title: Molecular determinants within N terminus of Orai3 protein that control channel activation and gating.
abstract: STIM1 and Orai represent the key components of Ca(2+) release-activated Ca(2+) channels. Activation of Orai channels requires coupling of the C terminus of STIM1 to the N and C termini of Orai. Although the latter appears to be central in the interaction with STIM1, the role of the N terminus and particularly of the conserved region close to the first transmembrane sequence is less well understood. Here, we investigated in detail the functional role of this conserved region in Orai3 by stepwise deletions. Molecular determinants were mapped for the two modes of Orai3 activation via STIM1 or 2-aminoethoxydiphenyl borate (2-APB) and for current gating characteristics. Increasing N-terminal truncations revealed a progressive decrease of the specific fast inactivation of Orai3 concomitant with diminished binding to calmodulin. STIM1-dependent activation of Orai3 was maintained as long as the second half of this conserved N-terminal domain was present. Further truncations abolished it, whereas Orai3 stimulation via 2-APB was partially retained. In aggregate, the N-terminal conserved region plays a multifaceted role in Orai3 current gating with distinct structural requirements for STIM1- and 2-APB-stimulated activation.
authors: Institute of Biophysics, University of Linz, Altenbergerstrasse 69, 4040 Linz, Austria.
authors: Judith
authors: J
authors: Bergsmann
authors: Isabella
authors: I
authors: Derler
authors: Martin
authors: M
authors: Muik
authors: Irene
authors: I
authors: Frischauf
authors: Marc
authors: M
authors: Fahrner
authors: Philipp
authors: P
authors: Pollheimer
authors: Clemens
authors: C
authors: Schwarzinger
authors: Hermann J
authors: HJ
authors: Gruber
authors: Klaus
authors: K
authors: Groschner
authors: Christoph
authors: C
authors: Romanin
mesh_terms: D015220:Calcium Channels / Q000737:chemistry / Q000378:metabolism*; D017124:Conserved Sequence; D006801:Humans; D015640:Ion Channel Gating; D008565:Membrane Proteins / Q000378:metabolism* / Q000502:physiology; D009363:Neoplasm Proteins / Q000378:metabolism* / Q000502:physiology; D017384:Sequence Deletion; D000071737:Stromal Interaction Molecule 1
chemical_list: D015220:Calcium Channels; D008565:Membrane Proteins; D009363:Neoplasm Proteins; C522867:Orai3 protein, human; C103530:STIM1 protein, human; D000071737:Stromal Interaction Molecule 1