Fingolimod hydrochloride (
FTY720) is the first in class of
sphingosine 1-phosphate (
S1P) receptor modulator approved to treat
multiple sclerosis via down-regulation of
G protein-coupled
S1P receptor 1 by its phosphorylated form (FTY720-P). Many studies have revealed that
FTY720 exerts various biological effects, including antitumor activities, angiogenesis inhibition, Ca(2+) mobilization and apoptosis, independently of S1P receptors. However, the exact mechanisms underlying their effects or signaling pathways mediated by
FTY720 have not been completely established. To gain further insights into molecular mechanisms of
FTY720 action, the effect of
FTY720 on Ca(2+) signaling in fission yeast was analyzed. The addition of Ca(2+) enhanced the sensitivity induced by
FTY720, and mutants lacking genes required for
calcium homeostasis, including
calcineurin and its downstream
transcription factor, Ppb1-responsive zinc finger
protein (Prz1), were hypersensitive to
FTY720 and CaCl2. The effect of
FTY720 on
calcineurin signaling was monitored by utilizing a
luciferase reporter construct fused to three tandem repeats of the
calcineurin-dependent response element (CDRE), which gives an accurate measure of
calcineurin activity. The addition of
FTY720 increased
calcineurin activity as well as Ca(2+) influx in a concentration-dependent manner. Notably, the FTY720-mediated Ca(2+) influx and
calcineurin activation were reduced markedly by the deletion of yam8 (+) or cch1 (+) encoding putative subunits of a Ca(2+) channel. Consistently, the deletion of Pmk1
mitogen-activated protein kinase (MAPK), which plays an important role in the activation of the Yam8/Cch1 channel, markedly decreased the intracellular Ca(2+) levels upon
FTY720 treatment. These results suggest that the FTY720-stimulated Ca(2+)/
calcineurin signaling activation partly involves the Yam8/Cch1 channel in fission yeast.