Activation Mechanism for CRAC Current and Store-operated Ca²⁺ Entry: CALCIUM INFLUX FACTOR AND Ca²⁺-INDEPENDENT PHOSPHOLIPASE A₂β-MEDIATED PATHWAY

• Published in: The Journal of biological chemistry 2006, Vol.281 (46), p.34926-34935
• Main Authors: Csutora, Peter, Zarayskiy, Vladislav, Peter, Krisztina, Monje, Francisco, Smani, Tarik, Zakharov, Sergey I, Litvinov, Dmitry, Bolotina, Victoria M
• Format: Article
• Language: English
• ISSN: 0021-9258; 1083-351X

Here we tested the role of calcium influx factor (CIF) and calcium-independent phospholipase A₂ (iPLA₂) in activation of Ca²⁺ release-activated Ca²⁺ (CRAC) channels and store-operated Ca²⁺ entry in rat basophilic leukemia (RBL-2H3) cells. We demonstrate that 1) endogenous CIF production may be triggered by Ca²⁺ release (net loss) as well as by simple buffering of free Ca²⁺ within the stores, 2) a specific 82-kDa variant of iPLA₂β and its corresponding activity are present in membrane fraction of RBL cells, 3) exogenous CIF (extracted from other species) mimics the effects of endogenous CIF and activates iPLA₂β when applied to cell homogenates but not intact cells, 4) activation of ICRAC can be triggered in resting RBL cells by dialysis with exogenous CIF, 5) molecular or functional inhibition of iPLA₂β prevents activation of ICRAC, which could be rescued by cell dialysis with a human recombinant iPLA₂β, 6) dependence of ICRAC on intracellular pH strictly follows pH dependence of iPLA₂β activity, and 7) (S)-BEL, a chiral enantiomer of suicidal substrate specific for iPLA₂β, could be effectively used for pharmacological inhibition of ICRAC and store-operated Ca²⁺ entry. These findings validate and significantly advance our understanding of the CIF-iPLA₂-dependent mechanism of activation of ICRAC and store-operated Ca²⁺ entry.