Isoform-specific tethering links the Golgi ribbon to maintain compartmentalization.
Isoform-specific tethering links the Golgi ribbon to maintain compartmentalization.
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DOI：
10.1091/mbc.e13-07-0395
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发表时间：
2014-01
影响因子：
3.3
通讯作者：
Linstedt AD
中科院分区：
文献类型：
--
作者：
Jarvela T;Linstedt AD
使用光灭活，池特异性荧光恢复，和高分辨率显微镜显示，膜系GRASP 65和GRASP 55的早期和晚期高尔基体膜，分别是至关重要的特定的，同型融合的膜上，他们居住。高尔基体重组和堆积蛋白（GRASPs）的同型膜拴系是哺乳动物高尔基体小栈横向连接成带状膜网络所必需的。尽管GRASP 65和GRASP 55分别特异性定位于顺式和中间/反式脑池，但尚不清楚每个GRASP是否介导脑池特异性束缚以及这种特异性是否是高尔基体区室化所必需的。这里，每个GRASP用KillerRed（KR）标记，在HeLa细胞中表达，并通过暴露于光1分钟来抑制。值得注意的是，任一GRASP的失活都使高尔基体带断开，GRASP 65-KR失活的直接影响是顺式而非反式高尔基体完整性的丧失，而GRASP 55-KR的失活首先影响反式而非顺式高尔基体。因此，每个GRASP似乎发挥直接和池特定的作用，连接成一个连续的膜网络的微型堆栈。为了测试失去脑池特异性束缚的后果，我们在所有脑池上产生了具有单个GRASP的高尔基体膜。值得注意的是，膜表现出野生型高尔基带的完整连接性，但在聚糖加工中被分解和缺陷。因此，GRASP同种型特异性地连接类似的脑池以确保高尔基体的区室化和适当的加工。
Use of photoinactivation, cisternae-specific fluorescence recovery, and high-resolution microscopy shows that the membrane tethers GRASP65 and GRASP55 on early and late Golgi membranes, respectively, are critical to the specific, homotypic fusion of the membranes on which they reside. Homotypic membrane tethering by the Golgi reassembly and stacking proteins (GRASPs) is required for the lateral linkage of mammalian Golgi ministacks into a ribbon-like membrane network. Although GRASP65 and GRASP55 are specifically localized to cis and medial/trans cisternae, respectively, it is unknown whether each GRASP mediates cisternae-specific tethering and whether such specificity is necessary for Golgi compartmentalization. Here each GRASP was tagged with KillerRed (KR), expressed in HeLa cells, and inhibited by 1-min exposure to light. Significantly, inactivation of either GRASP unlinked the Golgi ribbon, and the immediate effect of GRASP65-KR inactivation was a loss of cis- rather than trans-Golgi integrity, whereas inactivation of GRASP55-KR first affected the trans- and not the cis-Golgi. Thus each GRASP appears to play a direct and cisternae-specific role in linking ministacks into a continuous membrane network. To test the consequence of loss of cisternae-specific tethering, we generated Golgi membranes with a single GRASP on all cisternae. Remarkably, the membranes exhibited the full connectivity of wild-type Golgi ribbons but were decompartmentalized and defective in glycan processing. Thus the GRASP isoforms specifically link analogous cisternae to ensure Golgi compartmentalization and proper processing.