1
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A multivesicular body-like organelle mediates stimulus-regulated trafficking of olfactory ciliary transduction proteins. Nat Commun 2022; 13:6889. [PMID: 36371422 PMCID: PMC9653401 DOI: 10.1038/s41467-022-34604-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Accepted: 10/28/2022] [Indexed: 11/13/2022] Open
Abstract
Stimulus transduction in cilia of olfactory sensory neurons is mediated by odorant receptors, Gαolf, adenylate cyclase-3, cyclic nucleotide-gated and chloride ion channels. Mechanisms regulating trafficking and localization of these proteins in the dendrite are unknown. By lectin/immunofluorescence staining and in vivo correlative light-electron microscopy (CLEM), we identify a retinitis pigmentosa-2 (RP2), ESCRT-0 and synaptophysin-containing multivesicular organelle that is not part of generic recycling/degradative/exosome pathways. The organelle's intraluminal vesicles contain the olfactory transduction proteins except for Golf subunits Gγ13 and Gβ1. Instead, Gβ1 colocalizes with RP2 on the organelle's outer membrane. The organelle accumulates in response to stimulus deprivation, while odor stimuli or adenylate cyclase activation cause outer membrane disintegration, release of intraluminal vesicles, and RP2/Gβ1 translocation to the base of olfactory cilia. Together, these findings reveal the existence of a dendritic organelle that mediates both stimulus-regulated storage of olfactory ciliary transduction proteins and membrane-delimited sorting important for G protein heterotrimerization.
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2
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Retinitis pigmentosa 2 pathogenic mutants degrade through BAG6/HUWE1 complex. Exp Eye Res 2022; 220:109110. [DOI: 10.1016/j.exer.2022.109110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 03/30/2022] [Accepted: 05/08/2022] [Indexed: 11/21/2022]
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3
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Abstract
Rods and cones are retinal photoreceptor neurons required for our visual sensation. Because of their highly polarized structures and well-characterized processes of G protein-coupled receptor-mediated phototransduction signaling, these photoreceptors have been excellent models for studying the compartmentalization and sorting of proteins. Rods and cones have a modified ciliary compartment called the outer segment (OS) as well as non-OS compartments. The distinct membrane protein compositions between OS and non-OS compartments suggest that the OS is separated from the rest of the cellular compartments by multiple barriers or gates that are selectively permissive to specific cargoes. This review discusses the mechanisms of protein sorting and compartmentalization in photoreceptor neurons. Proper sorting and compartmentalization of membrane proteins are required for signal transduction and transmission. This review also discusses the roles of compartmentalized signaling, which is compromised in various retinal ciliopathies.
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Affiliation(s)
- Yoshikazu Imanishi
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA;
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4
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Lessieur EM, Song P, Nivar GC, Piccillo EM, Fogerty J, Rozic R, Perkins BD. Ciliary genes arl13b, ahi1 and cc2d2a differentially modify expression of visual acuity phenotypes but do not enhance retinal degeneration due to mutation of cep290 in zebrafish. PLoS One 2019; 14:e0213960. [PMID: 30970040 PMCID: PMC6457629 DOI: 10.1371/journal.pone.0213960] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2019] [Accepted: 03/28/2019] [Indexed: 01/11/2023] Open
Abstract
Mutations in the gene Centrosomal Protein 290 kDa (CEP290) result in multiple ciliopathies ranging from the neonatal lethal disorder Meckel-Gruber Syndrome to multi-systemic disorders such as Joubert Syndrome and Bardet-Biedl Syndrome to nonsyndromic diseases like Leber Congenital Amaurosis (LCA) and retinitis pigmentosa. Results from model organisms and human genetics studies, have suggest that mutations in genes encoding protein components of the transition zone (TZ) and other cilia-associated proteins can function as genetic modifiers and be a source for CEP290 pleiotropy. We investigated the zebrafish cep290fh297/fh297 mutant, which encodes a nonsense mutation (p.Q1217*). This mutant is viable as adults, exhibits scoliosis, and undergoes a slow, progressive cone degeneration. The cep290fh297/fh297 mutants showed partial mislocalization of the transmembrane protein rhodopsin but not of the prenylated proteins rhodopsin kinase (GRK1) or the rod transducin subunit GNB1. Surprisingly, photoreceptor degeneration did not trigger proliferation of Müller glia, but proliferation of rod progenitors in the outer nuclear layer was significantly increased. To determine if heterozygous mutations in other cilia genes could exacerbate retinal degeneration, we bred cep290fh297/fh297 mutants to arl13b, ahi1, and cc2d2a mutant zebrafish lines. While cep290fh297/fh297 mutants lacking a single allele of these genes did not exhibit accelerated photoreceptor degeneration, loss of one alleles of arl13b or ahi1 reduced visual performance in optokinetic response assays at 5 days post fertilization. Our results indicate that the cep290fh297/fh297 mutant is a useful model to study the role of genetic modifiers on photoreceptor degeneration in zebrafish and to explore how progressive photoreceptor degeneration influences regeneration in adult zebrafish.
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Affiliation(s)
- Emma M. Lessieur
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
- Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Ping Song
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Gabrielle C. Nivar
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Ellen M. Piccillo
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Joseph Fogerty
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Richard Rozic
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Brian D. Perkins
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
- Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, Ohio, United States of America
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5
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Gharahkhani P, Burdon KP, Cooke Bailey JN, Hewitt AW, Law MH, Pasquale LR, Kang JH, Haines JL, Souzeau E, Zhou T, Siggs OM, Landers J, Awadalla M, Sharma S, Mills RA, Ridge B, Lynn D, Casson R, Graham SL, Goldberg I, White A, Healey PR, Grigg J, Lawlor M, Mitchell P, Ruddle J, Coote M, Walland M, Best S, Vincent A, Gale J, RadfordSmith G, Whiteman DC, Montgomery GW, Martin NG, Mackey DA, Wiggs JL, MacGregor S, Craig JE. Analysis combining correlated glaucoma traits identifies five new risk loci for open-angle glaucoma. Sci Rep 2018; 8:3124. [PMID: 29449654 PMCID: PMC5814451 DOI: 10.1038/s41598-018-20435-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Accepted: 01/18/2018] [Indexed: 01/08/2023] Open
Abstract
Open-angle glaucoma (OAG) is a major cause of blindness worldwide. To identify new risk loci for OAG, we performed a genome-wide association study in 3,071 OAG cases and 6,750 unscreened controls, and meta-analysed the results with GWAS data for intraocular pressure (IOP) and optic disc parameters (the overall meta-analysis sample size varying between 32,000 to 48,000 participants), which are glaucoma-related traits. We identified and independently validated four novel genome-wide significant associations within or near MYOF and CYP26A1, LINC02052 and CRYGS, LMX1B, and LMO7 using single variant tests, one additional locus (C9) using gene-based tests, and two genetic pathways - "response to fluid shear stress" and "abnormal retina morphology" - in pathway-based tests. Interestingly, some of the new risk loci contribute to risk of other genetically-correlated eye diseases including myopia and age-related macular degeneration. To our knowledge, this study is the first integrative study to combine genetic data from OAG and its correlated traits to identify new risk variants and genetic pathways, highlighting the future potential of combining genetic data from genetically-correlated eye traits for the purpose of gene discovery and mapping.
