1
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Shan Z, Rivero-Gamez A, Lyumkis D, Horton NC. Two-metal ion mechanism of DNA cleavage by activated, filamentous SgrAI. J Biol Chem 2024; 300:107576. [PMID: 39009341 PMCID: PMC11367474 DOI: 10.1016/j.jbc.2024.107576] [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: 05/03/2024] [Revised: 06/21/2024] [Accepted: 07/09/2024] [Indexed: 07/17/2024] Open
Abstract
Enzymes that form filamentous assemblies with modulated enzymatic activities have gained increasing attention in recent years. SgrAI is a sequence specific type II restriction endonuclease that forms polymeric filaments with accelerated DNA cleavage activity and expanded DNA sequence specificity. Prior studies have suggested a mechanistic model linking the structural changes accompanying SgrAI filamentation to its accelerated DNA cleavage activity. In this model, the conformational changes that are specific to filamentous SgrAI maximize contacts between different copies of the enzyme within the filament and create a second divalent cation binding site in each subunit, which in turn facilitates the DNA cleavage reaction. However, our understanding of the atomic mechanism of catalysis is incomplete. Herein, we present two new structures of filamentous SgrAI solved using cryo-EM. The first structure, resolved to 3.3 Å, is of filamentous SgrAI containing an active site mutation that is designed to stall the DNA cleavage reaction, which reveals the enzymatic configuration prior to DNA cleavage. The second structure, resolved to 3.1 Å, is of WT filamentous SgrAI containing cleaved substrate DNA, which reveals the enzymatic configuration at the end of the enzymatic cleavage reaction. Both structures contain the phosphate moiety at the cleavage site and the biologically relevant divalent cation cofactor Mg2+ and define how the Mg2+ cation reconfigures during enzymatic catalysis. The data support a model for the activation mechanism that involves binding of a second Mg2+ in the SgrAI active site as a direct result of filamentation induced conformational changes.
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Affiliation(s)
- Zelin Shan
- The Salk Institute of Biological Sciences, La Jolla, California, USA
| | - Andres Rivero-Gamez
- The Salk Institute of Biological Sciences, La Jolla, California, USA; Department of Molecular Biology, School of Biological Sciences, University of California, San Diego La Jolla, California, USA
| | - Dmitry Lyumkis
- The Salk Institute of Biological Sciences, La Jolla, California, USA; Department of Molecular Biology, School of Biological Sciences, University of California, San Diego La Jolla, California, USA.
| | - Nancy C Horton
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona, USA.
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2
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Yin Y, Yu H, Wang X, Hu Q, Liu Z, Luo D, Yang X. Cytoophidia: a conserved yet promising mode of enzyme regulation in nucleotide metabolism. Mol Biol Rep 2024; 51:245. [PMID: 38300325 DOI: 10.1007/s11033-024-09208-y] [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: 10/17/2023] [Accepted: 01/02/2024] [Indexed: 02/02/2024]
Abstract
Nucleotide biosynthesis encompasses both de novo and salvage synthesis pathways, each characterized by significant material and procedural distinctions. Despite these differences, cells with elevated nucleotide demands exhibit a preference for the more intricate de novo synthesis pathway, intricately linked to modes of enzyme regulation. In this study, we primarily scrutinize the biological importance of a conserved yet promising mode of enzyme regulation in nucleotide metabolism-cytoophidia. Cytoophidia, comprising cytidine triphosphate synthase or inosine monophosphate dehydrogenase, is explored across diverse biological models, including yeasts, Drosophila, mice, and human cancer cell lines. Additionally, we delineate potential biomedical applications of cytoophidia. As our understanding of cytoophidia deepens, the roles of enzyme compartmentalization and polymerization in various biochemical processes will unveil, promising profound impacts on both research and the treatment of metabolism-related diseases.
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Affiliation(s)
- Yue Yin
- School of Queen Mary, Jiangxi Medical College, Nanchang University, Jiangxi, China
| | - Huanhuan Yu
- First School of Clinical Medicine, Jiangxi Medical College, Nanchang University, Jiangxi, China
| | - Xinyi Wang
- Thyroid Surgery Center, West China Hospital of Sichuan University, Chengdu, China
| | - Qiaohao Hu
- The 1st Affiliated Hospital, Jiangxi Medical College, Nanchang University, Jiangxi, China
| | - Zhuoqi Liu
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Jiangxi Medical College, Nanchang University, Jiangxi, China
| | - Daya Luo
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Jiangxi Medical College, Nanchang University, Jiangxi, China.
| | - Xiaohong Yang
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Jiangxi Medical College, Nanchang University, Jiangxi, China.
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3
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O'Neill AG, Burrell AL, Zech M, Elpeleg O, Harel T, Edvardson S, Mor-Shaked H, Rippert AL, Nomakuchi T, Izumi K, Kollman JM. Neurodevelopmental disorder mutations in the purine biosynthetic enzyme IMPDH2 disrupt its allosteric regulation. J Biol Chem 2023; 299:105012. [PMID: 37414152 PMCID: PMC10407431 DOI: 10.1016/j.jbc.2023.105012] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 06/23/2023] [Accepted: 06/28/2023] [Indexed: 07/08/2023] Open
Abstract
Inosine 5' monophosphate dehydrogenase (IMPDH) is a critical regulatory enzyme in purine nucleotide biosynthesis that is inhibited by the downstream product GTP. Multiple point mutations in the human isoform IMPDH2 have recently been associated with dystonia and other neurodevelopmental disorders, but the effect of the mutations on enzyme function has not been described. Here, we report the identification of two additional missense variants in IMPDH2 from affected individuals and show that all of the disease-associated mutations disrupt GTP regulation. Cryo-EM structures of one IMPDH2 mutant suggest this regulatory defect arises from a shift in the conformational equilibrium toward a more active state. This structural and functional analysis provides insight into IMPDH2-associated disease mechanisms that point to potential therapeutic approaches and raises new questions about fundamental aspects of IMPDH regulation.
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Affiliation(s)
- Audrey G O'Neill
- Department of Biochemistry, University of Washington, Seattle, Washington, USA
| | - Anika L Burrell
- Department of Biochemistry, University of Washington, Seattle, Washington, USA
| | - Michael Zech
- Institute of Neurogenomics, Helmholtz Zentrum München, Munich, Germany; Institute of Human Genetics, School of Medicine, Technical University of Munich, Munich, Germany
| | - Orly Elpeleg
- Department of Genetics, Hadassah Medical Center, Jerusalem, Israel; Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Tamar Harel
- Department of Genetics, Hadassah Medical Center, Jerusalem, Israel; Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Simon Edvardson
- Alyn Hospital, Hebrew University School of Medicine, Jerusalem, Israel
| | - Hagar Mor-Shaked
- Department of Genetics, Hadassah Medical Center, Jerusalem, Israel; Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Alyssa L Rippert
- Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | - Tomoki Nomakuchi
- Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | - Kosuke Izumi
- Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | - Justin M Kollman
- Department of Biochemistry, University of Washington, Seattle, Washington, USA.
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4
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Alhamad S, Elmasry Y, Uwagboe I, Chekmeneva E, Sands C, Cooper BW, Camuzeaux S, Salam A, Parsons M. B7-H3 Associates with IMPDH2 and Regulates Cancer Cell Survival. Cancers (Basel) 2023; 15:3530. [PMID: 37444640 DOI: 10.3390/cancers15133530] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Revised: 07/03/2023] [Accepted: 07/05/2023] [Indexed: 07/15/2023] Open
Abstract
Lung cancer is one of the most common cancers worldwide, and despite improvements in treatment regimens, patient prognosis remains poor. Lung adenocarcinomas develop from the lung epithelia and understanding how specific genetic and environmental factors lead to oncogenic transformation in these cells is of great importance to define the pathways that contribute to tumorigenesis. The recent rise in the use of immunotherapy to treat different cancers has prompted the exploration of immune modulators in tumour cells that may provide new targets to manipulate this process. Of these, the B7 family of cell surface receptors, which includes PD-1, is of particular interest due to its role in modulating immune cell responses within the tumour microenvironment. B7-H3 (CD276) is one family member that is upregulated in many cancer types and suggested to contribute to tumour-immune interactions. However, the function and ligand(s) for this receptor in normal lung epithelia and the mechanisms through which the overexpression of B7-H3 regulate cancer progression in the absence of immune cell interactions remain unclear. Here, we present evidence that B7-H3 is associated with one of the key rate-limiting metabolic enzymes IMPDH2, and the localisation of this complex is altered in human lung cancer cells that express high levels of B7-H3. Mechanistically, the IMPDH2:B7-H3 complex provides a protective role in cancer cells to escape oxidative stress triggered by chemotherapy, thus leading to cell survival. We further demonstrate that the loss of B7-H3 in cancer cells has no effect on growth or migration in 2D but promotes the expansion of 3D spheroids in an IMPDH2-dependent manner. These findings provide new insights into the B7-H3 function in the metabolic homeostasis of normal and transformed lung cancer cells, and whilst this molecule remains an interesting target for immunotherapy, these findings caution against the use of anti-B7-H3 therapies in certain clinical settings.
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Affiliation(s)
- Salwa Alhamad
- Randall Centre for Cell and Molecular Biophysics, King's College London, Guys Campus, New Hunts House, London SE1 1UL, UK
- Department of Biology, College of Science, Imam Abdulrahman Bin Faisal University, P.O. Box 1982, Dammam 31441, Saudi Arabia
| | - Yassmin Elmasry
- Randall Centre for Cell and Molecular Biophysics, King's College London, Guys Campus, New Hunts House, London SE1 1UL, UK
| | - Isabel Uwagboe
- Randall Centre for Cell and Molecular Biophysics, King's College London, Guys Campus, New Hunts House, London SE1 1UL, UK
| | - Elena Chekmeneva
- National Phenome Centre, Section of Bioanalytical Chemistry, Department of Metabolism, Digestion and Reproduction, Imperial College London, Hammersmith Hospital Campus, IRDB Building, 5th Floor, Du Cane Road, London W12 0NN, UK
| | - Caroline Sands
- National Phenome Centre, Section of Bioanalytical Chemistry, Department of Metabolism, Digestion and Reproduction, Imperial College London, Hammersmith Hospital Campus, IRDB Building, 5th Floor, Du Cane Road, London W12 0NN, UK
| | - Benjamin W Cooper
- National Phenome Centre, Section of Bioanalytical Chemistry, Department of Metabolism, Digestion and Reproduction, Imperial College London, Hammersmith Hospital Campus, IRDB Building, 5th Floor, Du Cane Road, London W12 0NN, UK
| | - Stephane Camuzeaux
- National Phenome Centre, Section of Bioanalytical Chemistry, Department of Metabolism, Digestion and Reproduction, Imperial College London, Hammersmith Hospital Campus, IRDB Building, 5th Floor, Du Cane Road, London W12 0NN, UK
| | - Ash Salam
- National Phenome Centre, Section of Bioanalytical Chemistry, Department of Metabolism, Digestion and Reproduction, Imperial College London, Hammersmith Hospital Campus, IRDB Building, 5th Floor, Du Cane Road, London W12 0NN, UK
| | - Maddy Parsons
- Randall Centre for Cell and Molecular Biophysics, King's College London, Guys Campus, New Hunts House, London SE1 1UL, UK
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5
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O'Neill AG, Burrell AL, Zech M, Elpeleg O, Harel T, Edvardson S, Shaked HM, Rippert AL, Nomakuchi T, Izumi K, Kollman JM. Point mutations in IMPDH2 which cause early-onset neurodevelopmental disorders disrupt enzyme regulation and filament structure. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.15.532669. [PMID: 36993700 PMCID: PMC10055058 DOI: 10.1101/2023.03.15.532669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
Abstract
Inosine 5' monophosphate dehydrogenase (IMPDH) is a critical regulatory enzyme in purine nucleotide biosynthesis that is inhibited by the downstream product GTP. Multiple point mutations in the human isoform IMPDH2 have recently been associated with dystonia and other neurodevelopmental disorders, but the effect of the mutations on enzyme function has not been described. Here, we report identification of two additional affected individuals with missense variants in IMPDH2 and show that all of the disease-associated mutations disrupt GTP regulation. Cryo-EM structures of one IMPDH2 mutant suggest this regulatory defect arises from a shift in the conformational equilibrium toward a more active state. This structural and functional analysis provides insight into IMPDH2-associated disease mechanisms that point to potential therapeutic approaches and raises new questions about fundamental aspects of IMPDH regulation.
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Affiliation(s)
- Audrey G O'Neill
- Department of Biochemistry, University of Washington, Seattle, WA, USA
| | - Anika L Burrell
- Department of Biochemistry, University of Washington, Seattle, WA, USA
| | - Michael Zech
- Institute of Neurogenomics, Helmholtz Zentrum München, 85764 Munich, Germany
- Institute of Human Genetics, School of Medicine, Technical University of Munich, 81675 Munich, Germany
| | - Orly Elpeleg
- Department of Genetics, Hadassah Medical Center, Jerusalem, Israel
- Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Tamar Harel
- Department of Genetics, Hadassah Medical Center, Jerusalem, Israel
- Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Simon Edvardson
- Alyn Hospital, Hebrew University School of Medicine, Jerusalem, Israel
| | - Hagar Mor Shaked
- Department of Genetics, Hadassah Medical Center, Jerusalem, Israel
- Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Alyssa L Rippert
- Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Tomoki Nomakuchi
- Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Kosuke Izumi
- Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Justin M Kollman
- Department of Biochemistry, University of Washington, Seattle, WA, USA
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6
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Meng J, Yang G, Li S, Luo Y, Bai Y, Deng C, Song N, Li M, Zeng X, Hu C. The clinical value of indirect immunofluorescence for screening anti-rods and rings antibodies: A retrospective study of two centers in China. Front Immunol 2022; 13:1007257. [PMID: 36238277 PMCID: PMC9552219 DOI: 10.3389/fimmu.2022.1007257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Accepted: 09/08/2022] [Indexed: 11/22/2022] Open
Abstract
Objective To investigate the distribution and clinical significance of the rods and rings (RR) pattern in various diseases. Methods A total of 169,891 patients in Peking Union Medical College Hospital (PUMCH) and 29,458 patients in Inner Mongolia People’s Hospital (IMPH) from January 2018 to December 2020 were included, and the results of ANA (antinuclear antibodies) and special antibodies were analyzed retrospectively. Results The positive rates of ANA and RR patterns were 34.84%, 0.16% in PUMCH, and 44.73%, 0.23% in IMPH. Anti-RR antibodies mainly appear in adults (≥ 41 years), mostly of low or medium fluorescence titers. Isolated RR patterns were mostly presented (60.30% and 69.12%, respectively), and the RR pattern mixed with the speckled pattern was most commonly observed among patients having two or more patterns. The RR pattern existed in a variety of diseases including hepatitis C, AIDs, pulmonary diseases, nephropathy diseases, and even healthy people. The highest prevalence of the RR pattern was observed in hepatic diseases, such as hepatic dysfunction (0.79%), hepatic cirrhosis (1.05%), PBC (0.85%), and AIH (0.65%), etc. The positive rate of specific antibodies in RR pattern cases was 31.25%, and anti-Ro52 (27, 20.61%) was the most common target antibody. Conclusion The RR pattern had a low prevalence in ANAs test samples and varied in different nationalities and regions. Except for hepatitis C, it could be observed in AIDs, pulmonary diseases, nephropathy, other hepatic diseases, and even healthy people, but the positive rate was slightly higher in hepatic diseases. Its mechanism of action and clinical relevance still need clarification.
