Norimichi Nakahata, Toshiko Yaginuma and Yasushi Ohizumi
Department of Pharmaceutical Molecular Biology, Graduate School of Pharmaceutical
Sciences, Tohoku University, Aoba, Aramaki, Aoba-ku, Sendai 980 - 8578,
Japan
Abstract: Since maitotoxin, a potent marine toxin, is known to
cause not only Ca2+ influx but also phosphoinositide hydrolysis,
we investigated the Ca2+ dependency of maitotoxin-induced phosphoinositide
hydrolysis in 1321N1 human astrocytoma cells. Maitotoxin elicited inositol
1,4,5-trisphosphate accumulation in a time-dependent manner. In [3H]inositol-labeled
cells, maitotoxin stimulated phosphoinositide hydrolysis in an extracellular
Ca2+-dependent manner. Maitotoxin also caused an intracellular
Ca2+ elevation, which was abolished by an intracellular Ca2+
chelater BAPTA-AM. Interestingly, maitotoxin still caused phosphoinositide
hydrolysis in the BAPTA-AM-treated cells. These results indicate that maitotoxin-induced
phosphoinositide hydrolysis is dependent on extracellular but not intracellular
Ca2+ in 1321N1 human astrocytoma cells.
Keywords: Maitotoxin, Phosphoinositide hydrolysis, Ca2+