young
- Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.
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2
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Corda PO, Bollen M, Ribeiro D, Fardilha M. Emerging roles of the Protein Phosphatase 1 (PP1) in the context of viral infections. Cell Commun Signal 2024; 22:65. [PMID: 38267954 PMCID: PMC10807198 DOI: 10.1186/s12964-023-01468-8] [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: 10/16/2023] [Accepted: 12/30/2023] [Indexed: 01/26/2024] Open
Abstract
Protein Phosphatase 1 (PP1) is a major serine/threonine phosphatase in eukaryotes, participating in several cellular processes and metabolic pathways. Due to their low substrate specificity, PP1's catalytic subunits do not exist as free entities but instead bind to Regulatory Interactors of Protein Phosphatase One (RIPPO), which regulate PP1's substrate specificity and subcellular localization. Most RIPPOs bind to PP1 through combinations of short linear motifs (4-12 residues), forming highly specific PP1 holoenzymes. These PP1-binding motifs may, hence, represent attractive targets for the development of specific drugs that interfere with a subset of PP1 holoenzymes. Several viruses exploit the host cell protein (de)phosphorylation machinery to ensure efficient virus particle formation and propagation. While the role of many host cell kinases in viral life cycles has been extensively studied, the targeting of phosphatases by viral proteins has been studied in less detail. Here, we compile and review what is known concerning the role of PP1 in the context of viral infections and discuss how it may constitute a putative host-based target for the development of novel antiviral strategies.
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Affiliation(s)
- Pedro O Corda
- Institute of Biomedicine (iBiMED), Department of Medical Sciences, University of Aveiro, Aveiro, Portugal
| | - Mathieu Bollen
- Department of Cellular and Molecular Medicine, Laboratory of Biosignaling & Therapeutics, Katholieke Universiteit Leuven, Louvain, Belgium
| | - Daniela Ribeiro
- Institute of Biomedicine (iBiMED), Department of Medical Sciences, University of Aveiro, Aveiro, Portugal.
| | - Margarida Fardilha
- Institute of Biomedicine (iBiMED), Department of Medical Sciences, University of Aveiro, Aveiro, Portugal.
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3
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Xiao Y, Chen Y, Chen J, Dong J. ASPP2 Is Phosphorylated by CDK1 during Mitosis and Required for Pancreatic Cancer Cell Proliferation. Cancers (Basel) 2023; 15:5424. [PMID: 38001686 PMCID: PMC10670399 DOI: 10.3390/cancers15225424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Revised: 11/10/2023] [Accepted: 11/13/2023] [Indexed: 11/26/2023] Open
Abstract
(1) Background: pancreatic cancer is highly lethal. The role of apoptosis-stimulating protein of p53-2 (ASPP2) in this lethal disease remains unclear. This protein belongs to the ASPP family of p53 interacting proteins. Previous studies in this lab used phosphate-binding tag (Phos-tag) sodium dodecyl sulfate (SDS) polyacrylamide gels and identified a motility upshift of the ASPP family of proteins during mitosis. (2) Purpose: this study expands on previous findings to identify the detailed phosphorylation regulation of ASPP2 during mitosis, as well as the function of ASPP2 in pancreatic cancer. (3) Methods: the Phos-tag technique was used to investigate the phosphorylation mechanism of ASPP2 during mitosis. Phospho-specific antibodies were generated to validate the phosphorylation of ASPP2, and ASPP2-inducible expression cell lines were established to determine the role of ASPP2 in pancreatic cancer. RNA sequencing (RNA-Seq) was used to uncover the downstream targets of ASPP2. (4) Results: results demonstrate that ASPP2 is phosphorylated during mitosis by cyclin-dependent kinase 1 (CDK1) at sites S562 and S704. In vitro and in vivo results show that ASPP2 is required for pancreatic cancer growth. Furthermore, the expressions of yes-associated protein (YAP)-related genes are found to be dramatically altered by ASPP2 depletion. Together, these findings reveal the phosphorylation mechanism of ASPP2 during mitosis. Collectively, results strongly indicate that ASPP2 is a potential target for abating tumor cell growth in pancreatic cancer.
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Affiliation(s)
| | | | | | - Jixin Dong
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198, USA; (Y.X.); (Y.C.); (J.C.)
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4
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Kieft R, Zhang Y, Yan H, Schmitz RJ, Sabatini R. Knockout of protein phosphatase 1 in Leishmania major reveals its role during RNA polymerase II transcription termination. Nucleic Acids Res 2023; 51:6208-6226. [PMID: 37194692 PMCID: PMC10325913 DOI: 10.1093/nar/gkad394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Revised: 04/26/2023] [Accepted: 05/04/2023] [Indexed: 05/18/2023] Open
Abstract
The genomes of kinetoplastids are organized into polycistronic transcription units that are flanked by a modified DNA base (base J, beta-D-glucosyl-hydroxymethyluracil). Previous work established a role of base J in promoting RNA polymerase II (Pol II) termination in Leishmania major and Trypanosoma brucei. We recently identified a PJW/PP1 complex in Leishmania containing a J-binding protein (JBP3), PP1 phosphatase 1, PP1 interactive-regulatory protein (PNUTS) and Wdr82. Analyses suggested the complex regulates transcription termination by recruitment to termination sites via JBP3-base J interactions and dephosphorylation of proteins, including Pol II, by PP1. However, we never addressed the role of PP1, the sole catalytic component, in Pol II transcription termination. We now demonstrate that deletion of the PP1 component of the PJW/PP1 complex in L. major, PP1-8e, leads to readthrough transcription at the 3'-end of polycistronic gene arrays. We show PP1-8e has in vitro phosphatase activity that is lost upon mutation of a key catalytic residue and associates with PNUTS via the conserved RVxF motif. Additionally, purified PJW complex with associated PP1-8e, but not complex lacking PP1-8e, led to dephosphorylation of Pol II, suggesting a direct role of PNUTS/PP1 holoenzymes in regulating transcription termination via dephosphorylating Pol II in the nucleus.
