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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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Nadel G, Yao Z, Hacohen-Lev-Ran A, Wainstein E, Maik-Rachline G, Ziv T, Naor Z, Admon A, Seger R. Phosphorylation of PP2Ac by PKC is a key regulatory step in the PP2A-switch-dependent AKT dephosphorylation that leads to apoptosis. Cell Commun Signal 2024; 22:154. [PMID: 38419089 PMCID: PMC10900696 DOI: 10.1186/s12964-024-01536-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Accepted: 02/17/2024] [Indexed: 03/02/2024] Open
Abstract
BACKGROUND Although GqPCR activation often leads to cell survival by activating the PI3K/AKT pathway, it was previously shown that in several cell types AKT activity is reduced and leads to JNK activation and apoptosis. The mechanism of AKT inactivation in these cells involves an IGBP1-coupled PP2Ac switch that induces the dephosphorylation and inactivation of both PI3K and AKT. However, the machinery involved in the initiation of PP2A switch is not known. METHODS We used phospho-mass spectrometry to identify the phosphorylation site of PP2Ac, and raised specific antibodies to follow the regulation of this phosphorylation. Other phosphorylations were monitored by commercial antibodies. In addition, we used coimmunoprecipitation and proximity ligation assays to follow protein-protein interactions. Apoptosis was detected by a TUNEL assay as well as PARP1 cleavage using SDS-PAGE and Western blotting. RESULTS We identified Ser24 as a phosphorylation site in PP2Ac. The phosphorylation is mediated mainly by classical PKCs (PKCα and PKCβ) but not by novel PKCs (PKCδ and PKCε). By replacing the phosphorylated residue with either unphosphorylatable or phosphomimetic residues (S24A and S24E), we found that this phosphorylation event is necessary and sufficient to mediate the PP2A switch, which ultimately induces AKT inactivation, and a robust JNK-dependent apoptosis. CONCLUSION Our results show that the PP2A switch is induced by PKC-mediated phosphorylation of Ser24-PP2Ac and that this phosphorylation leads to apoptosis upon GqPCR induction of various cells. We propose that this mechanism may provide an unexpected way to treat some cancer types or problems in the endocrine machinery.
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Affiliation(s)
- Guy Nadel
- Department of Immunology and Regenerative Biology, the Weizmann Institute of Science, Rehovot, Israel
| | - Zhong Yao
- Department of Immunology and Regenerative Biology, the Weizmann Institute of Science, Rehovot, Israel
| | - Avital Hacohen-Lev-Ran
- Department of Immunology and Regenerative Biology, the Weizmann Institute of Science, Rehovot, Israel
| | - Ehud Wainstein
- Department of Immunology and Regenerative Biology, the Weizmann Institute of Science, Rehovot, Israel
| | - Galia Maik-Rachline
- Department of Immunology and Regenerative Biology, the Weizmann Institute of Science, Rehovot, Israel
| | - Tamar Ziv
- Smoler Proteomic Center, Technion-Israel Institute of Technology, Haifa, Israel
| | - Zvi Naor
- Department of Biochemistry and Molecular Biology, Tel Aviv University, Tel Aviv, Israel
| | - Arie Admon
- Faculty of Biology, Technion-Israel Institute of Technology, Haifa, Israel
| | - Rony Seger
- Department of Immunology and Regenerative Biology, the Weizmann Institute of Science, Rehovot, Israel.
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3
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Ji N, Chen Z, Wang Z, Sun W, Yuan Q, Zhang X, Jia X, Wu J, Jiang J, Song M, Xu T, Liu Y, Ma Q, Sun Z, Bao Y, Zhang M, Huang M. LincR-PPP2R5C Promotes Th2 Cell Differentiation Through PPP2R5C/PP2A by Forming an RNA-DNA Triplex in Allergic Asthma. ALLERGY, ASTHMA & IMMUNOLOGY RESEARCH 2024; 16:71-90. [PMID: 38262392 PMCID: PMC10823138 DOI: 10.4168/aair.2024.16.1.71] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2023] [Revised: 08/13/2023] [Accepted: 08/22/2023] [Indexed: 01/25/2024]
Abstract
PURPOSE The roles and mechanisms of long noncoding RNAs (lncRNAs) in T helper 2 (Th2) differentiation from allergic asthma are poorly understood. We aimed to explore a novel lncRNA, LincR-protein phosphatase 2 regulatory subunit B' gamma (PPP2R5C), in Th2 differentiation in a mouse model of asthma. METHODS LincR-PPP2R5C from RNA-seq data of CD4+ T cells of asthma-like mice were validated and confirmed by quantitative reverse transcription polymerase chain reaction, northern blotting, nuclear and cytoplasmic separation, and fluorescence in situ hybridization (FISH). Lentiviruses encoding LincR-PPP2R5C or shRNA were used to overexpress or silence LincR-PPP2R5C in CD4+ T cells. The interactions between LincR-PPP2R5C and PPP2R5C were explored with western blotting, chromatin isolation by RNA purification assay, and fluorescence resonance energy transfer. An ovalbumin-induced acute asthma model in knockout (KO) mice (LincR-PPP2R5C KO, CD4 conditional LincR-PPP2R5C KO) was established to explore the roles of LincR-PPP2R5C in Th2 differentiation. RESULTS LncR-PPP2R5C was significantly higher in CD4+ T cells from asthmatic mice ex vivo and Th2 cells in vitro. The lentivirus encoding LincR-PPP2R5C suppressed Th1 differentiation; in contrast, the short hairpin RNA (shRNA) lentivirus decreased LincR-PPP2R5C and Th2 differentiation. Mechanistically, LincR-PPP2R5C deficiency suppressed the phosphatase activity of the protein phosphatase 2A (PP2A) holocomplex, resulting in a decline in Th2 differentiation. The formation of an RNA-DNA triplex between LincR-PPP2R5C and the PPP2R5C promoter enhanced PPP2R5C expression and activated PP2A. LincR-PPP2R5C KO and CD4 conditional KO decreased Th2 differentiation, airway hyperresponsiveness and inflammatory responses. CONCLUSIONS LincR-PPP2R5C regulated PPP2R5C expression and PP2A activity by forming an RNA-DNA triplex with the PPP2R5C promoter, leading to Th2 polarization in a mouse model of acute asthma. Our data presented the first definitive evidence of lncRNAs in the regulation of Th2 cells in asthma.
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Affiliation(s)
- Ningfei Ji
- Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Zhongqi Chen
- Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Zhengxia Wang
- Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Wei Sun
- Department of Respiratory and Critical Care Medicine, Xishan People's Hospital of Wuxi City, Wuxi Branch of Zhongda Hospital Affiliate to Southeast University, Wuxi, China
| | - Qi Yuan
- Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Xijie Zhang
- Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Xinyu Jia
- Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Jingjing Wu
- Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Jingxian Jiang
- Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Meijuan Song
- Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Tingting Xu
- Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Yanan Liu
- Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Qiyun Ma
- Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Zhixiao Sun
- Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Yanmin Bao
- Department of Respiratory Medicine, Shenzhen Children's Hospital, Shenzhen, China
| | - Mingshun Zhang
- Jiangsu Province Engineering Research Center of Antibody Drugs, NHC Key Laboratory of Antibody Technique, Department of Immunology, Nanjing Medical University, Nanjing, China.
| | - Mao Huang
- Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
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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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Yu H, Zaveri S, Sattar Z, Schaible M, Perez Gandara B, Uddin A, McGarvey LR, Ohlmeyer M, Geraghty P. Protein Phosphatase 2A as a Therapeutic Target in Pulmonary Diseases. MEDICINA (KAUNAS, LITHUANIA) 2023; 59:1552. [PMID: 37763671 PMCID: PMC10535831 DOI: 10.3390/medicina59091552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Revised: 08/22/2023] [Accepted: 08/24/2023] [Indexed: 09/29/2023]
Abstract
New disease targets and medicinal chemistry approaches are urgently needed to develop novel therapeutic strategies for treating pulmonary diseases. Emerging evidence suggests that reduced activity of protein phosphatase 2A (PP2A), a complex heterotrimeric enzyme that regulates dephosphorylation of serine and threonine residues from many proteins, is observed in multiple pulmonary diseases, including lung cancer, smoke-induced chronic obstructive pulmonary disease, alpha-1 antitrypsin deficiency, asthma, and idiopathic pulmonary fibrosis. Loss of PP2A responses is linked to many mechanisms associated with disease progressions, such as senescence, proliferation, inflammation, corticosteroid resistance, enhanced protease responses, and mRNA stability. Therefore, chemical restoration of PP2A may represent a novel treatment for these diseases. This review outlines the potential impact of reduced PP2A activity in pulmonary diseases, endogenous and exogenous inhibitors of PP2A, details the possible PP2A-dependent mechanisms observed in these conditions, and outlines potential therapeutic strategies for treatment. Substantial medicinal chemistry efforts are underway to develop therapeutics targeting PP2A activity. The development of specific activators of PP2A that selectively target PP2A holoenzymes could improve our understanding of the function of PP2A in pulmonary diseases. This may lead to the development of therapeutics for restoring normal PP2A responses within the lung.
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Affiliation(s)
- Howard Yu
- Department of Medicine, State University of New York Downstate Health Sciences University, 450 Clarkson Avenue, Brooklyn, NY 11203, USA; (H.Y.); (S.Z.); (Z.S.); (M.S.); (B.P.G.); (A.U.); (L.R.M.)
| | - Sahil Zaveri
- Department of Medicine, State University of New York Downstate Health Sciences University, 450 Clarkson Avenue, Brooklyn, NY 11203, USA; (H.Y.); (S.Z.); (Z.S.); (M.S.); (B.P.G.); (A.U.); (L.R.M.)
| | - Zeeshan Sattar
- Department of Medicine, State University of New York Downstate Health Sciences University, 450 Clarkson Avenue, Brooklyn, NY 11203, USA; (H.Y.); (S.Z.); (Z.S.); (M.S.); (B.P.G.); (A.U.); (L.R.M.)
| | - Michael Schaible
- Department of Medicine, State University of New York Downstate Health Sciences University, 450 Clarkson Avenue, Brooklyn, NY 11203, USA; (H.Y.); (S.Z.); (Z.S.); (M.S.); (B.P.G.); (A.U.); (L.R.M.)
| | - Brais Perez Gandara
- Department of Medicine, State University of New York Downstate Health Sciences University, 450 Clarkson Avenue, Brooklyn, NY 11203, USA; (H.Y.); (S.Z.); (Z.S.); (M.S.); (B.P.G.); (A.U.); (L.R.M.)
| | - Anwar Uddin
- Department of Medicine, State University of New York Downstate Health Sciences University, 450 Clarkson Avenue, Brooklyn, NY 11203, USA; (H.Y.); (S.Z.); (Z.S.); (M.S.); (B.P.G.); (A.U.); (L.R.M.)
| | - Lucas R. McGarvey
- Department of Medicine, State University of New York Downstate Health Sciences University, 450 Clarkson Avenue, Brooklyn, NY 11203, USA; (H.Y.); (S.Z.); (Z.S.); (M.S.); (B.P.G.); (A.U.); (L.R.M.)
| | | | - Patrick Geraghty
- Department of Medicine, State University of New York Downstate Health Sciences University, 450 Clarkson Avenue, Brooklyn, NY 11203, USA; (H.Y.); (S.Z.); (Z.S.); (M.S.); (B.P.G.); (A.U.); (L.R.M.)
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6
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Guffens L, Derua R, Janssens V. PME-1 sensitizes glioblastoma cells to oxidative stress-induced cell death by attenuating PP2A-B55α-mediated inactivation of MAPKAPK2-RIPK1 signaling. Cell Death Discov 2023; 9:265. [PMID: 37500619 PMCID: PMC10374899 DOI: 10.1038/s41420-023-01572-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 07/13/2023] [Accepted: 07/20/2023] [Indexed: 07/29/2023] Open
Abstract
Glioblastoma (GBM) is the most common primary brain tumor in adults. Current standard therapy is surgery followed by radiotherapy, with concurrent and adjuvant temozolomide chemotherapy. GBM is characterized by almost uniformly fatal outcomes, highlighting the unmet clinical need for more efficient, biomarker-guided treatments. Protein phosphatase methylesterase-1 (PME-1), a regulator of the tumor suppressive phosphatase PP2A, promotes PP2A demethylation and inactivation, and is overexpressed in 44% of GBM, associated with increased tumor grade and cellular proliferation. Here, we aimed to investigate how reactive oxygen species (ROS), a frequent by-product of radiotherapy and temozolomide chemotherapy, regulate PP2A function via its methylesterase PME-1, and how PME-1 overexpression impacts the response of GBM cells to oxidative stress. We found that in two glioblastoma cell lines, U87MG and U251MG, expression of PME-1 is positively correlated with the sensitivity of the cells to H2O2 or t-BHP-induced oxidative stress. Experiments using the irreversible pharmacologic PME-1 inhibitor, AMZ30, and different PME-1 mutants, revealed that the methylesterase function, the PP2A binding capacity, and the nuclear localization of PME-1 are all important for the sensitizing effect of PME-1 expression. Furthermore, we identified increased nuclear localization of the PP2A-B55α subunit, increased binding of PP2A-B55α to PME-1, and increased B55α-bound PP2A-C demethylation upon oxidative stress. Lastly, we uncovered increased stress-induced phosphorylation and activity of MAPKAPK2 and RIPK1 in PME-1 overexpressing U87MG cells, which caused the observed sensitization to t-BHP treatment. Our data reveal a novel role for PME-1 in oxidative stress-induced GBM cell death, regulating nuclear PP2A-B55α activity and MAPKAPK2-RIPK1 signaling. Patients with GBM tumors overexpressing PME-1, although having a worse prognosis due to increased cellular proliferation of the tumor, could actually be more responsive to oxidative stress-inducing therapies.
