title: Cooperativeness of Orai cytosolic domains tunes subtype-specific gating.
abstract: Activation of immune cells is triggered by the Ca(2+) release-activated Ca(2+) current, which is mediated via channels of the Orai protein family. A key gating process of the three Orai channel isoforms to prevent Ca(2+) overload is fast inactivation, most pronounced in Orai3. A subsequent reactivation is a unique gating characteristic of Orai1 channels, whereas Orai2 and Orai3 currents display a second, slow inactivation phase. Employing a chimeric approach by sequential swapping of respective intra- and extracellular regions between Orai1 and Orai3, we show here that Orai1 specific proline/arginine-rich domains in the N terminus mediate reactivation, whereas the second, intracellular loop modulates fast and slow gating processes. Swapping C-terminal strands lacks a significant impact. However, simultaneous transfer of Orai3 N terminus and its second loop or C terminus in an Orai1 chimera substantially increases fast inactivation centered between wild-type channels. Concomitant swap of all three cytosolic strands from Orai3 onto Orai1 fully conveys Orai3-like gating characteristics, in a strongly cooperative manner. In conclusion, Orai subtype-specific gating requires a cooperative interplay of all three cytosolic domains.
authors.affiliation: From the Institute of Biophysics, University of Linz, Altenbergerstrasse 69, 4040 Linz, Austria and.
authors.forename: Irene
authors.initials: I
authors.lastname: Frischauf
authors.affiliation: From the Institute of Biophysics, University of Linz, Altenbergerstrasse 69, 4040 Linz, Austria and. Electronic address: rainer.schindl@jku.at.
authors.forename: Rainer
authors.initials: R
authors.lastname: Schindl
authors.affiliation: From the Institute of Biophysics, University of Linz, Altenbergerstrasse 69, 4040 Linz, Austria and.
authors.forename: Judith
authors.initials: J
authors.lastname: Bergsmann
authors.affiliation: From the Institute of Biophysics, University of Linz, Altenbergerstrasse 69, 4040 Linz, Austria and.
authors.forename: Isabella
authors.initials: I
authors.lastname: Derler
authors.affiliation: From the Institute of Biophysics, University of Linz, Altenbergerstrasse 69, 4040 Linz, Austria and.
authors.forename: Marc
authors.initials: M
authors.lastname: Fahrner
authors.affiliation: From the Institute of Biophysics, University of Linz, Altenbergerstrasse 69, 4040 Linz, Austria and.
authors.forename: Martin
authors.initials: M
authors.lastname: Muik
authors.affiliation: From the Institute of Biophysics, University of Linz, Altenbergerstrasse 69, 4040 Linz, Austria and.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Fritsch
authors.affiliation: From the Institute of Biophysics, University of Linz, Altenbergerstrasse 69, 4040 Linz, Austria and.
authors.forename: Barbara
authors.initials: B
authors.lastname: Lackner
authors.affiliation: the Department of Pharmaceutical Sciences-Pharmacology and Toxicology, University of Graz, Universitätsplatz 2, 8010 Graz, Austria.
authors.forename: Klaus
authors.initials: K
authors.lastname: Groschner
authors.affiliation: From the Institute of Biophysics, University of Linz, Altenbergerstrasse 69, 4040 Linz, Austria and. Electronic address: 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*; D002460:Cell Line; D003600:Cytosol / Q000378:metabolism; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D015220:Calcium Channels; D011993:Recombinant Fusion Proteins; D002118:Calcium