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Huang Y, Dong X, Sun SY, Lim TK, Lin Q, He CY. ARL3 GTPases facilitate ODA16 unloading from IFT in motile cilia. SCIENCE ADVANCES 2024; 10:eadq2950. [PMID: 39231220 PMCID: PMC11373600 DOI: 10.1126/sciadv.adq2950] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2024] [Accepted: 07/30/2024] [Indexed: 09/06/2024]
Abstract
Eukaryotic cilia and flagella are essential for cell motility and sensory functions. Their biogenesis and maintenance rely on the intraflagellar transport (IFT). Several cargo adapters have been identified to aid IFT cargo transport, but how ciliary cargos are discharged from the IFT remains largely unknown. During our explorations of small GTPases ARL13 and ARL3 in Trypanosoma brucei, we found that ODA16, a known IFT cargo adapter present exclusively in motile cilia, is a specific effector of ARL3. In the cilia, active ARL3 GTPases bind to ODA16 and dissociate ODA16 from the IFT complex. Depletion of ARL3 GTPases stabilizes ODA16 interaction with the IFT, leading to ODA16 accumulation in cilia and defects in axonemal assembly. The interactions between human ODA16 homolog HsDAW1 and ARL GTPases are conserved, and these interactions are altered in HsDAW1 disease variants. These findings revealed a conserved function of ARL GTPases in IFT transport of motile ciliary components, and a mechanism of cargo unloading from the IFT.
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Affiliation(s)
- Yameng Huang
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore
| | - Xiaoduo Dong
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore
| | - Stella Y Sun
- Department of Structural Biology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Teck-Kwang Lim
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore
| | - Qingsong Lin
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore
| | - Cynthia Y He
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore
- The Centre for BioImaging Sciences, National University of Singapore, Singapore, Singapore
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2
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Frederick CE, Zenisek D. Ribbon Synapses and Retinal Disease: Review. Int J Mol Sci 2023; 24:5090. [PMID: 36982165 PMCID: PMC10049380 DOI: 10.3390/ijms24065090] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Revised: 02/27/2023] [Accepted: 03/01/2023] [Indexed: 03/30/2023] Open
Abstract
Synaptic ribbons are presynaptic protein complexes that are believed to be important for the transmission of sensory information in the visual system. Ribbons are selectively associated with those synapses where graded changes in membrane potential drive continuous neurotransmitter release. Defective synaptic transmission can arise as a result of the mutagenesis of a single ribbon component. Visual diseases that stem from malfunctions in the presynaptic molecular machinery of ribbon synapses in the retina are rare. In this review, we provide an overview of synaptopathies that give rise to retinal malfunction and our present understanding of the mechanisms that underlie their pathogenesis and discuss muscular dystrophies that exhibit ribbon synapse involvement in the pathology.
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Affiliation(s)
| | - David Zenisek
- Department of Molecular and Cellular Physiology, Yale University School of Medicine, 333 Cedar Street, P.O. Box 208026, New Haven, CT 06510, USA
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3
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Functional compartmentalization of photoreceptor neurons. Pflugers Arch 2021; 473:1493-1516. [PMID: 33880652 DOI: 10.1007/s00424-021-02558-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 03/15/2021] [Accepted: 03/22/2021] [Indexed: 12/16/2022]
Abstract
Retinal photoreceptors are neurons that convert dynamically changing patterns of light into electrical signals that are processed by retinal interneurons and ultimately transmitted to vision centers in the brain. They represent the essential first step in seeing without which the remainder of the visual system is rendered moot. To support this role, the major functions of photoreceptors are segregated into three main specialized compartments-the outer segment, the inner segment, and the pre-synaptic terminal. This compartmentalization is crucial for photoreceptor function-disruption leads to devastating blinding diseases for which therapies remain elusive. In this review, we examine the current understanding of the molecular and physical mechanisms underlying photoreceptor functional compartmentalization and highlight areas where significant knowledge gaps remain.
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4
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Barnes CL, Malhotra H, Calvert PD. Compartmentalization of Photoreceptor Sensory Cilia. Front Cell Dev Biol 2021; 9:636737. [PMID: 33614665 PMCID: PMC7889997 DOI: 10.3389/fcell.2021.636737] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 01/07/2021] [Indexed: 12/12/2022] Open
Abstract
Functional compartmentalization of cells is a universal strategy for segregating processes that require specific components, undergo regulation by modulating concentrations of those components, or that would be detrimental to other processes. Primary cilia are hair-like organelles that project from the apical plasma membranes of epithelial cells where they serve as exclusive compartments for sensing physical and chemical signals in the environment. As such, molecules involved in signal transduction are enriched within cilia and regulating their ciliary concentrations allows adaptation to the environmental stimuli. The highly efficient organization of primary cilia has been co-opted by major sensory neurons, olfactory cells and the photoreceptor neurons that underlie vision. The mechanisms underlying compartmentalization of cilia are an area of intense current research. Recent findings have revealed similarities and differences in molecular mechanisms of ciliary protein enrichment and its regulation among primary cilia and sensory cilia. Here we discuss the physiological demands on photoreceptors that have driven their evolution into neurons that rely on a highly specialized cilium for signaling changes in light intensity. We explore what is known and what is not known about how that specialization appears to have driven unique mechanisms for photoreceptor protein and membrane compartmentalization.
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Affiliation(s)
| | | | - Peter D. Calvert
- Department of Ophthalmology and Visual Sciences, Center for Vision Research, SUNY Upstate Medical University, Syracuse, NY, United States
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5
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Shimizu T, Nakamura T, Inaba H, Iwasa H, Maruyama J, Arimoto-Matsuzaki K, Nakata T, Nishina H, Hata Y. The RAS-interacting chaperone UNC119 drives the RASSF6-MDM2-p53 axis and antagonizes RAS-mediated malignant transformation. J Biol Chem 2020; 295:11214-11230. [PMID: 32554467 DOI: 10.1074/jbc.ra120.012649] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 06/16/2020] [Indexed: 11/06/2022] Open
Abstract
The gene encoding the proto-oncogene GTPase RAS is frequently mutated in human cancers. Mutated RAS proteins trigger antiapoptotic and cell-proliferative signals and lead to oncogenesis. However, RAS also induces apoptosis and senescence, which may contribute to the eradication of cells with RAS mutations. We previously reported that Ras association domain family member 6 (RASSF6) binds MDM2 and stabilizes the tumor suppressor p53 and that the active form of KRAS promotes the interaction between RASSF6 and MDM2. We also reported that Unc-119 lipid-binding chaperone (UNC119A), a chaperone of myristoylated proteins, interacts with RASSF6 and regulates RASSF6-mediated apoptosis. In this study, using several human cancer cell lines, quantitative RT-PCR, RNAi-based gene silencing, and immunoprecipitation/-fluorescence and cell biology assays, we report that UNC119A interacts with the active form of KRAS and that the C-terminal modification of KRAS is required for this interaction. We also noted that the hydrophobic pocket of UNC119A, which binds the myristoylated peptides, is not involved in the interaction. We observed that UNC119A promotes the binding of KRAS to RASSF6, enhances the interaction between RASSF6 and MDM2, and induces apoptosis. Conversely, UNC119A silencing promoted soft-agar colony formation, migration, and invasiveness in KRAS-mutated cancer cells. We conclude that UNC119A promotes KRAS-mediated p53-dependent apoptosis via RASSF6 and may play a tumor-suppressive role in cells with KRAS mutations.
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Affiliation(s)
- Takanobu Shimizu
- Department of Medical Biochemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Takeshi Nakamura
- Department of Medical Biochemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Hironori Inaba
- Department of Cell Biology, Graduate School of Medical and Dental Science, Tokyo Medical and Dental University, Tokyo, Japan
| | - Hiroaki Iwasa
- Department of Medical Biochemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Junichi Maruyama
- Department of Medical Biochemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Kyoko Arimoto-Matsuzaki
- Department of Medical Biochemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Takao Nakata
- Department of Cell Biology, Graduate School of Medical and Dental Science, Tokyo Medical and Dental University, Tokyo, Japan.,Center for Brain Integration Research, Tokyo Medical and Dental University, Tokyo, Japan
| | - Hiroshi Nishina
- Department of Developmental and Regenerative Biology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Yutaka Hata
- Department of Medical Biochemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan .,Center for Brain Integration Research, Tokyo Medical and Dental University, Tokyo, Japan
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6
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He L, Kooistra R, Das R, Oudejans E, van Leen E, Ziegler J, Portegies S, de Haan B, van Regteren Altena A, Stucchi R, Altelaar AM, Wieser S, Krieg M, Hoogenraad CC, Harterink M. Cortical anchoring of the microtubule cytoskeleton is essential for neuron polarity. eLife 2020; 9:55111. [PMID: 32293562 PMCID: PMC7159925 DOI: 10.7554/elife.55111] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Accepted: 03/31/2020] [Indexed: 12/22/2022] Open
Abstract
The development of a polarized neuron relies on the selective transport of proteins to axons and dendrites. Although it is well known that the microtubule cytoskeleton has a central role in establishing neuronal polarity, how its specific organization is established and maintained is poorly understood. Using the in vivo model system Caenorhabditis elegans, we found that the highly conserved UNC-119 protein provides a link between the membrane-associated Ankyrin (UNC-44) and the microtubule-associated CRMP (UNC-33). Together they form a periodic membrane-associated complex that anchors axonal and dendritic microtubule bundles to the cortex. This anchoring is critical to maintain microtubule organization by opposing kinesin-1 powered microtubule sliding. Disturbing this molecular complex alters neuronal polarity and causes strong developmental defects of the nervous system leading to severely paralyzed animals.
