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Castillo García M, Urdapilleta E. A dynamical adaptation model of visual spatiotemporal processing in cones and horizontal cells. Math Biosci 2023; 366:109104. [PMID: 37918478 DOI: 10.1016/j.mbs.2023.109104] [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: 09/14/2023] [Revised: 10/26/2023] [Accepted: 10/29/2023] [Indexed: 11/04/2023]
Abstract
In this work, we introduce a phenomenological model for the cone-horizontal cell assembly, including spatial integration and formation of receptive field-like structures. The model extends our previous dynamical adaptation description with gain control accounting for processes in single cones, valid in severe nonlinear regimes. Here, a spatially extended feedback mechanism is introduced from horizontal cells to cones to account for experimental evidence, contributing thus to the development of a center-surround receptive field in cones and downstream bipolar cells. Feedback gain is defined on different spatial scales by weighting spatial filters: a short scale accounting for cone input to the feedback mechanism and a large scale driven by the syncytium characteristics of horizontal cells. A third spatial scale improves the description, mimicking neighboring cone-cone coupling. This overall spatial integration couples to temporal signal processing, thus obtaining a spatiotemporal model of outer retina responses capable of reproducing nonlinear features in both dimensions (space and time). The model was tested and validated using measurements on horizontal cells from different studies, with excellent performance. By its phenomenological nature, signal processing properties are inferred from model parameters. The model can be used in arrays of processing units with more complex incoming patterns of visual stimuli.
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Affiliation(s)
- Miguel Castillo García
- Centro Atómico Bariloche and Instituto Balseiro, Comisión Nacional de Energía Atómica (CNEA), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Cuyo, Av. E. Bustillo 9500, R8402AGP San Carlos de Bariloche, Río Negro, Argentina
| | - Eugenio Urdapilleta
- Centro Atómico Bariloche and Instituto Balseiro, Comisión Nacional de Energía Atómica (CNEA), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Cuyo, Av. E. Bustillo 9500, R8402AGP San Carlos de Bariloche, Río Negro, Argentina.
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2
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Rodgers J, Wright P, Ballister ER, Hughes RB, Storchi R, Wynne J, Martial FP, Lucas RJ. Modulating signalling lifetime to optimise a prototypical animal opsin for optogenetic applications. Pflugers Arch 2023; 475:1387-1407. [PMID: 38036775 PMCID: PMC10730688 DOI: 10.1007/s00424-023-02879-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 11/01/2023] [Accepted: 11/02/2023] [Indexed: 12/02/2023]
Abstract
Animal opsins are light activated G-protein-coupled receptors, capable of optogenetic control of G-protein signalling for research or therapeutic applications. Animal opsins offer excellent photosensitivity, but their temporal resolution can be limited by long photoresponse duration when expressed outside their native cellular environment. Here, we explore methods for addressing this limitation for a prototypical animal opsin (human rod opsin) in HEK293T cells. We find that the application of the canonical rhodopsin kinase (GRK1)/visual arrestin signal termination mechanism to this problem is complicated by a generalised suppressive effect of GRK1 expression. This attenuation can be overcome using phosphorylation-independent mutants of arrestin, especially when these are tethered to the opsin protein. We further show that point mutations targeting the Schiff base stability of the opsin can also reduce signalling lifetime. Finally, we apply one such mutation (E122Q) to improve the temporal fidelity of restored visual responses following ectopic opsin expression in the inner retina of a mouse model of retinal degeneration (rd1). Our results reveal that these two strategies (targeting either arrestin binding or Schiff-base hydrolysis) can produce more time-delimited opsin signalling under heterologous expression and establish the potential of this approach to improve optogenetic performance.
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Affiliation(s)
- Jessica Rodgers
- Centre for Biological Timing, Division of Neuroscience, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, M13 9PT, UK.
| | - Phillip Wright
- Centre for Biological Timing, Division of Neuroscience, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, M13 9PT, UK
| | - Edward R Ballister
- Centre for Biological Timing, Division of Neuroscience, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, M13 9PT, UK
- Department of Biomedical Engineering, Columbia University, New York, NY, 10027, USA
- Department of Microbiology and Immunology, Vagelos College of Physicians and Surgeons of Columbia University, New York, 10032, NY, USA
| | - Rebecca B Hughes
- Centre for Biological Timing, Division of Neuroscience, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, M13 9PT, UK
| | - Riccardo Storchi
- Centre for Biological Timing, Division of Neuroscience, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, M13 9PT, UK
| | - Jonathan Wynne
- Centre for Biological Timing, Division of Neuroscience, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, M13 9PT, UK
| | - Franck P Martial
- Centre for Biological Timing, Division of Neuroscience, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, M13 9PT, UK
| | - Robert J Lucas
- Centre for Biological Timing, Division of Neuroscience, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, M13 9PT, UK.
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Akula JD, Lancos AM, AlWattar BK, De Bruyn H, Hansen RM, Fulton AB. A Simplified Model of Activation and Deactivation of Human Rod Phototransduction-An Electroretinographic Study. Invest Ophthalmol Vis Sci 2023; 64:36. [PMID: 37738060 PMCID: PMC10528468 DOI: 10.1167/iovs.64.12.36] [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: 06/09/2023] [Accepted: 08/28/2023] [Indexed: 09/23/2023] Open
Abstract
Purpose To test the hypothesis that a simple model having properties consistent with activation and deactivation in the rod approximates the whole time course of the photoresponse. Methods Routinely, an exponential of the form f = α·(1 - exp(-(τ·(t - teff)s-1))), with amplitude α, rate constant τ (often scaled by intensity), irreducible delay teff, and time exponent s-1, is fit to the early period of the flash electroretinogram. Notably, s (an integer) represents the three integrating stages in the rod amplification cascade (rhodopsin isomerization, transducin activation, and cGMP hydrolysis). The time course of the photoresponse to a 0.17 cd·s·m-2 conditioning flash (CF) was determined in 21 healthy eyes by presenting the CF plus a bright probe flash (PF) in tandem, separated by interstimulus intervals (ISIs) of 0.01 to 1.4 seconds, and calculating the proportion of the PF a-wave suppressed by the CF at each ISI. To test if similar kinetics describe deactivation, difference of exponential (DoE) functions with common α and teff parameters, respective rate constants for the initiation (I) and quenching (Q) phases of the response, and specified values of s (sI, sQ), were compared to the photoresponse time course. Results As hypothesized, the optimal values of sI and sQ were 3 and 2, respectively. Mean ± SD α was 0.80 ± 0.066, I was 7700 ± 2400 m2·cd-1·s-3, and Q was 1.4 ± 0.47 s-1. Overall, r2 was 0.93. Conclusions A method, including a DoE model with just three free parameters (α, I, Q), that robustly captures the magnitude and time-constants of the complete rod response, was produced. Only two steps integrate to quench the rod photoresponse.
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Affiliation(s)
- James D. Akula
- Ophthalmology, Boston Children's Hospital, Boston, Massachusetts, United States
- Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States
| | - Annie M. Lancos
- Ophthalmology, Boston Children's Hospital, Boston, Massachusetts, United States
| | - Bilal K. AlWattar
- Ophthalmology, Boston Children's Hospital, Boston, Massachusetts, United States
- Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States
| | - Hanna De Bruyn
- Ophthalmology, Boston Children's Hospital, Boston, Massachusetts, United States
| | - Ronald M. Hansen
- Ophthalmology, Boston Children's Hospital, Boston, Massachusetts, United States
- Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States
| | - Anne B. Fulton
- Ophthalmology, Boston Children's Hospital, Boston, Massachusetts, United States
- Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States
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Koch KW. Molecular tuning of calcium dependent processes by neuronal calcium sensor proteins in the retina. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2023; 1870:119491. [PMID: 37230154 DOI: 10.1016/j.bbamcr.2023.119491] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Revised: 05/04/2023] [Accepted: 05/05/2023] [Indexed: 05/27/2023]
Abstract
Vertebrate photoreceptor cells are exquisite light detectors operating under very dim and bright illumination mediated by phototransduction, which is under control of the two secondary messengers cGMP and Ca2+. Feedback mechanisms enable photoreceptor cells to regain their responsiveness after light stimulation and involve neuronal Ca2+-sensor proteins, named GCAPs (guanylate cyclase-activating proteins) and recoverins. This review compares the diversity in Ca2+-related signaling mediated by GCAP and recoverin variants that exhibit differences in Ca2+-sensing, protein conformational changes, myristoyl switch mechanisms, diversity in divalent cation binding and dimer formation. In summary, both subclasses of neuronal Ca2+-sensor proteins contribute to a complex signaling network in rod and cone cells, which is perfectly suited to match the requirements for sensitive cell responses and maintaining this responsiveness in the presence of different background light intensities.
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Affiliation(s)
- Karl-Wilhelm Koch
- Department of Neuroscience, Division of Biochemistry, University of Oldenburg, 26111 Oldenburg, Germany.
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Yee C, Görtemaker K, Wellpott R, Koch KW. Kinetics of cone specific G-protein signaling in avian photoreceptor cells. Front Mol Neurosci 2023; 16:1107025. [PMID: 36733826 PMCID: PMC9887155 DOI: 10.3389/fnmol.2023.1107025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Accepted: 01/03/2023] [Indexed: 01/19/2023] Open
Abstract
Cone photoreceptor cells of night-migratory songbirds seem to process the primary steps of two different senses, vision and magnetoreception. The molecular basis of phototransduction is a prototypical G protein-coupled receptor pathway starting with the photoexcitation of rhodopsin or cone opsin thereby activating a heterotrimeric G protein named transducin. This interaction is well understood in vertebrate rod cells, but parameter describing protein-protein interactions of cone specific proteins are rare and not available for migratory birds. European robin is a model organism for studying the orientation of birds in the earth magnetic field. Recent findings showed a link between the putative magnetoreceptor cryptochrome 4a and the cone specific G-protein of European robin. In the present work, we investigated the interaction of European robin cone specific G protein and cytoplasmic regions of long wavelength opsin. We identified the second loop in opsin connecting transmembrane regions three and four as a critical binding interface. Surface plasmon resonance studies using a synthetic peptide representing the second cytoplasmic loop and purified G protein α-subunit showed a high affinity interaction with a K D value of 21 nM. Truncation of the G protein α-subunit at the C-terminus by six amino acids slightly decreased the affinity. Our results suggest that binding of the G protein to cryptochrome can compete with the interaction of G protein and non-photoexcited long wavelength opsin. Thus, the parallel presence of two different sensory pathways in bird cone photoreceptors is reasonable under dark-adapted conditions or during illumination with short wavelengths.
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Affiliation(s)
- Chad Yee
- Division of Biochemistry, Department of Neuroscience, University of Oldenburg, Oldenburg, Germany
| | - Katharina Görtemaker
- Division of Biochemistry, Department of Neuroscience, University of Oldenburg, Oldenburg, Germany
| | - Rieke Wellpott
- Division of Biochemistry, Department of Neuroscience, University of Oldenburg, Oldenburg, Germany
| | - Karl-Wilhelm Koch
- Division of Biochemistry, Department of Neuroscience, University of Oldenburg, Oldenburg, Germany,Research Center Neurosensory Sciences, University of Oldenburg, Oldenburg, Germany,*Correspondence: Karl-Wilhelm Koch, ✉
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Caruso G, Klaus C, Hamm HE, Gurevich VV, Bisegna P, Andreucci D, DiBenedetto E, Makino CL. Pepperberg plot: Modeling flash response saturation in retinal rods of mouse. Front Mol Neurosci 2023; 15:1054449. [PMID: 36710929 PMCID: PMC9880052 DOI: 10.3389/fnmol.2022.1054449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Accepted: 11/09/2022] [Indexed: 01/15/2023] Open
Abstract
Retinal rods evolved to be able to detect single photons. Despite their exquisite sensitivity, rods operate over many log units of light intensity. Several processes inside photoreceptor cells make this incredible light adaptation possible. Here, we added to our previously developed, fully space resolved biophysical model of rod phototransduction, some of the mechanisms that play significant roles in shaping the rod response under high illumination levels: the function of RGS9 in shutting off G protein transducin, and calcium dependences of the phosphorylation rates of activated rhodopsin, of the binding of cGMP to the light-regulated ion channel, and of two membrane guanylate cyclase activities. A well stirred version of this model captured the responses to bright, saturating flashes in WT and mutant mouse rods and was used to explain "Pepperberg plots," that graph the time during which the response is saturated against the natural logarithm of flash strength for bright flashes. At the lower end of the range, saturation time increases linearly with the natural logarithm of flash strength. The slope of the relation (τD) is dictated by the time constant of the rate-limiting (slowest) step in the shutoff of the phototransduction cascade, which is the hydrolysis of GTP by transducin. We characterized mathematically the X-intercept ( Φ o ) which is the number of photoisomerizations that just saturates the rod response. It has been observed that for flash strengths exceeding a few thousand photoisomerizations, the curves depart from linearity. Modeling showed that the "upward bend" for very bright flash intensities could be explained by the dynamics of RGS9 complex and further predicted that there would be a plateau at flash strengths giving rise to more than ~107 photoisomerizations due to activation of all available PDE. The model accurately described alterations in saturation behavior of mutant murine rods resulting from transgenic perturbations of the cascade targeting membrane guanylate cyclase activity, and expression levels of GRK, RGS9, and PDE. Experimental results from rods expressing a mutant light-regulated channel purported to lack calmodulin regulation deviated from model predictions, suggesting that there were other factors at play.
