1
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Tebbe L, Kakakhel M, Al-Ubaidi MR, Naash MI. The role of syntaxins in retinal function and health. Front Cell Neurosci 2024; 18:1380064. [PMID: 38799985 PMCID: PMC11119284 DOI: 10.3389/fncel.2024.1380064] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Accepted: 04/16/2024] [Indexed: 05/29/2024] Open
Abstract
The soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein (SNAP) receptor (SNARE) superfamily plays a pivotal role in cellular trafficking by facilitating membrane fusion events. These SNARE proteins, including syntaxins, assemble into complexes that actively facilitate specific membrane fusion events. Syntaxins, as integral components of the SNARE complex, play a crucial role in initiating and regulating these fusion activities. While specific syntaxins have been extensively studied in various cellular processes, including neurotransmitter release, autophagy and endoplasmic reticulum (ER)-to-Golgi protein transport, their roles in the retina remain less explored. This review aims to enhance our understanding of syntaxins' functions in the retina by shedding light on how syntaxins mediate membrane fusion events unique to the retina. Additionally, we seek to establish a connection between syntaxin mutations and retinal diseases. By exploring the intricate interplay of syntaxins in retinal function and health, we aim to contribute to the broader comprehension of cellular trafficking in the context of retinal physiology and pathology.
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Affiliation(s)
| | | | | | - Muna I. Naash
- *Correspondence: Muna I. Naash, ; Muayyad R. Al-Ubaidi,
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2
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Clark AM, Yu D, Neiswanger G, Zhu D, Zou J, Maschek JA, Burgoyne T, Yang J. Disruption of CFAP418 interaction with lipids causes widespread abnormal membrane-associated cellular processes in retinal degenerations. JCI Insight 2024; 9:e162621. [PMID: 37971880 PMCID: PMC10906455 DOI: 10.1172/jci.insight.162621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Accepted: 11/15/2023] [Indexed: 11/19/2023] Open
Abstract
Syndromic ciliopathies and retinal degenerations are large heterogeneous groups of genetic diseases. Pathogenic variants in the CFAP418 gene may cause both disorders, and its protein sequence is evolutionarily conserved. However, the disease mechanism underlying CFAP418 mutations has not been explored. Here, we apply quantitative lipidomic, proteomic, and phosphoproteomic profiling and affinity purification coupled with mass spectrometry to address the molecular function of CFAP418 in the retina. We show that CFAP418 protein binds to the lipid metabolism precursor phosphatidic acid (PA) and mitochondrion-specific lipid cardiolipin but does not form a tight and static complex with proteins. Loss of Cfap418 in mice disturbs membrane lipid homeostasis and membrane-protein associations, which subsequently causes mitochondrial defects and membrane-remodeling abnormalities across multiple vesicular trafficking pathways in photoreceptors, especially the endosomal sorting complexes required for transport (ESCRT) pathway. Ablation of Cfap418 also increases the activity of PA-binding protein kinase Cα in the retina. Overall, our results indicate that membrane lipid imbalance is a pathological mechanism underlying syndromic ciliopathies and retinal degenerations which is associated with other known causative genes of these diseases.
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Affiliation(s)
- Anna M. Clark
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, and
| | - Dongmei Yu
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, and
| | - Grace Neiswanger
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, and
| | - Daniel Zhu
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, and
| | - Junhuang Zou
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, and
| | - J. Alan Maschek
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah, USA
| | - Thomas Burgoyne
- UCL Institute of Ophthalmology, University College of London, London, United Kingdom
| | - Jun Yang
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, and
- Department of Otolaryngology, and
- Department of Neurobiology, University of Utah, Salt Lake City, Utah, USA
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3
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Huang M, Chow CH, Gurdita A, Harada H, Pham Truong VQB, Eide S, Sun HS, Feng ZP, Monnier PP, Wallace VA, Sugita S. SNAP-25, but not SNAP-23, is essential for photoreceptor development, survival, and function in mice. Commun Biol 2024; 7:34. [PMID: 38182732 PMCID: PMC10770054 DOI: 10.1038/s42003-023-05760-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Accepted: 12/29/2023] [Indexed: 01/07/2024] Open
Abstract
SNARE-mediated vesicular transport is thought to play roles in photoreceptor glutamate exocytosis and photopigment delivery. However, the functions of Synaptosomal-associated protein (SNAP) isoforms in photoreceptors are unknown. Here, we revisit the expression of SNAP-23 and SNAP-25 and generate photoreceptor-specific knockout mice to investigate their roles. Although we find that SNAP-23 shows weak mRNA expression in photoreceptors, SNAP-23 removal does not affect retinal morphology or vision. SNAP-25 mRNA is developmentally regulated and undergoes mRNA trafficking to photoreceptor inner segments at postnatal day 9 (P9). SNAP-25 knockout photoreceptors develop normally until P9 but degenerate by P14 resulting in severe retinal thinning. Photoreceptor loss in SNAP-25 knockout mice is associated with abolished electroretinograms and vision loss. We find mistrafficked photopigments, enlarged synaptic vesicles, and abnormal synaptic ribbons which potentially underlie photoreceptor degeneration. Our results conclude that SNAP-25, but not SNAP-23, mediates photopigment delivery and synaptic functioning required for photoreceptor development, survival, and function.
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Affiliation(s)
- Mengjia Huang
- Division of Experimental & Translational Neuroscience, Krembil Brain Institute, University Health Network, Toronto, ON, M5T 0S8, Canada
- Department of Physiology, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, M5S 1A8, Canada
| | - Chun Hin Chow
- Division of Experimental & Translational Neuroscience, Krembil Brain Institute, University Health Network, Toronto, ON, M5T 0S8, Canada
- Department of Physiology, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, M5S 1A8, Canada
| | - Akshay Gurdita
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, M5S 1A8, Canada
- Donald K. Johnson Eye Institute, University Health Network, Toronto, ON, M5T 0S8, Canada
| | - Hidekiyo Harada
- Donald K. Johnson Eye Institute, University Health Network, Toronto, ON, M5T 0S8, Canada
| | - Victor Q B Pham Truong
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, M5S 1A8, Canada
- Donald K. Johnson Eye Institute, University Health Network, Toronto, ON, M5T 0S8, Canada
| | - Sarah Eide
- Department of Physiology, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, M5S 1A8, Canada
| | - Hong-Shuo Sun
- Department of Physiology, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, M5S 1A8, Canada
- Department of Anatomy, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, M5S 1A8, Canada
| | - Zhong-Ping Feng
- Department of Physiology, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, M5S 1A8, Canada
| | - Philippe P Monnier
- Department of Physiology, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, M5S 1A8, Canada
- Donald K. Johnson Eye Institute, University Health Network, Toronto, ON, M5T 0S8, Canada
- Department of Ophthalmology & Vision Sciences, University of Toronto, Toronto, ON, M5T 3A9, Canada
| | - Valerie A Wallace
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, M5S 1A8, Canada
- Donald K. Johnson Eye Institute, University Health Network, Toronto, ON, M5T 0S8, Canada
- Department of Ophthalmology & Vision Sciences, University of Toronto, Toronto, ON, M5T 3A9, Canada
| | - Shuzo Sugita
- Division of Experimental & Translational Neuroscience, Krembil Brain Institute, University Health Network, Toronto, ON, M5T 0S8, Canada.
- Department of Physiology, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, M5S 1A8, Canada.
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4
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Haggerty KN, Eshelman SC, Sexton LA, Frimpong E, Rogers LM, Agosto MA, Robichaux MA. Super-resolution mapping in rod photoreceptors identifies rhodopsin trafficking through the inner segment plasma membrane as an essential subcellular pathway. PLoS Biol 2024; 22:e3002467. [PMID: 38190419 PMCID: PMC10773939 DOI: 10.1371/journal.pbio.3002467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Accepted: 12/10/2023] [Indexed: 01/10/2024] Open
Abstract
Photoreceptor cells in the vertebrate retina have a highly compartmentalized morphology for efficient phototransduction and vision. Rhodopsin, the visual pigment in rod photoreceptors, is densely packaged into the rod outer segment sensory cilium and continuously renewed through essential synthesis and trafficking pathways housed in the rod inner segment. Despite the importance of this region for rod health and maintenance, the subcellular organization of rhodopsin and its trafficking regulators in the mammalian rod inner segment remain undefined. We used super-resolution fluorescence microscopy with optimized retinal immunolabeling techniques to perform a single molecule localization analysis of rhodopsin in the inner segments of mouse rods. We found that a significant fraction of rhodopsin molecules was localized at the plasma membrane, at the surface, in an even distribution along the entire length of the inner segment, where markers of transport vesicles also colocalized. Thus, our results collectively establish a model of rhodopsin trafficking through the inner segment plasma membrane as an essential subcellular pathway in mouse rod photoreceptors.
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Affiliation(s)
- Kristen N. Haggerty
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, West Virginia, United States of America
| | - Shannon C. Eshelman
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, West Virginia, United States of America
| | - Lauren A. Sexton
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, West Virginia, United States of America
| | - Emmanuel Frimpong
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, West Virginia, United States of America
| | - Leah M. Rogers
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, West Virginia, United States of America
| | - Melina A. Agosto
- Retina and Optic Nerve Research Laboratory, Department of Physiology and Biophysics, and Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Michael A. Robichaux
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, West Virginia, United States of America
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5
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Hinsch CL, Venkata JK, Hsu T, Dammai V. Controlled Plasma Membrane Delivery of FGFR1 and Modulation of Signaling by a Novel Regulated Anterograde RTK Transport Pathway. Cancers (Basel) 2023; 15:5837. [PMID: 38136383 PMCID: PMC10741464 DOI: 10.3390/cancers15245837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Revised: 11/29/2023] [Accepted: 12/05/2023] [Indexed: 12/24/2023] Open
Abstract
How human FGFR1 localizes to the PM is unknown. Currently, it is assumed that newly synthesized FGFR1 is continuously delivered to the PM. However, evidence indicates that FGFR1 is mostly sequestered in intracellular post-Golgi vesicles (PGVs) under normal conditions. In this report, live-cell imaging and total internal reflection fluorescence microscopy (TIRFM) were employed to study the dynamics of these FGFR1-positive vesicles. We designed recombinant proteins to target different transport components to and from the FGFR1 vesicles. Mouse embryoid bodies (mEBs) were used as a 3D model system to confirm major findings. Briefly, we found that Rab2a, Rab6a, Rab8a, RalA and caveolins are integral components of FGFR1-positive vesicles, representing a novel compartment. While intracellular sequestration prevented FGFR1 activation, serum starvation and hypoxia stimulated PM localization of FGFR1. Under these conditions, FGFR1 C-terminus acts as a scaffold to assemble proteins to (i) inactivate Rab2a and release sequestration, and (ii) assemble Rab6a for localized activation of Rab8a and RalA-exocyst to deliver the receptor to the PM. This novel pathway is named Regulated Anterograde RTK Transport (RART). This is the first instance of RTK regulated through control of PM delivery.
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Affiliation(s)
- Claire Leist Hinsch
- Hollings Cancer Center, Medical University of South Carolina, Charleston, SC 29401, USA (J.K.V.)
- Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, SC 29401, USA
| | - Jagadish Kummetha Venkata
- Hollings Cancer Center, Medical University of South Carolina, Charleston, SC 29401, USA (J.K.V.)
- Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, SC 29401, USA
| | - Tien Hsu
- Graduate Institute of Biomedical Sciences, China Medical University, Taichung 40433, Taiwan
| | - Vincent Dammai
- Aldevron LLC (Danaher Corporation), Fargo, ND 58104, USA
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6
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Masek M, Bachmann-Gagescu R. Control of protein and lipid composition of photoreceptor outer segments-Implications for retinal disease. Curr Top Dev Biol 2023; 155:165-225. [PMID: 38043951 DOI: 10.1016/bs.ctdb.2023.09.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2023]
Abstract
Vision is arguably our most important sense, and its loss brings substantial limitations to daily life for affected individuals. Light is perceived in retinal photoreceptors (PRs), which are highly specialized neurons subdivided into several compartments with distinct functions. The outer segments (OSs) of photoreceptors represent highly specialized primary ciliary compartments hosting the phototransduction cascade, which transforms incoming light into a neuronal signal. Retinal disease can result from various pathomechanisms originating in distinct subcompartments of the PR cell, or in the retinal pigment epithelium which supports the PRs. Dysfunction of primary cilia causes human disorders known as "ciliopathies", in which retinal disease is a common feature. This chapter focuses on PR OSs, discussing the mechanisms controlling their complex structure and composition. A sequence of tightly regulated sorting and trafficking events, both upstream of and within this ciliary compartment, ensures the establishment and maintenance of the adequate proteome and lipidome required for signaling in response to light. We discuss in particular our current understanding of the role of ciliopathy proteins involved in multi-protein complexes at the ciliary transition zone (CC2D2A) or BBSome (BBS1) and how their dysfunction causes retinal disease. While the loss of CC2D2A prevents the fusion of vesicles and delivery of the photopigment rhodopsin to the ciliary base, leading to early OS ultrastructural defects, BBS1 deficiency results in precocious accumulation of cholesterol in mutant OSs and decreased visual function preceding morphological changes. These distinct pathomechanisms underscore the central role of ciliary proteins involved in multiple processes controlling OS protein and lipid composition.
