Traceless synthesis of ceramides in living cells reveals saturation-dependent apoptotic effects

Significance Ceramides are a chemically diverse class of sphingolipids that have critical roles in a wide range of biological pathways. Despite their high biological interest, ceramides have been difficult to study because of their impermeability to the cell membrane. We overcome the principal issues with ceramide delivery by chemoselectively ligating lipid precursors in vivo. Our method employs a proximity-induced ligation which allows for the in situ synthesis of several different natural ceramide species within live cells. Using this approach, we directly confirm the proapoptotic effects of C16:0 ceramide in vivo and observe that ceramide saturation plays a determinant role in ceramide-driven apoptosis.