Main content area

Orai-2 is localized on secretory granules and regulates antigen-evoked Ca2+ mobilization and exocytosis in mast cells

Ikeya, Miho, Yamanoue, Kiyoshi, Mochizuki, Yuji, Konishi, Hirofumi, Tadokoro, Satoshi, Tanaka, Masahiko, Suzuki, Ryo, Hirashima, Naohide
Biochemical and biophysical research communications 2014 v.451 pp. 62-67
antigens, calcium, calcium channels, exocytosis, mast cells, secretion, secretory granules
The increase in intracellular Ca2+ through the Ca2+ channel is an indispensable step for the secretion of inflammatory mediators by mast cells. It was recently reported that Orai-1 is responsible for the Ca2+ influx that is activated by depletion of stored Ca2+. There are three isoforms of Orai: Orai-1, Orai-2, and Orai-3; however, isoforms other than Orai-1 are poorly understood. We found that Orai-2 is expressed and localized on secretory granules in RBL-2H3. Ca2+ release from Ca2+ store, induced by antigen stimulation, was significantly attenuated by knockdown of Orai-2, while that induced by thapsigargin was not affected. Furthermore, exocytotic release induced by antigen stimulation was inhibited in knockdown cells. This observation suggests a new role of Orai isoforms in secretory cells.