title: STIM1/Orai1 coiled-coil interplay in the regulation of store-operated calcium entry.
abstract: Orai1 calcium channels in the plasma membrane are activated by stromal interaction molecule-1 (STIM1), an endoplasmic reticulum calcium sensor, to mediate store-operated calcium entry (SOCE). The cytosolic region of STIM1 contains a long putative coiled-coil (CC)1 segment and shorter CC2 and CC3 domains. Here we present solution nuclear magnetic resonance structures of a trypsin-resistant CC1-CC2 fragment in the apo and Orai1-bound states. Each CC1-CC2 subunit forms a U-shaped structure that homodimerizes through antiparallel interactions between equivalent α-helices. The CC2:CC2' helix pair clamps two identical acidic Orai1 C-terminal helices at opposite ends of a hydrophobic/basic STIM-Orai association pocket. STIM1 mutants disrupting CC1:CC1' interactions attenuate, while variants promoting CC1 stability spontaneously activate Orai1 currents. CC2 mutations cause remarkable variability in Orai1 activation because of a dual function in binding Orai1 and autoinhibiting STIM1 oligomerization via interactions with CC3. We conclude that SOCE is activated through dynamic interplay between STIM1 and Orai1 helices.
authors.affiliation: University Health Network and Department of Medical Biophysics, Campbell Family Cancer Research Institute, Ontario Cancer Institute, University of Toronto, Room 4-804, MaRS TMDT, 101 College Street, Toronto, Ontario, Canada M5G 1L7.
authors.forename: Peter B
authors.initials: PB
authors.lastname: Stathopulos
authors.affiliation: Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria.
authors.forename: Rainer
authors.initials: R
authors.lastname: Schindl
authors.affiliation: Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria.
authors.forename: Marc
authors.initials: M
authors.lastname: Fahrner
authors.affiliation: University Health Network and Department of Medical Biophysics, Campbell Family Cancer Research Institute, Ontario Cancer Institute, University of Toronto, Room 4-804, MaRS TMDT, 101 College Street, Toronto, Ontario, Canada M5G 1L7.
authors.forename: Le
authors.initials: L
authors.lastname: Zheng
authors.affiliation: University Health Network and Department of Medical Biophysics, Campbell Family Cancer Research Institute, Ontario Cancer Institute, University of Toronto, Room 4-804, MaRS TMDT, 101 College Street, Toronto, Ontario, Canada M5G 1L7.
authors.forename: Geneviève M
authors.initials: GM
authors.lastname: Gasmi-Seabrook
authors.affiliation: Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Muik
authors.affiliation: Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria.
authors.forename: Christoph
authors.initials: C
authors.lastname: Romanin
authors.affiliation: University Health Network and Department of Medical Biophysics, Campbell Family Cancer Research Institute, Ontario Cancer Institute, University of Toronto, Room 4-804, MaRS TMDT, 101 College Street, Toronto, Ontario, Canada M5G 1L7.
authors.forename: Mitsuhiko
authors.initials: M
authors.lastname: Ikura
mesh_terms: D000595:Amino Acid Sequence; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D019281:Dimerization; D004721:Endoplasmic Reticulum / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008565:Membrane Proteins / Q000378:metabolism*; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009154:Mutation; D009363:Neoplasm Proteins / Q000378:metabolism*; D000071740:ORAI1 Protein; D018408:Patch-Clamp Techniques; D000071737:Stromal Interaction Molecule 1
chemical_list: D015220:Calcium Channels; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D000071740:ORAI1 Protein; C510746:ORAI1 protein, human; C103530:STIM1 protein, human; D000071737:Stromal Interaction Molecule 1; D002118:Calcium