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Guo M, Li Z, Gu M, Gu J, You Q, Wang L. Targeting phosphatases: From molecule design to clinical trials. Eur J Med Chem 2024; 264:116031. [PMID: 38101039 DOI: 10.1016/j.ejmech.2023.116031] [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: 10/23/2023] [Revised: 12/03/2023] [Accepted: 12/04/2023] [Indexed: 12/17/2023]
Abstract
Phosphatase is a kind of enzyme that can dephosphorylate target proteins, which can be divided into serine/threonine phosphatase and tyrosine phosphatase according to its mode of action. Current evidence showed multiple phosphatases were highly correlated with diseases including various cancers, demonstrating them as potential targets. However, currently, targeting phosphatases with small molecules faces many challenges, resulting in no drug approved. In this case, phosphatases are even regarded as "undruggable" targets for a long time. Recently, a variety of strategies have been adopted in the design of small molecule inhibitors targeting phosphatases, leading many of them to enter into the clinical trials. In this review, we classified these inhibitors into 4 types, including (1) molecular glues, (2) small molecules targeting catalytic sites, (3) allosteric inhibition, and (4) bifunctional molecules (proteolysis targeting chimeras, PROTACs). These molecules with diverse strategies prove the feasibility of phosphatases as drug targets. In addition, the combination therapy of phosphatase inhibitors with other drugs has also entered clinical trials, which suggests a broad prospect. Thus, targeting phosphatases with small molecules by different strategies is emerging as a promising way in the modulation of pathogenetic phosphorylation.
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Affiliation(s)
- Mochen Guo
- State Key Laboratory of Natural Medicines and Jiangsu Key Laboratory of Drug Design and Optimization, China Pharmaceutical University, Nanjing, 210009, China; Department of Medicinal Chemistry, School of Pharmacy, China Pharmaceutical University, Nanjing, 210009, China
| | - Zekun Li
- State Key Laboratory of Natural Medicines and Jiangsu Key Laboratory of Drug Design and Optimization, China Pharmaceutical University, Nanjing, 210009, China; Department of Medicinal Chemistry, School of Pharmacy, China Pharmaceutical University, Nanjing, 210009, China
| | - Mingxiao Gu
- State Key Laboratory of Natural Medicines and Jiangsu Key Laboratory of Drug Design and Optimization, China Pharmaceutical University, Nanjing, 210009, China; Department of Medicinal Chemistry, School of Pharmacy, China Pharmaceutical University, Nanjing, 210009, China
| | - Junrui Gu
- Department of Medicinal Chemistry, School of Pharmacy, China Pharmaceutical University, Nanjing, 210009, China
| | - Qidong You
- State Key Laboratory of Natural Medicines and Jiangsu Key Laboratory of Drug Design and Optimization, China Pharmaceutical University, Nanjing, 210009, China; Department of Medicinal Chemistry, School of Pharmacy, China Pharmaceutical University, Nanjing, 210009, China.
| | - Lei Wang
- State Key Laboratory of Natural Medicines and Jiangsu Key Laboratory of Drug Design and Optimization, China Pharmaceutical University, Nanjing, 210009, China; Department of Medicinal Chemistry, School of Pharmacy, China Pharmaceutical University, Nanjing, 210009, China.
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2
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Peris I, Romero-Murillo S, Vicente C, Narla G, Odero MD. Regulation and role of the PP2A-B56 holoenzyme family in cancer. Biochim Biophys Acta Rev Cancer 2023; 1878:188953. [PMID: 37437699 DOI: 10.1016/j.bbcan.2023.188953] [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: 05/14/2023] [Revised: 07/07/2023] [Accepted: 07/08/2023] [Indexed: 07/14/2023]
Abstract
Protein phosphatase 2A (PP2A) inactivation is common in cancer, leading to sustained activation of pro-survival and growth-promoting pathways. PP2A consists of a scaffolding A-subunit, a catalytic C-subunit, and a regulatory B-subunit. The functional complexity of PP2A holoenzymes arises mainly through the vast repertoire of regulatory B-subunits, which determine both their substrate specificity and their subcellular localization. Therefore, a major challenge for developing more effective therapeutic strategies for cancer is to identify the specific PP2A complexes to be targeted. Of note, the development of small molecules specifically directed at PP2A-B56α has opened new therapeutic avenues in both solid and hematological tumors. Here, we focus on the B56/PR61 family of PP2A regulatory subunits, which have a central role in directing PP2A tumor suppressor activity. We provide an overview of the mechanisms controlling the formation and regulation of these complexes, the pathways they control, and the mechanisms underlying their deregulation in cancer.
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Affiliation(s)
- Irene Peris
- Department of Biochemistry and Genetics, University of Navarra, Pamplona, Spain; Centro de Investigación Médica Aplicada (CIMA), University of Navarra, Pamplona, Spain; Instituto de Investigación Sanitaria de Navarra (IdiSNA), Pamplona, Spain.
| | - Silvia Romero-Murillo
- Department of Biochemistry and Genetics, University of Navarra, Pamplona, Spain; Centro de Investigación Médica Aplicada (CIMA), University of Navarra, Pamplona, Spain
| | - Carmen Vicente
- Centro de Investigación Médica Aplicada (CIMA), University of Navarra, Pamplona, Spain; Instituto de Investigación Sanitaria de Navarra (IdiSNA), Pamplona, Spain
| | - Goutham Narla
- Division of Genetic Medicine, Department of Internal Medicine, The University of Michigan Medical School, Ann Arbor, MI, USA
| | - Maria D Odero
- Department of Biochemistry and Genetics, University of Navarra, Pamplona, Spain; Centro de Investigación Médica Aplicada (CIMA), University of Navarra, Pamplona, Spain; Instituto de Investigación Sanitaria de Navarra (IdiSNA), Pamplona, Spain; CIBERONC, Instituto de Salud Carlos III, Madrid, Spain.
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3
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Wu J, Xu J, Naguib M, Bie B. Blockade of Type 2A Protein Phosphatase Signaling Attenuates Complement C1q-Mediated Microglial Phagocytosis of Glutamatergic Synapses Induced by Amyloid Fibrils. Mol Neurobiol 2023; 60:1527-1536. [PMID: 36515857 PMCID: PMC9910161 DOI: 10.1007/s12035-022-03161-2] [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: 01/19/2022] [Accepted: 12/06/2022] [Indexed: 12/15/2022]
Abstract
We previously reported the critical involvement of metabotropic GluR1 (mGluR1) signaling in complement C1q-dependent microglial phagocytosis of glutamatergic synapses in a rat model of Alzheimer's disease (AD) injected with amyloid fibrils. Here, we explored the role of type 2A protein phosphatase (type 2A PPase), a key enzyme downstream of mGluR1 signaling, in the pathogenesis of AD in rats. Significant local upregulation of PP2A expression was observed in the hippocampal CA1 after bilateral microinjection of amyloid-beta (Aβ1-40) fibrils. Amyloid fibrils induced remarkable dephosphorylation of pFMRP (fragile X mental retardation protein) and C1q upregulation in hippocampal glutamatergic synapses, which was ameliorated by microinjection of type 2A PPase inhibitor okadaic acid (OA). Microinjection of OA further attenuated the microglial phagocytosis of glutamatergic synapses, recovered the hippocampal glutamatergic transmission, and improved the performance in Morris water maze test. These findings demonstrated that dysfunction of type 2A PPase signaling contributed to complement C1q-dependent microglial phagocytosis of glutamatergic synapses and the cognitive impairments in the rat model of AD.
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Affiliation(s)
- Jiang Wu
- Anesthesiology Institute, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH, 44195, USA
| | - Jijun Xu
- Department of Pain Management, Anesthesiology Institute, 9500 Euclid Ave, Cleveland, OH, 44195, USA
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH, 44195, USA
| | - Mohamed Naguib
- Anesthesiology Institute, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH, 44195, USA
| | - Bihua Bie
- Anesthesiology Institute, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH, 44195, USA.
- Department of Biomedical Engineering, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH, 44195, USA.
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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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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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6
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Louzao MC, Vilariño N, Vale C, Costas C, Cao A, Raposo-Garcia S, Vieytes MR, Botana LM. Current Trends and New Challenges in Marine Phycotoxins. Mar Drugs 2022; 20:md20030198. [PMID: 35323497 PMCID: PMC8950113 DOI: 10.3390/md20030198] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 03/04/2022] [Accepted: 03/05/2022] [Indexed: 02/04/2023] Open
Abstract
Marine phycotoxins are a multiplicity of bioactive compounds which are produced by microalgae and bioaccumulate in the marine food web. Phycotoxins affect the ecosystem, pose a threat to human health, and have important economic effects on aquaculture and tourism worldwide. However, human health and food safety have been the primary concerns when considering the impacts of phycotoxins. Phycotoxins toxicity information, often used to set regulatory limits for these toxins in shellfish, lacks traceability of toxicity values highlighting the need for predefined toxicological criteria. Toxicity data together with adequate detection methods for monitoring procedures are crucial to protect human health. However, despite technological advances, there are still methodological uncertainties and high demand for universal phycotoxin detectors. This review focuses on these topics, including uncertainties of climate change, providing an overview of the current information as well as future perspectives.
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Affiliation(s)
- Maria Carmen Louzao
- Departamento de Farmacologia, Facultad de Veterinaria, Universidade de Santiago de Compostela, 27002 Lugo, Spain; (N.V.); (C.V.); (C.C.); (A.C.); (S.R.-G.)
- Correspondence: (M.C.L.); (L.M.B.)
| | - Natalia Vilariño
- Departamento de Farmacologia, Facultad de Veterinaria, Universidade de Santiago de Compostela, 27002 Lugo, Spain; (N.V.); (C.V.); (C.C.); (A.C.); (S.R.-G.)
| | - Carmen Vale
- Departamento de Farmacologia, Facultad de Veterinaria, Universidade de Santiago de Compostela, 27002 Lugo, Spain; (N.V.); (C.V.); (C.C.); (A.C.); (S.R.-G.)
| | - Celia Costas
- Departamento de Farmacologia, Facultad de Veterinaria, Universidade de Santiago de Compostela, 27002 Lugo, Spain; (N.V.); (C.V.); (C.C.); (A.C.); (S.R.-G.)
| | - Alejandro Cao
- Departamento de Farmacologia, Facultad de Veterinaria, Universidade de Santiago de Compostela, 27002 Lugo, Spain; (N.V.); (C.V.); (C.C.); (A.C.); (S.R.-G.)
| | - Sandra Raposo-Garcia
- Departamento de Farmacologia, Facultad de Veterinaria, Universidade de Santiago de Compostela, 27002 Lugo, Spain; (N.V.); (C.V.); (C.C.); (A.C.); (S.R.-G.)
| | - Mercedes R. Vieytes
- Departamento de Fisiologia, Facultad de Veterinaria, Universidade de Santiago de Compostela, 27002 Lugo, Spain;
| | - Luis M. Botana
- Departamento de Farmacologia, Facultad de Veterinaria, Universidade de Santiago de Compostela, 27002 Lugo, Spain; (N.V.); (C.V.); (C.C.); (A.C.); (S.R.-G.)
- Correspondence: (M.C.L.); (L.M.B.)
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7
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Zhu T, Jiang X, Xin H, Zheng X, Xue X, Chen JL, Qi B. GADD34-mediated dephosphorylation of eIF2α facilitates pseudorabies virus replication by maintaining de novo protein synthesis. Vet Res 2021; 52:148. [PMID: 34930429 PMCID: PMC8686791 DOI: 10.1186/s13567-021-01018-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Accepted: 11/22/2021] [Indexed: 11/10/2022] Open
Abstract
Viruses have evolved multiple strategies to manipulate their host's translational machinery for the synthesis of viral proteins. A common viral target is the alpha subunit of eukaryotic initiation factor 2 (eIF2α). In this study, we show that global protein synthesis was increased but the eIF2α phosphorylation level was markedly decreased in porcine kidney 15 (PK15) cells infected with pseudorabies virus (PRV), a swine herpesvirus. An increase in the eIF2α phosphorylation level by salubrinal treatment or transfection of constructs expressing wild-type eIF2α or an eIF2α phosphomimetic [eIF2α(S51D)] attenuated global protein synthesis and suppressed PRV replication. To explore the mechanism involved in the inhibition of eIF2α phosphorylation during PRV infection, we examined the phosphorylation status of protein kinase R-like endoplasmic reticulum kinase (PERK) and double-stranded RNA-dependent protein kinase R (PKR), two kinases that regulate eIF2α phosphorylation during infection with numerous viruses. We found that the level of neither phosphorylated (p)-PERK nor p-PKR was altered in PRV-infected cells or the lungs of infected mice. However, the expression of growth arrest and DNA damage-inducible protein 34 (GADD34), which promotes eIF2α dephosphorylation by recruiting protein phosphatase 1 (PP1), was significantly induced both in vivo and in vitro. Knockdown of GADD34 and inhibition of PP1 activity by okadaic acid treatment led to increased eIF2α phosphorylation but significantly suppressed global protein synthesis and inhibited PRV replication. Collectively, these results demonstrated that PRV induces GADD34 expression to promote eIF2α dephosphorylation, thereby maintaining de novo protein synthesis and facilitating viral replication.
