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[摘要]：Botulinum neurotoxins (BoNTs) are the etiological agents responsible for botulism, a disease characterized by peripheral neuromuscular blockade and a characteristic flaccid paralysis of humans. BoNTs are the most lethal known poisons affecting humans and have been recognized, as a potential bioterrorist threat. Current treatments for botulinum poisoning are predominately prophylactic in nature relying on passive immunization with antitoxins. Inhibition of the BoNT light chain metalloprotease (LC) has emerged as a new therapeutic strategy for the treatment of botulism that may provide an effective postexposure remedy. A high-throughput screening effort against the light chain of BoNT serotype A (LC/A) was conducted with the Johns Hopkins Clinical Compound Library composed of over 1,500 existing drugs. Lomofungin, a natural product first isolated in the late 1960s, was identified as an inhibitor of LC/A, displaying classical noncompetitive inhibition kinetics with a K-i of 6.7 +/- 0.7 mu M. The inhibition profile of lomofungin has been delineated by the use of both an active site inhibitor, 2,4-dichlorocinnamic hydroxamate, and a noncompetitive inhibitor D-chicoric acid. The inhibitor combination studies reveal that lomofungin binding is nonmutually exclusive (synergistic) with both inhibitors: the mechanistic implications of these observations are discussed. Lastly, cellular efficacy was investigated using a rat primary cell model which demonstrated that lomofungin can protect against SNAP-25 cleavage, the intracellular protein target of LC/A. |
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