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Feng A, Yang EY, Moore AR, Dhingra S, Chang SE, Yin X, Pi R, Mack EK, Völkel S, Geßner R, Gündisch M, Neubauer A, Renz H, Tsiodras S, Fragkou PC, Asuni AA, Levitt JE, Wilson JG, Leong M, Lumb JH, Mao R, Pinedo K, Roque J, Richards CM, Stabile M, Swaminathan G, Salagianni ML, Triantafyllia V, Bertrams W, Blish CA, Carette JE, Frankovich J, Meffre E, Nadeau KC, Singh U, Wang TT, Luning Prak ET, Herold S, Andreakos E, Schmeck B, Skevaki C, Rogers AJ, Utz PJ. Autoantibodies are highly prevalent in non-SARS-CoV-2 respiratory infections and critical illness. JCI Insight 2023; 8:e163150. [PMID: 36752204 PMCID: PMC9977421 DOI: 10.1172/jci.insight.163150] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Accepted: 12/14/2022] [Indexed: 02/09/2023] Open
Abstract
The widespread presence of autoantibodies in acute infection with SARS-CoV-2 is increasingly recognized, but the prevalence of autoantibodies in non-SARS-CoV-2 infections and critical illness has not yet been reported. We profiled IgG autoantibodies in 267 patients from 5 independent cohorts with non-SARS-CoV-2 viral, bacterial, and noninfectious critical illness. Serum samples were screened using Luminex arrays that included 58 cytokines and 55 autoantigens, many of which are associated with connective tissue diseases (CTDs). Samples positive for anti-cytokine antibodies were tested for receptor blocking activity using cell-based functional assays. Anti-cytokine antibodies were identified in > 50% of patients across all 5 acutely ill cohorts. In critically ill patients, anti-cytokine antibodies were far more common in infected versus uninfected patients. In cell-based functional assays, 11 of 39 samples positive for select anti-cytokine antibodies displayed receptor blocking activity against surface receptors for Type I IFN, GM-CSF, and IL-6. Autoantibodies against CTD-associated autoantigens were also commonly observed, including newly detected antibodies that emerged in longitudinal samples. These findings demonstrate that anti-cytokine and autoantibodies are common across different viral and nonviral infections and range in severity of illness.
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Affiliation(s)
- Allan Feng
- Department of Medicine, Division of Immunology and Rheumatology
- Institute for Immunity, Transplantation and Infection
| | - Emily Y. Yang
- Department of Medicine, Division of Immunology and Rheumatology
- Institute for Immunity, Transplantation and Infection
| | - Andrew Reese Moore
- Department of Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, and
| | - Shaurya Dhingra
- Department of Medicine, Division of Immunology and Rheumatology
- Institute for Immunity, Transplantation and Infection
| | - Sarah Esther Chang
- Department of Medicine, Division of Immunology and Rheumatology
- Institute for Immunity, Transplantation and Infection
| | - Xihui Yin
- Department of Medicine, Division of Immunology and Rheumatology
- Institute for Immunity, Transplantation and Infection
| | - Ruoxi Pi
- Department of Medicine, Division of Infectious Diseases, Stanford University School of Medicine, Stanford, California, USA
| | - Elisabeth K.M. Mack
- Department of Hematology, Oncology, Immunology, Philipps University Marburg, Marburg, Germany
| | - Sara Völkel
- Institute of Laboratory Medicine, Universities of Giessen and Marburg Lung Center (UGMLC), Philipps University Marburg, German Center for Lung Research (DZL), Marburg, Germany
| | - Reinhard Geßner
- Institute of Laboratory Medicine, Universities of Giessen and Marburg Lung Center (UGMLC), Philipps University Marburg, German Center for Lung Research (DZL), Marburg, Germany
| | - Margrit Gündisch
- Institute of Laboratory Medicine, Universities of Giessen and Marburg Lung Center (UGMLC), Philipps University Marburg, German Center for Lung Research (DZL), Marburg, Germany
| | - Andreas Neubauer
- Department of Hematology, Oncology, Immunology, Philipps University Marburg, Marburg, Germany
| | - Harald Renz
- Institute of Laboratory Medicine, Universities of Giessen and Marburg Lung Center (UGMLC), Philipps University Marburg, German Center for Lung Research (DZL), Marburg, Germany
| | - Sotirios Tsiodras
- 4th Department of Internal Medicine, Medical School, National and Kapodistrian University of Athens, Attikon University Hospital, Athens, Greece
| | - Paraskevi C. Fragkou
- 4th Department of Internal Medicine, Medical School, National and Kapodistrian University of Athens, Attikon University Hospital, Athens, Greece
- European Society of Clinical Microbiology and Infectious Diseases (ESCMID), Study Group for Respiratory Viruses (ESGREV), Basel, Switzerland