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Affiliation(s)
- Ting Zhu
- Key Laboratory of Fujian-Taiwan Animal Pathogen Biology, College of Animal Science, Fujian Agriculture and Forestry University, Fuzhou, China.
| | - Xueli Jiang
- Key Laboratory of Fujian-Taiwan Animal Pathogen Biology, College of Animal Science, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Hangkuo Xin
- Key Laboratory of Fujian-Taiwan Animal Pathogen Biology, College of Animal Science, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Xiaohui Zheng
- Key Laboratory of Fujian-Taiwan Animal Pathogen Biology, College of Animal Science, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Xiaonuan Xue
- Key Laboratory of Fujian-Taiwan Animal Pathogen Biology, College of Animal Science, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Ji-Long Chen
- Key Laboratory of Fujian-Taiwan Animal Pathogen Biology, College of Animal Science, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Baomin Qi
- Key Laboratory of Fujian-Taiwan Animal Pathogen Biology, College of Animal Science, Fujian Agriculture and Forestry University, Fuzhou, China
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Zhang Q, Fan Z, Zhang L, You Q, Wang L. Strategies for Targeting Serine/Threonine Protein Phosphatases with Small Molecules in Cancer. J Med Chem 2021; 64:8916-8938. [PMID: 34156850 DOI: 10.1021/acs.jmedchem.1c00631] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Among numerous posttranslational regulation patterns, phosphorylation is reversibly controlled by the balance of kinases and phosphatases. The major form of cellular signaling involves the reversible phosphorylation of proteins on tyrosine, serine, or threonine residues. However, altered phosphorylation levels are found in diverse diseases, including cancer, making kinases and phosphatases ideal drug targets. In contrast to the success of prosperous kinase inhibitors, design of small molecules targeting phosphatase is struggling due to past bias and difficulty. This is especially true for serine/threonine phosphatases, one of the largest phosphatase families. From this perspective, we aim to provide insights into serine/threonine phosphatases and the small molecules targeting these proteins for drug development, especially in cancer. Through highlighting the modulation strategies, we aim to provide basic principles for the design of small molecules and future perspectives for the application of drugs targeting serine/threonine phosphatases.
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Affiliation(s)
- Qiuyue Zhang
- State Key Laboratory of Natural Medicines and Jiangsu Key Laboratory of Drug Design and Optimization, China Pharmaceutical University, Nanjing 210009, China.,Department of Medicinal Chemistry, School of Pharmacy, China Pharmaceutical University, Nanjing 210009, China
| | - Zhongjiao Fan
- State Key Laboratory of Natural Medicines and Jiangsu Key Laboratory of Drug Design and Optimization, China Pharmaceutical University, Nanjing 210009, China.,Department of Medicinal Chemistry, School of Pharmacy, China Pharmaceutical University, Nanjing 210009, China
| | - Lianshan Zhang
- Shanghai Hengrui Pharmaceutical Co., Ltd., Shanghai 200245, China
| | - Qidong You
- State Key Laboratory of Natural Medicines and Jiangsu Key Laboratory of Drug Design and Optimization, China Pharmaceutical University, Nanjing 210009, China.,Department of Medicinal Chemistry, School of Pharmacy, China Pharmaceutical University, Nanjing 210009, China
| | - Lei Wang
- State Key Laboratory of Natural Medicines and Jiangsu Key Laboratory of Drug Design and Optimization, China Pharmaceutical University, Nanjing 210009, China.,Department of Medicinal Chemistry, School of Pharmacy, China Pharmaceutical University, Nanjing 210009, China
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9
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Louzao MC, Costas C, Abal P, Suzuki T, Watanabe R, Vilariño N, Carrera C, Boente-Juncal A, Vale C, Vieytes MR, Botana LM. Serotonin involvement in okadaic acid-induced diarrhoea in vivo. Arch Toxicol 2021; 95:2797-2813. [PMID: 34148100 PMCID: PMC8298366 DOI: 10.1007/s00204-021-03095-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Accepted: 06/15/2021] [Indexed: 12/13/2022]
Abstract
The consumption of contaminated shellfish with okadaic acid (OA) group of toxins leads to diarrhoeic shellfish poisoning (DSP) characterized by a set of symptoms including nausea, vomiting and diarrhoea. These phycotoxins are Ser/Thr phosphatase inhibitors, which produce hyperphosphorylation in cellular proteins. However, this inhibition does not fully explain the symptomatology reported and other targets could be relevant to the toxicity. Previous studies have indicated a feasible involvement of the nervous system. We performed a set of in vivo approaches to elucidate whether neuropeptide Y (NPY), Peptide YY (PYY) or serotonin (5-HT) was implicated in the early OA-induced diarrhoea. Fasted Swiss female mice were administered NPY, PYY(3-36) or cyproheptadine intraperitoneal prior to oral OA treatment (250 µg/kg). A non-significant delay in diarrhoea onset was observed for NPY (107 µg/kg) and PYY(3-36) (1 mg/kg) pre-treatment. On the contrary, the serotonin antagonist cyproheptadine was able to block (10 mg/kg) or delay (0.1 and 1 mg/kg) diarrhoea onset suggesting a role of 5-HT. This is the first report of the possible involvement of serotonin in OA-induced poisoning.
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Affiliation(s)
- M Carmen Louzao
- Departamento de Farmacología, Facultad de Veterinaria, Universidade de Santiago de Compostela, 27002, Lugo, Spain.
| | - Celia Costas
- Departamento de Farmacología, Facultad de Veterinaria, Universidade de Santiago de Compostela, 27002, Lugo, Spain
| | - Paula Abal
- Departamento de Farmacología, Facultad de Veterinaria, Universidade de Santiago de Compostela, 27002, Lugo, Spain
| | - Toshiyuki Suzuki
- Fisheries Technology Institute, National Research and Development Agency, Japan Fisheries Research and Education Agency, Yokohama, 236-8648, Japan
| | - Ryuichi Watanabe
- Fisheries Technology Institute, National Research and Development Agency, Japan Fisheries Research and Education Agency, Yokohama, 236-8648, Japan
| | - Natalia Vilariño
- Departamento de Farmacología, Facultad de Veterinaria, Universidade de Santiago de Compostela, 27002, Lugo, Spain
| | - Cristina Carrera
- Departamento de Farmacología, Facultad de Veterinaria, Universidade de Santiago de Compostela, 27002, Lugo, Spain
| | - Andrea Boente-Juncal
- Departamento de Farmacología, Facultad de Veterinaria, Universidade de Santiago de Compostela, 27002, Lugo, Spain
| | - Carmen Vale
- Departamento de Farmacología, Facultad de Veterinaria, Universidade de Santiago de Compostela, 27002, Lugo, Spain
| | - Mercedes R Vieytes
- Departamento de Fisiología, Facultad de Veterinaria, Universidade de Santiago de Compostela, 27002, Lugo, Spain
| | - Luis M Botana
- Departamento de Farmacología, Facultad de Veterinaria, Universidade de Santiago de Compostela, 27002, Lugo, Spain
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10
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Regulation of cardiomyocyte DNA damage and cell death by the type 2A protein phosphatase regulatory protein alpha4. Sci Rep 2021; 11:6293. [PMID: 33737606 PMCID: PMC7973735 DOI: 10.1038/s41598-021-85616-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Accepted: 02/03/2021] [Indexed: 12/05/2022] Open
Abstract
The type 2A protein phosphatase regulatory protein alpha4 (α4) constitutes an anti-apoptotic protein in non-cardiac tissue, however it’s anti-apoptotic properties in the heart are poorly defined. To this end, we knocked down α4 protein expression (α4 KD) using siRNA in cultured H9c2 cardiomyocytes and confirmed the lack of DNA damage/cell death by TUNEL staining and MTT assay. However, α4 KD did increase the phosphorylation of p53 and ATM/ATR substrates, decreased the expression of poly ADP-ribose polymerase and associated fragments. Expression of anti-apoptotic proteins Bcl-2 and Bcl-xL was reduced, whereas expression of pro-apoptotic BAX protein did not change. Alpha4 KD reduced basal H2AX Ser139 phosphorylation, whereas adenoviral-mediated re-expression of α4 protein following α4 KD, restored basal H2AX phosphorylation at Ser139. The sensitivity of H9c2 cardiomyocytes to doxorubicin-induced DNA damage and cytotoxicity was augmented by α4 KD. Adenoviral-mediated overexpression of α4 protein in ARVM increased PP2AC expression and augmented H2AX Ser139 phosphorylation in response to doxorubicin. Furthermore, pressure overload-induced heart failure was associated with reduced α4 protein expression, increased ATM/ATR protein kinase activity, increased H2AX expression and Ser139 phosphorylation. Hence, this study describes the significance of altered α4 protein expression in the regulation of DNA damage, cardiomyocyte cell death and heart failure.
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11
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Papke CM, Smolen KA, Swingle MR, Cressey L, Heng RA, Toporsian M, Deng L, Hagen J, Shen Y, Chung WK, Kettenbach AN, Honkanen RE. A disorder-related variant (E420K) of a PP2A-regulatory subunit (PPP2R5D) causes constitutively active AKT-mTOR signaling and uncoordinated cell growth. J Biol Chem 2021; 296:100313. [PMID: 33482199 PMCID: PMC7952134 DOI: 10.1016/j.jbc.2021.100313] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 01/13/2021] [Accepted: 01/15/2021] [Indexed: 02/08/2023] Open
Abstract
Functional genomic approaches have facilitated the discovery of rare genetic disorders and improved efforts to decipher their underlying etiology. PPP2R5D-related disorder is an early childhood onset condition characterized by intellectual disability, hypotonia, autism-spectrum disorder, macrocephaly, and dysmorphic features. The disorder is caused by de novo single nucleotide changes in PPP2R5D, which generate heterozygous dominant missense variants. PPP2R5D is known to encode a B'-type (B'56δ) regulatory subunit of a PP2A-serine/threonine phosphatase. To help elucidate the molecular mechanisms altered in PPP2R5D-related disorder, we used a CRISPR-single-base editor to generate HEK-293 cells in which a single transition (c.1258G>A) was introduced into one allele, precisely recapitulating a clinically relevant E420K variant. Unbiased quantitative proteomic and phosphoproteomic analyses of endogenously expressed proteins revealed heterozygous-dominant changes in kinase/phosphatase signaling. These data combined with orthogonal validation studies revealed a previously unrecognized interaction of PPP2R5D with AKT in human cells, leading to constitutively active AKT-mTOR signaling, increased cell size, and uncoordinated cellular growth in E420K-variant cells. Rapamycin reduced cell size and dose-dependently reduced RPS6 phosphorylation in E420K-variant cells, suggesting that inhibition of mTOR1 can suppress both the observed RPS6 hyperphosphorylation and increased cell size. Together, our findings provide a deeper understanding of PPP2R5D and insight into how the E420K-variant alters signaling networks influenced by PPP2R5D. Our comprehensive approach, which combines precise genome editing, isobaric tandem mass tag labeling of peptides generated from endogenously expressed proteins, and concurrent liquid chromatography-mass spectrometry (LC-MS3), also provides a roadmap that can be used to rapidly explore the etiologies of additional genetic disorders.
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Affiliation(s)
- Cinta M Papke
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, Alabama, USA
| | - Kali A Smolen
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA; Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, USA
| | - Mark R Swingle
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, Alabama, USA
| | - Lauren Cressey
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA; Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, USA
| | - Richard A Heng
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, Alabama, USA
| | - Mourad Toporsian
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, Alabama, USA
| | - Liyong Deng
- Department of Pediatrics, Columbia University Irving Medical Center, New York, New York, USA
| | - Jacob Hagen
- Department of Pediatrics, Columbia University Irving Medical Center, New York, New York, USA
| | - Yufeng Shen
- Department of Systems Biology, Columbia University Irving Medical Center, New York, New York, USA
| | - Wendy K Chung
- Department of Pediatrics, Columbia University Irving Medical Center, New York, New York, USA; Herbert Irving Comprehensive Cancer Center, Columbia University Medical Center, New York, New York, USA; Department of Medicine, Columbia University Medical Center, New York, New York, USA
| | - Arminja N Kettenbach
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA; Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, USA.
| | - Richard E Honkanen
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, Alabama, USA.