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Affiliation(s)
- Rudo Kieft
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA30602, USA
| | - Yang Zhang
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA30602, USA
| | - Haidong Yan
- Department of Genetics, University of Georgia, Athens, GA30602, USA
| | - Robert J Schmitz
- Department of Genetics, University of Georgia, Athens, GA30602, USA
| | - Robert Sabatini
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA30602, USA
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5
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Beacham GM, Wei DT, Beyrent E, Zhang Y, Zheng J, Camacho MMK, Florens L, Hollopeter G. The Caenorhabditis elegans ASPP homolog APE-1 is a junctional protein phosphatase 1 modulator. Genetics 2022; 222:iyac102. [PMID: 35792852 PMCID: PMC9434228 DOI: 10.1093/genetics/iyac102] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Accepted: 06/28/2022] [Indexed: 08/19/2023] Open
Abstract
How serine/threonine phosphatases are spatially and temporally tuned by regulatory subunits is a fundamental question in cell biology. Ankyrin repeat, SH3 domain, proline-rich-region-containing proteins are protein phosphatase 1 catalytic subunit binding partners associated with cardiocutaneous diseases. Ankyrin repeat, SH3 domain, proline-rich-region-containing proteins localize protein phosphatase 1 catalytic subunit to cell-cell junctions, but how ankyrin repeat, SH3 domain, proline-rich-region-containing proteins localize and whether they regulate protein phosphatase 1 catalytic subunit activity in vivo is unclear. Through a Caenorhabditis elegans genetic screen, we find that loss of the ankyrin repeat, SH3 domain, proline-rich-region-containing protein homolog, APE-1, suppresses a pathology called "jowls," providing us with an in vivo assay for APE-1 activity. Using immunoprecipitations and mass spectrometry, we find that APE-1 binds the protein phosphatase 1 catalytic subunit called GSP-2. Through structure-function analysis, we discover that APE-1's N-terminal half directs the APE-1-GSP-2 complex to intercellular junctions. Additionally, we isolated mutations in highly conserved residues of APE-1's ankyrin repeats that suppress jowls yet do not preclude GSP-2 binding, implying APE-1 does more than simply localize GSP-2. Indeed, in vivo reconstitution of APE-1 suggests the ankyrin repeats modulate phosphatase output, a function we find to be conserved among vertebrate homologs.
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Affiliation(s)
| | - Derek T Wei
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Erika Beyrent
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Ying Zhang
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Jian Zheng
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Mari M K Camacho
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Laurence Florens
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Gunther Hollopeter
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
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6
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Royer C, Sandham E, Slee E, Schneider F, Lagerholm CB, Godwin J, Veits N, Hathrell H, Zhou F, Leonavicius K, Garratt J, Narendra T, Vincent A, Jones C, Child T, Coward K, Graham C, Fritzsche M, Lu X, Srinivas S. ASPP2 maintains the integrity of mechanically stressed pseudostratified epithelia during morphogenesis. Nat Commun 2022; 13:941. [PMID: 35177595 PMCID: PMC8854694 DOI: 10.1038/s41467-022-28590-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 01/28/2022] [Indexed: 11/09/2022] Open
Abstract
During development, pseudostratified epithelia undergo large scale morphogenetic events associated with increased mechanical stress. Using a variety of genetic and imaging approaches, we uncover that in the mouse E6.5 epiblast, where apical tension is highest, ASPP2 safeguards tissue integrity. It achieves this by preventing the most apical daughter cells from delaminating apically following division events. In this context, ASPP2 maintains the integrity and organisation of the filamentous actin cytoskeleton at apical junctions. ASPP2 is also essential during gastrulation in the primitive streak, in somites and in the head fold region, suggesting that it is required across a wide range of pseudostratified epithelia during morphogenetic events that are accompanied by intense tissue remodelling. Finally, our study also suggests that the interaction between ASPP2 and PP1 is essential to the tumour suppressor function of ASPP2, which may be particularly relevant in the context of tissues that are subject to increased mechanical stress. The early embryo maintains its structure in the face of large mechanical stresses during morphogenesis. Here they show that ASPP2 acts to preserve epithelial integrity in regions of high apical tension during early development.
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Affiliation(s)
- Christophe Royer
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, OX1 3QX, UK.
| | - Elizabeth Sandham
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, OX1 3QX, UK
| | - Elizabeth Slee
- Ludwig Institute for Cancer Research, Nuffield Department of Medicine, University of Oxford, Oxford, OX3 7DQ, UK
| | - Falk Schneider
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK.,Translational Imaging Center, University of Southern California, Los Angeles, CA, 90089, USA
| | - Christoffer B Lagerholm
- Wolfson Imaging Centre Oxford, MRC Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, UK
| | - Jonathan Godwin
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, OX1 3QX, UK.,Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
| | - Nisha Veits
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, OX1 3QX, UK
| | - Holly Hathrell
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, OX1 3QX, UK
| | - Felix Zhou
- Ludwig Institute for Cancer Research, Nuffield Department of Medicine, University of Oxford, Oxford, OX3 7DQ, UK
| | - Karolis Leonavicius
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, OX1 3QX, UK.,Institute of Biotechnology, Vilnius University, Vilnius, Lithuania
| | - Jemma Garratt
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, OX1 3QX, UK.,Nuffield Department of Women's and Reproductive Health, University of Oxford, Level 3, Women's Centre, John Radcliffe Hospital, Headington, Oxford, OX3 9DU, UK
| | - Tanaya Narendra
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, OX1 3QX, UK.,Nuffield Department of Women's and Reproductive Health, University of Oxford, Level 3, Women's Centre, John Radcliffe Hospital, Headington, Oxford, OX3 9DU, UK
| | - Anna Vincent
- Oxford Fertility, Institute of Reproductive Sciences, Oxford Business Park North, Oxford, OX4 2HW, UK
| | - Celine Jones
- Nuffield Department of Women's and Reproductive Health, University of Oxford, Level 3, Women's Centre, John Radcliffe Hospital, Headington, Oxford, OX3 9DU, UK
| | - Tim Child
- Nuffield Department of Women's and Reproductive Health, University of Oxford, Level 3, Women's Centre, John Radcliffe Hospital, Headington, Oxford, OX3 9DU, UK.,Oxford Fertility, Institute of Reproductive Sciences, Oxford Business Park North, Oxford, OX4 2HW, UK
| | - Kevin Coward
- Nuffield Department of Women's and Reproductive Health, University of Oxford, Level 3, Women's Centre, John Radcliffe Hospital, Headington, Oxford, OX3 9DU, UK
| | - Chris Graham
- Nuffield Department of Women's and Reproductive Health, University of Oxford, Level 3, Women's Centre, John Radcliffe Hospital, Headington, Oxford, OX3 9DU, UK
| | - Marco Fritzsche
- Kennedy Institute for Rheumatology, University of Oxford, Oxford, OX3 7LF, UK.,Rosalind Franklin Institute, Didcot, OX11 0QS, UK
| | - Xin Lu
- Ludwig Institute for Cancer Research, Nuffield Department of Medicine, University of Oxford, Oxford, OX3 7DQ, UK
| | - Shankar Srinivas
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, OX1 3QX, UK.
