Shetty K M, Kurada P, O'Tousa J E
Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana 46556, USA.
J Biol Chem. 1998 Aug 7;273(32):20425-30. doi: 10.1074/jbc.273.32.20425.
Rab6 is a GTP binding protein that regulates vesicular trafficking within the Golgi and post-Golgi compartments. We overexpressed wild-type, a GTPase defective (Q71L), and a guanine nucleotide binding defective (N125I) Rab6 protein in Drosophila photoreceptors to assess the in vivo role of Rab6 in the trafficking of rhodopsin and other proteins. Expression of Drab6(Q71L) greatly reduced the steady state levels of two rhodopsins, Rh1 and Rh3, whereas Drab6(wt) and Drab6(N125I) showed weaker effects. Analysis of a strain carrying Rh1 rhodopsin under a heat shock promoter showed that Drab6(Q71L), but not Drab6(wt) or Drab6(N125I), prevents the maturation of rhodopsin beyond an immature 40 kDa form. Drab6(Q71L) is a GTPase defective mutant, indicating that anterograde transport of rhodopsin requires Rab6 GTPase function. The three Drab6 strains had no effect on the expression of several other photoreceptor proteins. The Drab6(Q71L) photoreceptors show marked histological defects at young ages and degenerate over a two week time span. These results establish that rhodopsin is transported via a Rab6 regulated pathway and that defects in trafficking pathways lead to retinal degeneration.
Rab6是一种GTP结合蛋白，可调节高尔基体和高尔基体后区室内的囊泡运输。我们在果蝇光感受器中过表达野生型、GTP酶缺陷型（Q71L）和鸟嘌呤核苷酸结合缺陷型（N125I）Rab6蛋白，以评估Rab6在视紫红质和其他蛋白运输中的体内作用。Drab6（Q71L）的表达大大降低了两种视紫红质Rh1和Rh3的稳态水平，而Drab6（wt）和Drab6（N125I）的作用较弱。对在热休克启动子下携带Rh1视紫红质的菌株进行分析表明，Drab6（Q71L）而非Drab6（wt）或Drab6（N125I）会阻止视紫红质成熟超过未成熟的40 kDa形式。Drab6（Q71L）是一种GTP酶缺陷型突变体，表明视紫红质的顺向运输需要Rab6 GTP酶功能。这三种Drab6菌株对其他几种光感受器蛋白的表达没有影响。Drab6（Q71L）光感受器在幼年时表现出明显的组织学缺陷，并在两周时间内退化。这些结果表明，视紫红质通过Rab6调节的途径运输，运输途径的缺陷会导致视网膜退化。
