An inside job: Annexin 1A-Inositol 1,4,5-trisphosphate receptor interaction conveys endoplasmic reticulum luminal Ca(2+) sensitivity

Cytoplasmic Ca(2+) is a pivotal regulator of IP(3)R activity. It is however controversial whether the [Ca(2+)] in the Endoplasmic Reticulum lumen also directly regulates channel function. We highlight a recent paper that demonstrates that luminal [Ca(2+)] potently inhibits IP(3)R activity. This regulation occurs indirectly by an interaction mediated through a binding partner, likely Annexin 1A.