Tetanus insensitive VAMP2 differentially restores synaptic and dense core vesicle fusion in tetanus neurotoxin treated neurons

• Published in: Scientific reports Vol. 10; no. 1; p. 10913
• Main Authors: Hoogstraaten, Rein I., van Keimpema, Linda, Toonen, Ruud F., Verhage, Matthijs
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 02-07-2020; Nature Publishing Group
• Subjects: 631/378; 631/378/340; 631/378/548; 631/378/87; Animals; Cells, Cultured; Cerebral Cortex - cytology; Dense core vesicles; Exocytosis - drug effects; Genes, Reporter; Hippocampus; Humanities and Social Sciences; Membrane Fusion - drug effects; Metalloendopeptidases; Mice; multidisciplinary; Nerve Tissue Proteins - drug effects; Nerve Tissue Proteins - physiology; Neuromodulation; Neurons; Neurons - drug effects; Neurons - physiology; Neuropeptide Y - analysis; Neurotoxins; Recombinant Proteins - metabolism; Science; Science (multidisciplinary); Secretory Vesicles - drug effects; Secretory Vesicles - ultrastructure; SNAP receptors; Synaptic Vesicles - drug effects; Synaptic Vesicles - ultrastructure; Tetanus; Tetanus Toxin - pharmacology; Vesicle fusion; Vesicle-Associated Membrane Protein 2 - drug effects; Vesicle-Associated Membrane Protein 2 - pharmacology
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-020-67988-2

The SNARE proteins involved in the secretion of neuromodulators from dense core vesicles (DCVs) in mammalian neurons are still poorly characterized. Here we use tetanus neurotoxin (TeNT) light chain, which cleaves VAMP1, 2 and 3, to study DCV fusion in hippocampal neurons and compare the effects on DCV fusion to those on synaptic vesicle (SV) fusion. Both DCV and SV fusion were abolished upon TeNT expression. Expression of tetanus insensitive (TI)-VAMP2 restored SV fusion in the presence of TeNT, but not DCV fusion. Expression of TI-VAMP1 or TI-VAMP3 also failed to restore DCV fusion. Co-transport assays revealed that both TI-VAMP1 and TI-VAMP2 are targeted to DCVs and travel together with DCVs in neurons. Furthermore, expression of the TeNT-cleaved VAMP2 fragment or a protease defective TeNT in wild type neurons did not affect DCV fusion and therefore cannot explain the lack of rescue of DCV fusion by TI-VAMP2. Finally, to test if two different VAMPs might both be required in the DCV secretory pathway,
Vamp1
null mutants were tested. However, VAMP1 deficiency did not reduce DCV fusion. In conclusion, TeNT treatment combined with TI-VAMP2 expression differentially affects the two main regulated secretory pathways: while SV fusion is normal, DCV fusion is absent.