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Affiliation(s)
- Jingjing Meng
- Department of Rheumatology and Clinical Immunology, Chinese Academy of Medical Sciences & Peking Union Medical College, National Clinical Research Center for Dermatologic and Immunologic Diseases (NCRC-DID), Ministry of Science & Technology, Key Laboratory of Rheumatology & Clinical Immunology, Ministry of Education, Beijing, China
- Department of Clinical Laboratory, Fifth Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Guoxiang Yang
- Department of Clinical Laboratory, Inner Mongolia People’s Hospital, Hohhot, China
| | - Siting Li
- Department of Rheumatology and Clinical Immunology, Chinese Academy of Medical Sciences & Peking Union Medical College, National Clinical Research Center for Dermatologic and Immunologic Diseases (NCRC-DID), Ministry of Science & Technology, Key Laboratory of Rheumatology & Clinical Immunology, Ministry of Education, Beijing, China
| | - Yueming Luo
- Department of Rheumatology and Clinical Immunology, Chinese Academy of Medical Sciences & Peking Union Medical College, National Clinical Research Center for Dermatologic and Immunologic Diseases (NCRC-DID), Ministry of Science & Technology, Key Laboratory of Rheumatology & Clinical Immunology, Ministry of Education, Beijing, China
- Jiangmen Wuyi Hospital of Traditional Chinese Medicine (TCM) (Affiliated Jiangmen TCM Hospital of Ji’nan University), Jiangmen, China
| | - Yina Bai
- Department of Rheumatology and Clinical Immunology, Chinese Academy of Medical Sciences & Peking Union Medical College, National Clinical Research Center for Dermatologic and Immunologic Diseases (NCRC-DID), Ministry of Science & Technology, Key Laboratory of Rheumatology & Clinical Immunology, Ministry of Education, Beijing, China
| | - Chuiwen Deng
- Department of Rheumatology and Clinical Immunology, Chinese Academy of Medical Sciences & Peking Union Medical College, National Clinical Research Center for Dermatologic and Immunologic Diseases (NCRC-DID), Ministry of Science & Technology, Key Laboratory of Rheumatology & Clinical Immunology, Ministry of Education, Beijing, China
| | - Ning Song
- Department of Rheumatology and Clinical Immunology, Chinese Academy of Medical Sciences & Peking Union Medical College, National Clinical Research Center for Dermatologic and Immunologic Diseases (NCRC-DID), Ministry of Science & Technology, Key Laboratory of Rheumatology & Clinical Immunology, Ministry of Education, Beijing, China
| | - Mengtao Li
- Department of Rheumatology and Clinical Immunology, Chinese Academy of Medical Sciences & Peking Union Medical College, National Clinical Research Center for Dermatologic and Immunologic Diseases (NCRC-DID), Ministry of Science & Technology, Key Laboratory of Rheumatology & Clinical Immunology, Ministry of Education, Beijing, China
| | - Xiaofeng Zeng
- Department of Rheumatology and Clinical Immunology, Chinese Academy of Medical Sciences & Peking Union Medical College, National Clinical Research Center for Dermatologic and Immunologic Diseases (NCRC-DID), Ministry of Science & Technology, Key Laboratory of Rheumatology & Clinical Immunology, Ministry of Education, Beijing, China
- *Correspondence: Chaojun Hu, ; Xiaofeng Zeng,
| | - Chaojun Hu
- Department of Rheumatology and Clinical Immunology, Chinese Academy of Medical Sciences & Peking Union Medical College, National Clinical Research Center for Dermatologic and Immunologic Diseases (NCRC-DID), Ministry of Science & Technology, Key Laboratory of Rheumatology & Clinical Immunology, Ministry of Education, Beijing, China
- *Correspondence: Chaojun Hu, ; Xiaofeng Zeng,
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7
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Shan Z, Ghadirian N, Lyumkis D, Horton NC. Pretransition state and apo structures of the filament-forming enzyme SgrAI elucidate mechanisms of activation and substrate specificity. J Biol Chem 2022; 298:101760. [PMID: 35202658 PMCID: PMC8960973 DOI: 10.1016/j.jbc.2022.101760] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Revised: 02/14/2022] [Accepted: 02/16/2022] [Indexed: 12/01/2022] Open
Abstract
Enzyme filamentation is a widespread phenomenon that mediates enzyme regulation and function. For the filament-forming sequence-specific DNA endonuclease SgrAI, the process of filamentation both accelerates its DNA cleavage activity and expands its DNA sequence specificity, thus allowing for many additional DNA sequences to be rapidly cleaved. Both outcomes-the acceleration of DNA cleavage and the expansion of sequence specificity-are proposed to regulate critical processes in bacterial innate immunity. However, the mechanistic bases underlying these events remain unclear. Herein, we describe two new structures of the SgrAI enzyme that shed light on its catalytic function. First, we present the cryo-EM structure of filamentous SgrAI bound to intact primary site DNA and Ca2+ resolved to ∼2.5 Å within the catalytic center, which represents the trapped enzyme-DNA complex prior to the DNA cleavage reaction. This structure reveals important conformational changes that contribute to the catalytic mechanism and the binding of a second divalent cation in the enzyme active site, which is expected to contribute to increased DNA cleavage activity of SgrAI in the filamentous state. Second, we present an X-ray crystal structure of DNA-free (apo) SgrAI resolved to 2.0 Å resolution, which reveals a disordered loop involved in DNA recognition. Collectively, these multiple new observations clarify the mechanism of expansion of DNA sequence specificity of SgrAI, including the indirect readout of sequence-dependent DNA structure, changes in protein-DNA interactions, and the disorder-to-order transition of a crucial DNA recognition element.
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Affiliation(s)
- Zelin Shan
- Laboratory of Genetics, The Salk Institute of Biological Sciences, La Jolla, California, USA
| | - Niloofar Ghadirian
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona, USA
| | - Dmitry Lyumkis
- Laboratory of Genetics, The Salk Institute of Biological Sciences, La Jolla, California, USA; Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, California, USA.
| | - Nancy C Horton
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona, USA.
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8
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Variable penetrance of Nab3 granule accumulation quantified by a new tool for high-throughput single-cell granule analysis. Curr Genet 2022; 68:467-480. [PMID: 35301575 DOI: 10.1007/s00294-022-01234-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 02/16/2022] [Accepted: 03/02/2022] [Indexed: 12/12/2022]
Abstract
Reorganization of cellular proteins into subcellular compartments, such as the concentration of RNA-binding proteins into cytoplasmic stress granules and P-bodies, is a well-recognized, widely studied physiological process currently under intense investigation. One example of this is the induction of the yeast Nab3 transcription termination factor to rearrange from its pan-nucleoplasmic distribution to a granule at the nuclear periphery in response to nutrient limitation. Recent work in many cell types has shown that protein condensation in the nucleus is functionally important for transcription initiation, RNA processing, and termination. However, little is known about how subnuclear compartments form. Here, we have quantitatively analyzed this dynamic process in living yeast using a high-throughput computational tool and fluorescence microscopy. This analysis revealed that Nab3 granule accumulation varies in penetrance across yeast strains. A concentrated single granule is formed from at least a quarter of the nuclear Nab3 drawn from the rest of the nucleus. Levels of granule accumulation were inversely correlated with a growth defect in the absence of glucose. Importantly, the basis for some of the variation in penetrance was attributable to a defect in mitochondrial function. This publicly available computational tool provides a rigorous, reproducible, and unbiased examination of Nab3 granule accumulation that should be widely applicable to a variety of fluorescent images. Thousands of live cells can be readily examined enabling rigorous statistical verification of significance. With it, we describe a new feature of inducible subnuclear compartment formation for RNA-binding transcription factors and an important determinant of granule biogenesis.
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9
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IMPDH dysregulation in disease: a mini review. Biochem Soc Trans 2022; 50:71-82. [PMID: 35191957 PMCID: PMC9022972 DOI: 10.1042/bst20210446] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 01/24/2022] [Accepted: 01/26/2022] [Indexed: 12/20/2022]
Abstract
Inosine-5′-monophosphate dehydrogenase (IMPDH) is a highly conserved enzyme in purine metabolism that is tightly regulated on multiple levels. IMPDH has a critical role in purine biosynthesis, where it regulates flux at the branch point between adenine and guanine nucleotide synthesis, but it also has a role in transcription regulation and other moonlighting functions have been described. Vertebrates have two isoforms, IMPDH1 and IMPDH2, and point mutations in each are linked to human disease. Mutations in IMPDH2 in humans are associated with neurodevelopmental disease, but the effects of mutations at the enzyme level have not yet been characterized. Mutations in IMPDH1 lead to retinal degeneration in humans, and recent studies have characterized how they cause functional defects in regulation. IMPDH1 is expressed as two unique splice variants in the retina, a tissue with very high and specific demands for purine nucleotides. Recent studies have revealed functional differences among splice variants, demonstrating that retinal variants up-regulate guanine nucleotide synthesis by reducing sensitivity to feedback inhibition by downstream products. A better understanding of the role of IMPDH1 in the retina and the characterization of an animal disease model will be critical for determining the molecular mechanism of IMPDH1-associated blindness.
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10
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Burrell AL, Nie C, Said M, Simonet JC, Fernández-Justel D, Johnson MC, Quispe J, Buey RM, Peterson JR, Kollman JM. IMPDH1 retinal variants control filament architecture to tune allosteric regulation. Nat Struct Mol Biol 2022; 29:47-58. [PMID: 35013599 PMCID: PMC9044917 DOI: 10.1038/s41594-021-00706-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 11/23/2021] [Indexed: 01/06/2023]
Abstract
Inosine-5'-monophosphate dehydrogenase (IMPDH), a key regulatory enzyme in purine nucleotide biosynthesis, dynamically assembles filaments in response to changes in metabolic demand. Humans have two isoforms: IMPDH2 filaments reduce sensitivity to feedback inhibition, while IMPDH1 assembly remains uncharacterized. IMPDH1 plays a unique role in retinal metabolism, and point mutants cause blindness. Here, in a series of cryogenic-electron microscopy structures we show that human IMPDH1 assembles polymorphic filaments with different assembly interfaces in extended and compressed states. Retina-specific splice variants introduce structural elements that reduce sensitivity to GTP inhibition, including stabilization of the extended filament form. Finally, we show that IMPDH1 disease mutations fall into two classes: one disrupts GTP regulation and the other has no effect on GTP regulation or filament assembly. These findings provide a foundation for understanding the role of IMPDH1 in retinal function and disease and demonstrate the diverse mechanisms by which metabolic enzyme filaments are allosterically regulated.
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Affiliation(s)
- Anika L Burrell
- Department of Biochemistry, University of Washington, Seattle, WA, USA
| | - Chuankai Nie
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, USA
| | - Meerit Said
- Department of Biochemistry, University of Washington, Seattle, WA, USA
| | - Jacqueline C Simonet
- Cancer Epigenetics and Signaling Program, Fox Chase Cancer Center, Philadelphia, PA, USA
- Department of Biology, Arcadia University, Glenside, PA, USA
| | - David Fernández-Justel
- Metabolic Engineering Group, Departamento de Microbiología y Genética, Universidad de Salamanca, Campus Miguel de Unamuno, Salamanca, Spain
| | - Matthew C Johnson
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Department of Structural Biology, Genentech, South San Francisco, CA, USA
| | - Joel Quispe
- Department of Biochemistry, University of Washington, Seattle, WA, USA
| | - Rubén M Buey
- Metabolic Engineering Group, Departamento de Microbiología y Genética, Universidad de Salamanca, Campus Miguel de Unamuno, Salamanca, Spain
| | - Jeffrey R Peterson
- Cancer Epigenetics and Signaling Program, Fox Chase Cancer Center, Philadelphia, PA, USA
| | - Justin M Kollman
- Department of Biochemistry, University of Washington, Seattle, WA, USA.
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11
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Cleghorn WM, Burrell AL, Giarmarco MM, Brock DC, Wang Y, Chambers ZS, Du J, Kollman JM, Brockerhoff SE. A highly conserved zebrafish IMPDH retinal isoform produces the majority of guanine and forms dynamic protein filaments in photoreceptor cells. J Biol Chem 2022; 298:101441. [PMID: 34813793 PMCID: PMC8688572 DOI: 10.1016/j.jbc.2021.101441] [Citation(s) in RCA: 6] [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: 08/30/2021] [Revised: 11/12/2021] [Accepted: 11/13/2021] [Indexed: 12/18/2022] Open
Abstract
Inosine monophosphate dehydrogenase (IMPDH) is a key regulatory enzyme in the de novo synthesis of the purine base guanine. Dominant mutations in human IMPDH1 cause photoreceptor degeneration for reasons that are unknown. Here, we sought to provide some foundational information on Impdh1a in the zebrafish retina. We found that in zebrafish, gene subfunctionalization due to ancestral duplication resulted in a predominant retinal variant expressed exclusively in rod and cone photoreceptors. This variant is structurally and functionally similar to the human IMPDH1 retinal variant and shares a reduced sensitivity to GTP-mediated inhibition. We also demonstrated that Impdh1a forms prominent protein filaments in vitro and in vivo in both rod and cone photoreceptor cell bodies, synapses, and to a lesser degree, in outer segments. These filaments changed length and cellular distribution throughout the day consistent with diurnal changes in both mRNA and protein levels. The loss of Impdh1a resulted in a substantial reduction of guanine levels, although cellular morphology and cGMP levels remained normal. Our findings demonstrate a significant role for IMPDH1 in photoreceptor guanine production and provide fundamental new information on the details of this protein in the zebrafish retina.