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12
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Fujiwara N, Shibutani S, Sakai Y, Watanabe T, Kitabayashi I, Oshima H, Oshima M, Hoshida H, Akada R, Usui T, Ohama T, Sato K. Autophagy regulates levels of tumor suppressor enzyme protein phosphatase 6. Cancer Sci 2020; 111:4371-4380. [PMID: 32969571 PMCID: PMC7734157 DOI: 10.1111/cas.14662] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Revised: 09/12/2020] [Accepted: 09/16/2020] [Indexed: 12/20/2022] Open
Abstract
Protein phosphatase 6 (PP6) is an essential serine/threonine protein phosphatase that acts as an important tumor suppressor. However, increased protein levels of PP6 have been observed in some cancer types, and they correlate with poor prognosis in glioblastoma. This raises a question about how PP6 protein levels are regulated in normal and transformed cells. In this study, we show that PP6 protein levels increase in response to pharmacologic and genetic inhibition of autophagy. PP6 associates with autophagic adaptor protein p62/SQSTM1 and is degraded in a p62-dependent manner. Accordingly, protein levels of PP6 and p62 fluctuate in concert under different physiological and pathophysiological conditions. Our data reveal that PP6 is regulated by p62-dependent autophagy and suggest that accumulation of PP6 protein in tumor tissues is caused at least partially by deficiency in autophagy.
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Affiliation(s)
- Nobuyuki Fujiwara
- Laboratory of Veterinary Pharmacology, Yamaguchi University, Yamaguchi, Japan.,Laboratory of Drug Discovery and Pharmacology, Faculty of Veterinary Medicine, Okayama University of Science, Ehime, Japan
| | - Shusaku Shibutani
- Laboratory of Veterinary Hygiene, Yamaguchi University, Yamaguchi, Japan
| | - Yusuke Sakai
- Laboratory of Veterinary Pathology, Yamaguchi University, Yamaguchi, Japan
| | - Toshio Watanabe
- Department of Biological Science, Graduate School of Humanities and Sciences, Nara Women's University, Nara, Japan
| | - Issay Kitabayashi
- Division of Hematological Malignancy, National Cancer Center Research Institute, Tokyo, Japan
| | - Hiroko Oshima
- Division of Genetics, Cancer Research Institute, Kanazawa University, Kanazawa, Japan
| | - Masanobu Oshima
- Division of Genetics, Cancer Research Institute, Kanazawa University, Kanazawa, Japan
| | - Hisashi Hoshida
- Department of Applied Chemistry, Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi, Japan
| | - Rinji Akada
- Department of Applied Chemistry, Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi, Japan
| | - Tatsuya Usui
- Laboratory of Veterinary Pharmacology, Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Tokyo, Japan
| | - Takashi Ohama
- Laboratory of Veterinary Pharmacology, Yamaguchi University, Yamaguchi, Japan
| | - Koichi Sato
- Laboratory of Veterinary Pharmacology, Yamaguchi University, Yamaguchi, Japan
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13
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The Inhibition of Serine/Threonine Protein Phosphatase Type 5 Mediates Cantharidin Toxicity to Control Periplaneta americana (L.). INSECTS 2020; 11:insects11100682. [PMID: 33050059 PMCID: PMC7600710 DOI: 10.3390/insects11100682] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 10/02/2020] [Accepted: 10/05/2020] [Indexed: 12/20/2022]
Abstract
The American cockroach, Periplaneta americana (L.), is a notorious urban pest. It has developed insecticidal resistance to commonly used insecticides. Cantharidin (CTD) is a defensive toxin derived from blister beetles. It has been verified to have insecticidal toxicity in a range of pests. In this study, we determined the ingestion toxicity of CTD and norcantharidin (NCTD) to P. americana to test whether they had the potential to be effective against P. americana. Bioassays revealed that CTD produces toxicity against P. americana. The median lethal concentration (LC50) value of CTD was 50.92 μg/mL, while NCTD displayed nearly no toxicity against P. americana. The inhibition assays of serine/threonine protein phosphatases (PSPs) in P. americana indicated that CTD and NCTD could inhibit PSPs. The value of the half maximal inhibitory concentration (IC50) of CTD was 7.21 ± 0.94 μM, whereas that of NCTD was higher, at 31.65 ± 3.87 μM. Furthermore, the inhibition effect of CTD on the serine/threonine protein phosphatase type 5 of P. americana (PaPP5) was superior to that of NCTD. Specifically, the IC50 of CTD reached 0.39 ± 0.04 μM, while the IC50 of NCTD was 1.87 ± 0.23 μM. This study paves the way for insect-derived agents (CTD) to be applied toward controlling P. americana and contributes to the development of novel insecticides based on PP5 as a target.
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14
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Biales AD, Bencic DC, Flick RW, Delacruz A, Gordon DA, Huang W. Global transcriptomic profiling of microcystin-LR or -RR treated hepatocytes (HepaRG). Toxicon X 2020; 8:100060. [PMID: 33235993 PMCID: PMC7670210 DOI: 10.1016/j.toxcx.2020.100060] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 09/24/2020] [Accepted: 09/27/2020] [Indexed: 12/20/2022] Open
Abstract
The canonical mode of action (MOA) of microcystins (MC) is the inhibition of protein phosphatases, but complete characterization of toxicity pathways is lacking. The existence of over 200 MC congeners complicates risk estimates worldwide. This work employed RNA-seq to provide an unbiased and comprehensive characterization of cellular targets and impacted cellular processes of hepatocytes exposed to either MC-LR or MC-RR congeners. The human hepatocyte cell line, HepaRG, was treated with three concentrations of MC-LR or -RR for 2 h. Significant reduction in cell survival was observed in LR1000 and LR100 treatments whereas no acute toxicity was observed in any MR-RR treatment. RNA-seq was performed on all treatments of MC-LR and -RR. Differentially expressed genes and pathways associated with oxidative and endoplasmic reticulum (ER) stress, and the unfolded protein response (UPR) were highly enriched by both congeners as were inflammatory pathways. Genes associated with both apoptotic and inflammatory pathways were enriched in LR1000. We present a model of MC toxicity that immediately causes oxidative stress and leads to ER stress and the activation of the UPR. Differential activation of the three arms of the UPR and the kinetics of JNK activation ultimately determine whether cell survival or apoptosis is favored. Extracellular exosomes were enrichment of by both congeners, suggesting a previously unidentified mechanism for MC-dependent extracellular signaling. The complement system was enriched only in MC-RR treatments, suggesting congener-specific differences in cellular effects. This study provided an unbiased snapshot of the early systemic hepatocyte response to MC-LR and MC-RR congeners and may explain differences in toxicity among MC congeners. Microcystin-LR and microcystin-RR have similar transcriptional responses. Genes associated with oxidative stress and the unfolded protein response were enriched by congeners. Genes associated with extracellular exosomes were enriched, suggesting a potential new mechanism for cell signaling. Complement associated genes were strongly enriched only by microcystin-RR. Identified a potential molecular mechanism underlying the cellular fate of hepatocyte.
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Affiliation(s)
- Adam D Biales
- U.S. Environmental Protection Agency, Office of Research and Development, Cincinnati, OH, 45268, USA
| | - David C Bencic
- U.S. Environmental Protection Agency, Office of Research and Development, Cincinnati, OH, 45268, USA
| | - Robert W Flick
- U.S. Environmental Protection Agency, Office of Research and Development, Cincinnati, OH, 45268, USA
| | - Armah Delacruz
- U.S. Environmental Protection Agency, Office of Research and Development, Cincinnati, OH, 45268, USA
| | - Denise A Gordon
- U.S. Environmental Protection Agency, Office of Research and Development, Cincinnati, OH, 45268, USA
| | - Weichun Huang
- U.S. Environmental Protection Agency, Office of Research and Development, Research Triangle Park, NC, 27709, USA
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15
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Protein kinase CK2 phosphorylation of SAPS3 subunit increases PP6 phosphatase activity with Aurora A kinase. Biochem J 2020; 477:431-444. [PMID: 31904830 DOI: 10.1042/bcj20190740] [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: 10/07/2019] [Revised: 12/04/2019] [Accepted: 01/06/2020] [Indexed: 12/11/2022]
Abstract
Protein Ser/Thr phosphatase-6 (PP6) regulates pathways for activation of NF-kB, YAP1 and Aurora A kinase (AURKA). PP6 is a heterotrimer comprised of a catalytic subunit, one of three different SAPS subunits and one of three different ankyrin-repeat ANKRD subunits. Here, we show FLAG-PP6C expressed in cells preferentially binds endogenous SAPS3, and the complex is active with the chemical substrate DiFMUP. SAPS3 has multiple acidic sequence motifs recognized by protein kinase CK2 (CK2) and SAPS3 is phosphorylated by purified CK2, without affecting its associated PP6 phosphatase activity. However, HA3-SAPS3-PP6 phosphatase activity using pT288 AURKA as substrate is significantly increased by phosphorylation with CK2. The substitution of Ala in nine putative phosphorylation sites in SAPS3 was required to prevent CK2 activation of the phosphatase. Different CK2 chemical inhibitors equally increased phosphorylation of endogenous AURKA in living cells, consistent with reduction in PP6 activity. CRISPR/Cas9 deletion or siRNA knockdown of SAPS3 resulted in highly activated endogenous AURKA, and a high proportion of cells with abnormal nuclei. Activation of PP6 by CK2 can form a feedback loop with bistable changes in substrates.
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16
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Kleinberger T. Biology of the adenovirus E4orf4 protein: from virus infection to cancer cell death. FEBS Lett 2019; 594:1891-1917. [DOI: 10.1002/1873-3468.13704] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 11/24/2019] [Accepted: 11/25/2019] [Indexed: 12/14/2022]
Affiliation(s)
- Tamar Kleinberger
- Department of Molecular Microbiology the Rappaport Faculty of Medicine Technion –Israel Institute of Technology Haifa Israel
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17
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Bouaïcha N, Miles CO, Beach DG, Labidi Z, Djabri A, Benayache NY, Nguyen-Quang T. Structural Diversity, Characterization and Toxicology of Microcystins. Toxins (Basel) 2019; 11:E714. [PMID: 31817927 PMCID: PMC6950048 DOI: 10.3390/toxins11120714] [Citation(s) in RCA: 206] [Impact Index Per Article: 41.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 12/02/2019] [Accepted: 12/04/2019] [Indexed: 11/22/2022] Open
Abstract
Hepatotoxic microcystins (MCs) are the most widespread class of cyanotoxins and the one that has most often been implicated in cyanobacterial toxicosis. One of the main challenges in studying and monitoring MCs is the great structural diversity within the class. The full chemical structure of the first MC was elucidated in the early 1980s and since then, the number of reported structural analogues has grown steadily and continues to do so, thanks largely to advances in analytical methodology. The structures of some of these analogues have been definitively elucidated after chemical isolation using a combination of techniques including nuclear magnetic resonance, amino acid analysis, and tandem mass spectrometry (MS/MS). Others have only been tentatively identified using liquid chromatography-MS/MS without chemical isolation. An understanding of the structural diversity of MCs, the genetic and environmental controls for this diversity and the impact of structure on toxicity are all essential to the ongoing study of MCs across several scientific disciplines. However, because of the diversity of MCs and the range of approaches that have been taken for characterizing them, comprehensive information on the state of knowledge in each of these areas can be challenging to gather. We have conducted an in-depth review of the literature surrounding the identification and toxicity of known MCs and present here a concise review of these topics. At present, at least 279 MCs have been reported and are tabulated here. Among these, about 20% (55 of 279) appear to be the result of chemical or biochemical transformations of MCs that can occur in the environment or during sample handling and extraction of cyanobacteria, including oxidation products, methyl esters, or post-biosynthetic metabolites. The toxicity of many MCs has also been studied using a range of different approaches and a great deal of variability can be observed between reported toxicities, even for the same congener. This review will help clarify the current state of knowledge on the structural diversity of MCs as a class and the impacts of structure on toxicity, as well as to identify gaps in knowledge that should be addressed in future research.
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Affiliation(s)
- Noureddine Bouaïcha
- Écologie, Systématique et Évolution, Univ. Paris-Sud, CNRS, AgroParisTech, Université Paris-Saclay, 91405 Orsay, France; (A.D.); (N.Y.B.)
| | - Christopher O. Miles
- Biotoxin Metrology, National Research Council Canada, 1411 Oxford St, Halifax, NS B3H 3Z1, Canada; (C.O.M.); (D.G.B.)
| | - Daniel G. Beach
- Biotoxin Metrology, National Research Council Canada, 1411 Oxford St, Halifax, NS B3H 3Z1, Canada; (C.O.M.); (D.G.B.)
| | - Zineb Labidi
- Laboratoire Biodiversité et Pollution des Écosystèmes, Faculté des Sciences de la Nature et de la Vie, Université Chadli Bendjedid d’El Taref, 36000 El Taref, Algeria;
| | - Amina Djabri
- Écologie, Systématique et Évolution, Univ. Paris-Sud, CNRS, AgroParisTech, Université Paris-Saclay, 91405 Orsay, France; (A.D.); (N.Y.B.)