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Affiliation(s)
- Liu He
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, Utrecht, Netherlands
| | - Robbelien Kooistra
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, Utrecht, Netherlands
| | - Ravi Das
- Neurophotonics and Mechanical Systems Biology, ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Ellen Oudejans
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, Utrecht, Netherlands
| | - Eric van Leen
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, Utrecht, Netherlands
| | - Johannes Ziegler
- Fast live-cell superresolution microscopy, ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Sybren Portegies
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, Utrecht, Netherlands
| | - Bart de Haan
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, Utrecht, Netherlands
| | - Anna van Regteren Altena
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, Utrecht, Netherlands
| | - Riccardo Stucchi
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, Utrecht, Netherlands.,Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, Netherlands
| | - Af Maarten Altelaar
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, Netherlands
| | - Stefan Wieser
- Fast live-cell superresolution microscopy, ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Michael Krieg
- Neurophotonics and Mechanical Systems Biology, ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Casper C Hoogenraad
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, Utrecht, Netherlands.,Department of Neuroscience, Genentech, Inc, South San Francisco, United States
| | - Martin Harterink
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, Utrecht, Netherlands
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7
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Cai XB, Wu KC, Zhang X, Lv JN, Jin GH, Xiang L, Chen J, Huang XF, Pan D, Lu B, Lu F, Qu J, Jin ZB. Whole-exome sequencing identified ARL2 as a novel candidate gene for MRCS (microcornea, rod-cone dystrophy, cataract, and posterior staphyloma) syndrome. Clin Genet 2019; 96:61-71. [PMID: 30945270 DOI: 10.1111/cge.13541] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Revised: 03/20/2019] [Accepted: 03/21/2019] [Indexed: 01/01/2023]
Abstract
Adenosine diphosphate (ADP)-ribosylation factor-like 2 (ARL2) protein participates in a broad range of cellular processes and acts as a mediator for mutant ARL2BP in cilium-associated retinitis pigmentosa and for mutant HRG4 in mitochondria-related photoreceptor degeneration. However, mutant ARL2 has not been linked to any human disease so far. Here, we identified a de novo variant in ARL2 (c.44G > T, p.R15L) in a Chinese pedigree with MRCS (microcornea, rod-cone dystrophy, cataract, and posterior staphyloma) syndrome through whole-exome sequencing and co-segregation analysis. Co-immunoprecipitation assay and immunoblotting confirmed that the mutant ARL2 protein showed a 62% lower binding affinity for HRG4 while a merely 18% lower binding affinity for ARL2BP. Immunofluorescence images of ARL2 and HRG4 co-localizing with cytochrome c in HeLa cells described their relationship with mitochondria. Further analyses of the mitochondrial respiratory chain and adenosine triphosphate production showed significant abnormalities under an ARL2-mutant condition. Finally, we generated transgenic mice to test the pathogenicity of this variant and observed retinal degeneration complicated with microcornea and cataract that were similar to those in our patients. In conclusion, we uncover ARL2 as a novel candidate gene for MRCS syndrome and suggest a mitochondria-related mechanism of the first ARL2 variant through site-directed mutagenesis studies.
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Affiliation(s)
- Xue-Bi Cai
- Lab for Stem Cell and Retinal Regeneration, Institute of Stem Cell Research; Division of Ophthalmic Genetics, The Eye Hospital, Wenzhou Medical University, Wenzhou, China.,State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou Medical University, Wenzhou, China
| | - Kun-Chao Wu
- Lab for Stem Cell and Retinal Regeneration, Institute of Stem Cell Research; Division of Ophthalmic Genetics, The Eye Hospital, Wenzhou Medical University, Wenzhou, China.,State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou Medical University, Wenzhou, China
| | - Xiao Zhang
- Lab for Stem Cell and Retinal Regeneration, Institute of Stem Cell Research; Division of Ophthalmic Genetics, The Eye Hospital, Wenzhou Medical University, Wenzhou, China.,State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou Medical University, Wenzhou, China
| | - Ji-Neng Lv
- Lab for Stem Cell and Retinal Regeneration, Institute of Stem Cell Research; Division of Ophthalmic Genetics, The Eye Hospital, Wenzhou Medical University, Wenzhou, China.,State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou Medical University, Wenzhou, China
| | - Guang-Hui Jin
- Lab for Stem Cell and Retinal Regeneration, Institute of Stem Cell Research; Division of Ophthalmic Genetics, The Eye Hospital, Wenzhou Medical University, Wenzhou, China.,State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou Medical University, Wenzhou, China
| | - Lue Xiang
- Lab for Stem Cell and Retinal Regeneration, Institute of Stem Cell Research; Division of Ophthalmic Genetics, The Eye Hospital, Wenzhou Medical University, Wenzhou, China.,State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou Medical University, Wenzhou, China
| | - Jie Chen
- State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou Medical University, Wenzhou, China
| | - Xiu-Feng Huang
- Lab for Stem Cell and Retinal Regeneration, Institute of Stem Cell Research; Division of Ophthalmic Genetics, The Eye Hospital, Wenzhou Medical University, Wenzhou, China.,State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou Medical University, Wenzhou, China
| | - Deng Pan
- Lab for Stem Cell and Retinal Regeneration, Institute of Stem Cell Research; Division of Ophthalmic Genetics, The Eye Hospital, Wenzhou Medical University, Wenzhou, China.,State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou Medical University, Wenzhou, China
| | - Bin Lu
- Protein Quality Control and Diseases Laboratory, Institute of Biophysics, School of Life Sciences, Wenzhou Medical University, Wenzhou, China
| | - Fan Lu
- State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou Medical University, Wenzhou, China
| | - Jia Qu
- State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou Medical University, Wenzhou, China
| | - Zi-Bing Jin
- Lab for Stem Cell and Retinal Regeneration, Institute of Stem Cell Research; Division of Ophthalmic Genetics, The Eye Hospital, Wenzhou Medical University, Wenzhou, China.,State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou Medical University, Wenzhou, China
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8
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Baehr W, Hanke-Gogokhia C, Sharif A, Reed M, Dahl T, Frederick JM, Ying G. Insights into photoreceptor ciliogenesis revealed by animal models. Prog Retin Eye Res 2018; 71:26-56. [PMID: 30590118 DOI: 10.1016/j.preteyeres.2018.12.004] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 12/10/2018] [Accepted: 12/18/2018] [Indexed: 12/11/2022]
Abstract
Photoreceptors are polarized neurons, with very specific subcellular compartmentalization and unique requirements for protein expression and trafficking. Each photoreceptor contains an outer segment, the site of photon capture that initiates vision, an inner segment that houses the biosynthetic machinery and a synaptic terminal for signal transmission to downstream neurons. Outer segments and inner segments are connected by a connecting cilium (CC), the equivalent of a transition zone (TZ) of primary cilia. The connecting cilium is part of the basal body/axoneme backbone that stabilizes the outer segment. This report will update the reader on late developments in photoreceptor ciliogenesis and transition zone formation, specifically in mouse photoreceptors, focusing on early events in photoreceptor ciliogenesis. The connecting cilium, an elongated and narrow structure through which all outer segment proteins and membrane components must traffic, functions as a gate that controls access to the outer segment. Here we will review genes and their protein products essential for basal body maturation and for CC/TZ genesis, sorted by phenotype. Emphasis is given to naturally occurring mouse mutants and gene knockouts that interfere with CC/TZ formation and ciliogenesis.
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Affiliation(s)
- Wolfgang Baehr
- Department of Ophthalmology and Visual Sciences, University of Utah Health Sciences, Salt Lake City, UT, 84132, USA.
| | - Christin Hanke-Gogokhia
- Department of Ophthalmology and Visual Sciences, University of Utah Health Sciences, Salt Lake City, UT, 84132, USA
| | - Ali Sharif
- Department of Ophthalmology and Visual Sciences, University of Utah Health Sciences, Salt Lake City, UT, 84132, USA
| | - Michelle Reed
- Department of Ophthalmology and Visual Sciences, University of Utah Health Sciences, Salt Lake City, UT, 84132, USA
| | - Tiffanie Dahl
- Department of Ophthalmology and Visual Sciences, University of Utah Health Sciences, Salt Lake City, UT, 84132, USA
| | - Jeanne M Frederick
- Department of Ophthalmology and Visual Sciences, University of Utah Health Sciences, Salt Lake City, UT, 84132, USA
| | - Guoxin Ying
- Department of Ophthalmology and Visual Sciences, University of Utah Health Sciences, Salt Lake City, UT, 84132, USA
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9
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Iwasa H, Sarkar A, Shimizu T, Sawada T, Hossain S, Xu X, Maruyama J, Arimoto-Matsuzaki K, Withanage K, Nakagawa K, Kurihara H, Kuroyanagi H, Hata Y. UNC119 is a binding partner of tumor suppressor Ras-association domain family 6 and induces apoptosis and cell cycle arrest by MDM2 and p53. Cancer Sci 2018; 109:2767-2780. [PMID: 29931788 PMCID: PMC6125449 DOI: 10.1111/cas.13706] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Accepted: 06/20/2018] [Indexed: 01/06/2023] Open
Abstract
Ras-association domain family 6 (RASSF6) is a tumor suppressor that interacts with MDM2 and stabilizes p53. Caenorhabditis elegans unc-119 encodes a protein that is required for normal development of the nervous system. Humans have 2 unc-119 homologues, UNC119 and UNC119B. We have identified UNC119 as a RASSF6-interacting protein. UNC119 promotes the interaction between RASSF6 and MDM2 and stabilizes p53. Thus, UNC119 induces apoptosis by RASSF6 and p53. UNC119 depletion impairs DNA repair after DNA damage and results in polyploid cell generation. These findings support that UNC119 is a regulator of the RASSF6-MDM2-p53 axis and functions as a tumor suppressor.