| | - Adijat A. Asuni
- Department of Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, and
| | - Joseph E. Levitt
- Department of Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, and
| | | | - Michelle Leong
- Department of Medicine, Division of Infectious Diseases, Stanford University School of Medicine, Stanford, California, USA
| | - Jennifer H. Lumb
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, USA
| | - Rong Mao
- Department of Medicine, Division of Immunology and Rheumatology
- Institute for Immunity, Transplantation and Infection
| | - Kassandra Pinedo
- Department of Medicine, Division of Infectious Diseases, Stanford University School of Medicine, Stanford, California, USA
| | - Jonasel Roque
- Department of Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, and
| | - Christopher M. Richards
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, USA
| | - Mikayla Stabile
- Department of Medicine, Division of Infectious Diseases, Stanford University School of Medicine, Stanford, California, USA
| | - Gayathri Swaminathan
- Department of Medicine, Division of Immunology and Rheumatology
- Institute for Immunity, Transplantation and Infection
| | - Maria L. Salagianni
- Laboratory of Immunobiology, Center for Clinical, Experimental Surgery and Translational Research, Biomedical Research Foundation of the Academy of Athens, Athens, Greece
| | - Vasiliki Triantafyllia
- Laboratory of Immunobiology, Center for Clinical, Experimental Surgery and Translational Research, Biomedical Research Foundation of the Academy of Athens, Athens, Greece
| | - Wilhelm Bertrams
- Institute for Lung Research, UGMLC, Philipps University Marburg, Marburg, Germany
| | - Catherine A. Blish
- Institute for Immunity, Transplantation and Infection
- Department of Medicine, Division of Infectious Diseases, Stanford University School of Medicine, Stanford, California, USA
- Chan Zuckerberg Biohub, San Francisco, California, USA
| | - Jan E. Carette
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, USA
| | - Jennifer Frankovich
- Department of Pediatrics, Division of Allergy, Immunology, Rheumatology, Stanford University School of Medicine, Stanford, California, USA
| | - Eric Meffre
- Department of Immunobiology, Yale University, New Haven, Connecticut, USA
| | - Kari Christine Nadeau
- Institute for Immunity, Transplantation and Infection
- Department of Medicine, Sean N. Parker Center for Allergy and Asthma Research, Stanford University School of Medicine, Stanford, California, USA
| | - Upinder Singh
- Institute for Immunity, Transplantation and Infection
- Department of Medicine, Division of Infectious Diseases, Stanford University School of Medicine, Stanford, California, USA
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, USA
| | - Taia T. Wang
- Institute for Immunity, Transplantation and Infection
- Department of Medicine, Division of Infectious Diseases, Stanford University School of Medicine, Stanford, California, USA
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, USA
- Chan Zuckerberg Biohub, San Francisco, California, USA
| | - Eline T. Luning Prak
- Department of Pathology and Laboratory Medicine and
- Institute for Immunology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Susanne Herold
- Department of Internal Medicine V, Infectious Diseases and Infection Control, UKGM, Justus Liebig University, and Institute for Lung Health (ILH), Giessen, Germany
- DZL and UGMLC, Giessen, Germany
| | - Evangelos Andreakos
- Laboratory of Immunobiology, Center for Clinical, Experimental Surgery and Translational Research, Biomedical Research Foundation of the Academy of Athens, Athens, Greece
| | - Bernd Schmeck
- Institute for Lung Research, UGMLC, Philipps University Marburg, Marburg, Germany
- Department of Medicine, Pulmonary and Critical Care Medicine, University Medical Center Marburg, Marburg, Germany
- DZL, German Center for Infection Research (DZIF), Center for Synthetic Microbiology (SYNMIKRO), Philipps University of Marburg, Marburg, Germany
| | - Chrysanthi Skevaki
- Institute of Laboratory Medicine, Universities of Giessen and Marburg Lung Center (UGMLC), Philipps University Marburg, German Center for Lung Research (DZL), Marburg, Germany
| | - Angela J. Rogers
- Department of Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, and
| | - Paul J. Utz
- Department of Medicine, Division of Immunology and Rheumatology
- Institute for Immunity, Transplantation and Infection