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Affiliation(s)
- Liesbeth Guffens
- Laboratory of Protein Phosphorylation & Proteomics, Dept. Cellular & Molecular Medicine, KU Leuven, B-3000, Leuven, Belgium
- KU Leuven Cancer Institute (LKI), B-3000, Leuven, Belgium
| | - Rita Derua
- Laboratory of Protein Phosphorylation & Proteomics, Dept. Cellular & Molecular Medicine, KU Leuven, B-3000, Leuven, Belgium
- SyBioMa, KU Leuven, B-3000, Leuven, Belgium
| | - Veerle Janssens
- Laboratory of Protein Phosphorylation & Proteomics, Dept. Cellular & Molecular Medicine, KU Leuven, B-3000, Leuven, Belgium.
- KU Leuven Cancer Institute (LKI), B-3000, Leuven, Belgium.
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7
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Saini LK, Bheri M, Pandey GK. Protein phosphatases and their targets: Comprehending the interactions in plant signaling pathways. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2023; 134:307-370. [PMID: 36858740 DOI: 10.1016/bs.apcsb.2022.11.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
Protein phosphorylation is a vital reversible post-translational modification. This process is established by two classes of enzymes: protein kinases and protein phosphatases. Protein kinases phosphorylate proteins while protein phosphatases dephosphorylate phosphorylated proteins, thus, functioning as 'critical regulators' in signaling pathways. The eukaryotic protein phosphatases are classified as phosphoprotein phosphatases (PPP), metallo-dependent protein phosphatases (PPM), protein tyrosine (Tyr) phosphatases (PTP), and aspartate (Asp)-dependent phosphatases. The PPP and PPM families are serine (Ser)/threonine (Thr) specific phosphatases (STPs) that dephosphorylate Ser and Thr residues. The PTP family dephosphorylates Tyr residues while dual-specificity phosphatases (DsPTPs/DSPs) dephosphorylate Ser, Thr, and Tyr residues. The composition of these enzymes as well as their substrate specificity are important determinants of their functional significance in a number of cellular processes and stress responses. Their role in animal systems is well-understood and characterized. The functional characterization of protein phosphatases has been extensively covered in plants, although the comprehension of their mechanistic basis is an ongoing pursuit. The nature of their interactions with other key players in the signaling process is vital to our understanding. The substrates or targets determine their potential as well as magnitude of the impact they have on signaling pathways. In this article, we exclusively overview the various substrates of protein phosphatases in plant signaling pathways, which are a critical determinant of the outcome of various developmental and stress stimuli.
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Affiliation(s)
- Lokesh K Saini
- Department of Plant Molecular Biology, University of Delhi South Campus, Dhaula Kuan, New Delhi, India
| | - Malathi Bheri
- Department of Plant Molecular Biology, University of Delhi South Campus, Dhaula Kuan, New Delhi, India
| | - Girdhar K Pandey
- Department of Plant Molecular Biology, University of Delhi South Campus, Dhaula Kuan, New Delhi, India.
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8
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Creighton MT, Nemie-Feyissa D, Zaman N, Johansen SS, Dysjaland H, Heidari B, Lillo C. Loss of LEUCINE CARBOXYL METHYLTRANSFERASE 1 interferes with metal homeostasis in Arabidopsis and enhances susceptibility to environmental stresses. JOURNAL OF PLANT PHYSIOLOGY 2022; 279:153843. [PMID: 36265226 DOI: 10.1016/j.jplph.2022.153843] [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: 07/17/2022] [Revised: 09/30/2022] [Accepted: 10/10/2022] [Indexed: 06/16/2023]
Abstract
The biochemical function of LEUCINE CARBOXYL METHYLTRANSFERASE 1 (LCMT1) is to transfer a methyl group from the methyl donor S-adenosylmethionine (SAM) to the catalytic subunits of PROTEIN PHOSPHATASE 2A (PP2Ac), PP4 and PP6. This post-translational modification by LCMT1 is found throughout eukaryotes from yeast to animals and plants, indicating that its function is essential. However, Arabidopsis with knocked out LCMT1 still grows and develops almost normally, at least under optimal growth conditions. We therefore proposed that the presence of LCMT1 would be important under non-optimal growth conditions and favoured plant survival during evolution. To shed light on the physiological functions of plant LCMT1, phenotypes of the lcmt1 mutant and wild type Arabidopsis were compared under various conditions including exposure to heavy metals, variable chelator concentrations, and increased temperature. The lcmt1 mutant was found to be more susceptible to these environmental changes than wild type and resulted in poor growth of seedlings and rosette stage plants. Element analysis of rosette stage plants mainly showed a difference between the lcmt1 mutant and wild type regarding concentrations of sodium and boron, two-fold up or halved, respectively. In both lcmt1 and wild type, lack of EDTA in the growth medium resulted in enhanced concentration of copper, manganese, zinc and sulphur, and especially lcmt1 growth was hampered by these conditions. The altered phenotype in response to stress, the element and mRNA transcript analysis substantiate that LCMT1 has an important role in metal homeostasis and show that functional LCMT1 is necessary to prevent damages from heat, heavy metals or lack of chelator.
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Affiliation(s)
- Maria T Creighton
- IKBM, Department of Chemistry, Bioscience and Environmental Engineering, University of Stavanger, 4036, Stavanger, Norway
| | - Dugassa Nemie-Feyissa
- IKBM, Department of Chemistry, Bioscience and Environmental Engineering, University of Stavanger, 4036, Stavanger, Norway
| | - Nabeela Zaman
- IKBM, Department of Chemistry, Bioscience and Environmental Engineering, University of Stavanger, 4036, Stavanger, Norway
| | - Sverre S Johansen
- IKBM, Department of Chemistry, Bioscience and Environmental Engineering, University of Stavanger, 4036, Stavanger, Norway
| | - Hege Dysjaland
- IKBM, Department of Chemistry, Bioscience and Environmental Engineering, University of Stavanger, 4036, Stavanger, Norway
| | - Behzad Heidari
- IKBM, Department of Chemistry, Bioscience and Environmental Engineering, University of Stavanger, 4036, Stavanger, Norway
| | - Cathrine Lillo
- IKBM, Department of Chemistry, Bioscience and Environmental Engineering, University of Stavanger, 4036, Stavanger, Norway.
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9
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Haanen TJ, O'Connor CM, Narla G. Biased holoenzyme assembly of protein phosphatase 2A (PP2A): From cancer to small molecules. J Biol Chem 2022; 298:102656. [PMID: 36328247 PMCID: PMC9707111 DOI: 10.1016/j.jbc.2022.102656] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Revised: 10/25/2022] [Accepted: 10/27/2022] [Indexed: 11/06/2022] Open
Abstract
Protein phosphatase 2A (PP2A) is a family of serine threonine phosphatases responsible for regulating protein phosphorylation, thus opposing the activity of cellular kinases. PP2A is composed of a catalytic subunit (PP2A Cα/β) and scaffolding subunit (PP2A Aα/β) and various substrate-directing B regulatory subunits. PP2A biogenesis is regulated at multiple levels. For example, the sequestration of the free catalytic subunit during the process of biogenesis avoids promiscuous phosphatase activity. Posttranslational modifications of PP2A C direct PP2A heterotrimeric formation. Additionally, PP2A functions as a haploinsufficient tumor suppressor, where attenuated PP2A enzymatic activity creates a permissive environment for oncogenic transformation. Recent work studying PP2A in cancer showed that its role in tumorigenesis is more nuanced, with some holoenzymes being tumor suppressive, while others are required for oncogenic transformation. In cancer biology, PP2A function is modulated through various mechanisms including the displacement of specific B regulatory subunits by DNA tumor viral antigens, by recurrent mutations, and through loss of carboxymethyl-sensitive heterotrimeric complexes. In aggregate, these alterations bias PP2A activity away from its tumor suppressive functions and toward oncogenic ones. From a therapeutic perspective, molecular glues and disruptors present opportunities for both the selective stabilization of tumor-suppressive holoenzymes and disruption of holoenzymes that are pro-oncogenic. Collectively, these approaches represent an attractive cancer therapy for a wide range of tumor types. This review will discuss the mechanisms by which PP2A holoenzyme formation is dysregulated in cancer and the current therapies that are aimed at biasing heterotrimer formation of PP2A for the treatment of cancer.
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10
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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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11
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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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12
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Li Y, Balakrishnan VK, Rowse M, Wu CG, Bravos AP, Yadav VK, Ivarsson YI, Strack S, Novikova IV, Xing Y. Coupling to short linear motifs creates versatile PME-1 activities in PP2A holoenzyme demethylation and inhibition. eLife 2022; 11:79736. [PMID: 35924897 PMCID: PMC9398451 DOI: 10.7554/elife.79736] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 08/03/2022] [Indexed: 11/30/2022] Open
Abstract
Protein phosphatase 2A (PP2A) holoenzymes target broad substrates by recognizing short motifs via regulatory subunits. PP2A methylesterase 1 (PME-1) is a cancer-promoting enzyme and undergoes methylesterase activation upon binding to the PP2A core enzyme. Here, we showed that PME-1 readily demethylates different families of PP2A holoenzymes and blocks substrate recognition in vitro. The high-resolution cryoelectron microscopy structure of a PP2A-B56 holoenzyme–PME-1 complex reveals that PME-1 disordered regions, including a substrate-mimicking motif, tether to the B56 regulatory subunit at remote sites. They occupy the holoenzyme substrate-binding groove and allow large structural shifts in both holoenzyme and PME-1 to enable multipartite contacts at structured cores to activate the methylesterase. B56 interface mutations selectively block PME-1 activity toward PP2A-B56 holoenzymes and affect the methylation of a fraction of total cellular PP2A. The B56 interface mutations allow us to uncover B56-specific PME-1 functions in p53 signaling. Our studies reveal multiple mechanisms of PME-1 in suppressing holoenzyme functions and versatile PME-1 activities derived from coupling substrate-mimicking motifs to dynamic structured cores.
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Affiliation(s)
- Yitong Li
- Department of Oncology, University of Wisconsin-Madison, Madison, United States
| | | | - Michael Rowse
- Indiana University - Purdue University Columbus, Columbus, United States
| | - Cheng-Guo Wu
- Department of Oncology, University of Wisconsin-Madison, Madison, United States
| | | | - Vikash K Yadav
- 5Department of Chemistry, Uppsala University, Uppsala, Sweden
| | - YIva Ivarsson
- 5Department of Chemistry, Uppsala University, Uppsala, Sweden
| | - Stefan Strack
- Department of Neuroscience and Pharmacology, University of Iowa, Iowa City, United States
| | - Irina V Novikova
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, United States
| | - Yongna Xing
- Department of Oncology, University of Wisconsin-Madison, Madison, United States
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13
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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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14
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Sergienko NM, Donner DG, Delbridge LMD, McMullen JR, Weeks KL. Protein phosphatase 2A in the healthy and failing heart: New insights and therapeutic opportunities. Cell Signal 2021; 91:110213. [PMID: 34902541 DOI: 10.1016/j.cellsig.2021.110213] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 12/02/2021] [Accepted: 12/07/2021] [Indexed: 02/06/2023]
Abstract
Protein phosphatases have emerged as critical regulators of phosphoprotein homeostasis in settings of health and disease. Protein phosphatase 2A (PP2A) encompasses a large subfamily of enzymes that remove phosphate groups from serine/threonine residues within phosphoproteins. The heterogeneity in PP2A structure, which arises from the grouping of different catalytic, scaffolding and regulatory subunit isoforms, creates distinct populations of catalytically active enzymes (i.e. holoenzymes) that localise to different parts of the cell. This structural complexity, combined with other regulatory mechanisms, such as interaction of PP2A heterotrimers with accessory proteins and post-translational modification of the catalytic and/or regulatory subunits, enables PP2A holoenzymes to target phosphoprotein substrates in a highly specific manner. In this review, we summarise the roles of PP2A in cardiac physiology and disease. PP2A modulates numerous processes that are vital for heart function including calcium handling, contractility, β-adrenergic signalling, metabolism and transcription. Dysregulation of PP2A has been observed in human cardiac disease settings, including heart failure and atrial fibrillation. Efforts are underway, particularly in the cancer field, to develop therapeutics targeting PP2A activity. The development of small molecule activators of PP2A (SMAPs) and other compounds that selectively target specific PP2A holoenzymes (e.g. PP2A/B56α and PP2A/B56ε) will improve understanding of the function of different PP2A species in the heart, and may lead to the development of therapeutics for normalising aberrant protein phosphorylation in settings of cardiac remodelling and dysfunction.
