Complex gangliosides affect GD 3 accessibility to antibody in developing neuronal cells

Abstract

Ganglioside expression of embryonic chick retina cells developed in vitro was analyzed by indirect immunofluorescence. Immature neurons were GD 3 positive cells and the labeling was chiefly distributed all over their cell membrane. Mature neurons became GD 3 negative and expressed complex gangliosides of the a- and b-pathways; nevertheless, the content of GD 3 accounted for approximately 40% of the total gangliosides in these cells. Neuraminidase hydrolysis pointed out that GD 3 was located in membrane of differentiated cells. The frequency of cells with the GD 3 immunostain localized in restricted areas of membrane of undifferentiated neurons increased significantly after adding a mixture of bovine brain gangliosides (largely complex gangliosides). Antibody binding to immobilized GD 3 showed a dose-dependent inhibition by adding a mixture of bovine brain gangliosides, GM 1, GD 1a or asialo-GM 1. Glycosphingolipids with shorter oligosaccharide chains, as cerebrosides or sulfatides, did not affect this binding. These results suggest that, concomitant with the accretion of content of complex gangliosides, a rearrangement in the membrane would occur, which progressively masks GD 3 to its antibody. This rearrangement might affect putative ganglioside functions involved in neuronal differentiation.