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7
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Mangon A, Salaün D, Bouali ML, Kuzmić M, Quitard S, Thuault S, Isnardon D, Audebert S, Puech PH, Verdier-Pinard P, Badache A. iASPP contributes to cell cortex rigidity, mitotic cell rounding, and spindle positioning. J Cell Biol 2021; 220:212730. [PMID: 34705028 PMCID: PMC8562848 DOI: 10.1083/jcb.202012002] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 08/03/2021] [Accepted: 09/19/2021] [Indexed: 12/27/2022] Open
Abstract
iASPP is a protein mostly known as an inhibitor of p53 pro-apoptotic activity and a predicted regulatory subunit of the PP1 phosphatase, which is often overexpressed in tumors. We report that iASPP associates with the microtubule plus-end binding protein EB1, a central regulator of microtubule dynamics, via an SxIP motif. iASPP silencing or mutation of the SxIP motif led to defective microtubule capture at the cortex of mitotic cells, leading to abnormal positioning of the mitotic spindle. These effects were recapitulated by the knockdown of the membrane-to-cortex linker Myosin-Ic (Myo1c), which we identified as a novel partner of iASPP. Moreover, iASPP or Myo1c knockdown cells failed to round up upon mitosis because of defective cortical stiffness. We propose that by increasing cortical rigidity, iASPP helps cancer cells maintain a spherical geometry suitable for proper mitotic spindle positioning and chromosome partitioning.
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Affiliation(s)
- Aurélie Mangon
- Centre de Recherche en Cancérologie de Marseille, Institut National de la Santé et de la Recherche Médicale, Institut Paoli-Calmettes, Aix-Marseille Université, Centre National de la Recherche Scientifique, Marseille, France
| | - Danièle Salaün
- Centre de Recherche en Cancérologie de Marseille, Institut National de la Santé et de la Recherche Médicale, Institut Paoli-Calmettes, Aix-Marseille Université, Centre National de la Recherche Scientifique, Marseille, France
| | - Mohamed Lala Bouali
- Centre de Recherche en Cancérologie de Marseille, Institut National de la Santé et de la Recherche Médicale, Institut Paoli-Calmettes, Aix-Marseille Université, Centre National de la Recherche Scientifique, Marseille, France
| | - Mira Kuzmić
- Centre de Recherche en Cancérologie de Marseille, Institut National de la Santé et de la Recherche Médicale, Institut Paoli-Calmettes, Aix-Marseille Université, Centre National de la Recherche Scientifique, Marseille, France
| | - Sabine Quitard
- Centre de Recherche en Cancérologie de Marseille, Institut National de la Santé et de la Recherche Médicale, Institut Paoli-Calmettes, Aix-Marseille Université, Centre National de la Recherche Scientifique, Marseille, France
| | - Sylvie Thuault
- Centre de Recherche en Cancérologie de Marseille, Institut National de la Santé et de la Recherche Médicale, Institut Paoli-Calmettes, Aix-Marseille Université, Centre National de la Recherche Scientifique, Marseille, France
| | - Daniel Isnardon
- Centre de Recherche en Cancérologie de Marseille, Institut National de la Santé et de la Recherche Médicale, Institut Paoli-Calmettes, Aix-Marseille Université, Centre National de la Recherche Scientifique, Marseille, France
| | - Stéphane Audebert
- Centre de Recherche en Cancérologie de Marseille, Institut National de la Santé et de la Recherche Médicale, Institut Paoli-Calmettes, Aix-Marseille Université, Centre National de la Recherche Scientifique, Marseille, France
| | - Pierre-Henri Puech
- Laboratoire Adhésion et Inflammation, Institut National de la Santé et de la Recherche Médicale, Centre National de la Recherche Scientifique, Aix Marseille Université, Turing Center for Living Systems, Marseille, France
| | - Pascal Verdier-Pinard
- Centre de Recherche en Cancérologie de Marseille, Institut National de la Santé et de la Recherche Médicale, Institut Paoli-Calmettes, Aix-Marseille Université, Centre National de la Recherche Scientifique, Marseille, France
| | - Ali Badache
- Centre de Recherche en Cancérologie de Marseille, Institut National de la Santé et de la Recherche Médicale, Institut Paoli-Calmettes, Aix-Marseille Université, Centre National de la Recherche Scientifique, Marseille, France
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8
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Specificity determinants of phosphoprotein phosphatases controlling kinetochore functions. Essays Biochem 2021; 64:325-336. [PMID: 32501472 DOI: 10.1042/ebc20190065] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 05/11/2020] [Accepted: 05/14/2020] [Indexed: 12/12/2022]
Abstract
Kinetochores are instrumental for accurate chromosome segregation by binding to microtubules in order to move chromosomes and by delaying anaphase onset through the spindle assembly checkpoint (SAC). Dynamic phosphorylation of kinetochore components is key to control these activities and is tightly regulated by temporal and spatial recruitment of kinases and phosphoprotein phosphatases (PPPs). Here we focus on PP1, PP2A-B56 and PP2A-B55, three PPPs that are important regulators of mitosis. Despite the fact that these PPPs share a very similar active site, they target unique ser/thr phosphorylation sites to control kinetochore function. Specificity is in part achieved by PPPs binding to short linear motifs (SLiMs) that guide their substrate specificity. SLiMs bind to conserved pockets on PPPs and are degenerate in nature, giving rise to a range of binding affinities. These SLiMs control the assembly of numerous substrate specifying complexes and their position and binding strength allow PPPs to target specific phosphorylation sites. In addition, the activity of PPPs is regulated by mitotic kinases and inhibitors, either directly at the activity level or through affecting PPP-SLiM interactions. Here, we discuss recent progress in understanding the regulation of PPP specificity and activity and how this controls kinetochore biology.
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9
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Salvi F, Hoermann B, Del Pino García J, Fontanillo M, Derua R, Beullens M, Bollen M, Barabas O, Köhn M. Towards Dissecting the Mechanism of Protein Phosphatase-1 Inhibition by Its C-Terminal Phosphorylation. Chembiochem 2020; 22:834-838. [PMID: 33085143 PMCID: PMC7984433 DOI: 10.1002/cbic.202000669] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Revised: 10/21/2020] [Indexed: 01/23/2023]
Abstract
Phosphoprotein phosphatase‐1 (PP1) is a key player in the regulation of phospho‐serine (pSer) and phospho‐threonine (pThr) dephosphorylation and is involved in a large fraction of cellular signaling pathways. Aberrant activity of PP1 has been linked to many diseases, including cancer and heart failure. Besides a well‐established activity control by regulatory proteins, an inhibitory function for phosphorylation (p) of a Thr residue in the C‐terminal intrinsically disordered tail of PP1 has been demonstrated. The associated phenotype of cell‐cycle arrest was repeatedly proposed to be due to autoinhibition of PP1 through either conformational changes or substrate competition. Here, we use PP1 variants created by mutations and protein semisynthesis to differentiate between these hypotheses. Our data support the hypothesis that pThr exerts its inhibitory function by mediating protein complex formation rather than by a direct mechanism of structural changes or substrate competition.
