The Golgi-Localized Arabidopsis Endomembrane Protein12 Contains Both Endoplasmic Reticulum Export and Golgi Retention Signals at Its C Terminus
The Golgi-Localized Arabidopsis Endomembrane Protein12 Contains Both Endoplasmic Reticulum Export and Golgi Retention Signals at Its C Terminus
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DOI：
10.1105/tpc.112.096057
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发表时间：
2012-05-01
期刊：
影响因子：
11.6
通讯作者：
Jiang, Liwen
中科院分区：
文献类型：
--
作者：
Gao, Caiji;Yu, Christine K. Y.;Jiang, Liwen
在酵母和哺乳动物细胞中，EMPs属于进化上保守的跨膜9超家族，其特征是存在一个大的管腔N端，9个跨膜结构域和一个短的细胞质尾部。拟南芥基因组包含12个EMP成员（EMP1至EMP12），但对其蛋白亚细胞定位和功能知之甚少。本文研究了EMP12在拟南芥中的亚细胞定位和靶向机制，结果表明：(1)在转基因拟南芥植物中，内源性EMP12（通过EMP12抗体检测）和绿色荧光蛋白(GFP)-EMP12融合定位于高尔基体；(2)在拟南芥细胞中，EMP12 C端的GFP融合导致EMP12-GFP错误定位到达高尔基后腔室和液泡进行降解；(3) EMP12细胞质尾部包含双重分选信号（即内质网输出基序和高尔基保留信号，分别与COPII和COPI亚基相互作用）；(4)在功能获得分析中，EMP12的高尔基基保留基序在高尔基体中保留了几个后高尔基膜蛋白。这些分选信号在所有植物EMP亚型中高度保守，因此可能代表了植物细胞中EMP靶向的一般机制。
Endomembrane proteins (EMPs), belonging to the evolutionarily conserved transmembrane nine superfamily in yeast and mammalian cells, are characterized by the presence of a large lumenal N terminus, nine transmembrane domains, and a short cytoplasmic tail. The Arabidopsis thaliana genome contains 12 EMP members (EMP1 to EMP12), but little is known about their protein subcellular localization and function. Here, we studied the subcellular localization and targeting mechanism of EMP12 in Arabidopsis and demonstrated that (1) both endogenous EMP12 (detected by EMP12 antibodies) and green fluorescent protein (GFP)-EMP12 fusion localized to the Golgi apparatus in transgenic Arabidopsis plants; (2) GFP fusion at the C terminus of EMP12 caused mislocalization of EMP12-GFP to reach post-Golgi compartments and vacuoles for degradation in Arabidopsis cells; (3) the EMP12 cytoplasmic tail contained dual sorting signals (i.e., an endoplasmic reticulum export motif and a Golgi retention signal that interacted with COPII and COPI subunits, respectively); and (4) the Golgi retention motif of EMP12 retained several post-Golgi membrane proteins within the Golgi apparatus in gain-of-function analysis. These sorting signals are highly conserved in all plant EMP isoforms and, thus, likely represent a general mechanism for EMP targeting in plant cells.