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Rutan Woods CT, Makia MS, Lewis TR, Crane R, Zeibak S, Yu P, Kakakhel M, Castillo CM, Arshavsky VY, Naash MI, Al-Ubaidi MR. Downregulation of rhodopsin is an effective therapeutic strategy in ameliorating peripherin-2-associated inherited retinal disorders. Nat Commun 2024; 15:4756. [PMID: 38834544 PMCID: PMC11150396 DOI: 10.1038/s41467-024-48846-5] [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: 08/22/2023] [Accepted: 05/15/2024] [Indexed: 06/06/2024] Open
Abstract
Given the absence of approved treatments for pathogenic variants in Peripherin-2 (PRPH2), it is imperative to identify a universally effective therapeutic target for PRPH2 pathogenic variants. To test the hypothesis that formation of the elongated discs in presence of PRPH2 pathogenic variants is due to the presence of the full complement of rhodopsin in absence of the required amounts of functional PRPH2. Here we demonstrate the therapeutic potential of reducing rhodopsin levels in ameliorating disease phenotype in knockin models for p.Lys154del (c.458-460del) and p.Tyr141Cys (c.422 A > G) in PRPH2. Reducing rhodopsin levels improves physiological function, mitigates the severity of disc abnormalities, and decreases retinal gliosis. Additionally, intravitreal injections of a rhodopsin-specific antisense oligonucleotide successfully enhance the physiological function of photoreceptors and improves the ultrastructure of discs in mutant mice. Presented findings shows that reducing rhodopsin levels is an effective therapeutic strategy for the treatment of inherited retinal degeneration associated with PRPH2 pathogenic variants.
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Affiliation(s)
| | - Mustafa S Makia
- Department of Biomedical Engineering, University of Houston, Houston, TX, 77204, USA
| | - Tylor R Lewis
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, 27710, USA
| | - Ryan Crane
- Department of Biomedical Engineering, University of Houston, Houston, TX, 77204, USA
| | - Stephanie Zeibak
- Department of Biomedical Engineering, University of Houston, Houston, TX, 77204, USA
| | - Paul Yu
- Department of Biomedical Engineering, University of Houston, Houston, TX, 77204, USA
| | - Mashal Kakakhel
- Department of Biomedical Engineering, University of Houston, Houston, TX, 77204, USA
| | - Carson M Castillo
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, 27710, USA
| | - Vadim Y Arshavsky
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, 27710, USA
| | - Muna I Naash
- Department of Biomedical Engineering, University of Houston, Houston, TX, 77204, USA.
| | - Muayyad R Al-Ubaidi
- Department of Biomedical Engineering, University of Houston, Houston, TX, 77204, USA.
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2
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Seidemann S, Salomon F, Hoffmann KB, Kurth T, Sbalzarini IF, Haase R, Ader M. Automated quantification of photoreceptor outer segments in developing and degenerating retinas on microscopy images across scales. Front Mol Neurosci 2024; 17:1398447. [PMID: 38854587 PMCID: PMC11157083 DOI: 10.3389/fnmol.2024.1398447] [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: 03/09/2024] [Accepted: 04/17/2024] [Indexed: 06/11/2024] Open
Abstract
The functionality of photoreceptors, rods, and cones is highly dependent on their outer segments (POS), a cellular compartment containing highly organized membranous structures that generate biochemical signals from incident light. While POS formation and degeneration are qualitatively assessed on microscopy images, reliable methodology for quantitative analyses is still limited. Here, we developed methods to quantify POS (QuaPOS) maturation and quality on retinal sections using automated image analyses. POS formation was examined during the development and in adulthood of wild-type mice via light microscopy (LM) and transmission electron microscopy (TEM). To quantify the number, size, shape, and fluorescence intensity of POS, retinal cryosections were immunostained for the cone POS marker S-opsin. Fluorescence images were used to train the robust classifier QuaPOS-LM based on supervised machine learning for automated image segmentation. Characteristic features of segmentation results were extracted to quantify the maturation of cone POS. Subsequently, this quantification method was applied to characterize POS degeneration in "cone photoreceptor function loss 1" mice. TEM images were used to establish the ultrastructural quantification method QuaPOS-TEM for the alignment of POS membranes. Images were analyzed using a custom-written MATLAB code to extract the orientation of membranes from the image gradient and their alignment (coherency). This analysis was used to quantify the POS morphology of wild-type and two inherited retinal degeneration ("retinal degeneration 19" and "rhodopsin knock-out") mouse lines. Both automated analysis technologies provided robust characterization and quantification of POS based on LM or TEM images. Automated image segmentation by the classifier QuaPOS-LM and analysis of the orientation of membrane stacks by QuaPOS-TEM using fluorescent or TEM images allowed quantitative evaluation of POS formation and quality. The assessments showed an increase in POS number, volume, and membrane coherency during wild-type postnatal development, while a decrease in all three observables was detected in different retinal degeneration mouse models. All the code used for the presented analysis is open source, including example datasets to reproduce the findings. Hence, the QuaPOS quantification methods are useful for in-depth characterization of POS on retinal sections in developmental studies, for disease modeling, or after therapeutic interventions affecting photoreceptors.
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Affiliation(s)
- Suse Seidemann
- Center for Regenerative Therapies Dresden (CRTD), Technische Universität Dresden, Dresden, Germany
- Center for Molecular and Cellular Bioengineering (CMCB), Technische Universität Dresden, Dresden, Germany
| | - Florian Salomon
- Center for Regenerative Therapies Dresden (CRTD), Technische Universität Dresden, Dresden, Germany
- Center for Molecular and Cellular Bioengineering (CMCB), Technische Universität Dresden, Dresden, Germany
| | - Karl B. Hoffmann
- Faculty of Computer Science, Technische Universität Dresden, Dresden, Germany
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
- Center for Systems Biology Dresden, Dresden, Germany
| | - Thomas Kurth
- Core Facility Electron Microscopy and Histology, Technology Platform, Center for Molecular and Cellular Bioengineering (CMCB), Technische Universität Dresden, Dresden, Germany
| | - Ivo F. Sbalzarini
- Faculty of Computer Science, Technische Universität Dresden, Dresden, Germany
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
- Center for Systems Biology Dresden, Dresden, Germany
- DFG Cluster of Excellence “Physics of Life”, Technische Universität Dresden, Dresden, Germany
- Center for Scalable Data Analytics and Artificial Intelligence (ScaDS.AI), Leipzig University, Leipzig, Germany
| | - Robert Haase
- DFG Cluster of Excellence “Physics of Life”, Technische Universität Dresden, Dresden, Germany
- Center for Scalable Data Analytics and Artificial Intelligence (ScaDS.AI), Leipzig University, Leipzig, Germany
| | - Marius Ader
- Center for Regenerative Therapies Dresden (CRTD), Technische Universität Dresden, Dresden, Germany
- Center for Molecular and Cellular Bioengineering (CMCB), Technische Universität Dresden, Dresden, Germany
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3
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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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4
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Miller LR, Bickel MA, Tarantini S, Runion ME, Matacchiera Z, Vance ML, Hibbs C, Vaden H, Nagykaldi D, Martin T, Bullen EC, Pinckard J, Kiss T, Howard EW, Yabluchanskiy A, Conley SM. IGF1R deficiency in vascular smooth muscle cells impairs myogenic autoregulation and cognition in mice. Front Aging Neurosci 2024; 16:1320808. [PMID: 38425784 PMCID: PMC10902040 DOI: 10.3389/fnagi.2024.1320808] [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: 10/13/2023] [Accepted: 01/22/2024] [Indexed: 03/02/2024] Open
Abstract
Introduction Cerebrovascular pathologies contribute to cognitive decline during aging, leading to vascular cognitive impairment and dementia (VCID). Levels of circulating insulin-like growth factor 1 (IGF-1), a vasoprotective hormone, decrease during aging. Decreased circulating IGF-1 in animal models leads to the development of VCID-like symptoms, but the cellular mechanisms underlying IGF-1-deficiency associated pathologies in the aged cerebrovasculature remain poorly understood. Here, we test the hypothesis that vascular smooth muscle cells (VSMCs) play an integral part in mediating the vasoprotective effects of IGF-1. Methods We used a hypertension-based model of cerebrovascular dysfunction in mice with VSMC-specific IGF-1 receptor (Igf1r) deficiency and evaluated the development of cerebrovascular pathologies and cognitive dysfunction. Results VSMC-specific Igf1r deficiency led to impaired cerebral myogenic autoregulation, independent of blood pressure changes, which was also associated with impaired spatial learning and memory function as measured by radial arm water maze and impaired motor learning measured by rotarod. In contrast, VSMC-specific IGF-1 receptor knockdown did not lead to cerebral microvascular rarefaction. Discussion These studies suggest that VSMCs are key targets for IGF-1 in the context of cerebrovascular health, playing a role in vessel stability alongside other cells in the neurovascular unit, and that VSMC dysfunction in aging likely contributes to VCID.
