Glu 106in the Orai1 pore contributes to fast Ca 2+ -dependent inactivation and pH dependence of Ca 2+ release-activated Ca 2+ (CRAC) current

Nathan R. Scrimgeour, David P. Wilson, Grigori Y. Rychkov

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27 Citations (Scopus)

Abstract

FCDI (fast Ca 2+ -dependent inactivation) is a mechanism that limits Ca 2+ entry through Ca 2+ channels, including CRAC (Ca 2+release-activated Ca 2+) channels. This phenomenon occurs when the Ca 2+ concentration rises beyond a certain level in the vicinity of the intracellular mouth of the channel pore. In CRAC channels, several regions of the pore-forming protein Orai1, and STIM1 (stromal interaction molecule 1), the sarcoplasmic/endoplasmic reticulum Ca 2+ sensor that communicates the Ca 2+ load of the intracellular stores to Orai1, have been shown to regulate fast Ca 2+ -dependent inactivation. Although significant advances in unravelling the mechanisms of CRAC channel gating have occurred, the mechanisms regulating fast Ca 2+ -dependent inactivation in this channel are not well understood. We have identified that a poremutation, E106D Orai1, changes the kinetics and voltage dependence of the I CRAC (CRAC current), and the selectivity of the Ca 2+ -binding site that regulates fast Ca 2+ - dependent inactivation, whereas the V102I and E190Q mutants when expressed at appropriate ratios with STIM1 have fast Ca 2+ -dependent inactivation similar to that of WT (wild-type) Orai1. Unexpectedly, the E106D mutation also changes the pH dependence of I CRAC. Unlike WTI CRAC, E106D-mediated current is not inhibited at low pH, but instead the block of Na + permeation through the E106D Orai1 pore by Ca 2+ is diminished. These results suggest that Glu 106 inside the CRAC channel pore is involved in co-ordinating the Ca 2+ -binding site that mediates fast Ca 2+ -dependent inactivation.

Original languageEnglish
Pages (from-to)743-753
Number of pages11
JournalBiochemical Journal
Volume441
Issue number2
DOIs
Publication statusPublished - 15 Jan 2012

Keywords

  • Ca release-activated Ca current (I )
  • Calcium
  • Gating
  • Patch clamp
  • pH dependence

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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