Gangliosides modulate glutamate receptor binding in rat brain synaptic plasma membranes.

The influence of gangliosides on the binding of L-[3H]glutamate (Glu) to its receptor(s) on isolated rat brain synaptic plasma membranes was investigated in two different buffer systems using an in vitro filter binding assay. It was found that the tested pure monosialogangliosides GM1 and GM2 as well as the polysialogangliosides GT1b and GD1a enhanced binding by up to about 100%, but only in the presence of 5 mM calcium. The binding site involved was sensitive to quisqualate but insensitive to N-methyl-D-aspartate and kainate. GM1 did exert its stimulating effect by increasing the number of binding sites on the membranes whereas the receptor's affinity for L-Glu was unchanged. Regional differences in rat brain were found: while the hippocampus and cortex exhibited significant Ca/GM1-induced stimulation of Glu binding, the cerebellum was unaffected. Our results suggest modulation of at least one subtype of the Glu receptor by gangliosides.