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Cross-linking of Orai1 channels by STIM proteins.
Proc Natl Acad Sci U S A. 2018 04 10; 115(15):E3398-E3407.PN

Abstract

The transmembrane docking of endoplasmic reticulum (ER) Ca2+-sensing STIM proteins with plasma membrane (PM) Orai Ca2+ channels is a critical but poorly understood step in Ca2+ signal generation. STIM1 protein dimers unfold to expose a discrete STIM-Orai activating region (SOAR1) that tethers and activates Orai1 channels within discrete ER-PM junctions. We reveal that each monomer within the SOAR dimer interacts independently with single Orai1 subunits to mediate cross-linking between Orai1 channels. Superresolution imaging and mobility measured by fluorescence recovery after photobleaching reveal that SOAR dimer cross-linking leads to substantial Orai1 channel clustering, resulting in increased efficacy and cooperativity of Orai1 channel function. A concatenated SOAR1 heterodimer containing one monomer point mutated at its critical Orai1 binding residue (F394H), although fully activating Orai channels, is completely defective in cross-linking Orai1 channels. Importantly, the naturally occurring STIM2 variant, STIM2.1, has an eight-amino acid insert in its SOAR unit that renders it functionally identical to the F394H mutant in SOAR1. Contrary to earlier predictions, the SOAR1-SOAR2.1 heterodimer fully activates Orai1 channels but prevents cross-linking and clustering of channels. Interestingly, combined expression of full-length STIM1 with STIM2.1 in a 5:1 ratio causes suppression of sustained agonist-induced Ca2+ oscillations and protects cells from Ca2+ overload, resulting from high agonist-induced Ca2+ release. Thus, STIM2.1 exerts a powerful regulatory effect on signal generation likely through preventing Orai1 channel cross-linking. Overall, STIM-mediated cross-linking of Orai1 channels is a hitherto unrecognized functional paradigm that likely provides an organizational microenvironment within ER-PM junctions with important functional impact on Ca2+ signal generation.

Authors+Show Affiliations

Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, PA 17033; zhouyd@psu.edu dongill@psu.edu.Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, PA 17033.Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, PA 17033.Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, PA 17033.Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, PA 17033.Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, PA 17033.Department of Molecular Biophysics, Center for Integrative Physiology and Molecular Medicine, Saarland University, Homburg 66421, Germany.Beijing Key Laboratory of Gene Resources and Molecular Development, College of Life Sciences, Beijing Normal University, 100875 Beijing, People's Republic of China.Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, PA 17033.Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, PA 17033; zhouyd@psu.edu dongill@psu.edu.

Pub Type(s)

Journal Article
Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

29581306

Citation

Zhou, Yandong, et al. "Cross-linking of Orai1 Channels By STIM Proteins." Proceedings of the National Academy of Sciences of the United States of America, vol. 115, no. 15, 2018, pp. E3398-E3407.
Zhou Y, Nwokonko RM, Cai X, et al. Cross-linking of Orai1 channels by STIM proteins. Proc Natl Acad Sci USA. 2018;115(15):E3398-E3407.
Zhou, Y., Nwokonko, R. M., Cai, X., Loktionova, N. A., Abdulqadir, R., Xin, P., Niemeyer, B. A., Wang, Y., Trebak, M., & Gill, D. L. (2018). Cross-linking of Orai1 channels by STIM proteins. Proceedings of the National Academy of Sciences of the United States of America, 115(15), E3398-E3407. https://doi.org/10.1073/pnas.1720810115
Zhou Y, et al. Cross-linking of Orai1 Channels By STIM Proteins. Proc Natl Acad Sci USA. 2018 04 10;115(15):E3398-E3407. PubMed PMID: 29581306.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Cross-linking of Orai1 channels by STIM proteins. AU - Zhou,Yandong, AU - Nwokonko,Robert M, AU - Cai,Xiangyu, AU - Loktionova,Natalia A, AU - Abdulqadir,Raz, AU - Xin,Ping, AU - Niemeyer,Barbara A, AU - Wang,Youjun, AU - Trebak,Mohamed, AU - Gill,Donald L, Y1 - 2018/03/26/ PY - 2018/3/28/pubmed PY - 2018/11/6/medline PY - 2018/3/28/entrez KW - Orai channels KW - STIM1 protein KW - STIM2.1 protein KW - calcium oscillation KW - calcium signals SP - E3398 EP - E3407 JF - Proceedings of the National Academy of Sciences of the United States of America JO - Proc. Natl. Acad. Sci. U.S.A. VL - 115 IS - 15 N2 - The transmembrane docking of endoplasmic reticulum (ER) Ca2+-sensing STIM proteins with plasma membrane (PM) Orai Ca2+ channels is a critical but poorly understood step in Ca2+ signal generation. STIM1 protein dimers unfold to expose a discrete STIM-Orai activating region (SOAR1) that tethers and activates Orai1 channels within discrete ER-PM junctions. We reveal that each monomer within the SOAR dimer interacts independently with single Orai1 subunits to mediate cross-linking between Orai1 channels. Superresolution imaging and mobility measured by fluorescence recovery after photobleaching reveal that SOAR dimer cross-linking leads to substantial Orai1 channel clustering, resulting in increased efficacy and cooperativity of Orai1 channel function. A concatenated SOAR1 heterodimer containing one monomer point mutated at its critical Orai1 binding residue (F394H), although fully activating Orai channels, is completely defective in cross-linking Orai1 channels. Importantly, the naturally occurring STIM2 variant, STIM2.1, has an eight-amino acid insert in its SOAR unit that renders it functionally identical to the F394H mutant in SOAR1. Contrary to earlier predictions, the SOAR1-SOAR2.1 heterodimer fully activates Orai1 channels but prevents cross-linking and clustering of channels. Interestingly, combined expression of full-length STIM1 with STIM2.1 in a 5:1 ratio causes suppression of sustained agonist-induced Ca2+ oscillations and protects cells from Ca2+ overload, resulting from high agonist-induced Ca2+ release. Thus, STIM2.1 exerts a powerful regulatory effect on signal generation likely through preventing Orai1 channel cross-linking. Overall, STIM-mediated cross-linking of Orai1 channels is a hitherto unrecognized functional paradigm that likely provides an organizational microenvironment within ER-PM junctions with important functional impact on Ca2+ signal generation. SN - 1091-6490 UR - https://www.unboundmedicine.com/medline/citation/29581306/Cross_linking_of_Orai1_channels_by_STIM_proteins_ L2 - http://www.pnas.org/cgi/pmidlookup?view=long&pmid=29581306 DB - PRIME DP - Unbound Medicine ER -