Modica Graziana, Skorobogata Olga, Sauvageau Etienne, Vissa Adriano, Yip Christopher M, Kim Peter K, Wurtele Hugo, Lefrancois Stephane
Centre INRS-Institut Armand-Frappier, Institut National de la Recherche Scientifique, Laval, Québec H7V 1B7, Canada.
Program in Cell Biology, The Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada.
J Cell Sci. 2017 Aug 1;130(15):2579-2590. doi: 10.1242/jcs.199729. Epub 2017 Jun 9.
Retromer is a multimeric protein complex that mediates endosome-to-trans-Golgi network (TGN) and endosome-to-plasma membrane trafficking of integral membrane proteins. Dysfunction of this complex has been linked to Alzheimer's disease and Parkinson's disease. The recruitment of retromer to endosomes is regulated by Rab7 (also known as RAB7A) to coordinate endosome-to-TGN trafficking of cargo receptor complexes. Rab7 is also required for the degradation of internalized integral membrane proteins, such as the epidermal growth factor receptor (EGFR). We found that Rab7 is palmitoylated and that this modification is not required for membrane anchoring. Palmitoylated Rab7 colocalizes efficiently with and has a higher propensity to interact with retromer than nonpalmitoylatable Rab7. Rescue of Rab7 knockout cells by expressing wild-type Rab7 restores efficient endosome-to-TGN trafficking, while rescue with nonpalmitoylatable Rab7 does not. Interestingly, Rab7 palmitoylation does not appear to be required for the degradation of EGFR or for its interaction with its effector, Rab-interacting lysosomal protein (RILP). Overall, our results indicate that Rab7 palmitoylation is required for the spatiotemporal recruitment of retromer and efficient endosome-to-TGN trafficking of the lysosomal sorting receptors.
回收体是一种多聚体蛋白复合物，介导整合膜蛋白从内体到反式高尔基体网络（TGN）以及从内体到质膜的运输。该复合物功能异常与阿尔茨海默病和帕金森病有关。Rab7（也称为RAB7A）调节回收体向内体的募集，以协调货物受体复合物从内体到TGN的运输。Rab7对于内化的整合膜蛋白（如表皮生长因子受体（EGFR））的降解也是必需的。我们发现Rab7被棕榈酰化，并且这种修饰对于膜锚定不是必需的。与不可棕榈酰化的Rab7相比，棕榈酰化的Rab7与回收体高效共定位并且与其相互作用的倾向更高。通过表达野生型Rab7挽救Rab7基因敲除细胞可恢复从内体到TGN的高效运输，而用不可棕榈酰化的Rab7进行挽救则不能。有趣的是，Rab7棕榈酰化似乎对于EGFR的降解或其与其效应器Rab相互作用溶酶体蛋白（RILP）的相互作用不是必需的。总体而言，我们的结果表明，Rab7棕榈酰化对于回收体的时空募集以及溶酶体分选受体从内体到TGN的高效运输是必需的。