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Affiliation(s)
- Nicola M Sergienko
- Baker Heart and Diabetes Institute, Melbourne VIC 3004, Australia; Central Clinical School, Monash University, Clayton VIC 3800, Australia
| | - Daniel G Donner
- Baker Heart and Diabetes Institute, Melbourne VIC 3004, Australia; Baker Department of Cardiometabolic Health, The University of Melbourne, Parkville VIC 3010, Australia
| | - Lea M D Delbridge
- Department of Anatomy and Physiology, The University of Melbourne, Parkville VIC 3010, Australia
| | - Julie R McMullen
- Baker Heart and Diabetes Institute, Melbourne VIC 3004, Australia; Baker Department of Cardiometabolic Health, The University of Melbourne, Parkville VIC 3010, Australia; Department of Physiology and Department of Medicine Alfred Hospital, Monash University, Clayton VIC 3800, Australia; Department of Physiology, Anatomy and Microbiology, La Trobe University, Bundoora VIC 3086, Australia; Department of Diabetes, Central Clinical School, Monash University, Clayton VIC 3800, Australia.
| | - Kate L Weeks
- Baker Heart and Diabetes Institute, Melbourne VIC 3004, Australia; Department of Anatomy and Physiology, The University of Melbourne, Parkville VIC 3010, Australia; Baker Department of Cardiometabolic Health, The University of Melbourne, Parkville VIC 3010, Australia; Department of Diabetes, Central Clinical School, Monash University, Clayton VIC 3800, Australia.
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15
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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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16
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Mazhar S, Leonard D, Sosa A, Schlatzer D, Thomas D, Narla G. Challenges and Reinterpretation of Antibody-Based Research on Phosphorylation of Tyr 307 on PP2Ac. Cell Rep 2021; 30:3164-3170.e3. [PMID: 32130915 DOI: 10.1016/j.celrep.2020.02.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Revised: 11/20/2019] [Accepted: 02/03/2020] [Indexed: 12/13/2022] Open
Abstract
Aberrant hyperphosphorylation of the protein phosphatase 2A catalytic subunit (PP2Ac) at Tyr307 has been associated with aggressive disease and poor clinical outcome in multiple cancers. However, the study of reversible phosphorylation at this site has relied entirely upon the use of antibodies-most prominently, the clone E155. Here, we provide evidence that the E155 and F-8 phospho-Tyr307 antibodies cannot differentiate between phosphorylated and unphosphorylated forms of PP2Ac. The form of PP2Ac bound by these antibodies in H358 cells is unphosphorylated at the C-terminal tail. Furthermore, these antibodies are sensitive to additional protein modifications that occur near Tyr307, including Thr304 phosphorylation and Leu309 methylation, when these post-translational modifications are present. Thus, studies that used these antibodies to report PP2Ac hyperphosphorylation require reinterpretation, as these antibodies cannot be reliably used as readouts for a single PP2Ac post-translational modification (PTM) change.
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Affiliation(s)
- Sahar Mazhar
- Department of Pathology, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Daniel Leonard
- Department of Pathology, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Alejandro Sosa
- Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Daniela Schlatzer
- Center for Proteomics and Bioinformatics, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Dafydd Thomas
- Department of Pathology, Michigan Medicine, University of Michigan, Ann Arbor, MI 48109, USA
| | - Goutham Narla
- Division of Genetic Medicine, Department of Internal Medicine, Michigan Medicine, University of Michigan, Ann Arbor, MI 48109, USA.
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17
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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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18
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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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19
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Dzulko M, Pons M, Henke A, Schneider G, Krämer OH. The PP2A subunit PR130 is a key regulator of cell development and oncogenic transformation. Biochim Biophys Acta Rev Cancer 2020; 1874:188453. [PMID: 33068647 DOI: 10.1016/j.bbcan.2020.188453] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 10/10/2020] [Accepted: 10/11/2020] [Indexed: 12/25/2022]
Abstract
Protein phosphatase 2A (PP2A) is a major serine/threonine phosphatase. This enzyme is involved in a plethora of cellular processes, including apoptosis, autophagy, cell proliferation, and DNA repair. Remarkably, PP2A can act as a context-dependent tumor suppressor or promoter. Active PP2A complexes consist of structural (PP2A-A), regulatory (PP2A-B), and catalytic (PP2A-C) subunits. The regulatory subunits define the substrate specificity and the subcellular localization of the holoenzyme. Here we condense the increasing evidence that the PP2A B-type subunit PR130 is a critical regulator of cell identity and oncogenic transformation. We summarize knowledge on the biological functions of PR130 in normal and transformed cells, targets of the PP2A-PR130 complex, and how diverse extra- and intracellular stimuli control the expression and activity of PR130. We additionally review the impact of PP2A-PR130 on cardiac functions, neuronal processes, and anti-viral defense and how this might affect cancer development and therapy.
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Affiliation(s)
- Melanie Dzulko
- Department of Toxicology, University Medical Center, 55131 Mainz, Germany
| | - Miriam Pons
- Department of Toxicology, University Medical Center, 55131 Mainz, Germany
| | - Andreas Henke
- Section of Experimental Virology, Institute of Medical Microbiology, Jena University Hospital, Friedrich Schiller University, 07745 Jena, Germany
| | - Günter Schneider
- Klinik und Poliklinik für Innere Medizin II, Technical University of Munich, 81675 Munich, Germany
| | - Oliver H Krämer
- Department of Toxicology, University Medical Center, 55131 Mainz, Germany.
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20
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Wu B, Cai H, Tang S, Xu Y, Shi Q, Wei L, Meng L, Zhang N, Wang X, Xiao D, Zou Y, Yang X, Li X, Lu C. Methionine-Mediated Protein Phosphatase 2A Catalytic Subunit (PP2Ac) Methylation Ameliorates the Tauopathy Induced by Manganese in Cell and Animal Models. Neurotherapeutics 2020; 17:1878-1896. [PMID: 32959271 PMCID: PMC7851222 DOI: 10.1007/s13311-020-00930-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/04/2020] [Indexed: 01/10/2023] Open
Abstract
The molecular mechanism of Alzheimer-like cognitive impairment induced by manganese (Mn) exposure has not yet been fully clarified, and there are currently no effective interventions to treat neurodegenerative lesions related to manganism. Protein phosphatase 2 A (PP2A) is a major tau phosphatase and was recently identified as a potential therapeutic target molecule for neurodegenerative diseases; its activity is directed by the methylation status of the catalytic C subunit. Methionine is an essential amino acid, and its downstream metabolite S-adenosylmethionine (SAM) participates in transmethylation pathways as a methyl donor. In this study, the neurotoxic mechanism of Mn and the protective effect of methionine were evaluated in Mn-exposed cell and rat models. We show that Mn-induced neurotoxicity is characterized by PP2Ac demethylation accompanied by abnormally decreased LCMT-1 and increased PME-1, which are associated with tau hyperphosphorylation and spatial learning and memory deficits, and that the poor availability of SAM in the hippocampus is likely to determine the loss of PP2Ac methylation. Importantly, maintenance of local SAM levels through continuous supplementation with exogenous methionine, or through specific inhibition of PP2Ac demethylation by ABL127 administration in vitro, can effectively prevent tau hyperphosphorylation to reduce cellular oxidative stress, apoptosis, damage to cell viability, and rat memory deficits in cell or animal Mn exposure models. In conclusion, our data suggest that SAM and PP2Ac methylation may be novel targets for the treatment of Mn poisoning and neurotoxic mechanism-related tauopathies.
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Affiliation(s)
- Bin Wu
- School of Public Health, Guangxi Medical University, 22 Shuangyong Road, Nanning, 530021, Guangxi, People's Republic of China
- Guangxi Colleges and Universities Key Laboratory of Prevention and Control of Highly Prevalent Diseases, Guangxi Medical University, 22 Shuangyong Road, Nanning, 530021, Guangxi, People's Republic of China
| | - Haiqing Cai
- School of Public Health, Guangxi Medical University, 22 Shuangyong Road, Nanning, 530021, Guangxi, People's Republic of China
- Guangxi Colleges and Universities Key Laboratory of Prevention and Control of Highly Prevalent Diseases, Guangxi Medical University, 22 Shuangyong Road, Nanning, 530021, Guangxi, People's Republic of China
| | - Shen Tang
- School of Basic Medical Sciences, Guangxi Medical University, 22 Shuangyong Road, Nanning, 530021, Guangxi, People's Republic of China
| | - Yilu Xu
- School of Public Health, Guangxi Medical University, 22 Shuangyong Road, Nanning, 530021, Guangxi, People's Republic of China
- Guangxi Colleges and Universities Key Laboratory of Prevention and Control of Highly Prevalent Diseases, Guangxi Medical University, 22 Shuangyong Road, Nanning, 530021, Guangxi, People's Republic of China
| | - Qianqian Shi
- School of Public Health, Guangxi Medical University, 22 Shuangyong Road, Nanning, 530021, Guangxi, People's Republic of China
- Guangxi Colleges and Universities Key Laboratory of Prevention and Control of Highly Prevalent Diseases, Guangxi Medical University, 22 Shuangyong Road, Nanning, 530021, Guangxi, People's Republic of China
| | - Lancheng Wei
- School of Public Health, Guangxi Medical University, 22 Shuangyong Road, Nanning, 530021, Guangxi, People's Republic of China
- Guangxi Colleges and Universities Key Laboratory of Prevention and Control of Highly Prevalent Diseases, Guangxi Medical University, 22 Shuangyong Road, Nanning, 530021, Guangxi, People's Republic of China
| | - Ling Meng
- School of Basic Medical Sciences, Guangxi Medical University, 22 Shuangyong Road, Nanning, 530021, Guangxi, People's Republic of China
| | - Ning Zhang
- School of Public Health, Guangxi Medical University, 22 Shuangyong Road, Nanning, 530021, Guangxi, People's Republic of China
- Guangxi Colleges and Universities Key Laboratory of Prevention and Control of Highly Prevalent Diseases, Guangxi Medical University, 22 Shuangyong Road, Nanning, 530021, Guangxi, People's Republic of China
| | - Xinhang Wang
- School of Basic Medical Sciences, Guangxi Medical University, 22 Shuangyong Road, Nanning, 530021, Guangxi, People's Republic of China
| | - Deqiang Xiao
- School of Public Health, Guangxi Medical University, 22 Shuangyong Road, Nanning, 530021, Guangxi, People's Republic of China
- Guangxi Colleges and Universities Key Laboratory of Prevention and Control of Highly Prevalent Diseases, Guangxi Medical University, 22 Shuangyong Road, Nanning, 530021, Guangxi, People's Republic of China
| | - Yunfeng Zou
- School of Public Health, Guangxi Medical University, 22 Shuangyong Road, Nanning, 530021, Guangxi, People's Republic of China
- Guangxi Colleges and Universities Key Laboratory of Prevention and Control of Highly Prevalent Diseases, Guangxi Medical University, 22 Shuangyong Road, Nanning, 530021, Guangxi, People's Republic of China
| | - Xiaobo Yang
- School of Public Health, Guangxi Medical University, 22 Shuangyong Road, Nanning, 530021, Guangxi, People's Republic of China
- Guangxi Colleges and Universities Key Laboratory of Prevention and Control of Highly Prevalent Diseases, Guangxi Medical University, 22 Shuangyong Road, Nanning, 530021, Guangxi, People's Republic of China
| | - Xiyi Li
- School of Public Health, Guangxi Medical University, 22 Shuangyong Road, Nanning, 530021, Guangxi, People's Republic of China.
- Guangxi Colleges and Universities Key Laboratory of Prevention and Control of Highly Prevalent Diseases, Guangxi Medical University, 22 Shuangyong Road, Nanning, 530021, Guangxi, People's Republic of China.
| | - Cailing Lu
- School of Public Health, Guangxi Medical University, 22 Shuangyong Road, Nanning, 530021, Guangxi, People's Republic of China.
- Guangxi Colleges and Universities Key Laboratory of Prevention and Control of Highly Prevalent Diseases, Guangxi Medical University, 22 Shuangyong Road, Nanning, 530021, Guangxi, People's Republic of China.
