Molecular Biophysics, Center for Integrative Physiology and Molecular Medicine, Saarland University, 66421 Homburg, Germany.
INM-Leibniz Institute for New Materials, 66123 Saarbrücken, Germany.
Int J Mol Sci. 2021 Jan 14;22(2):799. doi: 10.3390/ijms22020799.
The Ca selective channel ORAI1 and endoplasmic reticulum (ER)-resident STIM proteins form the core of the channel complex mediating store operated Ca entry (SOCE). Using liquid phase electron microscopy (LPEM), the distribution of ORAI1 proteins was examined at rest and after SOCE-activation at nanoscale resolution. The analysis of over seven hundred thousand ORAI1 positions revealed a number of ORAI1 channels had formed STIM-independent distinct supra-molecular clusters. Upon SOCE activation and in the presence of STIM proteins, a fraction of ORAI1 assembled in micron-sized two-dimensional structures, such as the known puncta at the ER plasma membrane contact zones, but also in divergent structures such as strands, and ring-like shapes. Our results thus question the hypothesis that stochastically migrating single ORAI1 channels are trapped at regions containing activated STIM, and we propose instead that supra-molecular ORAI1 clusters fulfill an amplifying function for creating dense ORAI1 accumulations upon SOCE-activation.
钙选择性通道 ORAI1 和内质网 (ER) 驻留的 STIM 蛋白构成了介导钙库操作钙内流 (SOCE) 的通道复合物的核心。利用液相电子显微镜 (LPEM)，以纳米级分辨率检查了 SOCE 激活前后 ORAI1 蛋白的分布。对超过 70 万个 ORAI1 位置的分析表明，一些 ORAI1 通道已经形成了 STIM 独立的独特超分子簇。在 SOCE 激活和 STIM 蛋白存在的情况下，一部分 ORAI1 组装成微米大小的二维结构，例如 ER 质膜接触区的已知斑点，但也组装成发散结构，如链状和环状形状。因此，我们的研究结果对随机迁移的单个 ORAI1 通道被捕获在含有激活的 STIM 的区域的假说提出了质疑，我们提出超分子 ORAI1 簇在 SOCE 激活时发挥放大功能，以形成密集的 ORAI1 聚集。