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Cao JY, Poddar A, Magtanong L, Lumb JH, Mileur TR, Reid MA, Dovey CM, Wang J, Locasale JW, Stone E, Cole SPC, Carette JE, Dixon SJ. A Genome-wide Haploid Genetic Screen Identifies Regulators of Glutathione Abundance and Ferroptosis Sensitivity. Cell Rep 2020; 26:1544-1556.e8. [PMID: 30726737 PMCID: PMC6424331 DOI: 10.1016/j.celrep.2019.01.043] [Citation(s) in RCA: 127] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Revised: 12/19/2018] [Accepted: 01/09/2019] [Indexed: 12/25/2022] Open
Abstract
The tripeptide glutathione suppresses the iron-dependent, non-apoptotic cell death process of ferroptosis. How glutathione abundance is regulated in the cell and how this regulation alters ferroptosis sensitivity is poorly understood. Using genome-wide human haploid genetic screening technology coupled to fluorescence-activated cell sorting (FACS), we directly identify genes that regulate intracellular glutathione abundance and characterize their role in ferroptosis regulation. Disruption of the ATP binding cassette (ABC)-family transporter multidrug resistance protein 1 (MRP1) prevents glutathione efflux from the cell and strongly inhibits ferroptosis. High levels of MRP1 expression decrease sensitivity to certain pro-apoptotic chemotherapeutic drugs, while collaterally sensitizing to all tested pro-ferroptotic agents. By contrast, disruption of KEAP1 and NAA38, leading to the stabilization of the transcription factor NRF2, increases glutathione levels but only weakly protects from ferroptosis. This is due in part to concomitant NRF2-mediated upregulation of MRP1. These results pinpoint glutathione efflux as an unanticipated regulator of ferroptosis sensitivity. Glutathione suppresses the non-apoptotic cell death process of ferroptosis. Using genome-wide human haploid cell mutagenesis and FACS-based detection, Cao et al. identify negative regulators of intracellular glutathione abundance that affect glutathione efflux and NRF2 protein levels, altering ferroptosis sensitivity.
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Affiliation(s)
| | - Aunoy Poddar
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Leslie Magtanong
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Jennifer H Lumb
- Department of Microbiology and Immunology, Stanford University, Stanford, CA 94305, USA
| | - Trevor R Mileur
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Michael A Reid
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC 27710, USA
| | - Cole M Dovey
- Department of Microbiology and Immunology, Stanford University, Stanford, CA 94305, USA
| | - Jin Wang
- Department of Pharmacology and Chemical Biology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Jason W Locasale
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC 27710, USA
| | - Everett Stone
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, USA
| | - Susan P C Cole
- Department of Pathology and Molecular Medicine and Division of Cancer Biology and Genetics, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Jan E Carette
- Department of Microbiology and Immunology, Stanford University, Stanford, CA 94305, USA
| | - Scott J Dixon
- Department of Biology, Stanford University, Stanford, CA 94305, USA.
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3
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Newton T, Allison R, Edgar JR, Lumb JH, Rodger CE, Manna PT, Rizo T, Kohl Z, Nygren AOH, Arning L, Schüle R, Depienne C, Goldberg L, Frahm C, Stevanin G, Durr A, Schöls L, Winner B, Beetz C, Reid E. Mechanistic basis of an epistatic interaction reducing age at onset in hereditary spastic paraplegia. Brain 2019; 141:1286-1299. [PMID: 29481671 PMCID: PMC5917785 DOI: 10.1093/brain/awy034] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Accepted: 01/04/2018] [Indexed: 12/20/2022] Open
Abstract
Many genetic neurological disorders exhibit variable expression within affected families, often exemplified by variations in disease age at onset. Epistatic effects (i.e. effects of modifier genes on the disease gene) may underlie this variation, but the mechanistic basis for such epistatic interactions is rarely understood. Here we report a novel epistatic interaction between SPAST and the contiguous gene DPY30, which modifies age at onset in hereditary spastic paraplegia, a genetic axonopathy. We found that patients with hereditary spastic paraplegia caused by genomic deletions of SPAST that extended into DPY30 had a significantly younger age at onset. We show that, like spastin, the protein encoded by SPAST, the DPY30 protein controls endosomal tubule fission, traffic of mannose 6-phosphate receptors from endosomes to the Golgi, and lysosomal ultrastructural morphology. We propose that additive effects on this pathway explain the reduced age at onset of hereditary spastic paraplegia in patients who are haploinsufficient for both genes.