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Affiliation(s)
- Lauren R. Miller
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - Marisa A. Bickel
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - Stefano Tarantini
- Vascular Cognitive Impairment and Neurodegeneration Program, Oklahoma Center for Geroscience and Healthy Brain Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
- Department of Neurosurgery, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
- The Peggy and Charles Stephenson Cancer Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
- Department of Health Promotion Sciences, College of Public Health, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - Megan E. Runion
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - Zoe Matacchiera
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - Michaela L. Vance
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - Clara Hibbs
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - Hannah Vaden
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - Domonkos Nagykaldi
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - Teryn Martin
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - Elizabeth C. Bullen
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - Jessica Pinckard
- Division of Comparative Medicine, Department of Pathology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - Tamas Kiss
- Pediatric Center, Semmelweis University, Budapest, Hungary
- Eötvös Loránd Research Network and Semmelweis University Cerebrovascular and Neurocognitive Disorders Research Group, Budapest, Hungary
| | - Eric W. Howard
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - Andriy Yabluchanskiy
- Vascular Cognitive Impairment and Neurodegeneration Program, Oklahoma Center for Geroscience and Healthy Brain Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
- Department of Neurosurgery, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - Shannon M. Conley
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
- Vascular Cognitive Impairment and Neurodegeneration Program, Oklahoma Center for Geroscience and Healthy Brain Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
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5
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Lewis TR, Makia MS, Castillo CM, Hao Y, Al-Ubaidi MR, Skiba NP, Conley SM, Arshavsky VY, Naash MI. ROM1 is redundant to PRPH2 as a molecular building block of photoreceptor disc rims. eLife 2023; 12:RP89444. [PMID: 37991486 PMCID: PMC10665016 DOI: 10.7554/elife.89444] [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] [Indexed: 11/23/2023] Open
Abstract
Visual signal transduction takes place within a stack of flattened membranous 'discs' enclosed within the light-sensitive photoreceptor outer segment. The highly curved rims of these discs, formed in the process of disc enclosure, are fortified by large hetero-oligomeric complexes of two homologous tetraspanin proteins, PRPH2 (a.k.a. peripherin-2 or rds) and ROM1. While mutations in PRPH2 affect the formation of disc rims, the role of ROM1 remains poorly understood. In this study, we found that the knockout of ROM1 causes a compensatory increase in the disc content of PRPH2. Despite this increase, discs of ROM1 knockout mice displayed a delay in disc enclosure associated with a large diameter and lack of incisures in mature discs. Strikingly, further increasing the level of PRPH2 rescued these morphological defects. We next showed that disc rims are still formed in a knockin mouse in which the tetraspanin body of PRPH2 was replaced with that of ROM1. Together, these results demonstrate that, despite its contribution to the formation of disc rims, ROM1 can be replaced by an excess of PRPH2 for timely enclosure of newly forming discs and establishing normal outer segment structure.
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Affiliation(s)
- Tylor R Lewis
- Department of Ophthalmology, Duke University Medical CenterDurhamUnited States
| | - Mustafa S Makia
- Department of Biomedical Engineering, University of HoustonHoustonUnited States
| | - Carson M Castillo
- Department of Ophthalmology, Duke University Medical CenterDurhamUnited States
| | - Ying Hao
- Department of Ophthalmology, Duke University Medical CenterDurhamUnited States
| | - Muayyad R Al-Ubaidi
- Department of Biomedical Engineering, University of HoustonHoustonUnited States
- College of Optometry, University of HoustonHoustonUnited States
| | - Nikolai P Skiba
- Department of Ophthalmology, Duke University Medical CenterDurhamUnited States
| | - Shannon M Conley
- Department of Cell Biology, University of Oklahoma Health Sciences CenterOklahoma CityUnited States
| | - Vadim Y Arshavsky
- Department of Ophthalmology, Duke University Medical CenterDurhamUnited States
- Department of Pharmacology and Cancer Biology, Duke University Medical CenterDurhamUnited States
| | - Muna I Naash
- Department of Biomedical Engineering, University of HoustonHoustonUnited States
- College of Optometry, University of HoustonHoustonUnited States
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6
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Ruiz-Pastor MJ, Sánchez-Sáez X, Kutsyr O, Albertos-Arranz H, Sánchez-Castillo C, Ortuño-Lizarán I, Martínez-Gil N, Vidal-Gil L, Méndez L, Sánchez-Martín M, Maneu V, Lax P, Cuenca N. Prph2 knock-in mice recapitulate human central areolar choroidal dystrophy retinal degeneration and exhibit aberrant synaptic remodeling and microglial activation. Cell Death Dis 2023; 14:711. [PMID: 37914688 PMCID: PMC10620171 DOI: 10.1038/s41419-023-06243-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 10/16/2023] [Accepted: 10/20/2023] [Indexed: 11/03/2023]
Abstract
Central areolar choroidal dystrophy is an inherited disorder characterized by progressive choriocapillaris atrophy and retinal degeneration and is usually associated with mutations in the PRPH2 gene. We aimed to generate and characterize a mouse model with the p.Arg195Leu mutation previously described in patients. Heterozygous (Prph2WT/KI) and homozygous (Prph2KI/KI) mice were generated using the CRISPR/Cas9 system to introduce the p.Arg195Leu mutation. Retinal function was assessed by electroretinography and optomotor tests at 1, 3, 6, 9, 12, and 20 months of age. The structural integrity of the retinas was evaluated at the same ages using optical coherence tomography. Immunofluorescence and transmission electron microscopy images of the retina were also analyzed. Genetic sequencing confirmed that both Prph2WT/KI and Prph2KI/KI mice presented the p.Arg195Leu mutation. A progressive loss of retinal function was found in both mutant groups, with significantly reduced visual acuity from 3 months of age in Prph2KI/KI mice and from 6 months of age in Prph2WT/KI mice. Decreased amplitudes in the electroretinography responses were observed from 1 month of age in Prph2KI/KI mice and from 6 months of age in Prph2WT/KI mice. Morphological analysis of the retinas correlated with functional findings, showing a progressive decrease in retinal thickness of mutant mice, with earlier and more severe changes in the homozygous mutant mice. We corroborated the alteration of the outer segment structure, and we found changes in the synaptic connectivity in the outer plexiform layer as well as gliosis and signs of microglial activation. The new Prph2WT/KI and Prph2KI/KI murine models show a pattern of retinal degeneration similar to that described in human patients with central areolar choroidal dystrophy and appear to be good models to study the mechanisms involved in the onset and progression of the disease, as well as to test the efficacy of new therapeutic strategies.
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Affiliation(s)
| | - Xavier Sánchez-Sáez
- Physiology, Genetics, and Microbiology, University of Alicante, Alicante, Spain
| | - Oksana Kutsyr
- Optics, Pharmacology, and Anatomy, University of Alicante, Alicante, Spain
| | | | | | | | | | - Lorena Vidal-Gil
- Physiology, Genetics, and Microbiology, University of Alicante, Alicante, Spain
| | - Lucía Méndez
- Transgenic Facility and Department of Medicine, University of Salamanca, Salamanca, Spain
| | - Manuel Sánchez-Martín
- Transgenic Facility and Department of Medicine, University of Salamanca, Salamanca, Spain
- Institute for Biomedical Research of Salamanca (IBSAL), Salamanca, Spain
| | - Victoria Maneu
- Optics, Pharmacology, and Anatomy, University of Alicante, Alicante, Spain
- Alicante Institute for Health and Biomedical Research (ISABIAL), Alicante, Spain
| | - Pedro Lax
- Physiology, Genetics, and Microbiology, University of Alicante, Alicante, Spain.
