Drosophila photoreceptor cells are employed as a model system for studying membrane protein transport. Phototransduction proteins like rhodopsin and the light-activated TRPL ion channel are transported within the photoreceptor cell, and they change their subcellular distribution in a light-dependent way. Investigating the transport mechanisms for rhodopsin and ion channels requires accurate histochemical methods for protein localization. By using immunocytochemistry the light-triggered translocation of TRPL has been described as a two-stage process. In stage 1, TRPL accumulates at the rhabdomere base and the adjacent stalk membrane a few minutes after onset of illumination and is internalized in stage 2 by endocytosis after prolonged light exposure. Here, we show that a commonly observed crescent shaped antibody labeling pattern suggesting a fast translocation of rhodopsin, TRP, and TRPL to the rhabdomere base is a light-dependent antibody staining artifact. This artifact is most probably caused by the profound structural changes in the microvillar membranes of rhabdomeres that result from activation of the signaling cascade. By using alternative labeling methods, either eGFP-tags or the self-labeling SNAP-tag, we show that light activation of TRPL transport indeed results in fast changes of the TRPL distribution in the rhabdomere but not in the way described previously.

中文翻译：

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在果蝇感光细胞中的横纹肌蛋白的免疫细胞化学标记受到光依赖性技术伪像的损害。

果蝇感光细胞被用作研究膜蛋白转运的模型系统。像视紫红质和光激活的TRPL离子通道这样的光转导蛋白在感光细胞内运输，它们以光依赖的方式改变其亚细胞分布。研究视紫红质和离子通道的转运机制需要精确的组织化学方法进行蛋白质定位。通过使用免疫细胞化学，TRPL的光触发易位已被描述为两个阶段的过程。在阶段1中，TRPL在光照开始后几分钟积聚在鼠李糖基和邻近的茎膜上，并且在阶段2中，长时间暴露后通过胞吞作用而被内在化。这里，我们表明，通常观察到的新月形抗体标记模式表明视紫红质，TRP和TRPL快速转移到弹状基础上是一种光依赖性抗体染色伪影。这种伪影很可能是由于激活信号级联反应导致的横纹肌微绒毛膜的深刻结构变化引起的。通过使用eGFP标签或自标记SNAP标签的替代标记方法，我们表明TRPL转运的光激活确实会导致弹状绒毛中TRPL分布的快速变化，但并非以前面描述的方式。这种伪影很可能是由于激活信号级联反应导致的横纹肌微绒毛膜的深刻结构变化引起的。通过使用eGFP标签或自标记SNAP标签的替代标记方法，我们表明TRPL转运的光激活确实会导致弹状绒毛中TRPL分布的快速变化，但并非以前面描述的方式。这种伪影很可能是由信号级联反应激活导致的横纹肌微绒毛膜的深刻结构变化引起的。通过使用eGFP标签或自标记SNAP标签的替代标记方法，我们表明TRPL转运的光激活确实会导致弹状绒毛中TRPL分布的快速变化，但并非以前面描述的方式。