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Affiliation(s)
- Giovanni Caruso
- Italian National Research Council, Istituto di Scienze del Patrimonio Culturale, Rome, Italy
| | - Colin Klaus
- The College of Public Health Division of Biostatistics and The Mathematical Biosciences Institute, The Ohio State University, Columbus, OH, United States
| | - Heidi E. Hamm
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN, United States
| | - Vsevolod V. Gurevich
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN, United States
| | - Paolo Bisegna
- Department of Civil Engineering and Computer Science, University of Rome Tor Vergata, Rome, Italy
| | - Daniele Andreucci
- Department of Basic and Applied Sciences for Engineering, Sapienza University of Rome, Rome, Italy
| | | | - Clint L. Makino
- Department of Physiology & Biophysics, Boston University Chobanian & Avedisian School of Medicine, Boston, MA, United States,*Correspondence: Clint L. Makino,
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Visual pigment-deficient cones survive and mediate visual signaling despite the lack of outer segments. Proc Natl Acad Sci U S A 2022; 119:2115138119. [PMID: 35197287 PMCID: PMC8892328 DOI: 10.1073/pnas.2115138119] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/30/2021] [Indexed: 11/18/2022] Open
Abstract
Rhodopsin and cone opsins are essential for light detection in vertebrate rods and cones, respectively. It is well established that rhodopsin is required for rod phototransduction, outer segment disk morphogenesis, and rod viability. However, the roles of cone opsins are less well understood. In this study, we adopted a loss-of-function approach to investigate the physiological roles of cone opsins in mice. We showed that cones lacking cone opsins do not form normal outer segments due to the lack of disk morphogenesis. Surprisingly, cone opsin-deficient cones survive for at least 12 mo, which is in stark contrast to the rapid rod degeneration observed in rhodopsin-deficient mice, suggesting that cone opsins are dispensable for cone viability. Although the mutant cones do not respond to light directly, they maintain a normal dark current and continue to mediate visual signaling by relaying the rod signal through rod-cone gap junctions. Our work reveals a striking difference between the role of rhodopsin and cone opsins in photoreceptor viability.
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8
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Wandell BA, Brainard DH, Cottaris NP. Visual encoding: Principles and software. PROGRESS IN BRAIN RESEARCH 2022; 273:199-229. [DOI: 10.1016/bs.pbr.2022.04.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Phototransduction in Anuran Green Rods: Origins of Extra-Sensitivity. Int J Mol Sci 2021; 22:ijms222413400. [PMID: 34948198 PMCID: PMC8707487 DOI: 10.3390/ijms222413400] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 12/06/2021] [Accepted: 12/10/2021] [Indexed: 01/13/2023] Open
Abstract
Green rods (GRs) represent a unique type of photoreceptor to be found in the retinas of anuran amphibians. These cells harbor a cone-specific blue-sensitive visual pigment but exhibit morphology of the outer segment typical for classic red rods (RRs), which makes them a perspective model object for studying cone–rod transmutation. In the present study, we performed detailed electrophysiological examination of the light sensitivity, response kinetics and parameters of discrete and continuous dark noise in GRs of the two anuran species: cane toad and marsh frog. Our results confirm that anuran GRs are highly specialized nocturnal vision receptors. Moreover, their rate of phototransduction quenching appeared to be about two-times slower than in RRs, which makes them even more efficient single photon detectors. The operating intensity ranges for two rod types widely overlap supposedly allowing amphibians to discriminate colors in the scotopic region. Unexpectedly for typical cone pigments but in line with some previous reports, the spontaneous isomerization rate of the GR visual pigment was found to be the same as for rhodopsin of RRs. Thus, our results expand the knowledge on anuran GRs and show that these are even more specialized single photon catchers than RRs, which allows us to assign them a status of “super-rods”.
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White ND, Batz ZA, Braun EL, Braun MJ, Carleton KL, Kimball RT, Swaroop A. A novel exome probe set captures phototransduction genes across birds (Aves) enabling efficient analysis of vision evolution. Mol Ecol Resour 2021; 22:587-601. [PMID: 34652059 DOI: 10.1111/1755-0998.13496] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Revised: 08/17/2021] [Accepted: 08/20/2021] [Indexed: 11/27/2022]
Abstract
The diversity of avian visual phenotypes provides a framework for studying mechanisms of trait diversification generally, and the evolution of vertebrate vision, specifically. Previous research has focused on opsins, but to fully understand visual adaptation, we must study the complete phototransduction cascade (PTC). Here, we developed a probe set that captures exonic regions of 46 genes representing the PTC and other light responses. For a subset of species, we directly compared gene capture between our probe set and low-coverage whole genome sequencing (WGS), and we discuss considerations for choosing between these methods. Finally, we developed a unique strategy to avoid chimeric assembly by using "decoy" reference sequences. We successfully captured an average of 64% of our targeted exome in 46 species across 14 orders using the probe set and had similar recovery using the WGS data. Compared to WGS or transcriptomes, our probe set: (1) reduces sequencing requirements by efficiently capturing vision genes, (2) employs a simpler bioinformatic pipeline by limiting required assembly and negating annotation, and (3) eliminates the need for fresh tissues, enabling researchers to leverage existing museum collections. We then utilized our vision exome data to identify positively selected genes in two evolutionary scenarios-evolution of night vision in nocturnal birds and evolution of high-speed vision specific to manakins (Pipridae). We found parallel positive selection of SLC24A1 in both scenarios, implicating the alteration of rod response kinetics, which could improve color discrimination in dim light conditions and/or facilitate higher temporal resolution.
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Affiliation(s)
- Noor D White
- Neurobiology Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, Maryland, USA.,Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, District of Columbia, USA.,Behavior, Ecology, Evolution and Systematics Program, University of Maryland, College Park, Maryland, USA
| | - Zachary A Batz
- Neurobiology Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Edward L Braun
- Department of Biology, University of Florida, Gainesville, Florida, USA
| | - Michael J Braun
- Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, District of Columbia, USA.,Behavior, Ecology, Evolution and Systematics Program, University of Maryland, College Park, Maryland, USA.,Department of Biology, University of Maryland, College Park, Maryland, USA
| | - Karen L Carleton
- Behavior, Ecology, Evolution and Systematics Program, University of Maryland, College Park, Maryland, USA.,Department of Biology, University of Maryland, College Park, Maryland, USA
| | - Rebecca T Kimball
- Department of Biology, University of Florida, Gainesville, Florida, USA
| | - Anand Swaroop
- Neurobiology Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, Maryland, USA
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Photoreceptor Phosphodiesterase (PDE6): Structure, Regulatory Mechanisms, and Implications for Treatment of Retinal Diseases. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1371:33-59. [PMID: 34170501 DOI: 10.1007/5584_2021_649] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The photoreceptor phosphodiesterase (PDE6) is a member of large family of Class I phosphodiesterases responsible for hydrolyzing the second messengers cAMP and cGMP. PDE6 consists of two catalytic subunits and two inhibitory subunits that form a tetrameric protein. PDE6 is a peripheral membrane protein that is localized to the signal-transducing compartment of rod and cone photoreceptors. As the central effector enzyme of the G-protein coupled visual transduction pathway, activation of PDE6 catalysis causes a rapid decrease in cGMP levels that results in closure of cGMP-gated ion channels in the photoreceptor plasma membrane. Because of its importance in the phototransduction pathway, mutations in PDE6 genes result in various retinal diseases that currently lack therapeutic treatment strategies due to inadequate knowledge of the structure, function, and regulation of this enzyme. This review focuses on recent progress in understanding the structure of the regulatory and catalytic domains of the PDE6 holoenzyme, the central role of the multi-functional inhibitory γ-subunit, the mechanism of activation by the heterotrimeric G protein, transducin, and future directions for pharmacological interventions to treat retinal degenerative diseases arising from mutations in the PDE6 genes.
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12
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A hybrid stochastic/deterministic model of single photon response and light adaptation in mouse rods. Comput Struct Biotechnol J 2021; 19:3720-3734. [PMID: 34285774 PMCID: PMC8258797 DOI: 10.1016/j.csbj.2021.06.033] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2021] [Revised: 06/19/2021] [Accepted: 06/21/2021] [Indexed: 12/02/2022] Open
Abstract
A hybrid stochastic/deterministic model of mouse rod phototransduction is presented. Rod photocurrent to photovoltage conversion in darkness is accurately characterized. Photoresponses to dim and bright stimuli and in various mutants are well reproduced. Recently debated molecular mechanisms of the phototransduction cascade are examined.
The phototransduction cascade is paradigmatic for signaling pathways initiated by G protein-coupled receptors and is characterized by a fine regulation of photoreceptor sensitivity and electrical response to a broad range of light stimuli. Here, we present a biochemically comprehensive model of phototransduction in mouse rods based on a hybrid stochastic and deterministic mathematical framework, and a quantitatively accurate description of the rod impedance in the dark. The latter, combined with novel patch clamp recordings from rod outer segments, enables the interconversion of dim flash responses between photovoltage and photocurrent and thus direct comparison with the simulations. The model reproduces the salient features of the experimental photoresponses at very dim and bright stimuli, for both normal photoreceptors and those with genetically modified cascade components. Our modelling approach recapitulates a number of recent findings in vertebrate phototransduction. First, our results are in line with the recently established requirement of dimeric activation of PDE6 by transducin and further show that such conditions can be fulfilled at the expense of a significant excess of G protein activated by rhodopsin. Secondly, simulations suggest a crucial role of the recoverin-mediated Ca2+-feedback on rhodopsin kinase in accelerating the shutoff, when light flashes are delivered in the presence of a light background. Finally, stochastic simulations suggest that transient complexes between dark rhodopsin and transducin formed prior to light stimulation increase the reproducibility of single photon responses. Current limitations of the model are likely associated with the yet unknown mechanisms governing the shutoff of the cascade.
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Key Words
- ADP, adenosine diphosphate
- ATP, adenosine-5′-triphosphate
- Arr, arrestin
- BG, background illumination
- CNG, cyclic nucleotide-gated (channel)
- CSM, completely substituted mutant of rhodopsin
- CV, coefficient of variation
- DM, deterministic model
- Dynamic modeling
- E, effector of the phototransduction cascade, activated PDE
- FFT, fast Fourier-transform
- GC, guanylate cyclase
- GCAPs, guanylate cyclase-activating proteins
- GDP, guanosine-5′-diphosphate
- GPCR, G protein-coupled receptor
- GTP, guanosine-5′-triphosphate
- Gt, G protein/transducin
- Gα, α-subunit of the G protein
- Gβγ, β- and γ-subunit of the G protein
- HSDM, hybrid stochastic/deterministic model
- Light adaptation
- MPR, multiple photon response
- PDE, phosphodiesterase 6
- Ph, photons
- Phototransduction
- R, rhodopsin
- RGS, regulator of G protein signaling
- RK, rhodopsin kinase
- ROS, rod outer segment
- Rec, recoverin
- Rn, activated rhodopsin that has been phosphorylated n times
- SD, standard deviation
- SPR, single photon response
- Stochastic simulation
- Systems biology
- TTP, time to peak
- cGMP, cyclic guanosine monophosphate
- ΔJ, photocurrent
- ΔU, photovoltage
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Abtout A, Fain G, Reingruber J. Analysis of waveform and amplitude of mouse rod and cone flash responses. J Physiol 2021; 599:3295-3312. [PMID: 33977528 DOI: 10.1113/jp281225] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Accepted: 04/28/2021] [Indexed: 12/14/2022] Open
Abstract
KEY POINTS Most vertebrate eyes have rod and cone photoreceptors, which use a signal transduction pathway consisting of many biological processes to transform light into an electrical response. We dissect and quantify the contribution of each of these processes to the photoreceptor light response by using a novel method of analysis that provides an analytical solution for the entire time course of the dim-flash light response. We find that the shape of the light response is exclusively controlled by deactivation parameters. Activation parameters scale this shape and alter the response amplitude. We show that the rising phase of the response depends on Ca2+ feedback, and we identify the deactivation parameters that control the recovery phase of the response. We devise new methods to extract values for deactivation and activation parameters from a separate analysis of response shape and response amplitude. ABSTRACT Vertebrate eyes have rod and cone photoreceptors, which use a complex transduction pathway comprising many biological processes to transform the absorption of light into an electrical response. A fundamental question in sensory transduction is how these processes contribute to the response. To study this question, we use a well-accepted phototransduction model, which we analyse with a novel method based on the log transform of the current. We derive an analytical solution that describes the entire time course of the photoreceptor response to dim flashes of light. We use this solution to dissect and quantify the contribution of each process to the response. We find that the entire dim-flash response is proportional to the flash intensity. By normalizing responses to unit amplitude, we define a waveform that is independent of the light intensity and characterizes the invariant shape of dim-flash responses. We show that this waveform is exclusively determined by deactivation rates; activation rates only scale the waveform and affect the amplitude. This analysis corrects a previous assumption that the rising phase is determined entirely by activation rates. We further show that the rising phase depends on Ca2+ feedback to the cyclase, contrary to current belief. We identify the deactivation rates that control the recovery phase of the response, and we devise new methods to extract activation and deactivation rates from an analysis of response shape and response amplitude. In summary, we provide a comprehensive understanding of how the various transduction processes produce the cellular response.
