Figure 4.

Store-operated Ca²⁺ entry (SOCE). Ligand binding to certain G protein coupled receptors leads to activation of phospholipase Cβ. The IP3 thus released increases Ca²⁺ release from the lumen of the endoplasmic reticulum. Depletion of ER calcium leads to a Stim1 (Ca²⁺ sensor)—Orai (Ca²⁺ channel) interaction and the entry of extracellular Ca²⁺. ZnO nanoparticles inhibit this pathway by blocking the SOCE without affecting proximal receptor signaling events [67].