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Affiliation(s)
- Francesca Salvi
- Genome Biology Unit, European Molecular Biology Laboratory, Meyerhofstraße 1, 69117, Heidelberg, Germany
| | - Bernhard Hoermann
- Signalling Research Centres BIOSS and CIBSS, University of Freiburg, Schänzlestraße 18, 79104, Freiburg, Germany.,Faculty of Biology, University of Freiburg, Schänzlestraße 18, 79104, Freiburg, Germany
| | - Javier Del Pino García
- Laboratory of Biosignaling and Therapeutics Department of Cellular and Molecular Medicine, KU Leuven, Herestraat 49, 3000, Leuven, Belgium
| | - Miriam Fontanillo
- Genome Biology Unit, European Molecular Biology Laboratory, Meyerhofstraße 1, 69117, Heidelberg, Germany
| | - Rita Derua
- Laboratory of Protein Phosphorylation and Proteomics Department of Cellular and Molecular Medicine, KU Leuven, Herestraat 49, 3000, Leuven, Belgium.,SyBioMa, KU Leuven, Herestraat 49, 3000, Leuven, Belgium
| | - Monique Beullens
- Laboratory of Biosignaling and Therapeutics Department of Cellular and Molecular Medicine, KU Leuven, Herestraat 49, 3000, Leuven, Belgium
| | - Mathieu Bollen
- Laboratory of Biosignaling and Therapeutics Department of Cellular and Molecular Medicine, KU Leuven, Herestraat 49, 3000, Leuven, Belgium
| | - Orsolya Barabas
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Meyerhofstraße 1, 69117, Heidelberg, Germany
| | - Maja Köhn
- Genome Biology Unit, European Molecular Biology Laboratory, Meyerhofstraße 1, 69117, Heidelberg, Germany.,Signalling Research Centres BIOSS and CIBSS, University of Freiburg, Schänzlestraße 18, 79104, Freiburg, Germany.,Faculty of Biology, University of Freiburg, Schänzlestraße 18, 79104, Freiburg, Germany
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10
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Protein phosphatase 1 in tumorigenesis: is it worth a closer look? Biochim Biophys Acta Rev Cancer 2020; 1874:188433. [PMID: 32956763 DOI: 10.1016/j.bbcan.2020.188433] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 08/26/2020] [Accepted: 09/12/2020] [Indexed: 02/06/2023]
Abstract
Cancer cells take advantage of signaling cascades to meet their requirements for sustained growth and survival. Cell signaling is tightly controlled by reversible protein phosphorylation mechanisms, which require the counterbalanced action of protein kinases and protein phosphatases. Imbalances on this system are associated with cancer development and progression. Protein phosphatase 1 (PP1) is one of the most relevant protein phosphatases in eukaryotic cells. Despite the widely recognized involvement of PP1 in key biological processes, both in health and disease, its relevance in cancer has been largely neglected. Here, we provide compelling evidence that support major roles for PP1 in tumorigenesis.
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11
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Guarné A. The More the Merrier: When Four Interfaces Are Better Than One. Structure 2020; 27:1483-1484. [PMID: 31577936 DOI: 10.1016/j.str.2019.09.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In this issue of Structure, Zhou et al. (2019) determine the crystal and solution structures of iASPP bound to PP1. The proteins interact through a discontinuous interface defined by four contact points. Association/dissociation of individual contacts enables the transition between multiple conformations and provides mechanistic insight into how ASPPs regulate phosphorylation of p53.
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Affiliation(s)
- Alba Guarné
- Department of Biochemistry, McGill University, Montreal, QC H3G 0B1, Canada.
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12
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Zhou Y, Millott R, Kim HJ, Peng S, Edwards RA, Skene-Arnold T, Hammel M, Lees-Miller SP, Tainer JA, Holmes CFB, Glover JNM. Flexible Tethering of ASPP Proteins Facilitates PP-1c Catalysis. Structure 2019; 27:1485-1496.e4. [PMID: 31402222 DOI: 10.1016/j.str.2019.07.012] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Revised: 06/14/2019] [Accepted: 07/22/2019] [Indexed: 12/15/2022]
Abstract
ASPP (apoptosis-stimulating proteins of p53) proteins bind PP-1c (protein phosphatase 1) and regulate p53 impacting cancer cell growth and apoptosis. Here we determine the crystal structure of the oncogenic ASPP protein, iASPP, bound to PP-1c. The structure reveals a 1:1 complex that relies on interactions of the iASPP SILK and RVxF motifs with PP-1c, plus interactions of the PP-1c PxxPxR motif with the iASPP SH3 domain. Small-angle X-ray scattering analyses suggest that the crystal structure undergoes slow interconversion with more extended conformations in solution. We show that iASPP, and the tumor suppressor ASPP2, enhance the catalytic activity of PP-1c against the small-molecule substrate, pNPP as well as p53. The combined results suggest that PxxPxR binding to iASPP SH3 domain is critical for complex formation, and that the modular ASPP-PP-1c interface provides dynamic flexibility that enables functional binding and dephosphorylation of p53 and other diverse protein substrates.
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Affiliation(s)
- Yeyun Zhou
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Robyn Millott
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Hyeong Jin Kim
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Shiyun Peng
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Ross A Edwards
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Tamara Skene-Arnold
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Michal Hammel
- Molecular Biophysics & Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Susan P Lees-Miller
- Department of Biochemistry and Molecular Biology, Arnie Charbonneau Cancer Institute, University of Calgary, Calgary, AB, Canada
| | - John A Tainer
- Molecular Biophysics & Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; Department of Molecular and Cellular Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA
| | - Charles F B Holmes
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada.
| | - J N Mark Glover
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada.
