Treatment of HL60 cells (a type of leukemia cell line) by a plant-derived organic compound called phorbol ester increased Sph levels threefold, whereby the cells differentiated into white blood cells called macrophages. Treatment of the same cells by exogenous Sph caused apoptosis. A specific protein kinase phosphorylates 14-3-3, otherwise known as sphingosine-dependent protein kinase 1 (SDK1), only in the presence of Sph.
Treatment of HL60 cells (a type of leukemia cell line) by phorbol ester increased Sph levels threefold, causing the cells to differentiate into macrophages. Conversely, exogenous Sph induced apoptosis in these cells. A specific protein kinase phosphorylates 14-3-3 (SDK1) only when Sph is present.