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Affiliation(s)
- Markus Masek
- Institute of Medical Genetics, University of Zurich, Zurich, Switzerland; Department of Molecular Life Sciences, University of Zurich, Zurich, Switzerland
| | - Ruxandra Bachmann-Gagescu
- Institute of Medical Genetics, University of Zurich, Zurich, Switzerland; Department of Molecular Life Sciences, University of Zurich, Zurich, Switzerland; University Research Priority Program AdaBD, University of Zurich, Zurich, Switzerland.
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7
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Li J, Jian Y, Liu R, Zhao X, Mao J, Wei W, Jiang C, Zhang L, Wang Y, Zhou P. Choline and Fish Oil Can Improve Memory of Mice through Increasing Brain DHA Level. Foods 2023; 12:foods12091799. [PMID: 37174337 PMCID: PMC10178732 DOI: 10.3390/foods12091799] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Revised: 04/06/2023] [Accepted: 04/20/2023] [Indexed: 05/15/2023] Open
Abstract
Docosahexaenoic acid (DHA) is highly enriched in the brain, and is essential for normal brain development and function. However, evidence suggests that currently used supplements, such as fish oil, do not significantly increase brain DHA levels. Therefore, this study aimed to investigate whether combined fish oil and choline supplementation could affect the type and enrich the content of DHA in the brain. The results revealed that the combined intake of fish oil and choline upregulated the expression of key transporters and receptors, including MFSD2A, FATP1, and FABP5, which increased the uptake of DHA in the brain. Additionally, this supplementation improved the synthesis and release of acetylcholine in the brain, which, in turn, enhanced the learning and memory abilities of mice. These findings suggest that the combined intake of fish oil and choline improves the bioavailability of DHA in the brain.
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Affiliation(s)
- Jin Li
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214126, China
- School of Food Science and Technology, Jiangnan University, Wuxi 214126, China
| | - Yaqiong Jian
- School of Food Science and Technology, Jiangnan University, Wuxi 214126, China
| | - Ruonan Liu
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214126, China
- School of Food Science and Technology, Jiangnan University, Wuxi 214126, China
| | - Xianfeng Zhao
- Danone Open Science Research Center for Life-Transforming Nutrition, Shanghai 200135, China
| | - Jiangyi Mao
- Danone Open Science Research Center for Life-Transforming Nutrition, Shanghai 200135, China
| | - Wei Wei
- School of Food Science and Technology, Jiangnan University, Wuxi 214126, China
| | - Chenyu Jiang
- School of Food Science and Technology, Jiangnan University, Wuxi 214126, China
| | - Lina Zhang
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214126, China
- School of Food Science and Technology, Jiangnan University, Wuxi 214126, China
| | - Yi Wang
- Danone Open Science Research Center for Life-Transforming Nutrition, Shanghai 200135, China
| | - Peng Zhou
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214126, China
- School of Food Science and Technology, Jiangnan University, Wuxi 214126, China
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8
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Haggerty KN, Eshelman SC, Sexton LA, Frimpong E, Rogers LM, Agosto MA, Robichaux MA. Mapping rhodopsin trafficking in rod photoreceptors with quantitative super-resolution microscopy. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.20.537413. [PMID: 37131638 PMCID: PMC10153271 DOI: 10.1101/2023.04.20.537413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Photoreceptor cells in the vertebrate retina have a highly compartmentalized morphology for efficient long-term phototransduction. Rhodopsin, the visual pigment in rod photoreceptors, is densely packaged into the rod outer segment sensory cilium and continuously renewed through essential synthesis and trafficking pathways housed in the rod inner segment. Despite the importance of this region for rod health and maintenance, the subcellular organization of rhodopsin and its trafficking regulators in the mammalian rod inner segment remain undefined. We used super-resolution fluorescence microscopy with optimized retinal immunolabeling techniques to perform a single molecule localization analysis of rhodopsin in the inner segments of mouse rods. We found that a significant fraction of rhodopsin molecules was localized at the plasma membrane in an even distribution along the entire length of the inner segment, where markers of transport vesicles also colocalized. Thus, our results collectively establish a model of rhodopsin trafficking through the inner segment plasma membrane as an essential subcellular pathway in mouse rod photoreceptors.
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Affiliation(s)
- Kristen N. Haggerty
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, WV, 26506
| | - Shannon C. Eshelman
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, WV, 26506
| | - Lauren A. Sexton
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, WV, 26506
| | - Emmanuel Frimpong
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, WV, 26506
| | - Leah M. Rogers
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, WV, 26506
| | - Melina A. Agosto
- Retina and Optic Nerve Research Laboratory, Department of Physiology and Biophysics, and Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, NS, B3H 4R2, Canada
| | - Michael A. Robichaux
- Department of Ophthalmology & Visual Sciences and Department of Biochemistry & Molecular Medicine, West Virginia University, Morgantown, WV, 26506
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9
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Gkikas I, Daskalaki I, Kounakis K, Tavernarakis N, Lionaki E. MitoSNARE Assembly and Disassembly Factors Regulate Basal Autophagy and Aging in C. elegans. Int J Mol Sci 2023; 24:ijms24044230. [PMID: 36835643 PMCID: PMC9964399 DOI: 10.3390/ijms24044230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 01/30/2023] [Accepted: 02/14/2023] [Indexed: 02/23/2023] Open
Abstract
SNARE proteins reside between opposing membranes and facilitate vesicle fusion, a physiological process ubiquitously required for secretion, endocytosis and autophagy. With age, neurosecretory SNARE activity drops and is pertinent to age-associated neurological disorders. Despite the importance of SNARE complex assembly and disassembly in membrane fusion, their diverse localization hinders the complete understanding of their function. Here, we revealed a subset of SNARE proteins, the syntaxin SYX-17, the synaptobrevins VAMP-7, SNB-6 and the tethering factor USO-1, to be either localized or in close proximity to mitochondria, in vivo. We term them mitoSNAREs and show that animals deficient in mitoSNAREs exhibit increased mitochondria mass and accumulation of autophagosomes. The SNARE disassembly factor NSF-1 seems to be required for the effects of mitoSNARE depletion. Moreover, we find mitoSNAREs to be indispensable for normal aging in both neuronal and non-neuronal tissues. Overall, we uncover a previously unrecognized subset of SNAREs that localize to mitochondria and propose a role of mitoSNARE assembly and disassembly factors in basal autophagy regulation and aging.
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Affiliation(s)
- Ilias Gkikas
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, 70013 Heraklion, Crete, Greece
- Department of Biology, School of Sciences and Engineering, University of Crete, 71110 Heraklion, Crete, Greece
| | - Ioanna Daskalaki
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, 70013 Heraklion, Crete, Greece
- Department of Biology, School of Sciences and Engineering, University of Crete, 71110 Heraklion, Crete, Greece
| | - Konstantinos Kounakis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, 70013 Heraklion, Crete, Greece
- Department of Basic Sciences, Faculty of Medicine, University of Crete, 71110 Heraklion, Crete, Greece
| | - Nektarios Tavernarakis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, 70013 Heraklion, Crete, Greece
- Department of Basic Sciences, Faculty of Medicine, University of Crete, 71110 Heraklion, Crete, Greece
- Correspondence: (N.T.); (E.L.)
| | - Eirini Lionaki
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, 70013 Heraklion, Crete, Greece
- Correspondence: (N.T.); (E.L.)
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10
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The genetics of monogenic intestinal epithelial disorders. Hum Genet 2022; 142:613-654. [PMID: 36422736 PMCID: PMC10182130 DOI: 10.1007/s00439-022-02501-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2022] [Accepted: 10/23/2022] [Indexed: 11/27/2022]
Abstract
Monogenic intestinal epithelial disorders, also known as congenital diarrheas and enteropathies (CoDEs), are a group of rare diseases that result from mutations in genes that primarily affect intestinal epithelial cell function. Patients with CoDE disorders generally present with infantile-onset diarrhea and poor growth, and often require intensive fluid and nutritional management. CoDE disorders can be classified into several categories that relate to broad areas of epithelial function, structure, and development. The advent of accessible and low-cost genetic sequencing has accelerated discovery in the field with over 45 different genes now associated with CoDE disorders. Despite this increasing knowledge in the causal genetics of disease, the underlying cellular pathophysiology remains incompletely understood for many disorders. Consequently, clinical management options for CoDE disorders are currently limited and there is an urgent need for new and disorder-specific therapies. In this review, we provide a general overview of CoDE disorders, including a historical perspective of the field and relationship to other monogenic disorders of the intestine. We describe the genetics, clinical presentation, and known pathophysiology for specific disorders. Lastly, we describe the major challenges relating to CoDE disorders, briefly outline key areas that need further study, and provide a perspective on the future genetic and therapeutic landscape.
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11
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Caenorhabditis elegans sine oculis/SIX-type homeobox genes act as homeotic switches to define neuronal subtype identities. Proc Natl Acad Sci U S A 2022; 119:e2206817119. [PMID: 36067313 PMCID: PMC9478639 DOI: 10.1073/pnas.2206817119] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Anatomical and molecular studies have revealed that in many animal nervous systems, neuronal cell types can often be subclassified into highly related subtypes with only small phenotypic differences. We decipher here the regulatory logic of such cell type diversification processes. We show that identity features of neurons that are highly similar to one another are controlled by master regulatory transcription factors and that phenotypic differences between related cell types are controlled by downstream acting transcription factors that promote or antagonize the ability of master regulatory factors to control unique identity features. Our findings help explain how neuronal cell types diversify and suggest hypothetical scenarios for neuronal cell-type evolution. The classification of neurons into distinct types reveals hierarchical taxonomic relationships that reflect the extent of similarity between neuronal cell types. At the base of such taxonomies are neuronal cells that are very similar to one another but differ in a small number of reproducible and select features. How are very similar members of a neuron class that share many features instructed to diversify into distinct subclasses? We show here that the six very similar members of the Caenorhabditis elegans IL2 sensory neuron class, which are all specified by a homeobox terminal selector, unc-86/BRN3, differentiate into two subtly distinct subclasses, a dorsoventral subclass and a lateral subclass, by the toggle switch–like action of the sine oculis/SIX homeobox gene unc-39. unc-39 is expressed only in the lateral IL2 neurons, and loss of unc-39 leads to a homeotic transformation of the lateral into the dorsoventral class; conversely, ectopic unc-39 expression converts the dorsoventral subclass into the lateral subclass. Hence, a terminal selector homeobox gene controls both class- as well as subclass-specific features, while a subordinate homeobox gene determines the ability of the class-specific homeobox gene to activate subtype-specific target genes. We find a similar regulatory mechanism operating in a distinct class of six motor neurons. Our findings underscore the importance of homeobox genes in neuronal identity control and invite speculations about homeotic identity transformations as potential drivers of evolutionary novelty during cell-type evolution in the brain.
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12
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Dutta P, Ray K. Ciliary membrane, localised lipid modification and cilia function. J Cell Physiol 2022; 237:2613-2631. [PMID: 35661356 DOI: 10.1002/jcp.30787] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Revised: 05/06/2022] [Accepted: 05/11/2022] [Indexed: 11/08/2022]
Abstract
Cilium, a tiny microtubule-based cellular appendage critical for cell signalling and physiology, displays a large variety of receptors. The composition and turnover of ciliary lipids and receptors determine cell behaviour. Due to the exclusion of ribosomal machinery and limited membrane area, a cilium needs adaptive logistics to actively reconstitute the lipid and receptor compositions during development and differentiation. How is this dynamicity generated? Here, we examine whether, along with the Intraflagellar-Transport, targeted changes in sector-wise lipid composition could control the receptor localisation and functions in the cilia. We discuss how an interplay between ciliary lipid composition, localised lipid modification, and receptor function could contribute to cilia growth and signalling. We argue that lipid modification at the cell-cilium interface could generate an added thrust for a selective exchange of membrane lipids and the transmembrane and membrane-associated proteins.
