Use of fumonisin B1 to test the intercellular transfer of sphingosine.

Sphingosine, a core unit of sphingolipids, has been shown to mediate intracellular signaling events. It is conceivable that sphingosine could act as an intracellular messenger as well as an intracellular modulator, if sphingosine were to be transferred intercellularly. Murine interleukin-2 (IL-2) dependent T-lymphocyte CTLL cells, murine fibroblasts Swiss 3R3 cells, and murine fibroblast BALB/C A31 cells metabolize exogenously added sphingosine to ceramide. Fumonisin B2, a mycotoxin produced by Fusarium moniliforme, blocks the conversion of sphingosine to ceramide. In the study described here, CTLL cells exhibiting the conversion of sphingosine to ceramide were used as recipient cells, whereas fumonisin B1-treated cells (A31 cells, Swiss 3T3 cells and CTLL cells), in which the conversion was blocked were used as donor cells. To demonstrate intercellular transfer of sphingosine through the conversion pathway of sphingosine to ceramide, fumonisin B1-treated donor cells incorporating radioactive sphingosine were co-incubated with CTLL cells and the ceramide response was examined. These experiments demonstrated that it is possible to prove the intercellular transfer of sphingosine by using different activities in the cellular conversion pathway of sphingosine to ceramide.