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Affiliation(s)
- Timothy Newton
- Department of Medical Genetics and Cambridge Institute for Medical Research, University of Cambridge, UK
| | - Rachel Allison
- Department of Medical Genetics and Cambridge Institute for Medical Research, University of Cambridge, UK
| | - James R Edgar
- Department of Clinical Biochemistry and Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, UK
| | - Jennifer H Lumb
- Department of Medical Genetics and Cambridge Institute for Medical Research, University of Cambridge, UK
| | - Catherine E Rodger
- Department of Medical Genetics and Cambridge Institute for Medical Research, University of Cambridge, UK
| | - Paul T Manna
- Department of Clinical Biochemistry and Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, UK
| | - Tania Rizo
- Department of Stem Cell Biology, Friedrich-Alexander University Erlangen-Nuernberg (FAU), Erlangen, Germany
| | - Zacharias Kohl
- Department of Molecular Neurology, Friedrich-Alexander University Erlangen-Nuernberg (FAU), Erlangen, Germany
| | | | - Larissa Arning
- Department of Human Genetics, Ruhr-University, Bochum, Germany
| | - Rebecca Schüle
- Center for Neurology and Hertie Institute for Clinical Brain Research, Eberhard-Karls-University, 72076 Tübingen, Germany.,German Center of Neurodegenerative Diseases (DZNE), 72076 Tübingen, Germany
| | - Christel Depienne
- ICM Brain and Spine Institute, INSERM U1127, CNRS UMR7225, Sorbonne Universites, UPMC Univ Paris VI UMR_S1127, Paris, France.,APHP, Genetic Department, Pitie-Salpêtrière University Hospital, Paris, France
| | - Lisa Goldberg
- Department of Clinical Chemistry and Laboratory Diagnostics, Jena University Hospital, Jena, Germany
| | - Christiane Frahm
- Hans Berger Department of Neurology, Jena University Hospital, Jena, Germany
| | - Giovanni Stevanin
- ICM Brain and Spine Institute, INSERM U1127, CNRS UMR7225, Sorbonne Universites, UPMC Univ Paris VI UMR_S1127, Paris, France.,APHP, Genetic Department, Pitie-Salpêtrière University Hospital, Paris, France.,Ecole Pratique des Hautes Etudes, PSL Research University, Paris, France
| | - Alexandra Durr
- ICM Brain and Spine Institute, INSERM U1127, CNRS UMR7225, Sorbonne Universites, UPMC Univ Paris VI UMR_S1127, Paris, France.,APHP, Genetic Department, Pitie-Salpêtrière University Hospital, Paris, France
| | - Ludger Schöls
- Center for Neurology and Hertie Institute for Clinical Brain Research, Eberhard-Karls-University, 72076 Tübingen, Germany.,German Center of Neurodegenerative Diseases (DZNE), 72076 Tübingen, Germany
| | - Beate Winner
- Department of Molecular Neurology, Friedrich-Alexander University Erlangen-Nuernberg (FAU), Erlangen, Germany
| | - Christian Beetz
- Department of Clinical Chemistry and Laboratory Diagnostics, Jena University Hospital, Jena, Germany
| | - Evan Reid
- Department of Medical Genetics and Cambridge Institute for Medical Research, University of Cambridge, UK
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4
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Lumb JH, Li Q, Popov LM, Ding S, Keith MT, Merrill BD, Greenberg HB, Li JB, Carette JE. DDX6 Represses Aberrant Activation of Interferon-Stimulated Genes. Cell Rep 2018; 20:819-831. [PMID: 28746868 DOI: 10.1016/j.celrep.2017.06.085] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 05/30/2017] [Accepted: 06/28/2017] [Indexed: 12/31/2022] Open
Abstract
The innate immune system tightly regulates activation of interferon-stimulated genes (ISGs) to avoid inappropriate expression. Pathological ISG activation resulting from aberrant nucleic acid metabolism has been implicated in autoimmune disease; however, the mechanisms governing ISG suppression are unknown. Through a genome-wide genetic screen, we identified DEAD-box helicase 6 (DDX6) as a suppressor of ISGs. Genetic ablation of DDX6 induced global upregulation of ISGs and other immune genes. ISG upregulation proved cell intrinsic, imposing an antiviral state and making cells refractory to divergent families of RNA viruses. Epistatic analysis revealed that ISG activation could not be overcome by deletion of canonical RNA sensors. However, DDX6 deficiency was suppressed by disrupting LSM1, a core component of mRNA degradation machinery, suggesting that dysregulation of RNA processing underlies ISG activation in the DDX6 mutant. DDX6 is distinct among DExD/H helicases that regulate the antiviral response in its singular ability to negatively regulate immunity.
