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  • Title: Effect of adenophostin A on Ca2+ entry and calcium release-activated calcium current (Icrac) in rat basophilic leukemia cells.
    Author: Huang Y, Takahashi M, Tanzawa K, Putney JW.
    Journal: J Biol Chem; 1998 Nov 27; 273(48):31815-21. PubMed ID: 9822648.
    Abstract:
    In most non-excitable cells, calcium influx is signaled by depletion of intracellular calcium stores, a process known as capacitative calcium entry. Adenophostin A, a potent activator of the inositol 1, 4,5-trisphosphate receptor, has been reported to activate Ca2+ entry in Xenopus oocytes to a greater extent than expected on the basis of its ability to release calcium stores. In this study, we compared the abilities of adenophostin A and inositol 2,4,5-trisphosphate ((2, 4,5)IP3) to release Ca2+ from intracellular stores, to activate Ca2+ entry, and to activate calcium release-activated calcium current (Icrac) in rat basophilic leukemia cells. Under conditions of low intracellular Ca2+ buffering (0.1 mM BAPTA), adenophostin A-induced Ca2+ release and activation of Icrac could be monitored simultaneously. However, other reagents that would be expected to deplete Ca2+ stores ((2,4,5)IP3, 3-fluoro-inositol 1,4, 5-trisphosphate, thapsigargin, and ionomycin) were unable to activate Icrac under this low Ca2+ buffering condition. Adenophostin A activated Icrac after a significant delay, longer than the delay for Ca2+ release. Thus, adenophostin A activates Icrac as a consequence of release of intracellular Ca2+, rather than directly acting on store-operated channels. The unique ability of adenophostin A to activate Icrac under conditions of low intracellular Ca2+ buffering suggests an additional site of action, perhaps in preventing or reducing rapid Ca2+-dependent inactivation of store-operated Ca2+ channels.
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