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Wachter F, Nowak RP, Ficarro S, Marto J, Fischer ES. Structural characterization of methylation-independent PP2A assembly guides alphafold2Multimer prediction of family-wide PP2A complexes. J Biol Chem 2024; 300:107268. [PMID: 38582449 PMCID: PMC11087950 DOI: 10.1016/j.jbc.2024.107268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 03/31/2024] [Accepted: 04/02/2024] [Indexed: 04/08/2024] Open
Abstract
Dysregulation of phosphorylation-dependent signaling is a hallmark of tumorigenesis. Protein phosphatase 2 (PP2A) is an essential regulator of cell growth. One scaffold subunit (A) binds to a catalytic subunit (C) to form a core AC heterodimer, which together with one of many regulatory (B) subunits forms the active trimeric enzyme. The combinatorial number of distinct PP2A complexes is large, which results in diverse substrate specificity and subcellular localization. The detailed mechanism of PP2A assembly and regulation remains elusive and reports about an important role of methylation of the carboxy terminus of PP2A C are conflicting. A better understanding of the molecular underpinnings of PP2A assembly and regulation is critical to dissecting PP2A function in physiology and disease. Here, we combined biochemical reconstitution, mass spectrometry, X-ray crystallography, and functional assays to characterize the assembly of trimeric PP2A. In vitro studies demonstrated that methylation of the carboxy-terminus of PP2A C was dispensable for PP2A assembly in vitro. To corroborate these findings, we determined the X-ray crystal structure of the unmethylated PP2A Aα-B56ε-Cα trimer complex to 3.1 Å resolution. The experimental structure superimposed well with an Alphafold2Multimer prediction of the PP2A trimer. We then predicted models of all canonical PP2A complexes providing a framework for structural analysis of PP2A. In conclusion, methylation was dispensable for trimeric PP2A assembly and integrative structural biology studies of PP2A offered predictive models for all canonical PP2A complexes.
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Affiliation(s)
- Franziska Wachter
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA; Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, USA
| | - Radosław P Nowak
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, USA
| | - Scott Ficarro
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA
| | - Jarrod Marto
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA
| | - Eric S Fischer
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, USA.
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2
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Joyce AW, Searle BC. Computational approaches to identify sites of phosphorylation. Proteomics 2024; 24:e2300088. [PMID: 37897210 DOI: 10.1002/pmic.202300088] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 10/07/2023] [Accepted: 10/09/2023] [Indexed: 10/29/2023]
Abstract
Due to their oftentimes ambiguous nature, phosphopeptide positional isomers can present challenges in bottom-up mass spectrometry-based workflows as search engine scores alone are often not enough to confidently distinguish them. Additional scoring algorithms can remedy this by providing confidence metrics in addition to these search results, reducing ambiguity. Here we describe challenges to interpreting phosphoproteomics data and review several different approaches to determine sites of phosphorylation for both data-dependent and data-independent acquisition-based workflows. Finally, we discuss open questions regarding neutral losses, gas-phase rearrangement, and false localization rate estimation experienced by both types of acquisition workflows and best practices for managing ambiguity in phosphosite determination.