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Affiliation(s)
- Jennifer H Lumb
- Department of Microbiology and Immunology, Stanford University, Stanford, CA 94305, USA
| | - Qin Li
- Department of Genetics, Stanford University, Stanford, CA 94305, USA
| | - Lauren M Popov
- Department of Microbiology and Immunology, Stanford University, Stanford, CA 94305, USA
| | - Siyuan Ding
- Department of Microbiology and Immunology, Stanford University, Stanford, CA 94305, USA; Division of Gastroenterology and Hepatology, Department of Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA; Palo Alto Veterans Institute of Research, VA Palo Alto Health Care System, Palo Alto, CA 94304, USA
| | - Marie T Keith
- Department of Microbiology and Immunology, Stanford University, Stanford, CA 94305, USA
| | - Bryan D Merrill
- Department of Microbiology and Immunology, Stanford University, Stanford, CA 94305, USA
| | - Harry B Greenberg
- Department of Microbiology and Immunology, Stanford University, Stanford, CA 94305, USA; Division of Gastroenterology and Hepatology, Department of Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA; Palo Alto Veterans Institute of Research, VA Palo Alto Health Care System, Palo Alto, CA 94304, USA
| | - Jin Billy Li
- Department of Genetics, Stanford University, Stanford, CA 94305, USA
| | - Jan E Carette
- Department of Microbiology and Immunology, Stanford University, Stanford, CA 94305, USA.
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Allison R, Lumb JH, Fassier C, Connell JW, Ten Martin D, Seaman MNJ, Hazan J, Reid E. An ESCRT-spastin interaction promotes fission of recycling tubules from the endosome. ACTA ACUST UNITED AC 2013; 202:527-43. [PMID: 23897888 PMCID: PMC3734076 DOI: 10.1083/jcb.201211045] [Citation(s) in RCA: 118] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Inclusion of IST1 into the ESCRT complex allows recruitment of the microtubule-severing protein spastin to promote fission of recycling tubules from the endosome. Mechanisms coordinating endosomal degradation and recycling are poorly understood, as are the cellular roles of microtubule (MT) severing. We show that cells lacking the MT-severing protein spastin had increased tubulation of and defective receptor sorting through endosomal tubular recycling compartments. Spastin required the ability to sever MTs and to interact with ESCRT-III (a complex controlling cargo degradation) proteins to regulate endosomal tubulation. Cells lacking IST1 (increased sodium tolerance 1), an endosomal sorting complex required for transport (ESCRT) component to which spastin binds, also had increased endosomal tubulation. Our results suggest that inclusion of IST1 into the ESCRT complex allows recruitment of spastin to promote fission of recycling tubules from the endosome. Thus, we reveal a novel cellular role for MT severing and identify a mechanism by which endosomal recycling can be coordinated with the degradative machinery. Spastin is mutated in the axonopathy hereditary spastic paraplegia. Zebrafish spinal motor axons depleted of spastin or IST1 also had abnormal endosomal tubulation, so we propose this phenotype is important for axonal degeneration.
