Competitive modulation of Ca2+ release-activated Ca2+ channel gating by STIM1 and 2-aminoethyldiphenyl borate

Megumi Yamashita, Agila Somasundaram, Murali Prakriya*

*Corresponding author for this work

Research output: Contribution to journalArticle

39 Scopus citations

Abstract

Activation of Ca2+ release-activated Ca2+ channels by depletion of intracellular Ca2+ stores involves physical interactions between the endoplasmic reticulum Ca2+ sensor, STIM1, and the channels composed of Orai subunits. Recent studies indicate that the Orai3 subtype, in addition to being store-operated, is also activated in a store-independent manner by 2-aminoethyldiphenyl borate (2-APB), a small molecule with complex pharmacology. However, it is unknown whether the store-dependent and -independent activation modes of Orai3 channels operate independently or whether there is cross-talk between these activation states. Here we report that in addition to causing direct activation, 2-APB also regulates storeoperated gating of Orai3 channels, causing potentiation at low doses and inhibition at high doses. Inhibition of store-operated gating by 2-APB was accompanied by the suppression of several modes of Orai3 channel regulation that depend on STIM1, suggesting that high doses of 2-APB interrupt STIM1-Orai3 coupling. Conversely, STIM1-bound Orai3 (and Orai1) channels resisted direct gating by high doses of 2-APB. The rate of direct 2-APB activation of Orai3 channels increased linearly with the degree of STIM1-Orai3 uncoupling, suggesting that 2-APB has to first disengage STIM1 before it can directly gate Orai3 channels. Collectively, our results indicate that the store-dependent and -independent modes of Ca2+ release-activated Ca2+ channel activation are mutually exclusive: channels bound to STIM1 resist 2-APB gating, whereas 2-APB antagonizes STIM1 gating.

Original languageEnglish (US)
Pages (from-to)9429-9442
Number of pages14
JournalJournal of Biological Chemistry
Volume286
Issue number11
DOIs
StatePublished - Mar 18 2011

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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