Figure 2. . Activation of release-activated Ca²⁺ channel.

The increase of IP₃ concentration induced by activation of PLC activates endoplasmic reticulum (ER)-resident IP₃ receptors (IP₃R) and causes the release of Ca²⁺ from ER, which leads to oligomerization and conformational switch of STIM1. The activated STIM1 oligomers then move toward the ER–plasma membrane junctions and trigger Ca²⁺ influx through direct interaction with an opening of ORAI1 Ca²⁺ channels in the plasma membrane.

CRAC: Release-activated Ca²⁺; PLC: Phospholipase C.