Hannah Matthew J, Hume Alistair N, Arribas Monica, Williams Ross, Hewlett Lindsay J, Seabra Miguel C, Cutler Daniel F
MRC Laboratory of Molecular Cell Biology, Cell Biology Unit, University College London, Gower St, London WC1E 6BT, UK.
J Cell Sci. 2003 Oct 1;116(Pt 19):3939-48. doi: 10.1242/jcs.00711. Epub 2003 Aug 19.
The identification of organelles is crucial for efficient cellular function, yet the basic underlying mechanisms by which this might occur have not been established. One group of proteins likely to be central to organelle identity is the Rab family of small GTPases. We have thus investigated Rab recruitment to membranes using endothelial cells as a model system. We report that Weibel-Palade bodies, the Von Willebrand Factor storage compartment of human umbilical vein endothelial cells, contain Rab27a. We have also found that Weibel-Palade body-like structures induced in HEK-293 cells by the expression of von Willebrand factor can recruit endogenous Rab27a. In the absence of von Willebrand Factor, Rab27a is not lysosome associated, indicating that it can distinguish between the Weibel-Palade-body-like organelle and a classical lysosome. Finally, a time course of Weibel-Palade-body formation was established using a green-fluorescent version of von Willebrand factor. Newly formed Weibel-Palade bodies lack Rab27a, which is acquired some hours after initial appearance of the cigar-shaped organelle. We conclude that a lumenal cargo protein drives the recruitment of Rab27a to the organelle membrane by a novel mechanism that is indirect, maturation-dependent and cell-type independent.
细胞器的识别对于细胞高效发挥功能至关重要，然而其背后可能的基本机制尚未明确。一类可能对细胞器识别起核心作用的蛋白质是小GTP酶的Rab家族。因此，我们以内皮细胞作为模型系统，研究了Rab蛋白向膜的募集情况。我们发现，人脐静脉内皮细胞中储存血管性血友病因子的魏尔-帕拉德小体含有Rab27a。我们还发现，在HEK-293细胞中通过表达血管性血友病因子诱导形成的类魏尔-帕拉德小体结构可以募集内源性Rab27a。在没有血管性血友病因子的情况下，Rab27a与溶酶体不相关，这表明它能够区分类魏尔-帕拉德小体细胞器和经典的溶酶体。最后，我们利用血管性血友病因子的绿色荧光版本建立了魏尔-帕拉德小体形成的时间进程。新形成的魏尔-帕拉德小体缺乏Rab27a，Rab27a是在雪茄状细胞器最初出现数小时后才获得的。我们得出结论，腔内货物蛋白通过一种间接的、成熟依赖的且细胞类型无关的新机制驱动Rab27a募集到细胞器膜上。