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Affiliation(s)
- Puya Gharahkhani
- QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia.
| | | | - Jessica N Cooke Bailey
- Population and Quantitative Health Sciences, Institute for Computational Biology, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | | | - Matthew H Law
- QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | - Louis R Pasquale
- Department of Ophthalmology, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, MA, USA.,Channing Division of Network Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Jae H Kang
- Channing Division of Network Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Jonathan L Haines
- Population and Quantitative Health Sciences, Institute for Computational Biology, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Emmanuelle Souzeau
- Department of Ophthalmology, Flinders University, Adelaide, South Australia, Australia
| | - Tiger Zhou
- Department of Ophthalmology, Flinders University, Adelaide, South Australia, Australia
| | - Owen M Siggs
- Department of Ophthalmology, Flinders University, Adelaide, South Australia, Australia
| | - John Landers
- Department of Ophthalmology, Flinders University, Adelaide, South Australia, Australia
| | - Mona Awadalla
- Department of Ophthalmology, Flinders University, Adelaide, South Australia, Australia
| | - Shiwani Sharma
- Department of Ophthalmology, Flinders University, Adelaide, South Australia, Australia
| | - Richard A Mills
- Department of Ophthalmology, Flinders University, Adelaide, South Australia, Australia
| | - Bronwyn Ridge
- Department of Ophthalmology, Flinders University, Adelaide, South Australia, Australia
| | - David Lynn
- South Australian Health & Medical Research Institute, School of Medicine, Flinders University, Adelaide, South Australia, Australia
| | - Robert Casson
- South Australian Institute of Ophthalmology, University of Adelaide, Adelaide, South Australia, Australia
| | - Stuart L Graham
- Ophthalmology and Vision Science, Macquarie University, Sydney, New South Wales, Australia
| | - Ivan Goldberg
- Department of Ophthalmology, University of Sydney, Sydney, Australia
| | - Andrew White
- Department of Ophthalmology, University of Sydney, Sydney, Australia.,Centre for Vision Research, The Westmead Institute for Medical Research, University of Sydney, Westmead, NSW, Australia
| | - Paul R Healey
- Department of Ophthalmology, University of Sydney, Sydney, Australia.,Centre for Vision Research, The Westmead Institute for Medical Research, University of Sydney, Westmead, NSW, Australia
| | - John Grigg
- Department of Ophthalmology, University of Sydney, Sydney, Australia
| | - Mitchell Lawlor
- Department of Ophthalmology, University of Sydney, Sydney, Australia
| | - Paul Mitchell
- Centre for Vision Research, The Westmead Institute for Medical Research, University of Sydney, Westmead, NSW, Australia
| | - Jonathan Ruddle
- Centre for Eye Research Australia (CERA), University of Melbourne, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia
| | - Michael Coote
- Centre for Eye Research Australia (CERA), University of Melbourne, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia
| | - Mark Walland
- Centre for Eye Research Australia (CERA), University of Melbourne, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia
| | - Stephen Best
- Department of Ophthalmology, University of Auckland, Auckland, New Zealand
| | - Andrea Vincent
- Department of Ophthalmology, University of Auckland, Auckland, New Zealand
| | - Jesse Gale
- Department of Ophthalmology, University of Otago, Dunedin, Otago, New Zealand
| | - Graham RadfordSmith
- QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia.,School of Medicine, University of Queensland, Herston Campus, Brisbane, QLD, Australia
| | - David C Whiteman
- QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | - Grant W Montgomery
- QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia.,Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia
| | - Nicholas G Martin
- QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | - David A Mackey
- University of Tasmania, Hobart, Tasmania, Australia.,Centre for Ophthalmology and Visual Science, Lions Eye Institute, University of Western Australia, Perth, Australia
| | - Janey L Wiggs
- Department of Ophthalmology, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, MA, USA
| | - Stuart MacGregor
- QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | - Jamie E Craig
- Department of Ophthalmology, Flinders University, Adelaide, South Australia, Australia.
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6
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Jean F, Pilgrim D. Coordinating the uncoordinated: UNC119 trafficking in cilia. Eur J Cell Biol 2017; 96:643-652. [PMID: 28935136 DOI: 10.1016/j.ejcb.2017.09.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Revised: 08/25/2017] [Accepted: 09/05/2017] [Indexed: 12/29/2022] Open
Abstract
Constructing the distinct subcellular environment of the cilium relies in a large part upon intraflagellar transport (IFT) proteins, which traffic cargo both to and within the cilium. However, evidence from the last 10 years suggests that IFT alone is not sufficient to generate the ciliary environment. One essential factor is UNC119, which interacts with known IFT molecular switches to transport ciliary cargos. Despite its apparent importance in ciliary trafficking though, human UNC119 mutations have only rarely been associated with diseases commonly linked with ciliopathies. This review will outline the trafficking pathways required for constructing the cilium by highlighting UNC119's role and the complexities involved in ciliary trafficking. Finally, despite important roles for UNC119 in cilia, UNC119 proteins also interact with non-ciliary proteins to affect other cellular processes.
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7
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Kurtenbach S, Gießl A, Strömberg S, Kremers J, Atorf J, Rasche S, Neuhaus EM, Hervé D, Brandstätter JH, Asan E, Hatt H, Kilimann MW. The BEACH Protein LRBA Promotes the Localization of the Heterotrimeric G-protein G olf to Olfactory Cilia. Sci Rep 2017; 7:8409. [PMID: 28814779 PMCID: PMC5559528 DOI: 10.1038/s41598-017-08543-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Accepted: 07/10/2017] [Indexed: 02/07/2023] Open
Abstract
BEACH domain proteins are involved in membrane protein traffic and human diseases, but their molecular mechanisms are not understood. The BEACH protein LRBA has been implicated in immune response and cell proliferation, and human LRBA mutations cause severe immune deficiency. Here, we report a first functional and molecular phenotype outside the immune system of LRBA-knockout mice: compromised olfaction, manifesting in reduced electro-olfactogram response amplitude, impaired food-finding efficiency, and smaller olfactory bulbs. LRBA is prominently expressed in olfactory and vomeronasal chemosensory neurons of wild-type mice. Olfactory impairment in the LRBA-KO is explained by markedly reduced concentrations (20–40% of wild-type levels) of all three subunits αolf, β1 and γ13 of the olfactory heterotrimeric G-protein, Golf, in the sensory cilia of olfactory neurons. In contrast, cilia morphology and the concentrations of many other proteins of olfactory cilia are not or only slightly affected. LRBA is also highly expressed in photoreceptor cells, another cell type with a specialized sensory cilium and heterotrimeric G-protein-based signalling; however, visual function appeared unimpaired by the LRBA-KO. To our knowledge, this is the first observation that a BEACH protein is required for the efficient subcellular localization of a lipid-anchored protein, and of a ciliary protein.
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Affiliation(s)
- Stefan Kurtenbach
- Department of Cell Physiology, Ruhr University Bochum, D-44780, Bochum, Germany
| | - Andreas Gießl
- Department of Biology, Animal Physiology, University of Erlangen-Nürnberg, D-91058, Erlangen, Germany
| | - Siv Strömberg
- Department of Neuroscience, Uppsala University, S-75124, Uppsala, Sweden
| | - Jan Kremers
- Department of Ophthalmology, University Hospital Erlangen, D-91054, Erlangen, Germany.,Department of Anatomy II, Friedrich-Alexander University Erlangen-Nürnberg, D-91054, Erlangen, Germany
| | - Jenny Atorf
- Department of Ophthalmology, University Hospital Erlangen, D-91054, Erlangen, Germany
| | - Sebastian Rasche
- Department of Cell Physiology, Ruhr University Bochum, D-44780, Bochum, Germany
| | - Eva M Neuhaus
- Department of Pharmacology and Toxikology, University Hospital Jena, D-07747, Jena, Germany
| | - Denis Hervé
- Inserm UMR-S839, Institut du Fer a Moulin, Universite Pierre et Marie Curie, F-75005, Paris, France
| | | | - Esther Asan
- Institute of Anatomy and Cell Biology, University of Würzburg, D-97070, Würzburg, Germany
| | - Hanns Hatt
- Department of Cell Physiology, Ruhr University Bochum, D-44780, Bochum, Germany
| | - Manfred W Kilimann
- Department of Neuroscience, Uppsala University, S-75124, Uppsala, Sweden. .,Department of Molecular Neurobiology, Max Planck Institute for Experimental Medicine, D-37075, Göttingen, Germany.
