Hsieh Ting-Sung, Chen Yu-Ju, Chang Chi-Lun, Lee Wan-Ru, Liou Jen
Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390.
Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390
Mol Biol Cell. 2017 Nov 7;28(23):3171-3180. doi: 10.1091/mbc.E17-06-0377. Epub 2017 Sep 27.
Endoplasmic reticulum-plasma membrane (ER-PM) junctions mediate crucial activities ranging from Ca signaling to lipid metabolism. Spatial organization of ER-PM junctions may modulate the extent and location of these cellular activities. However, the morphology and distribution of ER-PM junctions are not well characterized. Using photoactivated localization microscopy, we reveal that the contact area of single ER-PM junctions is mainly oblong with the dimensions of ∼120 nm × ∼80 nm in HeLa cells. Using total internal reflection fluorescence microscopy and structure illumination microscopy, we show that cortical actin contributes to spatial distribution and stability of ER-PM junctions. Further functional assays suggest that intact F-actin architecture is required for phosphatidylinositol 4,5-bisphosphate homeostasis mediated by Nir2 at ER-PM junctions. Together, our study provides quantitative information on spatial organization of ER-PM junctions that is in part regulated by F-actin. We envision that functions of ER-PM junctions can be differentially regulated through dynamic actin remodeling during cellular processes.
内质网 - 质膜（ER-PM）连接介导了从钙信号传导到脂质代谢等一系列关键活动。ER-PM连接的空间组织可能会调节这些细胞活动的程度和位置。然而，ER-PM连接的形态和分布尚未得到充分表征。利用光激活定位显微镜，我们发现HeLa细胞中单个ER-PM连接的接触面积主要呈椭圆形，尺寸约为120纳米×约80纳米。利用全内反射荧光显微镜和结构照明显微镜，我们表明皮质肌动蛋白有助于ER-PM连接的空间分布和稳定性。进一步的功能分析表明，完整的F-肌动蛋白结构对于Nir2在ER-PM连接处介导的磷脂酰肌醇4,5-二磷酸稳态是必需的。总之，我们的研究提供了关于ER-PM连接空间组织的定量信息，其部分受F-肌动蛋白调节。我们设想，在细胞过程中，ER-PM连接的功能可以通过动态肌动蛋白重塑进行差异调节。
