Glycolipids are
glycoconjugates that are predominantly found on the extracellular surface of cells ranging from bacteria to men. In bacteria and plants, glycoglycerolipids represent the main
glycolipid species.
Ceramides as carrier for
glycans, termed
glycosphingolipids (GSLs), are characteristic for vertebrates and insects. The
glycan part is involved in a variety of biological activities including cell adhesion and initiation of signaling. Most of these functions rest on two basic principles: (1) GSLs spontaneously contribute to organize
lipid rafts in biological membranes, thereby forming functional complexes ('glycosynapses') with receptor
proteins and
ion channels and (2) their
glycans are bound by receptors like
galectins (
protein-
glycan recognition) or cognate
glycans (
glycan-
glycan recognition). This interaction modulates cell adhesion, differentiation and growth processes. Besides their contribution to normal cell behavior, GSL expression patterns also influence disease processes by inducing cellular malfunctions when aberrant, as highlighted by inherited disorders of GSL metabolism like
sphingolipidoses. Altered GSL patterns are also associated with common neurological
diseases, autoimmune diseases and
cancer. With respect to
infections, various GSL-presented
glycans are attachment sites for bacteria and viruses as well as primary targets for
bacterial toxins. This review provides an introduction to GSL structures, their nomenclature and metabolism. Building on this, normal and pathological functions of GSL will be surveyed.