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8
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Liu F, Qin Y, Yu S, Soares DC, Yang L, Weng J, Li C, Gao M, Lu Z, Hu X, Liu X, Jiang T, Liu JY, Shu X, Tang Z, Liu M. Pathogenic mutations in retinitis pigmentosa 2 predominantly result in loss of RP2 protein stability in humans and zebrafish. J Biol Chem 2017; 292:6225-6239. [PMID: 28209709 PMCID: PMC5391753 DOI: 10.1074/jbc.m116.760314] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2016] [Revised: 02/14/2017] [Indexed: 12/20/2022] Open
Abstract
Mutations in retinitis pigmentosa 2 (RP2) account for 10-20% of X-linked retinitis pigmentosa (RP) cases. The encoded RP2 protein is implicated in ciliary trafficking of myristoylated and prenylated proteins in photoreceptor cells. To date >70 mutations in RP2 have been identified. How these mutations disrupt the function of RP2 is not fully understood. Here we report a novel in-frame 12-bp deletion (c.357_368del, p.Pro120_Gly123del) in zebrafish rp2 The mutant zebrafish shows reduced rod phototransduction proteins and progressive retinal degeneration. Interestingly, the protein level of mutant Rp2 is almost undetectable, whereas its mRNA level is near normal, indicating a possible post-translational effect of the mutation. Consistent with this hypothesis, the equivalent 12-bp deletion in human RP2 markedly impairs RP2 protein stability and reduces its protein level. Furthermore, we found that a majority of the RP2 pathogenic mutations (including missense, single-residue deletion, and C-terminal truncation mutations) severely destabilize the RP2 protein. The destabilized RP2 mutant proteins are degraded via the proteasome pathway, resulting in dramatically decreased protein levels. The remaining non-destabilizing mutations T87I, R118H/R118G/R118L/R118C, E138G, and R211H/R211L are suggested to impair the interaction between RP2 and its protein partners (such as ARL3) or with as yet unknown partners. By utilizing a combination of in silico, in vitro, and in vivo approaches, our work comprehensively indicates that loss of RP2 protein structural stability is the predominating pathogenic consequence for most RP2 mutations. Our study also reveals a role of the C-terminal domain of RP2 in maintaining the overall protein stability.
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Affiliation(s)
- Fei Liu
- From the Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - Yayun Qin
- From the Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - Shanshan Yu
- From the Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - Dinesh C Soares
- MRC Human Genetics Unit/Centre for Genomic and Experimental Medicine, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, United Kingdom, and
| | - Lifang Yang
- From the Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - Jun Weng
- From the Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - Chang Li
- From the Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - Meng Gao
- From the Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - Zhaojing Lu
- From the Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - Xuebin Hu
- From the Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - Xiliang Liu
- From the Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - Tao Jiang
- From the Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - Jing Yu Liu
- From the Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - Xinhua Shu
- Department of Life Sciences, Glasgow Caledonian University, Glasgow G4 0BA, United Kingdom
| | - Zhaohui Tang
- From the Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
| | - Mugen Liu
- From the Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China,
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9
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Parfitt DA, Lane A, Ramsden C, Jovanovic K, Coffey PJ, Hardcastle AJ, Cheetham ME. Using induced pluripotent stem cells to understand retinal ciliopathy disease mechanisms and develop therapies. Biochem Soc Trans 2016; 44:1245-1251. [PMID: 27911706 PMCID: PMC5238943 DOI: 10.1042/bst20160156] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Revised: 07/15/2016] [Accepted: 07/19/2016] [Indexed: 12/23/2022]
Abstract
The photoreceptor cells in the retina have a highly specialised sensory cilium, the outer segment (OS), which is important for detecting light. Mutations in cilia-related genes often result in retinal degeneration. The ability to reprogramme human cells into induced pluripotent stem cells and then differentiate them into a wide range of different cell types has revolutionised our ability to study human disease. To date, however, the challenge of producing fully differentiated photoreceptors in vitro has limited the application of this technology in studying retinal degeneration. In this review, we will discuss recent advances in stem cell technology and photoreceptor differentiation. In particular, the development of photoreceptors with rudimentary OS that can be used to understand disease mechanisms and as an important model to test potential new therapies for inherited retinal ciliopathies.
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Affiliation(s)
- David A. Parfitt
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, EC1V 9EL UK
| | - Amelia Lane
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, EC1V 9EL UK
| | - Conor Ramsden
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, EC1V 9EL UK
| | | | - Peter J. Coffey
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, EC1V 9EL UK
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10
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Gotthardt K, Lokaj M, Koerner C, Falk N, Gießl A, Wittinghofer A. A G-protein activation cascade from Arl13B to Arl3 and implications for ciliary targeting of lipidated proteins. eLife 2015; 4. [PMID: 26551564 PMCID: PMC4868535 DOI: 10.7554/elife.11859] [Citation(s) in RCA: 109] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Accepted: 11/06/2015] [Indexed: 12/11/2022] Open
Abstract
Small G-proteins of the ADP-ribosylation-factor-like (Arl) subfamily have been shown to be crucial to ciliogenesis and cilia maintenance. Active Arl3 is involved in targeting and releasing lipidated cargo proteins from their carriers PDE6δ and UNC119a/b to the cilium. However, the guanine nucleotide exchange factor (GEF) which activates Arl3 is unknown. Here we show that the ciliary G-protein Arl13B mutated in Joubert syndrome is the GEF for Arl3, and its function is conserved in evolution. The GEF activity of Arl13B is mediated by the G-domain plus an additional C-terminal helix. The switch regions of Arl13B are involved in the interaction with Arl3. Overexpression of Arl13B in mammalian cell lines leads to an increased Arl3·GTP level, whereas Arl13B Joubert-Syndrome patient mutations impair GEF activity and thus Arl3 activation. We anticipate that through Arl13B's exclusive ciliary localization, Arl3 activation is spatially restricted and thereby an Arl3·GTP compartment generated where ciliary cargo is specifically released.
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Affiliation(s)
- Katja Gotthardt
- Structural Biology Group, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Mandy Lokaj
- Structural Biology Group, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Carolin Koerner
- Structural Biology Group, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Nathalie Falk
- Department of Biology, Animal Physiology, University of Erlangen-Nuremberg, Erlangen, Germany
| | - Andreas Gießl
- Department of Biology, Animal Physiology, University of Erlangen-Nuremberg, Erlangen, Germany
| | - Alfred Wittinghofer
- Structural Biology Group, Max Planck Institute of Molecular Physiology, Dortmund, Germany
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11
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Lokaj M, Kösling SK, Koerner C, Lange SM, van Beersum SEC, van Reeuwijk J, Roepman R, Horn N, Ueffing M, Boldt K, Wittinghofer A. The Interaction of CCDC104/BARTL1 with Arl3 and Implications for Ciliary Function. Structure 2015; 23:2122-32. [PMID: 26455799 PMCID: PMC4635315 DOI: 10.1016/j.str.2015.08.016] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Revised: 08/26/2015] [Accepted: 08/29/2015] [Indexed: 01/23/2023]
Abstract
Cilia are small antenna-like cellular protrusions critical for many developmental signaling pathways. The ciliary protein Arl3 has been shown to act as a specific release factor for myristoylated and farnesylated ciliary cargo molecules by binding to the effectors Unc119 and PDE6δ. Here we describe a newly identified Arl3 binding partner, CCDC104/CFAP36. Biochemical and structural analyses reveal that the protein contains a BART-like domain and is called BARTL1. It recognizes an LLxILxxL motif at the N-terminal amphipathic helix of Arl3, which is crucial for the interaction with the BART-like domain but also for the ciliary localization of Arl3 itself. These results seem to suggest a ciliary role of BARTL1, and possibly link it to the Arl3 transport network. We thus speculate on a regulatory mechanism whereby BARTL1 aids the presentation of active Arl3 to its GTPase-activating protein RP2 or hinders Arl3 membrane binding in the area of the transition zone.