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Affiliation(s)
- Alex W Joyce
- Department of Biomedical Informatics, The Ohio State University Medical Center, Columbus, Ohio, USA
- Pelotonia Institute for Immuno-Oncology, The Ohio State University Comprehensive Cancer Center, Columbus, Ohio, USA
| | - Brian C Searle
- Department of Biomedical Informatics, The Ohio State University Medical Center, Columbus, Ohio, USA
- Pelotonia Institute for Immuno-Oncology, The Ohio State University Comprehensive Cancer Center, Columbus, Ohio, USA
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio, USA
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3
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Fan YG, Guo C, Zhao LX, Ge RL, Pang ZQ, He DL, Ren H, Wu TY, Zhang YH, Wang ZY. Astrocyte-derived lactoferrin reduces β-amyloid burden by promoting the interaction between p38 kinase and PP2A phosphatase in male APP/PS1 transgenic mice. Br J Pharmacol 2024; 181:896-913. [PMID: 37309219 DOI: 10.1111/bph.16161] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2022] [Revised: 04/23/2023] [Accepted: 06/03/2023] [Indexed: 06/14/2023] Open
Abstract
BACKGROUND AND PURPOSE Overexpression of astrocytic lactoferrin (Lf) was observed in the brain of Alzheimer's disease (AD) patients, whereas the role of astrocytic Lf in AD progression remains unexplored. In this study, we aimed to evaluate the effects of astrocytic Lf on AD progression. EXPERIMENTAL APPROACH Male APP/PS1 mice with astrocytes overexpressing human Lf were developed to evaluate the effects of astrocytic Lf on AD progression. N2a-sw cells also were employed to further uncover the mechanism of astrocytic Lf on β-amyloid (Aβ) production. KEY RESULTS Astrocytic Lf overexpression increased protein phosphatase 2A (PP2A) activity and reduced amyloid precursor protein (APP) phosphorylation, Aβ burden and tau hyperphosphorylation in APP/PS1 mice. Mechanistically, astrocytic Lf overexpression promoted the uptake of astrocytic Lf into neurons in APP/PS1 mice, and conditional medium from astrocytes overexpressing Lf inhibited p-APP (Thr668) expression in N2a-sw cells. Furthermore, recombinant human Lf (hLf) significantly enhanced PP2A activity and inhibited p-APP expression, whereas inhibition of p38 or PP2A activities abrogated the hLf-induced p-APP down-regulation in N2a-sw cells. Additionally, hLf promoted the interaction of p38 and PP2A via p38 activation, thereby enhancing PP2A activity, and low-density lipoprotein receptor-related protein 1 (LRP1) knockdown significantly reversed the hLf-induced p38 activation and p-APP down-regulation. CONCLUSIONS AND IMPLICATIONS Our data suggested that astrocytic Lf promoted neuronal p38 activation, via targeting to LRP1, subsequently promoting p38 binding to PP2A to enhance PP2A enzyme activity, which finally inhibited Aβ production via APP dephosphorylation. In conclusion, promoting astrocytic Lf expression may be a potential strategy against AD. LINKED ARTICLES This article is part of a themed issue From Alzheimer's Disease to Vascular Dementia: Different Roads Leading to Cognitive Decline. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.6/issuetoc.
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Affiliation(s)
- Yong-Gang Fan
- Key Laboratory of Medical Cell Biology of Ministry of Education, Key Laboratory of Major Chronic Diseases of Nervous System of Liaoning Province, Health Sciences Institute of China Medical University, Shenyang, China
| | - Chuang Guo
- College of Life and Health Sciences, Northeastern University, Shenyang, China
| | - Ling-Xiao Zhao
- Key Laboratory of Medical Cell Biology of Ministry of Education, Key Laboratory of Major Chronic Diseases of Nervous System of Liaoning Province, Health Sciences Institute of China Medical University, Shenyang, China
| | - Ri-Le Ge
- Key Laboratory of Medical Cell Biology of Ministry of Education, Key Laboratory of Major Chronic Diseases of Nervous System of Liaoning Province, Health Sciences Institute of China Medical University, Shenyang, China
| | - Zhong-Qiu Pang
- College of Life and Health Sciences, Northeastern University, Shenyang, China
| | - Da-Long He
- Key Laboratory of Medical Cell Biology of Ministry of Education, Key Laboratory of Major Chronic Diseases of Nervous System of Liaoning Province, Health Sciences Institute of China Medical University, Shenyang, China
| | - Hang Ren
- Key Laboratory of Medical Cell Biology of Ministry of Education, Key Laboratory of Major Chronic Diseases of Nervous System of Liaoning Province, Health Sciences Institute of China Medical University, Shenyang, China
| | - Ting-Yao Wu
- First Affiliated Hospital of Jinzhou Medical University, Jinzhou, China
| | - Yan-Hui Zhang