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Affiliation(s)
- Hiroaki Iwasa
- Department of Medical Biochemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Aradhan Sarkar
- Department of Medical Biochemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Takanobu Shimizu
- Department of Medical Biochemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Takeru Sawada
- Department of Medical Biochemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Shakhawoat Hossain
- Department of Medical Biochemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.,Department of Biochemistry and Molecular Biology, University of Rajshahi, Rajshahi, Bangladesh
| | - Xiaoyin Xu
- Department of Medical Biochemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.,China Department of Breast Surgery, The Second Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Junichi Maruyama
- Department of Medical Biochemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Kyoko Arimoto-Matsuzaki
- Department of Medical Biochemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Kanchanamala Withanage
- Department of Medical Biochemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Kentaro Nakagawa
- Department of Medical Biochemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Hidetake Kurihara
- Department of Physical Therapy, Faculty of Health Science, Aino University, Osaka, Japan
| | - Hidehito Kuroyanagi
- Laboratory of Gene Expression, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Yutaka Hata
- Department of Medical Biochemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.,Center for Brain Integration Research, Tokyo Medical and Dental University, Tokyo, Japan
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10
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Abstract
Proper regulation of the immune system is required for protection against pathogens and preventing autoimmune disorders. Inborn errors of the immune system due to inherited or de novo germline mutations can lead to the loss of protective immunity, aberrant immune homeostasis, and the development of autoimmune disease, or combinations of these. Forward genetic screens involving clinical material from patients with primary immunodeficiencies (PIDs) can vary in severity from life-threatening disease affecting multiple cell types and organs to relatively mild disease with susceptibility to a limited range of pathogens or mild autoimmune conditions. As central mediators of innate and adaptive immune responses, T cells are critical orchestrators and effectors of the immune response. As such, several PIDs result from loss of or altered T cell function. PID-associated functional defects range from complete absence of T cell development to uncontrolled effector cell activation. Furthermore, the gene products of known PID causal genes are involved in diverse molecular pathways ranging from T cell receptor signaling to regulators of protein glycosylation. Identification of the molecular and biochemical cause of PIDs can not only guide the course of treatment for patients, but also inform our understanding of the basic biology behind T cell function. In this chapter, we review PIDs with known genetic causes that intrinsically affect T cell function with particular focus on perturbations of biochemical pathways.
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Affiliation(s)
- William A Comrie
- Molecular Development of the Immune System Section, Laboratory of Immune System Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States; Clinical Genomics Program, National Institute of Allergy and Infectious Diseases (NIAID), NIH, Bethesda, MD, United States
| | - Michael J Lenardo
- Molecular Development of the Immune System Section, Laboratory of Immune System Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States; Clinical Genomics Program, National Institute of Allergy and Infectious Diseases (NIAID), NIH, Bethesda, MD, United States.
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11
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Ismail S. A GDI/GDF-like system for sorting and shuttling ciliary proteins. Small GTPases 2017; 8:208-211. [PMID: 27487321 PMCID: PMC5680679 DOI: 10.1080/21541248.2016.1213782] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Revised: 07/12/2016] [Accepted: 07/12/2016] [Indexed: 10/21/2022] Open
Abstract
Post/co-translational modifications by the addition of lipids take place in a vast number of proteins. Rab and Rho are small G proteins which are prenylated and targeted to membranes in complex with solubilizing factors called guanosine dissociation inhibitors (GDIs). The release of Rab and Rho at the correct destination from their cognate GDI has been proposed to be mediated through GDI displacement factors. However this mechanism is yet to be established and it has been shown that loading of Rab proteins with GTP at the destination can be sufficient for their correct targeting. PDE6D shares structural homology with Rho GDI and solubilises several prenylated proteins and mediate their targeting to different destinations including cilia. In a paper published by Fansa et al, the authors propose that sorting of cargo is dependent on the differential release by bona fide GDFs, Arl2 and Arl3, and the localization of the active Arl3GTP in cilia.
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12
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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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13
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Spatial cycles mediated by UNC119 solubilisation maintain Src family kinases plasma membrane localisation. Nat Commun 2017; 8:114. [PMID: 28740133 PMCID: PMC5524651 DOI: 10.1038/s41467-017-00116-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Accepted: 06/02/2017] [Indexed: 12/12/2022] Open
Abstract
The peripheral membrane proto-oncogene Src family protein tyrosine kinases relay growth factor signals to the cytoplasm of mammalian cells. We unravel the spatial cycles of solubilisation, trapping on perinuclear membrane compartments and vesicular transport that counter entropic equilibration to endomembranes for maintaining the enrichment and activity of Src family protein tyrosine kinases at the plasma membrane. The solubilising factor UNC119 sequesters myristoylated Src family protein tyrosine kinases from the cytoplasm, enhancing their diffusion to effectively release Src family protein tyrosine kinases on the recycling endosome by localised Arl2/3 activity. Src is then trapped on the recycling endosome via electrostatic interactions, whereas Fyn is quickly released to be kinetically trapped on the Golgi by palmitoyl acyl-transferase activity. Vesicular trafficking from these compartments restores enrichment of the Src family protein tyrosine kinases to the plasma membrane. Interference with these spatial cycles by UNC119 knockdown disrupts Src family protein tyrosine kinase localisation and signalling activity, indicating that UNC119 could be a drug target to affect oncogenic Src family protein tyrosine kinase signalling. The peripheral membrane proto-oncogene Src family protein tyrosine kinases (SFKs) transmit growth factor signals to the cytoplasm. Here the authors show that the solubilising factor UNC119 sequesters myristoylated SFKs to maintain its enrichment at the plasma membrane to enable signal transduction.
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14
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Abstract
Arl2 and Arl3 are Arf-like small GTP-binding proteins of the Arf subfamily of the Ras superfamily. Despite their structural similarity and sharing of many interacting partners, Arl2 and Arl3 have different biochemical properties and biological functions. Growing evidence suggest that Arl2 and Arl3 play a fundamental role as regulators of trafficking of lipid modified proteins between different compartments. Here we highlight the similarities and differences between these 2 homologous proteins and discuss the sorting mechanism of lipidated cargo into the ciliary compartment through the carriers PDE6δ and Unc119 and the release factors Arl2 and Arl3.
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Affiliation(s)
- Eyad K Fansa
- a Max Planck Institute of Molecular Physiology , Dortmund , Germany
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15
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Jaiswal M, Fansa EK, Kösling SK, Mejuch T, Waldmann H, Wittinghofer A. Novel Biochemical and Structural Insights into the Interaction of Myristoylated Cargo with Unc119 Protein and Their Release by Arl2/3. J Biol Chem 2016; 291:20766-78. [PMID: 27481943 PMCID: PMC5034065 DOI: 10.1074/jbc.m116.741827] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Revised: 07/29/2016] [Indexed: 11/06/2022] Open
Abstract
Primary cilia are highly specialized small antenna-like cellular protrusions that extend from the cell surface of many eukaryotic cell types. The protein content inside cilia and cytoplasm is very different, but details of the sorting process are not understood for most ciliary proteins. Recently, we have shown that prenylated proteins are sorted according to their affinity to the carrier protein PDE6δ and the ability of Arl3 but not Arl2 to release high affinity cargo inside the cilia (Fansa, E. K., Kösling, S. K., Zent, E., Wittinghofer, A., and Ismail, S. (2016) Nat. Commun. 7, 11366). Here we address the question whether a similar principle governs the transport of myristoylated cargo by the carrier proteins Unc119a and Unc119b. We thus analyzed the binding strength of N-terminal myristoylated cargo peptides (GNAT1, NPHP3, Cystin1, RP2, and Src) to Unc119a and Unc119b proteins. The affinity between myristoylated cargo and carrier protein, Unc119, varies between subnanomolar and micromolar. Peptides derived from ciliary localizing proteins (GNAT1, NPHP3, and Cystin1) bind with high affinity to Unc119 proteins, whereas a peptide derived from a non-ciliary localizing protein (Src) has low affinity. The peptide with intermediate affinity (RP2) is localized at the ciliary transition zone as a gate keeper. We show that the low affinity peptides are released by both Arl2·GppNHp and Arl3·GppNHp, whereas the high affinity peptides are exclusively released by only Arl3·GppNHp. Determination of the x-ray structure of myristoylated NPHP3 peptide in complex with Unc119a reveals the molecular details of high affinity binding and suggests the importance of the residues at the +2 and +3 positions relative to the myristoylated glycine for high and low affinities. The mutational analysis of swapping the residues at the +2 and +3 positions between high and low affinity peptides results in reversing their affinities for Unc119a and leads to a partial mislocalization of a low affinity mutant of NPHP3.
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Affiliation(s)
| | | | | | - Tom Mejuch
- the Department of Chemical Biology, Max Planck Institute of Molecular Physiology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
| | - Herbert Waldmann
- the Department of Chemical Biology, Max Planck Institute of Molecular Physiology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
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16
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Hanke-Gogokhia C, Wu Z, Gerstner CD, Frederick JM, Zhang H, Baehr W. Arf-like Protein 3 (ARL3) Regulates Protein Trafficking and Ciliogenesis in Mouse Photoreceptors. J Biol Chem 2016; 291:7142-55. [PMID: 26814127 DOI: 10.1074/jbc.m115.710954] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Indexed: 12/22/2022] Open
Abstract
Arf-like protein 3 (ARL3) is a ubiquitous small GTPase expressed in ciliated cells of plants and animals. Germline deletion ofArl3in mice causes multiorgan ciliopathy reminiscent of Bardet-Biedl or Joubert syndromes. As photoreceptors are elegantly compartmentalized and have cilia, we probed the function of ARL3 (ADP-ribosylation factor (Arf)-like 3 protein) by generating rod photoreceptor-specific (prefix(rod)) and retina-specific (prefix(ret))Arl3deletions. In predegenerate(rod)Arl3(-/-)mice, lipidated phototransduction proteins showed trafficking deficiencies, consistent with the role of ARL3 as a cargo displacement factor for lipid-binding proteins. By contrast,(ret)Arl3(-/-)rods and cones expressing Cre recombinase during embryonic development formed neither connecting cilia nor outer segments and degenerated rapidly. Absence of cilia infers participation of ARL3 in ciliogenesis and axoneme formation. Ciliogenesis was rescued, and degeneration was reversed in part by subretinal injection of adeno-associated virus particles expressing ARL3-EGFP. The conditional knock-out phenotypes permitted identification of two ARL3 functions, both in the GTP-bound form as follows: one as a regulator of intraflagellar transport participating in photoreceptor ciliogenesis and the other as a cargo displacement factor transporting lipidated protein to the outer segment. Surprisingly, a farnesylated inositol polyphosphate phosphatase only trafficked from the endoplasmic reticulum to the Golgi, thereby excluding it from a role in photoreceptor cilia physiology.