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Affiliation(s)
- Whitney M Cleghorn
- Department of Biochemistry, University of Washington, Seattle, Washington, USA; Department of Ophthalmology, University of Washington, Seattle, Washington, USA
| | - Anika L Burrell
- Department of Biochemistry, University of Washington, Seattle, Washington, USA
| | | | - Daniel C Brock
- Department of Biochemistry, University of Washington, Seattle, Washington, USA
| | - Yekai Wang
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, USA; Department of Biochemistry, West Virginia University, Morgantown, West Virginia, USA
| | - Zachary S Chambers
- Department of Biochemistry, University of Washington, Seattle, Washington, USA
| | - Jianhai Du
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, USA; Department of Biochemistry, West Virginia University, Morgantown, West Virginia, USA
| | - Justin M Kollman
- Department of Biochemistry, University of Washington, Seattle, Washington, USA
| | - Susan E Brockerhoff
- Department of Biochemistry, University of Washington, Seattle, Washington, USA; Department of Ophthalmology, University of Washington, Seattle, Washington, USA.
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12
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Calvo-Vidal MN, Zamponi N, Krumsiek J, Stockslager MA, Revuelta MV, Phillip JM, Marullo R, Tikhonova E, Kotlov N, Patel J, Yang SN, Yang L, Taldone T, Thieblemont C, Leonard JP, Martin P, Inghirami G, Chiosis G, Manalis SR, Cerchietti L. Oncogenic HSP90 Facilitates Metabolic Alterations in Aggressive B-cell Lymphomas. Cancer Res 2021; 81:5202-5216. [PMID: 34479963 PMCID: PMC8530929 DOI: 10.1158/0008-5472.can-21-2734] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2021] [Revised: 08/30/2021] [Accepted: 09/01/2021] [Indexed: 12/14/2022]
Abstract
HSP90 is critical for maintenance of the cellular proteostasis. In cancer cells, HSP90 also becomes a nucleating site for the stabilization of multiprotein complexes including signaling pathways and transcription complexes. Here we described the role of this HSP90 form, referred to as oncogenic HSP90, in the regulation of cytosolic metabolic pathways in proliferating B-cell lymphoma cells. Oncogenic HSP90 assisted in the organization of metabolic enzymes into non-membrane-bound functional compartments. Under experimental conditions that conserved cellular proteostasis, oncogenic HSP90 coordinated and sustained multiple metabolic pathways required for energy production and maintenance of cellular biomass as well as for secretion of extracellular metabolites. Conversely, inhibition of oncogenic HSP90, in absence of apparent client protein degradation, decreased the efficiency of MYC-driven metabolic reprogramming. This study reveals that oncogenic HSP90 supports metabolism in B-cell lymphoma cells and patients with diffuse large B-cell lymphoma, providing a novel mechanism of activity for HSP90 inhibitors. SIGNIFICANCE: The oncogenic form of HSP90 organizes and maintains functional multienzymatic metabolic hubs in cancer cells, suggesting the potential of repurposing oncogenic HSP90 selective inhibitors to disrupt metabolism in lymphoma cells.
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Affiliation(s)
- M Nieves Calvo-Vidal
- Hematology and Oncology Division, Department of Medicine, Weill Cornell Medicine, New York, New York
| | - Nahuel Zamponi
- Hematology and Oncology Division, Department of Medicine, Weill Cornell Medicine, New York, New York
| | - Jan Krumsiek
- Department of Physiology and Biophysics, Institute for Computational Biomedicine, Englander Institute for Precision Medicine, Weill Cornell Medicine, New York, New York
| | - Max A Stockslager
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Maria V Revuelta
- Hematology and Oncology Division, Department of Medicine, Weill Cornell Medicine, New York, New York
| | - Jude M Phillip
- Hematology and Oncology Division, Department of Medicine, Weill Cornell Medicine, New York, New York
| | - Rossella Marullo
- Hematology and Oncology Division, Department of Medicine, Weill Cornell Medicine, New York, New York
| | | | | | - Jayeshkumar Patel
- Hematology and Oncology Division, Department of Medicine, Weill Cornell Medicine, New York, New York
| | - Shao Ning Yang
- Hematology and Oncology Division, Department of Medicine, Weill Cornell Medicine, New York, New York
| | - Lucy Yang
- Koch Institute for Integrative Cancer Research and Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Tony Taldone
- Molecular Pharmacology and Chemistry Program, Memorial Sloan-Kettering Institute, New York, New York
| | - Catherine Thieblemont
- APHP, Saint-Louis Hospital, Hemato-Oncology, Paris - Paris Diderot University, Paris, France.,EA3788, Paris Descartes University, Paris, France
| | - John P Leonard
- Hematology and Oncology Division, Department of Medicine, Weill Cornell Medicine, New York, New York
| | - Peter Martin
- Hematology and Oncology Division, Department of Medicine, Weill Cornell Medicine, New York, New York
| | - Giorgio Inghirami
- Deparment of Pathology and Laboratory Medicine, Weill Cornell Medicine, New York, New York
| | - Gabriela Chiosis
- Molecular Pharmacology and Chemistry Program, Memorial Sloan-Kettering Institute, New York, New York
| | - Scott R Manalis
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts.,Koch Institute for Integrative Cancer Research and Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts.,Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Leandro Cerchietti
- Hematology and Oncology Division, Department of Medicine, Weill Cornell Medicine, New York, New York.
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13
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Ma K, Li N, Yan X, Zhu Y, Zhang C. Energy deficiency caused by CTPS downregulation in decidua may contribute to pre-eclampsia by impairing decidualization. J Cell Physiol 2021; 236:6520-6533. [PMID: 33576499 DOI: 10.1002/jcp.30326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2020] [Revised: 01/28/2021] [Accepted: 02/01/2021] [Indexed: 11/10/2022]
Abstract
Pre-eclampsia (PE) is a pregnancy-related disorder that occurs after 20 weeks of gestation. It seriously affects the health of maternity and the fetus. However, the pathogenesis of PE is still unknown. Decidualization deficiency is considered a contributing factor to the development of PE. CTP synthetase (CTPS) which is the rate-limiting enzyme in the CTP de novo biosynthesis, is essential for nucleic acid synthesis and cellular energy metabolism, and often appears as cytoophidium in many cell types. Here, we found that the expression of CTPS was significantly downregulated in decidual tissues of patients with severe PE compared with healthy pregnant women. During in vitro decidualization, changes in CTPS were accompanied by opposite fluctuation of the AMPK signaling pathway. Moreover, the downregulation of CTPS by glutamine analogs or CTPS small interfering RNA inhibited the decidualization process and the AMPK signaling pathway. Investigating the underlying mechanism of action by co-immunoprecipitation coupled with mass spectrometry showed that CTPS interacted with ATP synthase (ATPS) and maintained the content of ATP on Day 3 of decidualization. However, when combined with mitochondrial stress protein STRESS-70 instead of ATPS, the concentration of ATP on Day 6 of induction was reduced. Corresponding to this, CTPS was mainly distributes in the cytoplasm on Day 3 of induction, while it appeared both in the cytoplasm and the nucleus on Day 6 in decidualized cells, which was similar to that in cells before induction. In summary, we believe that CTPS plays an important role in decidualization by participating in energy metabolism. Abnormal expression of CTPS in decidualization would lead to abnormal decidualization and consequently result in the occurrence of PE.
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Affiliation(s)
- Ke Ma
- Shandong Provincial Key Laboratory of Animal Resistance Biology, College of Life Sciences, Shandong Normal University, Ji'nan, Shandong, China
| | - Na Li
- Shandong Provincial Key Laboratory of Animal Resistance Biology, College of Life Sciences, Shandong Normal University, Ji'nan, Shandong, China
| | - Xingyu Yan
- School of Medicine, Xiamen University, Xiamen, Fujian, China
| | - Yunqing Zhu
- Shandong Provincial Key Laboratory of Animal Resistance Biology, College of Life Sciences, Shandong Normal University, Ji'nan, Shandong, China
| | - Cong Zhang
- Shandong Provincial Key Laboratory of Animal Resistance Biology, College of Life Sciences, Shandong Normal University, Ji'nan, Shandong, China.,Center for Reproductive Medicine, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.,Shanghai Key Laboratory for Assisted Reproduction and Reproductive Genetics, Shanghai, China
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14
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Abstract
Enzymatic reactions and noncovalent (i.e., supramolecular) interactions are two fundamental nongenetic attributes of life. Enzymatic noncovalent synthesis (ENS) refers to a process where enzymatic reactions control intermolecular noncovalent interactions for spatial organization of higher-order molecular assemblies that exhibit emergent properties and functions. Like enzymatic covalent synthesis (ECS), in which an enzyme catalyzes the formation of covalent bonds to generate individual molecules, ENS is a unifying theme for understanding the functions, morphologies, and locations of molecular ensembles in cellular environments. This review intends to provide a summary of the works of ENS within the past decade and emphasize ENS for functions. After comparing ECS and ENS, we describe a few representative examples where nature uses ENS, as a rule of life, to create the ensembles of biomacromolecules for emergent properties/functions in a myriad of cellular processes. Then, we focus on ENS of man-made (synthetic) molecules in cell-free conditions, classified by the types of enzymes. After that, we introduce the exploration of ENS of man-made molecules in the context of cells by discussing intercellular, peri/intracellular, and subcellular ENS for cell morphogenesis, molecular imaging, cancer therapy, and other applications. Finally, we provide a perspective on the promises of ENS for developing molecular assemblies/processes for functions. This review aims to be an updated introduction for researchers who are interested in exploring noncovalent synthesis for developing molecular science and technologies to address societal needs.
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Affiliation(s)
- Hongjian He
- Department of Chemistry, Brandeis University, 415 South Street, Waltham, Massachusetts 02454, United States
| | - Weiyi Tan
- Department of Chemistry, Brandeis University, 415 South Street, Waltham, Massachusetts 02454, United States
| | - Jiaqi Guo
- Department of Chemistry, Brandeis University, 415 South Street, Waltham, Massachusetts 02454, United States
| | - Meihui Yi
- Department of Chemistry, Brandeis University, 415 South Street, Waltham, Massachusetts 02454, United States
| | - Adrianna N Shy
- Department of Chemistry, Brandeis University, 415 South Street, Waltham, Massachusetts 02454, United States
| | - Bing Xu
- Department of Chemistry, Brandeis University, 415 South Street, Waltham, Massachusetts 02454, United States
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15
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Calise SJ, Chan EKL. Anti-rods/rings autoantibody and IMPDH filaments: an update after fifteen years of discovery. Autoimmun Rev 2020; 19:102643. [PMID: 32805424 DOI: 10.1016/j.autrev.2020.102643] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2020] [Accepted: 03/27/2020] [Indexed: 02/07/2023]
Abstract
Autoantibodies to unknown subcellular rod and ring-shaped structures were first discovered in sera from hepatitis C patients in 2005. Early studies showed a strong association between these anti-rods/rings antibodies (anti-RR) and the standard of care interferon-α plus ribavirin combination therapy (IFN/RBV), suggesting that anti-RR are drug-induced autoantibodies. In the context of hepatitis C, anti-RR have been linked with relapse from or lack of response to IFN/RBV in some patient cohorts. However, examples of anti-RR in other diseases and healthy individuals have also been reported over the years, although anti-RR remains a rare autoantibody response in general. The advent of new direct-acting antiviral drugs for chronic hepatitis C and studies of anti-RR from different parts of the world are also beginning to change the perception of anti-RR. The nucleotide biosynthetic enzyme inosine monophosphate dehydrogenase (IMPDH) has been identified as the major autoantigen recognized by anti-RR. Coincidentally, the assembly of IMPDH into micron-scale rod and ring-shaped structures was discovered around the same time as anti-RR. Knowledge of the fundamental biological properties and cellular functions of these structures, referred to as "IMPDH filaments" by cell biologists, has advanced in parallel to anti-RR antibodies. Recent studies have revealed that IMPDH filament assembly is a mechanism to prevent feedback inhibition of IMPDH and is therefore important for the increased nucleotide production required in hyperproliferating cells, like activated T cells. Fifteen years later, we review the history and current knowledge in both the anti-RR autoantibody and IMPDH filament fields. TAKE-HOME MESSAGE: Anti-rods/rings are recognized as an example of a drug-induced autoantibody in hepatitis C patients treated with interferon and ribavirin, although new studies suggest anti-rods/rings may be detected in other contexts and may depend on unknown environmental or genetic factors in different populations. Recent data suggest that the assembly of IMPDH into rod and ring structures, the targets of anti-rods/rings autoantibody, is a mechanism for hyperproliferating cells, like activated T cells, to maintain increased guanine nucleotide levels to support rapid cell division.
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Affiliation(s)
- S John Calise
- Department of Oral Biology, University of Florida, 1395 Center Drive, Gainesville, FL 32610-0424, USA.
| | - Edward K L Chan
- Department of Oral Biology, University of Florida, 1395 Center Drive, Gainesville, FL 32610-0424, USA.