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21
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Nasa I, Cressey LE, Kruse T, Hertz EPT, Gui J, Graves LM, Nilsson J, Kettenbach AN. Quantitative kinase and phosphatase profiling reveal that CDK1 phosphorylates PP2Ac to promote mitotic entry. Sci Signal 2020; 13:13/648/eaba7823. [PMID: 32900880 DOI: 10.1126/scisignal.aba7823] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The reciprocal regulation of phosphoprotein phosphatases (PPPs) by protein kinases is essential to cell cycle progression and control, particularly during mitosis for which the role of kinases has been extensively studied. PPPs perform much of the serine/threonine dephosphorylation in eukaryotic cells and achieve substrate selectivity and specificity through the interaction of distinct regulatory subunits with conserved catalytic subunits in holoenzyme complexes. Using a mass spectrometry-based chemical proteomics approach to enrich, identify, and quantify endogenous PPP holoenzyme complexes combined with kinase profiling, we investigated the phosphorylation-dependent regulation of PPP holoenzymes in mitotic cells. We found that cyclin-dependent kinase 1 (CDK1) phosphorylated a threonine residue on the catalytic subunit of the phosphatase PP2A, which disrupted its holoenzyme formation with the regulatory subunit B55. The consequent decrease in the dephosphorylation of PP2A-B55 substrates promoted mitotic entry. This direct phosphorylation by CDK1 was in addition to a previously reported indirect mechanism, thus adding a layer to the interaction between CDK1 and PP2A in regulating mitotic entry.
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Affiliation(s)
- Isha Nasa
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth College, Hanover, NH 03755, USA.,Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center at Dartmouth, Lebanon, NH 03766, USA
| | - Lauren E Cressey
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth College, Hanover, NH 03755, USA
| | - Thomas Kruse
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen, Denmark
| | - Emil P T Hertz
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen, Denmark
| | - Jiang Gui
- Department of Biomedical Data Science, Geisel School of Medicine at Dartmouth College, Lebanon, NH 03756, USA
| | - Lee M Graves
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
| | - Jakob Nilsson
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen, Denmark
| | - Arminja N Kettenbach
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth College, Hanover, NH 03755, USA. .,Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center at Dartmouth, Lebanon, NH 03766, USA
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22
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Bheri M, Mahiwal S, Sanyal SK, Pandey GK. Plant protein phosphatases: What do we know about their mechanism of action? FEBS J 2020; 288:756-785. [PMID: 32542989 DOI: 10.1111/febs.15454] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2020] [Revised: 05/27/2020] [Accepted: 06/09/2020] [Indexed: 12/30/2022]
Abstract
Protein phosphorylation is a major reversible post-translational modification. Protein phosphatases function as 'critical regulators' in signaling networks through dephosphorylation of proteins, which have been phosphorylated by protein kinases. A large understanding of their working has been sourced from animal systems rather than the plant or the prokaryotic systems. The eukaryotic protein phosphatases include phosphoprotein phosphatases (PPP), metallo-dependent protein phosphatases (PPM), protein tyrosine (Tyr) phosphatases (PTP), and aspartate (Asp)-dependent phosphatases. The PPP and PPM families are serine(Ser)/threonine(Thr)-specific phosphatases (STPs), while PTP family is Tyr specific. Dual-specificity phosphatases (DsPTPs/DSPs) dephosphorylate Ser, Thr, and Tyr residues. PTPs lack sequence homology with STPs, indicating a difference in catalytic mechanisms, while the PPP and PPM families share a similar structural fold indicating a common catalytic mechanism. The catalytic cysteine (Cys) residue in the conserved HCX5 R active site motif of the PTPs acts as a nucleophile during hydrolysis. The PPP members require metal ions, which coordinate the phosphate group of the substrate, followed by a nucleophilic attack by a water molecule and hydrolysis. The variable holoenzyme assembly of protein phosphatase(s) and the overlap with other post-translational modifications like acetylation and ubiquitination add to their complexity. Though their functional characterization is extensively reported in plants, the mechanistic nature of their action is still being explored by researchers. In this review, we exclusively overview the plant protein phosphatases with an emphasis on their mechanistic action as well as structural characteristics.
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Affiliation(s)
- Malathi Bheri
- Department of Plant Molecular Biology, University of Delhi South Campus, New Delhi, India
| | - Swati Mahiwal
- Department of Plant Molecular Biology, University of Delhi South Campus, New Delhi, India
| | - Sibaji K Sanyal
- Department of Plant Molecular Biology, University of Delhi South Campus, New Delhi, India
| | - Girdhar K Pandey
- Department of Plant Molecular Biology, University of Delhi South Campus, New Delhi, India
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23
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Reduced Expression of the PP2A Methylesterase, PME-1, or the PP2A Methyltransferase, LCMT-1, Alters Sensitivity to Beta-Amyloid-Induced Cognitive and Electrophysiological Impairments in Mice. J Neurosci 2020; 40:4596-4608. [PMID: 32341098 DOI: 10.1523/jneurosci.2983-19.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 03/27/2020] [Accepted: 04/17/2020] [Indexed: 12/16/2022] Open
Abstract
Beta-amyloid (Aβ) is thought to play a critical role in Alzheimer's disease (AD), and application of soluble oligomeric forms of Aβ produces AD-like impairments in cognition and synaptic plasticity in experimental systems. We found previously that transgenic overexpression of the PP2A methylesterase, PME-1, or the PP2A methyltransferase, LCMT-1, altered the sensitivity of mice to Aβ-induced impairments, suggesting that PME-1 inhibition may be an effective approach for preventing or treating these impairments. To explore this possibility, we examined the behavioral and electrophysiological effects of acutely applied synthetic Aβ oligomers in male and female mice heterozygous for either a PME-1 KO or an LCMT-1 gene-trap mutation. We found that heterozygous PME-1 KO mice were resistant to Aβ-induced impairments in cognition and synaptic plasticity, whereas LCMT-1 gene-trap mice showed increased sensitivity to Aβ-induced impairments. The heterozygous PME-1 KO mice produced normal levels of endogenous Aβ and exhibited normal electrophysiological responses to picomolar concentrations of Aβ, suggesting that reduced PME-1 expression in these animals protects against Aβ-induced impairments without impacting normal physiological Aβ functions. Together, these data provide additional support for roles for PME-1 and LCMT-1 in regulating sensitivity to Aβ-induced impairments, and suggest that inhibition of PME-1 may constitute a viable therapeutic approach for selectively protecting against the pathologic actions of Aβ in AD.SIGNIFICANCE STATEMENT Elevated levels of β-amyloid (Aβ) in the brain are thought to contribute to the cognitive impairments observed in Alzheimer's disease patients. Here we show that genetically reducing endogenous levels of the PP2A methylesterase, PME-1, prevents the cognitive and electrophysiological impairments caused by acute exposure to pathologic concentrations of Aβ without impairing normal physiological Aβ function or endogenous Aβ production. Conversely, reducing endogenous levels of the PP2A methyltransferase, LCMT-1, increases sensitivity to Aβ-induced impairments. These data offer additional insights into the molecular factors that control sensitivity to Aβ-induced impairments, and suggest that inhibiting PME-1 may constitute a viable therapeutic avenue for preventing Aβ-related impairments in Alzheimer's disease.
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24
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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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25
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Frohner IE, Mudrak I, Kronlachner S, Schüchner S, Ogris E. Antibodies recognizing the C terminus of PP2A catalytic subunit are unsuitable for evaluating PP2A activity and holoenzyme composition. Sci Signal 2020; 13:13/616/eaax6490. [PMID: 31992581 DOI: 10.1126/scisignal.aax6490] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The methyl-esterification of the C-terminal leucine of the protein phosphatase 2A (PP2A) catalytic (C) subunit is essential for the assembly of specific trimeric PP2A holoenzymes, and this region of the C subunit also contains two threonine and tyrosine phosphorylation sites. Most commercial antibodies-including the monoclonal antibody 1D6 that is part of a frequently used, commercial phosphatase assay kit-are directed toward the C terminus of the C subunit, raising questions as to their ability to recognize methylated and phosphorylated forms of the enzyme. Here, we tested several PP2A C antibodies, including monoclonal antibodies 1D6, 7A6, G-4, and 52F8 and the polyclonal antibody 2038 for their ability to specifically detect PP2A in its various modified forms, as well as to coprecipitate regulatory subunits. The tested antibodies preferentially recognized the nonmethylated form of the enzyme, and they did not coimmunoprecipitate trimeric holoenzymes containing the regulatory subunits B or B', an issue that precludes their use to monitor PP2A holoenzyme activity. Furthermore, some of the antibodies also recognized the phosphatase PP4, demonstrating a lack of specificity for PP2A. Together, these findings suggest that reinterpretation of the data generated by using these reagents is required.
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Affiliation(s)
- Ingrid E Frohner
- Center for Medical Biochemistry, Max Perutz Labs, Vienna BioCenter, Medical University of Vienna, Dr. Bohr-Gasse 9, A-1030 Vienna, Austria
| | - Ingrid Mudrak
- Center for Medical Biochemistry, Max Perutz Labs, Vienna BioCenter, Medical University of Vienna, Dr. Bohr-Gasse 9, A-1030 Vienna, Austria
| | - Stephanie Kronlachner
- Center for Medical Biochemistry, Max Perutz Labs, Vienna BioCenter, Medical University of Vienna, Dr. Bohr-Gasse 9, A-1030 Vienna, Austria
| | - Stefan Schüchner
- Center for Medical Biochemistry, Max Perutz Labs, Vienna BioCenter, Medical University of Vienna, Dr. Bohr-Gasse 9, A-1030 Vienna, Austria
| | - Egon Ogris
- Center for Medical Biochemistry, Max Perutz Labs, Vienna BioCenter, Medical University of Vienna, Dr. Bohr-Gasse 9, A-1030 Vienna, Austria.
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26
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Shen W, Gao C, Cueto R, Liu L, Fu H, Shao Y, Yang WY, Fang P, Choi ET, Wu Q, Yang X, Wang H. Homocysteine-methionine cycle is a metabolic sensor system controlling methylation-regulated pathological signaling. Redox Biol 2020; 28:101322. [PMID: 31605963 PMCID: PMC6812029 DOI: 10.1016/j.redox.2019.101322] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Revised: 09/03/2019] [Accepted: 09/06/2019] [Indexed: 12/14/2022] Open
Abstract
Homocysteine-Methionine (HM) cycle produces universal methyl group donor S-adenosylmethione (SAM), methyltransferase inhibitor S-adenosylhomocysteine (SAH) and homocysteine (Hcy). Hyperhomocysteinemia (HHcy) is established as an independent risk factor for cardiovascular disease (CVD) and other degenerative disease. We selected 115 genes in the extended HM cycle (31 metabolic enzymes and 84 methyltransferases), examined their protein subcellular location/partner protein, investigated their mRNA levels and mapped their corresponding histone methylation status in 35 disease conditions via mining a set of public databases and intensive literature research. We have 6 major findings. 1) All HM metabolic enzymes are located only in the cytosol except for cystathionine-β-synthase (CBS), which was identified in both cytosol and nucleus. 2) Eight disease conditions encountered only histone hypomethylation on 8 histone residues (H3R2/K4/R8/K9/K27/K36/K79 and H4R3). Nine disease conditions had only histone hypermethylation on 8 histone residues (H3R2/K4/K9/K27/K36/K79 and H4R3/K20). 3) We classified 9 disease types with differential HM cycle expression pattern. Eleven disease conditions presented most 4 HM cycle pathway suppression. 4) Three disease conditions had all 4 HM cycle pathway suppression and only histone hypomethylation on H3R2/K4/R8/K9/K36 and H4R3. 5) Eleven HM cycle metabolic enzymes interact with 955 proteins. 6) Five paired HM cycle proteins interact with each other. We conclude that HM cycle is a key metabolic sensor system which mediates receptor-independent metabolism-associated danger signal recognition and modulates SAM/SAH-dependent methylation in disease conditions and that hypomethylation on frequently modified histone residues is a key mechanism for metabolic disorders, autoimmune disease and CVD. We propose that HM metabolism takes place in the cytosol, that nuclear methylation equilibration requires a nuclear-cytosol transfer of SAM/SAH/Hcy, and that Hcy clearance is essential for genetic protection.