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13
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Bertran MT, Mouilleron S, Zhou Y, Bajaj R, Uliana F, Kumar GS, van Drogen A, Lee R, Banerjee JJ, Hauri S, O'Reilly N, Gstaiger M, Page R, Peti W, Tapon N. ASPP proteins discriminate between PP1 catalytic subunits through their SH3 domain and the PP1 C-tail. Nat Commun 2019; 10:771. [PMID: 30770806 PMCID: PMC6377682 DOI: 10.1038/s41467-019-08686-0] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Accepted: 01/25/2019] [Indexed: 11/26/2022] Open
Abstract
Serine/threonine phosphatases such as PP1 lack substrate specificity and associate with a large array of targeting subunits to achieve the requisite selectivity. The tumour suppressor ASPP (apoptosis-stimulating protein of p53) proteins associate with PP1 catalytic subunits and are implicated in multiple functions from transcriptional regulation to cell junction remodelling. Here we show that Drosophila ASPP is part of a multiprotein PP1 complex and that PP1 association is necessary for several in vivo functions of Drosophila ASPP. We solve the crystal structure of the human ASPP2/PP1 complex and show that ASPP2 recruits PP1 using both its canonical RVxF motif, which binds the PP1 catalytic domain, and its SH3 domain, which engages the PP1 C-terminal tail. The ASPP2 SH3 domain can discriminate between PP1 isoforms using an acidic specificity pocket in the n-Src domain, providing an exquisite mechanism where multiple motifs are used combinatorially to tune binding affinity to PP1.
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Affiliation(s)
- M Teresa Bertran
- Apoptosis and Proliferation Control Laboratory, The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK
| | - Stéphane Mouilleron
- Structural Biology - Science Technology Platform, The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK.
| | - Yanxiang Zhou
- Apoptosis and Proliferation Control Laboratory, The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK
| | - Rakhi Bajaj
- Chemistry and Biochemistry Department, University of Arizona, 1041 E. Lowell Street, Biosciences West, 517, Tucson, AZ, 85721, USA
| | - Federico Uliana
- Department of Biology, Institute of Molecular Systems Biology, ETH Zürich, 8093, Zürich, Switzerland
| | - Ganesan Senthil Kumar
- Chemistry and Biochemistry Department, University of Arizona, 1041 E. Lowell Street, Biosciences West, 517, Tucson, AZ, 85721, USA
| | - Audrey van Drogen
- Department of Biology, Institute of Molecular Systems Biology, ETH Zürich, 8093, Zürich, Switzerland
| | - Rebecca Lee
- Structural Biology - Science Technology Platform, The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK
| | - Jennifer J Banerjee
- Apoptosis and Proliferation Control Laboratory, The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK
| | - Simon Hauri
- Department of Biology, Institute of Molecular Systems Biology, ETH Zürich, 8093, Zürich, Switzerland
| | - Nicola O'Reilly
- Peptide Chemistry Laboratory, The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK
| | - Matthias Gstaiger
- Department of Biology, Institute of Molecular Systems Biology, ETH Zürich, 8093, Zürich, Switzerland
| | - Rebecca Page
- Chemistry and Biochemistry Department, University of Arizona, 1041 E. Lowell Street, Biosciences West, 517, Tucson, AZ, 85721, USA
| | - Wolfgang Peti
- Chemistry and Biochemistry Department, University of Arizona, 1041 E. Lowell Street, Biosciences West, 517, Tucson, AZ, 85721, USA
| | - Nicolas Tapon
- Apoptosis and Proliferation Control Laboratory, The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK.
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14
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Gan W, Zhao H, Li T, Liu K, Huang J. CDK1 interacts with iASPP to regulate colorectal cancer cell proliferation through p53 pathway. Oncotarget 2017; 8:71618-71629. [PMID: 29069733 PMCID: PMC5641076 DOI: 10.18632/oncotarget.17794] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Accepted: 04/26/2017] [Indexed: 01/19/2023] Open
Abstract
CDK1 (cyclin-dependent kinase 1) is a critical regulator of the G2-M checkpoint. CDK1 is considered a possible target for cancer treatment. In addition to CDK1, iASPP plays essential role in maintaining cancer cell proliferation. In the present study, we monitored the expression of CDK1 and iASPP at mRNA and protein levels in CRC tissues and cell lines; we also predicted that iASPP protein might interact with CDK1 protein. By performing GST pull-down assay and Co-IP assay, we confirmed the interaction of CDK1 and iASPP protein. In CRC cell lines, CDK1 interacted with iASPP to affect CRC cell proliferation and apoptosis; moreover, the p53 apoptosis pathway was involved in this progression. Taken together, we revealed that CDK1 and iASPP was up-regulated in CRC tissues and cell lines; CDK1 protein interacted with iASPP protein to affect CRC cell proliferation and apoptosis through the p53 apoptosis pathway. CDK1 and iASPP might serve as not only promising targets in CRC treatment, but also efficient prognostic markers. From the perspective of protein interactions, we provided a novel theoretical basis for targeted therapy of CRC.
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Affiliation(s)
- Wei Gan
- Department of General Surgery, the Second Xiangya Hospital, Central South University, Changsha 410011, Hunan, China
| | - Hua Zhao
- Department of General Surgery, the Second Xiangya Hospital, Central South University, Changsha 410011, Hunan, China
| | - Tiegang Li
- Department of General Surgery, the Second Xiangya Hospital, Central South University, Changsha 410011, Hunan, China
| | - Kuijie Liu
- Department of General Surgery, the Second Xiangya Hospital, Central South University, Changsha 410011, Hunan, China
| | - Jiangsheng Huang
- Department of Minimally Invasive Surgery, the Second Xiangya Hospital, Central South University, Changsha 410011, Hunan, China
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15
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The Human Adenovirus Type 5 E4orf4 Protein Targets Two Phosphatase Regulators of the Hippo Signaling Pathway. J Virol 2015; 89:8855-70. [PMID: 26085163 DOI: 10.1128/jvi.03710-14] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Accepted: 06/05/2015] [Indexed: 12/13/2022] Open
Abstract
UNLABELLED When expressed alone at high levels, the human adenovirus E4orf4 protein exhibits tumor cell-specific p53-independent toxicity. A major E4orf4 target is the B55 class of PP2A regulatory subunits, and we have shown recently that binding of E4orf4 inhibits PP2A(B55) phosphatase activity in a dose-dependent fashion by preventing access of substrates (M. Z. Mui et al., PLoS Pathog 9:e1003742, 2013, http://dx.doi.org/10.1371/journal.ppat.1003742). While interaction with B55 subunits is essential for toxicity, E4orf4 mutants exist that, despite binding B55 at high levels, are defective in cell killing, suggesting that other essential targets exist. In an attempt to identify additional targets, we undertook a proteomics approach to characterize E4orf4-interacting proteins. Our findings indicated that, in addition to PP2A(B55) subunits, ASPP-PP1 complex subunits were found among the major E4orf4-binding species. Both the PP2A and ASPP-PP1 phosphatases are known to positively regulate effectors of the Hippo signaling pathway, which controls the expression of cell growth/survival genes by dephosphorylating the YAP transcriptional coactivator. We find here that expression of E4orf4 results in hyperphosphorylation of YAP, suggesting that Hippo signaling is affected by E4orf4 interactions with PP2A(B55) and/or ASPP-PP1 phosphatases. Furthermore, knockdown of YAP1 expression was seen to enhance E4orf4 killing, again consistent with a link between E4orf4 toxicity and inhibition of the Hippo pathway. This effect may in fact contribute to the cancer cell specificity of E4orf4 toxicity, as many human cancer cells rely heavily on the Hippo pathway for their enhanced proliferation. IMPORTANCE The human adenovirus E4orf4 protein has been known for some time to induce tumor cell-specific death when expressed at high levels; thus, knowledge of its mode of action could be of importance for development of new cancer therapies. Although the B55 form of the phosphatase PP2A has long been known as an essential E4orf4 target, genetic analyses indicated that others must exist. To identify additional E4orf4 targets, we performed, for the first time, a large-scale affinity purification/mass spectrometry analysis of E4orf4 binding partners. Several additional candidates were detected, including key regulators of the Hippo signaling pathway, which enhances cell viability in many cancers, and results of preliminary studies suggested a link between inhibition of Hippo signaling and E4orf4 toxicity.