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16
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Keppeke GD, Barcelos D, Fernandes M, Comodo AN, Guimarães DP, Cardili L, Carapeto FCL, Andrade LEC, Landman G. IMP dehydrogenase rod/ring structures in acral melanomas. Pigment Cell Melanoma Res 2020; 33:490-497. [PMID: 31883196 DOI: 10.1111/pcmr.12854] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 12/19/2019] [Accepted: 12/23/2019] [Indexed: 12/24/2022]
Abstract
Acral lentiginous melanoma (ALM) is a rare subtype of melanoma with aggressive behavior. IMPDH enzyme, involved in de novo GTP biosynthesis, has been reported to assemble into large filamentary structures called rods/rings (RR) or cytoophidium (cellular snakes). RR assembly induces a hyperactive state in IMPDH, usually to supply a high demand for GTP nucleotides, such as in highly proliferative cells. We investigate whether aggressive melanoma tumor cells present IMPDH-based RR structures. Forty-five ALM paraffin-embedded tissue samples and 59 melanocytic nevi were probed with anti-IMPDH2 antibody. Both the rod- and ring-shaped RR could be observed, with higher frequency in ALM. ROC curve analyzing the proportions of RR-positive cells in ALM versus nevi yielded a 0.88 AUC. Using the cutoff of 5.5% RR-positive cells, there was a sensitivity of 80% and specificity of 85% for ALM diagnosis. In ALM, 36 (80%) showed RR frequency above the cutoff, being classified as RR-positive, compared with only 9 (15%) of the nevi (p < .001). Histopathology showed that 71% of the RR-positive specimens presented Breslow thickness > 4.0mm, compared with only 29% in the RR-low/negative (p = .039). We propose that screening for RR structures in biopsy specimens may be a valuable tool helping differentiate ALM from nevi and accessing tumor malignancy.
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Affiliation(s)
- Gerson D Keppeke
- Rheumatology Division, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Denise Barcelos
- Department of Pathology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Mariana Fernandes
- Department of Pathology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Andréia N Comodo
- Department of Pathology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Daiane P Guimarães
- Department of Pathology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Leonardo Cardili
- Department of Pathology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Fernando C L Carapeto
- Department of Pathology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Luis E C Andrade
- Rheumatology Division, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Gilles Landman
- Department of Pathology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
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17
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Park CK, Horton NC. Structures, functions, and mechanisms of filament forming enzymes: a renaissance of enzyme filamentation. Biophys Rev 2019; 11:927-994. [PMID: 31734826 PMCID: PMC6874960 DOI: 10.1007/s12551-019-00602-6] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Accepted: 10/24/2019] [Indexed: 12/19/2022] Open
Abstract
Filament formation by non-cytoskeletal enzymes has been known for decades, yet only relatively recently has its wide-spread role in enzyme regulation and biology come to be appreciated. This comprehensive review summarizes what is known for each enzyme confirmed to form filamentous structures in vitro, and for the many that are known only to form large self-assemblies within cells. For some enzymes, studies describing both the in vitro filamentous structures and cellular self-assembly formation are also known and described. Special attention is paid to the detailed structures of each type of enzyme filament, as well as the roles the structures play in enzyme regulation and in biology. Where it is known or hypothesized, the advantages conferred by enzyme filamentation are reviewed. Finally, the similarities, differences, and comparison to the SgrAI endonuclease system are also highlighted.
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Affiliation(s)
- Chad K. Park
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ 85721 USA
| | - Nancy C. Horton
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ 85721 USA
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18
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Anti-Tumor Potential of IMP Dehydrogenase Inhibitors: A Century-Long Story. Cancers (Basel) 2019; 11:cancers11091346. [PMID: 31514446 PMCID: PMC6770829 DOI: 10.3390/cancers11091346] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Revised: 09/01/2019] [Accepted: 09/02/2019] [Indexed: 01/15/2023] Open
Abstract
The purine nucleotides ATP and GTP are essential precursors to DNA and RNA synthesis and fundamental for energy metabolism. Although de novo purine nucleotide biosynthesis is increased in highly proliferating cells, such as malignant tumors, it is not clear if this is merely a secondary manifestation of increased cell proliferation. Suggestive of a direct causative effect includes evidence that, in some cancer types, the rate-limiting enzyme in de novo GTP biosynthesis, inosine monophosphate dehydrogenase (IMPDH), is upregulated and that the IMPDH inhibitor, mycophenolic acid (MPA), possesses anti-tumor activity. However, historically, enthusiasm for employing IMPDH inhibitors in cancer treatment has been mitigated by their adverse effects at high treatment doses and variable response. Recent advances in our understanding of the mechanistic role of IMPDH in tumorigenesis and cancer progression, as well as the development of IMPDH inhibitors with selective actions on GTP synthesis, have prompted a reappraisal of targeting this enzyme for anti-cancer treatment. In this review, we summarize the history of IMPDH inhibitors, the development of new inhibitors as anti-cancer drugs, and future directions and strategies to overcome existing challenges.
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19
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Noree C, Sirinonthanawech N, Wilhelm JE. Saccharomyces cerevisiae ASN1 and ASN2 are asparagine synthetase paralogs that have diverged in their ability to polymerize in response to nutrient stress. Sci Rep 2019; 9:278. [PMID: 30670751 PMCID: PMC6342913 DOI: 10.1038/s41598-018-36719-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Accepted: 11/26/2018] [Indexed: 11/10/2022] Open
Abstract
Recent work has found that many metabolic enzymes have the ability to polymerize in response to metabolic changes or environmental stress. This ability to polymerize is well conserved for the few metabolic enzyme paralogs that have been studied in yeast. Here we describe the first set of paralogs, Asn1p and Asn2p, that have differential assembly behavior. Asn1p and Asn2p both co-assemble into filaments in response to nutrient limitation. However, the ability of Asn2p to form filaments is strictly dependent on the presence of Asn1p. Using mutations that block enzyme activity but have differential effects on Asn1p polymerization, we have found that Asn1p polymers are unlikely to have acquired a moonlighting function. Together these results provide a novel system for understanding the regulation and evolution of metabolic enzyme polymerization.
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Affiliation(s)
- Chalongrat Noree
- Institute of Molecular Biosciences, Mahidol University, 25/25 Phuttamonthon 4 Road, Salaya, Phuttamonthon, Nakhon Pathom, 73170, Thailand.
| | - Naraporn Sirinonthanawech
- Institute of Molecular Biosciences, Mahidol University, 25/25 Phuttamonthon 4 Road, Salaya, Phuttamonthon, Nakhon Pathom, 73170, Thailand
| | - James E Wilhelm
- Section of Cell and Developmental Biology, Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive (MC 0347), La Jolla, CA, 92093-0347, USA.
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20
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Keppeke GD, Calise SJ, Chan EKL, Andrade LEC. Ribavirin induces widespread accumulation of IMP dehydrogenase into rods/rings structures in multiple major mouse organs. Antiviral Res 2018; 162:130-135. [PMID: 30605724 DOI: 10.1016/j.antiviral.2018.12.017] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Revised: 11/27/2018] [Accepted: 12/28/2018] [Indexed: 12/11/2022]
Abstract
Ribavirin (RBV) is a guanosine analogue triazole most commonly used in the treatment of chronic hepatitis C (HCV) infection. Although its mechanism of action is a matter of debate, several possibilities have been proposed, including depletion of guanine nucleotides through inhibition of inosine monophosphate dehydrogenase (IMPDH). IMPDH has been shown to assemble into micron-scale rod- and ring-shaped structures (rods/rings or RR), also called "IMPDH filaments," both in vitro and in vivo. Formation of RR structures can occur naturally, potentially to influence IMPDH activity, or when de novo guanosine monophosphate biosynthesis or IMPDH itself are inhibited by nutrient deprivation or drugs like RBV. Numerous studies have also reported the occurrence of autoantibodies targeting RR structures (anti-RR) in HCV patients previously treated or under treatment with interferon-α and ribavirin (IFN/RBV) combination therapy. For this brief study, we considered the strong association between RR autoantibodies and IFN/RBV treatment, and the lack of data assessing how RBV affects RR formation in a variety of tissues in vivo. First, RR structures formed in the spleen and pancreas of normal mice without any treatment. Then, in RBV-treated mice, we detected RR structures in a number of tissues, including stomach, liver, spleen, kidney, brain, skin, and cardiac and skeletal muscle. We made several intriguing observations: predominance of RR structures in the mucosa and submucosa layers of the stomach wall; a high proportion of RR-positive cells in the cerebral cortex, suggesting that RBV actually crosses the blood-brain barrier; and a higher ratio of rings to rods in the epidermis compared to the dermis layer of the skin. Screening for RR structures appears to be a useful method to track tissue penetration of RBV and the many RR-inducing drugs previously identified.
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Affiliation(s)
- Gerson Dierley Keppeke
- Rheumatology Division, Escola Paulista de Medicina, Universidade Federal de São Paulo, Rua Botucatu 740, São Paulo, SP, 04023-062, Brazil.
| | - S John Calise
- Department of Oral Biology, University of Florida, 1395 Center Drive, Gainesville, FL, 32610-0424, USA
| | - Edward K L Chan
- Department of Oral Biology, University of Florida, 1395 Center Drive, Gainesville, FL, 32610-0424, USA
| | - Luis Eduardo C Andrade
- Rheumatology Division, Escola Paulista de Medicina, Universidade Federal de São Paulo, Rua Botucatu 740, São Paulo, SP, 04023-062, Brazil
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21
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Calise SJ, Abboud G, Kasahara H, Morel L, Chan EKL. Immune Response-Dependent Assembly of IMP Dehydrogenase Filaments. Front Immunol 2018; 9:2789. [PMID: 30555474 PMCID: PMC6283036 DOI: 10.3389/fimmu.2018.02789] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Accepted: 11/12/2018] [Indexed: 12/14/2022] Open
Abstract
Inosine monophosphate dehydrogenase (IMPDH) catalyzes the conversion of IMP to xanthosine monophosphate, the rate-limiting step in de novo guanosine monophosphate (GMP) synthesis. In cultured cells, IMPDH polymerizes into micron-scale filamentous structures when GMP synthesis is inhibited by depletion of purine precursors or by various drugs, including mycophenolic acid, ribavirin, and methotrexate. IMPDH filaments also spontaneously form in undifferentiated mouse embryonic stem cells and induced pluripotent stem cells, hinting they might function in various highly proliferative cell types. Therefore, we investigated IMPDH filament formation in human and murine T cells, which rely heavily on de novo guanine nucleotide synthesis to rapidly proliferate in response to antigenic challenge. We discovered extensive in vivo IMPDH filament formation in mature T cells, B cells, and other proliferating splenocytes of normal, adult B6 mice. Both cortical and medullary thymocytes in young and old mice also showed considerable assembly of IMPDH filaments. We then stimulated primary human peripheral blood mononuclear cells ex vivo with T cell mitogens phytohemagglutinin (PHA), concanavalin A (ConA), or antibodies to CD3 and CD28 for 72 h. We detected IMPDH filaments in 40–60% of T cells after activation compared to 0–10% of unstimulated T cells. Staining of activated T cells for the proliferation marker Ki-67 also showed an association between IMPDH filament formation and proliferation. Additionally, we transferred ovalbumin-specific CD4+ T cells from B6.OT-II mice into B6.Ly5a recipient mice, challenged these mice with ovalbumin, and harvested spleens 6 days later. In these spleens, we identified abundant IMPDH filaments in transferred T cells by immunofluorescence, indicating that IMPDH also polymerizes during in vivo antigen-specific T cell activation. Overall, our data indicate that IMPDH filament formation is a novel aspect of T cell activation and proliferation, and that filaments might be useful morphological markers for T cell activation. The data also suggest that in vivo IMPDH filament formation could be occurring in a variety of proliferating cell types throughout the body. We propose that T cell activation will be a valuable model for future experiments probing the molecular mechanisms that drive IMPDH polymerization, as well as how IMPDH filament formation affects cell function.
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Affiliation(s)
- S John Calise
- Department of Oral Biology, University of Florida, Gainesville, FL, United States
| | - Georges Abboud
- Department of Pathology, Immunology, and Laboratory Medicine, University of Florida, Gainesville, FL, United States
| | - Hideko Kasahara
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, FL, United States
| | - Laurence Morel
- Department of Pathology, Immunology, and Laboratory Medicine, University of Florida, Gainesville, FL, United States
| | - Edward K L Chan
- Department of Oral Biology, University of Florida, Gainesville, FL, United States
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22
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McCluskey GD, Bearne SL. Anfractuous assemblies of IMP dehydrogenase and CTP synthase: new twists on regulation? FEBS J 2018; 285:3724-3728. [PMID: 30285320 DOI: 10.1111/febs.14658] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Accepted: 09/12/2018] [Indexed: 12/16/2022]
Abstract
CTP synthase (CTPS) and IMP dehydrogenase (IMPDH) catalyse the rate-limiting steps of de novo CTP and guanosine nucleotide biosynthesis, respectively, and form filament assemblies in response to inhibitors. A recent study explores the morphology and dynamics of these assemblies using fluorescence and super-resolution confocal microscopy with cell lines expressing CTPS1 and IMPDH2 fusion proteins. The formation and dismantling of mixed assemblies depends on nucleotide levels, suggesting a co-regulation function.