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Affiliation(s)
- Priya Dutta
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, India
| | - Krishanu Ray
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, India
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13
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Rivera-Molina FE, Xi Z, Reales E, Wang B, Toomre D. Exocyst complex mediates recycling of internal cilia. Curr Biol 2021; 31:5580-5589.e5. [PMID: 34678163 DOI: 10.1016/j.cub.2021.09.067] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 07/22/2021] [Accepted: 09/23/2021] [Indexed: 12/23/2022]
Abstract
Primary cilia are slender, cellular antennae that sense extracellular stimuli, and their absence or dysfunction plays a role in numerous human diseases. Prior work has indicated a role of the exocyst tethering complex in cilia biogenesis and maintenance,1-6 with the underlying paradigm that the exocyst targets vesicles to the ciliary base to deliver ciliary cargoes.7-9 However, the role of the exocyst vis-à-vis to primary cilia in living cells and during stimulation is unknown. Herein, using advanced imaging and quantitative analysis reveals that serum stimulation increases the exocyst's localization to cilia by three-fold. This serum-stimulated localization is highly dynamic, and FRAP experiments show that exocysts at the cilia are highly mobile (60%-80%). Super resolution imaging reveals that the xocyst extends past the cilia base to the entire ciliary pocket. To visualize cilia exocytosis, we conducted live cell imaging with pH-sensitive cilia reporters in combination with extracellular pH switching. Strikingly, we observed that an exocyst-positive internal cilia fuses with the cell surface. These live cell results support a novel and dynamic role of the exocyst complex in the delivery of internalized cilia to the cell surface. Moreover, they suggest a novel pathway may be used to recycle primary cilia to the cell surface that engages the exocyst in response to stimuli. This new remarkable plasticity in cilia presence on the surface in response to extracellular stimuli suggest new means to potentially modulate cilia signaling.
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Affiliation(s)
- Félix E Rivera-Molina
- Department of Cell Biology, School of Medicine, Yale University, 333 Cedar St., New Haven, CT 06520, USA.
| | - Zhiqun Xi
- Department of Cell Biology, School of Medicine, Yale University, 333 Cedar St., New Haven, CT 06520, USA
| | - Elena Reales
- Department of Regeneration and Cell Therapy, Andalusian Molecular Biology and Regenerative Medicine Centre (CABIMER), Seville, Spain
| | - Bryan Wang
- Department of Cell Biology, School of Medicine, Yale University, 333 Cedar St., New Haven, CT 06520, USA
| | - Derek Toomre
- Department of Cell Biology, School of Medicine, Yale University, 333 Cedar St., New Haven, CT 06520, USA.
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14
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Ruiz-Pastor MJ, Kutsyr O, Lax P, Cuenca N. Decrease in DHA and other fatty acids correlates with photoreceptor degeneration in retinitis pigmentosa. Exp Eye Res 2021; 209:108667. [PMID: 34119484 DOI: 10.1016/j.exer.2021.108667] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 05/21/2021] [Accepted: 06/07/2021] [Indexed: 10/21/2022]
Abstract
Fatty acids, and especially docosahexaenoic acid (DHA), are essential for photoreceptor cell integrity and are involved in the phototransduction cascade. In this study, we analyzed the changes in the fatty acid profile in the retina of the rd10 mouse, model of retinitis pigmentosa, in order to identify potential risk factors for retinal degeneration and possible therapeutic approaches. Fatty acids from C57BL/6J and rd10 mouse retinas were extracted with Folch's method and analyzed by gas chromatography/mass spectrometry. Changes in retinal morphology were evaluated by immunohistochemistry. The rd10 mouse retina showed a decreased number of photoreceptor rows and alterations in photoreceptor morphology compared to C57BL/6J mice. The total amount of fatty acids dropped by 29.4% in the dystrophic retinas compared to C57BL/6J retinas. A positive correlation was found between the retinal content of specific fatty acids and the number of photoreceptor rows. We found that the amount of several short-chain and long-chain saturated fatty acids, as well as monounsaturated fatty acids, decreased in the retina of rd10 mice. Moreover, the content of the n-6 polyunsaturated fatty acid arachidonic acid and the n-3 polyunsaturated DHA decreased markedly in the dystrophic retina. The fall of DHA was more pronounced, hence the n-6/n-3 ratio was significantly increased in the diseased retina. The content of specific fatty acids in the retina decreased with photoreceptor degeneration in retinitis pigmentosa mice, with a remarkable reduction in DHA and other saturated and unsaturated fatty acids. These fatty acids could be essential for photoreceptor cell viability, and they should be evaluated for the design of therapeutical strategies and nutritional supplements.
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Affiliation(s)
- María José Ruiz-Pastor
- Department of Physiology, Genetics, and Microbiology, University of Alicante, Alicante, Spain
| | - Oksana Kutsyr
- Department of Physiology, Genetics, and Microbiology, University of Alicante, Alicante, Spain
| | - Pedro Lax
- Department of Physiology, Genetics, and Microbiology, University of Alicante, Alicante, Spain.
| | - Nicolás Cuenca
- Department of Physiology, Genetics, and Microbiology, University of Alicante, Alicante, Spain.
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15
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Janecke AR, Liu X, Adam R, Punuru S, Viestenz A, Strauß V, Laass M, Sanchez E, Adachi R, Schatz MP, Saboo US, Mittal N, Rohrschneider K, Escher J, Ganesh A, Al Zuhaibi S, Al Murshedi F, AlSaleem B, Alfadhel M, Al Sinani S, Alkuraya FS, Huber LA, Müller T, Heidelberger R, Janz R. Pathogenic STX3 variants affecting the retinal and intestinal transcripts cause an early-onset severe retinal dystrophy in microvillus inclusion disease subjects. Hum Genet 2021; 140:1143-1156. [PMID: 33974130 PMCID: PMC8263458 DOI: 10.1007/s00439-021-02284-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Accepted: 04/15/2021] [Indexed: 01/12/2023]
Abstract
Biallelic STX3 variants were previously reported in five individuals with the severe congenital enteropathy, microvillus inclusion disease (MVID). Here, we provide a significant extension of the phenotypic spectrum caused by STX3 variants. We report ten individuals of diverse geographic origin with biallelic STX3 loss-of-function variants, identified through exome sequencing, single-nucleotide polymorphism array-based homozygosity mapping, and international collaboration. The evaluated individuals all presented with MVID. Eight individuals also displayed early-onset severe retinal dystrophy, i.e., syndromic-intestinal and retinal-disease. These individuals harbored STX3 variants that affected both the retinal and intestinal STX3 transcripts, whereas STX3 variants affected only the intestinal transcript in individuals with solitary MVID. That STX3 is essential for retinal photoreceptor survival was confirmed by the creation of a rod photoreceptor-specific STX3 knockout mouse model which revealed a time-dependent reduction in the number of rod photoreceptors, thinning of the outer nuclear layer, and the eventual loss of both rod and cone photoreceptors. Together, our results provide a link between STX3 loss-of-function variants and a human retinal dystrophy. Depending on the genomic site of a human loss-of-function STX3 variant, it can cause MVID, the novel intestinal-retinal syndrome reported here or, hypothetically, an isolated retinal dystrophy.
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Affiliation(s)
- Andreas R Janecke
- Department of Pediatrics I, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
- Division of Human Genetics, Medical University of Innsbruck, Innsbruck, Austria.
| | - Xiaoqin Liu
- Department of Neurobiology and Anatomy, MSB 7.046, McGovern Medical School at the University of Texas HSC (UTHealth), 6431 Fannin Street, Houston, TX, 77030, USA
| | - Rüdiger Adam
- University Children's Hospital, Medical Faculty Mannheim, Heidelberg University, 68167 Mannheim, Germany
| | - Sumanth Punuru
- Department of Neurobiology and Anatomy, MSB 7.046, McGovern Medical School at the University of Texas HSC (UTHealth), 6431 Fannin Street, Houston, TX, 77030, USA
| | - Arne Viestenz
- Department of Ophthalmology, University Medical Center Halle, Martin-Luther-University Halle-Wittenberg, Halle, Germany
| | - Valeria Strauß
- Klinik für Kinder- und Jugendmedizin, Universitätsklinikum Halle, Halle, Germany
| | - Martin Laass
- Klinik und Poliklinik f. Kinder- u. Jugendmedizin, University of Dresden, Dresden, Germany
| | - Elizabeth Sanchez
- Department of Pulmonary Medicine, Division of Internal Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Roberto Adachi
- Department of Pulmonary Medicine, Division of Internal Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Martha P Schatz
- Department of Ophthalmology, University of Texas Health Science Center, San Antonio, TX, USA
| | - Ujwala S Saboo
- Department of Ophthalmology, University of Texas Health Science Center, San Antonio, TX, USA
| | - Naveen Mittal
- Department of Department of Pediatrics, Division of Pediatric Gastroenterology, University of Texas Health Science Center, San Antonio, TX, USA
| | | | - Johanna Escher
- Erasmus MC-Sophia Children's Hospital, Rotterdam, The Netherlands
| | - Anuradha Ganesh
- Department of Ophthalmology, Sultan Qaboos University Hospital, Muscat, Oman
| | - Sana Al Zuhaibi
- Department of Ophthalmology, Sultan Qaboos University Hospital, Muscat, Oman
| | - Fathiya Al Murshedi
- Genetic and Developmental Medicine Clinic, Sultan Qaboos University Hospital, Muscat, Oman
| | - Badr AlSaleem
- King Fahad Medical City, Children's Specialized Hospital, Riyadh, Saudi Arabia
| | - Majid Alfadhel
- Genetics Division and Medical Genomic Research Lab, King Saud Bin Abdulaziz University for Health Sciences (KSAU-HS), Riyadh, Saudi Arabia
| | - Siham Al Sinani
- Department of Child Health, Sultan Qaboos University Hospital, Muscat, Oman
| | - Fowzan S Alkuraya
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - Lukas A Huber
- Division of Cell Biology, Medical University of Innsbruck, Innsbruck, Austria
| | - Thomas Müller
- Department of Pediatrics I, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria
| | - Ruth Heidelberger
- Department of Neurobiology and Anatomy, MSB 7.046, McGovern Medical School at the University of Texas HSC (UTHealth), 6431 Fannin Street, Houston, TX, 77030, USA.
| | - Roger Janz
- Department of Neurobiology and Anatomy, MSB 7.046, McGovern Medical School at the University of Texas HSC (UTHealth), 6431 Fannin Street, Houston, TX, 77030, USA
- Center for Scientific Review, National Institutes of Health, Bethesda, MD, USA
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16
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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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17
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Sánchez-Bellver L, Toulis V, Marfany G. On the Wrong Track: Alterations of Ciliary Transport in Inherited Retinal Dystrophies. Front Cell Dev Biol 2021; 9:623734. [PMID: 33748110 PMCID: PMC7973215 DOI: 10.3389/fcell.2021.623734] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 02/09/2021] [Indexed: 01/14/2023] Open
Abstract
Ciliopathies are a group of heterogeneous inherited disorders associated with dysfunction of the cilium, a ubiquitous microtubule-based organelle involved in a broad range of cellular functions. Most ciliopathies are syndromic, since several organs whose cells produce a cilium, such as the retina, cochlea or kidney, are affected by mutations in ciliary-related genes. In the retina, photoreceptor cells present a highly specialized neurosensory cilium, the outer segment, stacked with membranous disks where photoreception and phototransduction occurs. The daily renewal of the more distal disks is a unique characteristic of photoreceptor outer segments, resulting in an elevated protein demand. All components necessary for outer segment formation, maintenance and function have to be transported from the photoreceptor inner segment, where synthesis occurs, to the cilium. Therefore, efficient transport of selected proteins is critical for photoreceptor ciliogenesis and function, and any alteration in either cargo delivery to the cilium or intraciliary trafficking compromises photoreceptor survival and leads to retinal degeneration. To date, mutations in more than 100 ciliary genes have been associated with retinal dystrophies, accounting for almost 25% of these inherited rare diseases. Interestingly, not all mutations in ciliary genes that cause retinal degeneration are also involved in pleiotropic pathologies in other ciliated organs. Depending on the mutation, the same gene can cause syndromic or non-syndromic retinopathies, thus emphasizing the highly refined specialization of the photoreceptor neurosensory cilia, and raising the possibility of photoreceptor-specific molecular mechanisms underlying common ciliary functions such as ciliary transport. In this review, we will focus on ciliary transport in photoreceptor cells and discuss the molecular complexity underpinning retinal ciliopathies, with a special emphasis on ciliary genes that, when mutated, cause either syndromic or non-syndromic retinal ciliopathies.