- Key Laboratory of Medical Cell Biology of Ministry of Education, Key Laboratory of Major Chronic Diseases of Nervous System of Liaoning Province, Health Sciences Institute of China Medical University, Shenyang, China
| | - Zhan-You Wang
- Key Laboratory of Medical Cell Biology of Ministry of Education, Key Laboratory of Major Chronic Diseases of Nervous System of Liaoning Province, Health Sciences Institute of China Medical University, Shenyang, China
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4
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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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5
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Jiang TY, Cui XW, Zeng TM, Pan YF, Lin YK, Feng XF, Tan YX, Yuan ZG, Dong LW, Wang HY. PTEN deficiency facilitates gemcitabine efficacy in cancer by modulating the phosphorylation of PP2Ac and DCK. Sci Transl Med 2023; 15:eadd7464. [PMID: 37437018 DOI: 10.1126/scitranslmed.add7464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Accepted: 06/22/2023] [Indexed: 07/14/2023]
Abstract
Gemcitabine is a nucleoside analog that has been successfully used in the treatment of multiple cancers. However, intrinsic or acquired resistance reduces the chemotherapeutic potential of gemcitabine. Here, we revealed a previously unappreciated mechanism by which phosphatase and tensin homolog (PTEN), one of the most frequently mutated genes in human cancers, dominates the decision-making process that is central to the regulation of gemcitabine efficacy in cholangiocarcinoma (CCA). By investigating a gemcitabine-treated CCA cohort, we found that PTEN deficiency was correlated with the improved efficacy of gemcitabine-based chemotherapy. Using cell-based drug sensitivity assays, cell line-derived xenograft, and patient-derived xenograft models, we further confirmed that PTEN deficiency or genetic-engineering down-regulation of PTEN facilitated gemcitabine efficacy both in vitro and in vivo. Mechanistically, PTEN directly binds to and dephosphorylates the C terminus of the catalytic subunit of protein phosphatase 2A (PP2Ac) to increase its enzymatic activity, which further dephosphorylates deoxycytidine kinase (DCK) at Ser74 to diminish gemcitabine efficacy. Therefore, PTEN deficiency and high phosphorylation of DCK predict a better response to gemcitabine-based chemotherapy in CCA. We speculate that the combination of PP2A inhibitor and gemcitabine in PTEN-positive tumors could avoid the resistance of gemcitabine, which would benefit a large population of patients with cancer receiving gemcitabine or other nucleoside analogs.
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Affiliation(s)
- Tian-Yi Jiang
- International Cooperation Laboratory on Signal Transduction, Eastern Hepatobiliary Surgery Institute, the Naval Medical University, Shanghai 200438, China
- National Center for Liver Cancer, the Naval Medical University, Shanghai 201805, China
| | - Xiao-Wen Cui
- National Center for Liver Cancer, the Naval Medical University, Shanghai 201805, China
- Department of Oncology, Eastern Hepatobiliary Surgery Hospital, the Naval Medical University, Shanghai 201805, China
| | - Tian-Mei Zeng
- Department of Oncology, Eastern Hepatobiliary Surgery Hospital, the Naval Medical University, Shanghai 201805, China
| | - Yu-Fei Pan
- International Cooperation Laboratory on Signal Transduction, Eastern Hepatobiliary Surgery Institute, the Naval Medical University, Shanghai 200438, China
- National Center for Liver Cancer, the Naval Medical University, Shanghai 201805, China
| | - Yun-Kai Lin
- International Cooperation Laboratory on Signal Transduction, Eastern Hepatobiliary Surgery Institute, the Naval Medical University, Shanghai 200438, China
- National Center for Liver Cancer, the Naval Medical University, Shanghai 201805, China
| | - Xiao-Fan Feng
- National Center for Liver Cancer, the Naval Medical University, Shanghai 201805, China
| | - Ye-Xiong Tan
- National Center for Liver Cancer, the Naval Medical University, Shanghai 201805, China
| | - Zhen-Gang Yuan
- Department of Oncology, Eastern Hepatobiliary Surgery Hospital, the Naval Medical University, Shanghai 201805, China
| | - Li-Wei Dong
- International Cooperation Laboratory on Signal Transduction, Eastern Hepatobiliary Surgery Institute, the Naval Medical University, Shanghai 200438, China
- National Center for Liver Cancer, the Naval Medical University, Shanghai 201805, China
| | - Hong-Yang Wang
- International Cooperation Laboratory on Signal Transduction, Eastern Hepatobiliary Surgery Institute, the Naval Medical University, Shanghai 200438, China
- National Center for Liver Cancer, the Naval Medical University, Shanghai 201805, China
- State Key Laboratory of Oncogenes and Related Genes, Shanghai Cancer Institute, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200127, China