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Affiliation(s)
- Wen Shen
- Department of Cardiovascular Medicine, The Second Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China; Centers for Metabolic Disease Research, Lewis Katz School of Medicine at Temple University, Philadelphia, PA, USA
| | - Chao Gao
- Centers for Metabolic Disease Research, Lewis Katz School of Medicine at Temple University, Philadelphia, PA, USA
| | - Ramon Cueto
- Centers for Metabolic Disease Research, Lewis Katz School of Medicine at Temple University, Philadelphia, PA, USA
| | - Lu Liu
- Centers for Metabolic Disease Research, Lewis Katz School of Medicine at Temple University, Philadelphia, PA, USA
| | - Hangfei Fu
- Centers for Metabolic Disease Research, Lewis Katz School of Medicine at Temple University, Philadelphia, PA, USA
| | - Ying Shao
- Centers for Metabolic Disease Research, Lewis Katz School of Medicine at Temple University, Philadelphia, PA, USA
| | - William Y Yang
- Centers for Metabolic Disease Research, Lewis Katz School of Medicine at Temple University, Philadelphia, PA, USA
| | - Pu Fang
- Centers for Metabolic Disease Research, Lewis Katz School of Medicine at Temple University, Philadelphia, PA, USA
| | - Eric T Choi
- Centers for Metabolic Disease Research, Lewis Katz School of Medicine at Temple University, Philadelphia, PA, USA; Division of Vascular & Endovascular Surgery, Department of Surgery, Lewis Katz School of Medicine at Temple University, Philadelphia, PA, USA
| | - Qinghua Wu
- Department of Cardiovascular Medicine, The Second Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China.
| | - Xiaofeng Yang
- Centers for Metabolic Disease Research, Lewis Katz School of Medicine at Temple University, Philadelphia, PA, USA
| | - Hong Wang
- Centers for Metabolic Disease Research, Lewis Katz School of Medicine at Temple University, Philadelphia, PA, USA.
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27
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Brautigan DL, Shenolikar S. Protein Serine/Threonine Phosphatases: Keys to Unlocking Regulators and Substrates. Annu Rev Biochem 2019; 87:921-964. [PMID: 29925267 DOI: 10.1146/annurev-biochem-062917-012332] [Citation(s) in RCA: 110] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Protein serine/threonine phosphatases (PPPs) are ancient enzymes, with distinct types conserved across eukaryotic evolution. PPPs are segregated into types primarily on the basis of the unique interactions of PPP catalytic subunits with regulatory proteins. The resulting holoenzymes dock substrates distal to the active site to enhance specificity. This review focuses on the subunit and substrate interactions for PPP that depend on short linear motifs. Insights about these motifs from structures of holoenzymes open new opportunities for computational biology approaches to elucidate PPP networks. There is an expanding knowledge base of posttranslational modifications of PPP catalytic and regulatory subunits, as well as of their substrates, including phosphorylation, acetylation, and ubiquitination. Cross talk between these posttranslational modifications creates PPP-based signaling. Knowledge of PPP complexes, signaling clusters, as well as how PPPs communicate with each other in response to cellular signals should unlock the doors to PPP networks and signaling "clouds" that orchestrate and coordinate different aspects of cell physiology.
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Affiliation(s)
- David L Brautigan
- Center for Cell Signaling and Department of Microbiology, Immunology and Cancer Biology, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA;
| | - Shirish Shenolikar
- Signature Research Programs in Cardiovascular and Metabolic Disorders and Neuroscience and Behavioral Disorders, Duke-NUS Medical School, Singapore 169857
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28
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Elgenaidi IS, Spiers JP. Regulation of the phosphoprotein phosphatase 2A system and its modulation during oxidative stress: A potential therapeutic target? Pharmacol Ther 2019; 198:68-89. [PMID: 30797822 DOI: 10.1016/j.pharmthera.2019.02.011] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Accepted: 02/15/2019] [Indexed: 02/06/2023]
Abstract
Phosphoprotein phosphatases are of growing interest in the pathophysiology of many diseases and are often the neglected partner of protein kinases. One family member, PP2A, accounts for dephosphorylation of ~55-70% of all serine/threonine phosphosites. Interestingly, dysregulation of kinase signalling is a hallmark of many diseases in which an increase in oxidative stress is also noted. With this in mind, we assess the evidence to support oxidative stress-mediated regulation of the PP2A system In this article, we first present an overview of the PP2A system before providing an analysis of the regulation of PP2A by endogenous inhibitors, post translational modification, and miRNA. Next, a detailed critique of data implicating reactive oxygen species, ischaemia, ischaemia-reperfusion, and hypoxia in regulating the PP2A holoenzyme and associated regulators is presented. Finally, the pharmacological targeting of PP2A, its endogenous inhibitors, and enzymes responsible for its post-translational modification are covered. There is extensive evidence that oxidative stress modulates multiple components of the PP2A system, however, most of the data pertains to the catalytic subunit of PP2A. Irrespective of the underlying aetiology, free radical-mediated attenuation of PP2A activity is an emerging theme. However, in many instances, a dichotomy exists, which requires clarification and mechanistic insight. Nevertheless, this raises the possibility that pharmacological activation of PP2A, either through small molecule activators of PP2A or CIP2A/SET antagonists may be beneficial in modulating the cellular response to oxidative stress. A better understanding of which, will have wide ranging implications for cancer, heart disease and inflammatory conditions.
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Affiliation(s)
- I S Elgenaidi
- Department of Pharmacology and Therapeutics, Trinity College Dublin, Ireland
| | - J P Spiers
- Department of Pharmacology and Therapeutics, Trinity College Dublin, Ireland.
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29
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Fowle H, Zhao Z, Graña X. PP2A holoenzymes, substrate specificity driving cellular functions and deregulation in cancer. Adv Cancer Res 2019; 144:55-93. [PMID: 31349904 PMCID: PMC9994639 DOI: 10.1016/bs.acr.2019.03.009] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
PP2A is a highly conserved eukaryotic serine/threonine protein phosphatase of the PPP family of phosphatases with fundamental cellular functions. In cells, PP2A targets specific subcellular locations and substrates by forming heterotrimeric holoenzymes, where a core dimer consisting of scaffold (A) and catalytic (C) subunits complexes with one of many B regulatory subunits. PP2A plays a key role in positively and negatively regulating a myriad of cellular processes, as it targets a very sizable fraction of the cellular substrates phosphorylated on Ser/Thr residues. This review focuses on insights made toward the understanding on how the subunit composition and structure of PP2A holoenzymes mediates substrate specificity, the role of substrate modulation in the signaling of cellular division, growth, and differentiation, and its deregulation in cancer.
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Affiliation(s)
- Holly Fowle
- Fels Institute for Cancer Research and Molecular Biology and Temple University Lewis Katz School of Medicine, Philadelphia, PA, United States
| | - Ziran Zhao
- Fels Institute for Cancer Research and Molecular Biology and Temple University Lewis Katz School of Medicine, Philadelphia, PA, United States
| | - Xavier Graña
- Fels Institute for Cancer Research and Molecular Biology and Temple University Lewis Katz School of Medicine, Philadelphia, PA, United States.
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30
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Yabe R, Tsuji S, Mochida S, Ikehara T, Usui T, Ohama T, Sato K. A stable association with PME-1 may be dispensable for PP2A demethylation - implications for the detection of PP2A methylation and immunoprecipitation. FEBS Open Bio 2018; 8:1486-1496. [PMID: 30186749 PMCID: PMC6120246 DOI: 10.1002/2211-5463.12485] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Revised: 06/06/2018] [Accepted: 06/27/2018] [Indexed: 12/03/2022] Open
Abstract
Reversible methyl-esterification (methylation) of Leu309 in the protein phosphatase 2A catalytic subunit (PP2Ac) is essential for proper biogenesis of the PP2A holoenzyme. Accumulating evidence links PP2Ac methylation to diseases, including cancer and neurodegenerative disorders. Protein phosphatase methyl-esterase (PME-1) specifically catalyzes PP2Ac demethylation. We demonstrate that PP2Ac is demethylated in cell extracts even at 0 °C unless prevented by a PME-1 methyl-esterase inhibitor. This promotes dissociation of PP2A heterotrimers with B55 or PR72 subunits, but not those with B56 subunits. These results reveal differential sensitivity of ABC heterotrimers to methylation status of the C subunit. Our study advocates caution when interpreting earlier findings, offers an effective protocol for preserving PP2A complexes, and reveals key distinctions between B subunits and their interactions with the AC core dimer of PP2A.
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Affiliation(s)
- Ryotaro Yabe
- Laboratory of Veterinary PharmacologyJoint Faculty of Veterinary MedicineYamaguchi UniversityJapan
| | - Shunya Tsuji
- Laboratory of Veterinary PharmacologyJoint Faculty of Veterinary MedicineYamaguchi UniversityJapan
| | - Satoru Mochida
- Priority Organization for Innovation and ExcellenceKumamoto UniversityJapan
| | - Tsuyoshi Ikehara
- Department of Food Science and TechnologyNational Fisheries UniversityShimonosekiJapan
| | - Tatsuya Usui
- Laboratory of Veterinary PharmacologyFaculty of AgricultureTokyo University of Agriculture and TechnologyFuchuJapan
| | - Takashi Ohama
- Laboratory of Veterinary PharmacologyJoint Faculty of Veterinary MedicineYamaguchi UniversityJapan
| | - Koichi Sato
- Laboratory of Veterinary PharmacologyJoint Faculty of Veterinary MedicineYamaguchi UniversityJapan
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Lee JA, Wang Z, Sambo D, Bunting KD, Pallas DC. Global loss of leucine carboxyl methyltransferase-1 causes severe defects in fetal liver hematopoiesis. J Biol Chem 2018; 293:9636-9650. [PMID: 29735529 PMCID: PMC6016458 DOI: 10.1074/jbc.ra118.002012] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Revised: 04/12/2018] [Indexed: 11/06/2022] Open
Abstract
Leucine carboxyl methyltransferase-1 (LCMT-1) methylates the C-terminal leucine α-carboxyl group of the catalytic subunits of the protein phosphatase 2A (PP2A) subfamily of protein phosphatases, PP2Ac, PP4c, and PP6c. LCMT-1 differentially regulates the formation and function of a subset of the heterotrimeric complexes that PP2A and PP4 form with their regulatory subunits. Global LCMT-1 knockout causes embryonic lethality in mice, but LCMT-1 function in development is unknown. In this study, we analyzed the effects of global LCMT-1 loss on embryonic development. LCMT-1 knockout causes loss of PP2Ac methylation, indicating that LCMT-1 is the sole PP2Ac methyltransferase. PP2A heterotrimers containing the Bα and Bδ B-type subunits are dramatically reduced in whole embryos, and the steady-state levels of PP2Ac and the PP2A structural A subunit are also down ∼30%. Strikingly, global loss of LCMT-1 causes severe defects in fetal hematopoiesis and usually death by embryonic day 16.5. Fetal livers of homozygous lcmt-1 knockout embryos display hypocellularity, elevated apoptosis, and greatly reduced numbers of hematopoietic stem and progenitor cell-enriched Kit+Lin-Sca1+ cells. The percent cycling cells and mitotic indices of WT and lcmt-1 knockout fetal liver cells are similar, suggesting that hypocellularity may be due to a combination of apoptosis and/or defects in specification, self-renewal, or survival of stem cells. Indicative of a possible intrinsic defect in stem cells, noncompetitive and competitive transplantation experiments reveal that lcmt-1 loss causes a severe multilineage hematopoietic repopulating defect. Therefore, this study reveals a novel role for LCMT-1 as a key player in fetal liver hematopoiesis.
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Affiliation(s)
- Jocelyn A Lee
- From the Department of Biochemistry, Winship Cancer Institute, the Biochemistry, Cell, and Developmental Graduate Program, and
| | - Zhengqi Wang
- the Aflac Cancer and Blood Disorders Center of Children's Healthcare of Atlanta, Department of Pediatrics, Winship Cancer Institute, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Danielle Sambo
- From the Department of Biochemistry, Winship Cancer Institute, the Biochemistry, Cell, and Developmental Graduate Program, and
| | - Kevin D Bunting
- the Aflac Cancer and Blood Disorders Center of Children's Healthcare of Atlanta, Department of Pediatrics, Winship Cancer Institute, Emory University School of Medicine, Atlanta, Georgia 30322
| | - David C Pallas
- From the Department of Biochemistry, Winship Cancer Institute, the Biochemistry, Cell, and Developmental Graduate Program, and
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Ma Q, Feng Y, Deng K, Shao H, Sui T, Zhang X, Sun X, Jin L, Ma Z, Luo G. Unique Responses of Hepatocellular Carcinoma and Cholangiocarcinoma Cell Lines toward Cantharidin and Norcantharidin. J Cancer 2018; 9:2183-2190. [PMID: 29937938 PMCID: PMC6010690 DOI: 10.7150/jca.25454] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Accepted: 03/26/2018] [Indexed: 12/18/2022] Open
Abstract
The present study aimed to investigate whether cell lines from human gastric and liver cancers respond differently toward cantharidin (CTD) and norcantharidin (NCTD) than other types of cancer cells. We first established the half maximal inhibitory concentrations (IC50s) of CTD for a large panel of cancer cell lines representing the 12 major types of human cancers and the mode of cell death induced by the two compounds. We next compared the growth inhibitory effects as well as the corresponding modes of action of CTD and NCTD. The IncuCyte ZOOM system was used as a semi-high throughput means to define IC50s and 90% inhibitory doses (IC90s) as a reference for the maximal tolerable doses (MTDs) for the two compounds in 72 cancer cell lines. Classical clonogenic survival assay was used to assess the anti-proliferative effect of CTD on selected cell lines of interest. In addition, DNA content-based flow was used to interrogate the modes of cell death following CTD or NCTD exposure. The results of these experiments led to several findings. 1). Cell lines representing hepatocellular carcinomas (HCCs) and cholangiocarcinomas (CCs) were among the most sensitive toward CTD, consistent with the previous clinical study of this compound and its source of origin, Mylabris. 2). Among the individual cell lines of a given cancer types, the sensitivity trends for CTD and NCTD did not exhibit a good correlation. 3) CTD and NCTD caused distinctive cytotoxic effects on HepG2 cells. Specifically, while a cytostatic effect is the primary cause of growth inhibition of CTD, cytotoxic effect is the main contributing factor for the growth inhibition of NTCD. These results indicate that liver cancer cell lines are among the most sensitive to CTD and that CTD and NCTD exhibit their effects through distinct mechanisms.