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Affiliation(s)
- Gregory D McCluskey
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Canada
| | - Stephen L Bearne
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Canada.,Department of Chemistry, Dalhousie University, Halifax, Canada
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23
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Calise SJ, Zheng B, Hasegawa T, Satoh M, Isailovic N, Ceribelli A, Andrade LE, Boylan K, Cavazzana I, Fritzler MJ, de la Torre IG, Hiepe F, Kohl K, Selmi C, Shoenfeld Y, Tincani A, Chan EK. Reference standards for the detection of anti-mitochondrial and anti-rods/rings autoantibodies. Clin Chem Lab Med 2018; 56:1789-1798. [PMID: 29478040 PMCID: PMC8128709 DOI: 10.1515/cclm-2017-1152] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2017] [Accepted: 01/24/2018] [Indexed: 12/19/2022]
Abstract
Background: Anti-mitochondrial antibodies (AMA) are found in >90% of primary biliary cholangitis patients. Anti-rods/rings antibodies (anti-RR) are most commonly associated with interferon-α and ribavirin treatment in hepatitis C patients. Clinical laboratories routinely screen for AMA and anti-RR using indirect immunofluorescence on HEp-2 cells (HEp-2-IFA). Therefore, we sought to establish reference materials for use in AMA and anti-RR testing. Methods: AMA-positive and anti-RR-positive human plasma samples (AMA-REF and RR-REF), identified as potential reference materials based on preliminary data, were further validated by multiple laboratories using HEp-2-IFA, immunoprecipitation (IP), western blotting, IP-western, line immunoassay (LIA), addressable laser bead immunoassay (ALBIA), and ELISA. Results: AMA-REF showed a strong positive cytoplasmic reticular/AMA staining pattern by HEp-2-IFA to ≥1:1280 dilution, and positive signal on rodent kidney/stomach/liver tissue. AMA-REF reacted with E2/E3, E3BP, E1α, and E1β subunits of the pyruvate dehydrogenase complex by IP and western blotting, and was positive for AMA antigens by LIA, ALBIA, and ELISA. RR-REF showed a strong positive rods and rings staining pattern by HEp-2-IFA to ≥1:1280 dilution. RR-REF reacted with inosine monophosphate dehydrogenase by IP, IP-western, and ALBIA. RR-REF also produced a nuclear homogenous staining pattern by HEp-2-IFA, immunoprecipitated proteins associated with anti-U1RNP antibody, and reacted weakly with histones, nucleosomes, Sm, and nRNP/Sm by LIA. Conclusions: AMA-REF and RR-REF are useful reference materials for academic or commercial clinical laboratories to calibrate and establish internal reference standards for immunodiagnostic assays. AMA-REF and RR-REF are now available for free distribution to qualified laboratories through Plasma Services Group.
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Affiliation(s)
- S. John Calise
- Department of Oral Biology, University of Florida, Gainesville, FL, USA
| | - Bing Zheng
- Department of Oral Biology, University of Florida, Gainesville, FL, USA
| | - Tomoko Hasegawa
- Department of Clinical Nursing, University of Occupational and Environmental Health, Kitakyushu, Japan
| | - Minoru Satoh
- Department of Clinical Nursing, University of Occupational and Environmental Health, Kitakyushu, Japan
| | - Natasa Isailovic
- Division of Rheumatology and Clinical Immunology, Laboratory of Autoimmunity and Metabolism, Humanitas Research Hospital, Rozzano, Milan, Italy
| | - Angela Ceribelli
- Division of Rheumatology and Clinical Immunology, Laboratory of Autoimmunity and Metabolism, Humanitas Research Hospital, Rozzano, Milan, Italy
| | - Luis E.C. Andrade
- Division of Rheumatology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
- Immunology Division, Fleury Medicine and Health Laboratories, São Paulo, Brazil
| | - Katherine Boylan
- Scientific & Clinical Affairs, Plasma Services Group Inc., Huntingdon Valley, PA, USA
| | - Ilaria Cavazzana
- Unità Operativa di Reumatologia e Immunologia Clinica, Spedali Civili di Brescia, Brescia, Italy
| | - Marvin J. Fritzler
- Department of Medicine, Cumming School of Medicine, University of Calgary, Calgary, Canada
| | - Ignacio Garcia de la Torre
- Department of Immunology and Rheumatology, Hospital General de Occidente and University of Guadalajara, Guadalajara, Mexico
| | - Falk Hiepe
- Charité – Universitätsmedizin Berlin and Deutsches Rheumaforschungszentrum Berlin, Berlin, Germany
| | - Kathryn Kohl
- Scientific & Clinical Affairs, Plasma Services Group Inc., Huntingdon Valley, PA, USA
| | - Carlo Selmi
- Division of Rheumatology and Clinical Immunology, Laboratory of Autoimmunity and Metabolism, Humanitas Research Hospital, Rozzano, Milan, Italy
- BIOMETRA Department, University of Milan, Italy
| | - Yehuda Shoenfeld
- Zabludowicz Center for Autoimmune Diseases, Sheba Medical Center, Tel Hashomer, Israel
| | - Angela Tincani
- Unità Operativa di Reumatologia e Immunologia Clinica, Spedali Civili di Brescia, Brescia, Italy
| | - Edward K.L. Chan
- Department of Oral Biology, University of Florida, Gainesville, FL, USA
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24
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Duong-Ly KC, Kuo YM, Johnson MC, Cote JM, Kollman JM, Soboloff J, Rall GF, Andrews AJ, Peterson JR. T cell activation triggers reversible inosine-5'-monophosphate dehydrogenase assembly. J Cell Sci 2018; 131:jcs.223289. [PMID: 30154209 DOI: 10.1242/jcs.223289] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Accepted: 08/06/2018] [Indexed: 12/17/2022] Open
Abstract
T cell-mediated adaptive immunity requires naïve, unstimulated T cells to transition from a quiescent metabolic state into a highly proliferative state upon T cell receptor engagement. This complex process depends on transcriptional changes mediated by Ca2+-dependent NFAT signaling, mTOR-mediated signaling and increased activity of the guanine nucleotide biosynthetic inosine-5'-monophosphate (IMP) dehydrogenase 1 and 2 enzymes (IMPDH1 and IMPDH2, hereafter IMPDH). Inhibitors of these pathways serve as potent immunosuppressants. Unexpectedly, we discovered that all three pathways converge to promote the assembly of IMPDH protein into micron-scale macromolecular filamentous structures in response to T cell activation. Assembly is post-transcriptionally controlled by mTOR and the Ca2+ influx regulator STIM1. Furthermore, IMPDH assembly and catalytic activity were negatively regulated by guanine nucleotide levels, suggesting a negative feedback loop that limits biosynthesis of guanine nucleotides. Filamentous IMPDH may be more resistant to this inhibition, facilitating accumulation of the higher GTP levels required for T cell proliferation.
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Affiliation(s)
- Krisna C Duong-Ly
- Cancer Biology Program, Fox Chase Cancer Center, Philadelphia, PA 19111, USA
| | - Yin-Ming Kuo
- Cancer Epigenetics Program, Fox Chase Cancer Center, Philadelphia, PA 19111, USA
| | - Matthew C Johnson
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA
| | - Joy M Cote
- Cancer Epigenetics Program, Fox Chase Cancer Center, Philadelphia, PA 19111, USA
| | - Justin M Kollman
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA
| | - Jonathan Soboloff
- Fels Institute for Cancer Research and Molecular Biology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Glenn F Rall
- Blood Cell Development and Function Program, Fox Chase Cancer Center, Philadelphia, PA 19111, USA
| | - Andrew J Andrews
- Cancer Epigenetics Program, Fox Chase Cancer Center, Philadelphia, PA 19111, USA
| | - Jeffrey R Peterson
- Cancer Biology Program, Fox Chase Cancer Center, Philadelphia, PA 19111, USA
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25
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Schiavon CR, Griffin ME, Pirozzi M, Parashuraman R, Zhou W, Jinnah HA, Reines D, Kahn RA. Compositional complexity of rods and rings. Mol Biol Cell 2018; 29:2303-2316. [PMID: 30024290 PMCID: PMC6249804 DOI: 10.1091/mbc.e18-05-0274] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Rods and rings (RRs) are large linear- or circular-shaped structures typically described as polymers of IMPDH (inosine monophosphate dehydrogenase). They have been observed across a wide variety of cell types and species and can be induced to form by inhibitors of IMPDH. RRs are thought to play a role in the regulation of de novo guanine nucleotide synthesis; however, the function and regulation of RRs is poorly understood. Here we show that the regulatory GTPase, ARL2, a subset of its binding partners, and several resident proteins at the endoplasmic reticulum (ER) also localize to RRs. We also have identified two new inducers of RR formation: AICAR and glucose deprivation. We demonstrate that RRs can be disassembled if guanine nucleotides can be generated by salvage synthesis regardless of the inducer. Finally, we show that there is an ordered addition of components as RRs mature, with IMPDH first forming aggregates, followed by ARL2, and only later calnexin, a marker of the ER. These findings suggest that RRs are considerably more complex than previously thought and that the function(s) of RRs may include involvement of a regulatory GTPase, its effectors, and potentially contacts with intracellular membranes.
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Affiliation(s)
- Cara R Schiavon
- Cancer Biology Graduate Program, Graduate Division of Biomedical and Biological Sciences, Laney Graduate School, Atlanta, GA 30307
| | - Maxwell E Griffin
- Cancer Biology Graduate Program, Graduate Division of Biomedical and Biological Sciences, Laney Graduate School, Atlanta, GA 30307
| | - Marinella Pirozzi
- EuroBioImaging Facility, Institute of Protein Biochemistry, 80131 Naples, Italy
| | - Raman Parashuraman
- EuroBioImaging Facility, Institute of Protein Biochemistry, 80131 Naples, Italy
| | - Wei Zhou
- Department of Hematology and Medical Oncology, Emory University School of Medicine, Atlanta, GA 30322
| | - H A Jinnah
- Department of Neurology and Human Genetics, Emory University School of Medicine, Atlanta, GA 30322
| | - Daniel Reines
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322
| | - Richard A Kahn
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322
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26
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Keppeke GD, Chang CC, Peng M, Chen LY, Lin WC, Pai LM, Andrade LEC, Sung LY, Liu JL. IMP/GTP balance modulates cytoophidium assembly and IMPDH activity. Cell Div 2018; 13:5. [PMID: 29946345 PMCID: PMC6004095 DOI: 10.1186/s13008-018-0038-0] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Accepted: 06/06/2018] [Indexed: 02/07/2023] Open
Abstract
Background Inosine monophosphate dehydrogenase (IMPDH), the rate-limiting enzyme in de novo GTP biosynthesis, plays an important role in cell metabolism and proliferation. It has been demonstrated that IMPDH can aggregate into a macrostructure, termed the cytoophidium, in mammalian cells under a variety of conditions. However, the regulation and function of the cytoophidium are still elusive. Results In this study, we report that spontaneous filamentation of IMPDH is correlated with rapid cell proliferation. Intracellular IMP accumulation promoted cytoophidium assembly, whereas elevated GTP level triggered disassociation of aggregates. By using IMPDH2 CBS domain mutant cell models, which are unable to form the cytoophidium, we have determined that the cytoophidium is of the utmost importance for maintaining the GTP pool and normal cell proliferation in the condition that higher IMPDH activity is required. Conclusions Together, our results suggest a novel mechanism whereby cytoophidium assembly upregulates IMPDH activity and mediates guanine nucleotide homeostasis. Electronic supplementary material The online version of this article (10.1186/s13008-018-0038-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Gerson Dierley Keppeke
- 1Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, OX1 3PT UK
| | - Chia Chun Chang
- 1Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, OX1 3PT UK.,2Institute of Biotechnology, National Taiwan University, Taipei, 106 Taiwan, ROC
| | - Min Peng
- 2Institute of Biotechnology, National Taiwan University, Taipei, 106 Taiwan, ROC
| | - Li-Yu Chen
- 1Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, OX1 3PT UK
| | - Wei-Cheng Lin
- 3Molecular Medicine Research Center, College of Medicine, Chang Gung University, Tao-Yuan, 333 Taiwan, ROC
| | - Li-Mei Pai
- 3Molecular Medicine Research Center, College of Medicine, Chang Gung University, Tao-Yuan, 333 Taiwan, ROC.,4Graduate Institute of Biomedical Science, College of Medicine, Chang Gung University, Tao-Yuan, 333 Taiwan, ROC.,5Department of Biochemistry, College of Medicine, Chang Gung University, Tao-Yuan, 333 Taiwan, ROC
| | - Luis Eduardo Coelho Andrade
- 6Rheumatology Division, Escola Paulista de Medicina, Universidade Federal de Sao Paulo, Sao Paulo, SP 04023-062 Brazil
| | - Li-Ying Sung
- 2Institute of Biotechnology, National Taiwan University, Taipei, 106 Taiwan, ROC.,7Agricultural Biotechnology Research Center, Academia Sinica, Taipei, 115 Taiwan, ROC
| | - Ji-Long Liu
- 1Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, OX1 3PT UK.,8School of Life Science and Technology, ShanghaiTech University, Shanghai, 201210 China
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27
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Narvaez-Ortiz HY, Lopez AJ, Gupta N, Zimmermann BH. A CTP Synthase Undergoing Stage-Specific Spatial Expression Is Essential for the Survival of the Intracellular Parasite Toxoplasma gondii. Front Cell Infect Microbiol 2018; 8:83. [PMID: 29623259 PMCID: PMC5874296 DOI: 10.3389/fcimb.2018.00083] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Accepted: 02/28/2018] [Indexed: 01/17/2023] Open
Abstract
Cytidine triphosphate synthase catalyzes the synthesis of cytidine 5′-triphosphate (CTP) from uridine 5′-triphosphate (UTP), the final step in the production of cytidine nucleotides. CTP synthases also form filamentous structures of different morphologies known as cytoophidia, whose functions in most organisms are unknown. Here, we identified and characterized a novel CTP synthase (TgCTPS) from Toxoplasma gondii. We show that TgCTPS is capable of substituting for its counterparts in the otherwise lethal double mutant (ura7Δ ura8Δ) of Saccharomyces cerevisiae. Equally, recombinant TgCTPS purified from Escherichia coli encodes for a functional protein in enzyme assays. The epitope-tagged TgCTPS under the control of its endogenous promoter displays a punctate cytosolic distribution, which undergoes spatial reorganization to form foci or filament-like structures when the parasite switches from a nutrient-replete (intracellular) to a nutrient-scarce (extracellular) condition. An analogous phenotype is observed upon nutrient stress or after treatment with a glutamine analog, 6-diazo-5-oxo-L-norleucine (DON). The exposure of parasites to DON disrupts the lytic cycle, and the TgCTPS is refractory to a genetic deletion, suggesting an essential requirement of this enzyme for T. gondii. Not least, this study, together with previous studies, supports that CTP synthase can serve as a potent drug target, because the parasite, unlike human host cells, cannot compensate for the lack of CTP synthase activity.
