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Brain‐derived neurotrophic factor facilitates in vivo internalization of tetanus neurotoxin C‐terminal fragment fusion proteins in mature mouse motor nerve terminals
Author(s) -
Roux Sylvie,
Saint Cloment Cécile,
Curie Thomas,
Girard Emmanuelle,
Mena FranciscoJavier Miana,
Barbier Julien,
Osta Rosario,
Molgó Jordi,
Brûlet Philippe
Publication year - 2006
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2006.05030.x
Subject(s) - glial cell line derived neurotrophic factor , internalization , microbiology and biotechnology , neurotrophic factors , ciliary neurotrophic factor , neuromuscular junction , neurotrophin , fusion protein , brain derived neurotrophic factor , chemistry , axoplasmic transport , biology , neuroscience , receptor , biochemistry , gene , recombinant dna
Abstract In a previous study it was reported that fusion proteins composed of the atoxic C‐terminal fragment of tetanus toxin (TTC) and green fluorescent protein or β‐galactosidase (GFP‐TTC and β‐gal‐TTC, respectively) rapidly cluster at motor nerve terminals of the mouse neuromuscular junction (NMJ). Because this traffic involves presynaptic activity, probably via the secretion of active molecules, we examined whether it is affected by brain‐derived neurotrophic factor (BDNF). Quantitative confocal microscopy and a fluorimetric assay for β‐gal activity revealed that co‐injecting BDNF and the fusion proteins significantly increased the kinetics and amount of the proteins' localization at the NMJ and their internalization by motor nerve terminals. The observed increases were independent of synaptic vesicle recycling because BDNF did not affect spontaneous quantal acetylcholine release. In addition, injecting anti‐BDNF antibody shortly before injecting GFP‐TTC, and before co‐injecting GFP‐TTC and BDNF, significantly reduced the fusion protein's localization at the NMJ. Co‐injecting GFP‐TTC with neurotrophin‐4 (NT‐4) or glial‐derived neurotrophic factor (GDNF), but not with nerve growth factor, neurotrophin‐3 or ciliary neurotrophic factor, also significantly increased the fusion protein's localization at the NMJ. Thus, TTC probes may use for their neuronal internalization endocytic pathways normally stimulated by BDNF, NT‐4 and GDNF binding. Different tyrosine kinase receptors with similar signalling pathways are activated by BDNF/NT‐4 and GDNF binding. Thus, activated components of these signalling pathways may be involved in the TTC probes' internalization, perhaps by facilitating localization of receptors of TTC in specific membrane microdomains or by recruiting various factors needed for internalization of TTC.