- Alicante Institute for Health and Biomedical Research (ISABIAL), Alicante, Spain.
| | - Nicolás Cuenca
- Physiology, Genetics, and Microbiology, University of Alicante, Alicante, Spain.
- Alicante Institute for Health and Biomedical Research (ISABIAL), Alicante, Spain.
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7
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Lewis TR, Makia MS, Castillo CM, Hao Y, Al-Ubaidi MR, Skiba NP, Conley SM, Arshavsky VY, Naash MI. ROM1 is redundant to PRPH2 as a molecular building block of photoreceptor disc rims. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.02.547380. [PMID: 37693615 PMCID: PMC10491102 DOI: 10.1101/2023.07.02.547380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/12/2023]
Abstract
Visual signal transduction takes place within a stack of flattened membranous "discs" enclosed within the light-sensitive photoreceptor outer segment. The highly curved rims of these discs, formed in the process of disc enclosure, are fortified by large hetero-oligomeric complexes of two homologous tetraspanin proteins, PRPH2 (a.k.a. peripherin-2 or rds) and ROM1. While mutations in PRPH2 affect the formation of disc rims, the role of ROM1 remains poorly understood. In this study, we found that the knockout of ROM1 causes a compensatory increase in the disc content of PRPH2. Despite this increase, discs of ROM1 knockout mice displayed a delay in disc enclosure associated with a large diameter and lack of incisures in mature discs. Strikingly, further increasing the level of PRPH2 rescued these morphological defects. We next showed that disc rims are still formed in a knockin mouse in which the tetraspanin body of PRPH2 was replaced with that of ROM1. Together, these results demonstrate that, despite its contribution to the formation of disc rims, ROM1 can be replaced by an excess of PRPH2 for timely enclosure of newly forming discs and establishing normal outer segment structure.
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Affiliation(s)
- Tylor R. Lewis
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, USA, 27710
| | - Mustafa S. Makia
- Department of Biomedical Engineering, University of Houston, Houston, TX, USA, 77204
| | - Carson M. Castillo
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, USA, 27710
| | - Ying Hao
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, USA, 27710
| | - Muayyad R. Al-Ubaidi
- Department of Biomedical Engineering, University of Houston, Houston, TX, USA, 77204
- College of Optometry, University of Houston, Houston, TX, USA, 77204
| | - Nikolai P. Skiba
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, USA, 27710
| | - Shannon M. Conley
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA, 73104
| | - Vadim Y. Arshavsky
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, USA, 27710
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA, 27710
| | - Muna I. Naash
- Department of Biomedical Engineering, University of Houston, Houston, TX, USA, 77204
- College of Optometry, University of Houston, Houston, TX, USA, 77204
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8
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Ikelle L, Makia M, Lewis T, Crane R, Kakakhel M, Conley SM, Birtley JR, Arshavsky VY, Al-Ubaidi MR, Naash MI. Comparative study of PRPH2 D2 loop mutants reveals divergent disease mechanism in rods and cones. Cell Mol Life Sci 2023; 80:214. [PMID: 37466729 PMCID: PMC10356684 DOI: 10.1007/s00018-023-04851-3] [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: 01/25/2023] [Revised: 05/10/2023] [Accepted: 06/28/2023] [Indexed: 07/20/2023]
Abstract
Mutations in the photoreceptor-specific tetraspanin gene peripherin-2 (PRPH2) lead to widely varying forms of retinal degeneration ranging from retinitis pigmentosa to macular dystrophy. Both inter- and intra-familial phenotypic heterogeneity has led to much interest in uncovering the complex pathogenic mechanisms of PRPH2-associated disease. Majority of disease-causing mutations in PRPH2 reside in the second intradiscal loop, wherein seven cysteines control protein folding and oligomerization. Here, we utilize knockin models to evaluate the role of three D2 loop cysteine mutants (Y141C, C213Y and C150S), alone or in combination. We elucidated how these mutations affect PRPH2 properties, including oligomerization and subcellular localization, and contribute to disease processes. Results from our structural, functional and molecular studies revealed that, in contrast to our understanding from prior investigations, rods are highly affected by PRPH2 mutations interfering with oligomerization and not merely by the haploinsufficiency associated with these mutations. On the other hand, cones are less affected by the toxicity of the mutant protein and significantly reduced protein levels, suggesting that knockdown therapeutic strategies may sustain cone functionality for a longer period. This observation provides useful data to guide and simplify the current development of effective therapeutic approaches for PRPH2-associated diseases that combine knockdown with high levels of gene supplementation needed to generate prolonged rod improvement.
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Affiliation(s)
- Larissa Ikelle
- Department of Biomedical Engineering, University of Houston, 3517 Cullen Blvd. Room 2027, Houston, TX, 77204-5060, USA
| | - Mustafa Makia
- Department of Biomedical Engineering, University of Houston, 3517 Cullen Blvd. Room 2027, Houston, TX, 77204-5060, USA
| | - Tylor Lewis
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, USA
| | - Ryan Crane
- Department of Biomedical Engineering, University of Houston, 3517 Cullen Blvd. Room 2027, Houston, TX, 77204-5060, USA
| | - Mashal Kakakhel
- Department of Biomedical Engineering, University of Houston, 3517 Cullen Blvd. Room 2027, Houston, TX, 77204-5060, USA
| | - Shannon M Conley
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
| | | | - Vadim Y Arshavsky
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, USA
| | - Muayyad R Al-Ubaidi
- Department of Biomedical Engineering, University of Houston, 3517 Cullen Blvd. Room 2027, Houston, TX, 77204-5060, USA.
| | - Muna I Naash
- Department of Biomedical Engineering, University of Houston, 3517 Cullen Blvd. Room 2027, Houston, TX, 77204-5060, USA.
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9
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Lewis TR, Phan S, Castillo CM, Kim KY, Coppenrath K, Thomas W, Hao Y, Skiba NP, Horb ME, Ellisman MH, Arshavsky VY. Photoreceptor disc incisures form as an adaptive mechanism ensuring the completion of disc enclosure. eLife 2023; 12:e89160. [PMID: 37449984 PMCID: PMC10361718 DOI: 10.7554/elife.89160] [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: 05/05/2023] [Accepted: 07/13/2023] [Indexed: 07/18/2023] Open
Abstract
The first steps of vision take place within a stack of tightly packed disc-shaped membranes, or 'discs', located in the outer segment compartment of photoreceptor cells. In rod photoreceptors, discs are enclosed inside the outer segment and contain deep indentations in their rims called 'incisures'. The presence of incisures has been documented in a variety of species, yet their role remains elusive. In this study, we combined traditional electron microscopy with three-dimensional electron tomography to demonstrate that incisures are formed only after discs become completely enclosed. We also observed that, at the earliest stage of their formation, discs are not round as typically depicted but rather are highly irregular in shape and resemble expanding lamellipodia. Using genetically manipulated mice and frogs and measuring outer segment protein abundances by quantitative mass spectrometry, we further found that incisure size is determined by the molar ratio between peripherin-2, a disc rim protein critical for the process of disc enclosure, and rhodopsin, the major structural component of disc membranes. While a high perpherin-2 to rhodopsin ratio causes an increase in incisure size and structural complexity, a low ratio precludes incisure formation. Based on these data, we propose a model whereby normal rods express a modest excess of peripherin-2 over the amount required for complete disc enclosure in order to ensure that this important step of disc formation is accomplished. Once the disc is enclosed, the excess peripherin-2 incorporates into the rim to form an incisure.