- Laboratoire Biodiversité et Pollution des Écosystèmes, Faculté des Sciences de la Nature et de la Vie, Université Chadli Bendjedid d’El Taref, 36000 El Taref, Algeria;
| | - Naila Yasmine Benayache
- Écologie, Systématique et Évolution, Univ. Paris-Sud, CNRS, AgroParisTech, Université Paris-Saclay, 91405 Orsay, France; (A.D.); (N.Y.B.)
| | - Tri Nguyen-Quang
- Biofluids and Biosystems Modeling (BBML), Faculty of Agriculture, Dalhousie University, 39 Cox Road, Truro, B2N 5E3 Nova Scotia, Canada;
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18
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Dziegielewski J, Bońkowska MA, Poniecka EA, Heo J, Du K, Crittenden RB, Bender TP, Brautigan DL, Larner JM. Deletion of the SAPS1 subunit of protein phosphatase 6 in mice increases radiosensitivity and impairs the cellular DNA damage response. DNA Repair (Amst) 2019; 85:102737. [PMID: 31751917 DOI: 10.1016/j.dnarep.2019.102737] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 09/17/2019] [Accepted: 10/15/2019] [Indexed: 12/24/2022]
Abstract
Cellular responses to DNA damage include activation of DNA-dependent protein kinase (DNA-PK) through, among others, the serine/threonine protein phosphatase 6 (PP6). We previously showed that recognition of DNA-PKcs is mediated by the SAPS1 PP6 regulatory subunit. Here, we report and characterize a SAPS1 null mouse and investigate the effects of deletion on DNA damage signaling and repair. Strikingly, neither SAPS1-null animals nor cells derived from them show gross defects, unless subjected to DNA damage by radiation or chemical agents. The overall survival of SAPS1-null animals following whole body irradiation is significantly shortened as compared to wild-type mice, and the clonogenic survival of null cells subjected to ionizing radiation is reduced. The dephosphorylation of DNA damage/repair markers, such as γH2AX, p53 and Kap1, is diminished in SAPS1-null cells as compared to wild-type controls. Our results demonstrate that loss of SAPS1 confers sensitivity to DNA damage and confirms previously reported cellular phenotypes of SAPS1 knock-down in human glioma cells. The results support a role for PP6 regulatory subunit SAPS1 in DNA damage responses, and offer a novel target for sensitization to enhance current tumor therapies, with a potential for limited deleterious side effects.
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Affiliation(s)
- Jaroslaw Dziegielewski
- Center for Cell Signaling, University of Virginia School of Medicine, Charlottesville, VA 22908, USA; Department of Radiation Oncology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Magdalena A Bońkowska
- Center for Cell Signaling, University of Virginia School of Medicine, Charlottesville, VA 22908, USA; Department of Microbiology, Immunology and Cancer Biology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Ewa A Poniecka
- Center for Cell Signaling, University of Virginia School of Medicine, Charlottesville, VA 22908, USA; Department of Microbiology, Immunology and Cancer Biology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Jinho Heo
- Center for Cell Signaling, University of Virginia School of Medicine, Charlottesville, VA 22908, USA; Department of Microbiology, Immunology and Cancer Biology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Kangping Du
- Center for Cell Signaling, University of Virginia School of Medicine, Charlottesville, VA 22908, USA; Department of Radiation Oncology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Rowena B Crittenden
- Department of Microbiology, Immunology and Cancer Biology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA; Beirne B. Carter Center for Immunology Research, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Timothy P Bender
- Department of Microbiology, Immunology and Cancer Biology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA; Beirne B. Carter Center for Immunology Research, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - David L Brautigan
- Center for Cell Signaling, University of Virginia School of Medicine, Charlottesville, VA 22908, USA; Department of Microbiology, Immunology and Cancer Biology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - James M Larner
- Center for Cell Signaling, University of Virginia School of Medicine, Charlottesville, VA 22908, USA; Department of Radiation Oncology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA.
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19
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Zhu X, Sun L, He Y, Wei H, Hong M, Liu F, Liu Q, Cao Y, Cui L. Plasmodium berghei serine/threonine protein phosphatase PP5 plays a critical role in male gamete fertility. Int J Parasitol 2019; 49:685-695. [DOI: 10.1016/j.ijpara.2019.03.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2019] [Accepted: 03/18/2019] [Indexed: 02/06/2023]
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20
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Javadpour P, Dargahi L, Ahmadiani A, Ghasemi R. To be or not to be: PP2A as a dual player in CNS functions, its role in neurodegeneration, and its interaction with brain insulin signaling. Cell Mol Life Sci 2019; 76:2277-2297. [PMID: 30874837 PMCID: PMC11105459 DOI: 10.1007/s00018-019-03063-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2018] [Revised: 02/16/2019] [Accepted: 03/07/2019] [Indexed: 12/26/2022]
Abstract
Accumulating evidence has reached the consensus that the balance of phosphorylation state of signaling molecules is a pivotal point in the regulation of cell signaling. Therefore, characterizing elements (kinases-phosphatases) in the phosphorylation balance are at great importance. However, the role of phosphatase enzymes is less investigated than kinase enzymes. PP2A is a member of serine/threonine protein phosphatase that its imbalance has been reported in neurodegenerative diseases. Therefore, we reviewed the superfamily of phosphatases and more specifically PP2A, its regulation, and physiological functions participate in CNS. Thereafter, we discussed the latest findings about PP2A dysregulation in Alzheimer and Parkinson diseases and possible interplay between this phosphatase and insulin signaling pathways. Finally, activating/inhibitory modulators for PP2A activity as well as experimental methods for PP2A study have been reviewed.
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Affiliation(s)
- Pegah Javadpour
- Department of Physiology, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Leila Dargahi
- Neurobiology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Abolhassan Ahmadiani
- Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Rasoul Ghasemi
- Department of Physiology, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
- Neurophysiology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
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21
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Jamsheer K M, Jindal S, Laxmi A. Evolution of TOR-SnRK dynamics in green plants and its integration with phytohormone signaling networks. JOURNAL OF EXPERIMENTAL BOTANY 2019; 70:2239-2259. [PMID: 30870564 DOI: 10.1093/jxb/erz107] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 02/26/2019] [Indexed: 05/07/2023]
Abstract
The target of rapamycin (TOR)-sucrose non-fermenting 1 (SNF1)-related protein kinase 1 (SnRK1) signaling is an ancient regulatory mechanism that originated in eukaryotes to regulate nutrient-dependent growth. Although the TOR-SnRK1 signaling cascade shows highly conserved functions among eukaryotes, studies in the past two decades have identified many important plant-specific innovations in this pathway. Plants also possess SnRK2 and SnRK3 kinases, which originated from the ancient SnRK1-related kinases and have specialized roles in controlling growth, stress responses and nutrient homeostasis in plants. Recently, an integrative picture has started to emerge in which different SnRKs and TOR kinase are highly interconnected to control nutrient and stress responses of plants. Further, these kinases are intimately involved with phytohormone signaling networks that originated at different stages of plant evolution. In this review, we highlight the evolution and divergence of TOR-SnRK signaling components in plants and their communication with each other as well as phytohormone signaling to fine-tune growth and stress responses in plants.
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Affiliation(s)
- Muhammed Jamsheer K
- Amity Food & Agriculture Foundation, Amity University Uttar Pradesh, Noida, India
| | - Sunita Jindal
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, India
| | - Ashverya Laxmi
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, India
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22
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Swingle MR, Honkanen RE. Inhibitors of Serine/Threonine Protein Phosphatases: Biochemical and Structural Studies Provide Insight for Further Development. Curr Med Chem 2019; 26:2634-2660. [PMID: 29737249 PMCID: PMC10013172 DOI: 10.2174/0929867325666180508095242] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 02/05/2018] [Accepted: 03/29/2018] [Indexed: 11/22/2022]
Abstract
BACKGROUND The reversible phosphorylation of proteins regulates many key functions in eukaryotic cells. Phosphorylation is catalyzed by protein kinases, with the majority of phosphorylation occurring on side chains of serine and threonine residues. The phosphomonoesters generated by protein kinases are hydrolyzed by protein phosphatases. In the absence of a phosphatase, the half-time for the hydrolysis of alkyl phosphate dianions at 25º C is over 1 trillion years; knon ~2 x 10-20 sec-1. Therefore, ser/thr phosphatases are critical for processes controlled by reversible phosphorylation. METHODS This review is based on the literature searched in available databases. We compare the catalytic mechanism of PPP-family phosphatases (PPPases) and the interactions of inhibitors that target these enzymes. RESULTS PPPases are metal-dependent hydrolases that enhance the rate of hydrolysis ([kcat/kM]/knon ) by a factor of ~1021, placing them among the most powerful known catalysts on earth. Biochemical and structural studies indicate that the remarkable catalytic proficiencies of PPPases are achieved by 10 conserved amino acids, DXH(X)~26DXXDR(X)~20- 26NH(X)~50H(X)~25-45R(X)~30-40H. Six act as metal-coordinating residues. Four position and orient the substrate phosphate. Together, two metal ions and the 10 catalytic residues position the phosphoryl group and an activated bridging water/hydroxide nucleophile for an inline attack upon the substrate phosphorous atom. The PPPases are conserved among species, and many structurally diverse natural toxins co-evolved to target these enzymes. CONCLUSION Although the catalytic site is conserved, opportunities for the development of selective inhibitors of this important group of metalloenzymes exist.
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Affiliation(s)
- Mark R Swingle
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile AL 36688, United States
| | - Richard E Honkanen
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile AL 36688, United States
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23
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Ohama T. The multiple functions of protein phosphatase 6. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1866:74-82. [DOI: 10.1016/j.bbamcr.2018.07.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 06/21/2018] [Accepted: 07/18/2018] [Indexed: 12/26/2022]
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24
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Microcystins: Synthesis and structure–activity relationship studies toward PP1 and PP2A. Bioorg Med Chem 2018; 26:1118-1126. [DOI: 10.1016/j.bmc.2017.08.040] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Revised: 08/19/2017] [Accepted: 08/23/2017] [Indexed: 11/19/2022]
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25
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Cui G, Li Y, Ding K, Hao S, Wang J, Zhang Z. Attribution of Bax and mitochondrial permeability transition pore on cantharidin-induced apoptosis of Sf9 cells. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2017; 142:91-101. [PMID: 29107253 DOI: 10.1016/j.pestbp.2017.01.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 01/11/2017] [Accepted: 01/14/2017] [Indexed: 06/07/2023]
Abstract
To investigate the insecticidal mechanism of cantharidin, a promising biological pesticide substance from blister beetle, on Sf9 cells, a cultured cell line derived from fall armyworm, Spodoptera frugiperda, we preliminary studied the attribution of Bax channel and mitochondrial permeability transition pore on cantharidin-induced mitochondrial apoptosis signal pathway. Changes in cell morphology, activity of mitochondrial dehydrogenases, release of cytochrome C and mitochondrial transmembrane potential were detected when the two channels were blocked by specific inhibitors, Bax channel blocker and cyclosporin A. Results showed that cantharidin-induced apoptotic features, including changes in the cell morphology, release of cytochrome C and decrease in mitochondrial transmembrane potential could be significantly inhibited by Bax channel blocker, while cyclosporin A accelerated the downward trend of mitochondrial dehydrogenases activity and caused a decrease of Ca2+ in mitochondria. In summary, Bax might be necessary but not exclusively for the apoptosis induced by cantharidin and the attribution of these channels seems to be more complexity.
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Affiliation(s)
- Gaofeng Cui
- College of Plant Science and Technology, Beijing University of Agriculture, Beijing 102206, China
| | - Yuansheng Li
- College of Plant Science and Technology, Beijing University of Agriculture, Beijing 102206, China
| | - Kai Ding
- College of Plant Science and Technology, Beijing University of Agriculture, Beijing 102206, China
| | - Shaodong Hao
- College of Plant Science and Technology, Beijing University of Agriculture, Beijing 102206, China
| | - Jinzhong Wang
- College of Plant Science and Technology, Beijing University of Agriculture, Beijing 102206, China
| | - Zhiyong Zhang
- College of Plant Science and Technology, Beijing University of Agriculture, Beijing 102206, China.
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26
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Creighton MT, Kolton A, Kataya ARA, Maple-Grødem J, Averkina IO, Heidari B, Lillo C. Methylation of protein phosphatase 2A-Influence of regulators and environmental stress factors. PLANT, CELL & ENVIRONMENT 2017; 40:2347-2358. [PMID: 28741704 DOI: 10.1111/pce.13038] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 07/08/2017] [Accepted: 07/11/2017] [Indexed: 05/13/2023]
Abstract
Protein phosphatase 2A catalytic subunit (PP2A-C) has a terminal leucine subjected to methylation, a regulatory mechanism conserved from yeast to mammals and plants. Two enzymes, LCMT1 and PME1, methylate and demethylate PP2A-C, respectively. The physiological importance of these posttranslational modifications is still enigmatic. We investigated these processes in Arabidopsis thaliana by mutant phenotyping, by global expression analysis, and by monitoring methylation status of PP2A-C under different environmental conditions. The lcmt1 mutant, possessing essentially only unmethylated PP2A-C, had less dense rosettes, and earlier flowering than wild type (WT). The pme1 mutant, with 30% reduction in unmethylated PP2A-C, was phenotypically comparable with WT. Approximately 200 overlapping genes were twofold upregulated, and 200 overlapping genes were twofold downregulated in both lcmt1 and pme1 relative to WT. Differences between the 2 mutants were also striking; 97 genes were twofold upregulated in pme1 compared with lcmt1, indicating that PME1 acts as a negative regulator for these genes. Analysis of enriched GO terms revealed categories of both abiotic and biotic stress genes. Furthermore, methylation status of PP2A-C was influenced by environmental stress, especially by hypoxia and salt stress, which led to increased levels of unmethylated PP2A-C, and highlights the importance of PP2A-C methylation/demethylation in environmental responses.