- Shanghai Key Laboratory of Hepatobiliary Tumor Biology, Shanghai, 200438, China
- Laboratory of Signaling Regulation and Targeting Therapy of Liver Cancer, the Naval Medical University and Ministry of Education, Shanghai 200438, China
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6
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Haanen TJ, O'Connor CM, Narla G. Biased holoenzyme assembly of protein phosphatase 2A (PP2A): From cancer to small molecules. J Biol Chem 2022; 298:102656. [PMID: 36328247 PMCID: PMC9707111 DOI: 10.1016/j.jbc.2022.102656] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Revised: 10/25/2022] [Accepted: 10/27/2022] [Indexed: 11/06/2022] Open
Abstract
Protein phosphatase 2A (PP2A) is a family of serine threonine phosphatases responsible for regulating protein phosphorylation, thus opposing the activity of cellular kinases. PP2A is composed of a catalytic subunit (PP2A Cα/β) and scaffolding subunit (PP2A Aα/β) and various substrate-directing B regulatory subunits. PP2A biogenesis is regulated at multiple levels. For example, the sequestration of the free catalytic subunit during the process of biogenesis avoids promiscuous phosphatase activity. Posttranslational modifications of PP2A C direct PP2A heterotrimeric formation. Additionally, PP2A functions as a haploinsufficient tumor suppressor, where attenuated PP2A enzymatic activity creates a permissive environment for oncogenic transformation. Recent work studying PP2A in cancer showed that its role in tumorigenesis is more nuanced, with some holoenzymes being tumor suppressive, while others are required for oncogenic transformation. In cancer biology, PP2A function is modulated through various mechanisms including the displacement of specific B regulatory subunits by DNA tumor viral antigens, by recurrent mutations, and through loss of carboxymethyl-sensitive heterotrimeric complexes. In aggregate, these alterations bias PP2A activity away from its tumor suppressive functions and toward oncogenic ones. From a therapeutic perspective, molecular glues and disruptors present opportunities for both the selective stabilization of tumor-suppressive holoenzymes and disruption of holoenzymes that are pro-oncogenic. Collectively, these approaches represent an attractive cancer therapy for a wide range of tumor types. This review will discuss the mechanisms by which PP2A holoenzyme formation is dysregulated in cancer and the current therapies that are aimed at biasing heterotrimer formation of PP2A for the treatment of cancer.
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7
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Sontag JM, Schuhmacher D, Taleski G, Jordan A, Khan S, Hoffman A, Gomez RJ, Mazalouskas MD, Hanks SK, Spiller BW, Sontag E, Wadzinski BE. A new paradigm for regulation of protein phosphatase 2A function via Src and Fyn kinase-mediated tyrosine phosphorylation. J Biol Chem 2022; 298:102248. [PMID: 35820485 PMCID: PMC9396060 DOI: 10.1016/j.jbc.2022.102248] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Revised: 07/01/2022] [Accepted: 07/04/2022] [Indexed: 12/01/2022] Open
Abstract
Protein phosphatase 2A (PP2A) is a major phospho-Ser/Thr phosphatase and a key regulator of cellular signal transduction pathways. While PP2A dysfunction has been linked to human cancer and neurodegenerative disorders such as Alzheimer’s disease (AD), PP2A regulation remains relatively poorly understood. It has been reported that the PP2A catalytic subunit (PP2Ac) is inactivated by a single phosphorylation at the Tyr307 residue by tyrosine kinases such as v-Src. However, multiple mass spectrometry studies have revealed the existence of other putative PP2Ac phosphorylation sites in response to activation of Src and Fyn, two major Src family kinases (SFKs). Here, using PP2Ac phosphomutants and novel phosphosite-specific PP2Ac antibodies, we show that cellular pools of PP2Ac are instead phosphorylated on both Tyr127 and Tyr284 upon Src activation, and on Tyr284 following Fyn activation. We found these phosphorylation events enhanced the interaction of PP2Ac with SFKs. In addition, we reveal SFK-mediated phosphorylation of PP2Ac at Y284 promotes dissociation of the regulatory Bα subunit, altering PP2A substrate specificity; the phosphodeficient Y127/284F and Y284F PP2Ac mutants prevented SFK-mediated phosphorylation of Tau at the CP13 (pSer202) epitope, a pathological hallmark of AD, and SFK-dependent activation of ERK, a major growth regulatory kinase upregulated in many cancers. Our findings demonstrate a novel PP2A regulatory mechanism that challenges the existing dogma on the inhibition of PP2A catalytic activity by Tyr307 phosphorylation. We propose dysregulation of SFK signaling in cancer and AD can lead to alterations in PP2A phosphorylation and subsequent deregulation of key PP2A substrates, including ERK and Tau.
