Fosfosphingolipidi

Fosfosphingolipidi, also known as phosphosphingolipids, are a subclass of sphingolipids in which the ceramide backbone bears a phosphate-containing head group. The best-characterized members are sphingomyelins, ceramide-1-phosphate, and ceramide phosphoethanolamine. Sphingomyelin features a phosphocholine head group attached by a phosphodiester linkage to ceramide and is a major component of animal cell membranes, particularly in the myelin sheath. Ceramide-1-phosphate is formed by phosphorylation of ceramide and acts as a bioactive lipid involved in inflammation, cell proliferation, and survival. Ceramide phosphoethanolamine is another phosphate-containing ceramide derivative found in certain tissues and organisms; it is less abundant in humans.

Biosynthesis and metabolism: Sphingomyelin is synthesized in the Golgi by sphingomyelin synthase through transfer of the head group from phosphatidylcholine to ceramide, producing diacylglycerol as a byproduct. Ceramide-1-phosphate is produced by ceramide kinase adding a phosphate to ceramide; it can be dephosphorylated by lipid phosphatases. Sphingomyelin is cleaved by sphingomyelinases to yield ceramide and phosphocholine. These lipids participate in membrane organization, particularly lipid rafts, and in signaling pathways that regulate inflammation, apoptosis, and stress responses. The balance among sphingomyelin, ceramide, ceramide-1-phosphate, and other sphingolipid metabolites forms part of the broader sphingolipid rheostat that influences cell fate.

Clinical and research relevance: Abnormalities in sphingolipid metabolism, including phosphosphingolipids, are linked to neurodegenerative diseases, cancer, and metabolic disorders. Sphingomyelin and its metabolites are studied as biomarkers and potential therapeutic targets. Analytical methods such as mass spectrometry enable detailed profiling of phosphosphingolipids in biological samples.