Orai1 and STIM reconstitute store-operated calcium channel function

Jonathan Soboloff, Maria A. Spassova, Xiang D. Tang, Thamara Hewavitharana, Wen Xu, Donald L. Gill

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Abstract

The two membrane proteins, STIM1 and Orai1, have each been shown to be essential for the activation of store-operated channels (SOC). Yet, how these proteins functionally interact is not known. Here, we reveal that STIM1 and Orai1 expressed together reconstitute functional SOCs. Expressed alone, Orai1 strongly reduces store-operated Ca2+ entry (SOCE) in human embryonic kidney 293 cells and the Ca2+ release-activated Ca2+ current (ICRAC) in rat basophilic leukemia cells. However, expressed along with the store-sensing STIM1 protein, Orai1 causes a massive increase in SOCE, enhancing the rate of Ca2+ entry by up to 103-fold. This entry is entirely store-dependent since the same coexpression causes no measurable store-independent Ca2+ entry. The entry is completely blocked by the SOC blocker, 2-aminoethoxydiphenylborate. Orai1 and STIM1 coexpression also caused a large gain in CRAC channel function in rat basophilic leukemia cells. The close STIM1 homologue, STIM2, inhibited SOCE when expressed alone but coexpressed with Orai1 caused substantial constitutive (store-independent) Ca2+ entry. STIM proteins are known to mediate Ca2+ store-sensing and endoplasmic reticulum-plasma membrane coupling with no intrinsic channel properties. Our results revealing a powerful gain in SOC function dependent on the presence of both Orai1 and STIM1 strongly suggest that Orai1 contributes the PM channel component responsible for Ca2+ entry. The suppression of SOC function by Orai1 overexpression likely reflects a required stoichiometry between STIM1 and Orai1.

Original languageEnglish (US)
Pages (from-to)20661-20665
Number of pages5
JournalJournal of Biological Chemistry
Volume281
Issue number30
DOIs
StatePublished - Jul 28 2006

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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    Soboloff, J., Spassova, M. A., Tang, X. D., Hewavitharana, T., Xu, W., & Gill, D. L. (2006). Orai1 and STIM reconstitute store-operated calcium channel function. Journal of Biological Chemistry, 281(30), 20661-20665. https://doi.org/10.1074/jbc.C600126200