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Affiliation(s)
- Tylor R Lewis
- Department of Ophthalmology, Duke University Medical CenterDurhamUnited States
| | - Sebastien Phan
- National Center for Microscopy and Imaging Research, School of Medicine, University of California, San DiegoLa JollaUnited States
| | - Carson M Castillo
- Department of Ophthalmology, Duke University Medical CenterDurhamUnited States
| | - Keun-Young Kim
- National Center for Microscopy and Imaging Research, School of Medicine, University of California, San DiegoLa JollaUnited States
| | - Kelsey Coppenrath
- Eugene Bell Center for Regenerative Biology and Tissue Engineering and National Xenopus ResourceWoods HoleUnited States
| | - William Thomas
- Eugene Bell Center for Regenerative Biology and Tissue Engineering and National Xenopus ResourceWoods HoleUnited States
| | - Ying Hao
- Department of Ophthalmology, Duke University Medical CenterDurhamUnited States
| | - Nikolai P Skiba
- Department of Ophthalmology, Duke University Medical CenterDurhamUnited States
| | - Marko E Horb
- Eugene Bell Center for Regenerative Biology and Tissue Engineering and National Xenopus ResourceWoods HoleUnited States
| | - Mark H Ellisman
- National Center for Microscopy and Imaging Research, School of Medicine, University of California, San DiegoLa JollaUnited States
| | - Vadim Y Arshavsky
- Department of Ophthalmology, Duke University Medical CenterDurhamUnited States
- Department of Pharmacology and Cancer Biology, Duke University Medical CenterDurhamUnited States
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10
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Lewis TR, Phan S, Castillo CM, Kim KY, Coppenrath K, Thomas W, Hao Y, Skiba NP, Horb ME, Ellisman MH, Arshavsky VY. Photoreceptor disc incisures form as an adaptive mechanism ensuring the completion of disc enclosure. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.06.535932. [PMID: 37066355 PMCID: PMC10104153 DOI: 10.1101/2023.04.06.535932] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/18/2023]
Abstract
The first steps of vision take place within a stack of tightly packed disc-shaped membranes, or "discs", located in the outer segment compartment of photoreceptor cells. In rod photoreceptors, discs are enclosed inside the outer segment and contain deep indentations in their rims called "incisures". The presence of incisures has been documented in a variety of species, yet their role remains elusive. In this study, we combined traditional electron microscopy with three-dimensional electron tomography to demonstrate that incisures are formed only after discs become completely enclosed. We also observed that, at the earliest stage of their formation, discs are not round as typically depicted but rather are highly irregular in shape and resemble expanding lamellipodia. Using genetically manipulated mice and frogs and measuring outer segment protein abundances by quantitative mass spectrometry, we further found that incisure size is determined by the molar ratio between peripherin-2, a disc rim protein critical for the process of disc enclosure, and rhodopsin, the major structural component of disc membranes. While a high perpherin-2 to rhodopsin ratio causes an increase in incisure size and structural complexity, a low ratio precludes incisure formation. Based on these data, we propose a model whereby normal rods express a modest excess of peripherin-2 over the amount required for complete disc enclosure in order to ensure that this important step of disc formation is accomplished. Once the disc is enclosed, the excess peripherin-2 incorporates into the rim to form an incisure.
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11
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Lewis TR, Al-Ubaidi MR, Naash MI, Arshavsky VY. The Role of Peripherin-2/ROM1 Complexes in Photoreceptor Outer Segment Disc Morphogenesis. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1415:277-281. [PMID: 37440045 DOI: 10.1007/978-3-031-27681-1_40] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/14/2023]
Abstract
The light-sensitive outer segment organelle of photoreceptor cells contains a stack of hundreds of flat, disc-shaped membranes called discs. The rims of these discs contain a photoreceptor-specific tetraspanin protein peripherin-2 (also known as rds or PRPH2). Mutations in the PRPH2 gene lead to a wide variety of inherited retinal degenerations in humans. The vast majority of these mutations occur within a large, intradiscal loop of peripherin-2, known as the D2 loop. The D2 loop mediates well-established intermolecular interactions of peripherin-2 molecules among themselves and a homologous protein ROM1. These interactions lead to the formation of large, highly ordered oligomers. In this chapter, we discuss the supramolecular organization of peripherin-2/ROM1 complexes and their contribution to the process of outer segment disc morphogenesis and enclosure.
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Affiliation(s)
- Tylor R Lewis
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, USA.
| | - Muayyad R Al-Ubaidi
- Department of Biomedical Engineering, College of Engineering, University of Houston, Houston, TX, USA
- College of Optometry, University of Houston, Houston, TX, USA
| | - Muna I Naash
- Department of Biomedical Engineering, College of Engineering, University of Houston, Houston, TX, USA
- College of Optometry, University of Houston, Houston, TX, USA
| | - Vadim Y Arshavsky
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, USA
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
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12
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El Mazouni D, Gros P. Cryo-EM structures of peripherin-2 and ROM1 suggest multiple roles in photoreceptor membrane morphogenesis. SCIENCE ADVANCES 2022; 8:eadd3677. [PMID: 36351012 PMCID: PMC9645710 DOI: 10.1126/sciadv.add3677] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Accepted: 09/19/2022] [Indexed: 06/16/2023]
Abstract
Mammalian peripherin-2 (PRPH2) and rod outer segment membrane protein 1 (ROM1) are retina-specific tetraspanins that partake in the constant renewal of stacked membrane discs of photoreceptor cells that enable vision. Here, we present single-particle cryo-electron microscopy structures of solubilized PRPH2-ROM1 heterodimers and higher-order oligomers. High-risk PRPH2 and ROM1 mutations causing blindness map to the protein-dimer interface. Cysteine bridges connect dimers forming positive-curved oligomers, whereas negative-curved oligomers were observed occasionally. Hexamers and octamers exhibit a secondary micelle that envelopes four carboxyl-terminal helices, supporting a potential role in membrane remodeling. Together, the data indicate multiple structures for PRPH2-ROM1 in creating and maintaining compartmentalization of photoreceptor cells.
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Affiliation(s)
- Dounia El Mazouni
- Structural Biochemistry, Bijvoet Centre for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, Netherlands
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13
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Pöge M, Mahamid J, Imanishi SS, Plitzko JM, Palczewski K, Baumeister W. Determinants shaping the nanoscale architecture of the mouse rod outer segment. eLife 2021; 10:e72817. [PMID: 34931611 PMCID: PMC8758146 DOI: 10.7554/elife.72817] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Accepted: 12/09/2021] [Indexed: 12/02/2022] Open
Abstract
The unique membrane organization of the rod outer segment (ROS), the specialized sensory cilium of rod photoreceptor cells, provides the foundation for phototransduction, the initial step in vision. ROS architecture is characterized by a stack of identically shaped and tightly packed membrane disks loaded with the visual receptor rhodopsin. A wide range of genetic aberrations have been reported to compromise ROS ultrastructure, impairing photoreceptor viability and function. Yet, the structural basis giving rise to the remarkably precise arrangement of ROS membrane stacks and the molecular mechanisms underlying genetically inherited diseases remain elusive. Here, cryo-electron tomography (cryo-ET) performed on native ROS at molecular resolution provides insights into key structural determinants of ROS membrane architecture. Our data confirm the existence of two previously observed molecular connectors/spacers which likely contribute to the nanometer-scale precise stacking of the ROS disks. We further provide evidence that the extreme radius of curvature at the disk rims is enforced by a continuous supramolecular assembly composed of peripherin-2 (PRPH2) and rod outer segment membrane protein 1 (ROM1) oligomers. We suggest that together these molecular assemblies constitute the structural basis of the highly specialized ROS functional architecture. Our Cryo-ET data provide novel quantitative and structural information on the molecular architecture in ROS and substantiate previous results on proposed mechanisms underlying pathologies of certain PRPH2 mutations leading to blindness.