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Affiliation(s)
- Mandy Lokaj
- Max-Planck-Institute of Molecular Physiology, Emeritus Group, Otto-Hahn-Straße 15, 44227 Dortmund, Germany
| | - Stefanie K Kösling
- Max-Planck-Institute of Molecular Physiology, Emeritus Group, Otto-Hahn-Straße 15, 44227 Dortmund, Germany
| | - Carolin Koerner
- Max-Planck-Institute of Molecular Physiology, Emeritus Group, Otto-Hahn-Straße 15, 44227 Dortmund, Germany
| | - Sven M Lange
- Max-Planck-Institute of Molecular Physiology, Emeritus Group, Otto-Hahn-Straße 15, 44227 Dortmund, Germany
| | - Sylvia E C van Beersum
- Department of Human Genetics and Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Geert Grooteplein Zuid 10, 6525 GA Nijmegen, the Netherlands
| | - Jeroen van Reeuwijk
- Department of Human Genetics and Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Geert Grooteplein Zuid 10, 6525 GA Nijmegen, the Netherlands
| | - Ronald Roepman
- Department of Human Genetics and Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Geert Grooteplein Zuid 10, 6525 GA Nijmegen, the Netherlands
| | - Nicola Horn
- Medical Proteome Center, Institute for Ophthalmic Research, University of Tübingen, Nägelestrasse 5, 72074 Tübingen, Germany
| | - Marius Ueffing
- Medical Proteome Center, Institute for Ophthalmic Research, University of Tübingen, Nägelestrasse 5, 72074 Tübingen, Germany
| | - Karsten Boldt
- Medical Proteome Center, Institute for Ophthalmic Research, University of Tübingen, Nägelestrasse 5, 72074 Tübingen, Germany
| | - Alfred Wittinghofer
- Max-Planck-Institute of Molecular Physiology, Emeritus Group, Otto-Hahn-Straße 15, 44227 Dortmund, Germany.
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12
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Li L, Rao KN, Zheng-Le Y, Hurd TW, Lillo C, Khanna H. Loss of retinitis pigmentosa 2 (RP2) protein affects cone photoreceptor sensory cilium elongation in mice. Cytoskeleton (Hoboken) 2015; 72:447-54. [PMID: 26383048 DOI: 10.1002/cm.21255] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Revised: 09/11/2015] [Accepted: 09/15/2015] [Indexed: 02/03/2023]
Abstract
Degeneration of photoreceptors (rods and cones) results in blindness. As we rely almost entirely on our daytime vision mediated by the cones, it is the loss of these photoreceptors that results in legal blindness and poor quality of life. Cone dysfunction is usually observed due to two mechanisms: noncell-autonomous due to the secondary effect of rod death if the causative gene is specifically expressed in rods and cell autonomous, if the mutation is in a cone-specific gene. However, it is difficult to dissect cone autonomous effect of mutations in the genes that are expressed in both rods and cones. Here we report a property of murine cone photoreceptors, which is a cone-autonomous effect of the genetic perturbation of the retinitis pigmentosa 2 (Rp2) gene mutated in human X-linked RP. Constitutive loss of Rp2 results in abnormal extension of the cone outer segment (COS). This effect is phenocopied when the Rp2 gene is ablated specifically in cones but not when ablated in rods. Furthermore, the elongated COS exhibits abnormal ultrastructure with disorganized lamellae. Additionally, elongation of both the outer segment membrane and the microtubule cytoskeleton was observed in the absence of RP2. Taken together, our studies identify a cone morphological defect in retinal degeneration due to ablation of RP2 and will assist in understanding cone-autonomous responses during disease and develop targeted therapies.
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Affiliation(s)
- Linjing Li
- Department of Ophthalmology, University of Massachusetts Medical School, Worcester, Massachusetts
| | - Kollu Nageswara Rao
- Department of Ophthalmology, University of Massachusetts Medical School, Worcester, Massachusetts
| | - Yun Zheng-Le
- Department of Medicine, University of Oklahoma Health Science Center, Oklahoma City, Oklahoma
| | | | - Concepción Lillo
- Institute of Neurosciences of Castilla Y León-INCyL, Institute of Biomedical Research of Salamanca-IBSAL, Cell Biology and Pathology, University of Salamanca, Salamanca, Spain
| | - Hemant Khanna
- Department of Ophthalmology, University of Massachusetts Medical School, Worcester, Massachusetts
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13
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Desvignes T, Nguyen T, Chesnel F, Bouleau A, Fauvel C, Bobe J. X-Linked Retinitis Pigmentosa 2 Is a Novel Maternal-Effect Gene Required for Left-Right Asymmetry in Zebrafish. Biol Reprod 2015; 93:42. [PMID: 26134862 DOI: 10.1095/biolreprod.115.130575] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2015] [Accepted: 06/10/2015] [Indexed: 01/05/2023] Open
Abstract
Retinitis pigmentosa 2 (RP2) gene is responsible for up to 20% of X-linked retinitis pigmentosa, a severe heterogeneous genetic disorder resulting in progressive retinal degeneration in humans. In vertebrates, several bodies of evidence have clearly established the role of Rp2 protein in cilia genesis and/or function. Unexpectedly, some observations in zebrafish have suggested the oocyte-predominant expression of the rp2 gene, a typical feature of maternal-effect genes. In the present study, we investigate the maternal inheritance of rp2 gene products in zebrafish eggs in order to address whether rp2 could be a novel maternal-effect gene required for normal development. Although both rp2 mRNA and corresponding protein are expressed during oogenesis, rp2 mRNA is maternally inherited, in contrast to Rp2 protein. A knockdown of the protein transcribed from both rp2 maternal and zygotic mRNA results in delayed epiboly and severe developmental defects, including eye malformations, that were not observed when only the protein from zygotic origin was knocked down. Moreover, the knockdown of maternal and zygotic Rp2 revealed a high incidence of left-right asymmetry establishment defects compared to only zygotic knockdown. Here we show that rp2 is a novel maternal-effect gene exclusively expressed in oocytes within the zebrafish ovary and demonstrate that maternal rp2 mRNA is essential for successful embryonic development and thus contributes to egg developmental competence. Our observations also reveal that Rp2 protein translated from maternal mRNA is important to allow normal heart loop formation, thus providing evidence of a direct maternal contribution to left-right asymmetry establishment.
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Affiliation(s)
- Thomas Desvignes
- INRA, UR1037 Fish Physiology and Genomics, Campus de Beaulieu, Rennes, France IFREMER, LALR, Palavas Les Flots, France
| | - Thaovi Nguyen
- INRA, UR1037 Fish Physiology and Genomics, Campus de Beaulieu, Rennes, France
| | | | - Aurélien Bouleau
- INRA, UR1037 Fish Physiology and Genomics, Campus de Beaulieu, Rennes, France IFREMER, LALR, Palavas Les Flots, France
| | | | - Julien Bobe
- INRA, UR1037 Fish Physiology and Genomics, Campus de Beaulieu, Rennes, France
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14
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Liu F, Chen J, Yu S, Raghupathy RK, Liu X, Qin Y, Li C, Huang M, Liao S, Wang J, Zou J, Shu X, Tang Z, Liu M. Knockout of RP2 decreases GRK1 and rod transducin subunits and leads to photoreceptor degeneration in zebrafish. Hum Mol Genet 2015; 24:4648-59. [PMID: 26034134 DOI: 10.1093/hmg/ddv197] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Accepted: 05/26/2015] [Indexed: 12/14/2022] Open
Abstract
Retinitis pigmentosa (RP) affects about 1.8 million individuals worldwide. X-linked retinitis pigmentosa (XLRP) is one of the most severe forms of RP. Nearly 85% of XLRP cases are caused by mutations in the X-linked retinitis pigmentosa 2 (RP2) and RPGR. RP2 has been considered to be a GTPase activator protein for ARL3 and to play a role in the traffic of ciliary proteins. The mechanism of how RP2 mutations cause RP is still unclear. In this study, we generated an RP2 knockout zebrafish line using transcription activator-like effector nuclease technology. Progressive retinal degeneration could be observed in the mutant zebrafish. The degeneration of rods' outer segments (OSs) is predominant, followed by the degeneration of cones' OS. These phenotypes are similar to the characteristics of RP2 patients, and also partly consistent with the phenotypes of RP2 knockout mice and morpholino-mediated RP2 knockdown zebrafish. For the first time, we found RP2 deletion leads to decreased protein levels and abnormal retinal localizations of GRK1 and rod transducin subunits (GNAT1 and GNB1) in zebrafish. Furthermore, the distribution of the total farnesylated proteins in zebrafish retina is also affected by RP2 ablation. These molecular alterations observed in the RP2 knockout zebrafish might probably be responsible for the gradual loss of the photoreceptors' OSs. Our work identified the progression of retinal degeneration in RP2 knockout zebrafish, provided a foundation for revealing the pathogenesis of RP caused by RP2 mutations, and would help to develop potential therapeutics against RP in further studies.
