Imanishi Yoshikazu, Batten Matthew L, Piston David W, Baehr Wolfgang, Palczewski Krzysztof
Department of Ophthalmology, University of Washington, 1959 NE Pacific St., Box 356485, Seattle, WA 98195-6485, USA.
J Cell Biol. 2004 Feb 2;164(3):373-83. doi: 10.1083/jcb.200311079. Epub 2004 Jan 26.
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.
当光线照射视网膜光感受器细胞，导致视紫红质发色团11-顺式视黄醛光异构化为全反式视黄醛时，脊椎动物的视觉感觉就会被触发。光感受器细胞恢复光照前的状态需要在相邻的视网膜色素上皮（RPE）中形成11-顺式视黄醛。利用全反式视黄酯的固有荧光，无创双光子显微镜揭示了与其他细胞器不同的、以前未被表征的结构（长度为6.9±1.1微米，直径为0.8±0.2微米），称为视黄酯储存颗粒（RESTs）或视网膜小体。这些结构形成了与其他细胞器不同的、富含全反式视黄酯的自主细胞内区室，并与脂肪分化相关蛋白共定位。通过使用野生型小鼠的体内实验证明，RESTs参与11-顺式视黄醛的形成。RESTs在无法进行酶促异构化的Rpe65-/-小鼠中积累，相应地，在视黄酯合成缺陷的Lrat-/-小鼠的眼睛中不存在。这些结果表明，位于RPE质膜附近的RESTs是11-顺式视黄醛产生的重要组成部分。
