GalCer

Galactosylceramide (GalCer) is a glycosphingolipid in the cerebroside family, consisting of a β-D-galactose head group linked to a ceramide backbone. It is a neutral glycolipid found in cell membranes, with particular abundance in nervous tissue.

In humans, GalCer is a major constituent of myelin membranes in the central nervous system, produced by oligodendrocytes and, to a lesser extent, Schwann cells. It contributes to the stability and architecture of the myelin sheath and is among the glycosphingolipids enriched in white matter. GalCer serves as a biochemical marker of oligodendroglial membranes and myelin integrity.

Biosynthesis and metabolism: GalCer is synthesized by UDP-galactose ceramide galactosyltransferase (UGT8), which transfers galactose from UDP-galactose to ceramide. It is degraded by galactocerebrosidase (GALC) to galactose and ceramide. Defects in GALC cause Krabbe disease (globoid cell leukodystrophy), a demyelinating disorder characterized by accumulation of galactosylceramide and psychosine and progressive neurodegeneration.

Immunology: The presentation of glycolipids by CD1d to natural killer T cells is best known for the potent α-galactosylceramide (α-GalCer) agonist. GalCer can be recognized by CD1d-restricted T cells in some contexts but is generally far less stimulatory than α-GalCer, reflecting its weaker immunogenic potential.

Clinical and research relevance: GalCer is an important structural lipid in myelin and a substrate in studies of glycosphingolipid metabolism. Abnormal GalCer metabolism is implicated in demyelinating diseases, and GalCer is a common reference point in lipidomics and neuroscience research. See also cerebroside, Krabbe disease, CD1d, iNKT cells.