Noninvasive two-photon imaging reveals retinyl ester storage structures in the eye |
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Authors: | Imanishi Yoshikazu Batten Matthew L Piston David W Baehr Wolfgang Palczewski Krzysztof |
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Institution: | Department of Ophthalmology, University of Washington, 1959 NE Pacific St., Box 356485, Seattle, WA 98195-6485, USA. |
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Abstract: | Visual sensation in vertebrates is triggered when light strikes retinal photoreceptor cells causing photoisomerization of the rhodopsin chromophore 11-cis-retinal to all-trans-retinal. The regeneration of preillumination conditions of the photoreceptor cells requires formation of 11-cis-retinal in the adjacent retinal pigment epithelium (RPE). Using the intrinsic fluorescence of all-trans-retinyl esters, noninvasive two-photon microscopy revealed previously uncharacterized structures (6.9 +/- 1.1 microm in length and 0.8 +/- 0.2 microm in diameter) distinct from other cellular organelles, termed the retinyl ester storage particles (RESTs), or retinosomes. These structures form autonomous all-trans-retinyl ester-rich intracellular compartments distinct from other organelles and colocalize with adipose differentiation-related protein. As demonstrated by in vivo experiments using wild-type mice, the RESTs participate in 11-cis-retinal formation. RESTs accumulate in Rpe65-/- mice incapable of carrying out the enzymatic isomerization, and correspondingly, are absent in the eyes of Lrat-/- mice deficient in retinyl ester synthesis. These results indicate that RESTs located close to the RPE plasma membrane are essential components in 11-cis-retinal production. |
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Keywords: | retinoid cycle photoreceptor cells two-photon microscopy retinal pigment epithelial cells rhodopsin |
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