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Affiliation(s)
- Annia Abtout
- Institut de Biologie de l'École Normale Supérieure, Paris, France
| | - Gordon Fain
- Department of Integrative Biology and Physiology, University of California, Los Angeles, California, USA.,Department of Ophthalmology and Stein Eye Institute, University of California, Los Angeles, California, USA
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Leinonen H, Cheng C, Pitkänen M, Sander CL, Zhang J, Saeid S, Turunen T, Shmara A, Weiss L, Ta L, Ton T, Koskelainen A, Vargas JD, Kimonis V, Palczewski K. A p97/Valosin-Containing Protein Inhibitor Drug CB-5083 Has a Potent but Reversible Off-Target Effect on Phosphodiesterase-6. J Pharmacol Exp Ther 2021; 378:31-41. [PMID: 33931547 DOI: 10.1124/jpet.120.000486] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2020] [Accepted: 04/29/2021] [Indexed: 12/16/2022] Open
Abstract
CB-5083 is an inhibitor of p97/valosin-containing protein (VCP), for which phase I trials for cancer were terminated because of adverse effects on vision, such as photophobia and dyschromatopsia. Lower dose CB-5083 could combat inclusion body myopathy with early-onset Paget disease and frontotemporal dementia or multisystem proteinopathy caused by gain-of-function mutations in VCP. We hypothesized that the visual impairment in the cancer trial was due to CB-5083's inhibition of phosphodiesterase (PDE)-6, which mediates signal transduction in photoreceptors. To test our hypothesis, we used in vivo and ex vivo electroretinography (ERG) in mice and a PDE6 activity assay of bovine rod outer segment (ROS) extracts. Additionally, histology and optical coherence tomography were used to assess CB-5083's long-term ocular toxicity. A single administration of CB-5083 led to robust ERG signal deterioration, specifically in photoresponse kinetics. Similar recordings with known PDE inhibitors sildenafil, tadalafil, vardenafil, and zaprinast showed that only vardenafil had as strong an effect on the ERG signal in vivo as did CB-5083. In the biochemical assay, CB-5083 inhibited PDE6 activity with a potency higher than sildenafil but lower than that of vardenafil. Ex vivo ERG revealed a PDE6 inhibition constant of 80 nM for CB-5083, which is 7-fold smaller than that for sildenafil. Finally, we showed that the inhibitory effect of CB-5083 on visual function is reversible, and its chronic administration does not cause permanent retinal anomalies in aged VCP-disease model mice. Our results warrant re-evaluation of CB-5083 as a clinical therapeutic agent. We recommend preclinical ERG recordings as a routine drug safety screen. SIGNIFICANCE STATEMENT: This report supports the use of a valosin-containing protein (VCP) inhibitor drug, CB-5083, for the treatment of neuromuscular VCP disease despite CB-5083's initial clinical failure for cancer treatment due to side effects on vision. The data show that CB-5083 displays a dose-dependent but reversible inhibitory action on phosphodiesterase-6, an essential enzyme in retinal photoreceptor function, but no long-term consequences on retinal function or structure.
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Affiliation(s)
- Henri Leinonen
- Gavin Herbert Eye Institute, Department of Ophthalmology (H.L., C.L.S., J.Z., K.P.), Department of Physiology & Biophysics (K.P.), Department of Chemistry (K.P.), and Division of Genetics and Genomic Medicine, Department of Pediatrics (C.C., A.S., L.W., L.T., T.T., V.K.), University of California Irvine, Irvine, California; Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio (C.L.S.); Department of Neuroscience and Biomedical Engineering, Aalto University, Espoo, Finland (M.P., S.S., T.T., A.K.); and Cleave Therapeutics, Inc., San Francisco, California (J.D.V.)
| | - Cheng Cheng
- Gavin Herbert Eye Institute, Department of Ophthalmology (H.L., C.L.S., J.Z., K.P.), Department of Physiology & Biophysics (K.P.), Department of Chemistry (K.P.), and Division of Genetics and Genomic Medicine, Department of Pediatrics (C.C., A.S., L.W., L.T., T.T., V.K.), University of California Irvine, Irvine, California; Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio (C.L.S.); Department of Neuroscience and Biomedical Engineering, Aalto University, Espoo, Finland (M.P., S.S., T.T., A.K.); and Cleave Therapeutics, Inc., San Francisco, California (J.D.V.)
| | - Marja Pitkänen
- Gavin Herbert Eye Institute, Department of Ophthalmology (H.L., C.L.S., J.Z., K.P.), Department of Physiology & Biophysics (K.P.), Department of Chemistry (K.P.), and Division of Genetics and Genomic Medicine, Department of Pediatrics (C.C., A.S., L.W., L.T., T.T., V.K.), University of California Irvine, Irvine, California; Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio (C.L.S.); Department of Neuroscience and Biomedical Engineering, Aalto University, Espoo, Finland (M.P., S.S., T.T., A.K.); and Cleave Therapeutics, Inc., San Francisco, California (J.D.V.)
| | - Christopher L Sander
- Gavin Herbert Eye Institute, Department of Ophthalmology (H.L., C.L.S., J.Z., K.P.), Department of Physiology & Biophysics (K.P.), Department of Chemistry (K.P.), and Division of Genetics and Genomic Medicine, Department of Pediatrics (C.C., A.S., L.W., L.T., T.T., V.K.), University of California Irvine, Irvine, California; Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio (C.L.S.); Department of Neuroscience and Biomedical Engineering, Aalto University, Espoo, Finland (M.P., S.S., T.T., A.K.); and Cleave Therapeutics, Inc., San Francisco, California (J.D.V.)
| | - Jianye Zhang
- Gavin Herbert Eye Institute, Department of Ophthalmology (H.L., C.L.S., J.Z., K.P.), Department of Physiology & Biophysics (K.P.), Department of Chemistry (K.P.), and Division of Genetics and Genomic Medicine, Department of Pediatrics (C.C., A.S., L.W., L.T., T.T., V.K.), University of California Irvine, Irvine, California; Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio (C.L.S.); Department of Neuroscience and Biomedical Engineering, Aalto University, Espoo, Finland (M.P., S.S., T.T., A.K.); and Cleave Therapeutics, Inc., San Francisco, California (J.D.V.)
| | - Sama Saeid
- Gavin Herbert Eye Institute, Department of Ophthalmology (H.L., C.L.S., J.Z., K.P.), Department of Physiology & Biophysics (K.P.), Department of Chemistry (K.P.), and Division of Genetics and Genomic Medicine, Department of Pediatrics (C.C., A.S., L.W., L.T., T.T., V.K.), University of California Irvine, Irvine, California; Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio (C.L.S.); Department of Neuroscience and Biomedical Engineering, Aalto University, Espoo, Finland (M.P., S.S., T.T., A.K.); and Cleave Therapeutics, Inc., San Francisco, California (J.D.V.)
| | - Teemu Turunen
- Gavin Herbert Eye Institute, Department of Ophthalmology (H.L., C.L.S., J.Z., K.P.), Department of Physiology & Biophysics (K.P.), Department of Chemistry (K.P.), and Division of Genetics and Genomic Medicine, Department of Pediatrics (C.C., A.S., L.W., L.T., T.T., V.K.), University of California Irvine, Irvine, California; Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio (C.L.S.); Department of Neuroscience and Biomedical Engineering, Aalto University, Espoo, Finland (M.P., S.S., T.T., A.K.); and Cleave Therapeutics, Inc., San Francisco, California (J.D.V.)
| | - Alyaa Shmara
- Gavin Herbert Eye Institute, Department of Ophthalmology (H.L., C.L.S., J.Z., K.P.), Department of Physiology & Biophysics (K.P.), Department of Chemistry (K.P.), and Division of Genetics and Genomic Medicine, Department of Pediatrics (C.C., A.S., L.W., L.T., T.T., V.K.), University of California Irvine, Irvine, California; Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio (C.L.S.); Department of Neuroscience and Biomedical Engineering, Aalto University, Espoo, Finland (M.P., S.S., T.T., A.K.); and Cleave Therapeutics, Inc., San Francisco, California (J.D.V.)
| | - Lan Weiss
- Gavin Herbert Eye Institute, Department of Ophthalmology (H.L., C.L.S., J.Z., K.P.), Department of Physiology & Biophysics (K.P.), Department of Chemistry (K.P.), and Division of Genetics and Genomic Medicine, Department of Pediatrics (C.C., A.S., L.W., L.T., T.T., V.K.), University of California Irvine, Irvine, California; Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio (C.L.S.); Department of Neuroscience and Biomedical Engineering, Aalto University, Espoo, Finland (M.P., S.S., T.T., A.K.); and Cleave Therapeutics, Inc., San Francisco, California (J.D.V.)
| | - Lac Ta
- Gavin Herbert Eye Institute, Department of Ophthalmology (H.L., C.L.S., J.Z., K.P.), Department of Physiology & Biophysics (K.P.), Department of Chemistry (K.P.), and Division of Genetics and Genomic Medicine, Department of Pediatrics (C.C., A.S., L.W., L.T., T.T., V.K.), University of California Irvine, Irvine, California; Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio (C.L.S.); Department of Neuroscience and Biomedical Engineering, Aalto University, Espoo, Finland (M.P., S.S., T.T., A.K.); and Cleave Therapeutics, Inc., San Francisco, California (J.D.V.)
| | - Timothy Ton
- Gavin Herbert Eye Institute, Department of Ophthalmology (H.L., C.L.S., J.Z., K.P.), Department of Physiology & Biophysics (K.P.), Department of Chemistry (K.P.), and Division of Genetics and Genomic Medicine, Department of Pediatrics (C.C., A.S., L.W., L.T., T.T., V.K.), University of California Irvine, Irvine, California; Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio (C.L.S.); Department of Neuroscience and Biomedical Engineering, Aalto University, Espoo, Finland (M.P., S.S., T.T., A.K.); and Cleave Therapeutics, Inc., San Francisco, California (J.D.V.)
| | - Ari Koskelainen
- Gavin Herbert Eye Institute, Department of Ophthalmology (H.L., C.L.S., J.Z., K.P.), Department of Physiology & Biophysics (K.P.), Department of Chemistry (K.P.), and Division of Genetics and Genomic Medicine, Department of Pediatrics (C.C., A.S., L.W., L.T., T.T., V.K.), University of California Irvine, Irvine, California; Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio (C.L.S.); Department of Neuroscience and Biomedical Engineering, Aalto University, Espoo, Finland (M.P., S.S., T.T., A.K.); and Cleave Therapeutics, Inc., San Francisco, California (J.D.V.)
| | - Jesse D Vargas
- Gavin Herbert Eye Institute, Department of Ophthalmology (H.L., C.L.S., J.Z., K.P.), Department of Physiology & Biophysics (K.P.), Department of Chemistry (K.P.), and Division of Genetics and Genomic Medicine, Department of Pediatrics (C.C., A.S., L.W., L.T., T.T., V.K.), University of California Irvine, Irvine, California; Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio (C.L.S.); Department of Neuroscience and Biomedical Engineering, Aalto University, Espoo, Finland (M.P., S.S., T.T., A.K.); and Cleave Therapeutics, Inc., San Francisco, California (J.D.V.)
| | - Virginia Kimonis
- Gavin Herbert Eye Institute, Department of Ophthalmology (H.L., C.L.S., J.Z., K.P.), Department of Physiology & Biophysics (K.P.), Department of Chemistry (K.P.), and Division of Genetics and Genomic Medicine, Department of Pediatrics (C.C., A.S., L.W., L.T., T.T., V.K.), University of California Irvine, Irvine, California; Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio (C.L.S.); Department of Neuroscience and Biomedical Engineering, Aalto University, Espoo, Finland (M.P., S.S., T.T., A.K.); and Cleave Therapeutics, Inc., San Francisco, California (J.D.V.)
| | - Krzysztof Palczewski
- Gavin Herbert Eye Institute, Department of Ophthalmology (H.L., C.L.S., J.Z., K.P.), Department of Physiology & Biophysics (K.P.), Department of Chemistry (K.P.), and Division of Genetics and Genomic Medicine, Department of Pediatrics (C.C., A.S., L.W., L.T., T.T., V.K.), University of California Irvine, Irvine, California; Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio (C.L.S.); Department of Neuroscience and Biomedical Engineering, Aalto University, Espoo, Finland (M.P., S.S., T.T., A.K.); and Cleave Therapeutics, Inc., San Francisco, California (J.D.V.)