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Affiliation(s)
- Laura Sánchez-Bellver
- Departament de Genètica, Microbiologia i Estadística, Universitat de Barcelona, Barcelona, Spain
- Institute of Biomedicine (IBUB-IRSJD), Universitat de Barcelona, Barcelona, Spain
| | - Vasileios Toulis
- Departament de Genètica, Microbiologia i Estadística, Universitat de Barcelona, Barcelona, Spain
- CIBERER, ISCIII, Universitat de Barcelona, Barcelona, Spain
| | - Gemma Marfany
- Departament de Genètica, Microbiologia i Estadística, Universitat de Barcelona, Barcelona, Spain
- Institute of Biomedicine (IBUB-IRSJD), Universitat de Barcelona, Barcelona, Spain
- CIBERER, ISCIII, Universitat de Barcelona, Barcelona, Spain
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18
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Syntaxin 3 is essential for photoreceptor outer segment protein trafficking and survival. Proc Natl Acad Sci U S A 2020; 117:20615-20624. [PMID: 32778589 DOI: 10.1073/pnas.2010751117] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Trafficking of photoreceptor membrane proteins from their site of synthesis in the inner segment (IS) to the outer segment (OS) is critical for photoreceptor function and vision. Here we evaluate the role of syntaxin 3 (STX3), in trafficking of OS membrane proteins such as peripherin 2 (PRPH2) and rhodopsin. Photoreceptor-specific Stx3 knockouts [Stx3 f/f(iCre75) and Stx3 f/f(CRX-Cre) ] exhibited rapid, early-onset photoreceptor degeneration and functional decline characterized by structural defects in IS, OS, and synaptic terminals. Critically, in the absence of STX3, OS proteins such as PRPH2, the PRPH2 binding partner, rod outer segment membrane protein 1 (ROM1), and rhodopsin were mislocalized along the microtubules to the IS, cell body, and synaptic region. We find that the PRPH2 C-terminal domain interacts with STX3 as well as other photoreceptor SNAREs, and our findings indicate that STX3 is an essential part of the trafficking pathway for both disc (rhodopsin) and rim (PRPH2/ROM1) components of the OS.
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19
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Long H, Huang K. Transport of Ciliary Membrane Proteins. Front Cell Dev Biol 2020; 7:381. [PMID: 31998723 PMCID: PMC6970386 DOI: 10.3389/fcell.2019.00381] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Accepted: 12/17/2019] [Indexed: 12/24/2022] Open
Abstract
Cilia and flagella are highly conserved organelles in eukaryotic cells that drive cell movement and act as cell antennae that receive and transmit signals. In addition to receiving and transducing external signals that activate signal cascades, cilia also secrete ciliary ectosomes that send signals to recipient cells, and thereby mediate cell–cell communication. Abnormal ciliary function leads to various ciliopathies, and the precise transport and localization of ciliary membrane proteins are essential for cilium function. This review summarizes current knowledge about the transport processes of ciliary membrane proteins after their synthesis at the endoplasmic reticulum: modification and sorting in the Golgi apparatus, transport through vesicles to the ciliary base, entrance into cilia through the diffusion barrier, and turnover by ectosome secretion. The molecular mechanisms and regulation involved in each step are also discussed. Transport of ciliary membrane proteins is a complex, precise cellular process coordinated among multiple organelles. By systematically analyzing the existing research, we identify topics that should be further investigated to promote progress in this field of research.
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Affiliation(s)
- Huan Long
- Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China
| | - Kaiyao Huang
- Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China
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20
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Datta P, Hendrickson B, Brendalen S, Ruffcorn A, Seo S. The myosin-tail homology domain of centrosomal protein 290 is essential for protein confinement between the inner and outer segments in photoreceptors. J Biol Chem 2019; 294:19119-19136. [PMID: 31694913 DOI: 10.1074/jbc.ra119.009712] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 10/30/2019] [Indexed: 12/13/2022] Open
Abstract
Mutations in the centrosomal protein 290 (CEP290) gene cause various ciliopathies involving retinal degeneration. CEP290 proteins localize to the ciliary transition zone and are thought to act as a gatekeeper that controls ciliary protein trafficking. However, precise roles of CEP290 in photoreceptors and pathomechanisms of retinal degeneration in CEP290-associated ciliopathies are not sufficiently understood. Using conditional Cep290 mutant mice, in which the C-terminal myosin-tail homology domain of CEP290 is disrupted after the connecting cilium is assembled, we show that this domain is essential for protein confinement between the inner and the outer segments. Upon disruption of the myosin-tail homology domain, inner segment plasma membrane proteins, including syntaxin 3 (STX3), synaptosome-associated protein 25 (SNAP25), and interphotoreceptor matrix proteoglycan 2 (IMPG2), rapidly accumulated in the outer segment. In contrast, localization of endomembrane proteins was not altered. Trafficking and confinement of most outer segment-resident proteins appeared to be unaffected or only minimally affected in Cep290 mutant mice. One notable exception was rhodopsin (RHO), which severely mislocalized to inner segments during the initial stage of degeneration. Similar mislocalization phenotypes were observed in Cep290rd16 mice. These results suggest that a failure of protein confinement at the connecting cilium and consequent accumulation of inner segment membrane proteins in the outer segment, along with insufficient RHO delivery, is part of the disease mechanisms that cause retinal degeneration in CEP290-associated ciliopathies. Our study provides insights into the pathomechanisms of retinal degenerations associated with compromised ciliary gates.
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Affiliation(s)
- Poppy Datta
- Department of Ophthalmology and Visual Sciences, University of Iowa College of Medicine, Iowa City, Iowa 52242.,Institute for Vision Research, University of Iowa, Iowa City, Iowa 52242
| | - Brandon Hendrickson
- Department of Ophthalmology and Visual Sciences, University of Iowa College of Medicine, Iowa City, Iowa 52242.,Institute for Vision Research, University of Iowa, Iowa City, Iowa 52242
| | - Sarah Brendalen
- Department of Ophthalmology and Visual Sciences, University of Iowa College of Medicine, Iowa City, Iowa 52242.,Institute for Vision Research, University of Iowa, Iowa City, Iowa 52242
| | - Avri Ruffcorn
- Department of Ophthalmology and Visual Sciences, University of Iowa College of Medicine, Iowa City, Iowa 52242.,Institute for Vision Research, University of Iowa, Iowa City, Iowa 52242
| | - Seongjin Seo
- Department of Ophthalmology and Visual Sciences, University of Iowa College of Medicine, Iowa City, Iowa 52242 .,Institute for Vision Research, University of Iowa, Iowa City, Iowa 52242
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21
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Abstract
Rods and cones are retinal photoreceptor neurons required for our visual sensation. Because of their highly polarized structures and well-characterized processes of G protein-coupled receptor-mediated phototransduction signaling, these photoreceptors have been excellent models for studying the compartmentalization and sorting of proteins. Rods and cones have a modified ciliary compartment called the outer segment (OS) as well as non-OS compartments. The distinct membrane protein compositions between OS and non-OS compartments suggest that the OS is separated from the rest of the cellular compartments by multiple barriers or gates that are selectively permissive to specific cargoes. This review discusses the mechanisms of protein sorting and compartmentalization in photoreceptor neurons. Proper sorting and compartmentalization of membrane proteins are required for signal transduction and transmission. This review also discusses the roles of compartmentalized signaling, which is compromised in various retinal ciliopathies.
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Affiliation(s)
- Yoshikazu Imanishi
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA;
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22
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The photoreceptor cilium and its diseases. Curr Opin Genet Dev 2019; 56:22-33. [DOI: 10.1016/j.gde.2019.05.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Revised: 04/21/2019] [Accepted: 05/11/2019] [Indexed: 12/26/2022]
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23
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Deretic D, Lorentzen E, Fresquez T. The ins and outs of the Arf4-based ciliary membrane-targeting complex. Small GTPases 2019; 12:1-12. [PMID: 31068062 DOI: 10.1080/21541248.2019.1616355] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
The small GTPase Arf4-based ciliary membrane-targeting complex recognizes specific targeting signals within sensory receptors and regulates their directed movement to primary cilia. Activated Arf4 directly binds the VxPx ciliary-targeting signal (CTS) of the light-sensing receptor rhodopsin. Recent findings revealed that at the trans-Golgi, marked by the small GTPase Rab6, activated Arf4 forms a functional complex with rhodopsin and the Arf guanine nucleotide exchange factor (GEF) GBF1, providing positive feedback that drives further Arf4 activation in ciliary trafficking. Arf4 function is conserved across diverse cell types; however, it appears that not all its aspects are conserved across species, as mouse Arf4 is a natural mutant in the conserved α3 helix, which is essential for its interaction with rhodopsin. Generally, activated Arf4 regulates the assembly of the targeting nexus containing the Arf GAP ASAP1 and the Rab11a-FIP3-Rabin8 dual effector complex, which controls the assembly of the highly conserved Rab11a-Rabin8-Rab8 ciliary-targeting module. It was recently found that this module interacts with the R-SNARE VAMP7, likely in its activated, c-Src-phosphorylated form. Rab11 and Rab8 bind VAMP7 regulatory longin domain (LD), whereas Rabin8 interacts with the SNARE domain, capturing VAMP7 for delivery to the ciliary base and subsequent pairing with the cognate SNAREs syntaxin 3 and SNAP-25. This review will focus on the implications of these novel findings that further illuminate the role of well-ordered Arf and Rab interaction networks in targeting of sensory receptors to primary cilia. Abbreviations: CTS: Ciliary-Targeting Signal; GAP: GTPase Activating Protein; GEF: Guanine Nucleotide Exchange Factor; RTC(s), Rhodopsin Transport Carrier(s); SNARE: Soluble N-ethylmaleimide-sensitive Factor Attachment Protein Receptor; TGN: Trans-Golgi Network.
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Affiliation(s)
- Dusanka Deretic
- Departments of Surgery, Division of Ophthalmology, University of New Mexico , Albuquerque, NM, USA.,Cell Biology and Physiology, University of New Mexico , Albuquerque, NM, USA
| | - Esben Lorentzen
- Department of Molecular Biology and Genetics, Aarhus University , Aarhus, Denmark
| | - Theresa Fresquez
- Departments of Surgery, Division of Ophthalmology, University of New Mexico , Albuquerque, NM, USA
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24
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Kandachar V, Tam BM, Moritz OL, Deretic D. An interaction network between the SNARE VAMP7 and Rab GTPases within a ciliary membrane-targeting complex. J Cell Sci 2018; 131:jcs.222034. [PMID: 30404838 DOI: 10.1242/jcs.222034] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Accepted: 10/30/2018] [Indexed: 12/16/2022] Open
Abstract
The Arf4-rhodopsin complex (mediated by the VxPx motif in rhodopsin) initiates expansion of vertebrate rod photoreceptor cilia-derived light-sensing organelles through stepwise assembly of a conserved trafficking network. Here, we examine its role in the sorting of VAMP7 (also known as TI-VAMP) - an R-SNARE possessing a regulatory longin domain (LD) - into rhodopsin transport carriers (RTCs). During RTC formation and trafficking, VAMP7 colocalizes with the ciliary cargo rhodopsin and interacts with the Rab11-Rabin8-Rab8 trafficking module. Rab11 and Rab8 bind the VAMP7 LD, whereas Rabin8 (also known as RAB3IP) interacts with the SNARE domain. The Arf/Rab11 effector FIP3 (also known as RAB11FIP3) regulates VAMP7 access to Rab11. At the ciliary base, VAMP7 forms a complex with the cognate SNAREs syntaxin 3 and SNAP-25. When expressed in transgenic animals, a GFP-VAMP7ΔLD fusion protein and a Y45E phosphomimetic mutant colocalize with endogenous VAMP7. The GFP-VAMP7-R150E mutant displays considerable localization defects that imply an important role of the R-SNARE motif in intracellular trafficking, rather than cognate SNARE pairing. Our study defines the link between VAMP7 and the ciliary targeting nexus that is conserved across diverse cell types, and contributes to general understanding of how functional Arf and Rab networks assemble SNAREs in membrane trafficking.
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Affiliation(s)
- Vasundhara Kandachar
- Department of Surgery, Division of Ophthalmology, University of New Mexico, Albuquerque, NM 87131, USA
| | - Beatrice M Tam
- Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, BC V5Z 3N9, Canada
| | - Orson L Moritz
- Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, BC V5Z 3N9, Canada
| | - Dusanka Deretic
- Department of Surgery, Division of Ophthalmology, University of New Mexico, Albuquerque, NM 87131, USA .,Cell Biology and Physiology, University of New Mexico, Albuquerque, NM 87131, USA
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25
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Lu L, Madugula V. Mechanisms of ciliary targeting: entering importins and Rabs. Cell Mol Life Sci 2018; 75:597-606. [PMID: 28852774 PMCID: PMC11105572 DOI: 10.1007/s00018-017-2629-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Revised: 08/11/2017] [Accepted: 08/16/2017] [Indexed: 12/29/2022]
Abstract
Primary cilium is a rod-like plasma membrane protrusion that plays important roles in sensing the cellular environment and initiating corresponding signaling pathways. The sensory functions of the cilium critically depend on the unique enrichment of ciliary residents, which is maintained by the ciliary diffusion barrier. It is still unclear how ciliary cargoes specifically enter the diffusion barrier and accumulate within the cilium. In this review, the organization and trafficking mechanism of the cilium are compared to those of the nucleus, which are much better understood at the moment. Though the cilium differs significantly from the nucleus in terms of molecular and cellular functions, analogous themes and principles in the membrane organization and cargo trafficking are notable between them. Therefore, knowledge in the nuclear trafficking can likely shed light on our understanding of the ciliary trafficking. Here, with a focus on membrane cargoes in mammalian cells, we briefly review various ciliary trafficking pathways from the Golgi to the periciliary membrane. Models for the subsequent import translocation across the diffusion barrier and the enrichment of cargoes within the ciliary membrane are discussed in detail. Based on recent discoveries, we propose a Rab-importin-based model in an attempt to accommodate various observations on ciliary targeting.
