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Supra-Molecular Assemblies of ORAI1 at Rest Precede Local Accumulation into Puncta after Activation

  • The Ca2+ selective channel ORAI1 and endoplasmic reticulum (ER)-resident STIM proteins form the core of the channel complex mediating store operated Ca2+ 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.

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Document Type:Article
Author:Diana B. PeckysORCiD, Daniel Gaa, Dalia AlansaryORCiD, Barbara A. NiemeyerORCiD, Niels de JongeORCiD
Parent Title (English):International journal of molecular sciences
First Page:799
Year of first Publication:2021
Release Date:2022/08/09
Tag:calcium channel; liquid phase electron microscopy; membrane protein; protein clusters; single molecule
Impact:06.208 (2021)
Funding Information:Deutsche Forschungsgemeinschaft (SFB1027 (project C7))
Scientific Units:Innovative Electron Microscopy
DDC classes:500 Naturwissenschaften und Mathematik / 530 Physik
Open Access:Open Access
Signature:INM 2021/014
Licence (German):License LogoCreative Commons - CC BY - Namensnennung 4.0 International