Journal article
Photochemistry of retinal chromophore in mouse melanopsin
Proceedings of the National Academy of Sciences - PNAS, Vol.105(26), pp.8861-8865
07/01/2008
Handle:
https://hdl.handle.net/2376/110432
PMCID: PMC2449331
PMID: 18579788
Abstract
In mammals, melanopsin is exclusively expressed in intrinsically photosensitive retinal ganglion cells (ipRGCs), which play an important role in circadian photoentrainment and other nonimage-forming functions. These ipRGCs reside in the inner retina, far removed from the pigment epithelium, which synthesizes the 11-
cis
retinal chromophore used by rod and cone photoreceptors to regenerate opsin for light detection. There has been considerable interest in the identification of the melanopsin chromophore and in understanding the process of photopigment regeneration in photoreceptors that are not in proximity to the classical visual cycle. We have devised an immuno-magnetic purification protocol that allows melanopsin-expressing retinal ganglion cells to be isolated and collected from multiple mouse retinas. Using this technique, we have demonstrated that native melanopsin
in vivo
exclusively binds 11-
cis
retinal in the dark and that illumination causes isomerization to the all-
trans
isoform. Furthermore, spectral analysis of the melanopsin photoproduct shows the formation of a protonated metarhodopsin with a maximum absorbance between 520 and 540 nm. These results indicate that even if melanopsin functions as a bistable photopigment with photo-regenerative activity native melanopsin must also use some other light-independent retinoid regeneration mechanism to return to the dark state, where all of the retinal is observed to be in the 11-
cis
form.
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Details
- Title
- Photochemistry of retinal chromophore in mouse melanopsin
- Creators
- Marquis T Walker - Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, MD 21250; andR. Lane Brown - Department of Veterinary and Comparative Anatomy, Pharmacology, and Physiology, Washington State University, Pullman, WA 99164Thomas W Cronin - Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, MD 21250; andPhyllis R Robinson - Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, MD 21250; and
- Publication Details
- Proceedings of the National Academy of Sciences - PNAS, Vol.105(26), pp.8861-8865
- Academic Unit
- Integrative Physiology and Neuroscience, Department of
- Publisher
- National Academy of Sciences
- Identifiers
- 99900547401701842
- Language
- English
- Resource Type
- Journal article