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Calabrese G, Molzahn C, Mayor T. Protein interaction networks in neurodegenerative diseases: from physiological function to aggregation. J Biol Chem 2022; 298:102062. [PMID: 35623389 PMCID: PMC9234719 DOI: 10.1016/j.jbc.2022.102062] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Revised: 04/26/2022] [Accepted: 05/18/2022] [Indexed: 11/25/2022] Open
Abstract
The accumulation of protein inclusions is linked to many neurodegenerative diseases that typically develop in older individuals, due to a combination of genetic and environmental factors. In rare familial neurodegenerative disorders, genes encoding for aggregation-prone proteins are often mutated. While the underlying mechanism leading to these diseases still remains to be fully elucidated, efforts in the past 20 years revealed a vast network of protein–protein interactions that play a major role in regulating the aggregation of key proteins associated with neurodegeneration. Misfolded proteins that can oligomerize and form insoluble aggregates associate with molecular chaperones and other elements of the proteolytic machineries that are the frontline workers attempting to protect the cells by promoting clearance and preventing aggregation. Proteins that are normally bound to aggregation-prone proteins can become sequestered and mislocalized in protein inclusions, leading to their loss of function. In contrast, mutations, posttranslational modifications, or misfolding of aggregation-prone proteins can lead to gain of function by inducing novel or altered protein interactions, which in turn can impact numerous essential cellular processes and organelles, such as vesicle trafficking and the mitochondria. This review examines our current knowledge of protein–protein interactions involving several key aggregation-prone proteins that are associated with Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, or amyotrophic lateral sclerosis. We aim to provide an overview of the protein interaction networks that play a central role in driving or mitigating inclusion formation, while highlighting some of the key proteomic studies that helped to uncover the extent of these networks.
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Affiliation(s)
- Gaetano Calabrese
- Michael Smith Laboratories, University of British Columbia, V6T 1Z4 Vancouver BC, Canada.
| | - Cristen Molzahn
- Michael Smith Laboratories, University of British Columbia, V6T 1Z4 Vancouver BC, Canada
| | - Thibault Mayor
- Michael Smith Laboratories, University of British Columbia, V6T 1Z4 Vancouver BC, Canada.
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2
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Sell GL, Xin W, Cook EK, Zbinden MA, Schaffer TB, O'Meally RN, Cole RN, Margolis SS. Deleting a UBE3A substrate rescues impaired hippocampal physiology and learning in Angelman syndrome mice. Sci Rep 2021; 11:19414. [PMID: 34593829 PMCID: PMC8484563 DOI: 10.1038/s41598-021-97898-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Accepted: 08/30/2021] [Indexed: 11/09/2022] Open
Abstract
In humans, loss-of-function mutations in the UBE3A gene lead to the neurodevelopmental disorder Angelman syndrome (AS). AS patients have severe impairments in speech, learning and memory, and motor coordination, for which there is currently no treatment. In addition, UBE3A is duplicated in > 1-2% of patients with autism spectrum disorders-a further indication of the significant role it plays in brain development. Altered expression of UBE3A, an E3 ubiquitin ligase, is hypothesized to lead to impaired levels of its target proteins, but identifying the contribution of individual UBE3A targets to UBE3A-dependent deficits remains of critical importance. Ephexin5 is a putative UBE3A substrate that has restricted expression early in development, regulates synapse formation during hippocampal development, and is abnormally elevated in AS mice, modeled by maternally-derived Ube3a gene deletion. Here, we report that Ephexin5 can be directly ubiquitylated by UBE3A. Furthermore, removing Ephexin5 from AS mice specifically rescued hippocampus-dependent behaviors, CA1 physiology, and deficits in dendritic spine number. Our findings identify Ephexin5 as a key driver of hippocampal dysfunction and related behavioral deficits in AS mouse models. These results demonstrate the exciting potential of targeting Ephexin5, and possibly other UBE3A substrates, to improve symptoms of AS and other UBE3A-related developmental disorders.
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Affiliation(s)
- Gabrielle L Sell
- Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Wood Basic Science Building Room 517, 725 N. Wolfe St., Baltimore, MD, 21205, USA.
- Solomon H. Snyder Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.
- Center for Neuroscience, University of California-Davis, One Shields Avenue, Davis, CA, 95616, USA.
| | - Wendy Xin
- Solomon H. Snyder Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
- Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, 21224, USA
- Department of Neurology and the Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA, 94158, USA
| | - Emily K Cook
- Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Wood Basic Science Building Room 517, 725 N. Wolfe St., Baltimore, MD, 21205, USA
| | - Mark A Zbinden
- Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Wood Basic Science Building Room 517, 725 N. Wolfe St., Baltimore, MD, 21205, USA
- Human Metabolome Technologies America, Inc., Boston, MA, 02134, USA
| | - Thomas B Schaffer
- Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Wood Basic Science Building Room 517, 725 N. Wolfe St., Baltimore, MD, 21205, USA
- NextCure Inc., Beltsville, MD, 20705, USA
| | - Robert N O'Meally
- Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Wood Basic Science Building Room 517, 725 N. Wolfe St., Baltimore, MD, 21205, USA
- Mass Spectrometry and Proteomics Facility, The Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Robert N Cole
- Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Wood Basic Science Building Room 517, 725 N. Wolfe St., Baltimore, MD, 21205, USA
- Mass Spectrometry and Proteomics Facility, The Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Seth S Margolis
- Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Wood Basic Science Building Room 517, 725 N. Wolfe St., Baltimore, MD, 21205, USA.
