Stimulation of Ca2+-dependent exocytosis and release of arachidonic acid in cultured mast cells (RBL-2H3) by quercetin

Basic secretagogues, such as compound 48/80, stimulate secretion in rat per itoneal mast cells by directly activating the heterotrimeric G-protein Gi(3 ) (Aridor M, et al. Science 1993,262,1569-72). Cultured RBL-2H3 mast cells do not normally respond to basic secretagogues, but acquire such responsive ness upon prolonged exposure to the kinase inhibitor, quercetin, which also increases the cellular level of Gi(3) (Senyshyn J, Baumgartner RA, Beaven MA. J Immunol 1998;160:5136 44). Expression of a GTPase-deficient mutant of G alpha i(3) in RBL-2H3 cells results in the stimulation of Ca2+-triggered exocytosis and release of arachidonic acid (AA) (Zussman A, Hermuet S, Sag i-Eisenberg R. Eur J Biochem 1998;258:144-6). Here we show that long-term i ncubation with quercetin markedly stimulates Ca2+-triggered exocytosis and release of AA from the RBL-2H3 cells. We further show that membranes derive d from such quercetin-treated cells display a reduced GTPase, but not ATPas e, activity. Taken together with our previous observations, these results f urther implicate Gi(3) as one of the cellular targets through which quercet in confers responsiveness towards the family of basic secretagogues. (C) 20 00 International Society for Immunopharmacology. published by Elsevier Scie nce Ltd. All rights reserved.