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Affiliation(s)
- Fei Liu
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei 430074, PR China
| | - Jiaxiang Chen
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei 430074, PR China
| | - Shanshan Yu
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei 430074, PR China
| | | | - Xiliang Liu
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei 430074, PR China
| | - Yayun Qin
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei 430074, PR China
| | - Chang Li
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei 430074, PR China
| | - Mi Huang
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei 430074, PR China
| | - Shengjie Liao
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei 430074, PR China
| | - Jiuxiang Wang
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei 430074, PR China
| | - Jian Zou
- Institute of Translational Medicine, Zhejiang University, 268 Kaixuan Road, Zhongxin Beilou, Hangzhou, 310029 Zhejiang, PR China
| | - Xinhua Shu
- Department of Life Sciences, Glasgow Caledonian University, Glasgow G4 0BA, UK and and
| | - Zhaohui Tang
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei 430074, PR China,
| | - Mugen Liu
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei 430074, PR China,
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15
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Schwarz N, Carr AJ, Lane A, Moeller F, Chen LL, Aguilà M, Nommiste B, Muthiah MN, Kanuga N, Wolfrum U, Nagel-Wolfrum K, da Cruz L, Coffey PJ, Cheetham ME, Hardcastle AJ. Translational read-through of the RP2 Arg120stop mutation in patient iPSC-derived retinal pigment epithelium cells. Hum Mol Genet 2015; 24:972-86. [PMID: 25292197 PMCID: PMC4986549 DOI: 10.1093/hmg/ddu509] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Accepted: 09/29/2014] [Indexed: 01/08/2023] Open
Abstract
Mutations in the RP2 gene lead to a severe form of X-linked retinitis pigmentosa. RP2 patients frequently present with nonsense mutations and no treatments are currently available to restore RP2 function. In this study, we reprogrammed fibroblasts from an RP2 patient carrying the nonsense mutation c.519C>T (p.R120X) into induced pluripotent stem cells (iPSC), and differentiated these cells into retinal pigment epithelial cells (RPE) to study the mechanisms of disease and test potential therapies. RP2 protein was undetectable in the RP2 R120X patient cells, suggesting a disease mechanism caused by complete lack of RP2 protein. The RP2 patient fibroblasts and iPSC-derived RPE cells showed phenotypic defects in IFT20 localization, Golgi cohesion and Gβ1 trafficking. These phenotypes were corrected by over-expressing GFP-tagged RP2. Using the translational read-through inducing drugs (TRIDs) G418 and PTC124 (Ataluren), we were able to restore up to 20% of endogenous, full-length RP2 protein in R120X cells. This level of restored RP2 was sufficient to reverse the cellular phenotypic defects observed in both the R120X patient fibroblasts and iPSC-RPE cells. This is the first proof-of-concept study to demonstrate successful read-through and restoration of RP2 function for the R120X nonsense mutation. The ability of the restored RP2 protein level to reverse the observed cellular phenotypes in cells lacking RP2 indicates that translational read-through could be clinically beneficial for patients.
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Affiliation(s)
- Nele Schwarz
- UCL Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, UK
| | - Amanda-Jayne Carr
- UCL Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, UK
| | - Amelia Lane
- UCL Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, UK
| | - Fabian Moeller
- Johannes Gutenberg-University Muellerweg 6, 55099 Mainz, Germany and
| | - Li Li Chen
- UCL Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, UK
| | - Mònica Aguilà
- UCL Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, UK
| | - Britta Nommiste
- UCL Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, UK
| | - Manickam N Muthiah
- UCL Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, UK, Moorfields Eye Hospital, 162 City Road, London EC1V 2PD, UK
| | - Naheed Kanuga
- UCL Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, UK
| | - Uwe Wolfrum
- Johannes Gutenberg-University Muellerweg 6, 55099 Mainz, Germany and
| | | | - Lyndon da Cruz
- UCL Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, UK, Moorfields Eye Hospital, 162 City Road, London EC1V 2PD, UK
| | - Peter J Coffey
- UCL Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, UK
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16
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Baehr W. Membrane protein transport in photoreceptors: the function of PDEδ: the Proctor lecture. Invest Ophthalmol Vis Sci 2014; 55:8653-66. [PMID: 25550383 DOI: 10.1167/iovs.14-16066] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
This lecture details the elucidation of cGMP phosphodiesterase (PDEδ), discovered 25 years ago by Joe Beavo at the University of Washington. PDEδ, once identified as a fourth PDE6 subunit, is now regarded as a promiscuous prenyl-binding protein and important chaperone of prenylated small G proteins of the Ras superfamily and prenylated proteins of phototransduction. Alfred Wittinghofer's group in Germany showed that PDEδ forms an immunoglobulin-like β-sandwich fold that is closely related in structure to other lipid-binding proteins, for example, Uncoordinated 119 (UNC119) and RhoGDI. His group cocrystallized PDEδ with ARL (Arf-like) 2(GTP), and later with farnesylated Rheb (ras homolog expressed in brain). PDEδ specifically accommodates farnesyl and geranylgeranyl moieties in the absence of bound protein. Germline deletion of the Pde6d gene encoding PDEδ impeded transport of rhodopsin kinase (GRK1) and PDE6 to outer segments, causing slowly progressing, recessive retinitis pigmentosa. A rare PDE6D null allele in human patients, discovered by Tania Attié-Bitach in France, specifically impeded trafficking of farnesylated phosphatidylinositol 3,4,5-trisphosphate (PIP3) 5-phosphatase (INPP5E) to cilia, causing severe syndromic ciliopathy (Joubert syndrome). Binding of cargo to PDEδ is controlled by Arf-like proteins, ARL2 and ARL3, charged with guanosine-5'-triphosphate (GTP). Arf-like proteins 2 and 3 are unprenylated small GTPases that serve as cargo displacement factors. The lifetime of ARL3(GTP) is controlled by its GTPase-activating protein, retinitis pigmentosa protein 2 (RP2), which accelerates GTPase activity up to 90,000-fold. RP2 null alleles in human patients are associated with severe X-linked retinitis pigmentosa (XLRP). Germline deletion of RP2 in mouse, however, causes only a mild form of XLRP. Absence of RP2 prolongs the activity of ARL3(GTP) that, in turn, impedes PDE6δ-cargo interactions and trafficking of prenylated protein to the outer segments. Hyperactive ARL3(GTP), acting as a hyperactive cargo displacement factor, is predicted to be key in the pathobiology of RP2-XLRP.