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Affiliation(s)
- Lei Lu
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore.
| | - Viswanadh Madugula
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore
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Apodaca G. Role of Polarity Proteins in the Generation and Organization of Apical Surface Protrusions. Cold Spring Harb Perspect Biol 2018; 10:cshperspect.a027813. [PMID: 28264821 DOI: 10.1101/cshperspect.a027813] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Protruding from the apical surfaces of epithelial cells are specialized structures, including cilia, microplicae, microvilli, and stereocilia. These contribute to epithelial function by cushioning the apical surface, by amplifying its surface area to facilitate nutrient absorption, and by promoting sensory transduction and barrier function. Despite these important roles, and the diseases that result when their formation is perturbed, there remain significant gaps in our understanding of the biogenesis of apical protrusions, or the pathways that promote their organization and orientation once at the apical surface. Here, I review some general aspects of these apical structures, and then discuss our current understanding of their formation and organization with respect to proteins that specify apicobasolateral polarity and planar cell polarity.
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Affiliation(s)
- Gerard Apodaca
- Department of Medicine Renal-Electrolyte Division and the Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
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Close WL, Anderson AN, Pellett PE. Betaherpesvirus Virion Assembly and Egress. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1045:167-207. [PMID: 29896668 DOI: 10.1007/978-981-10-7230-7_9] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Virions are the vehicle for cell-to-cell and host-to-host transmission of viruses. Virions need to be assembled reliably and efficiently, be released from infected cells, survive in the extracellular environment during transmission, recognize and then trigger entry of appropriate target cells, and disassemble in an orderly manner during initiation of a new infection. The betaherpesvirus subfamily includes four human herpesviruses (human cytomegalovirus and human herpesviruses 6A, 6B, and 7), as well as viruses that are the basis of important animal models of infection and immunity. Similar to other herpesviruses, betaherpesvirus virions consist of four main parts (in order from the inside): the genome, capsid, tegument, and envelope. Betaherpesvirus genomes are dsDNA and range in length from ~145 to 240 kb. Virion capsids (or nucleocapsids) are geometrically well-defined vessels that contain one copy of the dsDNA viral genome. The tegument is a collection of several thousand protein and RNA molecules packed into the space between the envelope and the capsid for delivery and immediate activity upon cellular entry at the initiation of an infection. Betaherpesvirus envelopes consist of lipid bilayers studded with virus-encoded glycoproteins; they protect the virion during transmission and mediate virion entry during initiation of new infections. Here, we summarize the mechanisms of betaherpesvirus virion assembly, including how infection modifies, reprograms, hijacks, and otherwise manipulates cellular processes and pathways to produce virion components, assemble the parts into infectious virions, and then transport the nascent virions to the extracellular environment for transmission.
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Affiliation(s)
- William L Close
- Department of Microbiology & Immunology, University of Michigan School of Medicine, Ann Arbor, MI, USA
- Department of Biochemistry, Microbiology, & Immunology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Ashley N Anderson
- Department of Biochemistry, Microbiology, & Immunology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Philip E Pellett
- Department of Biochemistry, Microbiology, & Immunology, Wayne State University School of Medicine, Detroit, MI, USA.
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Ojeda Naharros I, Gesemann M, Mateos JM, Barmettler G, Forbes A, Ziegler U, Neuhauss SCF, Bachmann-Gagescu R. Loss-of-function of the ciliopathy protein Cc2d2a disorganizes the vesicle fusion machinery at the periciliary membrane and indirectly affects Rab8-trafficking in zebrafish photoreceptors. PLoS Genet 2017; 13:e1007150. [PMID: 29281629 PMCID: PMC5760100 DOI: 10.1371/journal.pgen.1007150] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Revised: 01/09/2018] [Accepted: 12/11/2017] [Indexed: 12/22/2022] Open
Abstract
Ciliopathies are human disorders caused by dysfunction of primary cilia, ubiquitous organelles involved in transduction of environmental signals such as light sensation in photoreceptors. Concentration of signal detection proteins such as opsins in the ciliary membrane is achieved by RabGTPase-regulated polarized vesicle trafficking and by a selective barrier at the ciliary base, the transition zone (TZ). Dysfunction of the TZ protein CC2D2A causes Joubert/Meckel syndromes in humans and loss of ciliary protein localization in animal models, including opsins in retinal photoreceptors. The link between the TZ and upstream vesicle trafficking has been little explored to date. Moreover, the role of the small GTPase Rab8 in opsin-carrier vesicle (OCV) trafficking has been recently questioned in a mouse model. Using correlative light and electron microscopy and live imaging in zebrafish photoreceptors, we provide the first live characterization of Rab8-mediated trafficking in photoreceptors in vivo. Our results support a possibly redundant role for both Rab8a/b paralogs in OCV trafficking, based on co-localization of Rab8 and opsins in vesicular structures, and joint movement of Rab8-tagged particles with opsin. We further investigate the role of the TZ protein Cc2d2a in Rab8-mediated trafficking using cc2d2a zebrafish mutants and identify a requirement for Cc2d2a in the latest step of OCV trafficking, namely vesicle fusion. Progressive accumulation of opsin-containing vesicles in the apical portion of photoreceptors lacking Cc2d2a is caused by disorganization of the vesicle fusion machinery at the periciliary membrane with mislocalization and loss of the t-SNAREs SNAP25 and Syntaxin3 and of the exocyst component Exoc4. We further observe secondary defects on upstream Rab8-trafficking with cytoplasmic accumulation of Rab8. Taken together, our results support participation of Rab8 in OCV trafficking and identify a novel role for the TZ protein Cc2d2a in fusion of incoming ciliary-directed vesicles, through organization of the vesicle fusion machinery at the periciliary membrane. Ciliopathies are human disorders caused by dysfunction of primary cilia, ubiquitous organelles involved in transduction of environmental signals to the cells. Concentration and regulation of signal detection proteins in the ciliary membrane is therefore tightly regulated through polarized vesicle trafficking and through a selective barrier at the ciliary base called the transition zone (TZ). Dysfunction of TZ proteins leads to human ciliopathies and to aberrant localization of ciliary proteins in animal models. In this work, we use zebrafish retinal photoreceptors as a model to explore the relationship between the TZ and upstream vesicle trafficking. Relying on modern technologies such as correlative light and electron microscopy and live imaging of fluorescently-tagged proteins, we identify a role for the TZ protein CC2D2A in organizing the components required for vesicle fusion at the periciliary membrane. We also characterize the movement dynamics of vesicles carrying light-detection proteins (opsins) towards the ciliary compartment of photoreceptors in vivo and provide novel data in support of the recently questioned involvement of the small GTPase Rab8 in opsin-carrier vesicle trafficking in photoreceptors.
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Affiliation(s)
| | - Matthias Gesemann
- Institute of Molecular Life Sciences, University of Zurich, Zurich, Switzerland
| | - José M. Mateos
- Center for Microscopy and Image Analysis, University of Zurich, Zurich, Switzerland
| | - Gery Barmettler
- Center for Microscopy and Image Analysis, University of Zurich, Zurich, Switzerland
| | - Austin Forbes
- Fred Hutchison Cancer Research Center, Seattle, Washington, United States of America
| | - Urs Ziegler
- Center for Microscopy and Image Analysis, University of Zurich, Zurich, Switzerland
| | | | - Ruxandra Bachmann-Gagescu
- Institute of Molecular Life Sciences, University of Zurich, Zurich, Switzerland
- Institute of Medical Genetics, University of Zurich, Schlieren, Switzerland
- * E-mail:
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Aldiri I, Xu B, Wang L, Chen X, Hiler D, Griffiths L, Valentine M, Shirinifard A, Thiagarajan S, Sablauer A, Barabas ME, Zhang J, Johnson D, Frase S, Zhou X, Easton J, Zhang J, Mardis ER, Wilson RK, Downing JR, Dyer MA. The Dynamic Epigenetic Landscape of the Retina During Development, Reprogramming, and Tumorigenesis. Neuron 2017; 94:550-568.e10. [PMID: 28472656 PMCID: PMC5508517 DOI: 10.1016/j.neuron.2017.04.022] [Citation(s) in RCA: 169] [Impact Index Per Article: 24.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Revised: 02/15/2017] [Accepted: 04/14/2017] [Indexed: 12/21/2022]
Abstract
In the developing retina, multipotent neural progenitors undergo unidirectional differentiation in a precise spatiotemporal order. Here we profile the epigenetic and transcriptional changes that occur during retinogenesis in mice and humans. Although some progenitor genes and cell cycle genes were epigenetically silenced during retinogenesis, the most dramatic change was derepression of cell-type-specific differentiation programs. We identified developmental-stage-specific super-enhancers and showed that most epigenetic changes are conserved in humans and mice. To determine how the epigenome changes during tumorigenesis and reprogramming, we performed integrated epigenetic analysis of murine and human retinoblastomas and induced pluripotent stem cells (iPSCs) derived from murine rod photoreceptors. The retinoblastoma epigenome mapped to the developmental stage when retinal progenitors switch from neurogenic to terminal patterns of cell division. The epigenome of retinoblastomas was more similar to that of the normal retina than that of retina-derived iPSCs, and we identified retina-specific epigenetic memory.
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Affiliation(s)
- Issam Aldiri
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
| | - Beisi Xu
- Department of Computational Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
| | - Lu Wang
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
| | - Xiang Chen
- Department of Computational Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
| | - Daniel Hiler
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
| | - Lyra Griffiths
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
| | - Marc Valentine
- Cytogenetics Shared Resource, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
| | - Abbas Shirinifard
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
| | - Suresh Thiagarajan
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
| | - Andras Sablauer
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
| | - Marie-Elizabeth Barabas
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
| | - Jiakun Zhang
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
| | - Dianna Johnson
- Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA
| | - Sharon Frase
- Cell and Tissue Imaging Shared Resource, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
| | - Xin Zhou
- Department of Computational Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
| | - John Easton
- Department of Computational Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
| | - Jinghui Zhang
- Department of Computational Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
| | - Elaine R Mardis
- Department of Genetics, The Genome Institute, Washington University School of Medicine in St. Louis, St. Louis, Missouri 63108, USA; Department of Medicine, The Genome Institute, Washington University School of Medicine in St. Louis, St. Louis, Missouri 63108, USA
| | - Richard K Wilson
- Department of Genetics, The Genome Institute, Washington University School of Medicine in St. Louis, St. Louis, Missouri 63108, USA; Siteman Cancer Center, The Genome Institute, Washington University School of Medicine in St. Louis, St. Louis, Missouri 63108, USA
| | - James R Downing
- Department of Pathology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
| | - Michael A Dyer
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA; Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA; Howard Hughes Medical Institute, Chevy Chase, Maryland 20815, USA.
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Monis WJ, Faundez V, Pazour GJ. BLOC-1 is required for selective membrane protein trafficking from endosomes to primary cilia. J Cell Biol 2017; 216:2131-2150. [PMID: 28576874 PMCID: PMC5496619 DOI: 10.1083/jcb.201611138] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 03/24/2017] [Accepted: 05/03/2017] [Indexed: 11/30/2022] Open
Abstract
Monis et al. demonstrate that the BLOC-1 protein complex is required for trafficking polycystin-2, but not fibrocystin or smoothened, from endosomes to primary cilia. This is the first demonstration of a role for BLOC-1 in ciliary assembly and emphasizes the complexity of distinct ciliary membrane protein trafficking routes. Primary cilia perceive the extracellular environment through receptors localized in the ciliary membrane, but mechanisms directing specific proteins to this domain are poorly understood. To address this question, we knocked down proteins potentially important for ciliary membrane targeting and determined how this affects the ciliary trafficking of fibrocystin, polycystin-2, and smoothened. Our analysis showed that fibrocystin and polycystin-2 are dependent on IFT20, GMAP210, and the exocyst complex, while smoothened delivery is largely independent of these components. In addition, we found that polycystin-2, but not smoothened or fibrocystin, requires the biogenesis of lysosome-related organelles complex-1 (BLOC-1) for ciliary delivery. Consistent with the role of BLOC-1 in sorting from the endosome, we find that disrupting the recycling endosome reduces ciliary polycystin-2 and causes its accumulation in the recycling endosome. This is the first demonstration of a role for BLOC-1 in ciliary assembly and highlights the complexity of pathways taken to the cilium.