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Affiliation(s)
- Maria T Creighton
- Centre for Organelle Research, Faculty of Science and Technology, University of Stavanger, Stavanger, N-4036, Norway
| | - Anna Kolton
- Centre for Organelle Research, Faculty of Science and Technology, University of Stavanger, Stavanger, N-4036, Norway
- Faculty of Biotechnology and Horticulture, University of Agriculture in Krakow, Kraków, 31-425 Kraków, Poland
| | - Amr R A Kataya
- Centre for Organelle Research, Faculty of Science and Technology, University of Stavanger, Stavanger, N-4036, Norway
| | - Jodi Maple-Grødem
- Centre for Organelle Research, Faculty of Science and Technology, University of Stavanger, Stavanger, N-4036, Norway
| | - Irina O Averkina
- Centre for Organelle Research, Faculty of Science and Technology, University of Stavanger, Stavanger, N-4036, Norway
| | - Behzad Heidari
- Centre for Organelle Research, Faculty of Science and Technology, University of Stavanger, Stavanger, N-4036, Norway
| | - Cathrine Lillo
- Centre for Organelle Research, Faculty of Science and Technology, University of Stavanger, Stavanger, N-4036, Norway
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27
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Functions of protein phosphatase-6 in NF-κB signaling and in lymphocytes. Biochem Soc Trans 2017; 45:693-701. [PMID: 28620030 PMCID: PMC5473023 DOI: 10.1042/bst20160169] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Revised: 03/01/2017] [Accepted: 03/08/2017] [Indexed: 12/17/2022]
Abstract
Protein phosphatase-6 (PP6) is a member of the PPP family of Ser/Thr phosphatases involved in intracellular signaling. PP6 is conserved among all eukaryotes, and genetics in model organisms indicates it has non-redundant functions relative to other PPP phosphatases. PP6 functions in association with conserved SAPS subunits and, in vertebrate species, forms heterotrimers with Ankrd subunits. Multiple studies have demonstrated how PP6 exerts negative control at different steps of nuclear factor kappaB signaling. Expression of PP6 catalytic subunit and the PPP6R1 subunit is especially high in hematopoietic cells and lymphoid tissues. Recent efforts at conditionally knocking out genes for PP6c or PP6R1 (SAPS1) have revealed distinctive effects on development of and signaling in lymphocytes.
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28
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Eleftheriadou O, Boguslavskyi A, Longman MR, Cowan J, Francois A, Heads RJ, Wadzinski BE, Ryan A, Shattock MJ, Snabaitis AK. Expression and regulation of type 2A protein phosphatases and alpha4 signalling in cardiac health and hypertrophy. Basic Res Cardiol 2017; 112:37. [PMID: 28526910 PMCID: PMC5438423 DOI: 10.1007/s00395-017-0625-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Accepted: 05/02/2017] [Indexed: 01/25/2023]
Abstract
Cardiac physiology and hypertrophy are regulated by the phosphorylation status of many proteins, which is partly controlled by a poorly defined type 2A protein phosphatase-alpha4 intracellular signalling axis. Quantitative PCR analysis revealed that mRNA levels of the type 2A catalytic subunits were differentially expressed in H9c2 cardiomyocytes (PP2ACβ > PP2ACα > PP4C > PP6C), NRVM (PP2ACβ > PP2ACα = PP4C = PP6C), and adult rat ventricular myocytes (PP2ACα > PP2ACβ > PP6C > PP4C). Western analysis confirmed that all type 2A catalytic subunits were expressed in H9c2 cardiomyocytes; however, PP4C protein was absent in adult myocytes and only detectable following 26S proteasome inhibition. Short-term knockdown of alpha4 protein expression attenuated expression of all type 2A catalytic subunits. Pressure overload-induced left ventricular (LV) hypertrophy was associated with an increase in both PP2AC and alpha4 protein expression. Although PP6C expression was unchanged, expression of PP6C regulatory subunits (1) Sit4-associated protein 1 (SAP1) and (2) ankyrin repeat domain (ANKRD) 28 and 44 proteins was elevated, whereas SAP2 expression was reduced in hypertrophied LV tissue. Co-immunoprecipitation studies demonstrated that the interaction between alpha4 and PP2AC or PP6C subunits was either unchanged or reduced in hypertrophied LV tissue, respectively. Phosphorylation status of phospholemman (Ser63 and Ser68) was significantly increased by knockdown of PP2ACα, PP2ACβ, or PP4C protein expression. DNA damage assessed by histone H2A.X phosphorylation (γH2A.X) in hypertrophied tissue remained unchanged. However, exposure of cardiomyocytes to H2O2 increased levels of γH2A.X which was unaffected by knockdown of PP6C expression, but was abolished by the short-term knockdown of alpha4 expression. This study illustrates the significance and altered activity of the type 2A protein phosphatase-alpha4 complex in healthy and hypertrophied myocardium.
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Affiliation(s)
- Olga Eleftheriadou
- School of Life Sciences, Pharmacy and Chemistry, Faculty of Science Engineering and Computing, Kingston University, Penrhyn Road, Kingston-upon-Thames, Surrey, KT1 2EE, UK
| | - Andrii Boguslavskyi
- Cardiovascular Division, King's College London British Heart Foundation Centre, The Rayne Institute, St Thomas' Hospital, London, SE1 7EH, UK
| | - Michael R Longman
- School of Life Sciences, Pharmacy and Chemistry, Faculty of Science Engineering and Computing, Kingston University, Penrhyn Road, Kingston-upon-Thames, Surrey, KT1 2EE, UK
| | - Jonathan Cowan
- School of Life Sciences, Pharmacy and Chemistry, Faculty of Science Engineering and Computing, Kingston University, Penrhyn Road, Kingston-upon-Thames, Surrey, KT1 2EE, UK
| | - Asvi Francois
- Cardiovascular Division, King's College London British Heart Foundation Centre, The Rayne Institute, St Thomas' Hospital, London, SE1 7EH, UK
| | - Richard J Heads
- Cardiovascular Division, King's College London British Heart Foundation Centre, The Rayne Institute, St Thomas' Hospital, London, SE1 7EH, UK
| | - Brian E Wadzinski
- Department of Pharmacology, Vanderbilt University, Nashville, TN, USA
| | - Ali Ryan
- School of Life Sciences, Pharmacy and Chemistry, Faculty of Science Engineering and Computing, Kingston University, Penrhyn Road, Kingston-upon-Thames, Surrey, KT1 2EE, UK
| | - Michael J Shattock
- Cardiovascular Division, King's College London British Heart Foundation Centre, The Rayne Institute, St Thomas' Hospital, London, SE1 7EH, UK
| | - Andrew K Snabaitis
- School of Life Sciences, Pharmacy and Chemistry, Faculty of Science Engineering and Computing, Kingston University, Penrhyn Road, Kingston-upon-Thames, Surrey, KT1 2EE, UK.
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29
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Filter JJ, Williams BC, Eto M, Shalloway D, Goldberg ML. Unfair competition governs the interaction of pCPI-17 with myosin phosphatase (PP1-MYPT1). eLife 2017; 6. [PMID: 28387646 PMCID: PMC5441869 DOI: 10.7554/elife.24665] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2016] [Accepted: 03/31/2017] [Indexed: 11/30/2022] Open
Abstract
The small phosphoprotein pCPI-17 inhibits myosin light-chain phosphatase (MLCP). Current models postulate that during muscle relaxation, phosphatases other than MLCP dephosphorylate and inactivate pCPI-17 to restore MLCP activity. We show here that such hypotheses are insufficient to account for the observed rapidity of pCPI-17 inactivation in mammalian smooth muscles. Instead, MLCP itself is the critical enzyme for pCPI-17 dephosphorylation. We call the mutual sequestration mechanism through which pCPI-17 and MLCP interact inhibition by unfair competition: MLCP protects pCPI-17 from other phosphatases, while pCPI-17 blocks other substrates from MLCP’s active site. MLCP dephosphorylates pCPI-17 at a slow rate that is, nonetheless, both sufficient and necessary to explain the speed of pCPI-17 dephosphorylation and the consequent MLCP activation during muscle relaxation. DOI:http://dx.doi.org/10.7554/eLife.24665.001
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Affiliation(s)
- Joshua J Filter
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| | - Byron C Williams
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| | - Masumi Eto
- Department of Molecular Physiology and Biophysics, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, United States
| | - David Shalloway
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| | - Michael L Goldberg
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
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30
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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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31
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Dubuissez M, Loison I, Paget S, Vorng H, Ait-Yahia S, Rohr O, Tsicopoulos A, Leprince D. Protein Kinase C-Mediated Phosphorylation of BCL11B at Serine 2 Negatively Regulates Its Interaction with NuRD Complexes during CD4+ T-Cell Activation. Mol Cell Biol 2016; 36:1881-98. [PMID: 27161321 PMCID: PMC4911745 DOI: 10.1128/mcb.00062-16] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Revised: 02/16/2016] [Accepted: 05/03/2016] [Indexed: 12/17/2022] Open
Abstract
The transcription factor BCL11B/CTIP2 is a major regulatory protein implicated in various aspects of development, function and survival of T cells. Mitogen-activated protein kinase (MAPK)-mediated phosphorylation and SUMOylation modulate BCL11B transcriptional activity, switching it from a repressor in naive murine thymocytes to a transcriptional activator in activated thymocytes. Here, we show that BCL11B interacts via its conserved N-terminal MSRRKQ motif with endogenous MTA1 and MTA3 proteins to recruit various NuRD complexes. Furthermore, we demonstrate that protein kinase C (PKC)-mediated phosphorylation of BCL11B Ser2 does not significantly impact BCL11B SUMOylation but negatively regulates NuRD recruitment by dampening the interaction with MTA1 or MTA3 (MTA1/3) and RbAp46 proteins. We detected increased phosphorylation of BCL11B Ser2 upon in vivo activation of transformed and primary human CD4(+) T cells. We show that following activation of CD4(+) T cells, BCL11B still binds to IL-2 and Id2 promoters but activates their transcription by recruiting P300 instead of MTA1. Prolonged stimulation results in the direct transcriptional repression of BCL11B by KLF4. Our results unveil Ser2 phosphorylation as a new BCL11B posttranslational modification linking PKC signaling pathway to T-cell receptor (TCR) activation and define a simple model for the functional switch of BCL11B from a transcriptional repressor to an activator during TCR activation of human CD4(+) T cells.