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Affiliation(s)
- Wolfgang Baehr
- Department of Ophthalmology, John A. Moran Eye Center, University of Utah Health Science Center, University of Utah, Salt Lake City, Utah, United StatesDepartment of Neurobiology and Anatomy, University of Utah Health Science Center, University of Utah, Salt Lake City, Utah, United StatesDepartment of Biology, University of Utah, Salt Lake City, Utah, United States
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17
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Zhang H, Hanke-Gogokhia C, Jiang L, Li X, Wang P, Gerstner CD, Frederick JM, Yang Z, Baehr W. Mistrafficking of prenylated proteins causes retinitis pigmentosa 2. FASEB J 2014; 29:932-42. [PMID: 25422369 DOI: 10.1096/fj.14-257915] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The retinitis pigmentosa 2 polypeptide (RP2) functions as a GTPase-activating protein (GAP) for ARL3 (Arf-like protein 3), a small GTPase. ARL3 is an effector of phosphodiesterase 6 Δ (PDE6D), a prenyl-binding protein and chaperone of prenylated protein in photoreceptors. Mutations in the human RP2 gene cause X-linked retinitis pigmentosa (XLRP) and cone-rod dystrophy (XL-CORD). To study mechanisms causing XLRP, we generated an RP2 knockout mouse. The Rp2h(-/-) mice exhibited a slowly progressing rod-cone dystrophy simulating the human disease. Rp2h(-/-) scotopic a-wave and photopic b-wave amplitudes declined at 1 mo of age and continued to decline over the next 6 mo. Prenylated PDE6 subunits and G-protein coupled receptor kinase 1 (GRK1) were unable to traffic effectively to the Rp2h(-/-) outer segments. Mechanistically, absence of RP2 GAP activity increases ARL3-GTP levels, forcing PDE6D to assume a predominantly "closed" conformation that impedes binding of lipids. Lack of interaction disrupts trafficking of PDE6 and GRK1 to their destination, the photoreceptor outer segments. We propose that hyperactivity of ARL3-GTP in RP2 knockout mice and human patients with RP2 null alleles leads to XLRP resembling recessive rod-cone dystrophy.
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Affiliation(s)
- Houbin Zhang
- *The Sichuan Provincial Key Laboratory for Human Disease Gene Study, The Institute of Laboratory Medicine, Hospital of University of Electronic Science and Technology of China and Sichuan Provincial People's Hospital, Chengdu, Sichuan, China; School of Medicine, University of Electronic Science and Technology of China, Chengdu, Sichuan, China; Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, and Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah, USA; Department of Biochemistry and Biology, University of Potsdam, Potsdam-Golm, Germany; and Department of Biology, University of Utah, Salt Lake City, Utah, USA
| | - Christin Hanke-Gogokhia
- *The Sichuan Provincial Key Laboratory for Human Disease Gene Study, The Institute of Laboratory Medicine, Hospital of University of Electronic Science and Technology of China and Sichuan Provincial People's Hospital, Chengdu, Sichuan, China; School of Medicine, University of Electronic Science and Technology of China, Chengdu, Sichuan, China; Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, and Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah, USA; Department of Biochemistry and Biology, University of Potsdam, Potsdam-Golm, Germany; and Department of Biology, University of Utah, Salt Lake City, Utah, USA
| | - Li Jiang
- *The Sichuan Provincial Key Laboratory for Human Disease Gene Study, The Institute of Laboratory Medicine, Hospital of University of Electronic Science and Technology of China and Sichuan Provincial People's Hospital, Chengdu, Sichuan, China; School of Medicine, University of Electronic Science and Technology of China, Chengdu, Sichuan, China; Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, and Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah, USA; Department of Biochemistry and Biology, University of Potsdam, Potsdam-Golm, Germany; and Department of Biology, University of Utah, Salt Lake City, Utah, USA
| | - Xiaobo Li
- *The Sichuan Provincial Key Laboratory for Human Disease Gene Study, The Institute of Laboratory Medicine, Hospital of University of Electronic Science and Technology of China and Sichuan Provincial People's Hospital, Chengdu, Sichuan, China; School of Medicine, University of Electronic Science and Technology of China, Chengdu, Sichuan, China; Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, and Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah, USA; Department of Biochemistry and Biology, University of Potsdam, Potsdam-Golm, Germany; and Department of Biology, University of Utah, Salt Lake City, Utah, USA
| | - Pu Wang
- *The Sichuan Provincial Key Laboratory for Human Disease Gene Study, The Institute of Laboratory Medicine, Hospital of University of Electronic Science and Technology of China and Sichuan Provincial People's Hospital, Chengdu, Sichuan, China; School of Medicine, University of Electronic Science and Technology of China, Chengdu, Sichuan, China; Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, and Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah, USA; Department of Biochemistry and Biology, University of Potsdam, Potsdam-Golm, Germany; and Department of Biology, University of Utah, Salt Lake City, Utah, USA
| | - Cecilia D Gerstner
- *The Sichuan Provincial Key Laboratory for Human Disease Gene Study, The Institute of Laboratory Medicine, Hospital of University of Electronic Science and Technology of China and Sichuan Provincial People's Hospital, Chengdu, Sichuan, China; School of Medicine, University of Electronic Science and Technology of China, Chengdu, Sichuan, China; Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, and Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah, USA; Department of Biochemistry and Biology, University of Potsdam, Potsdam-Golm, Germany; and Department of Biology, University of Utah, Salt Lake City, Utah, USA
| | - Jeanne M Frederick
- *The Sichuan Provincial Key Laboratory for Human Disease Gene Study, The Institute of Laboratory Medicine, Hospital of University of Electronic Science and Technology of China and Sichuan Provincial People's Hospital, Chengdu, Sichuan, China; School of Medicine, University of Electronic Science and Technology of China, Chengdu, Sichuan, China; Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, and Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah, USA; Department of Biochemistry and Biology, University of Potsdam, Potsdam-Golm, Germany; and Department of Biology, University of Utah, Salt Lake City, Utah, USA
| | - Zhenglin Yang
- *The Sichuan Provincial Key Laboratory for Human Disease Gene Study, The Institute of Laboratory Medicine, Hospital of University of Electronic Science and Technology of China and Sichuan Provincial People's Hospital, Chengdu, Sichuan, China; School of Medicine, University of Electronic Science and Technology of China, Chengdu, Sichuan, China; Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, and Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah, USA; Department of Biochemistry and Biology, University of Potsdam, Potsdam-Golm, Germany; and Department of Biology, University of Utah, Salt Lake City, Utah, USA
| | - Wolfgang Baehr
- *The Sichuan Provincial Key Laboratory for Human Disease Gene Study, The Institute of Laboratory Medicine, Hospital of University of Electronic Science and Technology of China and Sichuan Provincial People's Hospital, Chengdu, Sichuan, China; School of Medicine, University of Electronic Science and Technology of China, Chengdu, Sichuan, China; Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, and Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah, USA; Department of Biochemistry and Biology, University of Potsdam, Potsdam-Golm, Germany; and Department of Biology, University of Utah, Salt Lake City, Utah, USA
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18
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Madhivanan K, Aguilar RC. Ciliopathies: the trafficking connection. Traffic 2014; 15:1031-56. [PMID: 25040720 DOI: 10.1111/tra.12195] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Revised: 06/28/2014] [Accepted: 07/08/2014] [Indexed: 12/15/2022]
Abstract
The primary cilium (PC) is a very dynamic hair-like membrane structure that assembles/disassembles in a cell-cycle-dependent manner and is present in almost every cell type. Despite being continuous with the plasma membrane, a diffusion barrier located at the ciliary base confers the PC properties of a separate organelle with very specific characteristics and membrane composition. Therefore, vesicle trafficking is the major process by which components are acquired for cilium formation and maintenance. In fact, a system of specific sorting signals controls the right of cargo admission into the cilia. Disruption to the ciliary structure or its function leads to multiorgan diseases known as ciliopathies. These illnesses arise from a spectrum of mutations in any of the more than 50 loci linked to these conditions. Therefore, it is not surprising that symptom variability (specific manifestations and severity) among and within ciliopathies appears to be an emerging characteristic. Nevertheless, one can speculate that mutations occurring in genes whose products contribute to the overall vesicle trafficking to the PC (i.e. affecting cilia assembly) will lead to more severe symptoms, whereas those involved in the transport of specific cargoes will result in milder phenotypes. In this review, we summarize the trafficking mechanisms to the cilia and also provide a description of the trafficking defects observed in some ciliopathies which can be correlated to the severity of the pathology.
