STIM1 triggers a gating rearrangement at the extracellular mouth of the ORAI1 channel.
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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.
author list (cited authors)
Gudlur, A., Quintana, A., Zhou, Y., Hirve, N., Mahapatra, S., & Hogan, P. G.
complete list of authors
Gudlur, Aparna||Quintana, Ariel||Zhou, Yubin||Hirve, Nupura||Mahapatra, Sahasransu||Hogan, Patrick G