Shedding new light on the generation of the visual chromophore

The visual phototransduction cascade begins with a cis–trans photoisomerization of a retinylidene chromophore associated with the visual pigments of rod and cone photoreceptors. Visual opsins release their all-trans-retinal chromophore following photoactivation, which necessitates the existence of p...

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Published inProceedings of the National Academy of Sciences - PNAS Vol. 117; no. 33; pp. 19629 - 19638
Main Authors Palczewski, Krzysztof, Kiser, Philip D.
Format Journal Article
LanguageEnglish
Published United States National Academy of Sciences 18.08.2020
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Summary:The visual phototransduction cascade begins with a cis–trans photoisomerization of a retinylidene chromophore associated with the visual pigments of rod and cone photoreceptors. Visual opsins release their all-trans-retinal chromophore following photoactivation, which necessitates the existence of pathways that produce 11-cis-retinal for continued formation of visual pigments and sustained vision. Proteins in the retinal pigment epithelium (RPE), a cell layer adjacent to the photoreceptor outer segments, form the well-established “dark” regeneration pathway known as the classical visual cycle. This pathway is sufficient to maintain continuous rod function and support cone photoreceptors as well although its throughput has to be augmented by additional mechanism(s) to maintain pigment levels in the face of high rates of photon capture. Recent studies indicate that the classical visual cycle works together with light-dependent processes in both the RPE and neural retina to ensure adequate 11-cis-retinal production under natural illuminances that can span ten orders of magnitude. Further elucidation of the interplay between these complementary systems is fundamental to understanding how cone-mediated vision is sustained in vivo. Here, we describe recent advances in understanding how 11-cis-retinal is synthesized via light-dependent mechanisms.
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Edited by Jeremy Nathans, Johns Hopkins University School of Medicine, Baltimore, MD, and approved July 9, 2020 (received for review May 16, 2020)
Author contributions: K.P. and P.D.K. wrote the paper.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.2008211117