Sphingolipids signaling

Igarashi, Y. Functional roles of sphingosine, sphingosine 1-phosphate, and methylsphingosines in regard to membrane sphingolipid signaling pathways (1997) I Biochem. (Tokyo) 122, 1080-7... 

Overlaps between backbone sphingolipid signaling and sphingolipid metabolism. 391... 

Merrill AH, Sweeley CC Sphingolipids metabolism and cell signaling. In Biochemistry of Lipids, Lipoproteins and Membranes. Vance DE, Vance JE (editors). Elsevier, 1996. 

While the fluid mosaic model of membrane stmcture has stood up well to detailed scrutiny, additional features of membrane structure and function are constantly emerging. Two structures of particular current interest, located in surface membranes, are tipid rafts and caveolae. The former are dynamic areas of the exo-plasmic leaflet of the lipid bilayer enriched in cholesterol and sphingolipids they are involved in signal transduction and possibly other processes. Caveolae may derive from lipid rafts. Many if not all of them contain the protein caveolin-1, which may be involved in their formation from rafts. Caveolae are observable by electron microscopy as flask-shaped indentations of the cell membrane. Proteins detected in caveolae include various components of the signal-transduction system (eg, the insutin receptor and some G proteins), the folate receptor, and endothetial nitric oxide synthase (eNOS). Caveolae and lipid rafts are active areas of research, and ideas concerning them and their possible roles in various diseases are rapidly evolving. 

Volume 311. Sphingolipid Metabolism and Cell Signaling (Part A)... 

Veldman, R. J., Maestre, N., Aduib, O. M., Medin, J. A., Salvayre, R., and Levade, T., 2001, A neutral sphingomyelinase resides in sphingolipid-enriched microdomains and is inhibited by the caveolin-scaffolding domain potential implications in tumor necrosis factor signaling. Biochem. J. 355 859-868. 

The white matter is a covering for the nerve fiber known as the myelin sheath. Myelin is a sphingolipid produced by oligodendrocytes (Schwann cells). It acts as a special type of insulation which allows for a much more rapid transmission of the nerve signal. The myelin cover is interrupted periodically. This "bare" area is called a node of Ranvier. It is very important to rapid nerve conduction. See Figure 21. 

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