Cell Death Lipids - Sphingomyelin and Ceramides
Sphingomyelin is one of the most abundant lipids in the plasma membrane of mammalian cells. In the early stages of apoptosis, Sphingomyelin is converted into ceramide by sphingomyelinase. This is thought to induce local physical changes in the membrane, which then signal subsequent steps of the apoptosis process. Ceramide is also known to be involved in other cell signaling pathways.
Sphingomyelin and ceramide of varying chain length can normally be found in the cell membrane and earlier investigations used egg sphingomyelin which incorporates sphingomyelin of varying chain length. To eliminate the effects of chain length, synthetic sphingomyelin having an amide-linked palmitoyl chain (16 carbon chain) was mixed with varying amounts of n-palmitoyl sphingosine (ceramide with 16 carbon chain).
We studied the effects of changing temperature and concentration and made a sphingomyelin and ceramide partial phase diagram. We found that ceramide increased the gel phase propensity of sphingomyelin-rich membranes.