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Boens S, Verbinnen I, Verhulst S, Szekér K, Ferreira M, Gevaert T, Baes M, Roskams T, van Grunsven LA, Van Eynde A, Bollen M. Brief Report: The Deletion of the Phosphatase Regulator NIPP1 Causes Progenitor Cell Expansion in the Adult Liver. Stem Cells 2016; 34:2256-62. [PMID: 27068806 DOI: 10.1002/stem.2375] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Revised: 02/17/2016] [Accepted: 03/14/2016] [Indexed: 01/10/2023]
Abstract
The Ppp1r8 gene encodes NIPP1, a nuclear interactor of protein phosphatase PP1. The deletion of NIPP1 is embryonic lethal at the gastrulation stage, which has hampered its functional characterization in adult tissues. Here, we describe the effects of a conditional deletion of NIPP1 in mouse liver epithelial cells. Ppp1r8(-/-) livers developed a ductular reaction, that is, bile-duct hyperplasia with associated fibrosis. The increased proliferation of biliary epithelial cells was at least partially due to an expansion of the progenitor cell compartment that was independent of liver injury. Gene-expression analysis confirmed an upregulation of progenitor cell markers in the liver knockout livers but showed no effect on the expression of liver-injury associated regulators of cholangiocyte differentiation markers. Consistent with an inhibitory effect of NIPP1 on progenitor cell proliferation, Ppp1r8(-/-) livers displayed an increased sensitivity to diet-supplemented 3,5-diethoxycarbonyl-1,4-dihydrocollidine, which also causes bile-duct hyperplasia through progenitor cell expansion. In contrast, the liver knockouts responded normally to injuries (partial hepatectomy, single CCl4 administration) that are restored through proliferation of differentiated parenchymal cells. Our data indicate that NIPP1 does not regulate the proliferation of hepatocytes but is a suppressor of biliary epithelial cell proliferation, including progenitor cells, in the adult liver. Stem Cells 2016;34:2256-2262.
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Affiliation(s)
- Shannah Boens
- Department of Cellular and Molecular Medicine, Laboratory of Biosignaling & Therapeutics, KU Leuven, Belgium
| | - Iris Verbinnen
- Department of Cellular and Molecular Medicine, Laboratory of Biosignaling & Therapeutics, KU Leuven, Belgium
| | - Stefaan Verhulst
- Liver Cell Biology Lab, Vrije Universiteit Brussel, Brussel, Belgium
| | - Kathelijne Szekér
- Department of Cellular and Molecular Medicine, Laboratory of Biosignaling & Therapeutics, KU Leuven, Belgium
| | - Monica Ferreira
- Department of Cellular and Molecular Medicine, Laboratory of Biosignaling & Therapeutics, KU Leuven, Belgium
| | - Thomas Gevaert
- Department of Development and Regeneration, Organ Systems, KU Leuven, Belgium
| | - Myriam Baes
- Department of Pharmaceutical & Pharmacological Sciences, Laboratory for Cell Metabolism, KU Leuven, Belgium
| | - Tania Roskams
- Department of Imaging & Pathology, Laboratory of Translational Cell & Tissue Research, KU Leuven, Belgium
| | | | - Aleyde Van Eynde
- Department of Cellular and Molecular Medicine, Laboratory of Biosignaling & Therapeutics, KU Leuven, Belgium
| | - Mathieu Bollen
- Department of Cellular and Molecular Medicine, Laboratory of Biosignaling & Therapeutics, KU Leuven, Belgium
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Winkler C, De Munter S, Van Dessel N, Lesage B, Heroes E, Boens S, Beullens M, Van Eynde A, Bollen M. The selective inhibition of protein phosphatase-1 results in mitotic catastrophe and impaired tumor growth. J Cell Sci 2015; 128:4526-37. [PMID: 26542020 DOI: 10.1242/jcs.175588] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 10/26/2015] [Indexed: 01/07/2023] Open
Abstract
The serine/threonine protein phosphatase-1 (PP1) complex is a key regulator of the cell cycle. However, the redundancy of PP1 isoforms and the lack of specific inhibitors have hampered studies on the global role of PP1 in cell cycle progression in vertebrates. Here, we show that the overexpression of nuclear inhibitor of PP1 (NIPP1; also known as PPP1R8) in HeLa cells culminated in a prometaphase arrest, associated with severe spindle-formation and chromosome-congression defects. In addition, the spindle assembly checkpoint was activated and checkpoint silencing was hampered. Eventually, most cells either died by apoptosis or formed binucleated cells. The NIPP1-induced mitotic arrest could be explained by the inhibition of PP1 that was titrated away from other mitotic PP1 interactors. Consistent with this notion, the mitotic-arrest phenotype could be rescued by the overexpression of PP1 or the inhibition of the Aurora B kinase, which acts antagonistically to PP1. Finally, we demonstrate that the overexpression of NIPP1 also hampered colony formation and tumor growth in xenograft assays in a PP1-dependent manner. Our data show that the selective inhibition of PP1 can be used to induce cancer cell death through mitotic catastrophe.