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Affiliation(s)
- Qixiang Ma
- School of Life Sciences, Centre For Translational Oncology, Beijing University of Chinese Medicine, 11 Beisanhuandong Road, Chaoyang District, Beijing 100029, People's Republic of China
| | - Yanyan Feng
- School of Life Sciences, Centre For Translational Oncology, Beijing University of Chinese Medicine, 11 Beisanhuandong Road, Chaoyang District, Beijing 100029, People's Republic of China
| | - Kaiwen Deng
- School of Life Sciences, Centre For Translational Oncology, Beijing University of Chinese Medicine, 11 Beisanhuandong Road, Chaoyang District, Beijing 100029, People's Republic of China
| | - Haozhen Shao
- School of Life Sciences, Centre For Translational Oncology, Beijing University of Chinese Medicine, 11 Beisanhuandong Road, Chaoyang District, Beijing 100029, People's Republic of China
| | - Tongtong Sui
- School of Life Sciences, Centre For Translational Oncology, Beijing University of Chinese Medicine, 11 Beisanhuandong Road, Chaoyang District, Beijing 100029, People's Republic of China
| | - Xin Zhang
- School of Life Sciences, Centre For Translational Oncology, Beijing University of Chinese Medicine, 11 Beisanhuandong Road, Chaoyang District, Beijing 100029, People's Republic of China
| | - Xiao Sun
- School of Life Sciences, Centre For Translational Oncology, Beijing University of Chinese Medicine, 11 Beisanhuandong Road, Chaoyang District, Beijing 100029, People's Republic of China
| | - Lin Jin
- School of Life Sciences, Centre For Translational Oncology, Beijing University of Chinese Medicine, 11 Beisanhuandong Road, Chaoyang District, Beijing 100029, People's Republic of China
| | - Zhitao Ma
- School of Life Sciences, Centre For Translational Oncology, Beijing University of Chinese Medicine, 11 Beisanhuandong Road, Chaoyang District, Beijing 100029, People's Republic of China
| | - Guangbin Luo
- School of Life Sciences, Centre For Translational Oncology, Beijing University of Chinese Medicine, 11 Beisanhuandong Road, Chaoyang District, Beijing 100029, People's Republic of China.,Department of Genetics and Genome Sciences, Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, OH 44106, USA
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Park HJ, Lee KW, Oh S, Yan R, Zhang J, Beach TG, Adler CH, Voronkov M, Braithwaite SP, Stock JB, Mouradian MM. Protein Phosphatase 2A and Its Methylation Modulating Enzymes LCMT-1 and PME-1 Are Dysregulated in Tauopathies of Progressive Supranuclear Palsy and Alzheimer Disease. J Neuropathol Exp Neurol 2018; 77:139-148. [PMID: 29281045 PMCID: PMC6251692 DOI: 10.1093/jnen/nlx110] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Hyperphosphorylated tau aggregates are characteristic of tauopathies including progressive supranuclear palsy (PSP) and Alzheimer disease (AD), but factors contributing to pathologic tau phosphorylation are not well understood. Here, we studied the regulation of the major tau phosphatase, the heterotrimeric AB55αC protein phosphatase 2 A (PP2A), in PSP and AD. The assembly and activity of this PP2A isoform are regulated by reversible carboxyl methylation of its catalytic C subunit, while the B subunit confers substrate specificity. We sought to address whether the decreases in PP2A methylation and its methylating enzyme, leucine carboxyl methyltransferase (LCMT-1), which are reported in AD, relate to tau pathology or to concomitant amyloid pathology by comparing them in the relatively pure tauopathy PSP. Immunohistochemical analysis of frontal cortices showed that methyl-PP2A is reduced while demethyl-PP2A is increased, with no changes in total PP2A or B55α subunit, resulting in a reduction in the methyl/demethyl PP2A ratio of 63% in PSP and 75% in AD compared to controls. Similarly, Western blot analyses showed a decrease of methyl-PP2A and an increase of demethyl-PP2A with a concomitant reduction in the methyl/demethyl PP2A ratio in both PSP (74%) and AD (76%) brains. This was associated with a decrease in LCMT-1 and an increase in the demethylating enzyme, protein phosphatase methylesterase (PME-1), in both diseases. These findings suggest that PP2A dysregulation in tauopathies may contribute to the accumulation of hyperphosphorylated tau and to neurodegeneration.
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Affiliation(s)
- Hye-Jin Park
- Center for Neurodegenerative and Neuroimmunologic Diseases, Department of Neurology, Rutgers—Robert Wood Johnson Medical School, Piscataway, New Jersey
| | - Kang-Woo Lee
- Center for Neurodegenerative and Neuroimmunologic Diseases, Department of Neurology, Rutgers—Robert Wood Johnson Medical School, Piscataway, New Jersey
| | - Stephanie Oh
- Center for Neurodegenerative and Neuroimmunologic Diseases, Department of Neurology, Rutgers—Robert Wood Johnson Medical School, Piscataway, New Jersey
| | - Run Yan
- Center for Neurodegenerative and Neuroimmunologic Diseases, Department of Neurology, Rutgers—Robert Wood Johnson Medical School, Piscataway, New Jersey
| | - Jie Zhang
- Center for Neurodegenerative and Neuroimmunologic Diseases, Department of Neurology, Rutgers—Robert Wood Johnson Medical School, Piscataway, New Jersey
| | | | | | | | | | - Jeffry B Stock
- Signum Biosciences, Princeton, New Jersey
- Department of Molecular Biology, Princeton University, Princeton, New Jersey
| | - M Maral Mouradian
- Center for Neurodegenerative and Neuroimmunologic Diseases, Department of Neurology, Rutgers—Robert Wood Johnson Medical School, Piscataway, New Jersey
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34
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Lee HY, Itahana Y, Schuechner S, Fukuda M, Je HS, Ogris E, Virshup DM, Itahana K. Ca2+-dependent demethylation of phosphatase PP2Ac promotes glucose deprivation–induced cell death independently of inhibiting glycolysis. Sci Signal 2018; 11:11/512/eaam7893. [DOI: 10.1126/scisignal.aam7893] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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35
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Asam K, Staniszewski A, Zhang H, Melideo SL, Mazzeo A, Voronkov M, Huber KL, Pérez E, Stock M, Stock JB, Arancio O, Nicholls RE. Eicosanoyl-5-hydroxytryptamide (EHT) prevents Alzheimer's disease-related cognitive and electrophysiological impairments in mice exposed to elevated concentrations of oligomeric beta-amyloid. PLoS One 2017; 12:e0189413. [PMID: 29253878 PMCID: PMC5734769 DOI: 10.1371/journal.pone.0189413] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Accepted: 11/24/2017] [Indexed: 02/04/2023] Open
Abstract
Soluble forms of oligomeric beta-amyloid (Aβ) are thought to play a central role in Alzheimer's disease (AD). Transgenic manipulation of methylation of the serine/threonine protein phosphatase, PP2A, was recently shown to alter the sensitivity of mice to AD-related impairments resulting from acute exposure to elevated levels of Aβ. In addition, eicosanoyl-5-hydroxytryptamide (EHT), a naturally occurring component from coffee beans that modulates PP2A methylation, was shown to confer therapeutic benefits in rodent models of AD and Parkinson's disease. Here, we tested the hypothesis that EHT protects animals from the pathological effects of exposure to elevated levels of soluble oligomeric Aβ. We treated mice with EHT-containing food at two different doses and assessed the sensitivity of these animals to Aβ-induced behavioral and electrophysiological impairments. We found that EHT administration protected animals from Aβ-induced cognitive impairments in both a radial-arm water maze and contextual fear conditioning task. We also found that both chronic and acute EHT administration prevented Aβ-induced impairments in long-term potentiation. These data add to the accumulating evidence suggesting that interventions with pharmacological agents, such as EHT, that target PP2A activity may be therapeutically beneficial for AD and other neurological conditions.
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Affiliation(s)
- Kesava Asam
- Department of Pathology and Cell Biology, Columbia University, New York, NY, United States of America
- The Taub Institute for Research on Alzheimer’s Disease and the Aging Brain, Columbia University, New York, NY, United States of America
| | - Agnieszka Staniszewski
- Department of Pathology and Cell Biology, Columbia University, New York, NY, United States of America
- The Taub Institute for Research on Alzheimer’s Disease and the Aging Brain, Columbia University, New York, NY, United States of America
| | - Hong Zhang
- Department of Pathology and Cell Biology, Columbia University, New York, NY, United States of America
- The Taub Institute for Research on Alzheimer’s Disease and the Aging Brain, Columbia University, New York, NY, United States of America
| | - Scott L. Melideo
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, United States of America
| | - Adolfo Mazzeo
- Department of Pathology and Cell Biology, Columbia University, New York, NY, United States of America
- The Taub Institute for Research on Alzheimer’s Disease and the Aging Brain, Columbia University, New York, NY, United States of America
| | - Michael Voronkov
- Signum Biosciences, 133 Wall Street, Princeton, New Jersey, United States of America
| | - Kristen L. Huber
- Signum Biosciences, 133 Wall Street, Princeton, New Jersey, United States of America
| | - Eduardo Pérez
- Signum Biosciences, 133 Wall Street, Princeton, New Jersey, United States of America
| | - Maxwell Stock
- Signum Biosciences, 133 Wall Street, Princeton, New Jersey, United States of America
| | - Jeffry B. Stock
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, United States of America
- Signum Biosciences, 133 Wall Street, Princeton, New Jersey, United States of America
| | - Ottavio Arancio
- Department of Pathology and Cell Biology, Columbia University, New York, NY, United States of America
- The Taub Institute for Research on Alzheimer’s Disease and the Aging Brain, Columbia University, New York, NY, United States of America
- Department of Medicine, Columbia University, New York, NY, United States of America
| | - Russell E. Nicholls
- Department of Pathology and Cell Biology, Columbia University, New York, NY, United States of America
- The Taub Institute for Research on Alzheimer’s Disease and the Aging Brain, Columbia University, New York, NY, United States of America
- * E-mail:
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36
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Therapeutic targeting of PP2A. Int J Biochem Cell Biol 2017; 96:182-193. [PMID: 29107183 DOI: 10.1016/j.biocel.2017.10.008] [Citation(s) in RCA: 117] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Revised: 10/13/2017] [Accepted: 10/16/2017] [Indexed: 12/19/2022]
Abstract
Protein phosphatase 2A (PP2A) is a major serine/threonine phosphatase that regulates many cellular processes. Given the central role of PP2A in regulating diverse biological functions and its dysregulation in many diseases, including cancer, PP2A directed therapeutics have become of great interest. The main approaches leveraged thus far can be categorized as follows: 1) inhibiting endogenous inhibitors of PP2A, 2) targeted disruption of post translational modifications on PP2A subunits, or 3) direct targeting of PP2A. Additional insight into the structural, molecular, and biological framework driving the efficacy of these therapeutic strategies will provide a foundation for the refinement and development of novel and clinically tractable PP2A targeted therapies.
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37
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Glucocorticoid Receptor-mediated transactivation is hampered by Striatin-3, a novel interaction partner of the receptor. Sci Rep 2017; 7:8941. [PMID: 28827617 PMCID: PMC5567040 DOI: 10.1038/s41598-017-09246-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Accepted: 07/19/2017] [Indexed: 12/12/2022] Open
Abstract
The transcriptional activity of the glucocorticoid receptor (GR) is co-determined by its ability to recruit a vast and varying number of cofactors. We here identify Striatin-3 (STRN3) as a novel interaction partner of GR that interferes with GR’s ligand-dependent transactivation capacity. Remarkably, STRN3 selectively affects only GR-dependent transactivation and leaves GR-dependent transrepression mechanisms unhampered. We found that STRN3 down-regulates GR transactivation by an additional recruitment of the catalytic subunit of protein phosphatase 2A (PPP2CA) to GR. We hypothesize the existence of a functional trimeric complex in the nucleus, able to dephosphorylate GR at serine 211, a known marker for GR transactivation in a target gene-dependent manner. The presence of STRN3 appears an absolute prerequisite for PPP2CA to engage in a complex with GR. Herein, the C-terminal domain of GR is essential, reflecting ligand-dependency, yet other receptor parts are also needed to create additional contacts with STRN3.