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Affiliation(s)
- William J Monis
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Victor Faundez
- Department of Cell Biology, Emory University, Atlanta, GA
| | - Gregory J Pazour
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA
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Bouaziz M, Bejaoui S, Rabeh I, Besbes R, El Cafsi M, Falcon J. Impact of temperature on sea bass, Dicentrarchus labrax , retina: Fatty acid composition, expression of rhodopsin and enzymes of lipid and melatonin metabolism. Exp Eye Res 2017; 159:87-97. [DOI: 10.1016/j.exer.2017.03.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Revised: 03/10/2017] [Accepted: 03/22/2017] [Indexed: 12/16/2022]
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A Presynaptic Group III mGluR Recruits Gβγ/SNARE Interactions to Inhibit Synaptic Transmission by Cone Photoreceptors in the Vertebrate Retina. J Neurosci 2017; 37:4618-4634. [PMID: 28363980 DOI: 10.1523/jneurosci.2948-16.2017] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Revised: 03/27/2017] [Accepted: 03/28/2017] [Indexed: 11/21/2022] Open
Abstract
G-protein βγ subunits (Gβγ) interact with presynaptic proteins and regulate neurotransmitter release downstream of Ca2+ influx. To accomplish their roles in sensory signaling, photoreceptor synapses use specialized presynaptic proteins that support neurotransmission at active zone structures known as ribbons. While several G-protein coupled receptors (GPCRs) influence synaptic transmission at ribbon synapses of cones and other retinal neurons, it is unknown whether Gβγ contributes to these effects. We tested whether activation of one particular GPCR, a metabotropic glutamate receptor (mGluR), can reduce cone synaptic transmission via Gβγ in tiger salamander retinas. In recordings from horizontal cells, we found that an mGluR agonist (L-AP4) reduced cone-driven light responses and mEPSC frequency. In paired recordings of cones and horizontal cells, L-AP4 slightly reduced cone ICa (∼10%) and caused a larger reduction in cone-driven EPSCs (∼30%). Proximity ligation assay revealed direct interactions between SNAP-25 and Gβγ subunits in retinal synaptic layers. Pretreatment with the SNAP-25 cleaving protease BoNT/A inhibited L-AP4 effects on synaptic transmission, as did introduction of a peptide derived from the SNAP-25 C terminus. Introducing Gβγ subunits directly into cones reduced EPSC amplitude. This effect was inhibited by BoNT/A, supporting a role for Gβγ/SNAP-25 interactions. However, the mGluR-dependent reduction in ICa was not mimicked by Gβγ, indicating that this effect was independent of Gβγ. The finding that synaptic transmission at cone ribbon synapses is regulated by Gβγ/SNAP-25 interactions indicates that these mechanisms are shared by conventional and ribbon-type synapses. Gβγ liberated from other photoreceptor GPCRs is also likely to regulate synaptic transmission.SIGNIFICANCE STATEMENT Dynamic regulation of synaptic transmission by presynaptic G-protein coupled receptors shapes information flow through neural circuits. At the first synapse in the visual system, presynaptic metabotropic glutamate receptors (mGluRs) regulate cone photoreceptor synaptic transmission, although the mechanisms and functional impact of this are unclear. We show that mGluRs regulate light response encoding across the cone synapse, accomplished in part by triggering G-protein βγ subunits (Gβγ) interactions with SNAP-25, a core component of the synaptic vesicle fusion machinery. In addition to revealing a role in visual processing, this provides the first demonstration that Gβγ/SNAP-25 interactions regulate synaptic function at a ribbon-type synapse, contributing to an emerging picture of the ubiquity of Gβγ/SNARE interactions in regulating synaptic transmission throughout the nervous system.
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Colin J, Gregory-Pauron L, Lanhers MC, Claudepierre T, Corbier C, Yen FT, Malaplate-Armand C, Oster T. Membrane raft domains and remodeling in aging brain. Biochimie 2016; 130:178-187. [DOI: 10.1016/j.biochi.2016.08.014] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Accepted: 08/31/2016] [Indexed: 12/21/2022]
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Abstract
Retinal photoreceptor cells contain a specialized outer segment (OS) compartment that functions in the capture of light and its conversion into electrical signals in a process known as phototransduction. In rods, photoisomerization of 11-cis to all-trans retinal within rhodopsin triggers a biochemical cascade culminating in the closure of cGMP-gated channels and hyperpolarization of the cell. Biochemical reactions return the cell to its 'dark state' and the visual cycle converts all-trans retinal back to 11-cis retinal for rhodopsin regeneration. OS are continuously renewed, with aged membrane removed at the distal end by phagocytosis and new membrane added at the proximal end through OS disk morphogenesis linked to protein trafficking. The molecular basis for disk morphogenesis remains to be defined in detail although several models have been proposed, and molecular mechanisms underlying protein trafficking are under active investigation. The aim of this Cell Science at a Glance article and the accompanying poster is to highlight our current understanding of photoreceptor structure, phototransduction, the visual cycle, OS renewal, protein trafficking and retinal degenerative diseases.
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Affiliation(s)
- Robert S Molday
- Department of Biochemistry and Molecular Biology, Centre for Macular Research, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3 Department of Ophthalmology and Visual Sciences, Centre for Macular Research, University of British Columbia, Vancouver, British Columbia, Canada V5Z 3N9
| | - Orson L Moritz
- Department of Ophthalmology and Visual Sciences, Centre for Macular Research, University of British Columbia, Vancouver, British Columbia, Canada V5Z 3N9
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Soo Hoo L, Banna CD, Radeke CM, Sharma N, Albertolle ME, Low SH, Weimbs T, Vandenberg CA. The SNARE Protein Syntaxin 3 Confers Specificity for Polarized Axonal Trafficking in Neurons. PLoS One 2016; 11:e0163671. [PMID: 27662481 PMCID: PMC5035089 DOI: 10.1371/journal.pone.0163671] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Accepted: 09/12/2016] [Indexed: 11/19/2022] Open
Abstract
Cell polarity and precise subcellular protein localization are pivotal to neuronal function. The SNARE machinery underlies intracellular membrane fusion events, but its role in neuronal polarity and selective protein targeting remain unclear. Here we report that syntaxin 3 is involved in orchestrating polarized trafficking in cultured rat hippocampal neurons. We show that syntaxin 3 localizes to the axonal plasma membrane, particularly to axonal tips, whereas syntaxin 4 localizes to the somatodendritic plasma membrane. Disruption of a conserved N-terminal targeting motif, which causes mislocalization of syntaxin 3, results in coincident mistargeting of the axonal cargos neuron-glia cell adhesion molecule (NgCAM) and neurexin, but not transferrin receptor, a somatodendritic cargo. Similarly, RNAi-mediated knockdown of endogenous syntaxin 3 leads to partial mistargeting of NgCAM, demonstrating that syntaxin 3 plays an important role in its targeting. Additionally, overexpression of syntaxin 3 results in increased axonal growth. Our findings suggest an important role for syntaxin 3 in maintaining neuronal polarity and in the critical task of selective trafficking of membrane protein to axons.
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Affiliation(s)
- Linda Soo Hoo
- Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America
- Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, California, United States of America
| | - Chris D. Banna
- Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America
- Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, California, United States of America
| | - Carolyn M. Radeke
- Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America
- Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, California, United States of America
| | - Nikunj Sharma
- Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America
- Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, California, United States of America
| | - Mary E. Albertolle
- Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America
- Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, California, United States of America
| | - Seng Hui Low
- Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America
- Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, California, United States of America
| | - Thomas Weimbs
- Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America
- Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, California, United States of America
| | - Carol A. Vandenberg
- Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America
- Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, California, United States of America
- * E-mail:
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Small GTPases Rab8a and Rab11a Are Dispensable for Rhodopsin Transport in Mouse Photoreceptors. PLoS One 2016; 11:e0161236. [PMID: 27529348 PMCID: PMC4987053 DOI: 10.1371/journal.pone.0161236] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Accepted: 08/02/2016] [Indexed: 01/01/2023] Open
Abstract
Rab11a and Rab8a are ubiquitous small GTPases shown as required for rhodopsin transport in Xenopus laevis and zebrafish photoreceptors by dominant negative (dn) disruption of function. Here, we generated retina-specific Rab11a (retRab11a) and Rab8a (retRab8a) single and double knockout mice to explore the consequences in mouse photoreceptors. Rhodopsin and other outer segment (OS) membrane proteins targeted correctly to OS and electroretinogram (ERG) responses in all three mutant mouse lines were indistinguishable from wild-type (WT). Further, AAV (adeno-associated virus)-mediated expression of dnRab11b in retRab11a-/- retina, or expression of dnRab8b in retRab8a-/- retina did not cause OS protein mislocalization. Finally, a retRab8a-/- retina injected at one month of age with AAVs expressing dnRab11a, dnRab11b, dnRab8b, and dnRab10 (four dn viruses on Rab8a-/- background) and harvested three months later exhibited normal OS protein localization. In contrast to results obtained with dnRab GTPases in Xenopus and zebrafish, mouse Rab11a and Rab8a are dispensable for proper rhodopsin and outer segment membrane protein targeting. Absence of phenotype after expression of four dn Rab GTPases in a Rab8a-/- retina suggests that Rab8b and Rab11b paralogs maybe dispensable as well. Our data thus demonstrate significant interspecies variation in photoreceptor membrane protein and rhodopsin trafficking.
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Mourão A, Christensen ST, Lorentzen E. The intraflagellar transport machinery in ciliary signaling. Curr Opin Struct Biol 2016; 41:98-108. [PMID: 27393972 DOI: 10.1016/j.sbi.2016.06.009] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Accepted: 06/07/2016] [Indexed: 01/12/2023]
Abstract
Cilia and flagella on eukaryotic cells are slender microtubule-based projections surrounded by a membrane with a unique lipid and protein composition. It is now appreciated that cilia in addition to their established roles in motility also constitute hubs for cellular signaling by sensing external environmental cues necessary for organ development and maintenance of human health. Pathways reported to rely on the cilium organelle include Hedgehog, TGF-β, Wnt, PDGFRα, integrin and DNA damage repair signaling. An emerging theme in ciliary signaling is the requirement for active transport of signaling components into and out of the cilium proper. Here, we review the current state-of-the-art regarding the importance of intraflagellar transport and BBSome multi-subunit complexes in ciliary signaling.
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Affiliation(s)
- André Mourão
- Department of Structural Cell Biology, Max-Planck-Institute of Biochemistry, Am Klopferspitz 18, D-82152 Martinsried, Germany
| | - Søren T Christensen
- Department of Biology, University of Copenhagen, Universitetsparken 13, DK-2100 Copenhagen, Denmark.
| | - Esben Lorentzen
- Department of Structural Cell Biology, Max-Planck-Institute of Biochemistry, Am Klopferspitz 18, D-82152 Martinsried, Germany.
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Jung B, Padula D, Burtscher I, Landerer C, Lutter D, Theis F, Messias AC, Geerlof A, Sattler M, Kremmer E, Boldt K, Ueffing M, Lickert H. Pitchfork and Gprasp2 Target Smoothened to the Primary Cilium for Hedgehog Pathway Activation. PLoS One 2016; 11:e0149477. [PMID: 26901434 PMCID: PMC4763541 DOI: 10.1371/journal.pone.0149477] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Accepted: 01/31/2016] [Indexed: 01/14/2023] Open
Abstract
The seven-transmembrane receptor Smoothened (Smo) activates all Hedgehog (Hh) signaling by translocation into the primary cilia (PC), but how this is regulated is not well understood. Here we show that Pitchfork (Pifo) and the G protein-coupled receptor associated sorting protein 2 (Gprasp2) are essential components of an Hh induced ciliary targeting complex able to regulate Smo translocation to the PC. Depletion of Pifo or Gprasp2 leads to failure of Smo translocation to the PC and lack of Hh target gene activation. Together, our results identify a novel protein complex that is regulated by Hh signaling and required for Smo ciliary trafficking and Hh pathway activation.
