Ceramide inhibits IgE-mediated activation of phospholipase D, but not of phospholipase C, in rat basophilic leukemia (RBL-2H3) cells.

摘要: Ceramide, a product of sphingomyelin hydrolysis by sphingomyelinase, elicits various cellular functions and has recently been regarded as second messenger. To investigate the role ceramide in rat basophilic leukemia (RBL-2H3) cells, effects cell-permeable analogue, N-acetylsphingosine (C2-ceramide), on Ag-mediated responses were examined. C2-Ceramide inhibited Ag- or PMA-induced activation phospholipase D (PLD), whereas Ca2+ ionophore A23187-induced PLD was not affected. failed to inhibit activity two different vitro assay systems. Since is known be regulated several factors, C2-ceramide these factors We have previously reported possible involvement protein tyrosine kinase activation. However, had no effect Ag-induced phosphorylation, including mitogen-activated (MAP) kinases. In fura-2-loaded RBL-2H3 suppressed influx, leaving initial increase inositol phosphate production unaffected. Western blot analysis revealed that Ag caused translocation C (PKC) alpha, beta 1, 2, delta epsilon isozymes from cytosol membrane fraction. Translocation 2 specifically prevented C2-ceramide. Moreover, serotonin release. absence extracellular Ca2+, release reaction greatly reduced. The inhibitory profile nearly same obtained C2-ceramide-treated cells. These results suggest inhibits release, probably through blockage influx Ca(2+)-dependent PKC