Noninvasive two-photon imaging reveals retinyl ester storage structures in the eye

Y Imanishi, ML Batten, DW Piston, W Baehr… - The Journal of cell …, 2004 - rupress.org
The Journal of cell biology, 2004rupress.org
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 μm in length and 0.8±0.2 μm in diameter) …
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 μm in length and 0.8 ± 0.2 μm 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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