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Affiliation(s)
- Matthias Pöge
- Max Planck Institute of Biochemistry, Department of Molecular Structural BiologyMartinsriedGermany
| | - Julia Mahamid
- Max Planck Institute of Biochemistry, Department of Molecular Structural BiologyMartinsriedGermany
| | - Sanae S Imanishi
- Eugene and Marilyn Glick Eye Institute and the Department of Ophthalmology, Indiana University School of MedicineyIndianapolisUnited States
| | - Jürgen M Plitzko
- Max Planck Institute of Biochemistry, Department of Molecular Structural BiologyMartinsriedGermany
| | - Krzysztof Palczewski
- Gavin Herbert Eye Institute and the Department of Ophthalmology, Center for Translational Vision Research, Department of Physiology & Biophysics, Department of Chemistry, Department of Molecular Biology and BiochemistryIrvineUnited States
| | - Wolfgang Baumeister
- Max Planck Institute of Biochemistry, Department of Molecular Structural BiologyMartinsriedGermany
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14
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Lewis TR, Makia MS, Castillo CM, Al-Ubaidi MR, Naash MI, Arshavsky VY. Photoreceptor Disc Enclosure Is Tightly Controlled by Peripherin-2 Oligomerization. J Neurosci 2021; 41:3588-3596. [PMID: 33707293 PMCID: PMC8055076 DOI: 10.1523/jneurosci.0041-21.2021] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Revised: 02/15/2021] [Accepted: 03/05/2021] [Indexed: 11/21/2022] Open
Abstract
Mutations in the PRPH2 gene encoding the photoreceptor-specific protein PRPH2 (also known as peripherin-2 or rds) cause a broad range of autosomal dominant retinal diseases. Most of these mutations affect the structure of the light-sensitive photoreceptor outer segment, which is composed of a stack of flattened "disc" membranes surrounded by the plasma membrane. The outer segment is renewed on a daily basis in a process whereby new discs are added at the outer segment base and old discs are shed at the outer segment tip. New discs are formed as serial membrane evaginations, which eventually enclose through a complex process of membrane remodeling (completely in rods and partially in cones). As disc enclosure proceeds, PRPH2 localizes to the rims of enclosed discs where it forms oligomers which fortify the highly curved membrane structure of these rims. In this study, we analyzed the outer segment phenotypes of mice of both sexes bearing a single copy of either the C150S or the Y141C PRPH2 mutation known to prevent or increase the degree of PRPH2 oligomerization, respectively. Strikingly, both mutations increased the number of newly forming, not-yet-enclosed discs, indicating that the precision of disc enclosure is regulated by PRPH2 oligomerization. Without tightly controlled enclosure, discs occasionally over-elongate and form large membranous "whorls" instead of disc stacks. These data show that the defects in outer segment structure arising from abnormal PRPH2 oligomerization are manifested at the stage of disc enclosure.SIGNIFICANCE STATEMENT The light-sensitive photoreceptor outer segment contains a stack of flattened "disc" membranes that are surrounded, or "enclosed," by the outer segment membrane. Disc enclosure is an adaptation increasing photoreceptor light sensitivity by facilitating the diffusion of the second messenger along the outer segment axes. However, the molecular mechanisms by which photoreceptor discs enclose within the outer segment membrane remain poorly understood. We now demonstrate that oligomers of the photoreceptor-specific protein peripherin-2, or PRPH2, play an active role in this process. We further propose that defects in disc enclosure because of abnormal PRPH2 oligomerization result in major structural abnormalities of the outer segment, ultimately leading to loss of visual function and cell degeneration in PRPH2 mutant models and human patients.
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Affiliation(s)
- Tylor R Lewis
- Department of Ophthalmology, Duke University Medical Center, Durham, North Carolina 27710
| | - Mustafa S Makia
- Department of Biomedical Engineering, University of Houston, Houston, Texas 77204
| | - Carson M Castillo
- Department of Ophthalmology, Duke University Medical Center, Durham, North Carolina 27710
| | - Muayyad R Al-Ubaidi
- Department of Biomedical Engineering, University of Houston, Houston, Texas 77204
- College of Optometry, University of Houston, Houston, Texas 77204
| | - Muna I Naash
- Department of Biomedical Engineering, University of Houston, Houston, Texas 77204
- College of Optometry, University of Houston, Houston, Texas 77204
| | - Vadim Y Arshavsky
- Department of Ophthalmology, Duke University Medical Center, Durham, North Carolina 27710
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710
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15
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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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16
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The GARP Domain of the Rod CNG Channel's β1-Subunit Contains Distinct Sites for Outer Segment Targeting and Connecting to the Photoreceptor Disk Rim. J Neurosci 2021; 41:3094-3104. [PMID: 33637563 DOI: 10.1523/jneurosci.2609-20.2021] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 01/15/2021] [Accepted: 02/18/2021] [Indexed: 11/21/2022] Open
Abstract
Vision begins when light is captured by the outer segment organelle of photoreceptor cells in the retina. Outer segments are modified cilia filled with hundreds of flattened disk-shaped membranes. Disk membranes are separated from the surrounding plasma membrane, and each membrane type has unique protein components. The mechanisms underlying this protein sorting remain entirely unknown. In this study, we investigated the outer segment delivery of the rod cyclic nucleotide-gated (CNG) channel, which is located in the outer segment plasma membrane, where it mediates the electrical response to light. Using Xenopus and mouse models of both sexes, we now show that the targeted delivery of the CNG channel to the outer segment uses the conventional secretory pathway, including protein processing in both ER and Golgi, and requires preassembly of its constituent α1 and β1 subunits. We further demonstrate that the N-terminal glutamic acid-rich protein (GARP) domain of CNGβ1 contains two distinct functional regions. The glutamic acid-rich region encodes specific information targeting the channel to rod outer segments. The adjacent proline-enriched region connects the CNG channel to photoreceptor disk rims, likely through an interaction with peripherin-2. These data reveal fine functional specializations within the structural domains of the CNG channel and suggest that its sequestration to the outer segment plasma membrane requires an interaction with peripherin-2.SIGNIFICANCE STATEMENT Neurons and other differentiated cells have a remarkable ability to deliver and organize signaling proteins at precise subcellular locations. We now report that the CNG channel, mediating the electrical response to light in rod photoreceptors, contains two specialized regions within the N terminus of its β-subunit: one responsible for delivery of this channel to the ciliary outer segment organelle and another for subsequent channel sequestration into the outer segment plasma membrane. These findings expand our understanding of the molecular specializations used by neurons to populate their critical functional compartments.
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17
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Impairments of Photoreceptor Outer Segments Renewal and Phototransduction Due to a Peripherin Rare Haplotype Variant: Insights from Molecular Modeling. Int J Mol Sci 2021; 22:ijms22073484. [PMID: 33801777 PMCID: PMC8036374 DOI: 10.3390/ijms22073484] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 03/23/2021] [Accepted: 03/25/2021] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Retinitis pigmentosa punctata albescens (RPA) is a particular form of retinitis pigmentosa characterized by childhood onset night blindness and areas of peripheral retinal atrophy. We investigated the genetic cause of RPA in a family consisting of two affected Egyptian brothers with healthy consanguineous parents. METHODS Mutational analysis of four RPA causative genes was realized by Sanger sequencing on both probands, and detected variants were subsequently genotyped in their parents. Afterwards, found variants were deeply, statistically, and in silico characterized to determine their possible effects and association with RPA. RESULTS Both brothers carry three missense PRPH2 variants in a homozygous condition (c.910C > A, c.929G > A, and c.1013A > C) and two promoter variants in RHO (c.-26A > G) and RLBP1 (c.-70G > A) genes, respectively. Haplotype analyses highlighted a PRPH2 rare haplotype variant (GAG), determining a possible alteration of PRPH2 binding with melanoregulin and other outer segment proteins, followed by photoreceptor outer segment instability. Furthermore, an altered balance of transcription factor binding sites, due to the presence of RHO and RLBP1 promoter variants, might determine a comprehensive downregulation of both genes, possibly altering the PRPH2 shared visual-related pathway. CONCLUSIONS Despite several limitations, the study might be a relevant step towards detection of novel scenarios in RPA etiopathogenesis.
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18
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Barnes CL, Malhotra H, Calvert PD. Compartmentalization of Photoreceptor Sensory Cilia. Front Cell Dev Biol 2021; 9:636737. [PMID: 33614665 PMCID: PMC7889997 DOI: 10.3389/fcell.2021.636737] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 01/07/2021] [Indexed: 12/12/2022] Open
Abstract
Functional compartmentalization of cells is a universal strategy for segregating processes that require specific components, undergo regulation by modulating concentrations of those components, or that would be detrimental to other processes. Primary cilia are hair-like organelles that project from the apical plasma membranes of epithelial cells where they serve as exclusive compartments for sensing physical and chemical signals in the environment. As such, molecules involved in signal transduction are enriched within cilia and regulating their ciliary concentrations allows adaptation to the environmental stimuli. The highly efficient organization of primary cilia has been co-opted by major sensory neurons, olfactory cells and the photoreceptor neurons that underlie vision. The mechanisms underlying compartmentalization of cilia are an area of intense current research. Recent findings have revealed similarities and differences in molecular mechanisms of ciliary protein enrichment and its regulation among primary cilia and sensory cilia. Here we discuss the physiological demands on photoreceptors that have driven their evolution into neurons that rely on a highly specialized cilium for signaling changes in light intensity. We explore what is known and what is not known about how that specialization appears to have driven unique mechanisms for photoreceptor protein and membrane compartmentalization.