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16
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iASPP, a previously unidentified regulator of desmosomes, prevents arrhythmogenic right ventricular cardiomyopathy (ARVC)-induced sudden death. Proc Natl Acad Sci U S A 2015; 112:E973-81. [PMID: 25691752 DOI: 10.1073/pnas.1408111112] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Desmosomes are anchoring junctions that exist in cells that endure physical stress such as cardiac myocytes. The importance of desmosomes in maintaining the homeostasis of the myocardium is underscored by frequent mutations of desmosome components found in human patients and animal models. Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a phenotype caused by mutations in desmosomal components in ∼ 50% of patients, however, the causes in the remaining 50% of patients still remain unknown. A deficiency of inhibitor of apoptosis-stimulating protein of p53 (iASPP), an evolutionarily conserved inhibitor of p53, caused by spontaneous mutation recently has been associated with a lethal autosomal recessive cardiomyopathy in Poll Hereford calves and Wa3 mice. However, the molecular mechanisms that mediate this putative function of iASPP are completely unknown. Here, we show that iASPP is expressed at intercalated discs in human and mouse postmitotic cardiomyocytes. iASPP interacts with desmoplakin and desmin in cardiomyocytes to maintain the integrity of desmosomes and intermediate filament networks in vitro and in vivo. iASPP deficiency specifically induces right ventricular dilatation in mouse embryos at embryonic day 16.5. iASPP-deficient mice with exon 8 deletion (Ppp1r13l(Δ8/Δ8)) die of sudden cardiac death, displaying features of ARVC. Intercalated discs in cardiomyocytes from four of six human ARVC cases show reduced or loss of iASPP. ARVC-derived desmoplakin mutants DSP-1-V30M and DSP-1-S299R exhibit weaker binding to iASPP. These data demonstrate that by interacting with desmoplakin and desmin, iASPP is an important regulator of desmosomal function both in vitro and in vivo. This newly identified property of iASPP may provide new molecular insight into the pathogenesis of ARVC.
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17
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Korrodi-Gregório L, Esteves SLC, Fardilha M. Protein phosphatase 1 catalytic isoforms: specificity toward interacting proteins. Transl Res 2014; 164:366-91. [PMID: 25090308 DOI: 10.1016/j.trsl.2014.07.001] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Revised: 06/26/2014] [Accepted: 07/01/2014] [Indexed: 01/21/2023]
Abstract
The coordinated and reciprocal action of serine-threonine protein kinases and protein phosphatases produces transitory phosphorylation, a fundamental regulatory mechanism for many biological processes. Phosphoprotein phosphatase 1 (PPP1), a major serine-threonine phosphatase, in particular, is ubiquitously distributed and regulates a broad range of cellular functions, including glycogen metabolism, cell cycle progression, and muscle relaxation. PPP1 has evolved effective catalytic machinery but in vitro lacks substrate specificity. In vivo, its specificity is achieved not only by the existence of different PPP1 catalytic isoforms, but also by binding of the catalytic moiety to a large number of regulatory or targeting subunits. Here, we will address exhaustively the existence of diverse PPP1 catalytic isoforms and the relevance of their specific partners and consequent functions.
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Affiliation(s)
- Luís Korrodi-Gregório
- Laboratório de Transdução de Sinais, Departamento de Biologia, Secção Autónoma de Ciências de Saúde, Centro de Biologia Celular, Universidade de Aveiro, Aveiro, Portugal
| | - Sara L C Esteves
- Laboratório de Transdução de Sinais, Departamento de Biologia, Secção Autónoma de Ciências de Saúde, Centro de Biologia Celular, Universidade de Aveiro, Aveiro, Portugal
| | - Margarida Fardilha
- Laboratório de Transdução de Sinais, Departamento de Biologia, Secção Autónoma de Ciências de Saúde, Centro de Biologia Celular, Universidade de Aveiro, Aveiro, Portugal.
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18
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ASPP2 links the apical lateral polarity complex to the regulation of YAP activity in epithelial cells. PLoS One 2014; 9:e111384. [PMID: 25360797 PMCID: PMC4216074 DOI: 10.1371/journal.pone.0111384] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2014] [Accepted: 09/23/2014] [Indexed: 12/28/2022] Open
Abstract
The Hippo pathway, by tightly controlling the phosphorylation state and activity of the transcription cofactors YAP and TAZ is essential during development and tissue homeostasis whereas its deregulation may lead to cancer. Recent studies have linked the apicobasal polarity machinery in epithelial cells to components of the Hippo pathway and YAP and TAZ themselves. However the molecular mechanism by which the junctional pool of YAP proteins is released and activated in epithelial cells remains unknown. Here we report that the tumour suppressor ASPP2 forms an apical-lateral polarity complex at the level of tight junctions in polarised epithelial cells, acting as a scaffold for protein phosphatase 1 (PP1) and junctional YAP via dedicated binding domains. ASPP2 thereby directly induces the dephosphorylation and activation of junctional YAP. Collectively, this study unearths a novel mechanistic paradigm revealing the critical role of the apical-lateral polarity complex in activating this localised pool of YAP in vitro, in epithelial cells, and in vivo, in the murine colonic epithelium. We propose that this mechanism may commonly control YAP functions in epithelial tissues.
