Colley N J, Baker E K, Stamnes M A, Zuker C S
Howard Hughes Medical Institute University of California, San Diego, La Jolla 92093.
Cell. 1991 Oct 18;67(2):255-63. doi: 10.1016/0092-8674(91)90177-z.
In Drosophila, the major rhodopsin Rh1 is synthesized in endoplasmic reticulum (ER)-bound ribosomes of the R1-R6 photoreceptor cells and is then transported to the rhabdomeres where it functions in phototransduction. Mutations in the cyclophilin homolog ninaA lead to a 90% reduction in Rh1 opsin. Cyclophilins have been shown to be peptidyl-prolyl cis-trans isomerases and have been implicated in catalyzing protein folding. We now show that mutations in the ninaA gene severely inhibit opsin transport from the ER, leading to dramatic accumulations of ER cisternae in the photoreceptor cells. These results demonstrate that ninaA functions in the ER. Interestingly, ninaA and Rh1 also colocalize to secretory vesicles, suggesting that Rh1 may require ninaA as it travels through the distal compartments of the secretory pathway. These results are discussed in relation to the possible role of cyclophilins in protein folding and intracellular protein trafficking.
在果蝇中，主要视紫红质Rh1在内质网（ER）结合的R1 - R6光感受器细胞核糖体中合成，然后被转运到微绒毛，在那里它参与光转导。亲环蛋白同源物ninaA中的突变导致Rh1视蛋白减少90%。亲环蛋白已被证明是肽基脯氨酰顺反异构酶，并参与催化蛋白质折叠。我们现在表明，ninaA基因中的突变严重抑制视蛋白从内质网的转运，导致光感受器细胞中内质网池的大量积累。这些结果表明ninaA在内质网中发挥作用。有趣的是，ninaA和Rh1也共定位于分泌小泡，这表明Rh1在通过分泌途径的远端区室时可能需要ninaA。本文结合亲环蛋白在蛋白质折叠和细胞内蛋白质运输中的可能作用对这些结果进行了讨论。