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Affiliation(s)
- Marion Dubuissez
- Université Lille, CNRS, Institut Pasteur de Lille, UMR 8161, Mechanisms of Tumorigenesis and Targeted Therapies (M3T), Lille, France
| | - Ingrid Loison
- Université Lille, CNRS, Institut Pasteur de Lille, UMR 8161, Mechanisms of Tumorigenesis and Targeted Therapies (M3T), Lille, France
| | - Sonia Paget
- Université Lille, CNRS, Institut Pasteur de Lille, UMR 8161, Mechanisms of Tumorigenesis and Targeted Therapies (M3T), Lille, France
| | - Han Vorng
- Université Lille, CNRS, INSERM, CHU Lille, Institut Pasteur de Lille, U1019, UMR8204, Center for Infection and Immunity of Lille (CIIL), Lille, France
| | - Saliha Ait-Yahia
- Université Lille, CNRS, INSERM, CHU Lille, Institut Pasteur de Lille, U1019, UMR8204, Center for Infection and Immunity of Lille (CIIL), Lille, France
| | - Olivier Rohr
- University of Strasbourg, IUT Louis Pasteur, EA7292, Dynamic of Host Pathogen Interactions, Institute of Parasitology and Tropical Pathology, Strasbourg, France Institut Universitaire de France, Paris, France
| | - Anne Tsicopoulos
- Université Lille, CNRS, INSERM, CHU Lille, Institut Pasteur de Lille, U1019, UMR8204, Center for Infection and Immunity of Lille (CIIL), Lille, France
| | - Dominique Leprince
- Université Lille, CNRS, Institut Pasteur de Lille, UMR 8161, Mechanisms of Tumorigenesis and Targeted Therapies (M3T), Lille, France
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32
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Chattopadhyay D, Swingle MR, Salter EA, Wood E, D'Arcy B, Zivanov C, Abney K, Musiyenko A, Rusin SF, Kettenbach A, Yet L, Schroeder CE, Golden JE, Dunham WH, Gingras AC, Banerjee S, Forbes D, Wierzbicki A, Honkanen RE. Crystal structures and mutagenesis of PPP-family ser/thr protein phosphatases elucidate the selectivity of cantharidin and novel norcantharidin-based inhibitors of PP5C. Biochem Pharmacol 2016; 109:14-26. [PMID: 27002182 DOI: 10.1016/j.bcp.2016.03.011] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Accepted: 03/15/2016] [Indexed: 12/24/2022]
Abstract
Cantharidin is a natural toxin and an active constituent in a traditional Chinese medicine used to treat tumors. Cantharidin acts as a semi-selective inhibitor of PPP-family ser/thr protein phosphatases. Despite sharing a common catalytic mechanism and marked structural similarity with PP1C, PP2AC and PP5C, human PP4C was found to be insensitive to the inhibitory activity of cantharidin. To explore the molecular basis for this selectivity, we synthesized and tested novel C5/C6-derivatives designed from quantum-based modeling of the interactions revealed in the co-crystal structures of PP5C in complex with cantharidin. Structure-activity relationship studies and analysis of high-resolution (1.25Å) PP5C-inhibitor co-crystal structures reveal close contacts between the inhibitor bridgehead oxygen and both a catalytic metal ion and a non-catalytic phenylalanine residue, the latter of which is substituted by tryptophan in PP4C. Quantum chemistry calculations predicted that steric clashes with the bulkier tryptophan side chain in PP4C would force all cantharidin-based inhibitors into an unfavorable binding mode, disrupting the strong coordination of active site metal ions observed in the PP5C co-crystal structures, thereby rendering PP4C insensitive to the inhibitors. This prediction was confirmed by inhibition studies employing native human PP4C. Mutation of PP5C (F446W) and PP1C (F257W), to mimic the PP4C active site, resulted in markedly suppressed sensitivity to cantharidin. These observations provide insight into the structural basis for the natural selectivity of cantharidin and provide an avenue for PP4C deselection. The novel crystal structures also provide insight into interactions that provide increased selectivity of the C5/C6 modifications for PP5C versus other PPP-family phosphatases.
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Affiliation(s)
| | - Mark R Swingle
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, AL 36688, USA
| | - Edward A Salter
- Department of Chemistry, University of South Alabama, Mobile, AL 36688, USA
| | - Eric Wood
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, AL 36688, USA; Department of Chemistry, University of South Alabama, Mobile, AL 36688, USA
| | - Brandon D'Arcy
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, AL 36688, USA
| | - Catherine Zivanov
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, AL 36688, USA; Department of Chemistry, University of South Alabama, Mobile, AL 36688, USA
| | - Kevin Abney
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, AL 36688, USA
| | - Alla Musiyenko
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, AL 36688, USA
| | - Scott F Rusin
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Lebanon, NH 03756, USA
| | - Arminja Kettenbach
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Lebanon, NH 03756, USA; Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth, Lebanon, NH 03756, USA
| | - Larry Yet
- Department of Chemistry, University of South Alabama, Mobile, AL 36688, USA
| | - Chad E Schroeder
- Department of Medicinal Chemistry, University of Kansas Specialized Chemistry Center, Lawrence, KS 66047, USA
| | - Jennifer E Golden
- Department of Medicinal Chemistry, University of Kansas Specialized Chemistry Center, Lawrence, KS 66047, USA
| | - Wade H Dunham
- Centre for Systems Biology, Lunenfeld-Tanenbaum Research Institute at Mount Sinai Hospital, Toronto, Ontario M5G 1X5, Canada; Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Anne-Claude Gingras
- Centre for Systems Biology, Lunenfeld-Tanenbaum Research Institute at Mount Sinai Hospital, Toronto, Ontario M5G 1X5, Canada; Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Surajit Banerjee
- Northeastern Collaborative Access Team (NE-CAT) Cornell University, Lemont, IL, USA
| | - David Forbes
- Department of Chemistry, University of South Alabama, Mobile, AL 36688, USA
| | - Andrzej Wierzbicki
- Department of Chemistry, University of South Alabama, Mobile, AL 36688, USA
| | - Richard E Honkanen
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, AL 36688, USA.
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33
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Rusin SF, Schlosser KA, Adamo ME, Kettenbach AN. Quantitative phosphoproteomics reveals new roles for the protein phosphatase PP6 in mitotic cells. Sci Signal 2015; 8:rs12. [PMID: 26462736 DOI: 10.1126/scisignal.aab3138] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Protein phosphorylation is an important regulatory mechanism controlling mitotic progression. Protein phosphatase 6 (PP6) is an essential enzyme with conserved roles in chromosome segregation and spindle assembly from yeast to humans. We applied a baculovirus-mediated gene silencing approach to deplete HeLa cells of the catalytic subunit of PP6 (PP6c) and analyzed changes in the phosphoproteome and proteome in mitotic cells by quantitative mass spectrometry-based proteomics. We identified 408 phosphopeptides on 272 proteins that increased and 298 phosphopeptides on 220 proteins that decreased in phosphorylation upon PP6c depletion in mitotic cells. Motif analysis of the phosphorylated sites combined with bioinformatics pathway analysis revealed previously unknown PP6c-dependent regulatory pathways. Biochemical assays demonstrated that PP6c opposed casein kinase 2-dependent phosphorylation of the condensin I subunit NCAP-G, and cellular analysis showed that depletion of PP6c resulted in defects in chromosome condensation and segregation in anaphase, consistent with dysregulation of condensin I function in the absence of PP6 activity.
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Affiliation(s)
- Scott F Rusin
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, NH 03755, USA
| | - Kate A Schlosser
- Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth, Lebanon, NH 03756, USA
| | - Mark E Adamo
- Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth, Lebanon, NH 03756, USA
| | - Arminja N Kettenbach
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, NH 03755, USA. Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth, Lebanon, NH 03756, USA.
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34
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Boylan JM, Salomon AR, Tantravahi U, Gruppuso PA. Adaptation of HepG2 cells to a steady-state reduction in the content of protein phosphatase 6 (PP6) catalytic subunit. Exp Cell Res 2015; 335:224-37. [PMID: 25999147 DOI: 10.1016/j.yexcr.2015.05.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Revised: 05/06/2015] [Accepted: 05/08/2015] [Indexed: 11/27/2022]
Abstract
Protein phosphatase 6 (PP6) is a ubiquitous Ser/Thr phosphatase involved in an array of cellular processes. To assess the potential of PP6 as a therapeutic target in liver disorders, we attenuated expression of the PP6 catalytic subunit in HepG2 cells using lentiviral-transduced shRNA. Two PP6 knock-down (PP6KD) cell lines (90% reduction of PP6-C protein content) were studied in depth. Both proliferated at a rate similar to control cells. However, flow cytometry indicated G2/M cell cycle arrest that was accounted for by a shift of the cells from a diploid to tetraploid state. PP6KD cells did not show an increase in apoptosis, nor did they exhibit reduced viability in the presence of bleomycin or taxol. Gene expression analysis by microarray showed attenuated anti-inflammatory signaling. Genes associated with DNA replication were downregulated. Mass spectrometry-based phosphoproteomic analysis yielded 80 phosphopeptides representing 56 proteins that were significantly affected by a stable reduction in PP6-C. Proteins involved in DNA replication, DNA damage repair and pre-mRNA splicing were overrepresented among these. PP6KD cells showed intact mTOR signaling. Our studies demonstrated involvement of PP6 in a diverse set of biological pathways and an adaptive response that may limit the effectiveness of targeting PP6 in liver disorders.
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Affiliation(s)
- Joan M Boylan
- Department of Pediatrics, Brown University and Rhode Island Hospital, Providence, RI, USA
| | - Arthur R Salomon
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI, USA; Department of Chemistry, Brown University, Providence, RI, USA
| | - Umadevi Tantravahi
- Division of Genetics, Department of Pathology, Brown University and Women and Infants Hospital, Providence, RI, USA
| | - Philip A Gruppuso
- Department of Pediatrics, Brown University and Rhode Island Hospital, Providence, RI, USA; Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI, USA.
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35
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Kleinberger T. Mechanisms of cancer cell killing by the adenovirus E4orf4 protein. Viruses 2015; 7:2334-57. [PMID: 25961489 PMCID: PMC4452909 DOI: 10.3390/v7052334] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2015] [Revised: 04/23/2015] [Accepted: 04/30/2015] [Indexed: 12/24/2022] Open
Abstract
During adenovirus (Ad) replication the Ad E4orf4 protein regulates progression from the early to the late phase of infection. However, when E4orf4 is expressed alone outside the context of the virus it induces a non-canonical mode of programmed cell death, which feeds into known cell death pathways such as apoptosis or necrosis, depending on the cell line tested. E4orf4-induced cell death has many interesting and unique features including a higher susceptibility of cancer cells to E4orf4-induced cell killing compared with normal cells, caspase-independence, a high degree of evolutionary conservation of the signaling pathways, a link to perturbations of the cell cycle, and involvement of two distinct cell death programs, in the nucleus and in the cytoplasm. Several E4orf4-interacting proteins including its major partners, protein phosphatase 2A (PP2A) and Src family kinases, contribute to induction of cell death. The various features of E4orf4-induced cell killing as well as studies to decipher the underlying mechanisms are described here. Many explanations for the cancer specificity of E4orf4-induced cell death have been proposed, but a full understanding of the reasons for the different susceptibility of cancer and normal cells to killing by E4orf4 will require a more detailed analysis of the complex E4orf4 signaling network. An improved understanding of the mechanisms involved in this unique mode of programmed cell death may aid in design of novel E4orf4-based cancer therapeutics.
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Affiliation(s)
- Tamar Kleinberger
- Department of Microbiology, Faculty of Medicine, Technion-Israel Institute of Technology, 1 Efron St., Bat Galim, Haifa 31096, Israel.
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36
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Wengrod J, Wang D, Weiss S, Zhong H, Osman I, Gardner LB. Phosphorylation of eIF2α triggered by mTORC1 inhibition and PP6C activation is required for autophagy and is aberrant in PP6C-mutated melanoma. Sci Signal 2015; 8:ra27. [PMID: 25759478 DOI: 10.1126/scisignal.aaa0899] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Amino acid deprivation promotes the inhibition of the kinase complex mTORC1 (mammalian target of rapamycin complex 1) and activation of the kinase GCN2 (general control nonrepressed 2). Signaling pathways downstream of both kinases have been thought to independently induce autophagy. We showed that these two amino acid-sensing systems are linked. We showed that pharmacological inhibition of mTORC1 led to activation of GCN2 and phosphorylation of the eukaryotic initiation factor 2α (eIF2α) in a mechanism dependent on the catalytic subunit of protein phosphatase 6 (PP6C). Autophagy induced by pharmacological inhibition of mTORC1 required PP6C, GCN2, and eIF2α phosphorylation. Although some of the PP6C mutants found in melanoma did not form a strong complex with PP6 regulatory subunits and were rapidly degraded, these mutants paradoxically stabilized PP6C encoded by the wild-type allele and increased eIF2α phosphorylation. Furthermore, these PP6C mutations were associated with increased autophagy in vitro and in human melanoma samples. Thus, these data showed that GCN2 activation and phosphorylation of eIF2α in response to mTORC1 inhibition are necessary for autophagy. Additionally, we described a role for PP6C in this process and provided a mechanism for PP6C mutations associated with melanoma.
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Affiliation(s)
- Jordan Wengrod
- Department of Medicine, New York University School of Medicine, New York, NY 10016, USA
| | - Ding Wang
- Department of Medicine, New York University School of Medicine, New York, NY 10016, USA
| | - Sarah Weiss
- Department of Medicine, New York University School of Medicine, New York, NY 10016, USA
| | - Hua Zhong
- Department of Population Health, New York University School of Medicine, New York, NY 10016, USA
| | - Iman Osman
- Department of Dermatology, New York University School of Medicine, New York, NY 10016, USA. NYU Perlmutter Cancer Center, New York University School of Medicine, New York, NY 10016, USA
| | - Lawrence B Gardner
- Department of Medicine, New York University School of Medicine, New York, NY 10016, USA. NYU Perlmutter Cancer Center, New York University School of Medicine, New York, NY 10016, USA. Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY 10016, USA.