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Affiliation(s)
- Jean-Marie Sontag
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia
| | - Diana Schuhmacher
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia
| | - Goce Taleski
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia
| | - Anthony Jordan
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Sarah Khan
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Alexander Hoffman
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia
| | - Rey J Gomez
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Matthew D Mazalouskas
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Steven K Hanks
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Benjamin W Spiller
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Estelle Sontag
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia.
| | - Brian E Wadzinski
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA.
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8
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Qiao HY, Zhang Q, Wang JM, Jiang JY, Huyan LY, Yan J, Li C, Wang HQ. TRIM29 regulates the SETBP1/SET/PP2A axis via transcription factor VEZF1 to promote progression of ovarian cancer. Cancer Lett 2021; 529:85-99. [PMID: 34973391 DOI: 10.1016/j.canlet.2021.12.029] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2021] [Revised: 12/09/2021] [Accepted: 12/25/2021] [Indexed: 12/14/2022]
Abstract
Ovarian cancer (OC) is a common gynecological malignant tumor that seriously endangers the health of women worldwide. Tripartite motif containing 29 (TRIM29) is a TRIM family member that is frequently overexpressed in OC. However, the specific role of TRIM29 in OC remains obscure. To investigate the underlying molecular mechanism, a global proteomics analysis identified SET binding protein 1 (SETBP1) as a crucial target of TRIM29. Subsequently, the SETBP1/SET/Protein phosphatase 2 (PP2A) axis was confirmed to be required for the recovery of cancer stem cell (CSC)-like phenotype suppressed by TRIM29 knockdown. Mechanistically, TRIM29 facilitated SETBP1 transcriptional activation via the VEZF1 transcription factor. More importantly, TRIM29 promoted VEZF1 mRNA translation by recruiting RNA binding protein BICC1 to its 3'UTR. The clinical significance was established by the association of TRIM29 and SETBP1 expression with clinicopathological features in OC samples. The SETBP1/SET/PP2A axis driven by TRIM29 via transcription factor VEZF1 is at least one of the primary mechanisms underlying TRIM29 maintenance of the CSC-like characteristics in OC.
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Affiliation(s)
- Huai-Yu Qiao
- Department of Biochemistry & Molecular Biology, China Medical University, Shenyang, 110026, China
| | - Qi Zhang
- Criminal Investigation Police University of China, Shenyang, 110854, China
| | - Jia-Mei Wang
- Department of Laboratory Medicine, The 1st affiliated hospital, China Medical University, Shenyang, 110001, China
| | - Jing-Yi Jiang
- Department of Biochemistry & Molecular Biology, China Medical University, Shenyang, 110026, China
| | - Ling-Yue Huyan
- 5+3 integrated clinical medicine 103K, China Medical University, Shenyang, 110026, China
| | - Jing Yan
- Department of Biochemistry & Molecular Biology, China Medical University, Shenyang, 110026, China
| | - Chao Li
- Department of Biochemistry & Molecular Biology, China Medical University, Shenyang, 110026, China
| | - Hua-Qin Wang
- Department of Biochemistry & Molecular Biology, China Medical University, Shenyang, 110026, China.
