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Title: Trafficking and neurotrophic effects of botulinum neurotoxin type A
Author: Solabre Valois, Luis
ISNI:       0000 0004 7972 7631
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2019
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Botulinum neurotoxin type A (BoNT/A) is a SNAP-25-cleaving protease produced by the bacterium C. botulinum that blocks synaptic transmission at the neuromuscular junction. Inhalation of 1 g can be lethal while lower doses can result in a paralysis that lasts for several months. However, this terrifying potency and persistence has converted it into a valuable drug in many muscle and neurological disorders. Paradoxically, BoNT/A induces nerve regeneration and BoNT/E, a BoNT/A homolog, has a much shorter persistence despite many mechanistic similarities. Tools for the comparative study of BoNT/A and BoNT/E were produced but shown to be ineffective for purposes of this thesis. By using a catalytically inactive mutant of BoNT/A (BoNT/A(0)), I showed that the toxin enters neurons through multiple mechanisms before entering the endocytic pathway. BoNT/A(0) escaped lysosomal degradation but was degraded by the proteasome. Furthermore, a fraction of BoNT/A was static at the early endosome and another fraction was exocytosed and was able to re-enter neurons as a full-length toxin. In addition, this research shows that neurite outgrowth induced by BoNT/A(0) is restricted to axonal outgrowth in vitro and is mediated by activation of the small GTPase Rac1 through the binding domain of BoNT/A (HCC/A). HCC/A also induced the formation of filopodia presynaptic vesicle release and neurogenesis. This thesis provides a model for the trafficking of full-length BoNT/A prior to any catalytic action and reformulates BoNT/A receptor binding domain as a neurotrophic factor.
Supervisor: Henley, Jeremy Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Botulinum ; Neurotoxin ; BoNT ; Botulism ; Neuron ; Trafficking ; Neurotrophic