Three Homologous ArfGAPs Participate in Coat Protein I-mediated Transport*
Three Homologous ArfGAPs Participate in Coat Protein I-mediated Transport*
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DOI：
10.1074/jbc.m900749200
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发表时间：
2009-05
影响因子：
4.8
通讯作者：
Akina Saitoh;Hye-Won Shin;A. Yamada;S. Waguri;K. Nakayama
中科院分区：
文献类型：
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作者：
Akina Saitoh;Hye-Won Shin;A. Yamada;S. Waguri;K. Nakayama
ArfGAP1是adp核糖基化因子（ARFs）的gtpase激活蛋白的原型，并被认为通过调节外壳蛋白I （COPI）包被囊泡的脱包参与从高尔基体到内质网（ER）的逆行运输。然而，通过RNA干扰减少ArfGAP1，既不会引起COPI定位的明显表型变化，也不会引起高尔基向内质网逆行转运的变化。因此，我们还研究了ArfGAP1的近亲同源物ArfGAP2和ArfGAP3。ArfGAP1、ArfGAP2和ArfGAP3同时被敲低的细胞显示gtp结合的ARF水平升高。此外，在这些细胞中，包括ERGIC-53、β-COP和GM130在内的蛋白质驻留在或通过顺式高尔基体循环，积聚在er -高尔基体中间区，高尔基体到er的逆行运输被阻断。在ArfGAP三重敲除细胞中观察到的表型与在β- cop缺失细胞中观察到的表型相似。三重ArfGAP-和β- cop -耗尽的细胞都积累了电子显微镜下可见的特征性液泡结构。此外，在arfgap缺失的细胞中，COPI集中在液泡结构的边缘。基于这些观察结果，我们得出结论，ArfGAP1、ArfGAP2和ArfGAP3在高尔基向内质网逆行转运中调节COPI功能具有重叠作用。
ArfGAP1 is a prototype of GTPase-activating proteins for ADP-ribosylation factors (ARFs) and has been proposed to be involved in retrograde transport from the Golgi apparatus to the endoplasmic reticulum (ER) by regulating the uncoating of coat protein I (COPI)-coated vesicles. Depletion of ArfGAP1 by RNA interference, however, causes neither a discernible phenotypic change in the COPI localization nor a change in the Golgi-to-ER retrograde transport. Therefore, we also examined ArfGAP2 and ArfGAP3, closely related homologues of ArfGAP1. Cells in which ArfGAP1, ArfGAP2, and ArfGAP3 are simultaneously knocked down show an increase in the GTP-bound ARF level. Furthermore, in these cells proteins resident in or cycling through the cis-Golgi, including ERGIC-53, β-COP, and GM130, accumulate in the ER-Golgi intermediate compartment, and Golgi-to-ER retrograde transport is blocked. The phenotypes observed in the triple ArfGAP knockdown cells are similar to those seen in β-COP-depleted cells. Both the triple ArfGAP- and β-COP-depleted cells accumulate characteristic vacuolar structures that are visible under electron microscope. Furthermore, COPI is concentrated at rims of the vacuolar structures in the ArfGAP-depleted cells. On the basis of these observations, we conclude that ArfGAP1, ArfGAP2, and ArfGAP3 have overlapping roles in regulating COPI function in Golgi-to-ER retrograde transport.