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Affiliation(s)
- Bomi Jung
- Institute of Diabetes and Regeneration Research, Helmholtz Zentrum München, München-Neuherberg, Germany
- Institute of Stem Cell Research, Helmholtz Zentrum München, München-Neuherberg, Germany
- German Center for Diabetes Research (DZD), 85764 München-Neuherberg, Germany
| | - Daniela Padula
- Institute of Diabetes and Regeneration Research, Helmholtz Zentrum München, München-Neuherberg, Germany
- Institute of Stem Cell Research, Helmholtz Zentrum München, München-Neuherberg, Germany
- German Center for Diabetes Research (DZD), 85764 München-Neuherberg, Germany
| | - Ingo Burtscher
- Institute of Diabetes and Regeneration Research, Helmholtz Zentrum München, München-Neuherberg, Germany
- Institute of Stem Cell Research, Helmholtz Zentrum München, München-Neuherberg, Germany
- German Center for Diabetes Research (DZD), 85764 München-Neuherberg, Germany
| | - Cedric Landerer
- Institute of Computational Biology, Helmholtz Zentrum München, München-Neuherberg, Germany
- Department of Ecology & Evolutionary Biology, University of Tennessee, Knoxville TN 37996, United States of America
| | - Dominik Lutter
- Institute of Computational Biology, Helmholtz Zentrum München, München-Neuherberg, Germany
- Institute of Diabetes and Adipositas, Helmholtz Zentrum München, München-Neuherberg, Germany
| | - Fabian Theis
- Institute of Computational Biology, Helmholtz Zentrum München, München-Neuherberg, Germany
| | - Ana C. Messias
- Institute of Structural Biology, Helmholtz Zentrum München, München-Neuherberg, Germany
- Center for Integrated Protein Science Munich at Biomolecular NMR Spectroscopy, Department Chemie, Technische Universität München, 85747 Garching, Germany
| | - Arie Geerlof
- Institute of Structural Biology, Helmholtz Zentrum München, München-Neuherberg, Germany
| | - Michael Sattler
- Institute of Structural Biology, Helmholtz Zentrum München, München-Neuherberg, Germany
- Center for Integrated Protein Science Munich at Biomolecular NMR Spectroscopy, Department Chemie, Technische Universität München, 85747 Garching, Germany
| | - Elisabeth Kremmer
- Institute of Molecular Immunology, Helmholtz Zentrum München, München-Neuherberg, Germany
| | - Karsten Boldt
- Department of Protein Science, Helmholtz Zentrum München, München-Neuherberg, Germany
- Centre of Ophthalmology, Institute for Ophthalmology Research, University of Tuebingen, 72076 Tuebingen, Germany
| | - Marius Ueffing
- Department of Protein Science, Helmholtz Zentrum München, München-Neuherberg, Germany
- Centre of Ophthalmology, Institute for Ophthalmology Research, University of Tuebingen, 72076 Tuebingen, Germany
| | - Heiko Lickert
- Institute of Diabetes and Regeneration Research, Helmholtz Zentrum München, München-Neuherberg, Germany
- Institute of Stem Cell Research, Helmholtz Zentrum München, München-Neuherberg, Germany
- German Center for Diabetes Research (DZD), 85764 München-Neuherberg, Germany
- * E-mail:
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39
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Cellular Mechanisms of Ciliary Length Control. Cells 2016; 5:cells5010006. [PMID: 26840332 PMCID: PMC4810091 DOI: 10.3390/cells5010006] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Revised: 01/21/2016] [Accepted: 01/25/2016] [Indexed: 12/12/2022] Open
Abstract
Cilia and flagella are evolutionarily conserved, membrane-bound, microtubule-based organelles on the surface of most eukaryotic cells. They play important roles in coordinating a variety of signaling pathways during growth, development, cell mobility, and tissue homeostasis. Defects in ciliary structure or function are associated with multiple human disorders called ciliopathies. These diseases affect diverse tissues, including, but not limited to the eyes, kidneys, brain, and lungs. Many processes must be coordinated simultaneously in order to initiate ciliogenesis. These include cell cycle, vesicular trafficking, and axonemal extension. Centrioles play a central role in both cell cycle progression and ciliogenesis, making the transition between basal bodies and mitotic spindle organizers integral to both processes. The maturation of centrioles involves a functional shift from cell division toward cilium nucleation which takes place concurrently with its migration and fusion to the plasma membrane. Several proteinaceous structures of the distal appendages in mother centrioles are required for this docking process. Ciliary assembly and maintenance requires a precise balance between two indispensable processes; so called assembly and disassembly. The interplay between them determines the length of the resulting cilia. These processes require a highly conserved transport system to provide the necessary substances at the tips of the cilia and to recycle ciliary turnover products to the base using a based microtubule intraflagellar transport (IFT) system. In this review; we discuss the stages of ciliogenesis as well as mechanisms controlling the lengths of assembled cilia.
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Seixas C, Choi SY, Polgar N, Umberger NL, East MP, Zuo X, Moreiras H, Ghossoub R, Benmerah A, Kahn RA, Fogelgren B, Caspary T, Lipschutz JH, Barral DC. Arl13b and the exocyst interact synergistically in ciliogenesis. Mol Biol Cell 2016; 27:308-20. [PMID: 26582389 PMCID: PMC4713133 DOI: 10.1091/mbc.e15-02-0061] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Revised: 10/29/2015] [Accepted: 11/12/2015] [Indexed: 12/22/2022] Open
Abstract
Arl13b belongs to the ADP-ribosylation factor family within the Ras superfamily of regulatory GTPases. Mutations in Arl13b cause Joubert syndrome, which is characterized by congenital cerebellar ataxia, hypotonia, oculomotor apraxia, and mental retardation. Arl13b is highly enriched in cilia and is required for ciliogenesis in multiple organs. Nevertheless, the precise role of Arl13b remains elusive. Here we report that the exocyst subunits Sec8, Exo70, and Sec5 bind preferentially to the GTP-bound form of Arl13b, consistent with the exocyst being an effector of Arl13b. Moreover, we show that Arl13b binds directly to Sec8 and Sec5. In zebrafish, depletion of arl13b or the exocyst subunit sec10 causes phenotypes characteristic of defective cilia, such as curly tail up, edema, and abnormal pronephric kidney development. We explored this further and found a synergistic genetic interaction between arl13b and sec10 morphants in cilia-dependent phenotypes. Through conditional deletion of Arl13b or Sec10 in mice, we found kidney cysts and decreased ciliogenesis in cells surrounding the cysts. Moreover, we observed a decrease in Arl13b expression in the kidneys from Sec10 conditional knockout mice. Taken together, our results indicate that Arl13b and the exocyst function together in the same pathway leading to functional cilia.
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Affiliation(s)
- Cecília Seixas
- CEDOC, NOVA Medical School/Faculdade de Ciências Médicas, Universidade Nova de Lisboa, 1169-056 Lisbon, Portugal
| | - Soo Young Choi
- Department of Medicine, Medical University of South Carolina, Charleston, SC 29425
| | - Noemi Polgar
- Department of Anatomy, Biochemistry, and Physiology, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, HI 96813
| | - Nicole L Umberger
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30022
| | - Michael P East
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30022
| | - Xiaofeng Zuo
- Department of Medicine, Medical University of South Carolina, Charleston, SC 29425
| | - Hugo Moreiras
- CEDOC, NOVA Medical School/Faculdade de Ciências Médicas, Universidade Nova de Lisboa, 1169-056 Lisbon, Portugal
| | - Rania Ghossoub
- Centre de Recherche en Cancérologie de Marseille, INSERM, UMR7258, 13009 Marseille, France
| | - Alexandre Benmerah
- INSERM UMR 1163, Laboratory of Inherited Kidney Diseases, 75015 Paris, France Paris Descartes-Sorbonne Paris Cité University, Imagine Institute, 75015 Paris, France
| | - Richard A Kahn
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30022
| | - Ben Fogelgren
- Department of Anatomy, Biochemistry, and Physiology, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, HI 96813
| | - Tamara Caspary
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30022
| | - Joshua H Lipschutz
- Department of Medicine, Medical University of South Carolina, Charleston, SC 29425 Department of Medicine, RHJ Veterans Affairs Medical Center, Charleston, SC 29425
| | - Duarte C Barral
- CEDOC, NOVA Medical School/Faculdade de Ciências Médicas, Universidade Nova de Lisboa, 1169-056 Lisbon, Portugal
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41
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Burgoyne T, Meschede IP, Burden JJ, Bailly M, Seabra MC, Futter CE. Rod disc renewal occurs by evagination of the ciliary plasma membrane that makes cadherin-based contacts with the inner segment. Proc Natl Acad Sci U S A 2015; 112:15922-7. [PMID: 26668363 PMCID: PMC4702997 DOI: 10.1073/pnas.1509285113] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The outer segments of vertebrate rod photoreceptors are renewed every 10 d. Outer segment components are transported from the site of synthesis in the inner segment through the connecting cilium, followed by assembly of the highly ordered discs. Two models of assembly of discrete discs involving either successive fusion events between intracellular rhodopsin-bearing vesicles or the evagination of the plasma membrane followed by fusion of adjacent evaginations have been proposed. Here we use immuno-electron microscopy and electron tomography to show that rhodopsin is transported from the inner to the outer segment via the ciliary plasma membrane, subsequently forming successive evaginations that "zipper" up proximally, but at their leading edges are free to make junctions containing the protocadherin, PCDH21, with the inner segment plasma membrane. Given the physical dimensions of the evaginations, coupled with likely instability of the membrane cortex at the distal end of the connecting cilium, we propose that the evagination occurs via a process akin to blebbing and is not driven by actin polymerization. Disassembly of these junctions is accompanied by fusion of the leading edges of successive evaginations to form discrete discs. This fusion is topologically different to that mediated by the membrane fusion proteins, SNAREs, as initial fusion is between exoplasmic leaflets, and is accompanied by gain of the tetraspanin rim protein, peripherin.
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Affiliation(s)
- Thomas Burgoyne
- Institute of Ophthalmology, University College London, London, EC1V9EL, United Kingdom
| | - Ingrid P Meschede
- Institute of Ophthalmology, University College London, London, EC1V9EL, United Kingdom
| | - Jemima J Burden
- Laboratory for Molecular and Cell Biology, University College London, London, WC1E6BT, United Kingdom
| | - Maryse Bailly
- Institute of Ophthalmology, University College London, London, EC1V9EL, United Kingdom
| | - Miguel C Seabra
- National Heart and Lung Institute, Imperial College, London, SW72AZ, United Kingdom; Centro de Estudos de Doenças Crónicas, NOVA Medical School/Faculdade de Ciências Médicas, Universidade Nova de Lisboa, 1169-056, Lisboa, Portugal
| | - Clare E Futter
- Institute of Ophthalmology, University College London, London, EC1V9EL, United Kingdom;
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Zulliger R, Conley SM, Mwoyosvi ML, Stuck MW, Azadi S, Naash MI. SNAREs Interact with Retinal Degeneration Slow and Rod Outer Segment Membrane Protein-1 during Conventional and Unconventional Outer Segment Targeting. PLoS One 2015; 10:e0138508. [PMID: 26406599 PMCID: PMC4583372 DOI: 10.1371/journal.pone.0138508] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Accepted: 08/31/2015] [Indexed: 12/31/2022] Open
Abstract
Mutations in the photoreceptor protein peripherin-2 (also known as RDS) cause severe retinal degeneration. RDS and its homolog ROM-1 (rod outer segment protein 1) are synthesized in the inner segment and then trafficked into the outer segment where they function in tetramers and covalently linked larger complexes. Our goal is to identify binding partners of RDS and ROM-1 that may be involved in their biosynthetic pathway or in their function in the photoreceptor outer segment (OS). Here we utilize several methods including mass spectrometry after affinity purification, in vitro co-expression followed by pull-down, in vivo pull-down from mouse retinas, and proximity ligation assay to identify and confirm the SNARE proteins Syntaxin 3B and SNAP-25 as novel binding partners of RDS and ROM-1. We show that both covalently linked and non-covalently linked RDS complexes interact with Syntaxin 3B. RDS in the mouse is trafficked from the inner segment to the outer segment by both conventional (i.e., Golgi dependent) and unconventional secretory pathways, and RDS from both pathways interacts with Syntaxin3B. Syntaxin 3B and SNAP-25 are enriched in the inner segment (compared to the outer segment) suggesting that the interaction with RDS/ROM-1 occurs in the inner segment. Syntaxin 3B and SNAP-25 are involved in mediating fusion of vesicles carrying other outer segment proteins during outer segment targeting, so could be involved in the trafficking of RDS/ROM-1.