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Ramaswamy K, Spitzer B, Kentsis A. Therapeutic Re-Activation of Protein Phosphatase 2A in Acute Myeloid Leukemia. Front Oncol 2015; 5:16. [PMID: 25699237 PMCID: PMC4313608 DOI: 10.3389/fonc.2015.00016] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2014] [Accepted: 01/13/2015] [Indexed: 11/13/2022] Open
Abstract
Protein phosphatase 2A (PP2A) is a serine/threonine phosphatase that is required for normal cell growth and development. PP2A is a potent tumor suppressor, which is inactivated in cancer cells as a result of genetic deletions and mutations. In myeloid leukemias, genes encoding PP2A subunits are generally intact. Instead, PP2A is functionally inhibited by post-translational modifications of its catalytic C subunit, and interactions with negative regulators by its regulatory B and scaffold A subunits. Here, we review the molecular mechanisms of genetic and functional inactivation of PP2A in human cancers, with a particular focus on human acute myeloid leukemias (AML). By analyzing expression of genes encoding PP2A subunits using transcriptome sequencing, we find that PP2A dysregulation in AML is characterized by silencing and overexpression of distinct A scaffold and B regulatory subunits, respectively. We review the mechanisms of functional PP2A activation by drugs such as fingolimod, forskolin, OP449, and perphenazine. This analysis yields two non-mutually exclusive mechanisms for therapeutic PP2A re-activation: (i) allosteric activation of the phosphatase activity, and (ii) stabilization of active holo-enzyme assembly and displacement of negative regulatory factors from A and B subunits. Future studies should allow the development of specific and potent pharmacologic activators of PP2A, and definition of susceptible disease subsets based on specific mechanisms of PP2A dysregulation.
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Affiliation(s)
- Kavitha Ramaswamy
- Molecular Pharmacology and Chemistry Program, Department of Pediatrics, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, Weill Medical College of Cornell University , New York, NY , USA
| | - Barbara Spitzer
- Molecular Pharmacology and Chemistry Program, Department of Pediatrics, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, Weill Medical College of Cornell University , New York, NY , USA
| | - Alex Kentsis
- Molecular Pharmacology and Chemistry Program, Department of Pediatrics, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, Weill Medical College of Cornell University , New York, NY , USA
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Ahn CS, Ahn HK, Pai HS. Overexpression of the PP2A regulatory subunit Tap46 leads to enhanced plant growth through stimulation of the TOR signalling pathway. JOURNAL OF EXPERIMENTAL BOTANY 2015; 66:827-40. [PMID: 25399018 PMCID: PMC4321543 DOI: 10.1093/jxb/eru438] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Tap46, a regulatory subunit of protein phosphatase 2A (PP2A), plays an essential role in plant growth and development through a functional link with the Target of Rapamycin (TOR) signalling pathway. Here, we have characterized the molecular mechanisms behind a gain-of-function phenotype of Tap46 and its relationship with TOR to gain further insights into Tap46 function in plants. Constitutive overexpression of Tap46 in Arabidopsis resulted in overall growth stimulation with enlarged organs, such as leaves and siliques. Kinematic analysis of leaf growth revealed that increased cell size was mainly responsible for the leaf enlargement. Tap46 overexpression also enhanced seed size and viability under accelerated ageing conditions. Enhanced plant growth was also observed in dexamethasone (DEX)-inducible Tap46 overexpression Arabidopsis lines, accompanied by increased cellular activities of nitrate-assimilating enzymes. DEX-induced Tap46 overexpression and Tap46 RNAi resulted in increased and decreased phosphorylation of S6 kinase (S6K), respectively, which is a sensitive indicator of endogenous TOR activity, and Tap46 interacted with S6K in planta based on bimolecular fluorescence complementation and co-immunoprecipitation. Furthermore, inactivation of TOR by estradiol-inducible RNAi or rapamycin treatment decreased Tap46 protein levels, but increased PP2A catalytic subunit levels. Real-time quantitative PCR analysis revealed that Tap46 overexpression induced transcriptional modulation of genes involved in nitrogen metabolism, ribosome biogenesis, and lignin biosynthesis. These findings suggest that Tap46 modulates plant growth as a positive effector of the TOR signalling pathway and Tap46/PP2Ac protein abundance is regulated by TOR activity.
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Affiliation(s)
- Chang Sook Ahn
- Department of Systems Biology, Yonsei University, Seoul 120-749, Korea
| | - Hee-Kyung Ahn
- Department of Systems Biology, Yonsei University, Seoul 120-749, Korea
| | - Hyun-Sook Pai
- Department of Systems Biology, Yonsei University, Seoul 120-749, Korea
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Kajihara R, Sakamoto H, Tanabe K, Takemoto K, Tasaki M, Ando Y, Inui S. Protein phosphatase 6 controls BCR-induced apoptosis of WEHI-231 cells by regulating ubiquitination of Bcl-xL. THE JOURNAL OF IMMUNOLOGY 2014; 192:5720-9. [PMID: 24808369 DOI: 10.4049/jimmunol.1302643] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Crosslinking BCR in the immature B cell line WEHI-231 causes apoptosis. We found that Bcl-xL was degraded by polyubiquitination upon BCR crosslinking and in this study explored the mechanism that controls the degradation of Bcl-xL. Ser(62) of Bcl-xL was phosphorylated by JNK to trigger polyubiquitination, and this was opposed by serine/threonine protein phosphatase 6 (PP6) that physically associated with Bcl-xL. We show BCR crosslinking decreased PP6 activity to allow Ser(62) phosphorylation of Bcl-xL. CD40 crosslinking rescues BCR-induced apoptosis, and we found PP6 associated with CD40 and PP6 activation in response to CD40. Our data suggest that PP6 activity is regulated to control apoptosis by modulating Ser(62) phosphorylation of Bcl-xL, which results in its polyubiquitination and degradation.
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Affiliation(s)
- Ryutaro Kajihara
- Department of Immunology and Hematology, Faculty of Life Sciences, Graduate School of Health Sciences, Kumamoto University, Kumamoto 862-0976, Japan; and
| | - Hitomi Sakamoto
- Department of Immunology and Hematology, Faculty of Life Sciences, Graduate School of Health Sciences, Kumamoto University, Kumamoto 862-0976, Japan; and
| | - Kano Tanabe
- Department of Immunology and Hematology, Faculty of Life Sciences, Graduate School of Health Sciences, Kumamoto University, Kumamoto 862-0976, Japan; and
| | - Kazuki Takemoto
- Department of Immunology and Hematology, Faculty of Life Sciences, Graduate School of Health Sciences, Kumamoto University, Kumamoto 862-0976, Japan; and
| | - Masayoshi Tasaki
- Department of Neurology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto 862-0976, Japan
| | - Yukio Ando
- Department of Neurology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto 862-0976, Japan
| | - Seiji Inui
- Department of Immunology and Hematology, Faculty of Life Sciences, Graduate School of Health Sciences, Kumamoto University, Kumamoto 862-0976, Japan; and
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Kleinberger T. Induction of cancer-specific cell death by the adenovirus E4orf4 protein. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 818:61-97. [PMID: 25001532 DOI: 10.1007/978-1-4471-6458-6_4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The adenovirus E4orf4 protein is a multifunctional viral regulator that contributes to temporal regulation of the progression of viral infection. When expressed alone, outside the context of the virus, E4orf4 induces p53-independent cell-death in transformed cells. Oncogenic transformation of primary cells in tissue culture sensitizes them to cell killing by E4orf4, indicating that E4orf4 research may have implications for cancer therapy. It has also been reported that E4orf4 induces a caspase-independent, non-classical apoptotic pathway, which maintains crosstalk with classical caspase-dependent pathways. Furthermore, several E4orf4 activities in the nucleus and in the cytoplasm and various protein partners contribute to cell killing by this viral protein. In the following chapter I summarize the current knowledge of the unique mode of E4orf4-induced cell death and its underlying mechanisms. Although several explanations for the cancer-specificity of E4orf4-induced toxicity have been proposed, a better grasp of the mechanisms responsible for E4orf4-induced cell death is required to elucidate the differential sensitivity of normal and cancer cells to E4orf4.
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Affiliation(s)
- Tamar Kleinberger
- Department of Molecular Microbiology, The Rappaport Family Institute for Research in the Medical Sciences, Faculty of Medicine, Technion - Israel Institute of Technology, Haifa, 31096, Israel,
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Couzens AL, Knight JDR, Kean MJ, Teo G, Weiss A, Dunham WH, Lin ZY, Bagshaw RD, Sicheri F, Pawson T, Wrana JL, Choi H, Gingras AC. Protein interaction network of the mammalian Hippo pathway reveals mechanisms of kinase-phosphatase interactions. Sci Signal 2013; 6:rs15. [PMID: 24255178 DOI: 10.1126/scisignal.2004712] [Citation(s) in RCA: 345] [Impact Index Per Article: 31.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The Hippo pathway regulates organ size and tissue homeostasis in response to multiple stimuli, including cell density and mechanotransduction. Pharmacological inhibition of phosphatases can also stimulate Hippo signaling in cell culture. We defined the Hippo protein-protein interaction network with and without inhibition of serine and threonine phosphatases by okadaic acid. We identified 749 protein interactions, including 599 previously unrecognized interactions, and demonstrated that several interactions with serine and threonine phosphatases were phosphorylation-dependent. Mutation of the T-loop of MST2 (mammalian STE20-like protein kinase 2), which prevented autophosphorylation, disrupted its association with STRIPAK (striatin-interacting phosphatase and kinase complex). Deletion of the amino-terminal forkhead-associated domain of SLMAP (sarcolemmal membrane-associated protein), a component of the STRIPAK complex, prevented its association with MST1 and MST2. Phosphatase inhibition produced temporally distinct changes in proteins that interacted with MOB1A and MOB1B (Mps one binder kinase activator-like 1A and 1B) and promoted interactions with upstream Hippo pathway proteins, such as MST1 and MST2, and with the trimeric protein phosphatase 6 complex (PP6). Mutation of three basic amino acids that are part of a phospho-serine- and phospho-threonine-binding domain in human MOB1B prevented its interaction with MST1 and PP6 in cells treated with okadaic acid. Collectively, our results indicated that changes in phosphorylation orchestrate interactions between kinases and phosphatases in Hippo signaling, providing a putative mechanism for pathway regulation.
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Affiliation(s)
- Amber L Couzens
- 1Centre for Systems Biology, Lunenfeld-Tanenbaum Research Institute at Mount Sinai Hospital, Toronto, Ontario M5G 1X5, Canada
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Zhang M, Yogesha SD, Mayfield JE, Gill GN, Zhang Y. Viewing serine/threonine protein phosphatases through the eyes of drug designers. FEBS J 2013; 280:4739-60. [PMID: 23937612 DOI: 10.1111/febs.12481] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Revised: 07/03/2013] [Accepted: 08/02/2013] [Indexed: 01/04/2023]
Abstract
Protein phosphatases, as the counterpart to protein kinases, are essential for homeostatic balance of cell signaling. Small chemical compounds that modulate the specific activity of phosphatases can be powerful tools to elucidate the biological functions of these enzymes. More importantly, many phosphatases are central players in the development of pathological pathways where inactivation can reverse or delay the onset of human diseases. Therefore, potent inhibitors for such phosphatases can be of great therapeutic benefit. In contrast to the seemingly identical enzymatic mechanism and structural characterization of eukaryotic protein kinases, protein phosphatases evolved from diverse ancestors, resulting in different domain architectures, reaction mechanisms and active site properties. In this review, we discuss for each family of serine/threonine protein phosphatases their involvement in biological processes and corresponding strategies for small chemical intervention. Recent advances in modern drug discovery technologies have markedly facilitated the identification of selective inhibitors for some members of the phosphatase family. Furthermore, the rapid growth in knowledge about structure-activity relationships related to possible new drug targets has aided the discovery of natural product inhibitors for the phosphatase family. This review summarizes the current state of investigation of the small molecules that regulate the function of serine/threonine phosphatases, the challenges presented and also strategies to overcome these obstacles.
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Affiliation(s)
- Mengmeng Zhang
- Department of Chemistry and Biochemistry, University of Texas at Austin, TX, USA
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Hammond D, Zeng K, Espert A, Bastos RN, Baron RD, Gruneberg U, Barr FA. Melanoma-associated mutations in protein phosphatase 6 cause chromosome instability and DNA damage owing to dysregulated Aurora-A. J Cell Sci 2013; 126:3429-40. [PMID: 23729733 DOI: 10.1242/jcs.128397] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Mutations in the PPP6C catalytic subunit of protein phosphatase 6 (PP6) are drivers for the development of melanoma. Here, we analyse a panel of melanoma-associated mutations in PPP6C and find that these generally compromise assembly of the PP6 holoenzyme and catalytic activity towards a model substrate. Detailed analysis of one mutant, PPP6C-H114Y, in both primary melanoma and engineered cell lines reveals it is destabilized and undergoes increased proteasome-mediated turnover. Global analysis of phosphatase substrates by mass spectrometry identifies the oncogenic kinase Aurora-A as the major PP6 substrate that is dysregulated under these conditions. Accordingly, cells lacking PPP6C or carrying the PPP6C-H114Y allele have elevated Aurora-A kinase activity and display chromosome instability with associated Aurora-A-dependent micronucleation. Chromosomes mis-segregated to these micronuclei are preferentially stained by the DNA damage marker γ-H2AX, suggesting that loss of PPP6C promotes both chromosome instability and DNA damage. These findings support the view that formation of micronuclei rather than chromosome instability alone explains how loss of PPP6C, and more generally mitotic spindle and centrosome defects, can act as drivers for genome instability in melanoma and other cancers.