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Affiliation(s)
- Christin Hanke-Gogokhia
- From the Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, and the Department of Biochemistry and Biology, University of Potsdam, 14476 Potsdam-Golm, Germany
| | - Zhijian Wu
- the NEI, National Institutes of Health, Bethesda, Maryland 20892
| | - Cecilia D Gerstner
- From the Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, and
| | - Jeanne M Frederick
- From the Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, and
| | - Houbin Zhang
- the Sichuan Provincial Key Laboratory for Human Disease Gene Study, Institute of Laboratory Medicine, Hospital of University of Electronic Science and Technology of China and Sichuan Provincial People's Hospital, Chengdu, 610072 Sichuan, China, the School of Medicine, University of Electronic Science and Technology of China, Chengdu, 610072 Sichuan, China, and
| | - Wolfgang Baehr
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah 84132, From the Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, and the Department of Biology, University of Utah, Salt Lake City, Utah 84112
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17
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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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18
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Kapoor S, Fansa EK, Möbitz S, Ismail SA, Winter R, Wittinghofer A, Weise K. Effect of the N-Terminal Helix and Nucleotide Loading on the Membrane and Effector Binding of Arl2/3. Biophys J 2015; 109:1619-29. [PMID: 26488653 PMCID: PMC4624342 DOI: 10.1016/j.bpj.2015.08.033] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Revised: 08/05/2015] [Accepted: 08/10/2015] [Indexed: 01/02/2023] Open
Abstract
The small GTP-binding proteins Arl2 and Arl3, which are close homologs, share a number of interacting partners and act as displacement factors for prenylated and myristoylated cargo. Nevertheless, both proteins have distinct biological functions. Whereas Arl3 is considered a ciliary protein, Arl2 has been reported to be involved in tubulin folding, mitochondrial function, and Ras signaling. How these different roles are attained by the two homolog proteins is not fully understood. Recently, we showed that the N-terminal amphipathic helix of Arl3, but not that of Arl2, regulates the release of myristoylated ciliary proteins from the GDI-like solubilizing factor UNC119a/b. In the biophysical study presented here, both proteins are shown to exhibit a preferential localization and clustering in liquid-disordered domains of phase-separated membranes. However, the membrane interaction behavior differs significantly between both proteins with regard to their nucleotide loading. Whereas Arl3 and other Arf proteins with an N-terminal amphipathic helix require GTP loading for the interaction with membranes, Arl2 binds to membranes in a nucleotide-independent manner. In contrast to Arl2, the N-terminal helix of Arl3 increases the binding affinity to UNC119a. Furthermore, UNC119a impedes membrane binding of Arl3, but not of Arl2. Taken together, these results suggest an interplay among the nucleotide status of Arl3, the location of the N-terminal helix, membrane fluidity and binding, and the release of lipid modified cargos from carriers such as UNC119a. Since a specific Arl3-GEF is postulated to reside inside cilia, the N-terminal helix of Arl3•GTP would be available for allosteric regulation of UNC119a cargo release only inside cilia.
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Affiliation(s)
- Shobhna Kapoor
- Physical Chemistry I - Biophysical Chemistry, TU Dortmund University, Dortmund, Germany; Department of Chemical Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Eyad K Fansa
- Structural Biology Group, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Simone Möbitz
- Physical Chemistry I - Biophysical Chemistry, TU Dortmund University, Dortmund, Germany
| | - Shehab A Ismail
- Structural Biology Group, Max Planck Institute of Molecular Physiology, Dortmund, Germany; Structural Biology of Cilia, CR-UK Beatson Institute, Glasgow, United Kingdom
| | - Roland Winter
- Physical Chemistry I - Biophysical Chemistry, TU Dortmund University, Dortmund, Germany
| | - Alfred Wittinghofer
- Structural Biology Group, Max Planck Institute of Molecular Physiology, Dortmund, Germany.
| | - Katrin Weise
- Physical Chemistry I - Biophysical Chemistry, TU Dortmund University, Dortmund, Germany.
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19
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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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20
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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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21
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Toyama R, Kim MH, Rebbert ML, Gonzales J, Burgess H, Dawid IB. Habenular commissure formation in zebrafish is regulated by the pineal gland-specific gene unc119c. Dev Dyn 2013; 242:1033-42. [PMID: 23749482 DOI: 10.1002/dvdy.23994] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2012] [Revised: 05/24/2013] [Accepted: 05/26/2013] [Indexed: 11/05/2022] Open
Abstract
BACKGROUND The zebrafish pineal gland (epiphysis) is a site of melatonin production, contains photoreceptor cells, and functions as a circadian clock pacemaker. Since it is located on the surface of the forebrain, it is accessible for manipulation and, therefore, is a useful model system to analyze pineal gland function and development. We previously analyzed the pineal transcriptome during development and showed that many genes exhibit a highly dynamic expression pattern in the pineal gland. RESULTS Among genes preferentially expressed in the zebrafish pineal gland, we identified a tissue-specific form of the unc119 gene family, unc119c, which is highly preferentially expressed in the pineal gland during day and night at all stages examined from embryo to adult. When expression of unc119c was inhibited, the formation of the habenular commissure (HC) was specifically compromised. The Unc119c interacting factors Arl3l1 and Arl3l2 as well as Wnt4a also proved indispensible for HC formation. CONCLUSIONS We suggest that Unc119c, together with Arl3l1/2, plays an important role in modulating Wnt4a production and secretion during HC formation in the forebrain of the zebrafish embryo.
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Affiliation(s)
- Reiko Toyama
- Program in Genomics of Development, NICHD, NIH, Bethesda, Maryland, USA
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22
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Mori R, Toda T. The dual role of fission yeast Tbc1/cofactor C orchestrates microtubule homeostasis in tubulin folding and acts as a GAP for GTPase Alp41/Arl2. Mol Biol Cell 2013; 24:1713-24, S1-8. [PMID: 23576550 PMCID: PMC3667724 DOI: 10.1091/mbc.e12-11-0792] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2012] [Revised: 02/22/2013] [Accepted: 03/29/2013] [Indexed: 11/11/2022] Open
Abstract
Supplying the appropriate amount of correctly folded α/β-tubulin heterodimers is critical for microtubule dynamics. Formation of assembly-competent heterodimers is remarkably elaborate at the molecular level, in which the α- and β-tubulins are separately processed in a chaperone-dependent manner. This sequential step is performed by the tubulin-folding cofactor pathway, comprising a specific set of regulatory proteins: cofactors A-E. We identified the fission yeast cofactor: the orthologue of cofactor C, Tbc1. In addition to its roles in tubulin folding, Tbc1 acts as a GAP in regulating Alp41/Arl2, a highly conserved small GTPase. Of interest, the expression of GDP- or GTP-bound Alp41 showed the identical microtubule loss phenotype, suggesting that continuous cycling between these forms is important for its functions. In addition, we found that Alp41 interacts with Alp1(D), the orthologue of cofactor D, specifically when in the GDP-bound form. Intriguingly, Alp1(D) colocalizes with microtubules when in excess, eventually leading to depolymerization, which is sequestered by co-overproducing GDP-bound Alp41. We present a model of the final stages of the tubulin cofactor pathway that includes a dual role for both Tbc1 and Alp1(D) in opposing regulation of the microtubule.
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Affiliation(s)
- Risa Mori
- Cell Regulation Laboratory, Cancer Research UK, London Research Institute, Lincoln's Inn Fields Laboratories, London WC2A 3LY, United Kingdom
| | - Takashi Toda
- Cell Regulation Laboratory, Cancer Research UK, London Research Institute, Lincoln's Inn Fields Laboratories, London WC2A 3LY, United Kingdom
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23
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Lee Y, Chung S, Baek IK, Lee TH, Paik SY, Lee J. UNC119a bridges the transmission of Fyn signals to Rab11, leading to the completion of cytokinesis. Cell Cycle 2013; 12:1303-15. [PMID: 23535298 PMCID: PMC3674094 DOI: 10.4161/cc.24404] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Src family kinases (SFKs) regulate the completion of cytokinesis through signal transduction pathways that lead to the Rab11-dependent phosphorylation of ERK and its localization to the midbody of cytokinetic cells. We find that UNC119a, a known activator of SFKs, plays essential roles in this signaling pathway. UNC119a localizes to the centrosome in interphase cells and begins to translocate from the spindle pole to the spindle midzone after the onset of mitosis; it then localizes to the intercellular bridge in telophase cells and to the midbody in cytokinetic cells. We show that the midbody localization of UNC119a is dependent on Rab11, and that knocking down UNC119a inhibits the Rab11-dependent phosphorylation and midbody localization of ERK and cytokinesis. Moreover, we demonstrate that UNC119a interacts with a Src family kinase, Fyn and is required for the activation of this kinase. These results suggest that UNC119a plays a key role in the Fyn signal transduction pathway, which regulates the completion of cytokinesis via Rab11.
