Optineurin mediates a negative regulation of Rab8 by the GTPase-activating protein TBC1D17
Optineurin mediates a negative regulation of Rab8 by the GTPase-activating protein TBC1D17
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DOI：
10.1242/jcs.102327
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发表时间：
2012-11
影响因子：
4
通讯作者：
Vipul Vaibhava;A. Nagabhushana;M. Chalasani;C. Sudhakar;A. Kumari;G. Swarup
中科院分区：
文献类型：
--
作者：
Vipul Vaibhava;A. Nagabhushana;M. Chalasani;C. Sudhakar;A. Kumari;G. Swarup
摘要Rab GTP酶调节多种膜转运途径，但GTP酶激活蛋白识别特定RAB的机制尚不清楚。Rab8参与了几个转运过程的控制，包括转铁蛋白受体从早期内体到循环内体的转运。在这里，我们提供的证据表明，TbC1D17是一种Rab GTP酶激活蛋白，通过其催化活性调节Rab8介导的转铁蛋白受体的胞内转运。Optineurin是一种与Rab8结合的效应蛋白，它介导了TBC1D17与Rab8的相互作用和共定位。与视神经磷酸酶直接相互作用需要一个非催化区的TBC1D17。共表达的Rab8，而不是其他测试的RAB，挽救了TBC1D17对转铁蛋白受体运输的抑制。激活的GTP结合形式的Rab8定位于从内吞循环室发出的小管。通过其催化活性，TBC1D17抑制Rab8在小管上的募集，并减少转铁蛋白受体和Rab8的共存。敲除optineurin或TBC1D17会导致Rab8在小管上的募集增加。与青光眼相关的视神经磷酸酶突变体E50K导致TBC1D17对Rab8的抑制作用增强，导致转铁蛋白受体内吞循环缺陷。我们的结果表明，TBC1D17通过与视神经磷酸酶的相互作用，调节了Rab8介导的转铁蛋白受体的内吞循环和Rab8向内吞循环小管的募集。我们描述了一种通过效应蛋白(Optineurin)调节Rab GTP酶的机制，该效应蛋白作为适配器将Rab(Rab8)及其GTP酶激活蛋白(TBC1D17)结合在一起。
Summary Rab GTPases regulate various membrane trafficking pathways but the mechanisms by which GTPase-activating proteins recognise specific Rabs are not clear. Rab8 is involved in controlling several trafficking processes, including the trafficking of transferrin receptor from the early endosome to the recycling endosome. Here, we provide evidence to show that TBC1D17, a Rab GTPase-activating protein, through its catalytic activity, regulates Rab8-mediated endocytic trafficking of transferrin receptor. Optineurin, a Rab8-binding effector protein, mediates the interaction and colocalisation of TBC1D17 with Rab8. A non-catalytic region of TBC1D17 is required for direct interaction with optineurin. Co-expression of Rab8, but not other Rabs tested, rescues the inhibition of transferrin receptor trafficking by TBC1D17. The activated GTP-bound form of Rab8 is localised to the tubules emanating from the endocytic recycling compartment. Through its catalytic activity, TBC1D17 inhibits recruitment of Rab8 to the tubules and reduces colocalisation of transferrin receptor and Rab8. Knockdown of optineurin or TBC1D17 results in enhanced recruitment of Rab8 to the tubules. A glaucoma-associated mutant of optineurin, E50K, causes enhanced inhibition of Rab8 by TBC1D17, resulting in defective endocytic recycling of transferrin receptor. Our results show that TBC1D17, through its interaction with optineurin, regulates Rab8-mediated endocytic recycling of transferrin receptor and recruitment of Rab8 to the endocytic recycling tubules. We describe a mechanism of regulating a Rab GTPase by an effector protein (optineurin) that acts as an adaptor to bring together a Rab (Rab8) and its GTPase-activating protein (TBC1D17).