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15
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Functional modulation of phosphodiesterase-6 by calcium in mouse rod photoreceptors. Sci Rep 2021; 11:8938. [PMID: 33903621 PMCID: PMC8076185 DOI: 10.1038/s41598-021-88140-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Accepted: 04/07/2021] [Indexed: 02/02/2023] Open
Abstract
Phosphodiesterase-6 (PDE6) is a key protein in the G-protein cascade converting photon information to bioelectrical signals in vertebrate photoreceptor cells. Here, we demonstrate that PDE6 is regulated by calcium, contrary to the common view that PDE1 is the unique PDE class whose activity is modulated by intracellular Ca2+. To broaden the operating range of photoreceptors, mammalian rod photoresponse recovery is accelerated mainly by two calcium sensor proteins: recoverin, modulating the lifetime of activated rhodopsin, and guanylate cyclase-activating proteins (GCAPs), regulating the cGMP synthesis. We found that decreasing rod intracellular Ca2+ concentration accelerates the flash response recovery and increases the basal PDE6 activity (βdark) maximally by ~ 30% when recording local electroretinography across the rod outer segment layer from GCAPs-/- recoverin-/- mice. Our modeling shows that a similar elevation in βdark can fully explain the observed acceleration of flash response recovery in low Ca2+. Additionally, a reduction of the free Ca2+ in GCAPs-/- recoverin-/- rods shifted the inhibition constants of competitive PDE inhibitor 3-isobutyl-1-methylxanthine (IBMX) against the thermally activated and light-activated forms of PDE6 to opposite directions, indicating a complex interaction between IBMX, PDE6, and calcium. The discovered regulation of PDE6 is a previously unknown mechanism in the Ca2+-mediated modulation of rod light sensitivity.
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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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First 3D-Structural Data of Full-Length Guanylyl Cyclase 1 in Rod-Outer-Segment Preparations of Bovine Retina by Cross-Linking/Mass Spectrometry. J Mol Biol 2021; 433:166947. [PMID: 33744315 DOI: 10.1016/j.jmb.2021.166947] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Revised: 03/10/2021] [Accepted: 03/11/2021] [Indexed: 11/24/2022]
Abstract
The rod-outer-segment guanylyl cyclase 1 (ROS-GC1) is a key transmembrane protein for retinal phototransduction. Mutations of ROS-GC1 correlate with different retinal diseases that often lead to blindness. No structural data are available for ROS-GC1 so far. We performed a 3D-structural analysis of native ROS-GC1 from bovine retina by cross-linking/mass spectrometry (XL-MS) and computational modeling. Absolute quantification and activity measurements of native ROS-GC1 were performed by MS-based assays directly in bovine retina samples. Our data present the first 3D-structural analysis of active, full-length ROS-GC1 derived from bovine retina. We propose a novel domain organization for the intracellular domain ROS-GC1. Our XL-MS data of native ROS-GC1 from rod-outer-segment preparations of bovine retina agree with a dimeric architecture. Our integrated approach can serve as a blueprint for conducting 3D-structural studies of membrane proteins in their native environment.
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18
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Stockman A, Henning GB, Rider AT. Clinical vision and molecular loss: Integrating visual psychophysics with molecular genetics reveals key details of normal and abnormal visual processing. Prog Retin Eye Res 2020; 83:100937. [PMID: 33388434 DOI: 10.1016/j.preteyeres.2020.100937] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2020] [Revised: 12/11/2020] [Accepted: 12/17/2020] [Indexed: 01/08/2023]
Abstract
Over the past two decades we have developed techniques and models to investigate the ways in which known molecular defects affect visual performance. Because molecular defects in retinal signalling invariably alter the speed of visual processing, our strategy has been to measure the resulting changes in flicker sensitivity. Flicker measurements provide not only straightforward clinical assessments of visual performance but also reveal fundamental details about the functioning of both abnormal and normal visual systems. Here, we bring together our past measurements of patients with pathogenic variants in the GNAT2, RGS9, GUCA1A, RPE65, OPA1, KCNV2 and NR2E3 genes and analyse the results using a standard model of visual processing. The model treats flicker sensitivity as the result of the actions of a sequence of simple processing steps, one or more of which is altered by the genetic defect. Our analyses show that most defects slow down the visual response directly, but some speed it up. Crucially, however, other steps in the processing sequence can make compensatory adjustments to offset the abnormality. For example, if the abnormal step slows down the visual response, another step is likely to speed up or attenuate the response to rebalance system performance. Such compensatory adjustments are probably made by steps in the sequence that usually adapt to changing light levels. Our techniques and modelling also allow us to tease apart stationary and progressive effects, and the localised molecular losses help us to unravel and characterise individual steps in the normal and abnormal processing sequences.
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Affiliation(s)
- Andrew Stockman
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, EC1V 9EL, England, UK.
| | - G Bruce Henning
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, EC1V 9EL, England, UK
| | - Andrew T Rider
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, EC1V 9EL, England, UK
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Ahrens N, Elbers D, Greb H, Janssen-Bienhold U, Koch KW. Interaction of G protein-coupled receptor kinases and recoverin isoforms is determined by localization in zebrafish photoreceptors. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2020; 1868:118946. [PMID: 33385424 DOI: 10.1016/j.bbamcr.2020.118946] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Revised: 12/22/2020] [Accepted: 12/23/2020] [Indexed: 12/14/2022]
Abstract
The zebrafish retina expresses four recoverin genes (rcv1a, rcv1b, rcv2a and rcv2b) and four opsin kinase genes (grk1a, grk1b, grk7a and grk7b) coding for recoverin and G protein-coupled receptor kinase (opsin kinase) paralogs, respectively. Both protein groups are suggested to form regulatory complexes in rod and cone outer segments, but at present, we lack information about co-localization of recoverin and opsin kinases in zebrafish retinae and which protein-protein interacting pairs form. We analyzed the distribution and co-localization of recoverin and opsin kinase expression in the zebrafish retina. For this purpose, we used custom-tailored monospecific antibodies revealing that the amount of recoverin paralogs in a zebrafish retina can differ by more than one order of magnitude with the highest amount for recoverin 1a and 2b. Further, immunohistochemical labelling showed presence of recoverin 1a in all rod cell compartments, but it only co-localized with opsin kinase 1a in rod outer segments. In contrast, recoverin 2b was only detected in double cones and co-localized with opsin kinases 1b, 7a and 7b. Further, we investigated the interaction between recoverin and opsin kinase variants by surface plasmon resonance spectroscopy indicating interaction of recoverin 1a and recoverin 2b with all opsin kinases. However, binding kinetics for recoverin 1a differed from those observed with recoverin 2b that showed slower association and dissociation processes. Our results indicate diverse recoverin and opsin kinase properties due to differential expression and interaction profiles.
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Affiliation(s)
- Nicole Ahrens
- Department of Neuroscience, Division of Biochemistry, University of Oldenburg, 26111 Oldenburg, Germany
| | - Dana Elbers
- Department of Neuroscience, Division of Biochemistry, University of Oldenburg, 26111 Oldenburg, Germany
| | - Helena Greb
- Department of Neuroscience, Division of Biochemistry, University of Oldenburg, 26111 Oldenburg, Germany
| | - Ulrike Janssen-Bienhold
- Department of Neuroscience, Division of Neurobiology, University of Oldenburg, 26111 Oldenburg, Germany
| | - Karl-Wilhelm Koch
- Department of Neuroscience, Division of Biochemistry, University of Oldenburg, 26111 Oldenburg, Germany.
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Reingruber J, Ingram NT, Griffis KG, Fain GL. A kinetic analysis of mouse rod and cone photoreceptor responses. J Physiol 2020; 598:3747-3763. [PMID: 32557629 PMCID: PMC7484371 DOI: 10.1113/jp279524] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Accepted: 06/08/2020] [Indexed: 12/21/2022] Open
Abstract
KEY POINTS Most vertebrate eyes have rods for dim-light vision and cones for brighter light and higher temporal sensitivity. Rods evolved from cone-like precursors through expression of different transduction genes or the same genes at different expression levels, but we do not know which molecular differences were most important. We approached this problem by analysing rod and cone responses with the same model but with different values for model parameters. We showed that, in addition to outer-segment volume, the most important differences between rods and cones are: (1) decreased transduction gain, reflecting smaller amplification in the G-protein cascade; (2) a faster rate of turnover of the second messenger cGMP in darkness; and (3) an accelerated rate of decay of the effector enzyme phosphodiesterase and perhaps also of activated visual pigment. We believe our analysis has identified the principal alterations during evolution responsible for the duplex retina. ABSTRACT Most vertebrates have rod and cone photoreceptors, which differ in their sensitivity and response kinetics. We know that rods evolved from cone-like precursors through the expression of different transduction genes or the same genes at different levels, but we do not know which molecular differences were most important. We have approached this problem in mouse retina by analysing the kinetic differences between rod flash responses and recent voltage-clamp recordings of cone flash responses, using a model incorporating the principal features of photoreceptor transduction. We apply a novel method of analysis using the log-transform of the current, and we ask which of the model's dynamic parameters need be changed to transform the flash response of a rod into that of a cone. The most important changes are a decrease in the gain of the response, reflecting a reduction in amplification of the transduction cascade; an increase in the rate of turnover of cGMP in darkness; and an increase in the rate of decay of activated phosphodiesterase, with perhaps also an increase in the rate of decay of light-activated visual pigment. Although we cannot exclude other differences, and in particular alterations in the Ca2+ economy of the photoreceptors, we believe that we have identified the kinetic parameters principally responsible for the differences in the flash responses of the two kinds of photoreceptors, which were likely during evolution to have resulted in the duplex retina.
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Affiliation(s)
- Jürgen Reingruber
- Institut de Biologie de l’École Normale Supérieure, 46 rue d’Ulm, 75005 Paris, France
| | - Norianne T. Ingram
- Department of Integrative Biology and Physiology, University of California, Los Angeles, CA 90095–7239, USA
- Department of Ophthalmology and Jules Stein Eye Institute, University of California, Los Angeles, CA 90095–7000, USA
| | - Khris G. Griffis
- Department of Ophthalmology and Jules Stein Eye Institute, University of California, Los Angeles, CA 90095–7000, USA
| | - Gordon L. Fain
- Department of Integrative Biology and Physiology, University of California, Los Angeles, CA 90095–7239, USA
- Department of Ophthalmology and Jules Stein Eye Institute, University of California, Los Angeles, CA 90095–7000, USA
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21
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Abstract
Rod photoreceptors are composed of a soma and an inner segment (IS) connected to an outer segment (OS) by a thin cilium. OSs are composed of a stack of ∼800 lipid discs surrounded by the plasma membrane where phototransduction takes place. Intracellular calcium plays a major role in phototransduction and is more concentrated in the discs, where it can be incorporated and released. To study calcium dynamics in rods, we used the fluorescent calcium dye CaSiR-1 AM working in the near-infrared (NIR) (excitation at 650 and emission at 664 nm), an advantage over previously used dyes. In this way, we investigated calcium dynamics with an unprecedented accuracy and most importantly in semidark-adapted conditions. We observed light-induced drops in [Ca2+]i with kinetics similar to that of photoresponses recorded electrophysiologically. We show three properties of the rods. First, intracellular calcium and key proteins have concentrations that vary from the OS base to tip. At the OS base, [Ca2+]i is ∼80 nM and increases up to ∼200 nM at the OS tip. Second, there are spontaneous calcium flares in healthy and functional rod OSs; these flares are highly localized and are more pronounced at the OS tip. Third, a bright flash of light at 488 nm induces a drop in [Ca2+]i at the OS base but often a flare at the OS tip. Therefore, rod OSs are not homogenous structures but have a structural and functional gradient, which is a fundamental aspect of transduction in vertebrate photoreceptors.
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Dal Cortivo G, Marino V, Bonì F, Milani M, Dell'Orco D. Missense mutations affecting Ca 2+-coordination in GCAP1 lead to cone-rod dystrophies by altering protein structural and functional properties. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2020; 1867:118794. [PMID: 32650103 DOI: 10.1016/j.bbamcr.2020.118794] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 07/01/2020] [Accepted: 07/03/2020] [Indexed: 02/06/2023]
Abstract
Guanylate cyclase activating protein 1 (GCAP1) is a neuronal calcium sensor (NCS) involved in the early biochemical steps underlying the phototransduction cascade. By switching from a Ca2+-bound form in the dark to a Mg2+-bound state following light activation of the cascade, GCAP1 triggers the activation of the retinal guanylate cyclase (GC), thus replenishing the levels of 3',5'-cyclic monophosphate (cGMP) necessary to re-open CNG channels. Here, we investigated the structural and functional effects of three missense mutations in GCAP1 associated with cone-rod dystrophy, which severely perturb the homeostasis of cGMP and Ca2+. Substitutions affect residues directly involved in Ca2+ coordination in either EF3 (D100G) or EF4 (E155A and E155G) Ca2+ binding motifs. We found that all GCAP1 variants form relatively stable dimers showing decreased apparent affinity for Ca2+ and blocking the enzyme in a constitutively active state at physiological levels of Ca2+. Interestingly, by corroborating spectroscopic experiments with molecular dynamics simulations we show that beside local structural effects, mutation of the bidentate glutamate in an EF-hand calcium binding motif can profoundly perturb the flexibility of the adjacent EF-hand as well, ultimately destabilizing the whole domain. Therefore, while Ca2+-binding to GCAP1 per se occurs sequentially, allosteric effects may connect EF hand motifs, which appear to be essential for the integrity of the structural switch mechanism in GCAP1, and perhaps in other NCS proteins.
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Affiliation(s)
- Giuditta Dal Cortivo
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, I-37134 Verona, Italy
| | - Valerio Marino
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, I-37134 Verona, Italy
| | - Francesco Bonì
- CNR-IBF, Istituto di Biofisica, Via Celoria 26, I-20133 Milano, Italy; Dipartimento di Bioscienze, Università di Milano, Via Celoria 26, I-20133 Milano, Italy
| | - Mario Milani
- CNR-IBF, Istituto di Biofisica, Via Celoria 26, I-20133 Milano, Italy; Dipartimento di Bioscienze, Università di Milano, Via Celoria 26, I-20133 Milano, Italy
| | - Daniele Dell'Orco
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, I-37134 Verona, Italy.
