Neuronal sensitivity to tetanus toxin requires gangliosides

Tetanus toxin produces spastic paralysis in situ by blocking inhibitory neu rotransmitter release in the spinal cord. Although di- and trisialoganglios ides bind tetanus toxin, their role as productive toxin receptors remains u nclear. We examined toxin binding and action in spinal cord cell cultures g rown in the presence of fumonisin B-1, an inhibitor of ganglioside synthesi s. Mouse spinal cord neurons grown for 3 weeks in culture in 20 mu M fumoni sin B-1 develop dendrites, axons, and synaptic terminals similar to untreat ed neurons, even though thin layer chromatography shows a greater than 90% inhibition of ganglioside synthesis. Absence of tetanus and cholera toxin b inding by toxin-horseradish peroxidase conjugates or immunofluorescence fur ther indicates loss of mono- and polysialogangliosides. In contrast to cont rol cultures, tetanus toxin added to fumonisin B-1-treated cultures does no t block potassium-stimulated glycine release, inhibit activity-dependent up take of FM1-43, or abolish immunoreactivity for vesicle-associated membrane protein, the toxin substrate. Supplementing fumonisin B-1-treated cultures with mixed brain gangliosides completely restores the ability of tetanus t oxin to bind to the neuronal surface and to block neurotransmitter release. These data demonstrate that fumonisin B-1 protects against toxin-induced s ynaptic blockade and that gangliosides are a necessary component of the rec eptor mechanism for tetanus toxin.