- Solomon H. Snyder Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.
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3
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Kim JY, Kim KM, Yang JH, Cho SS, Kim SJ, Park SJ, Ahn SG, Lee GH, Yang JW, Lim SC, Kang KW, Ki SH. Induction of E6AP by microRNA-302c dysregulation inhibits TGF-β-dependent fibrogenesis in hepatic stellate cells. Sci Rep 2020. [PMID: 31949242 DOI: 10.1038/s41598-019-57322-w.] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Hepatic stellate cells (HSCs) are essential for liver fibrosis. E6 associated protein (E6AP) is one of the E3-ubiquitin-protein ligase and has been studied in proliferation and cellular stress. Currently, no information is available on the role of E6AP on transforming growth factor-β (TGF-β) signaling and hepatic fibrogenesis. This study examined whether E6AP is overexpressed in activated HSCs, and if so, its effect on hepatic fibrogenesis and the molecular mechanism. E6AP was expressed higher in HSCs than hepatocytes, and was up-regulated in activated HSCs, HSCs from the livers of carbon tetrachloride-injected mice, or TGF-β-treated LX-2 cells. The TGF-β-mediated E6AP up-regulation was not due to altered mRNA level nor protein stability. Thus, we performed microRNA (miRNA, miR) analysis and found that miR-302c was dysregulated in TGF-β-treated LX-2 cells or activated primary HSCs. We revealed that miR-302c was a modulator of E6AP. E6AP overexpression inhibited TGF-β-induced expression of plasminogen activator inhibitor-1 in LX-2 cells, albeit it was independent of Smad pathway. Additionally, E6AP inhibited TGF-β-mediated phosphorylation of mitogen-activated protein kinases. To conclude, E6AP overexpression due to decreased miR-302c in HSCs attenuated hepatic fibrogenesis through inhibition of the TGF-β-induced mitogen-activated protein kinase signaling pathway, implying that E6AP and other molecules may contribute to protection against liver fibrosis.
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Affiliation(s)
- Ji Young Kim
- College of Pharmacy, Chosun University, Gwangju, 61452, Republic of Korea
| | - Kyu Min Kim
- College of Pharmacy, Chosun University, Gwangju, 61452, Republic of Korea
| | - Ji Hye Yang
- College of Pharmacy, Chosun University, Gwangju, 61452, Republic of Korea.,College of Korean Medicine, Dongshin University, Naju, Jeollanam-do, 58245, Republic of Korea
| | - Sam Seok Cho
- College of Pharmacy, Chosun University, Gwangju, 61452, Republic of Korea
| | - Seung Jung Kim
- College of Pharmacy, Chosun University, Gwangju, 61452, Republic of Korea
| | - Su Jung Park
- College of Pharmacy, Chosun University, Gwangju, 61452, Republic of Korea
| | - Sang-Gun Ahn
- Department of Pathology, College of Dentistry, Chosun University, Gwangju, 61452, Republic of Korea
| | - Gum Hwa Lee
- College of Pharmacy, Chosun University, Gwangju, 61452, Republic of Korea
| | - Jin Won Yang
- College of Pharmacy, Woosuk University, Wanju, Jeonbuk, 55338, Republic of Korea
| | - Sung Chul Lim
- College of Medicine, Chosun University, Gwangju, 61452, Republic of Korea
| | - Keon Wook Kang
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul, 08826, Republic of Korea
| | - Sung Hwan Ki
- College of Pharmacy, Chosun University, Gwangju, 61452, Republic of Korea.
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4
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Induction of E6AP by microRNA-302c dysregulation inhibits TGF-β-dependent fibrogenesis in hepatic stellate cells. Sci Rep 2020; 10:444. [PMID: 31949242 PMCID: PMC6965100 DOI: 10.1038/s41598-019-57322-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Accepted: 12/27/2019] [Indexed: 12/13/2022] Open
Abstract
Hepatic stellate cells (HSCs) are essential for liver fibrosis. E6 associated protein (E6AP) is one of the E3-ubiquitin-protein ligase and has been studied in proliferation and cellular stress. Currently, no information is available on the role of E6AP on transforming growth factor-β (TGF-β) signaling and hepatic fibrogenesis. This study examined whether E6AP is overexpressed in activated HSCs, and if so, its effect on hepatic fibrogenesis and the molecular mechanism. E6AP was expressed higher in HSCs than hepatocytes, and was up-regulated in activated HSCs, HSCs from the livers of carbon tetrachloride-injected mice, or TGF-β-treated LX-2 cells. The TGF-β-mediated E6AP up-regulation was not due to altered mRNA level nor protein stability. Thus, we performed microRNA (miRNA, miR) analysis and found that miR-302c was dysregulated in TGF-β-treated LX-2 cells or activated primary HSCs. We revealed that miR-302c was a modulator of E6AP. E6AP overexpression inhibited TGF-β-induced expression of plasminogen activator inhibitor-1 in LX-2 cells, albeit it was independent of Smad pathway. Additionally, E6AP inhibited TGF-β-mediated phosphorylation of mitogen-activated protein kinases. To conclude, E6AP overexpression due to decreased miR-302c in HSCs attenuated hepatic fibrogenesis through inhibition of the TGF-β-induced mitogen-activated protein kinase signaling pathway, implying that E6AP and other molecules may contribute to protection against liver fibrosis.