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38
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Functional importance of PP2A regulatory subunit loss in breast cancer. Breast Cancer Res Treat 2017; 166:117-131. [DOI: 10.1007/s10549-017-4403-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2017] [Accepted: 07/15/2017] [Indexed: 11/25/2022]
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39
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Han EH, Petrella DP, Blakeslee JJ. 'Bending' models of halotropism: incorporating protein phosphatase 2A, ABCB transporters, and auxin metabolism. JOURNAL OF EXPERIMENTAL BOTANY 2017; 68:3071-3089. [PMID: 28899081 DOI: 10.1093/jxb/erx127] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Salt stress causes worldwide reductions in agricultural yields, a problem that is exacerbated by the depletion of global freshwater reserves and the use of contaminated or recycled water (i.e. effluent water). Additionally, salt stress can occur as cultivated areas are subjected to frequent rounds of irrigation followed by periods of moderate to severe evapotranspiration, which can result in the heterogeneous aggregation of salts in agricultural soils. Our understanding of the later stages of salt stress and the mechanisms by which salt is transported out of cells and roots has greatly improved over the last decade. The precise mechanisms by which plant roots perceive salt stress and translate this perception into adaptive, directional growth away from increased salt concentrations (i.e. halotropism), however, are not well understood. Here, we provide a review of the current knowledge surrounding the early responses to salt stress and the initiation of halotropism, including lipid signaling, protein phosphorylation cascades, and changes in auxin metabolism and/or transport. Current models of halotropism have focused on the role of PIN2- and PIN1-mediated auxin efflux in initiating and controlling halotropism. Recent studies, however, suggest that additional factors such as ABCB transporters, protein phosphatase 2A activity, and auxin metabolism should be included in the model of halotropic growth.
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Affiliation(s)
- Eun Hyang Han
- Department of Horticulture and Crop Science, The Ohio State University/OARDC, Wooster, OH, USA
| | - Dominic P Petrella
- Department of Horticulture and Crop Science, The Ohio State University/OARDC, Wooster, OH, USA
| | - Joshua J Blakeslee
- Department of Horticulture and Crop Science, OARDC Metabolite Analysis Cluster (OMAC), The Ohio State University/OARDC, Wooster, OH, USA
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40
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Regulation of protein phosphatase 2A (PP2A) tumor suppressor function by PME-1. Biochem Soc Trans 2016; 44:1683-1693. [DOI: 10.1042/bst20160161] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Revised: 08/06/2016] [Accepted: 09/09/2016] [Indexed: 02/06/2023]
Abstract
Protein phosphatase 2A (PP2A) plays a major role in maintaining cellular signaling homeostasis by dephosphorylation of a variety of signaling proteins and acts as a tumor suppressor. Protein phosphatase methylesterase-1 (PME-1) negatively regulates PP2A activity by highly complex mechanisms that are reviewed here. Importantly, recent studies have shown that PME-1 promotes oncogenic MAPK/ERK and AKT pathway activities in various cancer types. In human glioma, high PME-1 expression correlates with tumor progression and kinase inhibitor resistance. We discuss the emerging cancer-associated function of PME-1 and its potential clinical relevance.
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41
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Du TT, Wang L, Duan CL, Lu LL, Zhang JL, Gao G, Qiu XB, Wang XM, Yang H. GBA deficiency promotes SNCA/α-synuclein accumulation through autophagic inhibition by inactivated PPP2A. Autophagy 2016; 11:1803-20. [PMID: 26378614 DOI: 10.1080/15548627.2015.1086055] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Loss-of-function mutations in the gene encoding GBA (glucocerebrosidase, β, acid), the enzyme deficient in the lysosomal storage disorder Gaucher disease, elevate the risk of Parkinson disease (PD), which is characterized by the misprocessing of SNCA/α-synuclein. However, the mechanistic link between GBA deficiency and SNCA accumulation remains poorly understood. In this study, we found that loss of GBA function resulted in increased levels of SNCA via inhibition of the autophagic pathway in SK-N-SH neuroblastoma cells, primary rat cortical neurons, or the rat striatum. Furthermore, expression of the autophagy pathway component BECN1 was downregulated as a result of the GBA knockdown-induced decrease in glucocerebrosidase activity. Most importantly, inhibition of autophagy by loss of GBA function was associated with PPP2A (protein phosphatase 2A) inactivation via Tyr307 phosphorylation. C2-ceramide (C2), a PPP2A agonist, activated autophagy in GBA-silenced cells, while GBA knockdown-induced SNCA accumulation was reversed by C2 or rapamycin (an autophagy inducer), suggesting that PPP2A plays an important role in the GBA knockdown-mediated inhibition of autophagy. These findings demonstrate that loss of GBA function may contribute to SNCA accumulation through inhibition of autophagy via PPP2A inactivation, thereby providing a mechanistic basis for the increased PD risk associated with GBA deficiency.
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Affiliation(s)
- Ting-Ting Du
- a Center of Parkinson Disease Beijing Institute for Brain Disorders; Key Laboratory for Neurodegenerative Disease of the Ministry of Education; Department of Neurobiology Capital Medical University ; Beijing , China.,b Key Laboratory of Cell Proliferation and Regulation Biology; Ministry of Education; College of Life Sciences; Beijing Normal University ; Beijing , China
| | - Le Wang
- a Center of Parkinson Disease Beijing Institute for Brain Disorders; Key Laboratory for Neurodegenerative Disease of the Ministry of Education; Department of Neurobiology Capital Medical University ; Beijing , China
| | - Chun-Li Duan
- a Center of Parkinson Disease Beijing Institute for Brain Disorders; Key Laboratory for Neurodegenerative Disease of the Ministry of Education; Department of Neurobiology Capital Medical University ; Beijing , China
| | - Ling-Ling Lu
- a Center of Parkinson Disease Beijing Institute for Brain Disorders; Key Laboratory for Neurodegenerative Disease of the Ministry of Education; Department of Neurobiology Capital Medical University ; Beijing , China
| | - Jian-Liang Zhang
- a Center of Parkinson Disease Beijing Institute for Brain Disorders; Key Laboratory for Neurodegenerative Disease of the Ministry of Education; Department of Neurobiology Capital Medical University ; Beijing , China
| | - Ge Gao
- a Center of Parkinson Disease Beijing Institute for Brain Disorders; Key Laboratory for Neurodegenerative Disease of the Ministry of Education; Department of Neurobiology Capital Medical University ; Beijing , China
| | - Xiao-Bo Qiu
- b Key Laboratory of Cell Proliferation and Regulation Biology; Ministry of Education; College of Life Sciences; Beijing Normal University ; Beijing , China
| | - Xiao-Min Wang
- a Center of Parkinson Disease Beijing Institute for Brain Disorders; Key Laboratory for Neurodegenerative Disease of the Ministry of Education; Department of Neurobiology Capital Medical University ; Beijing , China
| | - Hui Yang
- a Center of Parkinson Disease Beijing Institute for Brain Disorders; Key Laboratory for Neurodegenerative Disease of the Ministry of Education; Department of Neurobiology Capital Medical University ; Beijing , China
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42
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Hwang J, Lee JA, Pallas DC. Leucine Carboxyl Methyltransferase 1 (LCMT-1) Methylates Protein Phosphatase 4 (PP4) and Protein Phosphatase 6 (PP6) and Differentially Regulates the Stable Formation of Different PP4 Holoenzymes. J Biol Chem 2016; 291:21008-21019. [PMID: 27507813 DOI: 10.1074/jbc.m116.739920] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Indexed: 11/06/2022] Open
Abstract
The protein phosphatase 2A (PP2A) subfamily of phosphatases, PP2A, PP4, and PP6, are multifunctional serine/threonine protein phosphatases involved in many cellular processes. Carboxyl methylation of the PP2A catalytic subunit (PP2Ac) C-terminal leucine is regulated by the opposing activities of leucine carboxyl methyltransferase 1 (LCMT-1) and protein phosphatase methylesterase 1 (PME-1) and regulates PP2A holoenzyme formation. The site of methylation on PP2Ac is conserved in the catalytic subunits of PP4 and PP6, and PP4 is also methylated on that site, but the identities of the methyltransferase enzyme for PP4 are not known. Whether PP6 is methylated is also not known. Here we use antibodies specific for the unmethylated phosphatases to show that PP6 is carboxyl-methylated and that LCMT-1 is the major methyltransferase for PP2A, PP4, and PP6 in mouse embryonic fibroblasts (MEFs). Analysis of PP2A and PP4 complexes by blue native polyacrylamide gel electrophoresis (BN-PAGE) indicates that PP4 holoenzyme complexes, like those of PP2A, are differentially regulated by LCMT-1, with the PP4 regulatory subunit 1 (PP4R1)-containing PP4 complex being the most dramatically affected by the LCMT-1 loss. MEFs derived from LCMT-1 knock-out mouse embryos have reduced levels of PP2A B regulatory subunit and PP4R1 relative to control MEFs, indicating that LCMT-1 is important for maintaining normal levels of these subunits. Finally, LCMT-1 homozygous knock-out MEFs exhibited hyperphosphorylation of HDAC3, a reported target of the methylation-dependent PP4R1-PP4c complex. Collectively, our data suggest that LCMT-1 coordinately regulates the carboxyl methylation of PP2A-related phosphatases and, consequently, their holoenzyme assembly and function.
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Affiliation(s)
- Juyeon Hwang
- From the Department of Biochemistry, Winship Cancer Center, and the Biochemistry, Cell, and Developmental Graduate Program, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Jocelyn A Lee
- From the Department of Biochemistry, Winship Cancer Center, and the Biochemistry, Cell, and Developmental Graduate Program, Emory University School of Medicine, Atlanta, Georgia 30322
| | - David C Pallas
- From the Department of Biochemistry, Winship Cancer Center, and the Biochemistry, Cell, and Developmental Graduate Program, Emory University School of Medicine, Atlanta, Georgia 30322
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Crystal structure of the human Tip41 orthologue, TIPRL, reveals a novel fold and a binding site for the PP2Ac C-terminus. Sci Rep 2016; 6:30813. [PMID: 27489114 PMCID: PMC4973239 DOI: 10.1038/srep30813] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Accepted: 07/08/2016] [Indexed: 11/25/2022] Open
Abstract
TOR signaling pathway regulator-like (TIPRL) is a regulatory protein which inhibits the catalytic subunits of Type 2A phosphatases. Several cellular contexts have been proposed for TIPRL, such as regulation of mTOR signaling, inhibition of apoptosis and biogenesis and recycling of PP2A, however, the underlying molecular mechanism is still poorly understood. We have solved the crystal structure of human TIPRL at 2.15 Å resolution. The structure is a novel fold organized around a central core of antiparallel beta-sheet, showing an N-terminal α/β region at one of its surfaces and a conserved cleft at the opposite surface. Inside this cleft, we found a peptide derived from TEV-mediated cleavage of the affinity tag. We show by mutagenesis, pulldown and hydrogen/deuterium exchange mass spectrometry that this peptide is a mimic for the conserved C-terminal tail of PP2A, an important region of the phosphatase which regulates holoenzyme assembly, and TIPRL preferentially binds the unmodified version of the PP2A-tail mimetic peptide DYFL compared to its tyrosine-phosphorylated version. A docking model of the TIPRL-PP2Ac complex suggests that TIPRL blocks the phosphatase’s active site, providing a structural framework for the function of TIPRL in PP2A inhibition.
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Grech G, Baldacchino S, Saliba C, Grixti MP, Gauci R, Petroni V, Fenech AG, Scerri C. Deregulation of the protein phosphatase 2A, PP2A in cancer: complexity and therapeutic options. Tumour Biol 2016; 37:11691-11700. [PMID: 27444275 DOI: 10.1007/s13277-016-5145-4] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Accepted: 07/11/2016] [Indexed: 01/26/2023] Open
Abstract
The complexity of the phosphatase, PP2A, is being unravelled and current research is increasingly providing information on the association of deregulated PP2A function with cancer initiation and progression. It has been reported that decreased activity of PP2A is a recurrent observation in many types of cancer, including colorectal and breast cancer (Baldacchino et al. EPMA J. 5:3, 2014; Cristobal et al. Mol Cancer Ther. 13:938-947, 2014). Since deregulation of PP2A and its regulatory subunits is a common event in cancer, PP2A is a potential target for therapy (Baldacchino et al. EPMA J. 5:3, 2014). In this review, the structural components of the PP2A complex are described, giving an in depth overview of the diversity of regulatory subunits. Regulation of the active PP2A trimeric complex, through phosphorylation and methylation, can be targeted using known compounds, to reactivate the complex. The endogenous inhibitors of the PP2A complex are highly deregulated in cancer, representing cases that are eligible to PP2A-activating drugs. Pharmacological opportunities to target low PP2A activity are available and preclinical data support the efficacy of these drugs, but clinical trials are lacking. We highlight the importance of PP2A deregulation in cancer and the current trends in targeting the phosphatase.
