Reduction of All-trans-retinal in Vertebrate Rod Photoreceptors Requires the Combined Action of RDH8 and RDH12
Reduction of All-trans-retinal in Vertebrate Rod Photoreceptors Requires the Combined Action of RDH8 and RDH12
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DOI：
10.1074/jbc.m112.354514
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发表时间：
2012-07-13
影响因子：
4.8
通讯作者：
Koutalos, Yiannis
中科院分区：
文献类型：
--
作者：
Chen, Chunhe;Thompson, Debra A.;Koutalos, Yiannis
在脊椎动物视杆细胞中，类视黄醇脱氢酶/还原酶 (RDH) 对于将光激活视紫红质释放的反应性醛全反式视黄醛还原为全反式视黄醇（维生素 A）至关重要。先前的研究表明，RDH8 定位于光感受器外节，是发挥这一作用的有力候选者。然而，光感受器内段的 RDH12 功能也很关键，因为功能缺失突变会导致某些形式的莱伯先天性黑蒙的视网膜变性。为了研究 RDH8 和 RDH12 的体内作用，我们使用荧光成像来检查来自野生型小鼠和缺乏一种或两种 RDH 的敲除小鼠的单个分离杆状细胞中全反式视黄醇的产生。缺乏 Rdh8 的视杆细胞外段未能减少全反式视网膜，但缺乏 Rdh12 的视杆细胞外段则不受影响。暴露于光后，在野生型和基因敲除小鼠的视杆细胞中检测到类维生素A从外节向内节的泄漏。在缺乏 Rdh8 或 Rdh12 的细胞中，这种泄漏主要是全反式视网膜。与全反式视网膜一起孵育的野生型视杆细胞减少了细胞内部视网膜的中等负荷，但这种能力因 Rdh8 或 Rdh12 缺陷的细胞而丧失。我们的研究结果与 RDH8 定位于外节相一致，它提供了减少光响应产生的全反式视网膜所需的大部分活性。相比之下，内节中的 RDH12 可以保护重要的细胞器免受全反式视网膜细胞内泄漏以及源自细胞内外的其他醛引起的醛毒性。
In vertebrate rod cells, retinoid dehydrogenases/reductases (RDHs) are critical for reducing the reactive aldehyde all-trans-retinal that is released by photoactivated rhodopsin, to all-trans-retinol (vitamin A). Previous studies have shown that RDH8 localizes to photoreceptor outer segments and is a strong candidate for performing this role. However, RDH12 function in the photoreceptor inner segments is also key, because loss of function mutations cause retinal degeneration in some forms of Leber congenital amaurosis. To investigate the in vivo roles of RDH8 and RDH12, we used fluorescence imaging to examine all-trans-retinol production in single isolated rod cells from wild-type mice and knock-out mice lacking either one or both RDHs. Outer segments of rods deficient in Rdh8 failed to reduce all-trans-retinal, but those deficient in Rdh12 were unaffected. Following exposure to light, a leak of retinoids from outer to inner segments was detected in rods from both wild-type and knock-out mice. In cells lacking Rdh8 or Rdh12, this leak was mainly all-trans-retinal. Wild-type rods incubated with all-trans-retinal reduced moderate loads of retinal within the cell interior, but this ability was lost by cells deficient in Rdh8 or Rdh12. Our findings are consistent with localization of RDH8 to the outer segment where it provides most of the activity needed to reduce all-trans-retinal generated by the light response. In contrast, RDH12 in inner segments can protect vital cell organelles against aldehyde toxicity caused by an intracellular leak of all-trans-retinal, as well as other aldehydes originating both inside and outside the cell.