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5
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Stankovic-Valentin N, Melchior F. Control of SUMO and Ubiquitin by ROS: Signaling and disease implications. Mol Aspects Med 2018; 63:3-17. [PMID: 30059710 DOI: 10.1016/j.mam.2018.07.002] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 05/23/2018] [Accepted: 07/27/2018] [Indexed: 01/06/2023]
Abstract
Reversible post-translational modifications (PTMs) ensure rapid signal transmission from sensors to effectors. Reversible modification of proteins by the small proteins Ubiquitin and SUMO are involved in virtually all cellular processes and can modify thousands of proteins. Ubiquitination or SUMOylation is the reversible attachment of these modifiers to lysine residues of a target via isopeptide bond formation. These modifications require ATP and an enzymatic cascade composed of three classes of proteins: E1 activating enzymes, E2 conjugating enzymes and E3 ligases. The reversibility of the modification is ensured by specific isopeptidases. E1 and E2 enzymes, some E3 ligases and most isopeptidases have catalytic cysteine residues, which make them potentially susceptible for oxidation. Indeed, an increasing number of examples reveal regulation of ubiquitination and SUMOylation by reactive oxygen species, both in the context of redox signaling and in severe oxidative stress. Importantly, ubiquitination and SUMOylation play essential roles in the regulation of ROS homeostasis, participating in the control of ROS production and clearance. In this review, we will discuss the interplay between ROS homeostasis, Ubiquitin and SUMO pathways and the implications for the oxidative stress response and cell signaling.
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Affiliation(s)
- Nicolas Stankovic-Valentin
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), DKFZ - ZMBH Alliance, Heidelberg, Germany.
| | - Frauke Melchior
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), DKFZ - ZMBH Alliance, Heidelberg, Germany.
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Gulati T, Huang C, Caramia F, Raghu D, Paul PJ, Goode RJA, Keam SP, Williams SG, Haupt S, Kleifeld O, Schittenhelm RB, Gamell C, Haupt Y. Proteotranscriptomic Measurements of E6-Associated Protein (E6AP) Targets in DU145 Prostate Cancer Cells. Mol Cell Proteomics 2018; 17:1170-1183. [PMID: 29463595 DOI: 10.1074/mcp.ra117.000504] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Revised: 02/18/2018] [Indexed: 11/06/2022] Open
Abstract
Prostate cancer is a common cause of cancer-related death in men. E6AP (E6-Associated Protein), an E3 ubiquitin ligase and a transcription cofactor, is elevated in a subset of prostate cancer patients. Genetic manipulations of E6AP in prostate cancer cells expose a role of E6AP in promoting growth and survival of prostate cancer cells in vitro and in vivo However, the effect of E6AP on prostate cancer cells is broad and it cannot be explained fully by previously identified tumor suppressor targets of E6AP, promyelocytic leukemia protein and p27. To explore additional players that are regulated downstream of E6AP, we combined a transcriptomic and proteomic approach. We identified and quantified 16,130 transcripts and 7,209 proteins in castration resistant prostate cancer cell line, DU145. A total of 2,763 transcripts and 308 proteins were significantly altered on knockdown of E6AP. Pathway analyses supported the known phenotypic effects of E6AP knockdown in prostate cancer cells and in parallel exposed novel potential links of E6AP with cancer metabolism, DNA damage repair and immune response. Changes in expression of the top candidates were confirmed using real-time polymerase chain reaction. Of these, clusterin, a stress-induced chaperone protein, commonly deregulated in prostate cancer, was pursued further. Knockdown of E6AP resulted in increased clusterin transcript and protein levels in vitro and in vivo Concomitant knockdown of E6AP and clusterin supported the contribution of clusterin to the phenotype induced by E6AP. Overall, results from this study provide insight into the potential biological pathways controlled by E6AP in prostate cancer cells and identifies clusterin as a novel target of E6AP.
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Affiliation(s)
- Twishi Gulati
- From the ‡The Sir Peter MacCallum Department of Oncology, The University of Melbourne, Victoria, Australia.,§Tumor Suppression Laboratory, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Cheng Huang
- ¶Monash Biomedical Proteomics Facility, Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia
| | - Franco Caramia
- §Tumor Suppression Laboratory, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Dinesh Raghu
- From the ‡The Sir Peter MacCallum Department of Oncology, The University of Melbourne, Victoria, Australia.,§Tumor Suppression Laboratory, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Piotr J Paul
- From the ‡The Sir Peter MacCallum Department of Oncology, The University of Melbourne, Victoria, Australia.,§Tumor Suppression Laboratory, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Robert J A Goode
- ¶Monash Biomedical Proteomics Facility, Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia
| | - Simon P Keam
- §Tumor Suppression Laboratory, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Scott G Williams
- ‖Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Sue Haupt
- From the ‡The Sir Peter MacCallum Department of Oncology, The University of Melbourne, Victoria, Australia.,§Tumor Suppression Laboratory, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Oded Kleifeld
- **Department of Biology, Technion-Israel Institute of Technology, Haifa, Israel
| | - Ralf B Schittenhelm
- ¶Monash Biomedical Proteomics Facility, Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia
| | - Cristina Gamell
- From the ‡The Sir Peter MacCallum Department of Oncology, The University of Melbourne, Victoria, Australia.,§Tumor Suppression Laboratory, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Ygal Haupt
- From the ‡The Sir Peter MacCallum Department of Oncology, The University of Melbourne, Victoria, Australia; .,§Tumor Suppression Laboratory, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia.,‡‡Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia.,§§Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Victoria, Australia.,¶¶Department of Pathology, The University of Melbourne, Melbourne, Victoria, Australia
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7
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Webster E, Cho MT, Alexander N, Desai S, Naidu S, Bekheirnia MR, Lewis A, Retterer K, Juusola J, Chung WK. De novo PHIP-predicted deleterious variants are associated with developmental delay, intellectual disability, obesity, and dysmorphic features. Cold Spring Harb Mol Case Stud 2017; 2:a001172. [PMID: 27900362 PMCID: PMC5111011 DOI: 10.1101/mcs.a001172] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Using whole-exome sequencing, we have identified novel de novo heterozygous pleckstrin homology domain-interacting protein (PHIP) variants that are predicted to be deleterious, including a frameshift deletion, in two unrelated patients with common clinical features of developmental delay, intellectual disability, anxiety, hypotonia, poor balance, obesity, and dysmorphic features. A nonsense mutation in PHIP has previously been associated with similar clinical features. Patients with microdeletions of 6q14.1, including PHIP, have a similar phenotype of developmental delay, intellectual disability, hypotonia, and obesity, suggesting that the phenotype of our patients is a result of loss-of-function mutations. PHIP produces multiple protein products, such as PHIP1 (also known as DCAF14), PHIP, and NDRP. PHIP1 is one of the multiple substrate receptors of the proteolytic CUL4-DDB1 ubiquitin ligase complex. CUL4B deficiency has been associated with intellectual disability, central obesity, muscle wasting, and dysmorphic features. The overlapping phenotype associated with CUL4B deficiency suggests that PHIP mutations cause disease through disruption of the ubiquitin ligase pathway.