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23
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Abbas S, Marino V, Weisschuh N, Kieninger S, Solaki M, Dell’Orco D, Koch KW. Neuronal Calcium Sensor GCAP1 Encoded by GUCA1A Exhibits Heterogeneous Functional Properties in Two Cases of Retinitis Pigmentosa. ACS Chem Neurosci 2020; 11:1458-1470. [PMID: 32298085 DOI: 10.1021/acschemneuro.0c00111] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Genetic heterogeneity leading to retinal disorders impairs biological processes by causing, for example, severe disorder of signal transduction in photoreceptor outer segments. A normal balance of the second messenger homeostasis in photoreceptor cells seems to be a crucial factor for healthy and normal photoreceptor function. Genes like GUCY2D coding for guanylate cyclase GC-E and GUCA1A coding for the Ca2+-sensor guanylate cyclase-activating protein GCAP1 are critical for a precisely controlled synthesis of the second messenger cGMP. Mutations in GUCA1A frequently correlate in patients with cone dystrophy and cone-rod dystrophy. Here, we report two mutations in the GUCA1A gene that were found in patients diagnosed with retinitis pigmentosa, a phenotype that was rarely detected among previous cases of GUCA1A related retinopathies. One patient was heterozygous for the missense variant c.55C > T (p.H19Y), while the other patient was heterozygous for the missense variant c.479T > G (p.V160G). Using heterologous expression and cell culture systems, we examined the functional and molecular consequences of these point mutations. Both variants showed a dysregulation of guanylate cyclase activity, either a profound shift in Ca2+-sensitivity (H19Y) or a nearly complete loss of activating potency (V160G). Functional heterogeneity became also apparent in Ca2+/Mg2+-binding properties and protein conformational dynamics. A faster progression of retinal dystrophy in the patient carrying the V160G mutation seems to correlate with the more severe impairment of this variant.
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Affiliation(s)
- Seher Abbas
- Department of Neuroscience, Division of Biochemistry, University of Oldenburg, 26111 Oldenburg, Germany
| | - Valerio Marino
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, 37134 Verona, Italy
| | - Nicole Weisschuh
- Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, 72076 Tübingen, Germany
| | - Sinja Kieninger
- Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, 72076 Tübingen, Germany
| | - Maria Solaki
- Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, 72076 Tübingen, Germany
| | - Daniele Dell’Orco
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, 37134 Verona, Italy
| | - Karl-Wilhelm Koch
- Department of Neuroscience, Division of Biochemistry, University of Oldenburg, 26111 Oldenburg, Germany
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24
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Xu H, Enemchukwu N, Zhong X, Zhang O, Fu Y. Deletion of M-Opsin Prevents M Cone Degeneration in a Mouse Model of Leber Congenital Amaurosis. THE AMERICAN JOURNAL OF PATHOLOGY 2020; 190:1059-1067. [PMID: 32084365 PMCID: PMC7237827 DOI: 10.1016/j.ajpath.2020.01.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 12/24/2019] [Accepted: 01/07/2020] [Indexed: 12/15/2022]
Abstract
Mutations in retinoid isomerase (RPE65) or lecithin-retinol acyltransferase (LRAT) disrupt 11-cis-retinal synthesis and cause Leber congenital amaurosis (LCA). Despite the success of recent RPE65 gene therapy, follow-up studies show that patients continue to experience photoreceptor degeneration and lose vision benefit over time. In Lrat-/- mouse model, mislocalized medium (M)-wavelength opsin was degraded, whereas mislocalized short (S)-wavelength opsin accumulated before the onset of cone degeneration. The mechanism for the foveal M/long-wavelength cone photoreceptor degeneration in LCA is unknown. By crossing Lrat-/- mice with a proteasome reporter mouse strain, this study showed that M-opsin-enriched dorsal cones in Lrat-/- mice exhibit proteasome stress because of the degradation of large amounts of M-opsin. Deletion of M-opsin relieves the proteasome stress and completely prevents M cone degeneration in Lrat-/-Opn1sw-/- mice (a pure M cone LCA model, Opn1sw encoding S-opsin) for at least 12 months. These results suggest that M-opsin degradation-associated proteasome stress plays a major role in M cone degeneration in Lrat-/- model. This finding may represent a general mechanism for M cone degeneration in multiple forms of cone degeneration because of M-opsin mislocalization and degradation. These results have important implications for the current gene therapy strategy for LCA that emphasizes the need for combinatorial therapies to both improve vision and slow photoreceptor degeneration.
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Affiliation(s)
- Hui Xu
- Interdepartmental Program in Neuroscience, Department of Ophthalmology, University of Utah, Salt Lake City, Utah; Departments of Ophthalmology and Neuroscience, Baylor College of Medicine, Houston, Texas; Departments of Ophthalmology and Neuroscience, Baylor College of Medicine, Houston, Texas
| | - Nduka Enemchukwu
- Departments of Ophthalmology and Neuroscience, Baylor College of Medicine, Houston, Texas; Departments of Ophthalmology and Neuroscience, Baylor College of Medicine, Houston, Texas
| | - Xiaoyue Zhong
- Departments of Ophthalmology and Neuroscience, Baylor College of Medicine, Houston, Texas; Departments of Ophthalmology and Neuroscience, Baylor College of Medicine, Houston, Texas; Rice University, Houston, Texas
| | - Olivia Zhang
- Departments of Ophthalmology and Neuroscience, Baylor College of Medicine, Houston, Texas; Departments of Ophthalmology and Neuroscience, Baylor College of Medicine, Houston, Texas; Rice University, Houston, Texas
| | - Yingbin Fu
- Interdepartmental Program in Neuroscience, Department of Ophthalmology, University of Utah, Salt Lake City, Utah; Departments of Ophthalmology and Neuroscience, Baylor College of Medicine, Houston, Texas; Departments of Ophthalmology and Neuroscience, Baylor College of Medicine, Houston, Texas.
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25
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Byun JH, Hyeon JY, Kim ES, Kim BH, Miyanishi H, Kagawa H, Takeuchi Y, Kim SJ, Takemura A, Hur SP. Gene expression patterns of novel visual and non-visual opsin families in immature and mature Japanese eel males. PeerJ 2020; 8:e8326. [PMID: 32149019 PMCID: PMC7049458 DOI: 10.7717/peerj.8326] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2019] [Accepted: 12/02/2019] [Indexed: 01/24/2023] Open
Abstract
This study was carried out to identify and estimate physiological function of a new type of opsin subfamily present in the retina and whole brain tissues of Japanese eel using RNA–Seq transcriptome method. A total of 18 opsin subfamilies were identified through RNA–seq. The visual opsin family included Rh2, SWS2, FWO, DSO, and Exo-Rhod. The non-visual opsin family included four types of melanopsin subfamily (Opn4x1, Opn4x2, Opn4m1, and Opn4m2), peropsin, two types of neuropsin subfamily (Opn5-like, Opn5), Opn3, three types of TMT opsin subfamily (TMT1, 2, 3), VA-opsin, and parapinopsin. In terms of changes in photoreceptor gene expression in the retina of sexually mature and immature male eels, DSO mRNA increased in the maturation group. Analysis of expression of opsin family gene in male eel brain before and after maturation revealed that DSO and SWS2 expression in terms of visual opsin mRNA increased in the sexually mature group. In terms of non-visual opsin mRNA, parapinopsin mRNA increased whereas that of TMT2 decreased in the fore-brain of the sexually mature group. The mRNA for parapinopsin increased in the mid-brain of the sexually mature group, whereas those of TMT1 and TMT3 increased in the hind-brain of the sexually mature group. DSO mRNA also increased in the retina after sexual maturation, and DSO and SWS2 mRNA increased in whole brain part, suggesting that DSO and SWS2 are closely related to sexual maturation.
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Affiliation(s)
- Jun-Hwan Byun
- Graduate School of Engineering and Science, University of the Ryukyus, Nishihara, Okinawa, Japan
| | - Ji-Yeon Hyeon
- Jeju Research Institute, Korea Institute of Ocean Science & Technology, Jeju, Jeju, Republic of Korea.,Department of Biology, Jeju National University, Jeju, Jeju, Republic of Korea
| | - Eun-Su Kim
- Jeju Research Institute, Korea Institute of Ocean Science & Technology, Jeju, Jeju, Republic of Korea.,Department of Biology, Jeju National University, Jeju, Jeju, Republic of Korea
| | - Byeong-Hoon Kim
- Marine Science Institute, Jeju National University, Jeju, Jeju, Republic of Korea
| | - Hiroshi Miyanishi
- Department of Marine Biology and Environmental Sciences, Faculty of Agriculture, University of Miyazaki, Gakuen-Kibanadai-Nishi, Miyazaki, Japan
| | - Hirohiko Kagawa
- Department of Marine Biology and Environmental Sciences, Faculty of Agriculture, University of Miyazaki, Gakuen-Kibanadai-Nishi, Miyazaki, Japan
| | - Yuki Takeuchi
- Department of Chemistry, Biology and Marine Science, Faculty of Science, University of the Ryukyus, Nishihara, Okinawa, Japan
| | - Se-Jae Kim
- Department of Biology, Jeju National University, Jeju, Jeju, Republic of Korea
| | - Akihiro Takemura
- Department of Chemistry, Biology and Marine Science, Faculty of Science, University of the Ryukyus, Nishihara, Okinawa, Japan
| | - Sung-Pyo Hur
- Jeju Research Institute, Korea Institute of Ocean Science & Technology, Jeju, Jeju, Republic of Korea.,Department of Biology, Jeju National University, Jeju, Jeju, Republic of Korea
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26
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Ko GYP. Circadian regulation in the retina: From molecules to network. Eur J Neurosci 2020; 51:194-216. [PMID: 30270466 PMCID: PMC6441387 DOI: 10.1111/ejn.14185] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Revised: 08/16/2018] [Accepted: 08/20/2018] [Indexed: 12/14/2022]
Abstract
The mammalian retina is the most unique tissue among those that display robust circadian/diurnal oscillations. The retina is not only a light sensing tissue that relays light information to the brain, it has its own circadian "system" independent from any influence from other circadian oscillators. While all retinal cells and retinal pigment epithelium (RPE) possess circadian oscillators, these oscillators integrate by means of neural synapses, electrical coupling (gap junctions), and released neurochemicals (such as dopamine, melatonin, adenosine, and ATP), so the whole retina functions as an integrated circadian system. Dysregulation of retinal clocks not only causes retinal or ocular diseases, it also impacts the circadian rhythm of the whole body, as the light information transmitted from the retina entrains the brain clock that governs the body circadian rhythms. In this review, how circadian oscillations in various retinal cells are integrated, and how retinal diseases affect daily rhythms.
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Affiliation(s)
- Gladys Y-P Ko
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas
- Texas A&M Institute for Neuroscience, Texas A&M University, College Station, Texas
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27
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Lu Y, Kim TH, Yao X. Comparative study of wild-type and rd10 mice reveals transient intrinsic optical signal response before phosphodiesterase activation in retinal photoreceptors. Exp Biol Med (Maywood) 2019; 245:360-367. [PMID: 31852239 DOI: 10.1177/1535370219896284] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Transient intrinsic optical signal (IOS) has been observed in stimulus-evoked retinal photoreceptors. This study is to compare IOS changes in wild-type and retinal degeneration 10 (rd10) mouse retinas, to evaluate the effect of cyclic guanosine monophosphate phosphodiesterase on photoreceptor-IOS. Time-lapse near-infrared light microscopy was employed to monitor the spatiotemporal dynamics of the IOS responses in freshly isolated retinas activated by visible light stimulation. Comparative IOS recordings were conducted at postnatal days 14 (P14) and P16. At P14, intrinsic optical signal magnitudes and spatiotemporal dynamics in wild-type and rd10 retinas were similar, indicating that the phosphodiesterase deficiency in rd10 did not affect the formation of photoreceptor-IOS. At P16, IOS magnitude in rd10 significantly decreased compared to that in wild-type, suggesting the IOS sensitivity to the photoreceptor degeneration in rd10. Our experimental results and theoretical analysis indicate that early disc-based stages of the phototransduction cascade before the activation of phosphodiesterase may contribute to the formation of the photoreceptor-IOS responses; and the IOS can be a sensitive biomarker for objective assessment of retinal function. Impact statement Comparative study of wild-type and rd10 mice was implemented to reveal that transient intrinsic optical signal (IOS) was initiated before the phosphodiesterase activation in stimulus-activated photoreceptors and the IOS magnitude was sensitive to photoreceptor degeneration. The photoreceptor-IOS promises a noninvasive biomarker for objective assessment of age-related macular degeneration, retinitis pigmentosa, and other eye diseases that can produce photoreceptor dysfunctions.
