title: A coiled-coil clamp controls both conformation and clustering of stromal interaction molecule 1 (STIM1).
abstract: Store-operated Ca(2+) entry, essential for the adaptive immunity, is initiated by the endoplasmic reticulum (ER) Ca(2+) sensor STIM1. Ca(2+) entry occurs through the plasma membrane resident Ca(2+) channel Orai1 that directly interacts with the C-terminal STIM1 domain, named SOAR/CAD. Depletion of the ER Ca(2+) store controls this STIM1/Orai1 interaction via transition to an extended STIM1 C-terminal conformation, exposure of the SOAR/CAD domain, and STIM1/Orai1 co-clustering. Here we developed a novel approach termed FRET-derived Interaction in a Restricted Environment (FIRE) in an attempt to dissect the interplay of coiled-coil (CC) interactions in controlling STIM1 quiescent as well as active conformation and cluster formation. We present evidence of a sequential activation mechanism in the STIM1 cytosolic domains where the interaction between CC1 and CC3 segment regulates both SOAR/CAD exposure and CC3-mediated higher-order oligomerization as well as cluster formation. These dual levels of STIM1 auto-inhibition provide efficient control over the coupling to and activation of Orai1 channels.
authors.affiliation: From the Life Science Center JKU, Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria.
authors.forename: Marc
authors.initials: M
authors.lastname: Fahrner
authors.affiliation: From the Life Science Center JKU, Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Muik
authors.affiliation: From the Life Science Center JKU, Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria.
authors.forename: Rainer
authors.initials: R
authors.lastname: Schindl
authors.affiliation: From the Life Science Center JKU, Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria.
authors.forename: Carmen
authors.initials: C
authors.lastname: Butorac
authors.affiliation: Department of Physiology and Pharmacology, Western University, London, Ontario N6A 5C1, Canada, and.
authors.forename: Peter
authors.initials: P
authors.lastname: Stathopulos
authors.affiliation: Princess Margaret Cancer Centre and Department of Medical Biophysics, University of Toronto, Toronto, Ontario M5G 1L7, Canada.
authors.forename: Le
authors.initials: L
authors.lastname: Zheng
authors.affiliation: From the Life Science Center JKU, Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria.
authors.forename: Isaac
authors.initials: I
authors.lastname: Jardin
authors.affiliation: Princess Margaret Cancer Centre and Department of Medical Biophysics, University of Toronto, Toronto, Ontario M5G 1L7, Canada.
authors.forename: Mitsuhiko
authors.initials: M
authors.lastname: Ikura
authors.affiliation: From the Life Science Center JKU, Institute of Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, 4020 Linz, Austria, christoph.romanin@jku.at.
authors.forename: Christoph
authors.initials: C
authors.lastname: Romanin
mesh_terms: D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D000071740:ORAI1 Protein; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; 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
keywords: Calcium Release-activated Calcium Channel Protein 1 (ORAI1); Fluorescence; Patch Clamp; Signal Transduction; Stromal Interaction Molecule 1 (STIM1)