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Affiliation(s)
| | | | - Peter D. Calvert
- Department of Ophthalmology and Visual Sciences, Center for Vision Research, SUNY Upstate Medical University, Syracuse, NY, United States
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19
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Strayve D, Makia MS, Kakakhel M, Sakthivel H, Conley SM, Al-Ubaidi MR, Naash MI. ROM1 contributes to phenotypic heterogeneity in PRPH2-associated retinal disease. Hum Mol Genet 2020; 29:2708-2722. [PMID: 32716032 DOI: 10.1093/hmg/ddaa160] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 07/03/2020] [Accepted: 07/16/2020] [Indexed: 11/14/2022] Open
Abstract
Peripherin 2 (PRPH2) is a retina-specific tetraspanin protein essential for the formation of rod and cone photoreceptor outer segments (OS). Patients with mutations in PRPH2 exhibit severe retinal degeneration characterized by vast inter- and intra-familial phenotypic heterogeneity. To help understand contributors to this within-mutation disease variability, we asked whether the PRPH2 binding partner rod OS membrane protein 1 (ROM1) could serve as a phenotypic modifier. We utilized knockin and transgenic mouse models to evaluate the structural, functional and biochemical effects of eliminating one allele of Rom1 (Rom1+/-) in three different Prph2 models which mimic human disease: C213Y Prph2 (Prph2C/+), K153Del Prph2 (Prph2K/+) and R172W (Prph2R172W). Reducing Rom1 in the absence of Prph2 mutations (Rom1+/-) had no effect on retinal structure or function. However, the effects of reducing Rom1 in the presence of Prph2 mutations were highly variable. Prph2K/+/Rom1+/- mice had improved rod and cone function compared with Prph2K/+ as well as amelioration of K153Del-associated defects in PRPH2/ROM1 oligomerization. In contrast, Prph2R172W/Rom1+/- animals had worsened rod and cone function and exacerbated retinal degeneration compared with Prph2R172W animals. Removing one allele of Rom1 had no effect in Prph2C/+. Combined, our findings support a role for non-pathogenic ROM1 null variants in contributing to phenotypic variability in mutant PRPH2-associated retinal degeneration. Since the effects of Rom1 reduction are variable, our data suggest that this contribution is specific to the type of Prph2 mutation.
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Affiliation(s)
- Daniel Strayve
- Department of Biomedical Engineering, University of Houston, Houston, TX 77204, USA
| | - Mustafa S Makia
- Department of Biomedical Engineering, University of Houston, Houston, TX 77204, USA
| | - Mashal Kakakhel
- Department of Biomedical Engineering, University of Houston, Houston, TX 77204, USA
| | - Haarthi Sakthivel
- Department of Biomedical Engineering, University of Houston, Houston, TX 77204, USA
| | - Shannon M Conley
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.,Oklahoma Center for Neurosciences, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Muayyad R Al-Ubaidi
- Department of Biomedical Engineering, University of Houston, Houston, TX 77204, USA.,College of Optometry, University of Houston, Houston, TX 77004, USA.,Depatment of Biology and Biochemistry, University of Houston, Houston, TX 77204-5001, USA
| | - Muna I Naash
- Department of Biomedical Engineering, University of Houston, Houston, TX 77204, USA.,College of Optometry, University of Houston, Houston, TX 77004, USA.,Depatment of Biology and Biochemistry, University of Houston, Houston, TX 77204-5001, USA
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20
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Spencer WJ, Lewis TR, Pearring JN, Arshavsky VY. Photoreceptor Discs: Built Like Ectosomes. Trends Cell Biol 2020; 30:904-915. [PMID: 32900570 DOI: 10.1016/j.tcb.2020.08.005] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Revised: 08/05/2020] [Accepted: 08/11/2020] [Indexed: 01/22/2023]
Abstract
The light-sensitive outer segment organelle of the vertebrate photoreceptor cell is a modified cilium filled with hundreds of flattened 'disc' membranes that provide vast light-absorbing surfaces. The outer segment is constantly renewed with new discs added at its base every day. This continuous process is essential for photoreceptor viability. In this review, we describe recent breakthroughs in the understanding of disc morphogenesis, with a focus on the molecular mechanisms responsible for initiating disc formation from the ciliary membrane. We highlight the discoveries that this mechanism evolved from an innate ciliary process of releasing small extracellular vesicles, or ectosomes, and that both disc formation and ectosome release rely on the actin cytoskeleton.
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Affiliation(s)
- William J Spencer
- Albert Eye Research Institute, Duke University Medical Center, Durham, NC 27710, USA
| | - Tylor R Lewis
- Albert Eye Research Institute, Duke University Medical Center, Durham, NC 27710, USA
| | - Jillian N Pearring
- Department of Ophthalmology, University of Michigan, Ann Arbor, MI 48105, USA; Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI 48105, USA
| | - Vadim Y Arshavsky
- Albert Eye Research Institute, Duke University Medical Center, Durham, NC 27710, USA.
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21
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Park JY, Joo K, Woo SJ. Ophthalmic Manifestations and Genetics of the Polyglutamine Autosomal Dominant Spinocerebellar Ataxias: A Review. Front Neurosci 2020; 14:892. [PMID: 32973440 PMCID: PMC7472957 DOI: 10.3389/fnins.2020.00892] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Accepted: 07/30/2020] [Indexed: 12/20/2022] Open
Abstract
Spinocerebellar ataxia (SCA) is a part of the cerebellar neurodegenerative disease group that is diverse in genetics and phenotypes. It usually shows autosomal dominant inheritance. SCAs, always together with the cerebellar degeneration, may exhibit clinical deficits in brainstem or eye, especially retina or optic nerve. Interestingly, autosomal dominant SCAs share a common genetic mechanism; the length of the glutamine chain is abnormally expanded due to the increase in the cytosine–adenine–guanine (CAG) repeats of the disease causing gene. Studies have suggested that the mutant ataxin induces alteration of protein conformation and abnormal aggregation resulting in nuclear inclusions, and causes cellular loss of photoreceptors through a toxic effect. As a result, these pathologic changes induce a downregulation of genes involved in the phototransduction, development, and differentiation of photoreceptors such as CRX, one of the photoreceptor transcription factors. However, the exact mechanism of neuronal degeneration by mutant ataxin restricted to only certain type of neuronal cell including cerebellar Purkinje neurons and photoreceptor is still unclear. The most common SCAs are types 1, 2, 3, 6, 7, and 17 which contain about 80% of autosomal dominant SCA cases. Various aspects of eye movement abnormalities are evident depending on the degree of cerebellar and brainstem degeneration in SCAs. In addition, certain types of SCAs such as SCA7 are characterized by both cerebellar ataxia and visual loss mainly due to retinal degeneration. The severity of the retinopathy can vary from occult macular photoreceptor disruption to extensive retinal atrophy and is correlated with the number of CAG repeats. The value of using optical coherence tomography in conjunction with electrodiagnostic and genetic testing is emphasized as the combination of these tests can provide critical information regarding the etiology, morphological evaluation, and functional significances. Therefore, ophthalmologists need to recognize and differentiate SCAs in order to properly diagnose and evaluate the disease. In this review, we have described and discussed SCAs showing ophthalmic abnormalities with particular attention to their ophthalmic features, neurodegenerative mechanisms, genetics, and future perspectives.