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Affiliation(s)
- Yiming Lu
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Tae-Hoon Kim
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Xincheng Yao
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA.,Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL 60612, USA
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28
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Bocchero U, Tam BM, Chiu CN, Torre V, Moritz OL. Electrophysiological Changes During Early Steps of Retinitis Pigmentosa. Invest Ophthalmol Vis Sci 2019; 60:933-943. [PMID: 30840038 DOI: 10.1167/iovs.18-25347] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose The rhodopsin mutation P23H is responsible for a significant portion of autosomal-dominant retinitis pigmentosa, a disorder characterized by rod photoreceptor death. The mechanisms of toxicity remain unclear; previous studies implicate destabilization of P23H rhodopsin during light exposure, causing decreased endoplasmic reticulum (ER) exit and ER stress responses. Here, we probed phototransduction in Xenopus laevis rods expressing bovine P23H rhodopsin, in which retinal degeneration is inducible by light exposure, in order to examine early physiological changes that occur during retinal degeneration. Methods We recorded single-cell and whole-retina responses to light stimuli using electrophysiology. Moreover, we monitored morphologic changes in rods after different periods of light exposure. Results Initially, P23H rods had almost normal photoresponses, but following a brief light exposure varying from 4 to 32 photoisomerizations per disc, photoresponses became irreversibly prolonged. In intact retinas, rods began to shed OS fragments after a rod-saturating exposure of 12 minutes, corresponding to approximately 10 to 100 times more photoisomerizations. Conclusions Our results indicate that in P23H rods light-induced degeneration occurs in at least two stages, the first involving impairment of phototransduction and the second involving initiation of morphologic changes.
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Affiliation(s)
- Ulisse Bocchero
- Neuroscience Department, International School for Advanced Studies (SISSA), Trieste, Italy
| | - Beatrice M Tam
- Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Colette N Chiu
- Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Vincent Torre
- Neuroscience Department, International School for Advanced Studies (SISSA), Trieste, Italy
| | - Orson L Moritz
- Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, British Columbia, Canada
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29
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Modeling and simulation of phototransduction cascade in vertebrate rod photoreceptors. BMC Ophthalmol 2019; 19:55. [PMID: 30786871 PMCID: PMC6381673 DOI: 10.1186/s12886-019-1048-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 01/24/2019] [Indexed: 11/21/2022] Open
Abstract
Background The activation of phototransduction cascade in rod photoreceptors has been well studied in literature, but there is a lack of a mature kinetic model structure covering both the activation and inactivation processes. Methods In this work, a kinetic model structure is developed to describe the major activation and inactivation processes in vertebrate rod photoreceptors with the electroretinogram (ERG) as output. Simulation was performed to validate developed model structure. Results The developed model structure could fit experimental data with small error. Conclusions The result indicated that the developed model structure could show the inactivation process of phototransduction cascades in the rod photoreceptors.
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30
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Determination of basal phosphodiesterase activity in mouse rod photoreceptors with cGMP clamp. Sci Rep 2019; 9:1183. [PMID: 30718640 PMCID: PMC6362171 DOI: 10.1038/s41598-018-37661-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Accepted: 12/11/2018] [Indexed: 12/26/2022] Open
Abstract
Light regulates cGMP concentration in the photoreceptor cytoplasm by activating phosphodiesterase (PDE) molecules through a G-protein signalling cascade. Spontaneous PDE activity is present in rod outer segments even in darkness. This basal PDE activity (βdark) has not been determined in wild type mammalian photoreceptor cells although it plays a key role in setting the sensitivity and recovery kinetics of rod responses. We present a novel method for determination of βdark using local electroretinography (LERG) from isolated mouse retinas. The method is based on the ability of PDE inhibitors to decrease βdark, which can be counterbalanced by increasing PDE activity with light. This procedure clamps cytoplasmic cGMP to its dark value. βdark can be calculated based on the amount of light needed for the "cGMP clamp" and information extracted from the registered rod photoresponses. Here we apply this method to determine βdark values for the first time in the mammalian rods and obtain the following estimates for different mouse models: 3.9 s-1 for wild type, 4.5 s-1 for guanylate cyclase activating proteins (GCAPs) knockout, and 4.4 s-1 for GCAPs and recoverin double knockout mice. Our results suggest that depletion of GCAPs or recoverin do not affect βdark.
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31
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Kinoshita J, Peachey NS. Noninvasive Electroretinographic Procedures for the Study of the Mouse Retina. ACTA ACUST UNITED AC 2018; 8:1-16. [PMID: 30040236 DOI: 10.1002/cpmo.39] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Overall retinal function can be monitored by recording the light-evoked response of the eye at the corneal surface. The major components of the electroretinogram (ERG) provide important information regarding the functional status of many retinal cell types including rod photoreceptors, cone photoreceptors, bipolar cells, and the retinal pigment epithelium (RPE). The ERG can be readily recorded from mice, and this unit describes procedures for mouse anesthesia and the use of stimulation and recording procedures for measuring ERGs that reflect the response properties of different retinal cell types. Through these, the mouse ERG provides a noninvasive approach to measure multiple aspects of outer retinal function, including the status of the initial rod and cone pathways, rod photoreceptor deactivation, rod dark adaptation, the photoreceptor-to-bipolar cell synapse, and the RPE. © 2018 by John Wiley & Sons, Inc.
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Affiliation(s)
- Junzo Kinoshita
- Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, Ohio
| | - Neal S Peachey
- Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, Ohio.,Louis Stokes Cleveland VA Medical Center, Cleveland, Ohio.,Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, Ohio
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32
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Lu Y, Liu C, Yao X. In vivo observation of transient photoreceptor movement correlated with oblique light stimulation. PROCEEDINGS OF SPIE--THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING 2018; 10497:104971M. [PMID: 29950751 PMCID: PMC6016829 DOI: 10.1117/12.2287262] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Rod-dominated transient retinal phototropism (TRP) has been observed in freshly isolated retinas, promising a noninvasive biomarker for high resolution assessment of retinal physiology. However, in vivo mapping of TRP is challenging due to its fast time course and sub-cellular signal magnitude. By developing a line-scanning and virtually structured detection based super-resolution ophthalmoscope, we report here in vivo observation of TRP in frog retina. In vivo characterization of TRP time course and magnitude were implemented by using variable light stimulus intensities.
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Affiliation(s)
- Yiming Lu
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Changgeng Liu
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Xincheng Yao
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL 60612, USA
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33
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Shimmura T, Nakayama T, Shinomiya A, Fukamachi S, Yasugi M, Watanabe E, Shimo T, Senga T, Nishimura T, Tanaka M, Kamei Y, Naruse K, Yoshimura T. Dynamic plasticity in phototransduction regulates seasonal changes in color perception. Nat Commun 2017; 8:412. [PMID: 28871081 PMCID: PMC5583187 DOI: 10.1038/s41467-017-00432-8] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 06/28/2017] [Indexed: 12/05/2022] Open
Abstract
To cope with seasonal changes in the environment, organisms adapt their physiology and behavior. Although color perception varies among seasons, the underlying molecular basis and its physiological significance remain unclear. Here we show that dynamic plasticity in phototransduction regulates seasonal changes in color perception in medaka fish. Medaka are active and exhibit clear phototaxis in conditions simulating summer, but remain at the bottom of the tank and fail to exhibit phototaxis in conditions simulating winter. Mate preference tests using virtual fish created with computer graphics demonstrate that medaka are more attracted to orange-red-colored model fish in summer than in winter. Transcriptome analysis of the eye reveals dynamic seasonal changes in the expression of genes encoding photopigments and their downstream pathways. Behavioral analysis of photopigment-null fish shows significant differences from wild type, suggesting that plasticity in color perception is crucial for the emergence of seasonally regulated behaviors. Animal coloration and behavior can change seasonally, but it is unclear if visual sensitivity to color shifts as well. Here, Shimmura et al. show that medaka undergo seasonal behavioral change accompanied by altered expression of opsin genes, resulting in reduced visual sensitivity to mates during winter-like conditions.
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Affiliation(s)
- Tsuyoshi Shimmura
- Division of Seasonal Biology, National Institute for Basic Biology, National Institutes of Natural Sciences, Okazaki, Aichi, 444-8585, Japan.,Department of Basic Biology, The Graduate University for Advanced Studies (SOKENDAI), Hayama, 240-0193, Japan.,Laboratory of Animal Physiology, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi, 464-8601, Japan.,Department of Biological Production, Tokyo University of Agriculture and Technology, Fuchu, Tokyo, 183-8509, Japan
| | - Tomoya Nakayama
- Division of Seasonal Biology, National Institute for Basic Biology, National Institutes of Natural Sciences, Okazaki, Aichi, 444-8585, Japan.,Laboratory of Animal Physiology, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi, 464-8601, Japan
| | - Ai Shinomiya
- Division of Seasonal Biology, National Institute for Basic Biology, National Institutes of Natural Sciences, Okazaki, Aichi, 444-8585, Japan.,Department of Basic Biology, The Graduate University for Advanced Studies (SOKENDAI), Hayama, 240-0193, Japan
| | - Shoji Fukamachi
- Department of Chemical and Biological Sciences, Japan Women's University, Bunkyo-ku, Tokyo, 112-8681, Japan
| | - Masaki Yasugi
- Laboratory of Neurophysiology, National Institute for Basic Biology, National Institutes of Natural Sciences, Okazaki, Aichi, 444-8585, Japan
| | - Eiji Watanabe
- Department of Basic Biology, The Graduate University for Advanced Studies (SOKENDAI), Hayama, 240-0193, Japan.,Laboratory of Neurophysiology, National Institute for Basic Biology, National Institutes of Natural Sciences, Okazaki, Aichi, 444-8585, Japan
| | - Takayuki Shimo
- Division of Seasonal Biology, National Institute for Basic Biology, National Institutes of Natural Sciences, Okazaki, Aichi, 444-8585, Japan.,Laboratory of Animal Physiology, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi, 464-8601, Japan
| | - Takumi Senga
- Division of Seasonal Biology, National Institute for Basic Biology, National Institutes of Natural Sciences, Okazaki, Aichi, 444-8585, Japan.,Laboratory of Animal Physiology, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi, 464-8601, Japan
| | - Toshiya Nishimura
- Laboratory of Molecular Genetics for Reproduction, National Institute for Basic Biology, Okazaki, Aichi, 444-8787, Japan.,Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Aichi, 464-8601, Japan
| | - Minoru Tanaka
- Department of Basic Biology, The Graduate University for Advanced Studies (SOKENDAI), Hayama, 240-0193, Japan.,Laboratory of Molecular Genetics for Reproduction, National Institute for Basic Biology, Okazaki, Aichi, 444-8787, Japan.,Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Aichi, 464-8601, Japan
| | - Yasuhiro Kamei
- Department of Basic Biology, The Graduate University for Advanced Studies (SOKENDAI), Hayama, 240-0193, Japan.,Spectrography and Bioimaging Facility, National Institute for Basic Biology, National Institutes of Natural Sciences, Okazaki, Aichi, 444-8585, Japan
| | - Kiyoshi Naruse
- Department of Basic Biology, The Graduate University for Advanced Studies (SOKENDAI), Hayama, 240-0193, Japan.,Laboratory of Bioresources, National Institute for Basic Biology, National Institutes of Natural Sciences, Okazaki, Aichi, 444-8585, Japan
| | - Takashi Yoshimura
- Division of Seasonal Biology, National Institute for Basic Biology, National Institutes of Natural Sciences, Okazaki, Aichi, 444-8585, Japan. .,Laboratory of Animal Physiology, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi, 464-8601, Japan. .,Avian Bioscience Research Center, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi, 464-8601, Japan. .,Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Nagoya, 464-8601, Aichi, Japan.
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34
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Abstract
Fertilization is exceptionally complex and, depending on the species, happens in entirely different environments. External fertilizers in aquatic habitats, like marine invertebrates or fish, release their gametes into the seawater or freshwater, whereas sperm from most internal fertilizers like mammals cross the female genital tract to make their way to the egg. Various chemical and physical cues guide sperm to the egg. Quite generally, these cues enable signaling pathways that ultimately evoke a cellular Ca2+ response that modulates the waveform of the flagellar beat and, hence, the swimming path. To cope with the panoply of challenges to reach and fertilize the egg, sperm from different species have developed their own unique repertoire of signaling molecules and mechanisms. Here, we review the differences and commonalities for sperm sensory signaling in marine invertebrates (sea urchin), fish (zebrafish), and mammals (mouse, human).
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Affiliation(s)
- Dagmar Wachten
- Minerva Max Planck Research Group, Molecular Physiology, Center of Advanced European Studies and Research (caesar), 53175 Bonn, Germany
| | - Jan F Jikeli
- Minerva Max Planck Research Group, Molecular Physiology, Center of Advanced European Studies and Research (caesar), 53175 Bonn, Germany
| | - U Benjamin Kaupp
- Department Molecular Sensory Systems, Center of Advanced European Studies and Research (caesar), 53175 Bonn, Germany
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35
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Abstract
This study introduces a novel retinal temperature determination method based on the temperature dependent properties of photoresponses recorded by electroretinography (ERG). The kinetics and amplitudes of ERG photoresponses depend on retinal temperature. Additionally, raising retinal temperature increases the probability of long-wavelength photon absorption, which manifests as temperature dependence of photoreceptor sensitivity. In this study we extract a number of features that represent these properties from the a- and b-waves of mouse ex vivo ERG flash responses and construct three multivariable regression models between temperature and the selected features. The performance of these models was evaluated against a separate test dataset and for two of the models, an RMS temperature determination error of less than 0.50 °C could be reached. Our results demonstrate that the method can be successfully used for reliable retinal temperature determination ex vivo. The method, reflecting the temperature of distal retina, can be applied also in the estimation of retinal pigment epithelium temperature.