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Affiliation(s)
- Rahel Zulliger
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, 73104, United States of America
| | - Shannon M. Conley
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, 73104, United States of America
| | - Maggie L. Mwoyosvi
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, 73104, United States of America
| | - Michael W. Stuck
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, 73104, United States of America
| | - Seifollah Azadi
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, 73104, United States of America
| | - Muna I. Naash
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, 73104, United States of America
- * E-mail:
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43
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Vetter M, Wang J, Lorentzen E, Deretic D. Novel topography of the Rab11-effector interaction network within a ciliary membrane targeting complex. Small GTPases 2015; 6:165-73. [PMID: 26399276 DOI: 10.1080/21541248.2015.1091539] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
Small GTPases function as universal molecular switches due to the nucleotide dependent conformational changes of their switch regions that allow interacting proteins to discriminate between the active GTP-bound and the inactive GDP-bound states. Guanine nucleotide exchange factors (GEFs) recognize the inactive GDP-bound conformation whereas GTPase activating proteins (GAPs), and the GTPase effectors recognize the active GTP-bound state. Small GTPases are linked to each other through regulatory and effector proteins into functional networks that regulate intracellular membrane traffic through diverse mechanisms that include GEF and GAP cascades, GEF-effector interactions, common effectors and positive feedback loops linking interacting proteins. As more structural and functional information is becoming available, new types of interactions between regulatory proteins, and new mechanisms by which GTPases are networked to control membrane traffic are being revealed. This review will focus on the structure and function of the novel Rab11-FIP3-Rabin8 dual effector complex and its implications for the targeting of sensory receptors to primary cilia, dysfunction of which causes cilia defects underlying human diseases and disorders know as ciliopathies.
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Affiliation(s)
- Melanie Vetter
- a Department of Structural Cell Biology ; Max-Planck-Institute of Biochemistry ; Martinsried , Germany
| | - Jing Wang
- b Departments of Surgery ; Division of Ophthalmology; University of New Mexico ; Albuquerque , NM USA
| | - Esben Lorentzen
- a Department of Structural Cell Biology ; Max-Planck-Institute of Biochemistry ; Martinsried , Germany
| | - Dusanka Deretic
- b Departments of Surgery ; Division of Ophthalmology; University of New Mexico ; Albuquerque , NM USA.,c Cell Biology and Physiology ; University of New Mexico ; Albuquerque , NM USA
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Accumulation of non-outer segment proteins in the outer segment underlies photoreceptor degeneration in Bardet-Biedl syndrome. Proc Natl Acad Sci U S A 2015. [PMID: 26216965 DOI: 10.1073/pnas.1510111112] [Citation(s) in RCA: 96] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Compartmentalization and polarized protein trafficking are essential for many cellular functions. The photoreceptor outer segment (OS) is a sensory compartment specialized for phototransduction, and it shares many features with primary cilia. As expected, mutations disrupting protein trafficking to cilia often disrupt protein trafficking to the OS and cause photoreceptor degeneration. Bardet-Biedl syndrome (BBS) is one of the ciliopathies associated with defective ciliary trafficking and photoreceptor degeneration. However, precise roles of BBS proteins in photoreceptor cells and the underlying mechanisms of photoreceptor degeneration in BBS are not well understood. Here, we show that accumulation of non-OS proteins in the OS underlies photoreceptor degeneration in BBS. Using a newly developed BBS mouse model [Leucine zipper transcription factor-like 1 (Lztfl1)/Bbs17 mutant], isolated OSs, and quantitative proteomics, we determined 138 proteins that are enriched more than threefold in BBS mutant OS. In contrast, only eight proteins showed a more than threefold reduction. We found striking accumulation of Stx3 and Stxbp1/Munc18-1 and loss of polarized localization of Prom1 within the Lztfl1 and Bbs1 mutant OS. Ultrastructural analysis revealed that large vesicles are formed in the BBS OS, disrupting the lamellar structure of the OS. Our findings suggest that accumulation (and consequent sequestration) of non-OS proteins in the OS is likely the primary cause of photoreceptor degeneration in BBS. Our data also suggest that a major function of BBS proteins in photoreceptors is to transport proteins from the OS to the cell body or to prevent entry of non-OS proteins into the OS.
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45
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German OL, Agnolazza DL, Politi LE, Rotstein NP. Light, lipids and photoreceptor survival: live or let die? Photochem Photobiol Sci 2015. [PMID: 26204250 DOI: 10.1039/c5pp00194c] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Due to its constant exposure to light and its high oxygen consumption the retina is highly sensitive to oxidative damage, which is a common factor in inducing the death of photoreceptors after light damage or in inherited retinal degenerations. The high content of docosahexaenoic acid (DHA), the major polyunsaturated fatty acid in the retina, has been suggested to contribute to this sensitivity. DHA is crucial for developing and preserving normal visual function. However, further roles of DHA in the retina are still controversial. Current data support that it can tilt the scale either towards degeneration or survival of retinal cells. DHA peroxidation products can be deleterious to the retina and might lead to retinal degeneration. However, DHA has also been shown to act as, or to be the source of, a survival molecule that protects photoreceptors and retinal pigment epithelium cells from oxidative damage. We have established that DHA protects photoreceptors from oxidative stress-induced apoptosis and promotes their differentiation in vitro. DHA activates the retinoid X receptor (RXR) and the ERK/MAPK pathway, thus regulating the expression of anti and pro-apoptotic proteins. It also orchestrates a diversity of signaling pathways, modulating enzymatic pathways that control the sphingolipid metabolism and activate antioxidant defense mechanisms to promote photoreceptor survival and development. A deeper comprehension of DHA signaling pathways and context-dependent behavior is required to understand its dual functions in retinal physiology.
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Affiliation(s)
- Olga Lorena German
- Instituto de Investigaciones Bioquímicas de Bahía Blanca (INIBIBB), Universidad Nacional del Sur (UNS)-CONICET, Bahía Blanca, Buenos Aires, Argentina.
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Leaf A, Von Zastrow M. Dopamine receptors reveal an essential role of IFT-B, KIF17, and Rab23 in delivering specific receptors to primary cilia. eLife 2015; 4. [PMID: 26182404 PMCID: PMC4547097 DOI: 10.7554/elife.06996] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 07/15/2015] [Indexed: 01/05/2023] Open
Abstract
Appropriate physiological signaling by primary cilia depends on the specific targeting of particular receptors to the ciliary membrane, but how this occurs remains poorly understood. In this study, we show that D1-type dopaminergic receptors are delivered to cilia from the extra-ciliary plasma membrane by a mechanism requiring the receptor cytoplasmic tail, the intraflagellar transport complex-B (IFT-B), and ciliary kinesin KIF17. This targeting mechanism critically depends on Rab23, a small guanine nucleotide binding protein that has important effects on physiological signaling from cilia but was not known previously to be essential for ciliary delivery of any cargo. Depleting Rab23 prevents dopamine receptors from accessing the ciliary membrane. Conversely, fusion of Rab23 to a non-ciliary receptor is sufficient to drive robust, nucleotide-dependent mis-localization to the ciliary membrane. Dopamine receptors thus reveal a previously unrecognized mechanism of ciliary receptor targeting and functional role of Rab23 in promoting this process.
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Affiliation(s)
- Alison Leaf
- Program in Cell Biology, University of California, San Francisco, San Francisco, United States
| | - Mark Von Zastrow
- Program in Cell Biology, University of California, San Francisco, San Francisco, United States
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Rao KN, Li L, Anand M, Khanna H. Ablation of retinal ciliopathy protein RPGR results in altered photoreceptor ciliary composition. Sci Rep 2015; 5:11137. [PMID: 26068394 PMCID: PMC4463945 DOI: 10.1038/srep11137] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Accepted: 05/14/2015] [Indexed: 11/09/2022] Open
Abstract
Cilia regulate several developmental and homeostatic pathways that are critical to survival. Sensory cilia of photoreceptors regulate phototransduction cascade for visual processing. Mutations in the ciliary protein RPGR (retinitis pigmentosa GTPase regulator) are a prominent cause of severe blindness disorders due to degeneration of mature photoreceptors. However, precise function of RPGR is still unclear. Here we studied the involvement of RPGR in ciliary trafficking by analyzing the composition of photoreceptor sensory cilia (PSC) in Rpgrko retina. Using tandem mass spectrometry analysis followed by immunoblotting, we detected few alterations in levels of proteins involved in proteasomal function and vesicular trafficking in Rpgrko PSC, prior to onset of degeneration. We also found alterations in the levels of high molecular weight soluble proteins in Rpgrko PSC. Our data indicate RPGR regulates entry or retention of soluble proteins in photoreceptor cilia but spares the trafficking of key structural and phototransduction-associated proteins. Given a frequent occurrence of RPGR mutations in severe photoreceptor degeneration due to ciliary disorders, our results provide insights into pathways resulting in altered mature cilia function in ciliopathies.
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Affiliation(s)
- Kollu N Rao
- Department of Ophthalmology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Linjing Li
- Department of Ophthalmology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Manisha Anand
- Department of Ophthalmology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Hemant Khanna
- Department of Ophthalmology, University of Massachusetts Medical School, Worcester, MA 01605, USA
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48
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Finetti F, Patrussi L, Galgano D, Cassioli C, Perinetti G, Pazour GJ, Baldari CT. The small GTPase Rab8 interacts with VAMP-3 to regulate the delivery of recycling T-cell receptors to the immune synapse. J Cell Sci 2015; 128:2541-52. [PMID: 26034069 DOI: 10.1242/jcs.171652] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Accepted: 05/22/2015] [Indexed: 12/31/2022] Open
Abstract
IFT20, a component of the intraflagellar transport (IFT) system that controls ciliogenesis, regulates immune synapse assembly in the non-ciliated T-cell by promoting T-cell receptor (TCR) recycling. Here, we have addressed the role of Rab8 (for which there are two isoforms Rab8a and Rab8b), a small GTPase implicated in ciliogenesis, in TCR traffic to the immune synapse. We show that Rab8, which colocalizes with IFT20 in Rab11(+) endosomes, is required for TCR recycling. Interestingly, as opposed to in IFT20-deficient T-cells, TCR(+) endosomes polarized normally beneath the immune synapse membrane in the presence of dominant-negative Rab8, but were unable to undergo the final docking or fusion step. This could be accounted for by the inability of the vesicular (v)-SNARE VAMP-3 to cluster at the immune synapse in the absence of functional Rab8, which is responsible for its recruitment. Of note, and similar to in T-cells, VAMP-3 interacts with Rab8 at the base of the cilium in NIH-3T3 cells, where it regulates ciliary growth and targeting of the protein smoothened. The results identify Rab8 as a new player in vesicular traffic to the immune synapse and provide insight into the pathways co-opted by different cell types for immune synapse assembly and ciliogenesis.
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Affiliation(s)
- Francesca Finetti
- Department of Life Sciences, University of Siena, Siena 53100, Italy
| | - Laura Patrussi
- Department of Life Sciences, University of Siena, Siena 53100, Italy
| | - Donatella Galgano
- Department of Life Sciences, University of Siena, Siena 53100, Italy
| | - Chiara Cassioli
- Department of Life Sciences, University of Siena, Siena 53100, Italy
| | - Giuseppe Perinetti
- Department of Medical, Surgical and Health Sciences, School of Dentistry, University of Trieste, Trieste 34129, Italy
| | - Gregory J Pazour
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Cosima T Baldari
- Department of Life Sciences, University of Siena, Siena 53100, Italy
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Identification of genome-wide SNP-SNP and SNP-clinical Boolean interactions in age-related macular degeneration. Methods Mol Biol 2015; 1253:217-55. [PMID: 25403535 DOI: 10.1007/978-1-4939-2155-3_12] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We propose here a methodology to uncover modularities in the network of SNP-SNP interactions most associated with disease. We start by computing all possible Boolean binary SNP interactions across the whole genome. By constructing a weighted graph of the most relevant interactions and via a combinatorial optimization approach, we find the most highly interconnected SNPs. We show that the method can be easily extended to find SNP/environment interactions. Using a modestly sized GWAS dataset of age-related macular degeneration (AMD), we identify a group of only 19 SNPs, which include those in previously reported regions associated to AMD. We also uncover a larger set of loci pointing to a matrix of key processes and functions that are affected. The proposed integrative methodology extends and overlaps traditional statistical analysis in a natural way. Combinatorial optimization techniques allow us to find the kernel of the most central interactions, complementing current methods of GWAS analysis and also enhancing the search for gene-environment interaction.
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Polyunsaturated fatty acids and their metabolites in brain function and disease. Nat Rev Neurosci 2014; 15:771-85. [PMID: 25387473 DOI: 10.1038/nrn3820] [Citation(s) in RCA: 892] [Impact Index Per Article: 89.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The brain is highly enriched with fatty acids. These include the polyunsaturated fatty acids (PUFAs) arachidonic acid and docosahexaenoic acid, which are largely esterified to the phospholipid cell membrane. Once PUFAs are released from the membrane, they can participate in signal transduction, either directly or after enzymatic conversion to a variety of bioactive derivatives ('mediators'). PUFAs and their mediators regulate several processes within the brain, such as neurotransmission, cell survival and neuroinflammation, and thereby mood and cognition. PUFA levels and the signalling pathways that they regulate are altered in various neurological disorders, including Alzheimer's disease and major depression. Diet and drugs targeting PUFAs may lead to novel therapeutic approaches for the prevention and treatment of brain disorders.
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