title: STIM1 triggers a gating rearrangement at the extracellular mouth of the ORAI1 channel.
abstract: The ER-resident regulatory protein STIM1 triggers store-operated Ca(2+) entry by direct interaction with the plasma membrane Ca(2+) channel ORAI1. The mechanism of channel gating remains undefined. Here we establish that STIM1 gates the purified recombinant ORAI1 channel in vitro, and use Tb(3+) luminescence and, separately, disulfide crosslinking to probe movements of the pore-lining helices. We show that interaction of STIM1 with the cytoplasmic face of the human ORAI1 channel elicits a conformational change near the external entrance to the pore, detectable at the pore Ca(2+)-binding residue E106 and the adjacent pore-lining residue V102. We demonstrate that a short nonpolar segment of the pore including V102 forms a barrier to ion flux in the closed channel, implicating the STIM1-dependent movement in channel gating. Our data explain the close coupling between ORAI1 channel gating and ion selectivity, and open a new avenue to dissect the gating, modulation and inactivation of ORAI-family channels.
authors.affiliation: Division of Signalling and Gene Expression, La Jolla Institute for Allergy and Immunology, La Jolla, California 92037, USA.
authors.forename: Aparna
authors.initials: A
authors.lastname: Gudlur
authors.affiliation: Division of Signalling and Gene Expression, La Jolla Institute for Allergy and Immunology, La Jolla, California 92037, USA.
authors.forename: Ariel
authors.initials: A
authors.lastname: Quintana
authors.affiliation: Division of Signalling and Gene Expression, La Jolla Institute for Allergy and Immunology, La Jolla, California 92037, USA.
authors.forename: Yubin
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Division of Signalling and Gene Expression, La Jolla Institute for Allergy and Immunology, La Jolla, California 92037, USA.
authors.forename: Nupura
authors.initials: N
authors.lastname: Hirve
authors.affiliation: Division of Signalling and Gene Expression, La Jolla Institute for Allergy and Immunology, La Jolla, California 92037, USA.
authors.forename: Sahasransu
authors.initials: S
authors.lastname: Mahapatra
authors.affiliation: Division of Signalling and Gene Expression, La Jolla Institute for Allergy and Immunology, La Jolla, California 92037, USA.
authors.forename: Patrick G
authors.initials: PG
authors.lastname: Hogan
mesh_terms: D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology*; D008565:Membrane Proteins / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000378:metabolism*; D000071740:ORAI1 Protein; D017433:Protein Structure, Secondary; 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