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36
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Jovancevic N, Wunderlich KA, Haering C, Flegel C, Maßberg D, Weinrich M, Weber L, Tebbe L, Kampik A, Gisselmann G, Wolfrum U, Hatt H, Gelis L. Deep Sequencing of the Human Retinae Reveals the Expression of Odorant Receptors. Front Cell Neurosci 2017; 11:03. [PMID: 28174521 PMCID: PMC5258773 DOI: 10.3389/fncel.2017.00003] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Accepted: 01/09/2017] [Indexed: 01/17/2023] Open
Abstract
Several studies have demonstrated that the expression of odorant receptors (ORs) occurs in various tissues. These findings have served as a basis for functional studies that demonstrate the potential of ORs as drug targets for a clinical application. To the best of our knowledge, this report describes the first evaluation of the mRNA expression of ORs and the localization of OR proteins in the human retina that set a stage for subsequent functional analyses. RNA-Sequencing datasets of three individual neural retinae were generated using Next-generation sequencing and were compared to previously published but reanalyzed datasets of the peripheral and the macular human retina and to reference tissues. The protein localization of several ORs was investigated by immunohistochemistry. The transcriptome analyses detected an average of 14 OR transcripts in the neural retina, of which OR6B3 is one of the most highly expressed ORs. Immunohistochemical stainings of retina sections localized OR2W3 to the photosensitive outer segment membranes of cones, whereas OR6B3 was found in various cell types. OR5P3 and OR10AD1 were detected at the base of the photoreceptor connecting cilium, and OR10AD1 was also localized to the nuclear envelope of all of the nuclei of the retina. The cell type-specific expression of the ORs in the retina suggests that there are unique biological functions for those receptors.
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Affiliation(s)
| | - Kirsten A Wunderlich
- Department of Cell and Matrix Biology, Johannes Gutenberg University of Mainz Mainz, Germany
| | - Claudia Haering
- Department of Cell Physiology, Ruhr-University Bochum Bochum, Germany
| | - Caroline Flegel
- Department of Cell Physiology, Ruhr-University Bochum Bochum, Germany
| | - Désirée Maßberg
- Department of Cell Physiology, Ruhr-University Bochum Bochum, Germany
| | - Markus Weinrich
- Department of Cell Physiology, Ruhr-University Bochum Bochum, Germany
| | - Lea Weber
- Department of Cell Physiology, Ruhr-University Bochum Bochum, Germany
| | - Lars Tebbe
- Department of Cell and Matrix Biology, Johannes Gutenberg University of Mainz Mainz, Germany
| | - Anselm Kampik
- Department of Ophthalmology, Ludwig Maximilian University of Munich Munich, Germany
| | - Günter Gisselmann
- Department of Cell Physiology, Ruhr-University Bochum Bochum, Germany
| | - Uwe Wolfrum
- Department of Cell and Matrix Biology, Johannes Gutenberg University of Mainz Mainz, Germany
| | - Hanns Hatt
- Department of Cell Physiology, Ruhr-University Bochum Bochum, Germany
| | - Lian Gelis
- Department of Cell Physiology, Ruhr-University Bochum Bochum, Germany
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37
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Hansen RM, Moskowitz A, Akula JD, Fulton AB. The neural retina in retinopathy of prematurity. Prog Retin Eye Res 2017; 56:32-57. [PMID: 27671171 PMCID: PMC5237602 DOI: 10.1016/j.preteyeres.2016.09.004] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Revised: 09/15/2016] [Accepted: 09/20/2016] [Indexed: 12/26/2022]
Abstract
Retinopathy of prematurity (ROP) is a neurovascular disease that affects prematurely born infants and is known to have significant long term effects on vision. We conducted the studies described herein not only to learn more about vision but also about the pathogenesis of ROP. The coincidence of ROP onset and rapid developmental elongation of the rod photoreceptor outer segments motivated us to consider the role of the rods in this disease. We used noninvasive electroretinographic (ERG), psychophysical, and retinal imaging procedures to study the function and structure of the neurosensory retina. Rod photoreceptor and post-receptor responses are significantly altered years after the preterm days during which ROP is an active disease. The alterations include persistent rod dysfunction, and evidence of compensatory remodeling of the post-receptor retina is found in ERG responses to full-field stimuli and in psychophysical thresholds that probe small retinal regions. In the central retina, both Mild and Severe ROP delay maturation of parafoveal scotopic thresholds and are associated with attenuation of cone mediated multifocal ERG responses, significant thickening of post-receptor retinal laminae, and dysmorphic cone photoreceptors. These results have implications for vision and control of eye growth and refractive development and suggest future research directions. These results also lead to a proposal for noninvasive management using light that may add to the currently invasive therapeutic armamentarium against ROP.
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Affiliation(s)
- Ronald M Hansen
- Department of Ophthalmology, Children's Hospital and Harvard Medical School, 300 Longwood Ave., Boston, MA 02115-5737, USA.
| | - Anne Moskowitz
- Department of Ophthalmology, Children's Hospital and Harvard Medical School, 300 Longwood Ave., Boston, MA 02115-5737, USA.
| | - James D Akula
- Department of Ophthalmology, Children's Hospital and Harvard Medical School, 300 Longwood Ave., Boston, MA 02115-5737, USA.
| | - Anne B Fulton
- Department of Ophthalmology, Children's Hospital and Harvard Medical School, 300 Longwood Ave., Boston, MA 02115-5737, USA.
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38
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Noninvasive imaging of the photoreceptor mosaic response to light stimulation. Proc Natl Acad Sci U S A 2016; 113:12902-12903. [PMID: 27810954 DOI: 10.1073/pnas.1615790113] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
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39
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Petrukhin OV, Orlova TG, Nezvetsky AR, Orlov NY. The decrement in light sensitivity of the isolated frog retinal rod in the presence of a phosphorylation-resistant GDP analogue of guanosine-5′-O-(2-thiodiphosphate) as a confirmation of the hypothesis about transducin activation via the transphosphorylation mechanism. Biophysics (Nagoya-shi) 2016. [DOI: 10.1134/s0006350916050249] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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40
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Petrukhin OV, Orlova TG, Nezvetsky AR, Orlov NY. Transducin-activated cGMP-specific phosphodiesterase of external segments of bovine retinal rods: The influence of magnesium ions. Biophysics (Nagoya-shi) 2016. [DOI: 10.1134/s0006350916050237] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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41
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Petrukhin OV, Orlova TG, Nezvetsky AR, Orlov NY. Modeling of phototransduction processes in the photoreceptor disk membranes by the Monte Carlo method. Biophysics (Nagoya-shi) 2016. [DOI: 10.1134/s000635091606021x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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42
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Song Z, Zhou Y, Juusola M. Random Photon Absorption Model Elucidates How Early Gain Control in Fly Photoreceptors Arises from Quantal Sampling. Front Comput Neurosci 2016; 10:61. [PMID: 27445779 PMCID: PMC4919358 DOI: 10.3389/fncom.2016.00061] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 06/09/2016] [Indexed: 11/13/2022] Open
Abstract
Many diurnal photoreceptors encode vast real-world light changes effectively, but how this performance originates from photon sampling is unclear. A 4-module biophysically-realistic fly photoreceptor model, in which information capture is limited by the number of its sampling units (microvilli) and their photon-hit recovery time (refractoriness), can accurately simulate real recordings and their information content. However, sublinear summation in quantum bump production (quantum-gain-nonlinearity) may also cause adaptation by reducing the bump/photon gain when multiple photons hit the same microvillus simultaneously. Here, we use a Random Photon Absorption Model (RandPAM), which is the 1st module of the 4-module fly photoreceptor model, to quantify the contribution of quantum-gain-nonlinearity in light adaptation. We show how quantum-gain-nonlinearity already results from photon sampling alone. In the extreme case, when two or more simultaneous photon-hits reduce to a single sublinear value, quantum-gain-nonlinearity is preset before the phototransduction reactions adapt the quantum bump waveform. However, the contribution of quantum-gain-nonlinearity in light adaptation depends upon the likelihood of multi-photon-hits, which is strictly determined by the number of microvilli and light intensity. Specifically, its contribution to light-adaptation is marginal (≤ 1%) in fly photoreceptors with many thousands of microvilli, because the probability of simultaneous multi-photon-hits on any one microvillus is low even during daylight conditions. However, in cells with fewer sampling units, the impact of quantum-gain-nonlinearity increases with brightening light.
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Affiliation(s)
- Zhuoyi Song
- Centre for Mathematics, Physics and Engineering in the Life Sciences and Experimental Biology (CoMPLEX), University College LondonLondon, UK; Department of Biomedical Science, University of SheffieldSheffield, UK
| | - Yu Zhou
- School of Engineering, College of Science and Technology, University of Central Lancashire Preston, UK
| | - Mikko Juusola
- Department of Biomedical Science, University of SheffieldSheffield, UK; State Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal UniversityBeijing, China
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43
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Potvin-Fournier K, Lefèvre T, Picard-Lafond A, Marcotte C, Dufresne C, Cantin L, Salesse C, Auger M. Discriminating Lipid– from Protein–Calcium Binding To Understand the Interaction between Recoverin and Phosphatidylglycerol Model Membranes. Biochemistry 2016; 55:3481-91. [DOI: 10.1021/acs.biochem.6b00408] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Kim Potvin-Fournier
- Département
de chimie, Regroupement québécois de recherche sur la
fonction, l’ingénierie et les applications des protéines
(PROTEO), Centre de recherche sur les matériaux avancés
(CERMA), Centre québécois sur les matériaux fonctionnels
(CQMF), Université Laval, Pavillon Alexandre-Vachon, 1045
avenue de la médecine, Québec, Québec G1V 0A6, Canada
- CUO-recherche,
Centre de recherche du CHU de Québec, Hôpital du Saint-Sacrement,
Département d’ophtalmologie, Faculté de médecine,
PROTEO, Université Laval, Québec, Québec G1S 4L8, Canada
| | - Thierry Lefèvre
- Département
de chimie, Regroupement québécois de recherche sur la
fonction, l’ingénierie et les applications des protéines
(PROTEO), Centre de recherche sur les matériaux avancés
(CERMA), Centre québécois sur les matériaux fonctionnels
(CQMF), Université Laval, Pavillon Alexandre-Vachon, 1045
avenue de la médecine, Québec, Québec G1V 0A6, Canada
| | - Audrey Picard-Lafond
- Département
de chimie, Regroupement québécois de recherche sur la
fonction, l’ingénierie et les applications des protéines
(PROTEO), Centre de recherche sur les matériaux avancés
(CERMA), Centre québécois sur les matériaux fonctionnels
(CQMF), Université Laval, Pavillon Alexandre-Vachon, 1045
avenue de la médecine, Québec, Québec G1V 0A6, Canada
| | - Catherine Marcotte
- Département
de chimie, Regroupement québécois de recherche sur la
fonction, l’ingénierie et les applications des protéines
(PROTEO), Centre de recherche sur les matériaux avancés
(CERMA), Centre québécois sur les matériaux fonctionnels
(CQMF), Université Laval, Pavillon Alexandre-Vachon, 1045
avenue de la médecine, Québec, Québec G1V 0A6, Canada
| | - Caroline Dufresne
- Département
de chimie, Regroupement québécois de recherche sur la
fonction, l’ingénierie et les applications des protéines
(PROTEO), Centre de recherche sur les matériaux avancés
(CERMA), Centre québécois sur les matériaux fonctionnels
(CQMF), Université Laval, Pavillon Alexandre-Vachon, 1045
avenue de la médecine, Québec, Québec G1V 0A6, Canada
| | - Line Cantin
- CUO-recherche,
Centre de recherche du CHU de Québec, Hôpital du Saint-Sacrement,
Département d’ophtalmologie, Faculté de médecine,
PROTEO, Université Laval, Québec, Québec G1S 4L8, Canada
| | - Christian Salesse
- CUO-recherche,
Centre de recherche du CHU de Québec, Hôpital du Saint-Sacrement,
Département d’ophtalmologie, Faculté de médecine,
PROTEO, Université Laval, Québec, Québec G1S 4L8, Canada
| | - Michèle Auger
- Département
de chimie, Regroupement québécois de recherche sur la
fonction, l’ingénierie et les applications des protéines
(PROTEO), Centre de recherche sur les matériaux avancés
(CERMA), Centre québécois sur les matériaux fonctionnels
(CQMF), Université Laval, Pavillon Alexandre-Vachon, 1045
avenue de la médecine, Québec, Québec G1V 0A6, Canada
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44
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Lamb TD, Patel H, Chuah A, Natoli RC, Davies WIL, Hart NS, Collin SP, Hunt DM. Evolution of Vertebrate Phototransduction: Cascade Activation. Mol Biol Evol 2016; 33:2064-87. [PMID: 27189541 PMCID: PMC4948711 DOI: 10.1093/molbev/msw095] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
We applied high-throughput sequencing to eye tissue from several species of basal vertebrates (a hagfish, two species of lamprey, and five species of gnathostome fish), and we analyzed the mRNA sequences for the proteins underlying activation of the phototransduction cascade. The molecular phylogenies that we constructed from these sequences are consistent with the 2R WGD model of two rounds of whole genome duplication. Our analysis suggests that agnathans retain an additional representative (that has been lost in gnathostomes) in each of the gene families we studied; the evidence is strong for the G-protein α subunit (GNAT) and the cGMP phosphodiesterase (PDE6), and indicative for the cyclic nucleotide-gated channels (CNGA and CNGB). Two of the species (the hagfish Eptatretus cirrhatus and the lamprey Mordacia mordax) possess only a single class of photoreceptor, simplifying deductions about the composition of cascade protein isoforms utilized in their photoreceptors. For the other lamprey, Geotria australis, analysis of the ratios of transcript levels in downstream and upstream migrant animals permits tentative conclusions to be drawn about the isoforms used in four of the five spectral classes of photoreceptor. Overall, our results suggest that agnathan rod-like photoreceptors utilize the same GNAT1 as gnathostomes, together with a homodimeric PDE6 that may be agnathan-specific, whereas agnathan cone-like photoreceptors utilize a GNAT that may be agnathan-specific, together with the same PDE6C as gnathostomes. These findings help elucidate the evolution of the vertebrate phototransduction cascade from an ancestral chordate phototransduction cascade that existed prior to the vertebrate radiation.