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Affiliation(s)
- Emily Webster
- Department of Pediatrics, Columbia University Medical Center, New York, New York 10032, USA
| | | | | | - Sonal Desai
- Kennedy Krieger Institute, Baltimore, Maryland 21205, USA
| | - Sakkubai Naidu
- Kennedy Krieger Institute, Baltimore, Maryland 21205, USA
| | - Mir Reza Bekheirnia
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Andrea Lewis
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
| | | | | | - Wendy K Chung
- Department of Pediatrics, Columbia University Medical Center, New York, New York 10032, USA;; Department of Medicine, Columbia University Medical Center, New York, New York 10032, USA
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Kapoor I, Kanaujiya J, Kumar Y, Thota JR, Bhatt MLB, Chattopadhyay N, Sanyal S, Trivedi AK. Proteomic discovery of MNT as a novel interacting partner of E3 ubiquitin ligase E6AP and a key mediator of myeloid differentiation. Oncotarget 2016; 7:7640-56. [PMID: 26506232 PMCID: PMC4884944 DOI: 10.18632/oncotarget.6156] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2015] [Accepted: 09/30/2015] [Indexed: 12/31/2022] Open
Abstract
Perturbed stability of regulatory proteins is a major cause of transformations leading to cancer, including several leukemia subtypes. Here, for the first time we demonstrate that E6-associated protein (E6AP), an E3 ubiquitin ligase negatively targets MAX binding protein MNT for ubiquitin-mediated proteasome degradation and impedes ATRA mediated myeloid cell differentiation. MNT is a member of the Myc/Max/Mad network of transcription factor that regulates cell proliferation, differentiation, cellular transformation and tumorigenesis. Wild-type E6AP promoted proteasome dependent degradation of MNT, while catalytically inactive E6AP having cysteine replaced with alanine at amino-acid 843 position (E6APC843A) rather stabilized it. Further, these proteins physically associated with each other both in non-myeloid (HEK293T) and myeloid cells. MNT overexpression induced G0-G1 growth arrest and promoted myeloid differentiation while its knockdown mitigated even ATRA induced differentiation suggesting MNT to be crucial for myeloid differentiation. We further showed that ATRA inhibited E6AP and stabilized MNT expression by protecting it from E6AP mediated ubiquitin-proteasome degradation. Notably, E6AP knockdown in HL60 cells restored MNT expression and promoted myeloid differentiation. Taken together, our data demonstrated that E6AP negatively regulates granulocytic differentiation by targeting MNT for degradation which is required for growth arrest and subsequent myeloid differentiation by various differentiation inducing agents.
