Gangliosides in acetylcholine receptor-rich membranes from Torpedo marmorata and Discopyge tschudii.

The ganglioside composition of membranes enriched in nicotinic acetylcholine receptor (AChR) from the electric rays Discopyge tschudii and Torpedo marmorata has been determined, and compared to that of total electric organ. A ganglioside having the chromatographic mobility of GM2 constitutes the major ganglioside (approximately 60%) in total D. tschudii electric organ, followed by a component with the mobility of GD3 (approximately 10%), and a component running just below GD1a (about 12%). Minor constituents running as GM3 (2%) and as polysialogangliosides (comprising 8-15%) were also observed. Purified native membranes of D. tschudii and T. marmorata displayed a similar profile, except that they were richer in a GM1-like component, and the proportion of GM2-like gangliosides was lower than that in total electric organ. Using a 125I-cholera toxin overlay assay on neuraminidase-treated high-performance thin layer chromatograms, the presence of GM1, GD1a and trace amounts of GD1b and GT1 (or GQ) were detected in D. Tschudii total membranes. Immunocytochemical trechniques showed the co-localization of gangliosides GQ1c/GT1c/GP1c, recognized by the monoclonal antibody Q211, and the AChR at the ventral, innervated face of the electrocyte.