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Affiliation(s)
- YuKyung Lee
- Department of Systems Biology, Yonsei University, Seoul, Korea
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24
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Sinha S, Majumder A, Belcastro M, Sokolov M, Artemyev NO. Expression and subcellular distribution of UNC119a, a protein partner of transducin α subunit in rod photoreceptors. Cell Signal 2012; 25:341-8. [PMID: 23072788 DOI: 10.1016/j.cellsig.2012.10.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Accepted: 10/10/2012] [Indexed: 10/27/2022]
Abstract
A recently discovered interaction of rod transducin α subunit (Gα(t1)) with UNC119a is thought to be important for transducin trafficking in photoreceptors. In this study, we analyzed the subcellular distribution of UNC119a under different conditions of illumination in vivo. Analyses by immunofluorescence and Western blotting of retina serial tangential sections demonstrated that UNC119a resides predominantly in the rod inner segment, with a small fraction of UNC119a also appearing to infiltrate the rod outer segment. Such a distribution is consistent with the proposed role of UNC119a in facilitating transducin transport from the rod inner segment to the outer segment in the dark. In addition, UNC119a was present in smaller amounts in the cell body and synaptic region of rods. The profile of UNC119a subcellular distribution remained largely unchanged under all tested conditions of illumination, and correlated with the profile of Gα(t1) following its light-dependent translocation. Quantification by Western blotting suggested that mouse retina contains ~17 pmol of UNC119a, giving a ~1 to 4 molar ratio of UNC119a to Gα(t1). Hence, light-translocated Gα(t1) can serve as a major partner of UNC119a. Supporting this role, the levels of UNC119a were downregulated by about 2-fold in mouse retina lacking Gα(t1). As a dominant partner, Gα(t1) may potentially modulate the function of other known UNC119a-interacting proteins involved in photoreceptor ciliary trafficking and synaptic regulation, in a light-dependent manner.
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Affiliation(s)
- Satyabrata Sinha
- Department of Ophthalmology, West Virginia University, Morgantown, WV, USA
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25
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Constantine R, Zhang H, Gerstner CD, Frederick JM, Baehr W. Uncoordinated (UNC)119: coordinating the trafficking of myristoylated proteins. Vision Res 2012; 75:26-32. [PMID: 23000199 DOI: 10.1016/j.visres.2012.08.012] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2012] [Revised: 08/16/2012] [Accepted: 08/17/2012] [Indexed: 01/06/2023]
Abstract
The mechanism by which myristoylated proteins are targeted to specific subcellular membrane compartments is poorly understood. Two novel acyl-binding proteins, UNC119A and UNC119B, have been shown recently to function as chaperones/co-factors in the transport of myristoylated G protein α-subunits and src-type tyrosine kinases. UNC119 polypeptides feature an immunoglobulin-like β-sandwich fold that forms a hydrophobic pocket capable of binding lauroyl (C12) and myristoyl (C14) side chains. UNC119A in rod photoreceptors facilitates the transfer of transducin α subunits (Tα) from inner segment to outer segment membranes by forming an intermediate diffusible UNC119-Tα complex. Similar complexes are formed in other sensory neurons, as the G proteins ODR-3 and GPA-13 in Caenorhabditis elegans unc-119 mutants traffic inappropriately. UNC119B knockdown in IMCD3 cells prevents trafficking ofmyristoylated nephrocystin-3 (NPHP3), a protein associated with nephronophthisis, to cilia. Further, UNC119A was shown to transport myristoylated src-type tyrosine kinases to cell membranes and to affect T-cell receptor (TCR) and interleukin-5 receptor (IL-5R) activities. These interactions establish UNC119 polypeptides as novel lipid-binding chaperones with specificity for a diverse subset of myristoylated proteins.
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Affiliation(s)
- Ryan Constantine
- Graduate Program in Neuroscience, University of Utah Health Science Center, Salt Lake City, UT 84132, USA
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26
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Structural basis for Arl3-specific release of myristoylated ciliary cargo from UNC119. EMBO J 2012; 31:4085-94. [PMID: 22960633 DOI: 10.1038/emboj.2012.257] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Accepted: 08/20/2012] [Indexed: 12/29/2022] Open
Abstract
Access to the ciliary membrane for trans-membrane or membrane-associated proteins is a regulated process. Previously, we have shown that the closely homologous small G proteins Arl2 and Arl3 allosterically regulate prenylated cargo release from PDEδ. UNC119/HRG4 is responsible for ciliary delivery of myristoylated cargo. Here, we show that although Arl3 and Arl2 bind UNC119 with similar affinities, only Arl3 allosterically displaces cargo by accelerating its release by three orders of magnitude. Crystal structures of Arl3 and Arl2 in complex with UNC119a reveal the molecular basis of specificity. Contrary to previous structures of GTP-bound Arf subfamily proteins, the N-terminal amphipathic helix of Arl3·GppNHp is not displaced by the interswitch toggle but remains bound on the surface of the protein. Opposite to the mechanism of cargo release on PDEδ, this induces a widening of the myristoyl binding pocket. This leads us to propose that ciliary targeting of myristoylated proteins is not only dependent on nucleotide status but also on the cellular localization of Arl3.
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27
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Gopalakrishna KN, Doddapuneni K, Boyd KK, Masuho I, Martemyanov KA, Artemyev NO. Interaction of transducin with uncoordinated 119 protein (UNC119): implications for the model of transducin trafficking in rod photoreceptors. J Biol Chem 2011; 286:28954-28962. [PMID: 21712387 DOI: 10.1074/jbc.m111.268821] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The key visual G protein, transducin undergoes bi-directional translocations between the outer segment (OS) and inner compartments of rod photoreceptors in a light-dependent manner thereby contributing to adaptation and neuroprotection of rods. A mammalian uncoordinated 119 protein (UNC119), also known as Retina Gene 4 protein (RG4), has been recently implicated in transducin transport to the OS in the dark through its interaction with the N-acylated GTP-bound transducin-α subunit (Gα(t1)). Here, we demonstrate that the interaction of human UNC119 (HRG4) with transducin is dependent on the N-acylation, but does not require the GTP-bound form of Gα(t1). The lipid specificity of UNC119 is unique: UNC119 bound the myristoylated N terminus of Gα(t1) with much higher affinity than a prenylated substrate, whereas the homologous prenyl-binding protein PrBP/δ did not interact with the myristoylated peptide. UNC119 was capable of interacting with Gα(t1)GDP as well as with heterotrimeric transducin (G(t)). This interaction of UNC119 with G(t) led to displacement of Gβ(1)γ(1) from the heterotrimer. Furthermore, UNC119 facilitated solubilization of G(t) from dark-adapted rod OS membranes. Consistent with these observations, UNC119 inhibited rhodopsin-dependent activation of G(t), but had no effect on the GTP-hydrolysis by Gα(t1). A model for the role of UNC119 in the IS→OS translocation of G(t) is proposed based on the UNC119 ability to dissociate G(t) subunits from each other and the membrane. We also found that UNC119 inhibited activation of G(o) by D2 dopamine receptor in cultured cells. Thus, UNC119 may play conserved inhibitory role in regulation of GPCR-G protein signaling in non-visual tissues.
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Affiliation(s)
- Kota N Gopalakrishna
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa 52242
| | - Krishnarao Doddapuneni
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa 52242
| | - Kimberly K Boyd
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa 52242
| | - Ikuo Masuho
- Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa City, Iowa 52242 and
| | - Kirill A Martemyanov
- Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa City, Iowa 52242 and
| | - Nikolai O Artemyev
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa 52242; Department of Neuroscience, The Scripps Research Institute, Jupiter, Florida 33458.
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Zhang H, Constantine R, Vorobiev S, Chen Y, Seetharaman J, Huang YJ, Xiao R, Montelione GT, Gerstner CD, Davis MW, Inana G, Whitby FG, Jorgensen EM, Hill CP, Tong L, Baehr W. UNC119 is required for G protein trafficking in sensory neurons. Nat Neurosci 2011; 14:874-80. [PMID: 21642972 DOI: 10.1038/nn.2835] [Citation(s) in RCA: 133] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Indexed: 12/20/2022]
Abstract
UNC119 is widely expressed among vertebrates and other phyla. We found that UNC119 recognized the acylated N terminus of the rod photoreceptor transducin α (Tα) subunit and Caenorhabditis elegans G proteins ODR-3 and GPA-13. The crystal structure of human UNC119 at 1.95-Å resolution revealed an immunoglobulin-like β-sandwich fold. Pulldowns and isothermal titration calorimetry revealed a tight interaction between UNC119 and acylated Gα peptides. The structure of co-crystals of UNC119 with an acylated Tα N-terminal peptide at 2.0 Å revealed that the lipid chain is buried deeply into UNC119's hydrophobic cavity. UNC119 bound Tα-GTP, inhibiting its GTPase activity, thereby providing a stable UNC119-Tα-GTP complex capable of diffusing from the inner segment back to the outer segment after light-induced translocation. UNC119 deletion in both mouse and C. elegans led to G protein mislocalization. Thus, UNC119 is a Gα subunit cofactor essential for G protein trafficking in sensory cilia.
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Affiliation(s)
- Houbin Zhang
- Department of Ophthalmology, University of Utah Health Science Center, Salt Lake City, Utah, USA
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Trafficking of membrane proteins to cone but not rod outer segments is dependent on heterotrimeric kinesin-II. J Neurosci 2009; 29:14287-98. [PMID: 19906976 DOI: 10.1523/jneurosci.3976-09.2009] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Heterotrimeric kinesin-II is a molecular motor localized to the inner segment, connecting cilium and axoneme of mammalian photoreceptors. Our purpose was to identify the role of kinesin-II in anterograde intraflagellar transport by photoreceptor-specific deletions of kinesin family member 3A (KIF3A), its obligatory motor subunit. In cones lacking KIF3A, membrane proteins involved in phototransduction did not traffic to the outer segments resulting in complete absence of a photopic electroretinogram and progressive cone degeneration. Rod photoreceptors lacking KIF3A degenerated rapidly between 2 and 4 weeks postnatally, but the phototransduction components including rhodopsin trafficked to the outer segments during the course of degeneration. Furthermore, KIF3A deletion did not affect synaptic anterograde trafficking. The results indicate that trafficking of membrane proteins to the outer segment is dependent on kinesin-II in cone, but not rod photoreceptors, even though rods and cones share similar structures, and closely related phototransduction polypeptides.
