Tissue expression and biological functions of GalCer
GalCer has been originally described in the central nervous system. It is expressed in glial cells (i.e. oligodendrocytes and Schwann cells, respectively in the central and peripheric nervous systems) and it is the major lipid component of myelin, the protective sheath of axons that insulate the axon from electrical activity. This insulation is necessary to increase the rate of transmission of neuronal signals.
GalCer is also one of the major glycosphingolipids expressed by intestinal epithelial cells, which are involved in the terminal hydrolysis and uptake of nutrients.
Lipid rafts have been involved in the regulation of cellular communication pathways (signal transduction). Indeed, stimulation of GalCer at the surface of both neural and intestinal cells results in a rise of intracellular calcium concentration (9).