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9
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Lyons SP, Greiner EC, Cressey LE, Adamo ME, Kettenbach AN. Regulation of PP2A, PP4, and PP6 holoenzyme assembly by carboxyl-terminal methylation. Sci Rep 2021; 11:23031. [PMID: 34845248 PMCID: PMC8630191 DOI: 10.1038/s41598-021-02456-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 11/15/2021] [Indexed: 12/16/2022] Open
Abstract
The family of Phosphoprotein Phosphatases (PPPs) is responsible for most cellular serine and threonine dephosphorylation. PPPs achieve substrate specificity and selectivity by forming multimeric holoenzymes. PPP holoenzyme assembly is tightly controlled, and changes in the cellular repertoire of PPPs are linked to human disease, including cancer and neurodegeneration. For PP2A, PP4, and PP6, holoenzyme formation is in part regulated by carboxyl (C)-terminal methyl-esterification (often referred to as "methylation"). Here, we use mass spectrometry-based proteomics, methylation-ablating mutations, and genome editing to elucidate the role of C-terminal methylation on PP2A, PP4, and PP6 holoenzyme assembly. We find that the catalytic subunits of PP2A, PP4, and PP6 are frequently methylated in cancer cells and that deletion of the C-terminal leucine faithfully recapitulates loss of methylation. We observe that loss of PP2A methylation consistently reduced B55, B56, and B72 regulatory subunit binding in cancer and non-transformed cell lines. However, Striatin subunit binding is only affected in non-transformed cells. For PP4, we find that PP4R1 and PP4R3β bind in a methylation-dependent manner. Intriguingly, loss of methylation does not affect PP6 holoenzymes. Our analyses demonstrate in an unbiased, comprehensive, and isoform-specific manner the crucial regulatory function of endogenous PPP methylation in transformed and non-transformed cell lines.
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Affiliation(s)
- Scott P Lyons
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH, USA
| | | | | | | | - Arminja N Kettenbach
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH, USA.
- Norris Cotton Cancer Center, Lebanon, NH, USA.
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10
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Sabbir MG, Taylor CG, Zahradka P. Antisense overlapping long non-coding RNA regulates coding arachidonate 12-lipoxygenase gene by translational interference. Biochim Biophys Acta Mol Cell Biol Lipids 2021; 1866:158987. [PMID: 34174394 DOI: 10.1016/j.bbalip.2021.158987] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 05/13/2021] [Accepted: 06/03/2021] [Indexed: 01/18/2023]
Abstract
The arachidonate 12-lipoxygenase (ALOX12) enzyme catalyzes polyunsaturated fatty acids and facilitates generation of bioactive lipid mediators associated with various biological processes and disease pathologies. The human genome assembly revealed that the ALOX12 gene overlaps an antisense non-coding gene designated as ALOX12-antisense 1 (ALOX12-AS1). This arrangement indicates that the uncharacterized ALOX12-AS1 long non-coding RNA (lncRNA) may bind to the sense coding ALOX12 mRNA to form an antisense-sense duplex providing the basis of a novel ALOX12 regulatory mechanism. Therefore, this study was designed to determine whether the interaction of ALOX12-AS1 with ALOX12 mRNA functions as an anti-sense/sense duplex-mediated regulatory mechanism controlling the cellular content of ALOX12. Our findings indicate that two major isoforms of ALOX12-AS1 lncRNA are ubiquitously expressed in a variety of primary adult human tissues and different transformed cell types. RNA-FISH revealed cell-type-specific cytosolic as well as nuclear and nucleolar localization of the lncRNA. Interestingly, phorbol ester-induced nucleo-cytoplasmic translocation of the lncRNA in monocytic THP-1 cells resulted in a reduction of ALOX12 protein without a concomitant change in its mRNA level. This indicated ALOX12-AS1 operates via an antisense-sense duplex-mediated translational downregulation mechanism. This deduction was validated by demonstrating sense/antisense duplex formation and an association of the duplex with ribosomal proteins in HEK293 cells. Overall, this study revealed a hitherto unknown mechanism of antisense lncRNA-mediated translational downregulation of ALOX12 that adds to the existing regulatory mechanisms for the modulation of potent bioactive lipid mediators that contribute to both health and disease.