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19
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Sung CH, Leroux MR. The roles of evolutionarily conserved functional modules in cilia-related trafficking. Nat Cell Biol 2014; 15:1387-97. [PMID: 24296415 DOI: 10.1038/ncb2888] [Citation(s) in RCA: 157] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Cilia are present across most eukaryotic phyla and have diverse sensory and motility roles in animal physiology, cell signalling and development. Their biogenesis and maintenance depend on vesicular and intraciliary (intraflagellar) trafficking pathways that share conserved structural and functional modules. The functional units of the interconnected pathways, which include proteins involved in membrane coating as well as small GTPases and their accessory factors, were first experimentally associated with canonical vesicular trafficking. These components are, however, ancient, having been co-opted by the ancestral eukaryote to establish the ciliary organelle, and their study can inform us about ciliary biology in higher organisms.
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Affiliation(s)
- Ching-Hwa Sung
- Margaret M. Dyson Vision Research Institute, Department of Ophthalmology, Weill Medical College of Cornell University, 1300 York Avenue, New York, New York 10065, USA
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20
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Bush A, Hogg C. Primary ciliary dyskinesia: recent advances in epidemiology, diagnosis, management and relationship with the expanding spectrum of ciliopathy. Expert Rev Respir Med 2014; 6:663-82. [DOI: 10.1586/ers.12.60] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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21
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Abstract
The ARF-like (ARL) proteins, within the ARF family, are a collection of functionally diverse GTPases that share extensive (>40 %) identity with the ARFs and each other and are assumed to share basic mechanisms of regulation and a very incompletely documented degree of overlapping regulators. At least four ARLs were already present in the last eukaryotic common ancestor, along with one ARF, and these have been expanded to >20 members in mammals. We know little about the majority of these proteins so our review will focus on those about which the most is known, including ARL1, ARL2, ARL3, ARL4s, ARL6, ARL13s, and ARFRP1. From this fragmentary information we extract some generalizations and conclusions regarding the sources and extent of specificity and functions of the ARLs.
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Affiliation(s)
- Alfred Wittinghofer
- Max-Planck-Institute of Molecular Physiology, Dortmund, Nordrhein-Westfalen Germany
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22
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Andre J, Kerry L, Qi X, Hawkins E, Drizyte K, Ginger ML, McKean PG. An alternative model for the role of RP2 protein in flagellum assembly in the African trypanosome. J Biol Chem 2013; 289:464-75. [PMID: 24257747 PMCID: PMC3879569 DOI: 10.1074/jbc.m113.509521] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The tubulin cofactor C domain-containing protein TbRP2 is a basal body (centriolar) protein essential for axoneme formation in the flagellate protist Trypanosoma brucei, the causal agent of African sleeping sickness. Here, we show how TbRP2 is targeted and tethered at mature basal bodies and provide novel insight into TbRP2 function. Regarding targeting, understanding how several hundred proteins combine to build a microtubule axoneme is a fundamental challenge in eukaryotic cell biology. We show that basal body localization of TbRP2 is mediated by twinned, N-terminal TOF (TON1, OFD1, and FOP) and LisH motifs, motifs that otherwise facilitate localization of only a few conserved proteins at microtubule-organizing centers in animals, plants, and flagellate protists. Regarding TbRP2 function, there is a debate as to whether the flagellar assembly function of specialized, centriolar tubulin cofactor C domain-containing proteins is processing tubulin, the major component of axonemes, or general vesicular trafficking in a flagellum assembly context. Here we report that TbRP2 is required for the recruitment of T. brucei orthologs of MKS1 and MKS6, proteins that, in animal cells, are part of a complex that assembles at the base of the flagellum to regulate protein composition and cilium function. We also identify that TbRP2 is detected by YL1/2, an antibody classically used to detect α-tubulin. Together, these data suggest a general processing role for TbRP2 in trypanosome flagellum assembly and challenge the notion that TbRP2 functions solely in assessing tubulin “quality” prior to tubulin incorporation into the elongating axoneme.
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Affiliation(s)
- Jane Andre
- From the Faculty of Health and Medicine, Biomedical and Life Sciences, Lancaster University, Lancaster LA1 4YQ, United Kingdom
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23
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Wang J, Deretic D. Molecular complexes that direct rhodopsin transport to primary cilia. Prog Retin Eye Res 2013; 38:1-19. [PMID: 24135424 DOI: 10.1016/j.preteyeres.2013.08.004] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Revised: 08/13/2013] [Accepted: 08/19/2013] [Indexed: 11/27/2022]
Abstract
Rhodopsin is a key molecular constituent of photoreceptor cells, yet understanding of how it regulates photoreceptor membrane trafficking and biogenesis of light-sensing organelles, the rod outer segments (ROS) is only beginning to emerge. Recently identified sequence of well-orchestrated molecular interactions of rhodopsin with the functional networks of Arf and Rab GTPases at multiple stages of intracellular targeting fits well into the complex framework of the biogenesis and maintenance of primary cilia, of which the ROS is one example. This review will discuss the latest progress in dissecting the molecular complexes that coordinate rhodopsin incorporation into ciliary-targeted carriers with the recruitment and activation of membrane tethering complexes and regulators of fusion with the periciliary plasma membrane. In addition to revealing the fundamental principals of ciliary membrane renewal, recent advances also provide molecular insight into the ways by which disruptions of the exquisitely orchestrated interactions lead to cilia dysfunction and result in human retinal dystrophies and syndromic diseases that affect multiple organs, including the eyes.
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Affiliation(s)
- Jing Wang
- Department of Surgery, Division of Ophthalmology, University of New Mexico, Albuquerque, NM 87131, USA
| | - Dusanka Deretic
- Department of Surgery, Division of Ophthalmology, University of New Mexico, Albuquerque, NM 87131, USA; Department of Cell Biology and Physiology, University of New Mexico, Albuquerque, NM 87131, USA.
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André J, Harrison S, Towers K, Qi X, Vaughan S, McKean PG, Ginger ML. The tubulin cofactor C family member TBCCD1 orchestrates cytoskeletal filament formation. J Cell Sci 2013; 126:5350-6. [PMID: 24101722 DOI: 10.1242/jcs.136515] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
TBCCD1 is an enigmatic member of the tubulin-binding cofactor C (TBCC) family of proteins required for mother-daughter centriole linkage in the green alga Chlamydomonas reinhardtii and nucleus-centrosome-Golgi linkage in mammalian cells. Loss of these linkages has severe morphogenetic consequences, but the mechanism(s) through which TBCCD1 contributes to cell organisation is unknown. In the African sleeping sickness parasite Trypanosoma brucei a microtubule-dominant cytoskeleton dictates cell shape, influencing strongly the positioning and inheritance patterns of key intracellular organelles. Here, we show the trypanosome orthologue of TBCCD1 is found at multiple locations: centrioles, the centriole-associated Golgi 'bi-lobe', and the anterior end of the cell body. Loss of Trypanosoma brucei TBCCD1 results in disorganisation of the structurally complex bi-lobe architecture and loss of centriole linkage to the single unit-copy mitochondrial genome (or kinetoplast) of the parasite. We therefore identify TBCCD1 as an essential protein associated with at least two filament-based structures in the trypanosome cytoskeleton. The last common ancestor of trypanosomes, animals and green algae was arguably the last common ancestor of all eukaryotes. On the basis of our observations, and interpretation of published data, we argue for an unexpected co-option of the TBCC domain for an essential non-tubulin-related function at an early point during evolution of the eukaryotic cytoskeleton.
