Targeted delivery into motor nerve terminals of inhibitors for SNARE‐cleaving proteases via liposomes coupled to an atoxic botulinum neurotoxin

• Published in: The FEBS journal 2012-07, Vol.279 (14), p.2555-2567
• Main Authors: Edupuganti, Om P., Ovsepian, Saak V., Wang, Jiafu, Zurawski, Tomas H., Schmidt, James J., Smith, Leonard, Lawrence, Gary W., Dolly, J. Oliver
• Format: Article
• Language: English
• Subjects: Animals; biotin–streptavidin conjugation; Botulinum Toxins - chemistry; Botulinum Toxins - genetics; Botulinum Toxins - metabolism; Botulinum Toxins, Type A; Clostridium botulinum; Diaphragm - metabolism; Drug Delivery Systems - methods; Fluorescein - chemistry; Gene loci; Humans; Liposomes; Mice; Microscopy, Confocal; Motor ability; Motor Neurons - metabolism; Mutation; Nerve Endings - metabolism; neuromuscular transmission; Neurotoxicity; Paralysis - metabolism; Paralysis - therapy; Peptides; pharmaceutical carriers; Presynaptic Terminals - metabolism; Protease Inhibitors - administration & dosage; Protease Inhibitors - chemistry; Proteases; Recombinant Fusion Proteins - chemistry; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; SNAP‐25; SNARE Proteins - metabolism; Streptavidin - genetics; Streptavidin - metabolism; Synaptosomal-Associated Protein 25 - metabolism
• ISSN: 1742-464X; 1742-4658
• DOI: 10.1111/j.1742-4658.2012.08638.x

A targeted drug carrier (TDC) is described for transferring functional proteins or peptides into motor nerve terminals, a pivotal locus for therapeutics to treat neuromuscular disorders. It exploits the pronounced selectivity of botulinum neurotoxin type B (BoNT/B) for interacting with acceptors on these cholinergic nerve endings and becoming internalized. The gene encoding an innocuous BoNT/B protease‐inactive mutant (BoTIM) was fused to that for core streptavidin, expressed in Escherichia coli and the purified protein was conjugated to surface‐biotinylated liposomes. Such decorated liposomes, loaded with fluorescein as traceable cargo, acquired pronounced specificity for motor nerve terminals in isolated mouse hemidiaphragms and facilitated the intraneuronal transfer of the fluor, as revealed by confocal microscopy. Delivery of the protease light chain of botulinum neurotoxin type A (BoNT/A) via this TDC accelerated the onset of neuromuscular paralysis, indicative of improved translocation of this enzyme into the presynaptic cytosol with subsequent proteolytic inactivation of synaptosomal‐associated protein of molecular mass 25 kDa (SNAP‐25), an exocytotic soluble N‐ethyl‐maleimide‐sensitive factor attachment protein receptor (SNARE) essential for neurotransmitter release. BoTIM‐coupled liposomes, loaded with peptide inhibitors of proteases, yielded considerable attenuation of the neuroparalytic effects of BoNT/A or BoNT/F as a result of their cytosolic transfer, the first in situ demonstration of the ability of designer antiproteases to suppress the symptoms of botulism ex vivo. Delivery of the BoNT/A inhibitor by liposomes targeted with the full‐length BoTIM proved more effective than that mediated by its C‐terminal neuroacceptor‐binding domain. This demonstrated versatility of TDC for nonviral cargo transfer into cholinergic nerve endings has unveiled its potential for direct delivery of functional targets into motor nerve endings. Targeted drug carrier (TDC) for delivering cargo (●) into motor neuron cytosol. A protease‐inactive mutant of botulinum neurotoxin B tagged with core streptavidin (CS‐BoTIM/B; ), attached to surface biotins (●) on liposomes, binds via gangliosides (G) and synaptotagmin I/II (Syt) prior to fusion with the neuronal membrane.