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Pore properties of Orai1 calcium channel dimers and their activation by the STIM1 ER calcium sensor.
J Biol Chem. 2018 08 17; 293(33):12962-12974.JB

Abstract

Store-operated Ca2+ entry signals are mediated by plasma membrane Orai channels activated through intermembrane coupling with Ca2+-sensing STIM proteins in the endoplasmic reticulum (ER). The nature of this elaborate Orai-gating mechanism has remained enigmatic. Based on the Drosophila Orai structure, mammalian Orai1 channels are hexamers comprising three dimeric subunit pairs. We utilized concatenated Orai1 dimers to probe the function of key domains within the channel pore and gating regions. The Orai1-E106Q selectivity-filter mutant, widely considered a dominant pore blocker, was surprisingly nondominant within concatenated heterodimers with Orai1-WT. The Orai1-E106Q/WT heterodimer formed STIM1-activated nonselective cation channels with significantly enlarged apparent pore diameter. Other Glu-106 substitutions entirely blocked the function of heterodimers with Orai1-WT. The hydrophobic pore-lining mutation V102C, which constitutively opens channels, was suppressed by Orai1-WT in the heterodimer. In contrast, the naturally occurring R91W pore-lining mutation associated with human immunodeficiency was completely dominant-negative over Orai-WT in heterodimers. Heterodimers containing the inhibitory K85E mutation extending outward from the pore helix gave an interesting partial effect on both channel activation and STIM1 binding, indicating an important allosteric link between the cytosolic Orai1 domains. The Orai1 C-terminal STIM1-binding domain mutation L273D powerfully blocked STIM1-induced channel activation. The Orai1-L273D/WT heterodimer had drastically impaired STIM1-induced channel gating but, unexpectedly, retained full STIM1 binding. This reveals the critical role of Leu-273 in transducing the STIM1-binding signal into the allosteric conformational change that initiates channel gating. Overall, our results provide important new insights into the role of key functional domains that mediate STIM1-induced gating of the Orai1 channel.

Authors+Show Affiliations

From the Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033 and.From the Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033 and.From the Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033 and.From the Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033 and.From the Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033 and.the Beijing Key Laboratory of Gene Resources and Molecular Development College of Life Sciences, Beijing Normal University, Beijing 100875, China.From the Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033 and.From the Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033 and zhouyd@psu.edu.From the Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033 and 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

29954946

Citation

Cai, Xiangyu, et al. "Pore Properties of Orai1 Calcium Channel Dimers and Their Activation By the STIM1 ER Calcium Sensor." The Journal of Biological Chemistry, vol. 293, no. 33, 2018, pp. 12962-12974.
Cai X, Nwokonko RM, Loktionova NA, et al. Pore properties of Orai1 calcium channel dimers and their activation by the STIM1 ER calcium sensor. J Biol Chem. 2018;293(33):12962-12974.
Cai, X., Nwokonko, R. M., Loktionova, N. A., Abdulqadir, R., Baraniak, J. H., Wang, Y., Trebak, M., Zhou, Y., & Gill, D. L. (2018). Pore properties of Orai1 calcium channel dimers and their activation by the STIM1 ER calcium sensor. The Journal of Biological Chemistry, 293(33), 12962-12974. https://doi.org/10.1074/jbc.RA118.003424
Cai X, et al. Pore Properties of Orai1 Calcium Channel Dimers and Their Activation By the STIM1 ER Calcium Sensor. J Biol Chem. 2018 08 17;293(33):12962-12974. PubMed PMID: 29954946.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Pore properties of Orai1 calcium channel dimers and their activation by the STIM1 ER calcium sensor. AU - Cai,Xiangyu, AU - Nwokonko,Robert M, AU - Loktionova,Natalia A, AU - Abdulqadir,Raz, AU - Baraniak,James H,Jr AU - Wang,Youjun, AU - Trebak,Mohamed, AU - Zhou,Yandong, AU - Gill,Donald L, Y1 - 2018/06/28/ PY - 2018/04/11/received PY - 2018/05/31/revised PY - 2018/6/30/pubmed PY - 2019/2/13/medline PY - 2018/6/30/entrez KW - Orai1 KW - STIM1 KW - calcium KW - calcium channel KW - cell signaling KW - channel gating KW - ion channel KW - selectivity filter KW - store-operated channel SP - 12962 EP - 12974 JF - The Journal of biological chemistry JO - J. Biol. Chem. VL - 293 IS - 33 N2 - Store-operated Ca2+ entry signals are mediated by plasma membrane Orai channels activated through intermembrane coupling with Ca2+-sensing STIM proteins in the endoplasmic reticulum (ER). The nature of this elaborate Orai-gating mechanism has remained enigmatic. Based on the Drosophila Orai structure, mammalian Orai1 channels are hexamers comprising three dimeric subunit pairs. We utilized concatenated Orai1 dimers to probe the function of key domains within the channel pore and gating regions. The Orai1-E106Q selectivity-filter mutant, widely considered a dominant pore blocker, was surprisingly nondominant within concatenated heterodimers with Orai1-WT. The Orai1-E106Q/WT heterodimer formed STIM1-activated nonselective cation channels with significantly enlarged apparent pore diameter. Other Glu-106 substitutions entirely blocked the function of heterodimers with Orai1-WT. The hydrophobic pore-lining mutation V102C, which constitutively opens channels, was suppressed by Orai1-WT in the heterodimer. In contrast, the naturally occurring R91W pore-lining mutation associated with human immunodeficiency was completely dominant-negative over Orai-WT in heterodimers. Heterodimers containing the inhibitory K85E mutation extending outward from the pore helix gave an interesting partial effect on both channel activation and STIM1 binding, indicating an important allosteric link between the cytosolic Orai1 domains. The Orai1 C-terminal STIM1-binding domain mutation L273D powerfully blocked STIM1-induced channel activation. The Orai1-L273D/WT heterodimer had drastically impaired STIM1-induced channel gating but, unexpectedly, retained full STIM1 binding. This reveals the critical role of Leu-273 in transducing the STIM1-binding signal into the allosteric conformational change that initiates channel gating. Overall, our results provide important new insights into the role of key functional domains that mediate STIM1-induced gating of the Orai1 channel. SN - 1083-351X UR - https://www.unboundmedicine.com/medline/citation/29954946/Pore_properties_of_Orai1_calcium_channel_dimers_and_their_activation_by_the_STIM1_ER_calcium_sensor_ L2 - http://www.jbc.org/cgi/pmidlookup?view=long&pmid=29954946 DB - PRIME DP - Unbound Medicine ER -