PROMOTION OF THE RELEASE OF 11-CIS-RETINAL FROM CULTURED RETINAL-PIGMENT EPITHELIUM BY INTERPHOTORECEPTOR RETINOID-BINDING PROTEIN
PROMOTION OF THE RELEASE OF 11-CIS-RETINAL FROM CULTURED RETINAL-PIGMENT EPITHELIUM BY INTERPHOTORECEPTOR RETINOID-BINDING PROTEIN
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DOI：
10.1021/bi00152a049
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发表时间：
1992-09-22
期刊：
影响因子：
2.9
通讯作者：
BOK, D
中科院分区：
文献类型：
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作者：
CARLSON, A;BOK, D
本研究探讨光感受器间类视黄醇结合蛋白(IRBP)是否对11-顺式视黄醛(Ral)的释放是必需的，或者类视黄酸是否在合成后从视网膜色素上皮(RPE)中结构性地释放出来。IRBP在光感受器间基质(IPM)中的战略位置和它与维甲酸的结合能力使其成为11-环状释放的候选角色。将胎牛RPE细胞培养在可渗透的小室中，其顶端表面分别加入含apo-IRBP、apo形式的细胞视黄醛结合蛋白(CRALBP)、apo形式的血清视黄醇结合蛋白(RBP)或牛血清白蛋白(BSA)的培养液或不含结合蛋白的培养液。用RBP将[H-3]-全反式视黄醇(ROL)输送到细胞基底面。高效液相色谱分析表明，当apo-IRBP存在时，[H-3]-11-cis-ral被最佳地释放到顶端培养液中。最令人惊讶的结果是当apo-CRALBP在根尖中时，[H-3]-11-cis-al的水平降低。圆二色谱表明，CRALBP没有被内源配体去除所需的光漂白变性。因此，如果apo-CRALBP被结构性地释放到根尖介质中，它应该能够结合[H-3]-11-顺式。此外，当存在apo-IRBP以外的蛋白质时，或者如果细胞单独与培养液孵育，顶端[H-3]-11-顺式的减少伴随着细胞内[H-3]-全反式视黄酸棕榈酸酯和[H-3]-全反式-ROL在基础培养液中的积累。综上所述，这些结果提示IRBP可能通过RPE根尖膜上的受体参与[H-3]-11-cis-ral的心尖释放。
This study investigates whether the interphotoreceptor retinoid-binding protein (IRBP) is necessary for the release of 11-cis-retinaldehyde (RAL) or if the retinoid is constitutively released from the retinal pigment epithelium (RPE) following synthesis. The strategic location of IRBP in the interphotoreceptor matrix (IPM) and its retinoid-binding ability make it a candidate for a role in 11-cis-RAL release. Fetal bovine RPE cells were grown in permeable chambers, and their apical surfaces were incubated with medium containing either apo-IRBP, the apo form of cellular retinaldehyde-binding protein (CRALBP), the apo form of serum retinol-binding protein (RBP), or bovine serum albumin (BSA) or with medium devoid of binding proteins. [H-3]-all-trans-Retinol (ROL) was delivered to the basal surface of the cells by RBP. High-performance liquid chromatography demonstrated that [H-3]-11-cis-RAL was optimally released into the apical medium when apo-IRBP was present. The most surprising result was the diminished level of [H-3]-11-cis-RAL when apo-CRALBP was in the apical medium. Circular dichroism demonstrated that CRALBP had not been denatured by the photobleaching required for endogenous ligand removal. Therefore, apo-CRALBP should have been able to bind [H-3]-11-cis-RAL if it was constitutively released into the apical medium. In addition, when proteins other than apo-IRBP were present, or if the cells were incubated with medium alone, the observed decrease in apical [H-3]-11-cis-RAL was concomitant with a buildup of intracellular [H-3]-all-trans-retinyl palmitate and [H-3]-all-trans-ROL in the basal culture medium. Together these results suggest that IRBP is actively involved in the apical release of [H-3]-11-cis-RAL, perhaps via a receptor in the RPE apical membrane.