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Affiliation(s)
- Jun Young Park
- Department of Ophthalmology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seoul, South Korea
| | - Kwangsic Joo
- Department of Ophthalmology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seoul, South Korea
| | - Se Joon Woo
- Department of Ophthalmology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seoul, South Korea
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22
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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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23
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Chen HY, Kelley RA, Li T, Swaroop A. Primary cilia biogenesis and associated retinal ciliopathies. Semin Cell Dev Biol 2020; 110:70-88. [PMID: 32747192 PMCID: PMC7855621 DOI: 10.1016/j.semcdb.2020.07.013] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 07/14/2020] [Accepted: 07/18/2020] [Indexed: 12/19/2022]
Abstract
The primary cilium is a ubiquitous microtubule-based organelle that senses external environment and modulates diverse signaling pathways in different cell types and tissues. The cilium originates from the mother centriole through a complex set of cellular events requiring hundreds of distinct components. Aberrant ciliogenesis or ciliary transport leads to a broad spectrum of clinical entities with overlapping yet highly variable phenotypes, collectively called ciliopathies, which include sensory defects and syndromic disorders with multi-organ pathologies. For efficient light detection, photoreceptors in the retina elaborate a modified cilium known as the outer segment, which is packed with membranous discs enriched for components of the phototransduction machinery. Retinopathy phenotype involves dysfunction and/or degeneration of the light sensing photoreceptors and is highly penetrant in ciliopathies. This review will discuss primary cilia biogenesis and ciliopathies, with a focus on the retina, and the role of CP110-CEP290-CC2D2A network. We will also explore how recent technologies can advance our understanding of cilia biology and discuss new paradigms for developing potential therapies of retinal ciliopathies.
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Affiliation(s)
- Holly Y Chen
- Neurobiology, Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, MSC0610, 6 Center Drive, Bethesda, MD 20892, USA.
| | - Ryan A Kelley
- Neurobiology, Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, MSC0610, 6 Center Drive, Bethesda, MD 20892, USA
| | - Tiansen Li
- Neurobiology, Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, MSC0610, 6 Center Drive, Bethesda, MD 20892, USA
| | - Anand Swaroop
- Neurobiology, Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, MSC0610, 6 Center Drive, Bethesda, MD 20892, USA.
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24
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Oertel FC, Zeitz O, Rönnefarth M, Bereuter C, Motamedi S, Zimmermann HG, Kuchling J, Grosch AS, Doss S, Browne A, Paul F, Schmitz-Hübsch T, Brandt AU. Functionally Relevant Maculopathy and Optic Atrophy in Spinocerebellar Ataxia Type 1. Mov Disord Clin Pract 2020; 7:502-508. [PMID: 32626794 PMCID: PMC7328427 DOI: 10.1002/mdc3.12949] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Revised: 02/19/2020] [Accepted: 03/08/2020] [Indexed: 12/16/2022] Open
Abstract
Background Spinocerebellar ataxia type 1 (SCA-ATXN1) is an inherited progressive ataxia disorder characterized by an adult-onset cerebellar syndrome combined with nonataxia signs. Retinal or optic nerve affection are not systematically described. Objectives To describe a retinal phenotype and its functional relevance in SCA-ATXN1. Methods We applied optical coherence tomography (OCT) in 20 index cases with SCA-ATXN1 and 22 healthy controls (HCs), investigating qualitative changes and quantifying the peripapillary retinal nerve fiber layer (pRNFL) thickness and combined ganglion cell and inner plexiform layer (GCIP) volume as markers of optic atrophy and outer retinal layers as markers of maculopathy. Visual function was assessed by high- (HC-VA) and low-contrast visual acuity (LC-VA) and the Hardy-Rand-Rittler pseudoisochromatic test for color vision. Results Five patients (25%) showed distinct maculopathies in the ellipsoid zone (EZ). Furthermore, pRNFL (P < 0.001) and GCIP (P = 0.002) were reduced in patients (pRNFL, 80.86 ± 9.49 μm; GCIP, 1.84 ± 0.16 mm3) compared with HCs (pRNFL, 97.02 ± 8.34 μm; GCIP, 1.98 ± 0.12 mm3). Outer macular layers were similar between groups, but reduced in patients with maculopathies. HC-VA (P = 0.002) and LC-VA (P < 0.001) were reduced in patients (HC-VA [logMAR]: 0.01 ± 010; LC-VA [logMAR]: 0.44 ± 0.16) compared with HCs (HC-VA [logMAR]: -0.12 ± 0.08; LC-VA [logMAR]: 0.25 ± 0.05). Color vision was abnormal in 2 patients with maculopathies. Conclusions A distinct maculopathy, termed EZ disruption, as well as optic atrophy add to the known nonataxia features in SCA-ATXN1. Whereas optic atrophy may be understood as part of a widespread neurodegeneration, EZ disruption may be explained by effects of ataxin-1 gene or protein on photoreceptors. Our findings extend the spectrum of nonataxia signs in SCA-ATXN1 with potential relevance for diagnosis and monitoring.
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Affiliation(s)
- Frederike Cosima Oertel
- Experimental and Clinical Research Center, Max-Delbrück-Centrum für Molekulare Medizin and Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin Humboldt-Universität zu Berlin, and Berlin Institute of Health Berlin Germany.,NeuroCure Clinical Research Center, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin Humboldt-Universität zu Berlin, and Berlin Institute of Health Berlin Germany
| | - Oliver Zeitz
- Department of Ophthalmology, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin Humboldt-Universität zu Berlin, and Berlin Institute of Health Berlin Germany
| | - Maria Rönnefarth
- Department of Neurology, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin Humboldt-Universität zu Berlin, and Berlin Institute of Health Berlin Germany
| | - Charlotte Bereuter
- Experimental and Clinical Research Center, Max-Delbrück-Centrum für Molekulare Medizin and Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin Humboldt-Universität zu Berlin, and Berlin Institute of Health Berlin Germany.,NeuroCure Clinical Research Center, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin Humboldt-Universität zu Berlin, and Berlin Institute of Health Berlin Germany
| | - Seyedamirhosein Motamedi
- Experimental and Clinical Research Center, Max-Delbrück-Centrum für Molekulare Medizin and Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin Humboldt-Universität zu Berlin, and Berlin Institute of Health Berlin Germany.,NeuroCure Clinical Research Center, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin Humboldt-Universität zu Berlin, and Berlin Institute of Health Berlin Germany
| | - Hanna G Zimmermann
- Experimental and Clinical Research Center, Max-Delbrück-Centrum für Molekulare Medizin and Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin Humboldt-Universität zu Berlin, and Berlin Institute of Health Berlin Germany.,NeuroCure Clinical Research Center, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin Humboldt-Universität zu Berlin, and Berlin Institute of Health Berlin Germany
| | - Joseph Kuchling
- Experimental and Clinical Research Center, Max-Delbrück-Centrum für Molekulare Medizin and Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin Humboldt-Universität zu Berlin, and Berlin Institute of Health Berlin Germany.,NeuroCure Clinical Research Center, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin Humboldt-Universität zu Berlin, and Berlin Institute of Health Berlin Germany.,Department of Neurology, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin Humboldt-Universität zu Berlin, and Berlin Institute of Health Berlin Germany
| | - Anne Sophie Grosch
- Department of Neurology, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin Humboldt-Universität zu Berlin, and Berlin Institute of Health Berlin Germany
| | - Sarah Doss
- Department of Neurology, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin Humboldt-Universität zu Berlin, and Berlin Institute of Health Berlin Germany.,Department of Neurological Sciences University of Nebraska Medical Center Nebraska Omaha USA
| | - Andrew Browne
- Department of Ophthalmology University of California Irvine Irvine California USA
| | - Friedemann Paul
- Experimental and Clinical Research Center, Max-Delbrück-Centrum für Molekulare Medizin and Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin Humboldt-Universität zu Berlin, and Berlin Institute of Health Berlin Germany.,NeuroCure Clinical Research Center, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin Humboldt-Universität zu Berlin, and Berlin Institute of Health Berlin Germany.,Department of Neurology, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin Humboldt-Universität zu Berlin, and Berlin Institute of Health Berlin Germany
| | - Tanja Schmitz-Hübsch
- Experimental and Clinical Research Center, Max-Delbrück-Centrum für Molekulare Medizin and Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin Humboldt-Universität zu Berlin, and Berlin Institute of Health Berlin Germany.,NeuroCure Clinical Research Center, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin Humboldt-Universität zu Berlin, and Berlin Institute of Health Berlin Germany
| | - Alexander U Brandt
- Experimental and Clinical Research Center, Max-Delbrück-Centrum für Molekulare Medizin and Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin Humboldt-Universität zu Berlin, and Berlin Institute of Health Berlin Germany.,NeuroCure Clinical Research Center, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin Humboldt-Universität zu Berlin, and Berlin Institute of Health Berlin Germany.,Department of Neurology University of California Irvine Irvine California USA
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25
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Lewis TR, Makia MS, Kakakhel M, Al-Ubaidi MR, Arshavsky VY, Naash MI. Photoreceptor Disc Enclosure Occurs in the Absence of Normal Peripherin-2/rds Oligomerization. Front Cell Neurosci 2020; 14:92. [PMID: 32410962 PMCID: PMC7198881 DOI: 10.3389/fncel.2020.00092] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Accepted: 03/30/2020] [Indexed: 12/11/2022] Open
Abstract
Mutations in the peripherin-2 gene (PRPH2, also known as rds) cause a heterogeneous range of autosomal dominant retinal diseases. PRPH2 encodes a photoreceptor-specific tetraspanin protein, PRPH2, that is a main structural component of the photoreceptor outer segment. PRPH2 distributes to the rims of outer segment disc membranes as they undergo the process of disc membrane enclosure. Within these rims, PRPH2 exists in homo-oligomeric form or as a hetero-oligomer with another tetraspanin protein, ROM1. While complete loss of PRPH2 prevents photoreceptor outer segment formation, mutations affecting the state of its oligomerization, including C150S, C213Y and Y141C, produce outer segment structural defects. In this study, we addressed whether any of these mutations also affect disc enclosure. We employed recently developed methodology for ultrastructural analysis of the retina, involving tissue processing with tannic acid, to assess the status of disc enclosure in knockin mouse models bearing either one or two alleles of the C150S, C213Y and Y141C PRPH2 mutations. While varying degrees of outer segment structural abnormalities were observed in each of these mouse models, they contained both newly forming “open” discs and mature “enclosed” discs. These data demonstrate that normal PRPH2 oligomerization is not essential for photoreceptor disc enclosure.