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19
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Öhman T, Söderholm S, Hintsanen P, Välimäki E, Lietzén N, MacKintosh C, Aittokallio T, Matikainen S, Nyman TA. Phosphoproteomics combined with quantitative 14-3-3-affinity capture identifies SIRT1 and RAI as novel regulators of cytosolic double-stranded RNA recognition pathway. Mol Cell Proteomics 2014; 13:2604-17. [PMID: 24997996 DOI: 10.1074/mcp.m114.038968] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Viral double-stranded RNA (dsRNA) is the most important viral structure recognized by cytosolic pattern-recognition receptors of the innate immune system, and its recognition results in the activation of signaling cascades that stimulate the production of antiviral cytokines and apoptosis of infected cells. 14-3-3 proteins are ubiquitously expressed regulatory molecules that participate in a variety of cellular processes, and 14-3-3 protein-mediated signaling pathways are activated by cytoplasmic dsRNA in human keratinocytes. However, the functional role of 14-3-3 protein-mediated interactions during viral dsRNA stimulation has remained uncharacterized. Here, we used functional proteomics to identify proteins whose phosphorylation and interaction with 14-3-3 is modulated by dsRNA and to characterize the signaling pathways activated during cytosolic dsRNA-induced innate immune response in human HaCaT keratinocytes. Phosphoproteome analysis showed that several MAPK- and immune-response-related signaling pathways were activated after dsRNA stimulation. Interactome analysis identified RelA-associated inhibitor, high-mobility group proteins, and several proteins associated with host responses to viral infection as novel 14-3-3 target proteins. Functional studies showed that RelA-associated inhibitor regulated dsRNA-induced apoptosis and TNF production. Integrated network analyses of proteomic data revealed that sirtuin1 was a central molecule regulated by 14-3-3s during dsRNA stimulation. Further experiments showed that sirtuin 1 negatively regulated dsRNA-induced NFκB transcriptional activity, suppressed expression of antiviral cytokines, and protected cells from apoptosis in dsRNA-stimulated and encephalomyocarditis-virus-infected keratinocytes. In conclusion, our data highlight the importance of 14-3-3 proteins in antiviral responses and identify RelA-associated inhibitor and sirtuin 1 as novel regulators of antiviral innate immune responses.
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Affiliation(s)
- Tiina Öhman
- From the ‡Institute of Biotechnology, FI-00014 University of Helsinki, Helsinki, Finland
| | - Sandra Söderholm
- From the ‡Institute of Biotechnology, FI-00014 University of Helsinki, Helsinki, Finland; §Finnish Institute of Occupational Health, FI-00250 Helsinki, Finland
| | - Petteri Hintsanen
- ¶Institute for Molecular Medicine Finland (FIMM), FI-00014 University of Helsinki, Helsinki, Finland
| | - Elina Välimäki
- From the ‡Institute of Biotechnology, FI-00014 University of Helsinki, Helsinki, Finland; §Finnish Institute of Occupational Health, FI-00250 Helsinki, Finland
| | - Niina Lietzén
- From the ‡Institute of Biotechnology, FI-00014 University of Helsinki, Helsinki, Finland
| | - Carol MacKintosh
- **University of Dundee, Dundee, Scotland DD1 5EH, United Kingdom
| | - Tero Aittokallio
- ¶Institute for Molecular Medicine Finland (FIMM), FI-00014 University of Helsinki, Helsinki, Finland
| | - Sampsa Matikainen
- §Finnish Institute of Occupational Health, FI-00250 Helsinki, Finland
| | - Tuula A Nyman
- From the ‡Institute of Biotechnology, FI-00014 University of Helsinki, Helsinki, Finland;
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20
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Understanding the antagonism of retinoblastoma protein dephosphorylation by PNUTS provides insights into the PP1 regulatory code. Proc Natl Acad Sci U S A 2014; 111:4097-102. [PMID: 24591642 DOI: 10.1073/pnas.1317395111] [Citation(s) in RCA: 90] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The serine/threonine protein phosphatase 1 (PP1) dephosphorylates hundreds of key biological targets by associating with nearly 200 regulatory proteins to form highly specific holoenzymes. However, how these proteins direct PP1 specificity and the ability to predict how these PP1 interacting proteins bind PP1 from sequence alone is still missing. PP1 nuclear targeting subunit (PNUTS) is a PP1 targeting protein that, with PP1, plays a central role in the nucleus, where it regulates chromatin decondensation, RNA processing, and the phosphorylation state of fundamental cell cycle proteins, including the retinoblastoma protein (Rb), p53, and MDM2. The molecular function of PNUTS in these processes is completely unknown. Here, we show that PNUTS, which is intrinsically disordered in its free form, interacts strongly with PP1 in a highly extended manner. Unexpectedly, PNUTS blocks one of PP1's substrate binding grooves while leaving the active site accessible. This interaction site, which we have named the arginine site, allowed us to define unique PP1 binding motifs, which advances our ability to predict how more than a quarter of the known PP1 regulators bind PP1. Additionally, the structure shows how PNUTS inhibits the PP1-mediated dephosphorylation of critical substrates, especially Rb, by blocking their binding sites on PP1, insights that are providing strategies for selectively enhancing Rb activity.
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21
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Kok BPC, Skene-Arnold TD, Ling J, Benesch MGK, Dewald J, Harris TE, Holmes CFB, Brindley DN. Conserved residues in the N terminus of lipin-1 are required for binding to protein phosphatase-1c, nuclear translocation, and phosphatidate phosphatase activity. J Biol Chem 2014; 289:10876-10886. [PMID: 24558042 DOI: 10.1074/jbc.m114.552612] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Lipin-1 is a phosphatidate phosphatase in glycerolipid biosynthesis and signal transduction. It also serves as a transcriptional co-regulator to control lipid metabolism and adipogenesis. These functions are controlled partly by its subcellular distribution. Hyperphosphorylated lipin-1 remains sequestered in the cytosol, whereas hypophosphorylated lipin-1 translocates to the endoplasmic reticulum and nucleus. The serine/threonine protein phosphatase-1 catalytic subunit (PP-1c) is a major protein dephosphorylation enzyme. Its activity is controlled by interactions with different regulatory proteins, many of which contain conserved RVXF binding motifs. We found that lipin-1 binds to PP-1cγ through a similar HVRF binding motif. This interaction depends on Mg(2+) or Mn(2+) and is competitively inhibited by (R/H)VXF-containing peptides. Mutating the HVRF motif in the highly conserved N terminus of lipin-1 greatly decreases PP-1cγ interaction. Moreover, mutations of other residues in the N terminus of lipin-1 also modulate PP-1cγ binding. PP-1cγ binds poorly to a phosphomimetic mutant of lipin-1 and binds well to the non-phosphorylatable lipin-1 mutant. This indicates that lipin-1 is dephosphorylated before PP-1cγ binds to its HVRF motif. Importantly, mutating the HVRF motif also abrogates the nuclear translocation and phosphatidate phosphatase activity of lipin-1. In conclusion, we provide novel evidence of the importance of the lipin-1 N-terminal domain for its catalytic activity, nuclear localization, and binding to PP-1cγ.
