Molecular machinery for non-vesicular trafficking of ceramide

• Published in: Nature 2003-12, Vol.426 (6968), p.803-809
• Main Authors: Hanada, Kentaro, Kumagai, Keigo, Yasuda, Satoshi, Miura, Yukiko, Kawano, Miyuki, Fukasawa, Masayoshi, Nishijima, Masahiro
• Format: Article
• Language: English
• Subjects: Alternative Splicing - genetics; Amino Acid Substitution; Amino acids; Animals; Binding Sites; Biochemistry; Biological and medical sciences; Biological Transport; Cell Line; Cell physiology; Cellular biology; Ceramides - metabolism; Cloning, Molecular; Cricetinae; Disease; Endoplasmic Reticulum - metabolism; Fundamental and applied biological sciences. Psychology; Genetic Complementation Test; Golgi Apparatus - metabolism; Humanities and Social Sciences; Humans; Intracellular Membranes - metabolism; Lipids; Membrane and intracellular transports; Molecular and cellular biology; multidisciplinary; Mutation; Phosphatidylinositol Phosphates - metabolism; Protein Binding; Protein Structure, Tertiary; Protein-Serine-Threonine Kinases - chemistry; Protein-Serine-Threonine Kinases - genetics; Protein-Serine-Threonine Kinases - metabolism; Science; Science (multidisciplinary); Sphingomyelins - biosynthesis
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature02188

Synthesis and sorting of lipids are essential for membrane biogenesis; however, the mechanisms underlying the transport of membrane lipids remain little understood. Ceramide is synthesized at the endoplasmic reticulum and translocated to the Golgi compartment for conversion to sphingomyelin. The main pathway of ceramide transport to the Golgi is genetically impaired in a mammalian mutant cell line, LY-A. Here we identify CERT as the factor defective in LY-A cells. CERT, which is identical to a splicing variant of Goodpasture antigen-binding protein, is a cytoplasmic protein with a phosphatidylinositol-4-monophosphate-binding (PtdIns4P) domain and a putative domain for catalysing lipid transfer. In vitro assays show that this lipid-transfer-catalysing domain specifically extracts ceramide from phospholipid bilayers. CERT expressed in LY-A cells has an amino acid substitution that destroys its PtdIns4P-binding activity, thereby impairing its Golgi-targeting function. We conclude that CERT mediates the intracellular trafficking of ceramide in a non-vesicular manner.