The overall goal of this proposal is to understand how clostridial neurotoxins interact with their target cells and to use this knowledge to develop effective inhibitors of the toxin-cell interaction. Three botulinum toxins (A,B and E) will be studied to determine whether observations made with one toxin (botulinum toxin A) might have general applicability. If the botulinum toxins behave similarly, comparisons will be made to tetanus toxin to determine what similarities exist between the two classes of neurotoxins. Specifically, studies of the binding of botulinum toxins B and E to G1b gangliosides and derivatives thereof will be carried out. Results will be compared to those obtained for botulinum toxin A and tetanus toxin. Accumulating evidence suggests that gangliosides may not be the only cell surface receptor for these neurotoxins. In recent studies, we have found that botulinum toxin A, its heavy chain and the carboxy terminal half of the heavy chain bind to synaptosomal proteins. Tetanus toxin also adhered to synaptosomal proteins but it had to be preincubated with GT1b in order to bind to protein. The protein adhered to by both neurotoxins has an apparent molecular weight of approximately 77 kDa and is glycosylated. Experiments designed to purify and characterize the approximately kDa protein will be continued, and the site(s) adhered to by the toxin will be identified as will the portion of the neurotoxin responsible for the binding, and in in vitro experiments designed to identify the functional aspects of specific interactions.