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Affiliation(s)
- Trevor D Lamb
- Eccles Institute of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, ACT, Australia
| | - Hardip Patel
- Genome Discovery Unit, John Curtin School of Medical Research, Australian National University, Canberra, ACT, Australia Department of Genome Biology, John Curtin School of Medical Research, Australian National University, Canberra, ACT, Australia
| | - Aaron Chuah
- Genome Discovery Unit, John Curtin School of Medical Research, Australian National University, Canberra, ACT, Australia
| | - Riccardo C Natoli
- Eccles Institute of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, ACT, Australia ANU Medical School, Australian National University, Canberra, ACT, Australia
| | - Wayne I L Davies
- School of Animal Biology, University of Western Australia, Perth, WA, Australia Oceans Institute, University of Western Australia, Perth, WA, Australia Lions Eye Institute, University of Western Australia, Perth, WA, Australia
| | - Nathan S Hart
- School of Animal Biology, University of Western Australia, Perth, WA, Australia Oceans Institute, University of Western Australia, Perth, WA, Australia Department of Biological Sciences, Macquarie University, Sydney, NSW, Australia
| | - Shaun P Collin
- School of Animal Biology, University of Western Australia, Perth, WA, Australia Oceans Institute, University of Western Australia, Perth, WA, Australia Lions Eye Institute, University of Western Australia, Perth, WA, Australia
| | - David M Hunt
- School of Animal Biology, University of Western Australia, Perth, WA, Australia Lions Eye Institute, University of Western Australia, Perth, WA, Australia
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45
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Robin J, Brauer J, Sulmann S, Marino V, Dell’Orco D, Lienau C, Koch KW. Differential Nanosecond Protein Dynamics in Homologous Calcium Sensors. ACS Chem Biol 2015. [PMID: 26204433 DOI: 10.1021/acschembio.5b00278] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Shaping the temporal response of photoreceptors is facilitated by a well-balanced second messenger cascade, in which two neuronal Ca(2+)-sensor proteins operate in a sequential relay mechanism. Although they share structurally similar sensing units, they differentially activate the same target protein. Here, as a prototypical case in Ca(2+)-mediated signal processing, we investigate differential cellular responsiveness in protein conformational dynamics on a nanosecond time scale. For this, we have site-specifically labeled cysteine residues in guanylate cyclase-activating protein GCAP1 by the fluorescent dye Alexa647 and probed its local environment via time-resolved fluorescence spectroscopy. Fluorescence lifetime and rotational anisotropy measurements reveal a distinct structural movement of the polypeptide chain around position 106 upon release of Ca(2+). This is supported by analyzing the diffusional dye motion in a wobbling-in-a-cone model and by molecular dynamics simulations. We conclude that GCAP1 and its cellular cognate GCAP2 operate by distinctly different switching mechanisms despite their high structural homology.
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Affiliation(s)
- Jörg Robin
- Ultrafast
Nano-Optics, Institute of Physics, Faculty V, University of Oldenburg, D-26111 Oldenburg, Germany
- Center
of Interface Science, University of Oldenburg, D-26111 Oldenburg, Germany
| | - Jens Brauer
- Ultrafast
Nano-Optics, Institute of Physics, Faculty V, University of Oldenburg, D-26111 Oldenburg, Germany
- Center
of Interface Science, University of Oldenburg, D-26111 Oldenburg, Germany
| | - Stefan Sulmann
- Biochemistry,
Department of Neurosciences, Faculty VI, University of Oldenburg, D-26111 Oldenburg, Germany
| | - Valerio Marino
- Department
of Life Sciences and Reproduction, Section of Biological Chemistry, University of Verona, Verona, Italy
| | - Daniele Dell’Orco
- Department
of Life Sciences and Reproduction, Section of Biological Chemistry, University of Verona, Verona, Italy
- Center
for BioMedical Computing (CBMC), University of Verona, Verona, Italy
| | - Christoph Lienau
- Ultrafast
Nano-Optics, Institute of Physics, Faculty V, University of Oldenburg, D-26111 Oldenburg, Germany
- Center
of Interface Science, University of Oldenburg, D-26111 Oldenburg, Germany
| | - Karl-Wilhelm Koch
- Center
of Interface Science, University of Oldenburg, D-26111 Oldenburg, Germany
- Biochemistry,
Department of Neurosciences, Faculty VI, University of Oldenburg, D-26111 Oldenburg, Germany
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46
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Marino V, Scholten A, Koch KW, Dell'Orco D. Two retinal dystrophy-associated missense mutations in GUCA1A with distinct molecular properties result in a similar aberrant regulation of the retinal guanylate cyclase. Hum Mol Genet 2015; 24:6653-66. [PMID: 26358777 DOI: 10.1093/hmg/ddv370] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Accepted: 09/04/2015] [Indexed: 11/13/2022] Open
Abstract
Two recently identified missense mutations (p. L84F and p. I107T) in GUCA1A, the gene coding for guanylate cyclase (GC)-activating protein 1 (GCAP1), lead to a phenotype ascribable to cone, cone-rod and macular dystrophies. Here, we present a thorough biochemical and biophysical characterization of the mutant proteins and their distinct molecular features. I107T-GCAP1 has nearly wild-type-like protein secondary and tertiary structures, and binds Ca(2+) with a >10-fold lower affinity than the wild-type. On the contrary, L84F-GCAP1 displays altered tertiary structure in both GC-activating and inhibiting states, and a wild type-like apparent affinity for Ca(2+). The latter mutant also shows a significantly high affinity for Mg(2+), which might be important for stabilizing the GC-activating state and inducing a cooperative mechanism for the binding of Ca(2+), so far not been observed in other GCAP1 variants. Moreover, the thermal stability of L84F-GCAP1 is particularly high in the Ca(2+)-bound, GC-inhibiting state. Molecular dynamics simulations suggest that such enhanced stability arises from a deeper burial of the myristoyl moiety within the EF1-EF2 domain. The simulations also support an allosteric mechanism connecting the myristoyl moiety to the highest-affinity Ca(2+) binding site EF3. In spite of their remarkably distinct molecular features, both mutants cause constitutive activation of the target GC at physiological Ca(2+). We conclude that the similar aberrant regulation of the target enzyme results from a similar perturbation of the GCAP1-GC interaction, which may eventually cause dysregulation of both Ca(2+) and cyclic GMP homeostasis and result in retinal degeneration.
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Affiliation(s)
- Valerio Marino
- Department of Neurological, Biomedical and Movement Sciences, Section of Biological Chemistry
| | - Alexander Scholten
- Department of Neurosciences, Biochemistry Group, University of Oldenburg, 26111 Oldenburg, Germany
| | - Karl-Wilhelm Koch
- Department of Neurosciences, Biochemistry Group, University of Oldenburg, 26111 Oldenburg, Germany
| | - Daniele Dell'Orco
- Department of Neurological, Biomedical and Movement Sciences, Section of Biological Chemistry, Centre for BioMedical Computing (CBMC), University of Verona, 37134 Verona, Italy and
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47
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Gurevich EV, Gurevich VV. Beyond traditional pharmacology: new tools and approaches. Br J Pharmacol 2015; 172:3229-41. [PMID: 25572005 DOI: 10.1111/bph.13066] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Revised: 11/24/2014] [Accepted: 01/02/2015] [Indexed: 12/14/2022] Open
Abstract
Traditional pharmacology is defined as the science that deals with drugs and their actions. While small molecule drugs have clear advantages, there are many cases where they have proved to be ineffective, prone to unacceptable side effects, or where due to a particular disease aetiology they cannot possibly be effective. A dominant feature of the small molecule drugs is their single mindedness: they provide either continuous inhibition or continuous activation of the target. Because of that, these drugs tend to engage compensatory mechanisms leading to drug tolerance, drug resistance or, in some cases, sensitization and consequent loss of therapeutic efficacy over time and/or unwanted side effects. Here we discuss new and emerging therapeutic tools and approaches that have potential for treating the majority of disorders for which small molecules are either failing or cannot be developed. These new tools include biologics, such as recombinant hormones and antibodies, as well as approaches involving gene transfer (gene therapy and genome editing) and the introduction of specially designed self-replicating cells. It is clear that no single method is going to be a 'silver bullet', but collectively, these novel approaches hold promise for curing practically every disorder.
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Affiliation(s)
- E V Gurevich
- Department of Pharmacology, Vanderbilt University, Nashville, TN, USA
| | - V V Gurevich
- Department of Pharmacology, Vanderbilt University, Nashville, TN, USA
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48
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Gunkel M, Schöneberg J, Alkhaldi W, Irsen S, Noé F, Kaupp UB, Al-Amoudi A. Higher-order architecture of rhodopsin in intact photoreceptors and its implication for phototransduction kinetics. Structure 2015; 23:628-38. [PMID: 25728926 DOI: 10.1016/j.str.2015.01.015] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Revised: 01/16/2015] [Accepted: 01/22/2015] [Indexed: 12/23/2022]
Abstract
The visual pigment rhodopsin belongs to the family of G protein-coupled receptors that can form higher oligomers. It is controversial whether rhodopsin forms oligomers and whether oligomers are functionally relevant. Here, we study rhodopsin organization in cryosections of dark-adapted mouse rod photoreceptors by cryoelectron tomography. We identify four hierarchical levels of organization. Rhodopsin forms dimers; at least ten dimers form a row. Rows form pairs (tracks) that are aligned parallel to the disk incisures. Particle-based simulation shows that the combination of tracks with fast precomplex formation, i.e. rapid association and dissociation between inactive rhodopsin and the G protein transducin, leads to kinetic trapping: rhodopsin first activates transducin from its own track, whereas recruitment of transducin from other tracks proceeds more slowly. The trap mechanism could produce uniform single-photon responses independent of rhodopsin lifetime. In general, tracks might provide a platform that coordinates the spatiotemporal interaction of signaling molecules.
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Affiliation(s)
- Monika Gunkel
- Department of Molecular Sensory Systems, Center of Advanced European Studies and Research (caesar), Ludwig-Erhard-Allee 2, 53175 Bonn, Germany
| | - Johannes Schöneberg
- Computational Molecular Biology Group, Freie Universität Berlin, Arnimallee 6, 14195 Berlin, Germany
| | - Weaam Alkhaldi
- German Center of Neurodegenerative Diseases, Ludwig-Erhard-Allee 2, 53175 Bonn, Germany
| | - Stephan Irsen
- Department of Molecular Sensory Systems, Center of Advanced European Studies and Research (caesar), Ludwig-Erhard-Allee 2, 53175 Bonn, Germany
| | - Frank Noé
- Computational Molecular Biology Group, Freie Universität Berlin, Arnimallee 6, 14195 Berlin, Germany
| | - U Benjamin Kaupp
- Department of Molecular Sensory Systems, Center of Advanced European Studies and Research (caesar), Ludwig-Erhard-Allee 2, 53175 Bonn, Germany.
| | - Ashraf Al-Amoudi
- German Center of Neurodegenerative Diseases, Ludwig-Erhard-Allee 2, 53175 Bonn, Germany.
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49
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Abstract
Cilia are highly conserved for their structure and also for their sensory functions. They serve as antennae for extracellular information. Whether the cilia are motile or not, they respond to environmental mechanical and chemical stimuli and signal to the cell body. The information from extracellular stimuli is commonly converted to electrical signals through the repertoire of ion-conducting channels in the ciliary membrane resulting in changes in concentrations of ions, especially Ca2+, in the cilia. These changes, in turn, affect motility and signaling pathways in the cilia and cell body to carry on the signal transduction. We review here the activities of ion channels in cilia from protists to vertebrates.
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Affiliation(s)
- Steven J Kleene
- Department of Molecular and Cellular Physiology University of Cincinnati Cincinnati, OH 45267-0576 USA 1-513-558-6099 (phone) 1-513-558-5738 (fax)
| | - Judith L Van Houten
- Department of Biology University of Vermont Burlington, VT 05405, USA 1-802-656-0452 (phone) 1-802-656-2914 (FAX)
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50
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Orlov DN, Nezvetsky AR, Orlova TG, Petrukhin OV, Orlov NY. The phosphorylation state of transducin beta-subunits. Biophysics (Nagoya-shi) 2014. [DOI: 10.1134/s0006350914050194] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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