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Affiliation(s)
- Isha Kapoor
- Biochemistry Division, CSIR-Central Drug Research Institute, Lucknow, UP, India
| | - Jitendra Kanaujiya
- Biochemistry Division, CSIR-Central Drug Research Institute, Lucknow, UP, India
| | - Yogesh Kumar
- Biochemistry Division, CSIR-Central Drug Research Institute, Lucknow, UP, India
| | | | - Madan L B Bhatt
- Department of Radiotherapy, King George's Medical University, Lucknow, UP, India
| | - Naibedya Chattopadhyay
- Division of Endocrinology and Center for Research in Anabolic Skeletal Targets in Health and Illness (ASTHI), CSIR-Central Drug Research Institute (CSIR-CDRI), Lucknow, UP, India
| | - Sabyasachi Sanyal
- Biochemistry Division, CSIR-Central Drug Research Institute, Lucknow, UP, India
| | - Arun Kumar Trivedi
- Biochemistry Division, CSIR-Central Drug Research Institute, Lucknow, UP, India
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9
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Kuslansky Y, Sominsky S, Jackman A, Gamell C, Monahan BJ, Haupt Y, Rosin-Arbesfeld R, Sherman L. Ubiquitin ligase E6AP mediates nonproteolytic polyubiquitylation of β-catenin independent of the E6 oncoprotein. J Gen Virol 2016; 97:3313-3330. [DOI: 10.1099/jgv.0.000624] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Affiliation(s)
- Yael Kuslansky
- Department of Clinical Microbiology and Immunology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Sophia Sominsky
- Department of Clinical Microbiology and Immunology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Anna Jackman
- Department of Clinical Microbiology and Immunology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Cristina Gamell
- Research Division, The Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville 3010, Victoria, Australia
| | - Brendon J. Monahan
- Division of Systems Biology and Personalized Medicine, Walter and Eliza Hall Institute of Medical Research, Parkville 3052, Victoria, Australia
| | - Ygal Haupt
- Research Division, The Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville 3010, Victoria, Australia
| | - Rina Rosin-Arbesfeld
- Department of Clinical Microbiology and Immunology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Levana Sherman
- Department of Clinical Microbiology and Immunology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
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Upadhyay A, Amanullah A, Chhangani D, Mishra R, Mishra A. Selective multifaceted E3 ubiquitin ligases barricade extreme defense: Potential therapeutic targets for neurodegeneration and ageing. Ageing Res Rev 2015; 24:138-59. [PMID: 26247845 DOI: 10.1016/j.arr.2015.07.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2015] [Revised: 06/24/2015] [Accepted: 07/30/2015] [Indexed: 12/24/2022]
Abstract
Efficient and regular performance of Ubiquitin Proteasome System and Autophagy continuously eliminate deleterious accumulation of nonnative protiens. In cellular quality control system, E3 ubiquitin ligases are significant employees for defense mechanism against abnormal toxic proteins. Few findings indicate that lack of functions of E3 ubiquitin ligases can be a causative factor of neurodevelopmental disorders, neurodegeneration, cancer and ageing. However, the detailed molecular pathomechanism implying E3 ubiquitin ligases in cellular functions in multifactorial disease conditions are not well understood. This article systematically represents the unique characteristics, molecular nature, and recent developments in the knowledge of neurobiological functions of few crucial E3 ubiquitin ligases. Here, we review recent literature on the roles of E6-AP, HRD1 and ITCH E3 ubiquitin ligases in the neuro-pathobiological mechanisms, with precise focus on the processes of neurodegeneration, and thereby propose new lines of potential targets for therapeutic interventions.
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Abstract
In this review we summarize the clinical and genetic aspects of Angelman syndrome (AS), its molecular and cellular underpinnings, and current treatment strategies. AS is a neurodevelopmental disorder characterized by severe cognitive disability, motor dysfunction, speech impairment, hyperactivity, and frequent seizures. AS is caused by disruption of the maternally expressed and paternally imprinted UBE3A, which encodes an E3 ubiquitin ligase. Four mechanisms that render the maternally inherited UBE3A nonfunctional are recognized, the most common of which is deletion of the maternal chromosomal region 15q11-q13. Remarkably, duplication of the same chromosomal region is one of the few characterized persistent genetic abnormalities associated with autistic spectrum disorder, occurring in >1-2% of all cases of autism spectrum disorder. While the overall morphology of the brain and connectivity of neural projections appear largely normal in AS mouse models, major functional defects are detected at the level of context-dependent learning, as well as impaired maturation of hippocampal and neocortical circuits. While these findings demonstrate a crucial role for ubiquitin protein ligase E3A in synaptic development, the mechanisms by which deficiency of ubiquitin protein ligase E3A leads to AS pathophysiology in humans remain poorly understood. However, recent efforts have shown promise in restoring functions disrupted in AS mice, renewing hope that an effective treatment strategy can be found.
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Affiliation(s)
- Seth S Margolis
- Department of Biological Chemistry, The Johns Hopkins University School of Medicine, 725 N. Wolfe St., Baltimore, MD, 21205, USA,
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12
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Ronchi VP, Klein JM, Edwards DJ, Haas AL. The active form of E6-associated protein (E6AP)/UBE3A ubiquitin ligase is an oligomer. J Biol Chem 2013; 289:1033-48. [PMID: 24273172 DOI: 10.1074/jbc.m113.517805] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Employing 125I-polyubiquitin chain formation as a functional readout of ligase activity, biochemical and biophysical evidence demonstrates that catalytically active E6-associated protein (E6AP)/UBE3A is an oligomer. Based on an extant structure previously discounted as an artifact of crystal packing forces, we propose that the fully active form of E6AP is a trimer, analysis of which reveals a buried surface of 7508Å2 and radially symmetric interacting residues that are conserved within the Hect (homologous to E6AP C terminus) ligase superfamily. An absolutely conserved interaction between Phe(727) and a hydrophobic pocket present on the adjacent subunit is critical for trimer stabilization because mutation disrupts the oligomer and decreases kcat 62-fold but fails to affect E2 ubiquitin binding or subsequent formation of the Hect domain Cys(820) ubiquitin thioester catalytic intermediate. Exogenous N-acetylphenylalanylamide reversibly antagonizes Phe(727)-dependent trimer formation and catalytic activity (Ki12 mM), as does a conserved-helical peptide corresponding to residues 474–490 of E6A Pisoform 1 (Ki22M) reported to bind the hydrophobic pocket of other Hect ligases, presumably blocking Phe(727) intercalation and trimer formation. Conversely, oncogenic human papillomavirus-16/18 E6 protein significantly enhances E6AP catalytic activity by promoting trimer formation (Kactivation 1.5 nM) through the ability of E6 to form homodimers. Recombinant E6 protein additionally rescues the kcat defect of the Phe(727) mutation and that of a specific loss-of-function Angelman syndrome mutation that promotes trimer destabilization. The present findings codify otherwise disparate observations regarding the mechanism of E6AP and related Hect ligases in addition to suggesting therapeutic approaches for modulating ligase activity.