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30
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Veltel S, Wittinghofer A. RPGR and RP2: targets for the treatment of X-linked retinitis pigmentosa? Expert Opin Ther Targets 2009; 13:1239-51. [PMID: 19702441 DOI: 10.1517/14728220903225016] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Retinitis pigmentosa is the most important hereditary eye disease and there is currently no cure available. Although mutations were found in more than 40 genes in patients with retinitis pigmentosa, only two genes have thus far been found to be responsible for one of the most severe forms of the disease, X-linked retinitis pigmentosa. In this review, we highlight the current knowledge about the two gene products RPGR and RP2 and try to link genetic data from patients with functional data on the corresponding proteins. Based on the fact that recent gene therapeutic approaches for eye diseases are at a very promising stage, we discuss the potential of RPGR and RP2 as drug targets to treat retinitis pigmentosa.
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Affiliation(s)
- Stefan Veltel
- Max-Planck-Institut für molekulare Physiologie, Abteilung Strukturelle Biologie, Otto Hahn-Street 11, 44227 Dortmund, Germany
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31
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Toyama R, Chen X, Jhawar N, Aamar E, Epstein J, Reany N, Alon S, Gothilf Y, Klein DC, Dawid IB. Transcriptome analysis of the zebrafish pineal gland. Dev Dyn 2009; 238:1813-26. [PMID: 19504458 DOI: 10.1002/dvdy.21988] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The zebrafish pineal gland (epiphysis) is a site of melatonin production, contains photoreceptor cells, and functions as a circadian clock pace maker. Here, we have used microarray technology to study the zebrafish pineal transcriptome. Analysis of gene expression at three larval and two adult stages revealed a highly dynamic transcriptional profile, revealing many genes that are highly expressed in the zebrafish pineal gland. Statistical analysis of the data based on Gene Ontology annotation indicates that many transcription factors are highly expressed during larval stages, whereas genes dedicated to phototransduction are preferentially expressed in the adult. Furthermore, several genes were identified that exhibit day/night differences in expression. Among the multiple candidate genes suggested by these data, we note the identification of a tissue-specific form of the unc119 gene with a possible role in pineal development.
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Affiliation(s)
- Reiko Toyama
- Laboratory of Molecular Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, Maryland, USA.
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32
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Zhang T, Li S, Zhang Y, Zhong C, Lai Z, Ding J. Crystal structure of the ARL2-GTP-BART complex reveals a novel recognition and binding mode of small GTPase with effector. Structure 2009; 17:602-10. [PMID: 19368893 DOI: 10.1016/j.str.2009.01.014] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2008] [Revised: 01/02/2009] [Accepted: 01/16/2009] [Indexed: 11/17/2022]
Abstract
ARL2 is a member of the ADP-ribosylation factor family but has unique biochemical features. BART is an effector of ARL2 that is essential for nuclear retention of STAT3 and may also be involved in mitochondria transport and apoptosis. Here we report the crystal structure and biochemical characterization of human ARL2-GTP-BART complex. ARL2-GTP assumes a typical small GTPase fold with a unique N-terminal alpha helix conformation. BART consists of a six alpha helix bundle. The interactions between ARL2 and BART involve two interfaces: a conserved N-terminal LLXIL motif of ARL2 is embedded in a hydrophobic cleft of BART and the switch regions of ARL2 interact with helix alpha3 of BART. Both interfaces are essential for the binding as verified by mutagenesis study. This novel recognition and binding mode is different from that of other small GTPase-effector interactions and provides molecular basis for the high specificity of ARL2 for BART.
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Affiliation(s)
- Tianlong Zhang
- Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Shanghai 200031, China
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33
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Alpadi K, Magupalli VG, Käppel S, Köblitz L, Schwarz K, Seigel GM, Sung CH, Schmitz F. RIBEYE recruits Munc119, a mammalian ortholog of the Caenorhabditis elegans protein unc119, to synaptic ribbons of photoreceptor synapses. J Biol Chem 2008; 283:26461-7. [PMID: 18664567 PMCID: PMC3258921 DOI: 10.1074/jbc.m801625200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2008] [Revised: 07/07/2008] [Indexed: 11/06/2022] Open
Abstract
Munc119 (also denoted as RG4) is a mammalian ortholog of the Caenorhabditis elegans protein unc119 and is essential for vision and synaptic transmission at photoreceptor ribbon synapses by unknown molecular mechanisms. Munc119/RG4 is related to the prenyl-binding protein PrBP/delta and expressed at high levels in photoreceptor ribbon synapses. Synaptic ribbons are presynaptic specializations in the active zone of these tonically active synapses and contain RIBEYE as a unique and major component. In the present study, we identified Munc119 as a RIBEYE-interacting protein at photoreceptor ribbon synapses using five independent approaches. The PrBP/delta homology domain of Munc119 is essential for the interaction with the NADH binding region of RIBEYE(B) domain. But RIBEYE-Munc119 interaction does not depend on NADH binding. A RIBEYE point mutant (RE(B)E844Q) that no longer interacted with Munc119 still bound NADH, arguing that binding of Munc119 and NADH to RIBEYE are independent from each other. Our data indicate that Munc119 is a synaptic ribbon-associated component. We show that Munc119 can be recruited to synaptic ribbons via its interaction with RIBEYE. Our data suggest that the RIBEYE-Munc119 interaction is essential for synaptic transmission at the photoreceptor ribbon synapse.
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Affiliation(s)
- Kannan Alpadi
- Department of Neuroanatomy, Institute for
Anatomy and Cell Biology, Saarland University, Medical School Homburg/Saar,
66421 Homburg/Saar, Germany, the Department of
Ophthalmology, Physiology, and Biophysics, SUNY University at Buffalo,
Buffalo, New York 14214, and the Margaret M.
Dyson Vision Research Institute, Department of Ophthalmology, Cell and
Developmental Biology, Weill Medical College of Cornell University, New York,
New York 10021
| | - Venkat Giri Magupalli
- Department of Neuroanatomy, Institute for
Anatomy and Cell Biology, Saarland University, Medical School Homburg/Saar,
66421 Homburg/Saar, Germany, the Department of
Ophthalmology, Physiology, and Biophysics, SUNY University at Buffalo,
Buffalo, New York 14214, and the Margaret M.
Dyson Vision Research Institute, Department of Ophthalmology, Cell and
Developmental Biology, Weill Medical College of Cornell University, New York,
New York 10021
| | - Stefanie Käppel
- Department of Neuroanatomy, Institute for
Anatomy and Cell Biology, Saarland University, Medical School Homburg/Saar,
66421 Homburg/Saar, Germany, the Department of
Ophthalmology, Physiology, and Biophysics, SUNY University at Buffalo,
Buffalo, New York 14214, and the Margaret M.
Dyson Vision Research Institute, Department of Ophthalmology, Cell and
Developmental Biology, Weill Medical College of Cornell University, New York,
New York 10021
| | - Louise Köblitz
- Department of Neuroanatomy, Institute for
Anatomy and Cell Biology, Saarland University, Medical School Homburg/Saar,
66421 Homburg/Saar, Germany, the Department of
Ophthalmology, Physiology, and Biophysics, SUNY University at Buffalo,
Buffalo, New York 14214, and the Margaret M.
Dyson Vision Research Institute, Department of Ophthalmology, Cell and
Developmental Biology, Weill Medical College of Cornell University, New York,
New York 10021
| | - Karin Schwarz
- Department of Neuroanatomy, Institute for
Anatomy and Cell Biology, Saarland University, Medical School Homburg/Saar,
66421 Homburg/Saar, Germany, the Department of
Ophthalmology, Physiology, and Biophysics, SUNY University at Buffalo,
Buffalo, New York 14214, and the Margaret M.
Dyson Vision Research Institute, Department of Ophthalmology, Cell and
Developmental Biology, Weill Medical College of Cornell University, New York,
New York 10021
| | - Gail M. Seigel
- Department of Neuroanatomy, Institute for
Anatomy and Cell Biology, Saarland University, Medical School Homburg/Saar,
66421 Homburg/Saar, Germany, the Department of
Ophthalmology, Physiology, and Biophysics, SUNY University at Buffalo,
Buffalo, New York 14214, and the Margaret M.
Dyson Vision Research Institute, Department of Ophthalmology, Cell and
Developmental Biology, Weill Medical College of Cornell University, New York,
New York 10021
| | - Ching-Hwa Sung
- Department of Neuroanatomy, Institute for
Anatomy and Cell Biology, Saarland University, Medical School Homburg/Saar,
66421 Homburg/Saar, Germany, the Department of
Ophthalmology, Physiology, and Biophysics, SUNY University at Buffalo,
Buffalo, New York 14214, and the Margaret M.
Dyson Vision Research Institute, Department of Ophthalmology, Cell and
Developmental Biology, Weill Medical College of Cornell University, New York,
New York 10021
| | - Frank Schmitz
- Department of Neuroanatomy, Institute for
Anatomy and Cell Biology, Saarland University, Medical School Homburg/Saar,
66421 Homburg/Saar, Germany, the Department of
Ophthalmology, Physiology, and Biophysics, SUNY University at Buffalo,
Buffalo, New York 14214, and the Margaret M.
Dyson Vision Research Institute, Department of Ophthalmology, Cell and
Developmental Biology, Weill Medical College of Cornell University, New York,
New York 10021
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34
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Veltel S, Kravchenko A, Ismail S, Wittinghofer A. Specificity of Arl2/Arl3 signaling is mediated by a ternary Arl3-effector-GAP complex. FEBS Lett 2008; 582:2501-7. [PMID: 18588884 DOI: 10.1016/j.febslet.2008.05.053] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2008] [Revised: 05/09/2008] [Accepted: 05/13/2008] [Indexed: 10/21/2022]
Abstract
Arl2 and Arl3, members of the Arf subfamily of small G proteins, are believed to be involved in ciliary and microtubule-dependent processes. Recently, we could identify RP2, responsible for a variant of X-linked retinitis pigmentosa, as the Arl3-specific GAP. Here, we have characterized Arl2/3 interactions. We show the formation of a ternary complex between Arl3, its cognate GAP RP2 and its retinal effector HRG4. This complex seems to be important for photoreceptor function.