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Affiliation(s)
| | - Andrea J Lopez
- Departamento de Ciencias Biologicas, Universidad de los Andes, Bogota, Colombia
| | - Nishith Gupta
- Department of Molecular Parasitology, Faculty of Life Sciences, Humboldt University, Berlin, Germany
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28
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Anthony SA, Burrell AL, Johnson MC, Duong-Ly KC, Kuo YM, Simonet JC, Michener P, Andrews A, Kollman JM, Peterson JR. Reconstituted IMPDH polymers accommodate both catalytically active and inactive conformations. Mol Biol Cell 2017; 28:mbc.E17-04-0263. [PMID: 28794265 PMCID: PMC5620369 DOI: 10.1091/mbc.e17-04-0263] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Revised: 08/02/2017] [Accepted: 08/04/2017] [Indexed: 01/01/2023] Open
Abstract
Several metabolic enzymes undergo reversible polymerization into macromolecular assemblies. The function of these assemblies is often unclear but in some cases they regulate enzyme activity and metabolic homeostasis. The guanine nucleotide biosynthetic enzyme inosine monophosphate dehydrogenase (IMPDH) forms octamers that polymerize into helical chains. In mammalian cells, IMPDH filaments can associate into micron-length assemblies. Polymerization and enzyme activity are regulated in part by binding of purine nucleotides to an allosteric regulatory domain. ATP promotes octamer polymerization, whereas GTP promotes a compact, inactive conformation whose ability to polymerize is unknown. Also unclear is whether polymerization directly alters IMPDH catalytic activity. To address this, we identified point mutants of human IMPDH2 that either prevent or promote polymerization. Unexpectedly, we found that polymerized and non-assembled forms of recombinant IMPDH have comparable catalytic activity, substrate affinity, and GTP sensitivity and validated this finding in cells. Electron microscopy revealed that substrates and allosteric nucleotides shift the equilibrium between active and inactive conformations in both the octamer and the filament. Unlike other metabolic filaments, which selectively stabilize active or inactive conformations, recombinant IMPDH filaments accommodate multiple states. These conformational states are finely tuned by substrate availability and purine balance, while polymerization may allow cooperative transitions between states.
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Affiliation(s)
- Sajitha A Anthony
- Cancer Biology Program, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111
| | - Anika L Burrell
- Department of Biochemistry, University of Washington, 1959 NE Pacific Street, Box 357350, Seattle, WA 98195
| | - Matthew C Johnson
- Department of Biochemistry, University of Washington, 1959 NE Pacific Street, Box 357350, Seattle, WA 98195
| | - Krisna C Duong-Ly
- Cancer Biology Program, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111
| | - Yin-Ming Kuo
- Cancer Biology Program, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111
| | - Jacqueline C Simonet
- Cancer Biology Program, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111
| | - Peter Michener
- Department of Biochemistry & Molecular Biology, Drexel University College of Medicine, 245 N. 15th Street, Philadelphia, PA 19102
| | - Andrew Andrews
- Cancer Biology Program, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111
| | - Justin M Kollman
- Department of Biochemistry, University of Washington, 1959 NE Pacific Street, Box 357350, Seattle, WA 98195
| | - Jeffrey R Peterson
- Cancer Biology Program, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111
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29
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Chitrakar I, Kim-Holzapfel DM, Zhou W, French JB. Higher order structures in purine and pyrimidine metabolism. J Struct Biol 2017; 197:354-364. [PMID: 28115257 DOI: 10.1016/j.jsb.2017.01.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Revised: 01/14/2017] [Accepted: 01/18/2017] [Indexed: 10/20/2022]
Abstract
The recent discovery of several forms of higher order protein structures in cells has shifted the paradigm of how we think about protein organization and metabolic regulation. These dynamic and controllable protein assemblies, which are composed of dozens or hundreds of copies of an enzyme or related enzymes, have emerged as important players in myriad cellular processes. We are only beginning to appreciate the breadth of function of these types of macromolecular assemblies. These higher order structures, which can be assembled in response to varied cellular stimuli including changing metabolite concentrations or signaling cascades, give the cell the capacity to modulate levels of biomolecules both temporally and spatially. This provides an added level of control with distinct kinetics and unique features that can be harnessed as a subtle, yet powerful regulatory mechanism. Due, in large part, to advances in structural methods, such as crystallography and cryo-electron microscopy, and the advent of super-resolution microscopy techniques, a rapidly increasing number of these higher order structures are being identified and characterized. In this review, we detail what is known about the structure, function and control mechanisms of these mesoscale protein assemblies, with a particular focus on those involved in purine and pyrimidine metabolism. These structures have important implications both for our understanding of fundamental cellular processes and as fertile ground for new targets for drug discovery and development.
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Affiliation(s)
- Iva Chitrakar
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794, United States
| | - Deborah M Kim-Holzapfel
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794, United States
| | - Weijie Zhou
- Department of Chemistry, Stony Brook University, Stony Brook, NY 11794, United States
| | - Jarrod B French
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794, United States; Department of Chemistry, Stony Brook University, Stony Brook, NY 11794, United States.
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30
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Noble JW, Hunter DV, Roskelley CD, Chan EKL, Mills J. Loukoumasomes Are Distinct Subcellular Structures from Rods and Rings and Are Structurally Associated with MAP2 and the Nuclear Envelope in Retinal Cells. PLoS One 2016; 11:e0165162. [PMID: 27798680 PMCID: PMC5087950 DOI: 10.1371/journal.pone.0165162] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 10/07/2016] [Indexed: 12/19/2022] Open
Abstract
“Rods and rings” (RR) and loukoumasomes are similarly shaped, subcellular macromolecular structures with as yet unknown function. RR, so named because of their shape, are formed in response to inhibition in the GTP or CTP synthetic pathways and are highly enriched in the two key enzymes of the nucleotide synthetic pathway. Loukoumasomes also occur as linear and toroidal bodies and were initially inferred to be the same as RR, largely due to their shared shape and size and the fact that it was unclear if they shared the same subcomponents. In human retinoblastoma tissue and cells we have observed toroidal, perinuclear, macromolecular structures of similar size and antigenicity to those previously reported in neurons (neuronal-loukoumasomes). To further characterize the subcomponents of the retinal-loukoumasomes, confocal analysis following immunocytochemical staining for alpha-tubulin, beta-III tubulin and detyrosinated tubulin was performed. These studies indicate that retinal-loukoumasomes are enriched for beta-III tubulin and other tubulins associated with microtubules. Immunofluorescence together with the in situ proximity ligation assay (PLA), confirmed that beta-III tubulin colocalized with detyrosinated tubulin within loukoumasomes. Our results indicate that these tissues contain only loukoumasomes because these macromolecular structures are immunoreactive with an anti-tubulin antibody but are not recognized by the prototype anti-RR/inosine monophosphate dehydrogenase (IMPDH) antibody (It2006). To further compare the RR and retinal-loukoumasomes, retinoblastoma cells were exposed to the IMPDH-inhibitor ribavirin, a drug known to induce the formation of RR. In contrast to RR, the production of retinal-loukoumasomes was unaffected. Coimmunostaining of Y79 cells for beta-III tubulin and IMPDH indicate that these cells, when treated with ribavirin, can contain both retinal-loukoumasomes and RR and that these structures are antigenically distinct. Subcellular fractionation studies indicate that ribavirin increased the RR subcomponent, IMPDH, in the nuclear fraction of Y79 cells from 21.3 ± 5.8% (0 mM ribavirin) to 122.8 ± 7.9% (1 mM ribavirin) while the subcellular localization of the retinal-loukoumasome subcomponent tubulin went unaltered. Further characterization of retinal-loukoumasomes in retinoblastoma cells reveals that they are intimately associated with lamin folds within the nuclear envelope. Using immunofluorescence and the in situ PLA in this cell type, we have observed colocalization of beta-III tubulin with MAP2. As MAP2 is a microtubule-associated protein implicated in microtubule crosslinking, this supports a role for microtubule crosslinkers in the formation of retinal-loukoumasomes. Together, these results suggest that loukoumasomes and RR are distinct subcellular macromolecular structures, formed by different cellular processes and that there are other loukoumasome-like structures within retinal tissues and cells.
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Affiliation(s)
- Jake W. Noble
- Department of Biology, Trinity Western University, Langley, British Columbia, Canada
| | - Diana V. Hunter
- International Collaboration on Repair Discoveries (ICORD), University of British Columbia, Vancouver, British Columbia, Canada
| | - Calvin D. Roskelley
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Edward K. L. Chan
- Department of Oral Biology, University of Florida, Gainesville, Florida, United States of America
| | - Julia Mills
- Department of Biology, Trinity Western University, Langley, British Columbia, Canada
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
- * E-mail:
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31
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Keppeke GD, Prado MS, Nunes E, Perazzio SF, Rodrigues SH, Ferraz MLG, Chan EKL, Andrade LEC. Differential capacity of therapeutic drugs to induce Rods/Rings structures in vitro and in vivo and generation of anti-Rods/Rings autoantibodies. Clin Immunol 2016; 173:149-156. [PMID: 27746381 DOI: 10.1016/j.clim.2016.10.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 09/26/2016] [Accepted: 10/09/2016] [Indexed: 12/27/2022]
Abstract
Some HCV patients using ribavirin and interferon alpha (IFN-α) develop anti-rods and rings (RR) autoantibodies, the main target of which is inosine monophosphate dehydrogenase (IMPDH), the rate-determining enzyme in de novo GTP biosynthesis. In vitro inhibition of IMPDH by ribavirin induces RR formation. Here we investigate whether other commonly used drugs that interfere with GTP biosynthesis can induce RR structures in vitro and vivo and elicit generation of autoantibodies. HEp-2 cells treated for 24h with ribavirin, mycophenolic acid (MPA), azathioprine, methotrexate or acyclovir were positive for RR structures. However, adefovir, entecavir, tenofovir and lamivudine did not induce RR structures in these cells. Structures induced by ribavirin in HEp-2 cells are stable after 24h drug-washout, while structures induced by other drugs are relatively labile, disappearing within 2h. Looking at patients treated with these drugs, HCV patients treated with ribavirin (n=17) showed higher average percentage of RR-positive peripheral mononuclear cells than autoimmune patients treated with RR-inducing immunosuppressant drugs (n=21). Serum from 173 autoimmune patients who had been treated with MPA, azathioprine or methotrexate was tested for presence of anti-RR autoantibodies, and only one sample was found to be positive. Conversely, of 48 anti-RR autoantibody positive samples identified at Fleury Laboratories over 30months, 94% were from HCV patients treated with ribavirin plus IFN-α. These data indicate that RR structures can be induced by a variety of drugs in vitro and in vivo, but anti-RR autoantibody production is mostly restricted to HCV patients under ribavirin+IFN-α treatment.
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Affiliation(s)
- Gerson Dierley Keppeke
- Rheumatology Division, Federal University of Sao Paulo, Sao Paulo, SP 04023-062, Brazil.
| | - Monica Simon Prado
- Rheumatology Division, Federal University of Sao Paulo, Sao Paulo, SP 04023-062, Brazil
| | - Eunice Nunes
- Gastroenterology Division, Federal University of Sao Paulo, Sao Paulo, SP 04023-062, Brazil
| | - Sandro Felix Perazzio
- Rheumatology Division, Federal University of Sao Paulo, Sao Paulo, SP 04023-062, Brazil; Immunology Division, Fleury Medicine and Health Laboratories, Sao Paulo SP 04102-050, Brazil
| | | | | | - Edward K L Chan
- Department of Oral Biology, University of Florida, Gainesville, FL 32610-0424, USA
| | - Luis Eduardo Coelho Andrade
- Rheumatology Division, Federal University of Sao Paulo, Sao Paulo, SP 04023-062, Brazil; Immunology Division, Fleury Medicine and Health Laboratories, Sao Paulo SP 04102-050, Brazil.
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32
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Liu JL. The Cytoophidium and Its Kind: Filamentation and Compartmentation of Metabolic Enzymes. Annu Rev Cell Dev Biol 2016; 32:349-372. [DOI: 10.1146/annurev-cellbio-111315-124907] [Citation(s) in RCA: 88] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Ji-Long Liu
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, United Kingdom;
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China;
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Habrian C, Chandrasekhara A, Shahrvini B, Hua B, Lee J, Jesinghaus R, Barry R, Gitai Z, Kollman J, Baldwin EP. Inhibition of Escherichia coli CTP Synthetase by NADH and Other Nicotinamides and Their Mutual Interactions with CTP and GTP. Biochemistry 2016; 55:5554-5565. [PMID: 27571563 DOI: 10.1021/acs.biochem.6b00383] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
CTP synthetases catalyze the last step of pyrimidine biosynthesis and provide the sole de novo source of cytosine-containing nucleotides. As a central regulatory hub, they are regulated by ribonucleotide and enzyme concentration through ATP and UTP substrate availability, CTP product inhibition, GTP allosteric modification, and quaternary structural changes including the formation of CTP-inhibited linear polymers (filaments). Here, we demonstrate that nicotinamide redox cofactors are moderate inhibitors of Escherichia coli CTP synthetase (EcCTPS). NADH and NADPH are the most potent, and the primary inhibitory determinant is the reduced nicotinamide ring. Although nicotinamide inhibition is noncompetitive with substrates, it apparently enhances CTP product feedback inhibition and GTP allosteric regulation. Further, CTP and GTP also enhance each other's effects, consistent with the idea that NADH, CTP, and GTP interact with a common intermediate enzyme state. A filament-blocking mutation that reduces CTP inhibitory effects also reduced inhibition by GTP but not NADH. Protein-concentration effects on GTP inhibition suggest that, like CTP, GTP preferentially binds to the filament. All three compounds display nearly linear dose-dependent inhibition, indicating a complex pattern of cooperative interactions between binding sites. The apparent synergy between inhibitors, in consideration with physiological nucleotide concentrations, points to metabolically relevant inhibition by nicotinamides, and implicates cellular redox state as a regulator of pyrimidine biosynthesis.
