Synaptotagmin-Associated Endoplasmic Reticulum-Plasma Membrane Contact Sites Are Localized to Immobile ER Tubules
Synaptotagmin-Associated Endoplasmic Reticulum-Plasma Membrane Contact Sites Are Localized to Immobile ER Tubules
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DOI：
10.1104/pp.18.00498
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发表时间：
2018-10-01
期刊：
影响因子：
7.4
通讯作者：
Shimada, Tomoo
中科院分区：
文献类型：
--
作者：
Ishikawa, Kazuya;Tamura, Kentaro;Shimada, Tomoo
植物内质网（ER）在形态上分为小管和片层，整体上似乎是连续流动的，但局部存在移动的区和不移动的区。在真核生物中，ER在称为ER-PM接触位点（EPCSs）的结构域与质膜（PM）发生物理和功能性相互作用。扩展的突触结合蛋白家族蛋白集中在皮质ER中形成一种类型的EPCS;然而，目前还不清楚扩展的突触结合蛋白的定位是否对应于EPCS以及在皮质ER中形成EPCS的位置。在这里，我们分析了时空定位的突触结合蛋白1（SYT 1），突触结合蛋白在拟南芥（拟南芥），调查的精确分布SYT 1相关的EPCSs在皮层ER。使用超分辨率共聚焦实时成像显微镜的三维成像表明，SYT 1特异性定位于ER-PM边界。延时成像显示SYT 1分布于非移动的内质网小管，但不分布于移动的小管。此外，SYT 1经常定位于ER片的边缘，这些ER片随着时间的推移转化为不动的ER小管。较低的细胞内钙离子浓度导致EPCS面积增加，并破坏ER网络。最后，SYT 1缺陷导致不动小管减少和ER网孔扩大。总之，我们的研究结果表明，SYT 1相关的EPCS分布到不动的小管，并在管状ER网络的形成中发挥重要作用。这提供了重要的洞察皮质ER的功能和动力学/形态之间的关系。
The plant endoplasmic reticulum (ER), which is morphologically divided into tubules and sheets, seems to flow continuously as a whole, but locally, mobile and immobile regions exist. In eukaryotes, the ER physically and functionally interacts with the plasma membrane (PM) at domains called ER-PM contact sites (EPCSs). Extended synaptotagmin family proteins are concentrated in the cortical ER to form one type of EPCS; however, it is unclear whether the localization of extended synaptotagmin corresponds to the EPCS and where in the cortical ER the EPCSs are formed. Here, we analyzed the spatiotemporal localization of SYNAPTOTAGMIN1 (SYT1), a synaptotagmin in Arabidopsis (Arabidopsis thaliana), to investigate the precise distribution of SYT1-associated EPCSs in the cortical ER. Three-dimensional imaging using superresolution confocal live imaging microscopy demonstrated that SYT1 was specifically localized to the ER-PM boundary. Time-lapse imaging revealed that SYT1 was distributed to immobile ER tubules, but not to mobile tubules. Moreover, SYT1 was frequently localized to the edges of ER sheets that were transformed into immobile ER tubules over time. A lower intracellular calcium ion concentration resulted in an increased EPCS area and disrupted the ER network. Finally, SYT1 deficiency caused a reduction of the immobile tubules and enlargement of the ER meshes. Taken together, our findings show that SYT1-associated EPCS are distributed to immobile tubules and play an important role in the formation of the tubular ER network. This provides important insight into the relationship between the function and dynamics/morphology of the cortical ER.