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13
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Abstract
HECT ubiquitin ligases are key components of the ubiquitin-proteasome system, which is present in all eukaryotes. In this study, the patterns of emergence of HECT genes in plants are described. Phylogenetic and structural data indicate that viridiplantae have six main HECT subfamilies, which arose before the split that separated green algae from the rest of plants. It is estimated that the common ancestor of all plants contained seven HECT genes. Contrary to what happened in animals, the number of HECT genes has been kept quite constant in all lineages, both in chlorophyta and streptophyta, although evolutionary recent duplications are found in some species. Several of the genes found in plants may have originated very early in eukaryotic evolution, given that they have clear similarities, both in sequence and structure, to animal genes. Finally, in Arabidopsis thaliana, we found significant correlations in the expression patterns of HECT genes and some ancient, broadly expressed genes that belong to a different ubiquitin ligase family, called RBR. These results are discussed in the context of the evolution of the gene families required for ubiquitination in plants.
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Affiliation(s)
- Ignacio Marín
- Instituto de Biomedicina de Valencia-Consejo Superior de Investigaciones Científicas (IBV-CSIC), Valencia, Spain.
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14
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Chan AL, Grossman T, Zuckerman V, Campigli Di Giammartino D, Moshel O, Scheffner M, Monahan B, Pilling P, Jiang YH, Haupt S, Schueler-Furman O, Haupt Y. c-Abl phosphorylates E6AP and regulates its E3 ubiquitin ligase activity. Biochemistry 2013; 52:3119-29. [PMID: 23581475 DOI: 10.1021/bi301710c] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
In human papillomavirus (HPV)-infected cells, the p53 tumor suppressor is tightly regulated by the HPV-E6-E6AP complex, which promotes it for proteasomal degradation. We previously demonstrated that c-Abl tyrosine kinase protects p53 from HPV-E6-E6AP complex-mediated ubiquitination and degradation under stress conditions. However, the underlying mechanism was not defined. In this study, we explored the possibility that c-Abl targets E6AP and thereby protects p53. We demonstrated that c-Abl interacts with and phosphorylates E6AP. We determined that the E3 ligase activity of E6AP is impaired in response to phosphorylation by c-Abl. We mapped the phosphorylation site to tyrosine 636 within the HECT catalytic domain of E6AP, and using substitution mutants, we showed that this residue dictates the E3 ligase activity of E6AP, in a substrate-specific manner. On the basis of the crystal structure of the HECT domain of E6AP, we propose a model in which tyrosine 636 plays a regulatory role in the oligomerization of E6AP, which is a process implicated in its E3 ubiquitin ligase activity. Our results suggest that c-Abl protects p53 from HPV-E6-E6AP complex-mediated degradation by phosphorylating E6AP and impairing its E3 ligase activity, thus providing a molecular explanation for the stress-induced protection of p53 in HPV-infected cells.
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Affiliation(s)
- Ai-Leen Chan
- Research Division, The Peter MacCallum Cancer Centre, St. Andrew's Place, East Melbourne 3002, Victoria, Australia
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15
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E6-AP association promotes SOD1 aggresomes degradation and suppresses toxicity. Neurobiol Aging 2013; 34:1310.e11-23. [DOI: 10.1016/j.neurobiolaging.2012.08.016] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Revised: 07/22/2012] [Accepted: 08/22/2012] [Indexed: 12/14/2022]
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16
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The E6AP E3 ubiquitin ligase regulates the cellular response to oxidative stress. Oncogene 2012; 32:3510-9. [DOI: 10.1038/onc.2012.365] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Revised: 06/20/2012] [Accepted: 07/04/2012] [Indexed: 11/09/2022]
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17
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Lochab S, Pal P, Kanaujiya JK, Tripathi SB, Kapoor I, Bhatt MLB, Sanyal S, Behre G, Trivedi AK. Proteomic identification of E6AP as a molecular target of tamoxifen in MCF7 cells. Proteomics 2012; 12:1363-77. [PMID: 22589186 DOI: 10.1002/pmic.201100572] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Tamoxifen (Tam) is most widely used selective estrogen receptor modulator (SERM) for treatment of hormone-responsive breast cancer. Despite being regularly used in clinical therapy for breast cancer since 1971, the mechanism of Tam action remains largely unclear. In order to gain insights into Tam-mediated antibreast cancer actions, we applied 2DE and MS based proteomics approach to identify target proteins of Tam. We identified E6-associated protein, i.e. E6AP (UBE3A) among others to be regulated by Tam that otherwise is upregulated in breast tumors. We confirmed our 2DE finding by immunoblotting and further show that Tam leads to inhibition of E6AP expression presumably by promoting its autoubiquitination, which is coupled with nuclear export and subsequent proteasome-mediated degradation. Furthermore, we show that Tam- and siE6AP-mediated inhibition of E6AP leads to enhanced G0-G1 growth arrest and apoptosis, which is also evident from significant upregulation of cytochrome-c, Bax, p21, and PARP cleavage. Taken together, our data suggest that, Tam-targeted E6AP inhibition is in fact required for Tam-mediated antibreast cancer actions. Thus, E6AP may be a therapeutic target in breast cancer.