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Affiliation(s)
- Bernard P C Kok
- Signal Transduction Research Group, Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2S2, Canada
| | - Tamara D Skene-Arnold
- Signal Transduction Research Group, Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2S2, Canada
| | - Ji Ling
- Signal Transduction Research Group, Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2S2, Canada
| | - Matthew G K Benesch
- Signal Transduction Research Group, Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2S2, Canada
| | - Jay Dewald
- Signal Transduction Research Group, Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2S2, Canada
| | - Thurl E Harris
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesvillle, Virginia 22908
| | - Charles F B Holmes
- Signal Transduction Research Group, Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2S2, Canada
| | - David N Brindley
- Signal Transduction Research Group, Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2S2, Canada.
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22
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Iosub-Amir A, Friedler A. Protein–protein interactions of ASPP2: an emerging therapeutic target. MEDCHEMCOMM 2014. [DOI: 10.1039/c4md00147h] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
ASPP2 induces apoptosis and is downregulated in many types of cancer, making it a promising target for anti-cancer drugs.
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Affiliation(s)
- Anat Iosub-Amir
- Institute of Chemistry
- The Hebrew University of Jerusalem
- Safra Campus
- Jerusalem 91904, Israel
| | - Assaf Friedler
- Institute of Chemistry
- The Hebrew University of Jerusalem
- Safra Campus
- Jerusalem 91904, Israel
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23
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Uhrig RG, Labandera AM, Moorhead GB. Arabidopsis PPP family of serine/threonine protein phosphatases: many targets but few engines. TRENDS IN PLANT SCIENCE 2013; 18:505-13. [PMID: 23790269 DOI: 10.1016/j.tplants.2013.05.004] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Revised: 05/14/2013] [Accepted: 05/17/2013] [Indexed: 05/20/2023]
Abstract
The major plant serine/threonine protein phosphatases belong to the phosphoprotein phosphatase (PPP) family. Over the past few years the complement of Arabidopsis thaliana PPP family of catalytic subunits has been cataloged and many regulatory subunits identified. Specific roles for PPPs have been characterized, including roles in auxin and brassinosteroid signaling, in phototropism, in regulating the target of rapamycin pathway, and in cell stress responses. In this review, we provide a framework for understanding the PPP family by exploring the fundamental role of the phosphatase regulatory subunits that drive catalytic engine specificity. Although there are fewer plant protein phosphatases compared with their protein kinase partners, their function is now recognized to be as dynamic and as regulated as that of protein kinases.
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Affiliation(s)
- R Glen Uhrig
- Department of Biological Sciences, University of Calgary, Canada
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24
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Shopik MJ, Li L, Luu HA, Obeidat M, Holmes CFB, Ballermann BJ. Multi-directional function of the protein phosphatase 1 regulatory subunit TIMAP. Biochem Biophys Res Commun 2013; 435:567-73. [PMID: 23685145 DOI: 10.1016/j.bbrc.2013.05.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Accepted: 05/04/2013] [Indexed: 11/19/2022]
Abstract
TIMAP is an endothelial-cell predominant member of the MYPT family of PP1c regulatory subunits. This study explored the TIMAP-PP1c interaction and substrate specificity in vitro. TIMAP associated with all three PP1c isoforms, but endogenous endothelial cell TIMAP preferentially co-immunoprecipitated with PP1cβ. Structural modeling of the TIMAP/PP1c complex predicts that the PP1c C-terminus is buried in the TIMAP ankyrin cluster, and that the PP1c active site remains accessible. Consistent with this model, C-terminal PP1c phosphorylation by cdk2-cyclinA was masked by TIMAP, and PP1c bound TIMAP when the active site was occupied by the inhibitor microcystin. TIMAP inhibited PP1c activity toward phosphorylase a in a concentration-dependent manner, with half-maximal inhibition in the 0.4-1.2 nM range, an effect modulated by the length, and by Ser333/Ser337 phosphomimic mutations of the TIMAP C-terminus. TIMAP-bound PP1cβ effectively dephosphorylated MLC2 and TIMAP itself. By contrast, TIMAP inhibited the PP1cβ activity toward the putative substrate LAMR1, and instead masked LAMR1 PKA- and PKC-phosphorylation sites. This is direct evidence that MLC2 is a TIMAP/PP1c substrate. The data also indicate that TIMAP can modify protein phosphorylation independent of its function as a PP1c regulatory subunit, namely by masking phosphorylation sites of binding partners like PP1c and LAMR1.
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Affiliation(s)
- Micheal J Shopik
- Department of Biochemistry, University of Alberta, Edmonton, AB, Canada
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MicroRNA-124 regulates the proliferation of colorectal cancer cells by targeting iASPP. BIOMED RESEARCH INTERNATIONAL 2013; 2013:867537. [PMID: 23691514 PMCID: PMC3652105 DOI: 10.1155/2013/867537] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Revised: 02/24/2013] [Accepted: 02/27/2013] [Indexed: 01/17/2023]
Abstract
MicroRNAs are a class of small, noncoding RNAs that function as critical regulators of gene expression by targeting mRNAs for translational repression or degradation. In this study, we demonstrate that expression of microRNA-124 (miR-124) is significantly downregulated in colorectal cancer tissues and cell lines, compared to the matched adjacent tissues. We identified and confirmed inhibitor of apoptosis-stimulating protein of p53 (iASPP) as a novel, direct target of miR-124 using target prediction algorithms and luciferase reporter gene assays. Overexpression of miR-124 suppressed iASPP protein expression, upregulated expression of the downstream signaling molecule nuclear factor-kappa B (NF- κ B), and attenuated cell viability, proliferation, and colony formation in SW480 and HT-29 colorectal cancer cells in vitro. Forced overexpression of iASPP partly rescued the inhibitory effect of miR-124 on SW480 and HT29 cell proliferation. Taken together, these findings shed light on the role and mechanism of action of miR-124, indicate that the miR-124/iASPP axis can regulate the proliferation of colorectal cancer cells, and suggest that miR-124 may serve as a potential therapeutic target for colorectal cancer.
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