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Affiliation(s)
- Stefan Veltel
- Max-Planck-Institut für molekulare Physiologie, Abteilung Strukturelle Biologie, Otto-Hahn-Strasse 11, Dortmund, Germany
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35
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The retinitis pigmentosa 2 gene product is a GTPase-activating protein for Arf-like 3. Nat Struct Mol Biol 2008; 15:373-80. [DOI: 10.1038/nsmb.1396] [Citation(s) in RCA: 136] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2007] [Accepted: 01/28/2008] [Indexed: 11/09/2022]
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36
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Abstract
Small G proteins play a central role in the organization of the secretory and endocytic pathways. The majority of such small G proteins are members of the Rab family, which are anchored to the bilayer by C-terminal prenyl groups. However, the recruitment of some effectors, including vesicle coat proteins, is mediated by a second class of small G proteins that is unique in having an N-terminal amphipathic helix that becomes available for membrane insertion upon GTP binding. Sar1, Arf1, and Arf6 are the best-characterized members of this ADP-ribosylation factor (Arf) family. In addition, all eukaryotes contain additional distantly related G proteins, often called Arf like, or Arls. The complete Arf family in humans has 29 members. The roles of these related G proteins are poorly understood, but recent work has shown that some are involved in membrane traffic or organizing the cytoskeleton. Here we review what is known about all the members of the Arf family, along with the known regulatory molecules that convert them between GDP- and GTP-bound states.
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37
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Zhang H, Li S, Doan T, Rieke F, Detwiler PB, Frederick JM, Baehr W. Deletion of PrBP/delta impedes transport of GRK1 and PDE6 catalytic subunits to photoreceptor outer segments. Proc Natl Acad Sci U S A 2007; 104:8857-62. [PMID: 17496142 PMCID: PMC1885592 DOI: 10.1073/pnas.0701681104] [Citation(s) in RCA: 141] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The mouse Pde6d gene encodes a ubiquitous prenyl binding protein, termed PrBP/delta, of largely unknown physiological function. PrBP/delta was originally identified as a putative rod cGMP phosphodiesterase (PDE6) subunit in the retina, where it is relatively abundant. To investigate the consequences of Pde6d deletion in retina, we generated a Pde6d(-/-) mouse by targeted recombination. Although manifesting reduced body weight, the Pde6d(-/-) mouse was viable and fertile and its retina developed normally. Immunocytochemistry showed that farnesylated rhodopsin kinase (GRK1) and prenylated rod PDE6 catalytic subunits partially mislocalized in Pde6d(-/-) rods, whereas rhodopsin was unaffected. In Pde6d(-/-) rod single-cell recordings, sensitivity to single photons was increased and saturating flash responses were prolonged. Pde6d(-/-) scotopic paired-flash electroretinograms indicated a delay in recovery of the dark state, likely due to reduced levels of GRK1 in rod outer segments. In Pde6d(-/-) cone outer segments, GRK1 and cone PDE6alpha' were present at very low levels and the photopic b-wave amplitudes were reduced by 70%. Thus the absence of PrBP/delta in retina impairs transport of prenylated proteins, particularly GRK1 and cone PDE, to rod and cone outer segments, resulting in altered photoreceptor physiology and a phenotype of a slowly progressing rod/cone dystrophy.
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Affiliation(s)
- H. Zhang
- *John A. Moran Eye Center, University of Utah Health Science Center, Salt Lake City, UT 84132
| | - S. Li
- *John A. Moran Eye Center, University of Utah Health Science Center, Salt Lake City, UT 84132
| | - T. Doan
- Department of Physiology and Biophysics and
| | - F. Rieke
- Department of Physiology and Biophysics and
- Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195; and
| | | | - J. M. Frederick
- *John A. Moran Eye Center, University of Utah Health Science Center, Salt Lake City, UT 84132
| | - W. Baehr
- *John A. Moran Eye Center, University of Utah Health Science Center, Salt Lake City, UT 84132
- Departments of Neurobiology and Anatomy and
- Biology, University of Utah, Salt Lake City, UT 84112
- To whom correspondence should be addressed at:
Department of Ophthalmology, University of Utah Health Science Center, 65 N. Medical Drive, Salt Lake City, UT 84132. E-mail:
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38
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Ishiba Y, Higashide T, Mori N, Kobayashi A, Kutobta S, McLaren MJ, Satoh H, Wong F, Inana G. Targeted inactivation of synaptic HRG4 (UNC119) causes dysfunction in the distal photoreceptor and slow retinal degeneration, revealing a new function. Exp Eye Res 2006; 84:473-85. [PMID: 17174953 PMCID: PMC1820979 DOI: 10.1016/j.exer.2006.10.016] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2006] [Revised: 10/24/2006] [Accepted: 10/27/2006] [Indexed: 11/23/2022]
Abstract
HRG4 (UNC119) is a photoreceptor protein predominantly localized to the photoreceptor synapses and to the inner segments to a lesser degree. A heterozygous truncation mutation in HRG4 was found in a patient with late onset cone-rod dystrophy, and a transgenic (TG) mouse expressing the identical mutant protein developed late onset retinal degeneration, confirming the pathogenic potential of HRG4. Recently, the dominant negative pathogenic mechanism in the TG model was shown to involve increased affinity of the truncated mutant HRG4 for its target, ARL2, which leads to a delayed decrease in its downstream target, mitochondrial ANT1, mitochondrial stress, synaptic degeneration, trans-synaptic degeneration, and whole photoreceptor degeneration by apoptosis. In this study, the mouse HRG4 (MRG4) gene was cloned and targeted to construct a knock-out (KO) mouse model of HRG4 in order to study the effects of completely inactivating this protein. The KO model was examined by genomic Southern blotting, Western blotting, immunofluorescence, funduscopy, LM and EM histopathology, ERG, and TUNEL analyses. The KO model developed a slowly progressive retinal degeneration, characterized by mottling in the fundus, mild thinning of the photoreceptor layer, and increase in apoptosis as early as 6 months, dramatic acceleration at approximately 17 months, and virtual obliteration of the photoreceptors by 20 months. When compared to retinal degeneration in the TG model, significant differences existed in the KO consisting of more severe and early photoreceptor death without evidence of early synaptic and trans-synaptic degeneration as seen in the TG, confirmed by LM and EM histopathology, ERG, and Western blotting of synaptic proteins. The results indicated a dysfunction in the KO outside the synapses in the distal end of photoreceptors where MRG4 is also localized. Differences in the phenotypes of retinal degeneration in the KO and TG models reflect a dysfunction in the two opposite ends of photoreceptors, i.e., the distal inner/outer segments and proximal synapses, respectively, indicating a second function of MRG4 in the distal photoreceptor and dual functionality of MRG4. Thus, inactivation of MRG4 by gene targeting resulted in a retinal degeneration phenotype quite different from that previously seen in the TG, attesting to the multiplicity of MRG4 function, in addition to the importance of this protein for normal retinal function. These models will be useful in elucidating the functions of HRG4/MRG4 and the mechanism of slow retinal degeneration.
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MESH Headings
- Adaptor Proteins, Signal Transducing
- Animals
- Apoptosis
- Blotting, Western/methods
- Cloning, Molecular
- Electroretinography
- Fluorescent Antibody Technique
- Fundus Oculi
- Gene Targeting
- Humans
- In Situ Nick-End Labeling
- Intracellular Signaling Peptides and Proteins/genetics
- Intracellular Signaling Peptides and Proteins/metabolism
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Mice, Transgenic
- Microtubule Proteins/genetics
- Microtubule Proteins/metabolism
- Models, Animal
- Mutation
- Photoreceptor Cells, Vertebrate/metabolism
- Photoreceptor Cells, Vertebrate/pathology
- Photoreceptor Cells, Vertebrate/physiology
- Retina/pathology
- Retinal Degeneration/metabolism
- Retinal Degeneration/pathology
- Retinal Degeneration/physiopathology
- Synapses/metabolism
- Synapses/pathology
- Synapses/physiology
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Affiliation(s)
- Yasutsugu Ishiba
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL 33136
| | - Tomomi Higashide
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL 33136
| | - Naoki Mori
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL 33136
| | - Akira Kobayashi
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL 33136
| | - Shinya Kutobta
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL 33136
| | | | - Hiromasa Satoh
- Department of Ophthalmology, Duke University School of Medicine, Durham, NC.27710
| | - Fulton Wong
- Department of Ophthalmology, Duke University School of Medicine, Durham, NC.27710
| | - George Inana
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL 33136
- Address correspondence to: George Inana, M.D., Ph.D., Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, 1638 N.W. 10 Avenue, Miami, FL 33136, U.S.A., Tel. 305-326-6509, Fax. 305-326-6029, Email.
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39
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Zhang H, Hosier S, Terew JM, Zhang K, Cote RH, Baehr W. Assay and functional properties of PrBP(PDEdelta), a prenyl-binding protein interacting with multiple partners. Methods Enzymol 2006; 403:42-56. [PMID: 16473576 DOI: 10.1016/s0076-6879(05)03005-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
A 17-kDa prenyl-binding protein, PrBP(PDEdelta), is highly conserved among various species from human to Caenorhabditis elegans. First identified as a putative regulatory delta subunit of the cyclic nucleotide phosphodiesterase (PDE6) purified from mammalian photoreceptor cells, PrBP(PDEdelta) has been hypothesized to reduce activation of PDE6 by the heterotrimeric G-protein, transducin, thereby desensitizing the photoresponse. However, recent work shows that PrBP(PDEdelta) interacts with numerous prenylated proteins at their farnesylated or geranylgeranylated C-termini, as well as with non-prenylated proteins. These polypeptides include small GTPases such as Rab13, Ras, Rap, and Rho6, as well as components involved in phototransduction (e.g., rod and cone PDE6, rod and cone opsin kinases). Expression of PrBP(PDEdelta) in tissues and organisms not expressing PDE6, the demonstration of multiple interacting partners with PrBP(PDEdelta), and its low abundance in rod outer segments all argue against it being a regulatory PDE6 subunit. This raises intriguing questions as to its physiological functions. In this chapter, we review the current status of PrBP(PDEdelta) and describe some of the assays used to determine these interactions in detail. In mammalian photoreceptors, the results are consistent with a role of PrBP(PDEdelta) in the transport of prenylated proteins from their site of synthesis in the inner segment to the outer segment where phototransduction occurs.