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Affiliation(s)
- Rachel Allison
- Department of Medical Genetics, University of Cambridge, Cambridge CB2 0XY, England, UK
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Abstract
Early endosomal cargo is typically targeted to either a degradative or recycling pathway. Despite established functions for the retromer and ESCRT complexes at late endosomes/multivesicular bodies, the mechanisms integrating and coordinating these functions remain largely unknown. Rab family GTPases are key membrane trafficking organizers and could contribute. Here, in the unicellular organism Trypanosoma brucei, we demonstrate that Rab28 locates to the endosomal pathway and partially colocalizes with Vps23, an ESCRT I component. Rab28 is required for turnover of endocytosed proteins and for lysosomal delivery of protein cargo. Using RNA interference we find that in Rab28-depleted cells, protein levels of ESCRT I (Vps23/28) and retromer (Vps26) are also decreased, suggesting that Rab28 is an important regulator of these factors. We suggest that Rab28 coordinates the activity of retromer-dependent trafficking and ESCRT-mediated degradative pathways.
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Affiliation(s)
- Jennifer H Lumb
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK
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7
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Lumb JH, Connell JW, Allison R, Reid E. The AAA ATPase spastin links microtubule severing to membrane modelling. Biochim Biophys Acta 2011; 1823:192-7. [PMID: 21888932 DOI: 10.1016/j.bbamcr.2011.08.010] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2011] [Revised: 08/10/2011] [Accepted: 08/17/2011] [Indexed: 11/18/2022]
Abstract
In 1999, mutations in the gene encoding the microtubule severing AAA ATPase spastin were identified as a major cause of a genetic neurodegenerative condition termed hereditary spastic paraplegia (HSP). This finding stimulated intense study of the spastin protein and over the last decade, a combination of cell biological, in vivo, in vitro and structural studies have provided important mechanistic insights into the cellular functions of the protein, as well as elucidating cell biological pathways that might be involved in axonal maintenance and degeneration. Roles for spastin have emerged in shaping the endoplasmic reticulum and the abscission stage of cytokinesis, in which spastin appears to couple membrane modelling to microtubule regulation by severing.
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Affiliation(s)
- Jennifer H Lumb
- Department of Medical Genetics and Cambridge Institute for Medical Research, University of Cambridge, UK
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Abstract
BACKGROUND Rab small GTPases are important mediators of membrane transport, and orthologues frequently retain similar locations and functions, even between highly divergent taxa. In metazoan organisms Rab23 is an important negative regulator of Sonic hedgehog signaling and is crucial for correct development and differentiation of cellular lineages by virtue of an involvement in ciliary recycling. Previously, we reported that Trypanosoma brucei Rab23 localized to the nuclear envelope 1, which is clearly inconsistent with the mammalian location and function. As T. brucei is unicellular the potential that Rab23 has no role in cell signaling was possible. Here we sought to further investigate the role(s) of Rab23 in T. brucei to determine if Rab23 was an example of a Rab protein with divergent function in distinct taxa. METHODS/MAJOR FINDINGS The taxonomic distribution of Rab23 was examined and compared with the presence of flagella/cilia in representative taxa. Despite evidence for considerable secondary loss, we found a clear correlation between a conventional flagellar structure and the presence of a Rab23 orthologue in the genome. By epitope-tagging, Rab23 was localized and found to be present at the flagellum throughout the cell cycle. However, RNAi knockdown did not result in a flagellar defect, suggesting that Rab23 is not required for construction or maintenance of the flagellum. CONCLUSIONS The location of Rab23 at the flagellum is conserved between mammals and trypanosomes and the Rab23 gene is restricted to flagellated organisms. These data may suggest the presence of a Rab23-mediated signaling mechanism in trypanosomes.
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Affiliation(s)
- Jennifer H Lumb
- Cambridge Institute for Medical Research, MRC/Wellcome Trust building, Addenbrooke's Hospital, Hills Road, Cambridge, CB2 0XY, UK.
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Field MC, Lumb JH, Adung'a VO, Jones NG, Engstler M. Chapter 1 Macromolecular Trafficking and Immune Evasion in African Trypanosomes. International Review of Cell and Molecular Biology 2009; 278:1-67. [DOI: 10.1016/s1937-6448(09)78001-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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