[The biological role of sulfatides].
Sulfatides (3-O-sulfogalactosylceramides, sulfated galactocerebrosides, SM4) are esters of sulfuric acid with galactosylceramides. These acidic glycosphingolipids, present at the external leaflet of the plasma membrane, are synthesized by a variety of mammalian cells. They are especially abundant in the myelin sheath of oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system. Studies using cerebroside galactosyltransferase-deficient mice revealed that sulfatides are responsible for proper structure and functioning of myelin. Large amounts of sulfatides are also found in the kidney, gastrointestinal tract, islets of Langerhans, and membranes of erythrocytes, thrombocytes and granulocytes. They are ligands for numerous proteins, but in most cases the biological role of such interactions is poorly understood. A notable exception is their binding by P- and L-selectins. Platelet sulfatides are major ligands for P-selectin, and this interaction is critical for the formation of stable platelet aggregates. Sulfatides also bind to chemokines, and seem to play a role in regulation of cytokine expression in human lymphocytes and monocytes. Aberrant metabolism of sulfatides, could cause several important human diseases. In this article, we describe the changes in sulfatide expression associated with such nervous disorders as metachromatic leukodystrophy (MLD), Parkinson's disease and Alzheimer's disease, and several types of cancer, e.g. colon cancer, kidney cancer, and ovarian cancer. We also discuss the involvement of sulfatides in cancer progression, diabetes and autoimmune and immune disorders such as multiple sclerosis. This acidic glycosphingolipids seem to play an important role in pathogenesis of infectious diseases, serving as receptors for binding various bacteria and viruses.