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40
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Zhou C, Cunningham L, Marcus AI, Li Y, Kahn RA. Arl2 and Arl3 regulate different microtubule-dependent processes. Mol Biol Cell 2006; 17:2476-87. [PMID: 16525022 PMCID: PMC1446103 DOI: 10.1091/mbc.e05-10-0929] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Arl2 and Arl3 are closely related members of the Arf family of regulatory GTPases that arose from a common ancestor early in eukaryotic evolution yet retain extensive structural, biochemical, and functional features. The presence of Arl3 in centrosomes, mitotic spindles, midzones, midbodies, and cilia are all supportive of roles in microtubule-dependent processes. Knockdown of Arl3 by siRNA resulted in changes in cell morphology, increased acetylation of alpha-tubulin, failure of cytokinesis, and increased number of binucleated cells. We conclude that Arl3 binds microtubules in a regulated manner to alter specific aspects of cytokinesis. In contrast, an excess of Arl2 activity, achieved by expression of the [Q70L]Arl2 mutant, caused the loss of microtubules and cell cycle arrest in M phase. Initial characterization of the underlying defects suggests a defect in the ability to polymerize tubulin in the presence of excess Arl2 activity. We also show that Arl2 is present in centrosomes and propose that its action in regulating tubulin polymerization is mediated at centrosomes. Somewhat paradoxically, no phenotypes were observed Arl2 expression was knocked down or Arl3 activity was increased in HeLa cells. We conclude that Arl2 and Arl3 have related but distinct roles at centrosomes and in regulating microtubule-dependent processes.
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Affiliation(s)
- Chengjing Zhou
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322-3050, USA
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Norton AW, Hosier S, Terew JM, Li N, Dhingra A, Vardi N, Baehr W, Cote RH. Evaluation of the 17-kDa prenyl-binding protein as a regulatory protein for phototransduction in retinal photoreceptors. J Biol Chem 2005; 280:1248-56. [PMID: 15504722 PMCID: PMC3392308 DOI: 10.1074/jbc.m410475200] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mammalian rod photoreceptor phosphodiesterase (PDE6) holoenzyme is isolated in both a membrane-associated and a soluble form. Membrane binding is a consequence of prenylation of PDE6 catalytic subunits, whereas soluble PDE6 is purified with a 17-kDa prenyl-binding protein (PDEdelta) tightly bound. This protein, here termed PrBP/delta, has been hypothesized to reduce activation of PDE6 by transducin, thereby desensitizing the photoresponse. To test the potential role of PrBP/delta in regulating phototransduction, we examined the abundance, localization, and potential binding partners of PrBP/delta in retina and in purified rod outer segment (ROS) suspensions whose physiological and biochemical properties are well characterized. The amphibian homologue of PrBP/delta was cloned and sequenced and found to have 82% amino acid sequence identity with mammalian PrBP/delta. In contrast to bovine ROS, all of the PDE6 in purified frog ROS is membrane-associated. However, addition of recombinant frog PrBP/delta can solubilize PDE6 and prevent its activation by transducin. PrBP/delta also binds other prenylated photoreceptor proteins in vitro, including opsin kinase (GRK1/GRK7) and rab8. Quantitative immunoblot analysis of the PrBP/delta content of purified ROS reveals insufficient amounts of PrBP/delta (<0.1 PrBP/delta per PDE6) to serve as a subunit of PDE6 in either mammalian or amphibian photoreceptors. The immunolocalization of PrBP/delta in frog and bovine retina shows greatest PrBP/delta immunolabeling outside the photoreceptor cell layer. Within photoreceptors, only the inner segments of frog double cones are strongly labeled, whereas bovine photoreceptors reveal more PrBP/delta labeling near the junction of the inner and outer segments (connecting cilium) of photoreceptors. Together, these results rule out PrBP/delta as a PDE6 subunit and implicate PrBP/delta in the transport and membrane targeting of prenylated proteins (including PDE6) from their site of synthesis in the inner segment to their final destination in the outer segment of rods and cones.
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Affiliation(s)
- Angela W. Norton
- Department of Biochemistry and Molecular Biology, University of New Hampshire, Durham, New Hampshire 03824-2617
| | - Suzanne Hosier
- Department of Biochemistry and Molecular Biology, University of New Hampshire, Durham, New Hampshire 03824-2617
| | - Jennifer M. Terew
- Department of Biochemistry and Molecular Biology, University of New Hampshire, Durham, New Hampshire 03824-2617
| | - Ning Li
- Moran Eye Center, University of Utah Health Center, Salt Lake City, Utah 84132
| | - Anuradha Dhingra
- Department of Neuroscience, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Noga Vardi
- Department of Neuroscience, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Wolfgang Baehr
- Moran Eye Center, University of Utah Health Center, Salt Lake City, Utah 84132
| | - Rick H. Cote
- Department of Biochemistry and Molecular Biology, University of New Hampshire, Durham, New Hampshire 03824-2617
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Abstract
ADP-ribosylation factor (Arf) GTP-binding proteins are among the best-characterized members of the Ras superfamily of GTPases, with well-established functions in membrane-trafficking pathways. A recent watershed of genomic and structural information has identified a family of conserved related proteins: the Arf-like (Arl) GTPases. The best-characterized Arl protein, Arl2, regulates the folding of beta tubulin, and recent data suggest that Arl1 and Arf-related protein 1 (ARFRP1) are localized to the trans-Golgi network (TGN), where they function, in part, to regulate the tethering of endosome-derived transport vesicles. Other Arl proteins are localized to the cytosol, nucleus, cytoskeleton and mitochondria, which indicates that Arl proteins have diverse roles that are distinct from the known functions of traditional Arf GTPases.
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Affiliation(s)
- Christopher G Burd
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6058, USA.
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Shern JF, Sharer JD, Pallas DC, Bartolini F, Cowan NJ, Reed MS, Pohl J, Kahn RA. Cytosolic Arl2 is complexed with cofactor D and protein phosphatase 2A. J Biol Chem 2003; 278:40829-36. [PMID: 12912990 DOI: 10.1074/jbc.m308678200] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Arl2 is a member of the ADP-ribosylation factor family of 20-kDa GTPases that is highly conserved in eukaryotes. Recent results revealed that a portion of cellular Arl2 and its binding partner, BART, localize to mitochondria. Because approximately 90% of cellular Arl2 is cytosolic, we investigated properties of the soluble protein and found that it is stably bound in a complex that migrates in gel filtration medium with a predicted molecular mass of approximately 300 kDa. This complex was purified approximately 500-fold from the soluble fraction of bovine brain. Protein components were identified by mass spectroscopy and revealed the presence of four other proteins that include the tubulin folding cochaperone cofactor D and all three subunits of at least two protein phosphatase 2A (PP2A) protein phosphatase trimers. The presence of more than one PP2A B-type subunit and the low stoichiometry of Arl2 indicate that the purified preparation still contains a mixture of complexes that cannot currently be completely resolved. Thus, although all the soluble Arl2 in bovine brain is in high molecular mass complexes, only a portion of the total cellular cofactor D and PP2A are associated with the Arl2. We further show that the Arl2 in the complex cannot bind GTP and that complexed cofactor D does not efficiently participate in tubulin refolding reactions in a manner comparable with free cofactor D. Our data suggest functional roles for the cytosolic Arl2 complex in modulating tubulin and microtubule behavior as well as a possible role in apoptosis.
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Affiliation(s)
- Jack F Shern
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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Zhang H, Liu XH, Zhang K, Chen CK, Frederick JM, Prestwich GD, Baehr W. Photoreceptor cGMP phosphodiesterase delta subunit (PDEdelta) functions as a prenyl-binding protein. J Biol Chem 2003; 279:407-13. [PMID: 14561760 DOI: 10.1074/jbc.m306559200] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Bovine PDEdelta was originally copurified with rod cGMP phosphodiesterase (PDE) and shown to interact with prenylated, carboxymethylated C-terminal Cys residues. Other studies showed that PDEdelta can interact with several small GTPases including Rab13, Ras, Rap, and Rho6, all of which are prenylated, as well as the N-terminal portion of retinitis pigmentosa GTPase regulator and Arl2/Arl3, which are not prenylated. We show by immunocytochemistry with a PDEdelta-specific antibody that PDEdelta is present in rods and cones. We find by yeast two-hybrid screening with a PDEdelta bait that it can interact with farnesylated rhodopsin kinase (GRK1) and that prenylation is essential for this interaction. In vitro binding assays indicate that both recombinant farnesylated GRK1 and geranylgeranylated GRK7 co-precipitate with a glutathione S-transferase-PDEdelta fusion protein. Using fluorescence resonance energy transfer techniques exploiting the intrinsic tryptophan fluorescence of PDEdelta and dansylated prenyl cysteines as fluorescent ligands, we show that PDEdelta specifically binds geranylgeranyl and farnesyl moieties with a Kd of 19.06 and 0.70 microm, respectively. Our experiments establish that PDEdelta functions as a prenyl-binding protein interacting with multiple prenylated proteins.
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Affiliation(s)
- Houbin Zhang
- Department of Neurobiology and Anatomy, University of Utah, Salt Lake City, Utah 84112, USA
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