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Affiliation(s)
- Claudia Winkler
- Laboratory of Biosignaling & Therapeutics, KU Leuven Department of Cellular and Molecular Medicine, University of Leuven, Leuven B-3000, Belgium
| | - Sofie De Munter
- Laboratory of Biosignaling & Therapeutics, KU Leuven Department of Cellular and Molecular Medicine, University of Leuven, Leuven B-3000, Belgium
| | - Nele Van Dessel
- Laboratory of Biosignaling & Therapeutics, KU Leuven Department of Cellular and Molecular Medicine, University of Leuven, Leuven B-3000, Belgium
| | - Bart Lesage
- Laboratory of Biosignaling & Therapeutics, KU Leuven Department of Cellular and Molecular Medicine, University of Leuven, Leuven B-3000, Belgium
| | - Ewald Heroes
- Laboratory of Biosignaling & Therapeutics, KU Leuven Department of Cellular and Molecular Medicine, University of Leuven, Leuven B-3000, Belgium
| | - Shannah Boens
- Laboratory of Biosignaling & Therapeutics, KU Leuven Department of Cellular and Molecular Medicine, University of Leuven, Leuven B-3000, Belgium
| | - Monique Beullens
- Laboratory of Biosignaling & Therapeutics, KU Leuven Department of Cellular and Molecular Medicine, University of Leuven, Leuven B-3000, Belgium
| | - Aleyde Van Eynde
- Laboratory of Biosignaling & Therapeutics, KU Leuven Department of Cellular and Molecular Medicine, University of Leuven, Leuven B-3000, Belgium
| | - Mathieu Bollen
- Laboratory of Biosignaling & Therapeutics, KU Leuven Department of Cellular and Molecular Medicine, University of Leuven, Leuven B-3000, Belgium
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Verheyen T, Görnemann J, Verbinnen I, Boens S, Beullens M, Van Eynde A, Bollen M. Genome-wide promoter binding profiling of protein phosphatase-1 and its major nuclear targeting subunits. Nucleic Acids Res 2015; 43:5771-84. [PMID: 25990731 PMCID: PMC4499128 DOI: 10.1093/nar/gkv500] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Accepted: 05/05/2015] [Indexed: 12/11/2022] Open
Abstract
Protein phosphatase-1 (PP1) is a key regulator of transcription and is targeted to promoter regions via associated proteins. However, the chromatin binding sites of PP1 have never been studied in a systematic and genome-wide manner. Methylation-based DamID profiling in HeLa cells has enabled us to map hundreds of promoter binding sites of PP1 and three of its major nuclear interactors, i.e. RepoMan, NIPP1 and PNUTS. Our data reveal that the α, β and γ isoforms of PP1 largely bind to distinct subsets of promoters and can also be differentiated by their promoter binding pattern. PP1β emerged as the major promoter-associated isoform and shows an overlapping binding profile with PNUTS at dozens of active promoters. Surprisingly, most promoter binding sites of PP1 are not shared with RepoMan, NIPP1 or PNUTS, hinting at the existence of additional, largely unidentified chromatin-targeting subunits. We also found that PP1 is not required for the global chromatin targeting of RepoMan, NIPP1 and PNUTS, but alters the promoter binding specificity of NIPP1. Our data disclose an unexpected specificity and complexity in the promoter binding of PP1 isoforms and their chromatin-targeting subunits.
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Affiliation(s)
- Toon Verheyen
- Laboratory of Biosignaling & Therapeutics, KU Leuven Department of Cellular and Molecular Medicine, University of Leuven, B-3000 Leuven, Belgium
| | - Janina Görnemann
- Laboratory of Biosignaling & Therapeutics, KU Leuven Department of Cellular and Molecular Medicine, University of Leuven, B-3000 Leuven, Belgium
| | - Iris Verbinnen
- Laboratory of Biosignaling & Therapeutics, KU Leuven Department of Cellular and Molecular Medicine, University of Leuven, B-3000 Leuven, Belgium
| | - Shannah Boens
- Laboratory of Biosignaling & Therapeutics, KU Leuven Department of Cellular and Molecular Medicine, University of Leuven, B-3000 Leuven, Belgium
| | - Monique Beullens
- Laboratory of Biosignaling & Therapeutics, KU Leuven Department of Cellular and Molecular Medicine, University of Leuven, B-3000 Leuven, Belgium
| | - Aleyde Van Eynde
- Laboratory of Biosignaling & Therapeutics, KU Leuven Department of Cellular and Molecular Medicine, University of Leuven, B-3000 Leuven, Belgium
| | - Mathieu Bollen
- Laboratory of Biosignaling & Therapeutics, KU Leuven Department of Cellular and Molecular Medicine, University of Leuven, B-3000 Leuven, Belgium
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Abstract
Protein phosphatase-1 (PP1) is an essential enzyme for every eukaryotic cell and catalyzes more than half of all protein dephosphorylations at serine and threonine residues. The free catalytic subunit of PP1 shows little substrate selectivity but is tightly regulated in vivo by a large variety of structurally unrelated PP1-interacting proteins (PIPs). PIPs form highly specific dimeric or trimeric PP1 holoenzymes by acting as substrates, inhibitors, and/or substrate-specifiers. The surface of PP1 contains many binding sites for short PP1-docking motifs that are combined by PIPs to create a PP1-binding code that is universal, specific, degenerate, nonexclusive, and dynamic. These properties of the PP1-binding code can be used for the rational design of small molecules that disrupt subsets of PP1 holoenzymes and have a therapeutic potential.