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Affiliation(s)
- Dean Hammond
- University of Oxford, Department of Biochemistry, South Parks Road, Oxford OX1 3QU, UK
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Dai M, Xue Q, Mccray T, Margavage K, Chen F, Lee JH, Nezames CD, Guo L, Terzaghi W, Wan J, Deng XW, Wang H. The PP6 phosphatase regulates ABI5 phosphorylation and abscisic acid signaling in Arabidopsis. THE PLANT CELL 2013; 25:517-34. [PMID: 23404889 PMCID: PMC3608775 DOI: 10.1105/tpc.112.105767] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2012] [Revised: 12/18/2012] [Accepted: 01/24/2013] [Indexed: 05/19/2023]
Abstract
The basic Leucine zipper transcription factor ABSCISIC ACID INSENSITIVE5 (ABI5) is a key regulator of abscisic acid (ABA)-mediated seed germination and postgermination seedling growth. While a family of SUCROSE NONFERMENTING1-related protein kinase2s (SnRK2s) is responsible for ABA-induced phosphorylation and stabilization of ABI5, the phosphatase(s) responsible for dephosphorylating ABI5 is still unknown. Here, we demonstrate that mutations in FyPP1 (for Phytochrome-associated serine/threonine protein phosphatase1) and FyPP3, two homologous genes encoding the catalytic subunits of Ser/Thr PROTEIN PHOSPHATASE6 (PP6), cause an ABA hypersensitive phenotype in Arabidopsis thaliana, including ABA-mediated inhibition of seed germination and seedling growth. Conversely, overexpression of FyPP causes reduced sensitivity to ABA. The ABA hypersensitive phenotype of FyPP loss-of-function mutants is ABI5 dependent, and the amount of phosphorylated and total ABI5 proteins inversely correlates with the levels of FyPP proteins. Moreover, FyPP proteins physically interact with ABI5 in vitro and in vivo, and the strength of the interaction depends on the ABI5 phosphorylation status. In vitro phosphorylation assays show that FyPP proteins directly dephosphorylate ABI5. Furthermore, genetic and biochemical assays show that FyPP proteins act antagonistically with SnRK2 kinases to regulate ABI5 phosphorylation and ABA responses. Thus, Arabidopsis PP6 phosphatase regulates ABA signaling through dephosphorylation and destabilization of ABI5.
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Affiliation(s)
- Mingqiu Dai
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520-8104
| | - Qin Xue
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520-8104
| | - Tyra Mccray
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520-8104
| | - Kathryn Margavage
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520-8104
- Department of Biology, Wilkes University, Wilkes-Barre, Pennsylvania 18766
| | - Fang Chen
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520-8104
| | - Jae-Hoon Lee
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520-8104
- Department of Biology Education, Pusan National University, Busan 609-735, Korea
| | - Cynthia D. Nezames
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520-8104
| | - Liquan Guo
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520-8104
- State Environmental Protection Key Laboratory of Wetland Ecology and Vegetation Restoration, Northeast Normal University, Changchun 130062, China
| | - William Terzaghi
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520-8104
- Department of Biology, Wilkes University, Wilkes-Barre, Pennsylvania 18766
| | - Jianmin Wan
- Institute of Crop Sciences, Chinese Academy of Agriculture Sciences, Beijing 100081, China
| | - Xing Wang Deng
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520-8104
- National Engineering Research Center for Crop Molecular Design, Beijing 100085, China
| | - Haiyang Wang
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520-8104
- Institute of Crop Sciences, Chinese Academy of Agriculture Sciences, Beijing 100081, China
- National Engineering Research Center for Crop Molecular Design, Beijing 100085, China
- College of Life Science, Capital Normal University, Beijing, 100048, China
- Address correspondence to
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Haeseleer F, Sokal I, Gregory FD, Lee A. Protein phosphatase 2A dephosphorylates CaBP4 and regulates CaBP4 function. Invest Ophthalmol Vis Sci 2013; 54:1214-26. [PMID: 23341017 DOI: 10.1167/iovs.12-11319] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE CaBP4 is a neuronal Ca(2+)-binding protein that is expressed in the retina and in the cochlea, and is essential for normal photoreceptor synaptic function. CaBP4 is phosphorylated by protein kinase C zeta (PKCζ) in the retina at serine 37, which affects its interaction with and modulation of voltage-gated Ca(v)1 Ca(2+) channels. In this study, we investigated the potential role and functional significance of protein phosphatase 2A (PP2A) in CaBP4 dephosphorylation. METHODS The effect of protein phosphatase inhibitors, light, and overexpression of PP2A subunits on CaBP4 dephosphorylation was measured in in vitro assays. Pull-down experiments using retinal or transfected HEK293 cell lysates were used to investigate the association between CaBP4 and PP2A subunits. Electrophysiologic recordings of cotransfected HEK293 cells were performed to analyze the effect of CaBP4 dephosphorylation in modulating Ca(v)1.3 currents. RESULTS PP2A inhibitors, okadaic acid (OA), and fostriecin, but not PP1 selective inhibitors, NIPP-1, and inhibitor 2, block CaBP4 dephosphorylation in retinal lysates. Increased phosphatase activity in light-dependent conditions reverses phosphorylation of CaBP4 by PKCζ. In HEK293 cells, overexpression of PP2A enhances the rate of dephosphorylation of CaBP4. In addition, inhibition of protein phosphatase activity by OA increases CaBP4 phosphorylation and potentiates the modulatory effect of CaBP4 on Ca(v)1.3 Ca(2+) channels in HEK293T cells. CONCLUSIONS This study provides evidence that CaBP4 is dephosphorylated by PP2A in the retina. Our findings reveal a novel role for protein phosphatases in regulating CaBP4 function in the retina, which may fine tune presynaptic Ca(2+) signals at the photoreceptor synapse.
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Affiliation(s)
- Françoise Haeseleer
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA.
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Dephosphorylation of endogenous GABA(B) receptor R2 subunit and AMPK α subunits which were measured by in vitro method using transfer membrane. Neurochem Int 2012; 62:137-44. [PMID: 23238131 DOI: 10.1016/j.neuint.2012.12.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2012] [Revised: 11/17/2012] [Accepted: 12/05/2012] [Indexed: 01/19/2023]
Abstract
Protein phosphorylation can be regulated by changes in kinase activity, phosphatase activity, or both. GABA(B) receptor R2 subunit (GABA(B)R2) is phosphorylated at S783 by 5'-AMP-activated-protein kinase (AMPK), and this phosphorylation modulates GABA(B) receptor desensitization. Since the GABA(B) receptor is an integral membrane protein, solubilizing GABA(B)R2 is difficult. To circumvent this problem and to identify specific phosphatases that dephosphorylate S783, we employed an in vitro assay based on dephosphorylation of proteins on PVDF membranes by purified phosphatases. Our method allowed us to demonstrate that S783 in GABA(B)R2 is directly dephosphorylated by PP2A (but not by PP1, PP2B nor PP2C) in a dose-dependent and okadaic acid-sensitive manner. We also show that the level of phosphorylation of the catalytic subunit of AMPK at T172 is reduced by PP1, PP2A and PP2C. Our data indicate that PP2A dephosphorylates GABA(B)R2(S783) less efficiently than AMPK(T172), and that additional phosphatases might be involved in S783 dephosphorylation.
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47
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Woo SM, Min KJ, Kwon TK. Calyculin A causes sensitization to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis by ROS-mediated down-regulation of cellular FLICE-inhibiting protein (c-FLIP) and by enhancing death receptor 4 mRNA stabilization. Apoptosis 2012; 17:1223-34. [DOI: 10.1007/s10495-012-0753-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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48
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Magnaudeix A, Wilson CM, Page G, Bauvy C, Codogno P, Lévêque P, Labrousse F, Corre-Delage M, Yardin C, Terro F. PP2A blockade inhibits autophagy and causes intraneuronal accumulation of ubiquitinated proteins. Neurobiol Aging 2012; 34:770-90. [PMID: 22892312 DOI: 10.1016/j.neurobiolaging.2012.06.026] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Revised: 05/30/2012] [Accepted: 06/29/2012] [Indexed: 12/11/2022]
Abstract
Using cultured cortical neurons, we show that the blockade of protein phosphatase 2A (PP2A), either pharmacologically by okadaic acid or by short hairpin RNA (shRNA)-mediated silencing of PP2A catalytic subunit, inhibited basal autophagy and autophagy induced in several experimental settings (including serum deprivation, endoplasmic reticulum stress, rapamycin, and proteasome inhibition) at early stages before autophagosome maturation. Conversely, PP2A upregulation by PP2A catalytic subunit overexpression stimulates neuronal autophagy. In addition, PP2A blockade resulted in the activation of the negative regulator of autophagy mammalian target of rapamycin complex 1 and 5' adenosine monophosphate (AMP)-activated protein kinase (AMPK) and led to intraneuronal accumulation of p62- and ubiquitin-positive protein inclusions, likely due to autophagy downregulation. These data are consistent with previous findings showing that specific invalidation of the autophagy process in the nervous system of mouse resulted in the accumulation of p62- and ubiquitin-positive protein inclusion bodies. Furthermore, we showed that PP2A inhibition alters the distribution of the microtubule-associated protein 1 light chain(LC) 3-I (MAP LC3-I), a key component of the autophagy molecular machinery. Whether MAP LC3-I distribution in the cell accounts for autophagy regulation remains to be determined. These data are important to human neurodegenerative diseases, especially Alzheimer's disease, because they provide links for the first time between the pathological features of Alzheimer's disease:PP2A downregulation, autophagy disruption, and protein aggregation.
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Affiliation(s)
- Amandine Magnaudeix
- Laboratoire d'Histologie, de Biologie Cellulaire et de Cytogénétique, Faculté de Médecine, Université de Limoges, Limoges, France
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The role of translation initiation regulation in haematopoiesis. Comp Funct Genomics 2012; 2012:576540. [PMID: 22649283 PMCID: PMC3357504 DOI: 10.1155/2012/576540] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2012] [Accepted: 02/25/2012] [Indexed: 02/06/2023] Open
Abstract
Organisation of RNAs into functional subgroups that are translated in response to extrinsic and intrinsic factors underlines a relatively unexplored gene expression modulation that drives cell fate in the same manner as regulation of the transcriptome by transcription factors. Recent studies on the molecular mechanisms of inflammatory responses and haematological disorders indicate clearly that the regulation of mRNA translation at the level of translation initiation, mRNA stability, and protein isoform synthesis is implicated in the tight regulation of gene expression. This paper outlines how these posttranscriptional control mechanisms, including control at the level of translation initiation factors and the role of RNA binding proteins, affect hematopoiesis. The clinical relevance of these mechanisms in haematological disorders indicates clearly the potential therapeutic implications and the need of molecular tools that allow measurement at the level of translational control. Although the importance of miRNAs in translation control is well recognised and studied extensively, this paper will exclude detailed account of this level of control.
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Sents W, Ivanova E, Lambrecht C, Haesen D, Janssens V. The biogenesis of active protein phosphatase 2A holoenzymes: a tightly regulated process creating phosphatase specificity. FEBS J 2012; 280:644-61. [PMID: 22443683 DOI: 10.1111/j.1742-4658.2012.08579.x] [Citation(s) in RCA: 157] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Protein phosphatase type 2A (PP2A) enzymes constitute a large family of Ser/Thr phosphatases with multiple functions in cellular signaling and physiology. The composition of heterotrimeric PP2A holoenzymes, resulting from the combinatorial assembly of a catalytic C subunit, a structural A subunit, and regulatory B-type subunit, provides the essential determinants for substrate specificity, subcellular targeting, and fine-tuning of phosphatase activity, largely explaining why PP2A is functionally involved in so many diverse physiological processes, sometimes in seemingly opposing ways. In this review, we highlight how PP2A holoenzyme biogenesis and enzymatic activity are controlled by a sophisticatedly coordinated network of five PP2A modulators, consisting of α4, phosphatase 2A phosphatase activator (PTPA), leucine carboxyl methyl transferase 1 (LCMT1), PP2A methyl esterase 1 (PME-1) and, potentially, target of rapamycin signaling pathway regulator-like 1 (TIPRL1), which serve to prevent promiscuous phosphatase activity until the holoenzyme is completely assembled. Likewise, these modulators may come into play when PP2A holoenzymes are disassembled following particular cellular stresses. Malfunctioning of these cellular control mechanisms contributes to human disease. The potential therapeutic benefits or pitfalls of interfering with these regulatory mechanisms will be briefly discussed.
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Affiliation(s)
- Ward Sents
- Laboratory of Protein Phosphorylation & Proteomics, Department of Cellular and Molecular Medicine, University of Leuven, Leuven, Belgium
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