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Turning Cones Off: the Role of the 9-Methyl Group of Retinal in Red Cones

Our ability to see in bright light depends critically on the rapid rate at which cone photoreceptors detect and adapt to changes in illumination. This is achieved, in part, by their rapid response termination. In this study, we investigate the hypothesis that this rapid termination of the response i...

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Autores principales: Estevez, Maureen E., Ala-Laurila, Petri, Crouch, Rosalie K., Cornwall, M. Carter
Formato: Texto
Lenguaje:English
Publicado: The Rockefeller University Press 2006
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2151603/
https://www.ncbi.nlm.nih.gov/pubmed/17101818
http://dx.doi.org/10.1085/jgp.200609630
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author Estevez, Maureen E.
Ala-Laurila, Petri
Crouch, Rosalie K.
Cornwall, M. Carter
author_facet Estevez, Maureen E.
Ala-Laurila, Petri
Crouch, Rosalie K.
Cornwall, M. Carter
author_sort Estevez, Maureen E.
collection PubMed
description Our ability to see in bright light depends critically on the rapid rate at which cone photoreceptors detect and adapt to changes in illumination. This is achieved, in part, by their rapid response termination. In this study, we investigate the hypothesis that this rapid termination of the response in red cones is dependent on interactions between the 9-methyl group of retinal and red cone opsin, which are required for timely metarhodopsin (Meta) II decay. We used single-cell electrical recordings of flash responses to assess the kinetics of response termination and to calculate guanylyl cyclase (GC) rates in salamander red cones containing native visual pigment as well as visual pigment regenerated with 11-cis 9-demethyl retinal, an analogue of retinal in which the 9-methyl group is missing. After exposure to bright light that photoactivated more than ∼0.2% of the pigment, red cones containing the analogue pigment had a slower recovery of both flash response amplitudes and GC rates (up to 10 times slower at high bleaches) than red cones containing 11-cis retinal. This finding is consistent with previously published biochemical data demonstrating that red cone opsin regenerated in vitro with 11-cis 9-demethyl retinal exhibited prolonged activation as a result of slowed Meta II decay. Our results suggest that two different mechanisms regulate the recovery of responsiveness in red cones after exposure to light. We propose a model in which the response recovery in red cones can be regulated (particularly at high light intensities) by the Meta II decay rate if that rate has been inhibited. In red cones, the interaction of the 9-methyl group of retinal with opsin promotes efficient Meta II decay and, thus, the rapid rate of recovery.
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spelling pubmed-21516032008-01-17 Turning Cones Off: the Role of the 9-Methyl Group of Retinal in Red Cones Estevez, Maureen E. Ala-Laurila, Petri Crouch, Rosalie K. Cornwall, M. Carter J Gen Physiol Articles Our ability to see in bright light depends critically on the rapid rate at which cone photoreceptors detect and adapt to changes in illumination. This is achieved, in part, by their rapid response termination. In this study, we investigate the hypothesis that this rapid termination of the response in red cones is dependent on interactions between the 9-methyl group of retinal and red cone opsin, which are required for timely metarhodopsin (Meta) II decay. We used single-cell electrical recordings of flash responses to assess the kinetics of response termination and to calculate guanylyl cyclase (GC) rates in salamander red cones containing native visual pigment as well as visual pigment regenerated with 11-cis 9-demethyl retinal, an analogue of retinal in which the 9-methyl group is missing. After exposure to bright light that photoactivated more than ∼0.2% of the pigment, red cones containing the analogue pigment had a slower recovery of both flash response amplitudes and GC rates (up to 10 times slower at high bleaches) than red cones containing 11-cis retinal. This finding is consistent with previously published biochemical data demonstrating that red cone opsin regenerated in vitro with 11-cis 9-demethyl retinal exhibited prolonged activation as a result of slowed Meta II decay. Our results suggest that two different mechanisms regulate the recovery of responsiveness in red cones after exposure to light. We propose a model in which the response recovery in red cones can be regulated (particularly at high light intensities) by the Meta II decay rate if that rate has been inhibited. In red cones, the interaction of the 9-methyl group of retinal with opsin promotes efficient Meta II decay and, thus, the rapid rate of recovery. The Rockefeller University Press 2006-12 /pmc/articles/PMC2151603/ /pubmed/17101818 http://dx.doi.org/10.1085/jgp.200609630 Text en Copyright © 2006, The Rockefeller University Press This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/).
spellingShingle Articles
Estevez, Maureen E.
Ala-Laurila, Petri
Crouch, Rosalie K.
Cornwall, M. Carter
Turning Cones Off: the Role of the 9-Methyl Group of Retinal in Red Cones
title Turning Cones Off: the Role of the 9-Methyl Group of Retinal in Red Cones
title_full Turning Cones Off: the Role of the 9-Methyl Group of Retinal in Red Cones
title_fullStr Turning Cones Off: the Role of the 9-Methyl Group of Retinal in Red Cones
title_full_unstemmed Turning Cones Off: the Role of the 9-Methyl Group of Retinal in Red Cones
title_short Turning Cones Off: the Role of the 9-Methyl Group of Retinal in Red Cones
title_sort turning cones off: the role of the 9-methyl group of retinal in red cones
topic Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2151603/
https://www.ncbi.nlm.nih.gov/pubmed/17101818
http://dx.doi.org/10.1085/jgp.200609630
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