The effect of rottlerin in calcium regulation in HMC-1(560) cells is mediated by a PKC-delta independent effect

The human mast cell line (HMC-1(560)) is a good model for Ca(2+) signaling studies, because intracellular alkalinization is the mainly histamine release stimulus without changes in the intracellular Ca(2+) levels. This fact allows us to study Ca(2+) changes without degranulation, since this process can affected cellular viability. Ionomycin and thapsigargin have been fully used for induced Ca(2+) influx across SOC channels. When HMC-1(560) cells are incubated with rottlerin, 5 microM, for 5 min a strong inhibition of ionomycin-induced Ca(2+) influx is observed. However, when thapsigargin stimulates Ca(2+) influx, rottlerin did not show any effect on Ca(2+) levels. This fact point two possibilities, ionomycin and thapsigargin might activate different SOC channels or that these drugs might activate the same channel but in a different way in HMC-1(560) cells. The rottlerin inhibition of ionomycin-induced Ca(2+) influx is PKC-delta independent and this effect is not related with the store depletion, since rottlerin has the same effect when it is added before or after the stores are empty. FCCP, a know uncoupler of oxidative phosphorylation in mitochondria, induces the same inhibition in ionomycin Ca(2+) influx than rottlerin which point to the mitochondria as a cellular target to rottlerin.