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Affiliation(s)
- Shannah Boens
- Laboratory of Biosignaling & Therapeutics, Department of Cellular and Molecular Medicine, University of Leuven, Leuven, Belgium
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Cools T, Iantcheva A, Weimer AK, Boens S, Takahashi N, Maes S, Van den Daele H, Van Isterdael G, Schnittger A, De Veylder L. The Arabidopsis thaliana checkpoint kinase WEE1 protects against premature vascular differentiation during replication stress. Plant Cell 2011; 23:1435-48. [PMID: 21498679 PMCID: PMC3101530 DOI: 10.1105/tpc.110.082768] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2010] [Revised: 03/22/2011] [Accepted: 03/30/2011] [Indexed: 05/17/2023]
Abstract
A sessile lifestyle forces plants to respond promptly to factors that affect their genomic integrity. Therefore, plants have developed checkpoint mechanisms to arrest cell cycle progression upon the occurrence of DNA stress, allowing the DNA to be repaired before onset of division. Previously, the WEE1 kinase had been demonstrated to be essential for delaying progression through the cell cycle in the presence of replication-inhibitory drugs, such as hydroxyurea. To understand the severe growth arrest of WEE1-deficient plants treated with hydroxyurea, a transcriptomics analysis was performed, indicating prolonged S-phase duration. A role for WEE1 during S phase was substantiated by its specific accumulation in replicating nuclei that suffered from DNA stress. Besides an extended replication phase, WEE1 knockout plants accumulated dead cells that were associated with premature vascular differentiation. Correspondingly, plants without functional WEE1 ectopically expressed the vascular differentiation marker VND7, and their vascular development was aberrant. We conclude that the growth arrest of WEE1-deficient plants is due to an extended cell cycle duration in combination with a premature onset of vascular cell differentiation. The latter implies that the plant WEE1 kinase acquired an indirect developmental function that is important for meristem maintenance upon replication stress.
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Affiliation(s)
- Toon Cools
- Department of Plant Systems Biology, VIB, 9052 Ghent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, B-9052 Ghent, Belgium
| | - Anelia Iantcheva
- Department of Plant Systems Biology, VIB, 9052 Ghent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, B-9052 Ghent, Belgium
| | - Annika K. Weimer
- Department of Molecular Mechanisms of Phenotypic Plasticity, Institut de Biologie Moléculaire des Plantes–Centre National de Recherche Scientifique, Unité Propre de Recherche 2357, Université de Strasbourg, 67084 Strasbourg Cedex, France
| | - Shannah Boens
- Department of Plant Systems Biology, VIB, 9052 Ghent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, B-9052 Ghent, Belgium
| | - Naoki Takahashi
- Department of Plant Systems Biology, VIB, 9052 Ghent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, B-9052 Ghent, Belgium
| | - Sara Maes
- Department of Plant Systems Biology, VIB, 9052 Ghent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, B-9052 Ghent, Belgium
| | - Hilde Van den Daele
- Department of Plant Systems Biology, VIB, 9052 Ghent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, B-9052 Ghent, Belgium
| | - Gert Van Isterdael
- Department of Plant Systems Biology, VIB, 9052 Ghent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, B-9052 Ghent, Belgium
| | - Arp Schnittger
- Department of Molecular Mechanisms of Phenotypic Plasticity, Institut de Biologie Moléculaire des Plantes–Centre National de Recherche Scientifique, Unité Propre de Recherche 2357, Université de Strasbourg, 67084 Strasbourg Cedex, France
| | - Lieven De Veylder
- Department of Plant Systems Biology, VIB, 9052 Ghent, Belgium
- Department of Plant Biotechnology and Genetics, Ghent University, B-9052 Ghent, Belgium
- Address correspondence to
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