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Affiliation(s)
- Chris Habrian
- Department of Molecular and Cellular Biology, University of California, Davis , Davis, California 95616, United States.,Biophysics Graduate Program, University of California, Berkeley , Berkeley, California 94720, United States
| | - Adithi Chandrasekhara
- Department of Molecular and Cellular Biology, University of California, Davis , Davis, California 95616, United States.,Process Development Rotation Program, Genentech Inc. , 1 DNA Way, South San Francisco, California 94080, United States
| | - Bita Shahrvini
- Department of Molecular and Cellular Biology, University of California, Davis , Davis, California 95616, United States
| | - Brian Hua
- Department of Molecular and Cellular Biology, University of California, Davis , Davis, California 95616, United States.,Department of Biology, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
| | - Jason Lee
- Department of Molecular and Cellular Biology, University of California, Davis , Davis, California 95616, United States.,Drexel University College of Medicine , Philadelphia, Pennsylvania 19129, United States.,Kaiser Permanente , Sacramento, California 95823, United States
| | - Roger Jesinghaus
- Department of Molecular and Cellular Biology, University of California, Davis , Davis, California 95616, United States
| | - Rachael Barry
- Department of Molecular Biology, Princeton University , Princeton, New Jersey 08544, United States.,Department of Cellular and Molecular Medicine, University of California, San Diego , La Jolla, California 92903, United States
| | - Zemer Gitai
- Department of Molecular Biology, Princeton University , Princeton, New Jersey 08544, United States
| | - Justin Kollman
- Department of Biochemistry, University of Washington , Seattle, Washington 98195, United States
| | - Enoch P Baldwin
- Department of Molecular and Cellular Biology, University of California, Davis , Davis, California 95616, United States
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Calise SJ, Purich DL, Nguyen T, Saleem DA, Krueger C, Yin JD, Chan EKL. 'Rod and ring' formation from IMP dehydrogenase is regulated through the one-carbon metabolic pathway. J Cell Sci 2016; 129:3042-52. [PMID: 27343244 DOI: 10.1242/jcs.183400] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Accepted: 06/21/2016] [Indexed: 12/29/2022] Open
Abstract
'Rods and rings' (RRs) are conserved, non-membrane-bound intracellular polymeric structures composed, in part, of inosine monophosphate dehydrogenase (IMPDH), a key enzyme leading to GMP and GTP biosynthesis. RR formation is induced by IMPDH inhibitors as well as glutamine deprivation. They also form upon treatment of cells with glutamine synthetase inhibitors. We now report that depriving cells of serine and glycine promotes RR formation, and we have traced these effects to dihydrofolate reductase (DHFR) and serine hydroxymethyltransferase-2 (SHMT2), pivotal enzymes in one-carbon metabolism and nucleotide biosynthesis. RR assembly is likewise induced upon DHFR inhibition by methotrexate or aminopterin as well as siRNA-mediated knockdown of DHFR or SHMT2. Because RR assembly occurs when guanine nucleotide biosynthesis is inhibited, and because RRs rapidly disassemble after the addition of guanine nucleotide precursors, RR formation might be an adaptive homeostatic mechanism, allowing IMPDH to sense changes in the one-carbon folate pathway.
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Affiliation(s)
- S John Calise
- Department of Oral Biology, University of Florida, 1395 Center Drive, Gainesville, FL 32610-0424, USA
| | - Daniel L Purich
- Department of Biochemistry and Molecular Biology, University of Florida, 1200 Newell Drive, Gainesville, FL 32610-0245, USA
| | - Thuy Nguyen
- Department of Oral Biology, University of Florida, 1395 Center Drive, Gainesville, FL 32610-0424, USA
| | - Dania A Saleem
- Department of Oral Biology, University of Florida, 1395 Center Drive, Gainesville, FL 32610-0424, USA
| | - Claire Krueger
- Department of Oral Biology, University of Florida, 1395 Center Drive, Gainesville, FL 32610-0424, USA
| | - Joyce D Yin
- Department of Oral Biology, University of Florida, 1395 Center Drive, Gainesville, FL 32610-0424, USA
| | - Edward K L Chan
- Department of Oral Biology, University of Florida, 1395 Center Drive, Gainesville, FL 32610-0424, USA
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Chan EKL, Damoiseaux J, de Melo Cruvinel W, Carballo OG, Conrad K, Francescantonio PLC, Fritzler MJ, Garcia-De La Torre I, Herold M, Mimori T, Satoh M, von Mühlen CA, Andrade LEC. Report on the second International Consensus on ANA Pattern (ICAP) workshop in Dresden 2015. Lupus 2016; 25:797-804. [DOI: 10.1177/0961203316640920] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The second meeting for the International Consensus on Antinuclear antibody (ANA) Pattern (ICAP) was held on 22 September 2015, one day prior to the opening of the 12th Dresden Symposium on Autoantibodies in Dresden, Germany. The ultimate goal of ICAP is to promote harmonization and understanding of autoantibody nomenclature, and thereby optimizing ANA usage in patient care. The newly developed ICAP website www.ANApatterns.org was introduced to the more than 50 participants. This was followed by several presentations and discussions focusing on key issues including the two-tier classification of ANA patterns into competent-level versus expert-level, the consideration of how to report composite versus mixed ANA patterns, and the necessity for developing a consensus on how ANA results should be reported. The need to establish on-line training modules to help users gain competency in identifying ANA patterns was discussed as a future addition to the website. To advance the ICAP goal of promoting wider international participation, it was agreed that there should be a consolidated plan to translate consensus documents into other languages by recruiting help from members of the respective communities.
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Affiliation(s)
- E K L Chan
- Department of Oral Biology, University of Florida, Gainesville, Florida, USA
| | - J Damoiseaux
- Central Diagnostic Laboratory, Maastricht University Medical Center, Maastricht, The Netherlands
| | | | - O G Carballo
- Laboratory of Immunology, Hospital Carlos G. Durand, and Department of Immunology, Instituto Universitario del Hospital Italiano, Buenos Aires, Argentina
| | - K Conrad
- Institute of Immunology, Technical University of Dresden, Dresden, Germany
| | | | - M J Fritzler
- Department of Medicine, Cumming School of Medicine, University of Calgary, Calgary, Canada
| | - I Garcia-De La Torre
- Department of Immunology and Rheumatology, Hospital General de Occidente and University of Guadalajara, Guadalajara, Mexico
| | - M Herold
- Department of Internal Medicine VI, Medical University of Innsbruck, Innsbruck, Austria
| | - T Mimori
- Department of the Control for Rheumatic Diseases and Department of Rheumatology and Clinical Immunology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - M Satoh
- Department of Clinical Nursing, University of Occupational and Environmental Health, Kitakyushu, Japan
| | | | - L E C Andrade
- Rheumatology Division, Escola Paulista de Medicina, Universidade Federal de São Paulo; Immunology Division, Fleury Medicine and Health Laboratories, São Paulo, Brazil
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Keppeke GD, Calise SJ, Chan EKL, Andrade LEC. Anti-rods/rings autoantibody generation in hepatitis C patients during interferon-α/ribavirin therapy. World J Gastroenterol 2016; 22:1966-1974. [PMID: 26877604 PMCID: PMC4726672 DOI: 10.3748/wjg.v22.i6.1966] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Revised: 11/04/2015] [Accepted: 11/24/2015] [Indexed: 02/06/2023] Open
Abstract
Chronic inflammation associated with hepatitis C virus (HCV) infection can lead to disabling liver diseases with progression to liver cirrhosis and hepatocellular carcinoma. Despite the recent availability of more effective and less toxic therapeutic options, in most parts of the world the standard treatment consists of a weekly injection of pegylated interferon α (IFN-α) together with a daily dose of ribavirin. HCV patients frequently present circulating non-organ-specific autoantibodies demonstrating a variety of staining patterns in the indirect immunofluorescence assay for antinuclear antibodies (ANA). Between 20% to 40% of HCV patients treated with IFN-α and ribavirin develop autoantibodies showing a peculiar ANA pattern characterized as rods and rings (RR) structures. The aim of this article is to review the recent reports regarding RR structures and anti-rods/rings (anti-RR) autoantibody production by HCV patients after IFN-α/ribavirin treatment. Anti-RR autoantibodies first appear around the sixth month of treatment and reach a plateau around the twelfth month. After treatment completion, anti-RR titers decrease/disappear in half the patients and remain steady in the other half. Some studies have observed a higher frequency of anti-RR antibodies in relapsers, i.e., patients in which circulating virus reappears after initially successful therapy. The main target of anti-RR autoantibodies in HCV patients is inosine-5’-monophosphate dehydrogenase 2 (IMPDH2), the rate-limiting enzyme involved in the guanosine triphosphate biosynthesis pathway. Ribavirin is a direct IMPDH2 inhibitor and is able to induce the formation of RR structures in vitro and in vivo. In conclusion, these observations led to the hypothesis that anti-RR autoantibody production is a human model of immunologic tolerance breakdown that allows us to explore the humoral autoimmune response from the beginning of the putative triggering event: exposure to ribavirin and interferon.
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Kohnhorst CL, Schmitt DL, Sundaram A, An S. Subcellular functions of proteins under fluorescence single-cell microscopy. BIOCHIMICA ET BIOPHYSICA ACTA 2016; 1864:77-84. [PMID: 26025769 PMCID: PMC5679394 DOI: 10.1016/j.bbapap.2015.05.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2015] [Revised: 05/08/2015] [Accepted: 05/18/2015] [Indexed: 11/25/2022]
Abstract
A cell is a highly organized, dynamic, and intricate biological entity orchestrated by a myriad of proteins and their self-assemblies. Because a protein's actions depend on its coordination in both space and time, our curiosity about protein functions has extended from the test tube into the intracellular space of the cell. Accordingly, modern technological developments and advances in enzymology have been geared towards analyzing protein functions within intact single cells. We discuss here how fluorescence single-cell microscopy has been employed to identify subcellular locations of proteins, detect reversible protein-protein interactions, and measure protein activity and kinetics in living cells. Considering that fluorescence single-cell microscopy has been only recently recognized as a primary technique in enzymology, its potentials and outcomes in studying intracellular protein functions are projected to be immensely useful and enlightening. We anticipate that this review would inspire many investigators to study their proteins of interest beyond the conventional boundary of specific disciplines. This article is part of a Special Issue entitled: Physiological Enzymology and Protein Functions.
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Affiliation(s)
- Casey L Kohnhorst
- Department of Chemistry and Biochemistry, University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250, USA
| | - Danielle L Schmitt
- Department of Chemistry and Biochemistry, University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250, USA
| | - Anand Sundaram
- Department of Chemistry and Biochemistry, University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250, USA
| | - Songon An
- Department of Chemistry and Biochemistry, University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250, USA.
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Pyrimidine Metabolism: Dynamic and Versatile Pathways in Pathogens and Cellular Development. J Genet Genomics 2015; 42:195-205. [PMID: 26059768 DOI: 10.1016/j.jgg.2015.04.004] [Citation(s) in RCA: 91] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Revised: 04/13/2015] [Accepted: 04/14/2015] [Indexed: 11/21/2022]
Abstract
The importance of pyrimidines lies in the fact that they are structural components of a broad spectrum of key molecules that participate in diverse cellular functions, such as synthesis of DNA, RNA, lipids, and carbohydrates. Pyrimidine metabolism encompasses all enzymes involved in the synthesis, degradation, salvage, interconversion and transport of these molecules. In this review, we summarize recent publications that document how pyrimidine metabolism changes under a variety of conditions, including, when possible, those studies based on techniques of genomics, transcriptomics, proteomics, and metabolomics. First, we briefly look at the dynamics of pyrimidine metabolism during nonpathogenic cellular events. We then focus on changes that pathogen infections cause in the pyrimidine metabolism of their host. Next, we discuss the effects of antimetabolites and inhibitors, and finally we consider the consequences of genetic manipulations, such as knock-downs, knock-outs, and knock-ins, of pyrimidine enzymes on pyrimidine metabolism in the cell.
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Keppeke GD, Calise SJ, Chan EKL, Andrade LEC. Assembly of IMPDH2-based, CTPS-based, and mixed rod/ring structures is dependent on cell type and conditions of induction. J Genet Genomics 2015; 42:287-99. [PMID: 26165495 DOI: 10.1016/j.jgg.2015.04.002] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2014] [Revised: 04/07/2015] [Accepted: 04/09/2015] [Indexed: 02/07/2023]
Abstract
Inhibition of guanosine triphosphate (GTP) and cytidine triphosphate (CTP) biosynthetic pathways induces cells to assemble rod/ring (RR) structures, also named cytoophidia, which consist of the enzymes cytidine triphosphate synthase (CTPS) and inosine-5'-monophosphate dehydrogenase 2 (IMPDH2). We aim to explore the interaction of CTPS and IMPDH2 in the generation of RR structures. HeLa and COS-7 cells were cultured in normal conditions or in the presence of 6-diazo-5-oxo-L-norleucine (DON), ribavirin, or mycophenolic acid (MPA). Over 90% of DON-treated cells presented RR structures. In HeLa cells, 35% of the RR structures were positive for IMPDH2 alone, 26% were CTPS alone, and 31% were IMPDH2/CTPS mixed, while in COS-7 cells, 42% of RR were IMPDH2 alone, 41% were CTPS alone, and 10% were IMPDH2/CTPS mixed. Ribavirin and MPA treatments induced only IMPDH2-based RR. Cells were also transfected with an N-terminal hemagglutinin (NHA)-tagged CTPS1 construct. Over 95% of NHA-CTPS1 transfected cells with DON treatment presented IMPDH2-based RR and almost 100% presented CTPS1-based RR; when treated with ribavirin, over 94% of transfected cells presented IMPDH2-based RR and 37% presented CTPS1-based RR, whereas 2% of untreated transfected cells presented IMPDH2-based RR and 28% presented CTPS1-based RR. These results may help in understanding the relationship between CTP and GTP biosynthetic pathways, especially concerning the formation of filamentous RR structures.
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Affiliation(s)
- Gerson Dierley Keppeke
- Rheumatology Division, Federal University of Sao Paulo, Sao Paulo SP 04023-062, Brazil; Department of Oral Biology, University of Florida, Gainesville FL 32610-0424, USA.
| | - S John Calise
- Department of Oral Biology, University of Florida, Gainesville FL 32610-0424, USA
| | - Edward K L Chan
- Department of Oral Biology, University of Florida, Gainesville FL 32610-0424, USA
| | - Luis Eduardo C Andrade
- Rheumatology Division, Federal University of Sao Paulo, Sao Paulo SP 04023-062, Brazil; Immunology Division, Fleury Medicine and Health Laboratories, Sao Paulo SP 04102-050, Brazil.
