GANGLIOSIDE GT1B AS A COMPLEMENTARY RECEPTOR COMPONENT FOR CLOSTRIDIUM-BOTULINUM NEUROTOXINS

Clostridium botulinum type B neurotoxin (BoNT/B) recognizes a complex of synaptotagmin II and ganglioside GT1b or GD1a as the high-affinity toxin binding site. Recombinant deletion mutants of synaptotagmin II a llowed us to demonstrate that the N-terminal domain including the tran smembrane region retains BoNT/B binding activity while the C-terminal domain is not involved in constituting the BoNT/B receptor. BoNT/B bin ding to reconstituted lipid vesicles containing synaptotagmin II and g angliosides showed that GT1b and GD1a confer the difference in the max imum binding capacity but not in the dissociation constant. The direct binding of GT1b to the deletion mutants revealed that the transmembra ne region is required to bind GT1b, suggesting that synaptotagmin II b inds to the ceramide portion of gangliosides within the plasma membran e. A monoclonal antibody against GT1b effectively inhibited not only B oNT/B binding to the reconstituted lipid vesicles and brain synaptosom es but also type A BoNT (BoNT/A) binding to brain synaptosomes. in add ition, the monoclonal antibody antagonized the action of both BoNT/A a nd BoNT/B on synaptic transmission of rat superior cervical ganglion n eurons. These results suggest that GT1b functions as a component of th e receptor complex. (C) 1998 Academic Press.