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Affiliation(s)
- Tylor R Lewis
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, United States
| | - Mustafa S Makia
- Department of Biomedical Engineering, University of Houston, Houston, TX, United States
| | - Mashal Kakakhel
- Department of Biomedical Engineering, University of Houston, Houston, TX, United States
| | - Muayyad R Al-Ubaidi
- Department of Biomedical Engineering, University of Houston, Houston, TX, United States.,College of Optometry, University of Houston, Houston, TX, United States
| | - Vadim Y Arshavsky
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, United States.,Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, United States
| | - Muna I Naash
- Department of Biomedical Engineering, University of Houston, Houston, TX, United States.,College of Optometry, University of Houston, Houston, TX, United States
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26
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Tebbe L, Kakakhel M, Makia MS, Al-Ubaidi MR, Naash MI. The Interplay between Peripherin 2 Complex Formation and Degenerative Retinal Diseases. Cells 2020; 9:E784. [PMID: 32213850 PMCID: PMC7140794 DOI: 10.3390/cells9030784] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 03/11/2020] [Accepted: 03/20/2020] [Indexed: 12/17/2022] Open
Abstract
Peripherin 2 (Prph2) is a photoreceptor-specific tetraspanin protein present in the outer segment (OS) rims of rod and cone photoreceptors. It shares many common features with other tetraspanins, including a large intradiscal loop which contains several cysteines. This loop enables Prph2 to associate with itself to form homo-oligomers or with its homologue, rod outer segment membrane protein 1 (Rom1) to form hetero-tetramers and hetero-octamers. Mutations in PRPH2 cause a multitude of retinal diseases including autosomal dominant retinitis pigmentosa (RP) or cone dominant macular dystrophies. The importance of Prph2 for photoreceptor development, maintenance and function is underscored by the fact that its absence results in a failure to initialize OS formation in rods and formation of severely disorganized OS membranous structures in cones. Although the exact role of Rom1 has not been well studied, it has been concluded that it is not necessary for disc morphogenesis but is required for fine tuning OS disc size and structure. Pathogenic mutations in PRPH2 often result in complex and multifactorial phenotypes, involving not just photoreceptors, as has historically been reasoned, but also secondary effects on the retinal pigment epithelium (RPE) and retinal/choroidal vasculature. The ability of Prph2 to form complexes was identified as a key requirement for the development and maintenance of OS structure and function. Studies using mouse models of pathogenic Prph2 mutations established a connection between changes in complex formation and disease phenotypes. Although progress has been made in the development of therapeutic approaches for retinal diseases in general, the highly complex interplay of functions mediated by Prph2 and the precise regulation of these complexes made it difficult, thus far, to develop a suitable Prph2-specific therapy. Here we describe the latest results obtained in Prph2-associated research and how mouse models provided new insights into the pathogenesis of its related diseases. Furthermore, we give an overview on the current status of the development of therapeutic solutions.
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Affiliation(s)
| | | | | | - Muayyad R. Al-Ubaidi
- Department of Biomedical Engineering, University of Houston, Houston, TX 77204, USA; (L.T.); (M.K.); (M.S.M.)
| | - Muna I. Naash
- Department of Biomedical Engineering, University of Houston, Houston, TX 77204, USA; (L.T.); (M.K.); (M.S.M.)
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27
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Dong K, Xue H, Cheng J, Su J, Li D, Zhang J, Zhang H. PRPH2 Activates Hippo Signalling and Suppresses the Invasion and Anoikis Inhibition of Laryngeal Cancer. Cancer Manag Res 2019; 11:10107-10115. [PMID: 31819643 PMCID: PMC6896914 DOI: 10.2147/cmar.s222527] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Accepted: 11/12/2019] [Indexed: 01/08/2023] Open
Abstract
Introduction Laryngeal cancer is the most common head and neck cancer worldwide. It is urgent to identify the mechanisms underlying laryngeal cancer pathogenesis. In the present study, we investigated the biological functions of Peripherin 2 (PRPH2) in laryngeal cancer and uncovered the molecular mechanism underlying this disease. Methods Laryngeal cancer tissues were used to analyze the expression of PRPH2. In vitro transwell matrigel invasion assay and annexin V anoikis assay in laryngeal cancer cells were conducted to investigate PRPH2 related biological functions. Quantitative real-time PCR and Western blotting were performed to investigate the expression and mechanism of PRPH2 in laryngeal cancer. Results We found that the expression of PRPH2 was significantly downregulated in laryngeal cancer tissues. Overexpression of PRPH2 suppressed the invasion and anoikis inhibition of laryngeal cancer cells. Furthermore, PRPH2 overexpression increased the phosphorylation of YAP and LATS1 and decreased the activities of Rho GTPases, while PRPH2 knockdown had opposite effects. Inhibitors of the Hippo pathway abrogated PRPH2 knockdown-induced laryngeal cancer cell invasion and anoikis inhibition. Discussion These results suggested that PRPH2 suppresses laryngeal cancer cell invasion and anoikis inhibition by activating Hippo signalling. PRPH2 may serve as a potential therapeutic target for laryngeal cancer in the future.
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Affiliation(s)
- KaiFeng Dong
- Department of Ear-Nose-Throat, The First Hospital of Hebei Medical University, Shijiazhuang, Hebei 050031, People's Republic of China
| | - HaiTao Xue
- Department of Ear-Nose-Throat, The First Hospital of Hebei Medical University, Shijiazhuang, Hebei 050031, People's Republic of China
| | - JianGang Cheng
- Department of Ear-Nose-Throat, Shijiazhuang Ping'an Hospital, Shijiazhuang, Hebei 050021, People's Republic of China
| | - Jing Su
- Department of Ear-Nose-Throat, The First Hospital of Hebei Medical University, Shijiazhuang, Hebei 050031, People's Republic of China
| | - Dan Li
- Department of Ear-Nose-Throat, The First Hospital of Hebei Medical University, Shijiazhuang, Hebei 050031, People's Republic of China
| | - JiHua Zhang
- Department of Ear-Nose-Throat, The First Hospital of Hebei Medical University, Shijiazhuang, Hebei 050031, People's Republic of China
| | - HaoLei Zhang
- Department of Ear-Nose-Throat, The First Hospital of Hebei Medical University, Shijiazhuang, Hebei 050031, People's Republic of China
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