Lysenin: a sphingomyelin specific pore-forming toxin.

Sphingomyelin is a major sphingolipid in mammalian cells. Recent results indicate that sphingomyelin is a reservoir of lipid second messengers, ceramide and sphingosine-1-phosphate. Sphingomyelin is also a major component of sphingolipid and cholesterol-rich membrane domains (lipid rafts). Lysenin is a pore-forming toxin that specifically binds sphingomyelin. The binding of lysenin to sphingomyelin is dependent on the membrane distribution of the lipid, i.e. the toxin selectively binds sphingomyelin clusters. Development of a non-toxic lysenin mutant revealed the spatial and functional heterogeneity of sphingolipid-rich membrane domains.