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Affiliation(s)
- Savita Lochab
- DTDD Division, CSIR-Central Drug Research Institute, Lucknow, Uttar Pradesh, India
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18
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Abstract
Neoplastic transformation requires the elimination of key tumor suppressors, which may result from E3 ligase-mediated proteasomal degradation. We previously demonstrated a key role for the E3 ubiquitin ligase E6AP in the regulation of promyelocytic leukemia protein (PML) stability and formation of PML nuclear bodies. Here, we report the involvement of the E6AP-PML axis in B-cell lymphoma development. A partial loss of E6AP attenuated Myc-induced B-cell lymphomagenesis. This tumor suppressive action was achieved by the induction of cellular senescence. B-cell lymphomas deficient for E6AP expressed elevated levels of PML and PML-nuclear bodies with a concomitant increase in markers of cellular senescence, including p21, H3K9me3, and p16. Consistently, PML deficiency accelerated the rate of Myc-induced B-cell lymphomagenesis. Importantly, E6AP expression was elevated in ∼ 60% of human Burkitt lymphomas, and down-regulation of E6AP in B-lymphoma cells restored PML expression with a concurrent induction of cellular senescence in these cells. Our findings demonstrate that E6AP-mediated down-regulation of PML-induced senescence is essential for B-cell lymphoma progression. This provides a molecular explanation for the down-regulation of PML observed in non-Hodgkin lymphomas, thereby suggesting a novel therapeutic approach for restoration of tumor suppression in B-cell lymphoma.
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19
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E6AP is required for replicative and oncogene-induced senescence in mouse embryo fibroblasts. Oncogene 2011; 31:2199-209. [DOI: 10.1038/onc.2011.402] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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20
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Kühnle S, Kogel U, Glockzin S, Marquardt A, Ciechanover A, Matentzoglu K, Scheffner M. Physical and functional interaction of the HECT ubiquitin-protein ligases E6AP and HERC2. J Biol Chem 2011; 286:19410-6. [PMID: 21493713 PMCID: PMC3103319 DOI: 10.1074/jbc.m110.205211] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2010] [Revised: 04/04/2011] [Indexed: 11/06/2022] Open
Abstract
Deregulation of the ubiquitin-protein ligase E6AP contributes to the development of the Angelman syndrome and to cervical carcinogenesis suggesting that the activity of E6AP needs to be under tight control. However, how E6AP activity is regulated at the post-translational level under non-pathologic conditions is poorly understood. In this study, we report that the giant protein HERC2, which is like E6AP a member of the HECT family of ubiquitin-protein ligases, binds to E6AP. The interaction is mediated by the RCC1-like domain 2 of HERC2 and a region spanning amino acid residues 150-200 of E6AP. Furthermore, we provide evidence that HERC2 stimulates the ubiquitin-protein ligase activity of E6AP in vitro and within cells and that this stimulatory effect does not depend on the ubiquitin-protein ligase activity of HERC2. Thus, the data obtained indicate that HERC2 acts as a regulator of E6AP.
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Affiliation(s)
- Simone Kühnle
- From the Department of Biology and Konstanz Research School Chemical Biology, and
| | - Ulrike Kogel
- From the Department of Biology and Konstanz Research School Chemical Biology, and
| | - Sandra Glockzin
- From the Department of Biology and Konstanz Research School Chemical Biology, and
| | - Andreas Marquardt
- Proteomics Facility, University of Konstanz, 78457 Konstanz, Germany and
| | - Aaron Ciechanover
- the Cancer and Vascular Biology Research Center, The Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa 31096, Israel
| | | | - Martin Scheffner
- From the Department of Biology and Konstanz Research School Chemical Biology, and
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21
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Nasu J, Murakami K, Miyagawa S, Yamashita R, Ichimura T, Wakita T, Hotta H, Miyamura T, Suzuki T, Satoh T, Shoji I. E6AP ubiquitin ligase mediates ubiquitin-dependent degradation of peroxiredoxin 1. J Cell Biochem 2011; 111:676-85. [PMID: 20589759 DOI: 10.1002/jcb.22752] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
E6-associated protein (E6AP) is a cellular ubiquitin protein ligase that mediates ubiquitylation and degradation of tumor suppressor p53 in conjunction with the high-risk human papillomavirus E6 protein. We previously reported that E6AP targets annexin A1 protein for ubiquitin-dependent proteasomal degradation. To gain a better understanding of the physiological function of E6AP, we have been seeking to identify novel substrates of E6AP. Here, we identified peroxiredoxin 1 (Prx1) as a novel E6AP-binding protein using a tandem affinity purification procedure coupled with mass spectrometry. Prx1 is a 25-kDa member of the Prx family, a ubiquitous family of antioxidant peroxidases that regulate many cellular processes through intracellular oxidative signal transduction pathways. Immunoprecipitation analysis showed that E6AP binds Prx1 in vivo. Pull-down experiments showed that E6AP binds Prx1 in vitro. Ectopic expression of E6AP enhanced the degradation of Prx1 in vivo. In vivo and in vitro ubiquitylation assays revealed that E6AP promoted polyubiquitylation of Prx1. RNAi-mediated downregulation of endogenous E6AP increased the level of endogenous Prx1 protein. Taken together, our data suggest that E6AP mediates the ubiquitin-dependent proteasomal degradation of Prx1. Our findings raise a possibility that E6AP may play a role in regulating Prx1-dependent intracellular oxidative signal transduction pathways.