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Affiliation(s)
- Jane André
- Faculty of Health and Medicine, Division of Biomedical and Life Sciences, Lancaster University, Lancaster LA1 4YQ, UK
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25
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Davidson AE, Schwarz N, Zelinger L, Stern-Schneider G, Shoemark A, Spitzbarth B, Gross M, Laxer U, Sosna J, Sergouniotis PI, Waseem NH, Wilson R, Kahn RA, Plagnol V, Wolfrum U, Banin E, Hardcastle AJ, Cheetham ME, Sharon D, Webster AR. Mutations in ARL2BP, encoding ADP-ribosylation-factor-like 2 binding protein, cause autosomal-recessive retinitis pigmentosa. Am J Hum Genet 2013; 93:321-9. [PMID: 23849777 DOI: 10.1016/j.ajhg.2013.06.003] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Revised: 05/03/2013] [Accepted: 06/04/2013] [Indexed: 01/01/2023] Open
Abstract
Retinitis pigmentosa (RP) is a genetically heterogeneous retinal degeneration characterized by photoreceptor death, which results in visual failure. Here, we used a combination of homozygosity mapping and exome sequencing to identify mutations in ARL2BP, which encodes an effector protein of the small GTPases ARL2 and ARL3, as causative for autosomal-recessive RP (RP66). In a family affected by RP and situs inversus, a homozygous, splice-acceptor mutation, c.101-1G>C, which alters pre-mRNA splicing of ARLBP2 in blood RNA, was identified. In another family, a homozygous c.134T>G (p.Met45Arg) mutation was identified. In the mouse retina, ARL2BP localized to the basal body and cilium-associated centriole of photoreceptors and the periciliary extension of the inner segment. Depletion of ARL2BP caused cilia shortening. Moreover, depletion of ARL2, but not ARL3, caused displacement of ARL2BP from the basal body, suggesting that ARL2 is vital for recruiting or anchoring ARL2BP at the base of the cilium. This hypothesis is supported by the finding that the p.Met45Arg amino acid substitution reduced binding to ARL2 and caused the loss of ARL2BP localization at the basal body in ciliated nasal epithelial cells. These data demonstrate a role for ARL2BP and ARL2 in primary cilia function and that this role is essential for normal photoreceptor maintenance and function.
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Li L, Khan N, Hurd T, Ghosh AK, Cheng C, Molday R, Heckenlively JR, Swaroop A, Khanna H. Ablation of the X-linked retinitis pigmentosa 2 (Rp2) gene in mice results in opsin mislocalization and photoreceptor degeneration. Invest Ophthalmol Vis Sci 2013; 54:4503-11. [PMID: 23745007 DOI: 10.1167/iovs.13-12140] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
PURPOSE Mutations in the RP2 gene are associated with 10% to 15% of X-linked retinitis pigmentosa (XLRP), a debilitating disorder characterized by the degeneration of retinal rod and cone photoreceptors. The molecular mechanism of pathogenesis of photoreceptor degeneration in XLRP-RP2 has not been elucidated, and no treatment is currently available. This study was undertaken to investigate the pathogenesis of RP2-associated retinal degeneration. METHODS We introduced loxP sites that flank exon 2, a mutational hotspot in XLRP-RP2, in the mouse Rp2 gene. We then produced Rp2-null allele using transgenic mice that expressed Cre-recombinase under control of the ubiquitous CAG promoter. Electroretinography (ERG), histology, light microscopy, transmission electron microscopy, and immunofluorescence microscopy were performed to ascertain the effect of ablation of Rp2 on photoreceptor development, function, and protein trafficking. RESULTS Although no gross abnormalities were detected in the Rp2(null) mice, photopic (cone) and scotopic (rod) function as measured by ERG showed a gradual decline starting as early as 1 month of age. We also detected slow progressive degeneration of the photoreceptor membrane discs in the mutant retina. These defects were associated with mislocalization of cone opsins to the nuclear and synaptic layers and reduced rhodopsin content in the outer segment of mutant retina prior to the onset of photoreceptor degeneration. CONCLUSIONS Our studies suggest that RP2 contributes to the maintenance of photoreceptor function and that cone opsin mislocalization represents an early step in XLRP caused by RP2 mutations. The Rp2(null) mice should serve as a useful preclinical model for testing gene- and cell-based therapies.
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Affiliation(s)
- Linjing Li
- Department of Ophthalmology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
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Whigham BT, Allingham RR. Developments in Ocular Genetics: Annual Review. ASIA-PACIFIC JOURNAL OF OPHTHALMOLOGY (PHILADELPHIA, PA.) 2013; 2:177-86. [PMID: 26108111 DOI: 10.1097/apo.0b013e318294b837] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE The purpose of this study was to summarize major developments in ocular genetics over the past year. DESIGN A literature review was performed for articles relating to the genetics of eye diseases and morphology. The search focused on articles published between September 15, 2011, and September 15, 2012. METHODS PubMed and Google Scholar search tools were used to search for ocular genetics articles in the desired date range. RESULTS Major advances have been reported in numerous areas including glaucoma, age-related macular degeneration, and keratoconus. Numerous novel associations have been identified through large genome-wide association studies. In addition, numerous disease genes have been identified through next-generation sequencing technologies. CONCLUSIONS Ocular genetics continues to advance at a rapid pace and benefit from new technologies. Numerous discoveries in the past year point toward areas for continued research.
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Affiliation(s)
- Benjamin T Whigham
- From the Department of Ophthalmology, Duke University Eye Center, Durham, NC
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28
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Raghupathy RK, McCulloch DL, Akhtar S, Al-mubrad TM, Shu X. Zebrafish model for the genetic basis of X-linked retinitis pigmentosa. Zebrafish 2013; 10:62-9. [PMID: 23536988 DOI: 10.1089/zeb.2012.0761] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Retinitis pigmentosa (RP) affects 1/4000 individuals in most populations, and X-linked RP (XLRP) is one of the most severe forms of human retinal degeneration. Mutations in both the retinitis pigmentosa GTPase regulator (RPGR) gene and retinitis pigmentosa 2 (RP2) gene account for almost all cases of XLRP. The functional roles of both RPGR and RP2 in the pathogenesis of XLRP are unclear. Due to the surprisingly high degree of functional conservation between human genes and their zebrafish orthologues, the zebrafish has become an important model for human retinal disorders. In this brief review, we summarize the functional characterization of XLRP-causing genes, RPGR and RP2, in zebrafish, and highlight recent studies that provide insight into the cellular functions of both genes. This will not only shed light on disease mechanisms in XLRP but will also provide a solid platform to test RP-causing mutants before proposing XLRP gene therapy trials.
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Schwarz N, Hardcastle AJ, Cheetham ME. Arl3 and RP2 mediated assembly and traffic of membrane associated cilia proteins. Vision Res 2012; 75:2-4. [PMID: 22884633 DOI: 10.1016/j.visres.2012.07.016] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2012] [Revised: 07/24/2012] [Accepted: 07/25/2012] [Indexed: 01/17/2023]
Abstract
The traffic of proteins to the outer segment of photoreceptors is a fundamentally important process, which when perturbed results in photoreceptor cell death. Recent reports have revealed a novel pathway for the traffic of lipid-modified proteins involving the small GTPase Arl3 and its effectors PDEδ and Unc119. The retinitis pigmentosa protein RP2 is a GTPase activating protein (GAP) for Arl3 and also appears to regulate the assembly and traffic of membrane associated protein complexes. We recently identified the Gβ subunit of transducin (Gβ1) as a novel RP2 interacting protein. Our data support a role for RP2 in facilitating membrane association and traffic of Gβ1, potentially prior to the formation of the obligate Gβ:Gγ heterodimer. Here, we review the recent evidence that suggests that RP2 co-operates with Arl3 and its effectors in protein complex assembly and membrane specification for lipid-modified proteins. This is exemplified by the co-ordination of cilia associated traffic for heterotrimeric G proteins and we propose a model for the role of Arl3 and RP2 in this process.
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Affiliation(s)
- Nele Schwarz
- UCL Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, UK
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