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Calise SJ, Keppeke GD, Andrade LEC, Chan EKL. Anti-rods/rings: a human model of drug-induced autoantibody generation. Front Immunol 2015; 6:41. [PMID: 25699057 PMCID: PMC4318423 DOI: 10.3389/fimmu.2015.00041] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Accepted: 01/21/2015] [Indexed: 12/17/2022] Open
Abstract
In recent years, autoantibodies targeting subcellular structures described as the rods and rings pattern in HEp-2 ANA have been presented as a unique case of autoantibody generation. These rod and ring structures (RR) are at least partially composed of inosine monophosphate dehydrogenase type 2 (IMPDH2), and their formation can be induced in vitro by several small-molecule inhibitors, including some IMPDH2 inhibitors. Autoantibodies targeting these relatively unknown structures have been almost exclusively observed in hepatitis C virus (HCV) patients who have undergone treatment with pegylated interferon-α/ribavirin (IFN/RBV) combination therapy. To date, anti-RR antibodies have not been found in treatment-naïve HCV patients or in patients from any other disease groups, with few reported exceptions. Here, we describe recent advances in characterizing the RR structure and the strong association between anti-RR antibody response and HCV patients treated with IFN/RBV, detailing why anti-RR can be considered a human model of drug-induced autoantibody generation.
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Affiliation(s)
- S John Calise
- Department of Oral Biology, University of Florida , Gainesville, FL , USA
| | - Gerson D Keppeke
- Rheumatology Division, Universidade Federal de São Paulo , São Paulo , Brazil
| | - Luis E C Andrade
- Rheumatology Division, Universidade Federal de São Paulo , São Paulo , Brazil ; Fleury Medicine and Health Laboratories, Immunology Division , São Paulo , Brazil
| | - Edward K L Chan
- Department of Oral Biology, University of Florida , Gainesville, FL , USA
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Keppeke GD, Andrade LEC, Grieshaber SS, Chan EKL. Microinjection of specific anti-IMPDH2 antibodies induces disassembly of cytoplasmic rods/rings that are primarily stationary and stable structures. Cell Biosci 2015; 5:1. [PMID: 25601894 PMCID: PMC4298086 DOI: 10.1186/2045-3701-5-1] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Accepted: 12/18/2014] [Indexed: 02/08/2023] Open
Abstract
BACKGROUND Our laboratory previously reported interesting rods 3-10 μm long and rings 2-5 μm diameter (RR) in the cytoplasm of mammalian cells. Experimental evidence show that both inosine-5'-monophosphate dehydrogenase 2 (IMPDH2) and cytidine triphosphate synthetase (CTPS) are components of RR structures. Several cell types, including mouse embryonic stem cells, and cell lines, such as mouse 3 T3 and rat NRK, naturally present RR structures, while other cells can present RR when treated with compounds interfering with GTP/CTP biosynthetic pathways. In this study, we aimed to investigate the dynamic behavior of these RR in live cells. RESULTS RR were detected in >90% of COS-7 and HeLa cells treated with 1 mM ribavirin or 6-Diazo-5-oxo-L-norleucine (DON) for 24 h, and in 75% of COS-7 cells treated with 1 mM mycophenolic acid (MPA) for the same period of time. Microinjection of affinity-purified anti-IMPDH2 antibodies in live COS-7 cells treated with ribavirin, DON, or MPA showed mature forms of RR presented as stable and stationary structures in 71% of cells. In the remaining 29% of cells, RR acquired erratic movement and progressively disassembled into fragments and disappeared within 10 min. The specific stationary state and antibody-dependent disassembling of RR structures was independently confirmed in COS-7 and HeLa cells transfected with GFP-tagged IMPDH2. CONCLUSIONS This is the first demonstration of disassembly of RR structures upon microinjection of anti-IMPDH2 antibodies that led to the disappearance of the molecular aggregates. The disassembly of RR after microinjection of anti-IMPDH2 antibody further strengthens the notion that IMPDH2 are major building blocks of RR. Using two independent methods, this study demonstrated that the induced RR are primarily stationary structures in live cells and that IMPDH2 is a key component of RR.
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Affiliation(s)
- Gerson Dierley Keppeke
- />Department of Oral Biology, University of Florida, 1395 Center Drive, Gainesville, FL 32610-0424 USA
- />Rheumatology Division, Universidade Federal de São Paulo, Rua Botucatu 740, São Paulo, SP 04023-062 Brazil
| | - Luís Eduardo C Andrade
- />Rheumatology Division, Universidade Federal de São Paulo, Rua Botucatu 740, São Paulo, SP 04023-062 Brazil
- />Immunology Division, Fleury Medicine and Health Laboratories, Avenida Gal Waldomiro Lima 508, São Paulo, SP 04102-050 Brazil
| | - Scott S Grieshaber
- />Department of Biological Sciences, University of Idaho, 875 Center Drive, Moscow, ID 83844 USA
| | - Edward K L Chan
- />Department of Oral Biology, University of Florida, 1395 Center Drive, Gainesville, FL 32610-0424 USA
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Strochlic TI, Stavrides KP, Thomas SV, Nicolas E, O'Reilly AM, Peterson JR. Ack kinase regulates CTP synthase filaments during Drosophila oogenesis. EMBO Rep 2014; 15:1184-91. [PMID: 25223282 DOI: 10.15252/embr.201438688] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The enzyme CTP synthase (CTPS) dynamically assembles into macromolecular filaments in bacteria, yeast, Drosophila, and mammalian cells, but the role of this morphological reorganization in regulating CTPS activity is controversial. During Drosophila oogenesis, CTPS filaments are transiently apparent in ovarian germline cells during a period of intense genomic endoreplication and stockpiling of ribosomal RNA. Here, we demonstrate that CTPS filaments are catalytically active and that their assembly is regulated by the non-receptor tyrosine kinase DAck, the Drosophila homologue of mammalian Ack1 (activated cdc42-associated kinase 1), which we find also localizes to CTPS filaments. Egg chambers from flies deficient in DAck or lacking DAck catalytic activity exhibit disrupted CTPS filament architecture and morphological defects that correlate with reduced fertility. Furthermore, ovaries from these flies exhibit reduced levels of total RNA, suggesting that DAck may regulate CTP synthase activity. These findings highlight an unexpected function for DAck and provide insight into a novel pathway for the developmental control of an essential metabolic pathway governing nucleotide biosynthesis.
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Affiliation(s)
- Todd I Strochlic
- Cancer Biology Program, Fox Chase Cancer Center, Philadelphia, PA, USA
| | - Kevin P Stavrides
- Cancer Biology Program, Fox Chase Cancer Center, Philadelphia, PA, USA Epigenetics and Progenitor Cells Keystone Program, Fox Chase Cancer Center, Philadelphia, PA, USA
| | - Sam V Thomas
- Cancer Biology Program, Fox Chase Cancer Center, Philadelphia, PA, USA
| | | | - Alana M O'Reilly
- Cancer Biology Program, Fox Chase Cancer Center, Philadelphia, PA, USA Epigenetics and Progenitor Cells Keystone Program, Fox Chase Cancer Center, Philadelphia, PA, USA
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Barry RM, Bitbol AF, Lorestani A, Charles EJ, Habrian CH, Hansen JM, Li HJ, Baldwin EP, Wingreen NS, Kollman JM, Gitai Z. Large-scale filament formation inhibits the activity of CTP synthetase. eLife 2014; 3:e03638. [PMID: 25030911 PMCID: PMC4126345 DOI: 10.7554/elife.03638] [Citation(s) in RCA: 122] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
CTP Synthetase (CtpS) is a universally conserved and essential metabolic enzyme. While many enzymes form small oligomers, CtpS forms large-scale filamentous structures of unknown function in prokaryotes and eukaryotes. By simultaneously monitoring CtpS polymerization and enzymatic activity, we show that polymerization inhibits activity, and CtpS's product, CTP, induces assembly. To understand how assembly inhibits activity, we used electron microscopy to define the structure of CtpS polymers. This structure suggests that polymerization sterically hinders a conformational change necessary for CtpS activity. Structure-guided mutagenesis and mathematical modeling further indicate that coupling activity to polymerization promotes cooperative catalytic regulation. This previously uncharacterized regulatory mechanism is important for cellular function since a mutant that disrupts CtpS polymerization disrupts E. coli growth and metabolic regulation without reducing CTP levels. We propose that regulation by large-scale polymerization enables ultrasensitive control of enzymatic activity while storing an enzyme subpopulation in a conformationally restricted form that is readily activatable. DOI:http://dx.doi.org/10.7554/eLife.03638.001 Enzymes are proteins that perform reactions that can convert one or more chemicals (the substrates) into others (the products). The rate at which an enzyme produces its product is often carefully regulated. Some molecules slow or stop an enzyme by binding to and blocking the site where its substrates normally bind: its ‘active site’. Other molecules can also bind to sites other than the active site, which can cause the enzyme to become either more or less active. Almost all living things have an enzyme called CTP synthetase that makes one of the building blocks that is used to build DNA and a similar molecule called RNA. This enzyme converts a molecule called uridine triphosphate (or UTP) into another called cytidine triphosphate (CTP): a reaction that is powered by breaking down molecules of adenosine triphosphate (ATP). The amount of CTP synthetase made by a cell is carefully controlled. The enzyme's activity is also regulated by the levels of UTP and CTP, and by another molecule (called GTP) that binds to a site outside of its active site. Four copies of the CTP synthetase protein must work together before this enzyme can turn UTP into CTP. The enzyme also forms much larger aggregates, or polymers; however, it is not clear what causes these polymers to form, or what they do in a cell. Barry et al. have now discovered that CTP synthetase is almost completely inactivated when these polymers are formed. Furthermore, CTP encourages the polymers to form, whilst UTP and ATP cause them to disassemble. Therefore, this enzyme is least active when there is excess product in the cell, and most active when its substrates are plentiful. By determining the three-dimensional structure of a CTP synthetase polymer, Barry et al. reveal that although CTP is bound to the enzymes, their active sites are still freely accessible. However, the enzymes in the polymer appear to be locked into a shape that makes them unable to carry out their function. When Barry et al. then mutated the enzyme so that it was unable to form polymers it was also no longer inactivated in the same way by CTP. Bacterial cells with only these mutant versions of CTP synthetase are unable to properly control their levels of CTP. This suggests that polymer formation is important for regulating this enzyme in response to a build up of its product. Further work is needed to see whether the regulation of CTP synthetase activity by forming polymers is specific to this enzyme or a widespread mechanism that is used to control other enzymes too. DOI:http://dx.doi.org/10.7554/eLife.03638.002
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Affiliation(s)
- Rachael M Barry
- Department of Molecular Biology, Princeton University, Princeton, United States
| | - Anne-Florence Bitbol
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, United States
| | - Alexander Lorestani
- Department of Molecular Biology, Princeton University, Princeton, United States
| | - Emeric J Charles
- Department of Anatomy and Cell Biology, McGill University, Montreal, Canada
| | - Chris H Habrian
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, United States
| | - Jesse M Hansen
- Department of Anatomy and Cell Biology, McGill University, Montreal, Canada
| | - Hsin-Jung Li
- Department of Molecular Biology, Princeton University, Princeton, United States
| | - Enoch P Baldwin
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, United States
| | - Ned S Wingreen
- Department of Molecular Biology, Princeton University, Princeton, United States Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, United States
| | - Justin M Kollman
- Department of Anatomy and Cell Biology, McGill University, Montreal, Canada Groupe de Recherche Axé sur la Structure des Protéines, McGill University, Montreal, Canada
| | - Zemer Gitai
- Department of Molecular Biology, Princeton University, Princeton, United States
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Juda P, Smigová J, Kováčik L, Bártová E, Raška I. Ultrastructure of cytoplasmic and nuclear inosine-5'-monophosphate dehydrogenase 2 "rods and rings" inclusions. J Histochem Cytochem 2014; 62:739-50. [PMID: 24980853 DOI: 10.1369/0022155414543853] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Inosine-5'-monophosphate dehydrogenase catalyzes the critical step in the de novo synthesis of guanosine nucleotides: the oxidation of inosine monophosphate to xanthosine monophosphate. This reaction can be inhibited by specific inhibitors, such as ribavirin or mycophenolic acid, which are widely used in clinical treatment when required to inhibit the proliferation of viruses or cells. However, it was recently found that such an inhibition affects the cells, leading to a redistribution of IMPDH2 and the appearance of IMPDH2 inclusions in the cytoplasm. According to their shape, these inclusions have been termed "Rods and Rings" (R&R). In this work, we focused on the subcellular localization of IMPDH2 protein and the ultrastructure of R&R inclusions. Using microscopy and western blot analysis, we show the presence of nuclear IMPDH2 in human cells. We also show that the nuclear pool has an ability to form Rod structures after inhibition by ribavirin. Concerning the ultrastructure, we observed that R&R inclusions in cellulo correspond to the accumulation of fibrous material that is not surrounded by a biological membrane. The individual fibers are composed of regularly repeating subunits with a length of approximately 11 nm. Together, our findings describe the localization of IMPDH2 inside the nucleus of human cells as well as the ultrastructure of R&R inclusions.
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Affiliation(s)
- Pavel Juda
- Charles University in Prague, First Faculty of Medicine, Institute of Cellular Biology and Pathology, Czech Republic (PJ, JS, LK, IR)Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Brno, Czech Republic (EB)
| | - Jana Smigová
- Charles University in Prague, First Faculty of Medicine, Institute of Cellular Biology and Pathology, Czech Republic (PJ, JS, LK, IR)Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Brno, Czech Republic (EB)
| | - Lubomír Kováčik
- Charles University in Prague, First Faculty of Medicine, Institute of Cellular Biology and Pathology, Czech Republic (PJ, JS, LK, IR)Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Brno, Czech Republic (EB)
| | - Eva Bártová
- Charles University in Prague, First Faculty of Medicine, Institute of Cellular Biology and Pathology, Czech Republic (PJ, JS, LK, IR)Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Brno, Czech Republic (EB)
| | - Ivan Raška
- Charles University in Prague, First Faculty of Medicine, Institute of Cellular Biology and Pathology, Czech Republic (PJ, JS, LK, IR)Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Brno, Czech Republic (EB)
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