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Affiliation(s)
- Junichi Nasu
- Department of Virology II, National Institute of Infectious Diseases, Shinjuku-ku, Tokyo, Japan
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Nedd4 and Nedd4-2: closely related ubiquitin-protein ligases with distinct physiological functions. Cell Death Differ 2010; 17:68-77. [PMID: 19557014 DOI: 10.1038/cdd.2009.84] [Citation(s) in RCA: 172] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The Nedd4 (neural precursor cell-expressed developmentally downregulated gene 4) family of ubiquitin ligases (E3s) is characterized by a distinct modular domain architecture, with each member consisting of a C2 domain, 2-4 WW domains, and a HECT-type ligase domain. Of the nine mammalian members of this family, Nedd4 and its close relative, Nedd4-2, represent the ancestral ligases with strong similarity to the yeast, Rsp5. In Saccharomyces cerevisiae Rsp5 has a key role in regulating the trafficking, sorting, and degradation of a large number of proteins in multiple cellular compartments. However, in mammals the Nedd4 family members, including Nedd4 and Nedd4-2, appear to have distinct functions, thereby suggesting that these E3s target specific proteins for ubiquitylation. In this article we focus on the biology and emerging functions of Nedd4 and Nedd4-2, and review recent in vivo studies on these E3s.
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23
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Marín I. Animal HECT ubiquitin ligases: evolution and functional implications. BMC Evol Biol 2010; 10:56. [PMID: 20175895 PMCID: PMC2837046 DOI: 10.1186/1471-2148-10-56] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2009] [Accepted: 02/22/2010] [Indexed: 11/10/2022] Open
Abstract
Background HECT ubiquitin ligases (HECT E3s) are key components of the eukaryotic ubiquitin-proteasome system and are involved in the genesis of several human diseases. In this study, I analyze the patterns of diversification of HECT E3s since animals emerged in order to provide the right framework to understand the functional data available for proteins of this family. Results I show that the current classification of HECT E3s into three groups (NEDD4-like E3s, HERCs and single-HECT E3s) is fundamentally incorrect. First, the existence of a "Single-HECT E3s" group is not supported by phylogenetic analyses. Second, the HERC proteins must be divided into two subfamilies (Large HERCs, Small HERCs) that are evolutionarily very distant, their structural similarity being due to convergence and not to a common origin. Sequence and structural analyses show that animal HECT E3s can be naturally classified into 16 subfamilies. Almost all of them appeared either before animals originated or in early animal evolution. More recently, multiple gene losses have occurred independently in some lineages (nematodes, insects, urochordates), the same groups that have also lost genes of another type of E3s (RBR family). Interestingly, the emergence of some animal HECT E3s precedes the origin of key cellular systems that they regulate (TGF-β and EGF signal transduction pathways; p53 family of transcription factors) and it can be deduced that distantly related HECT proteins have been independently co-opted to perform similar roles. This may contribute to explain why distantly related HECT E3s are involved in the genesis of multiple types of cancer. Conclusions The complex evolutionary history of HECT ubiquitin ligases in animals has been deciphered. The most appropriate model animals to study them and new theoretical and experimental lines of research are suggested by these results.
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Affiliation(s)
- Ignacio Marín
- Instituto de Biomedicina de Valencia, Consejo Superior de Investigaciones Científicas (IBV-CSIC), Valencia, Spain.
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Emerging roles of the ubiquitin proteasome system in nuclear hormone receptor signaling. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 87:117-35. [PMID: 20374703 DOI: 10.1016/s1877-1173(09)87004-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Nuclear receptor (NR)-mediated transcription is intimately tied to the ubiquitin proteasome system (UPS). The UPS targets numerous NR and coregulator proteins, regulating their stability and altering their transcriptional activities through the posttranslational placement of ubiquitin marks on them. Differences in the manner in which ubiquitin is attached to target proteins or itself have distinct regulatory consequences. Protein monoubiquitination, polyubiquitination, the site of ubiquitin attachment to a target protein, and the type of polyubiquitin chain linkage all lead to different biological outcomes and have an important regulatory function in NR-mediated transcription. Consistent with its role in protein degradation, the UPS is able to limit the biological actions of both NRs and coregulators by reducing their protein concentrations in the cell. However, in spite of its destructive capabilities, the UPS can play a positive role in facilitating NR-mediated transcription as well. In addition, ubiquitin-like modifications such as SUMOylation also modify and regulate NRs and coregulators. The UPS forms a key biological system that underlies a sophisticated postranslational regulatory scheme from which complex and dynamic regulation of NR-mediated transcription can occur.
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25
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Much to know about proteolysis: intricate proteolytic machineries compromise essential cellular functions. Biochem Soc Trans 2008; 36:781-5. [DOI: 10.1042/bst0360781] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Proteolysis has traditionally been considered as a radical way to terminate the function of a protein. However, protein destruction also is the starting point for many processes as they can only occur when the way has been cleared for the action of other proteins. Protein destruction can occur virtually in all compartments and organelles of the cell, associated with cell membranes or large protein complexes, it determines subcellular partitioning, association with positive or negative regulators which conditions the action of many critical cellular factors. The third intracellular proteolysis meeting held by the University La Laguna, Canary Islands, Spain, included speakers working with some of the most important proteolytic systems present in higher eukaryotes, such as the UPS (ubiquitin–proteasome system) and autophagy. Owing to the fact that these pathways directly or indirectly regulate many cell functions, this meeting brought together an audience with a wide range of research interests, including genetic, cell biological, biochemical and structural aspects of protein degradation. Some of these topics inspired interesting discussions and a significant number of these are developed in the issues reviewed herein.
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