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Affiliation(s)
- Mohammad Golam Sabbir
- Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Albrechtsen Research Centre, Winnipeg, MB R2H 2A6, Canada.
| | - Carla G Taylor
- Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Albrechtsen Research Centre, Winnipeg, MB R2H 2A6, Canada; Department of Food and Human Nutritional Sciences, University of Manitoba, Winnipeg, MB R3T 2N2, Canada; Department of Physiology and Pathophysiology, University of Manitoba, Winnipeg, MB R3E 0J9, Canada
| | - Peter Zahradka
- Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Albrechtsen Research Centre, Winnipeg, MB R2H 2A6, Canada; Department of Food and Human Nutritional Sciences, University of Manitoba, Winnipeg, MB R3T 2N2, Canada; Department of Physiology and Pathophysiology, University of Manitoba, Winnipeg, MB R3E 0J9, Canada
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11
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Frohner IE, Mudrak I, Schüchner S, Anrather D, Hartl M, Sontag JM, Sontag E, Wadzinski BE, Preglej T, Ellmeier W, Ogris E. PP2A C Phospho-Tyr 307 Antibodies Are Not Specific for this Modification but Are Sensitive to Other PP2A C Modifications Including Leu 309 Methylation. Cell Rep 2021; 30:3171-3182.e6. [PMID: 32130916 DOI: 10.1016/j.celrep.2020.02.035] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 12/03/2019] [Accepted: 02/07/2020] [Indexed: 02/06/2023] Open
Abstract
Protein phosphatase 2A (PP2A) is an important regulator of signal transduction pathways and a tumor suppressor. Phosphorylation of the PP2A catalytic subunit (PP2AC) at tyrosine 307 has been claimed to inactivate PP2A and was examined in more than 180 studies using commercial antibodies, but this modification was never identified using mass spectrometry. Here we show that the most cited pTyr307 monoclonal antibodies, E155 and F-8, are not specific for phosphorylated Tyr307 but instead are hampered by PP2AC methylation at leucine 309 or phosphorylation at threonine 304. Other pTyr307 antibodies are sensitive to PP2AC methylation as well, and some cross-react with pTyr residues in general, including phosphorylated hemagglutinin tags. We identify pTyr307 using targeted mass spectrometry after transient overexpression of PP2AC and Src kinase. Yet under such conditions, none of the tested antibodies show exclusive pTyr307 specificity. Thus, data generated using these antibodies need to be revisited, and the mechanism of PP2A inactivation needs to be redefined.
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Affiliation(s)
- Ingrid E Frohner
- Center for Medical Biochemistry, Max Perutz Labs, Medical University of Vienna, Dr. Bohr-Gasse 9, 1030 Vienna, Austria
| | - Ingrid Mudrak
- Center for Medical Biochemistry, Max Perutz Labs, Medical University of Vienna, Dr. Bohr-Gasse 9, 1030 Vienna, Austria
| | - Stefan Schüchner
- Center for Medical Biochemistry, Max Perutz Labs, Medical University of Vienna, Dr. Bohr-Gasse 9, 1030 Vienna, Austria
| | - Dorothea Anrather
- Mass Spectrometry Facility, Max Perutz Labs, Dr. Bohr-Gasse 9, 1030 Vienna, Austria
| | - Markus Hartl
- Mass Spectrometry Facility, Max Perutz Labs, Dr. Bohr-Gasse 9, 1030 Vienna, Austria
| | - Jean-Marie Sontag
- School of Biomedical Sciences and Pharmacy, The University of Newcastle, Callaghan, NSW 2308, Australia
| | - Estelle Sontag
- School of Biomedical Sciences and Pharmacy, The University of Newcastle, Callaghan, NSW 2308, Australia
| | - Brian E Wadzinski
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Teresa Preglej
- Division of Immunobiology, Institute of Immunology, Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, 1090 Vienna, Austria
| | - Wilfried Ellmeier
- Division of Immunobiology, Institute of Immunology, Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, 1090 Vienna, Austria
| | - Egon Ogris
- Center for Medical Biochemistry, Max Perutz Labs, Medical University of Vienna, Dr. Bohr-Gasse 9, 1030 Vienna, Austria.
