TY - JOUR
T1 - Orai1 and STIM reconstitute store-operated calcium channel function
AU - Soboloff, Jonathan
AU - Spassova, Maria A.
AU - Tang, Xiang D.
AU - Hewavitharana, Thamara
AU - Xu, Wen
AU - Gill, Donald L.
PY - 2006/7/28
Y1 - 2006/7/28
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=33746369780&partnerID=8YFLogxK
U2 - 10.1074/jbc.C600126200
DO - 10.1074/jbc.C600126200
M3 - Article
SN - 0021-9258
VL - 281
SP - 20661
EP - 20665
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 30
ER -