A membrane receptor for gangliosides is associated with central nervous system myelin.

A binding protein specific for major neuronal gangliosides was detected on rat brain membranes using a synthetic ganglioside-protein conjugate, 125I-(GT1b)4BSA (bovine serum albumin derivatized with 4 mol of ganglioside GT1b/mol of protein), as a radioligand. Specific binding of the ligand displayed marked regional variation within the brain, with white matter-enriched regions demonstrating the highest binding activity. Autoradiographic localization of 125I-(GT1b)4BSA binding to tissue sections revealed selective association with myelinated pathways throughout the brain. The ligand also bound preferentially to brain subcellular fractions enriched in myelin, even after removal of axolemma. In contrast, peripheral nerve myelin had little binding activity. The myelin-associated ganglioside receptor detected by 125I-(GT1b)4BSA binding appears to be a novel oligodendroglial membrane protein which preferentially recognizes neuronal gangliosides.

Carbohydrate-specific cell adhesion directly to glycosphingolipids separated on thin-layer chromatography plates.

Cell surface carbohydrates and complementary carbohydrate receptors may mediate cell-cell recognition and adhesion. We report a method which detects carbohydrate-specific adhesion of intact eukaryotic cells directly to glycosphingolipids separated on thin-layer chromatography plates. Various glycosphingolipids were chromatographed on high-performance silica gel thin-layer chromatography plates, and the plates were coated with a thin film of poly(isobutyl methacrylate) and mounted in a specially designed plexiglass chamber. Metabolically radiolabeled cells were added to the chamber, which was then sealed and gently centrifuged to bring the cells into contact with the surface of the TLC plate. After incubation to allow adhesion to occur, the chamber was inverted and centrifuged to remove nonadherent cells from the plate surface. The plate was removed from the chamber, the adherent cells were fixed in place with glutaraldehyde, and the plate was dried and subjected to autoradiography. Chicken hepatocytes, which have a cell surface receptor for N-acetylglucosamine, adhered only to those areas of the plate to which appropriate glycosphingolipids (having that terminal sugar) had migrated. Cell adhesion was blocked by soluble N-acetylglucosamine (but not by other sugars) and was readily detectable using a variety of developing solvents. Cell adhesion to as little as 8 pmol of the appropriate lipid was readily detected. This method can be used to test glycosphingolipids as cell surface recognition markers for a variety of cell types.

Gangliosides support neural retina cell adhesion.

Cell surface carbohydrates and complementary carbohydrate receptors may mediate cell-cell recognition during neuronal development. To model such interactions, we developed a technique to test the ability of cell surface lipids (particularly glycosphingolipids) to mediate specific cell recognition and adhesion (Blackburn, C.C., and Schnaar, R.L. (1983) J. Biol. Chem. 258, 1180-1188). When cells were incubated on plastic microwells adsorbed with various glycolipids, carbohydrate-specific cell adhesion was readily detected. We report here the use of this method to study adhesion of embryonic chick neural retina cells to purified cell surface lipids. Rapid and specific cell adhesion was observed when the neural retina cells were incubated on surfaces adsorbed with gangliosides (an important class of neuronal cell surface glycoconjugates) but not on surfaces adsorbed with various neutral glycosphingolipids, phospholipids, or sulfatide. This suggests that the observed cell adhesion was specific for the carbohydrate moiety of the adsorbed ganglioside and was not due to nonspecific ionic or hydrophobic interactions. Although the surface density of adsorbed lipid required to support cell adhesion was the same for all gangliosides examined, the extent of adhesion varied when different purified gangliosides were used. Ganglioside-specific adhesion was not dependent on the presence of calcium (at 37 degrees C) and was attenuated by pretreatment of the cells with trypsin. The extent of ganglioside-directed neural retinal cell adhesion varied with embryonic age. These results imply that gangliosides may play a role in cell-cell recognition in the developing nervous system.