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12
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Specificity determinants of phosphoprotein phosphatases controlling kinetochore functions. Essays Biochem 2021; 64:325-336. [PMID: 32501472 DOI: 10.1042/ebc20190065] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 05/11/2020] [Accepted: 05/14/2020] [Indexed: 12/12/2022]
Abstract
Kinetochores are instrumental for accurate chromosome segregation by binding to microtubules in order to move chromosomes and by delaying anaphase onset through the spindle assembly checkpoint (SAC). Dynamic phosphorylation of kinetochore components is key to control these activities and is tightly regulated by temporal and spatial recruitment of kinases and phosphoprotein phosphatases (PPPs). Here we focus on PP1, PP2A-B56 and PP2A-B55, three PPPs that are important regulators of mitosis. Despite the fact that these PPPs share a very similar active site, they target unique ser/thr phosphorylation sites to control kinetochore function. Specificity is in part achieved by PPPs binding to short linear motifs (SLiMs) that guide their substrate specificity. SLiMs bind to conserved pockets on PPPs and are degenerate in nature, giving rise to a range of binding affinities. These SLiMs control the assembly of numerous substrate specifying complexes and their position and binding strength allow PPPs to target specific phosphorylation sites. In addition, the activity of PPPs is regulated by mitotic kinases and inhibitors, either directly at the activity level or through affecting PPP-SLiM interactions. Here, we discuss recent progress in understanding the regulation of PPP specificity and activity and how this controls kinetochore biology.
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Nasa I, Kettenbach AN. Effects of carboxyl-terminal methylation on holoenzyme function of the PP2A subfamily. Biochem Soc Trans 2020; 48:2015-2027. [PMID: 33125487 PMCID: PMC8380034 DOI: 10.1042/bst20200177] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 09/14/2020] [Accepted: 09/16/2020] [Indexed: 01/07/2023]
Abstract
Phosphoprotein Phosphatases (PPPs) are enzymes highly conserved from yeast and human and catalyze the majority of the serine and threonine dephosphorylation in cells. To achieve substrate specificity and selectivity, PPPs form multimeric holoenzymes consisting of catalytic, structural/scaffolding, and regulatory subunits. For the Protein Phosphatase 2A (PP2A)-subfamily of PPPs, holoenzyme assembly is at least in part regulated by an unusual carboxyl-terminal methyl-esterification, commonly referred to as 'methylation'. Carboxyl-terminal methylation is catalyzed by Leucine carboxyl methyltransferase-1 (LCMT1) that utilizes S-adenosyl-methionine (SAM) as the methyl donor and removed by protein phosphatase methylesterase 1 (PME1). For PP2A, methylation dictates regulatory subunit selection and thereby downstream phosphorylation signaling. Intriguingly, there are four families of PP2A regulatory subunits, each exhibiting different levels of methylation sensitivity. Thus, changes in PP2A methylation stoichiometry alters the complement of PP2A holoenzymes in cells and creates distinct modes of kinase opposition. Importantly, selective inactivation of PP2A signaling through the deregulation of methylation is observed in several diseases, most prominently Alzheimer's disease (AD). In this review, we focus on how carboxyl-terminal methylation of the PP2A subfamily (PP2A, PP4, and PP6) regulates holoenzyme function and thereby phosphorylation signaling, with an emphasis on AD.
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Affiliation(s)
- Isha Nasa
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth College, Hanover, NH, U.S.A
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center at Dartmouth, Lebanon, NH, U.S.A
| | - Arminja N Kettenbach
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth College, Hanover, NH, U.S.A
- Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center at Dartmouth, Lebanon, NH, U.S.A
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