title: Facilitation of Orai3 targeting and store-operated function by Orai1.
abstract: Orai1 subunits interacting with STIM1 molecules comprise the major components responsible for calcium release-activated calcium (CRAC) channels. The homologs Orai2 and Orai3 yield smaller store-operated currents when overexpressed and are mostly unable to substitute Orai1. Orai3 subunits are also essential components of store independent channel complexes and also tune inhibition of ICRAC by reactive oxygen species. Here we use patch-clamp, microscopy, Ca(2+)-imaging and biochemical experiments to investigate the interdependence of Orai2, Orai3 and Orai1. We demonstrate that store-operation and localization of Orai3 but not of Orai2 to STIM1 clusters in HEK cells or to the immunological synapse in T cells is facilitated by Orai1 while Orai3's store-independent activity remains unaffected. On the other hand, one Orai3 subunit confers redox-resistance to heteromeric channels. The inefficient store operation of Orai3 is partly due to the lack of three critical C-terminal residues, the insertion of which improves interaction with STIM1 and abrogates Orai3's dependence on Orai1. Our results suggest that Orai3 down-tunes efficient STIM1 gating when in a heteromeric complex with Orai1.
authors: Molecular Biophysics, School of Medicine, Saarland University, 66421 Homburg, Germany.
authors: Dalia
authors: D
authors: Alansary
authors: Biophysics, Center for Integrated Physiology and Molecular Medicine (CIPMM), School of Medicine, Saarland University, 66421 Homburg, Germany.
authors: Ivan
authors: I
authors: Bogeski
authors: Molecular Biophysics, School of Medicine, Saarland University, 66421 Homburg, Germany. Electronic address: barbara.niemeyer@uks.eu.
authors: Barbara A
authors: BA
authors: Niemeyer
mesh_terms: D000595:Amino Acid Sequence; D015220:Calcium Channels / Q000737:chemistry / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D054992:Immunological Synapses; D015640:Ion Channel Gating; D019169:Jurkat Cells; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins; D000071740:ORAI1 Protein; D000071741:ORAI2 Protein; D010084:Oxidation-Reduction; D055503:Protein Multimerization; D021122:Protein Subunits / Q000378:metabolism; D021381:Protein Transport; D000071737:Stromal Interaction Molecule 1; D013601:T-Lymphocytes / Q000378:metabolism
chemical_list: D015220:Calcium Channels; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D000071740:ORAI1 Protein; C510746:ORAI1 protein, human; D000071741:ORAI2 Protein; C514506:ORAI2 protein, human; C522867:Orai3 protein, human; D021122:Protein Subunits; C103530:STIM1 protein, human; D000071737:Stromal Interaction Molecule 1
keywords: CRAC; Clustering; Concatenated channel; Immunological synapse; STIM1; Stoichiometry