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Affiliation(s)
- Godfrey Grech
- Department of Pathology, Faculty of Medicine & Surgery, Medical School, University of Malta, Msida, MSD2090, Malta.
| | - Shawn Baldacchino
- Department of Pathology, Faculty of Medicine & Surgery, Medical School, University of Malta, Msida, MSD2090, Malta
| | - Christian Saliba
- Centre for Molecular Medicine and Biobanking, University of Malta, Msida, Malta
| | - Maria Pia Grixti
- Department of Pathology, Faculty of Medicine & Surgery, Medical School, University of Malta, Msida, MSD2090, Malta
| | - Robert Gauci
- Department of Pathology, Faculty of Medicine & Surgery, Medical School, University of Malta, Msida, MSD2090, Malta
| | - Vanessa Petroni
- Department of Anatomy, Faculty of Medicine & Surgery, University of Malta, Msida, Malta
| | - Anthony G Fenech
- Department of Clinical Pharmacology & Therapeutics, Faculty of Medicine & Surgery, University of Malta, Msida, Malta
| | - Christian Scerri
- Department of Physiology and Biochemistry, Faculty of Medicine & Surgery, University of Malta, Msida, Malta.,Molecular Genetics Clinic, Mater Dei Hospital, Msida, Malta
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Beier A, Teichert I, Krisp C, Wolters DA, Kück U. Catalytic Subunit 1 of Protein Phosphatase 2A Is a Subunit of the STRIPAK Complex and Governs Fungal Sexual Development. mBio 2016; 7:e00870-16. [PMID: 27329756 PMCID: PMC4916389 DOI: 10.1128/mbio.00870-16] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Accepted: 05/19/2016] [Indexed: 12/21/2022] Open
Abstract
UNLABELLED The generation of complex three-dimensional structures is a key developmental step for most eukaryotic organisms. The details of the molecular machinery controlling this step remain to be determined. An excellent model system to study this general process is the generation of three-dimensional fruiting bodies in filamentous fungi like Sordaria macrospora Fruiting body development is controlled by subunits of the highly conserved striatin-interacting phosphatase and kinase (STRIPAK) complex, which has been described in organisms ranging from yeasts to humans. The highly conserved heterotrimeric protein phosphatase PP2A is a subunit of STRIPAK. Here, catalytic subunit 1 of PP2A was functionally characterized. The Δpp2Ac1 strain is sterile, unable to undergo hyphal fusion, and devoid of ascogonial septation. Further, PP2Ac1, together with STRIPAK subunit PRO22, governs vegetative and stress-related growth. We revealed in vitro catalytic activity of wild-type PP2Ac1, and our in vivo analysis showed that inactive PP2Ac1 blocks the complementation of the sterile deletion strain. Tandem affinity purification, followed by mass spectrometry and yeast two-hybrid analysis, verified that PP2Ac1 is a subunit of STRIPAK. Further, these data indicate links between the STRIPAK complex and other developmental signaling pathways, implying the presence of a large interconnected signaling network that controls eukaryotic developmental processes. The insights gained in our study can be transferred to higher eukaryotes and will be important for understanding eukaryotic cellular development in general. IMPORTANCE The striatin-interacting phosphatase and kinase (STRIPAK) complex is highly conserved from yeasts to humans and is an important regulator of numerous eukaryotic developmental processes, such as cellular signaling and cell development. Although functional insights into the STRIPAK complex are accumulating, the detailed molecular mechanisms of single subunits are only partially understood. The first fungal STRIPAK was described in Sordaria macrospora, which is a well-established model organism used to study the formation of fungal fruiting bodies, three-dimensional organ-like structures. We analyzed STRIPAK subunit PP2Ac1, catalytic subunit 1 of protein phosphatase PP2A, to study the importance of the catalytic activity of this protein during sexual development. The results of our yeast two-hybrid analysis and tandem affinity purification, followed by mass spectrometry, indicate that PP2Ac1 activity connects STRIPAK with other signaling pathways and thus forms a large interconnected signaling network.
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Affiliation(s)
- Anna Beier
- Lehrstuhl für Allgemeine und Molekulare Botanik, Ruhr-Universität, Bochum, Germany
| | - Ines Teichert
- Lehrstuhl für Allgemeine und Molekulare Botanik, Ruhr-Universität, Bochum, Germany
| | - Christoph Krisp
- Lehrstuhl für Analytische Chemie, Ruhr-Universität, Bochum, Germany
| | - Dirk A Wolters
- Lehrstuhl für Analytische Chemie, Ruhr-Universität, Bochum, Germany
| | - Ulrich Kück
- Lehrstuhl für Allgemeine und Molekulare Botanik, Ruhr-Universität, Bochum, Germany
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PP2A methylation controls sensitivity and resistance to β-amyloid-induced cognitive and electrophysiological impairments. Proc Natl Acad Sci U S A 2016; 113:3347-52. [PMID: 26951658 DOI: 10.1073/pnas.1521018113] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Elevated levels of the β-amyloid peptide (Aβ) are thought to contribute to cognitive and behavioral impairments observed in Alzheimer's disease (AD). Protein phosphatase 2A (PP2A) participates in multiple molecular pathways implicated in AD, and its expression and activity are reduced in postmortem brains of AD patients. PP2A is regulated by protein methylation, and impaired PP2A methylation is thought to contribute to increased AD risk in hyperhomocysteinemic individuals. To examine further the link between PP2A and AD, we generated transgenic mice that overexpress the PP2A methylesterase, protein phosphatase methylesterase-1 (PME-1), or the PP2A methyltransferase, leucine carboxyl methyltransferase-1 (LCMT-1), and examined the sensitivity of these animals to behavioral and electrophysiological impairments caused by exogenous Aβ exposure. We found that PME-1 overexpression enhanced these impairments, whereas LCMT-1 overexpression protected against Aβ-induced impairments. Neither transgene affected Aβ production or the electrophysiological response to low concentrations of Aβ, suggesting that these manipulations selectively affect the pathological response to elevated Aβ levels. Together these data identify a molecular mechanism linking PP2A to the development of AD-related cognitive impairments that might be therapeutically exploited to target selectively the pathological effects caused by elevated Aβ levels in AD patients.
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Sangodkar J, Farrington C, McClinch K, Galsky MD, Kastrinsky DB, Narla G. All roads lead to PP2A: exploiting the therapeutic potential of this phosphatase. FEBS J 2016; 283:1004-24. [PMID: 26507691 PMCID: PMC4803620 DOI: 10.1111/febs.13573] [Citation(s) in RCA: 230] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Revised: 09/29/2015] [Accepted: 10/21/2015] [Indexed: 12/22/2022]
Abstract
Protein phosphatase 2A (PP2A) is a serine/threonine phosphatase involved in the regulation of many cellular processes. A confirmed tumor suppressor protein, PP2A is genetically altered or functionally inactivated in many cancers highlighting a need for its therapeutic reactivation. In this review we discuss recent literature on PP2A: the elucidation of its structure and the functions of its subunits, and the identification of molecular lesions and post-translational modifications leading to its dysregulation in cancer. A final section will discuss the proteins and small molecules that modulate PP2A and how these might be used to target dysregulated forms of PP2A to treat cancers and other diseases.
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Affiliation(s)
- Jaya Sangodkar
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mt. Sinai, New York, NY, USA
| | - Caroline Farrington
- Department of Medicine and Institute for Transformative Molecular Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Kimberly McClinch
- Department of Hematology and Medical Oncology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Matthew D. Galsky
- Department of Hematology and Medical Oncology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - David B. Kastrinsky
- Department of Structural and Chemical Biology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Goutham Narla
- Department of Medicine and Institute for Transformative Molecular Medicine, Case Western Reserve University, Cleveland, OH, USA
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Abstract
Protein phosphatase 2A (PP2A) plays a critical multi-faceted role in the regulation of the cell cycle. It is known to dephosphorylate over 300 substrates involved in the cell cycle, regulating almost all major pathways and cell cycle checkpoints. PP2A is involved in such diverse processes by the formation of structurally distinct families of holoenzymes, which are regulated spatially and temporally by specific regulators. Here, we review the involvement of PP2A in the regulation of three cell signaling pathways: wnt, mTOR and MAP kinase, as well as the G1→S transition, DNA synthesis and mitotic initiation. These processes are all crucial for proper cell survival and proliferation and are often deregulated in cancer and other diseases.
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Affiliation(s)
- Nathan Wlodarchak
- a McArdle Laboratory for Cancer Research, University of Wisconsin-Madison , Madison , WI , USA
| | - Yongna Xing
- a McArdle Laboratory for Cancer Research, University of Wisconsin-Madison , Madison , WI , USA
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Dudiki T, Kadunganattil S, Ferrara JK, Kline DW, Vijayaraghavan S. Changes in Carboxy Methylation and Tyrosine Phosphorylation of Protein Phosphatase PP2A Are Associated with Epididymal Sperm Maturation and Motility. PLoS One 2015; 10:e0141961. [PMID: 26569399 PMCID: PMC4646675 DOI: 10.1371/journal.pone.0141961] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Accepted: 10/15/2015] [Indexed: 01/21/2023] Open
Abstract
Mammalian sperm contain the serine/threonine phosphatases PP1γ2 and PP2A. The role of sperm PP1γ2 is relatively well studied. Here we confirm the presence of PP2A in sperm and show that it undergoes marked changes in methylation (leucine 309), tyrosine phosphorylation (tyrosine 307) and catalytic activity during epididymal sperm maturation. Spermatozoa isolated from proximal caput, distal caput and caudal regions of the epididymis contain equal immuno-reactive amounts of PP2A. Using demethyl sensitive antibodies we show that PP2A is methylated at its carboxy terminus in sperm from the distal caput and caudal regions but not in sperm from the proximal caput region of the epididymis. The methylation status of PP2A was confirmed by isolation of PP2A with microcystin agarose followed by alkali treatment, which causes hydrolysis of protein carboxy methyl esters. Tyrosine phosphorylation of sperm PP2A varied inversely with methylation. That is, PP2A was tyrosine phosphorylated when it was demethylated but not when methylated. PP2A demethylation and its reciprocal tyrosine phosphorylation were also affected by treatment of sperm with L-homocysteine and adenosine, which are known to elevate intracellular S-adenosylhomocysteine, a feedback inhibitor of methyltransferases. Catalytic activity of PP2A declined during epididymal sperm maturation. Inhibition of PP2A by okadaic acid or by incubation of caudal epididymal spermatozoa with L-homocysteine and adenosine resulted in increase of sperm motility parameters including percent motility, velocity, and lateral head amplitude. Demethylation or pharmacological inhibition of PP2A also leads to an increase in phosphorylation of glycogen synthase kinase-3 (GSK3). Our results show for the first time that changes in PP2A activity due to methylation and tyrosine phosphorylation occur in sperm and that these changes may play an important role in the regulation of sperm function.
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Affiliation(s)
- Tejasvi Dudiki
- Department of Biological Sciences, Kent State University, Kent, Ohio, United States of America
| | - Suraj Kadunganattil
- Department of Biological Sciences, Kent State University, Kent, Ohio, United States of America
| | - John K. Ferrara
- Department of Biological Sciences, Kent State University, Kent, Ohio, United States of America
| | - Douglas W. Kline
- Department of Biological Sciences, Kent State University, Kent, Ohio, United States of America
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Kurimchak A, Graña X. PP2A: more than a reset switch to activate pRB proteins during the cell cycle and in response to signaling cues. Cell Cycle 2015; 14:18-30. [PMID: 25483052 PMCID: PMC4612414 DOI: 10.4161/15384101.2014.985069] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
In their active hypophosphorylated state, members of the retinoblastoma family of pocket proteins negatively regulate cell cycle progression at least in part by repressing expression of E2F-dependent genes. Mitogen-dependent activation of G1 and G1/S Cyclin Dependent Kinases (CDKs) results in coordinated hyperphosphorylation and inactivation of these proteins, which no longer bind and repress E2Fs. S and G2/M CDKs maintain pocket protein hyperphosphorylated through the end of mitosis. The inactivating action of inducible CDKs is opposed by the Ser/Thr protein phosphatases PP2A and PP1. Various trimeric PP2A holoenzymes have been implicated in dephosphorylation of pocket proteins in response to specific cellular signals and stresses or as part of an equilibrium with CDKs throughout the cell cycle. PP1 has specifically been implicated in dephosphorylation of pRB in late mitosis and early G1. This review is particularly focused on the emerging role of PP2A as a major hub for integration of growth suppressor signals that require rapid inactivation of pocket proteins. Of note, activation of particular PP2A holoenzymes triggers differential activation of pocket proteins in the presence of active CDKs.
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Affiliation(s)
- Alison Kurimchak
- a Fels Institute for Cancer Research and Molecular Biology and Department of Biochemistry; Temple University School of Medicine ; Philadelphia , PA USA
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