Snake presynaptic neurotoxins with phospholipase A2 activity induce punctate swellings of neurites and exocytosis of synaptic vesicles.
The mechanisms of action of four snake presynaptic phospholipase A2 neurotoxins were investigated in cultured neurons isolated from various parts of the rat brain. Strikingly, physiological concentrations of notexin, beta-bungarotoxin, taipoxin or textilotoxin induced a dose-dependent formation of discrete bulges at various sites of neuronal projections. Neuronal bulging was paralleled by the redistribution of the two synaptic vesicle markers synaptophysin I (SypI) and vesicle-attached membrane protein 2 (VAMP2) to the bulges, and by the exposure of the luminal domain of synaptotagmin on the cell surface. These neurotoxins induced glutamate release from cultured neurons similarly to the known evoked release of acetylcholine from neuromuscular junctions. In addition, partial fragmentation of F-actin and neurofilaments was observed in neurons, but not in astrocytes. These findings indicate that these snake presynaptic neurotoxins act with by same mechanism and that the observed phenotype results from the fusion of synaptic vesicles with the plasma membrane not balanced by an adequate membrane retrieval. These changes closely resemble those occurring at neuromuscular junctions of intoxicated animals and fully qualify these primary neuronal cultures as pertinent models for studying the molecular mode of action of these neurotoxins.
Rigoni
Michela
M
Department of Biomedical Sciences and CNR Institute of Neuroscience, University of Padova, Viale G. Colombo 3, 35121 Padova, Italy.
Schiavo
Giampietro
G
Weston
Anne E
AE
Caccin
Paola
P
Allegrini
Federica
F
Pennuto
Maria
M
Valtorta
Flavia
F
Montecucco
Cesare
C
Rossetto
Ornella
O
D000818:Animals; D002478:Cells, Cultured; D003964:Diaphragm / Q000166:cytology / Q000187:drug effects* / Q000294:innervation; D005089:Exocytosis; D018698:Glutamic Acid / Q000378:metabolism; D008297:Male; D051379:Mice; D016501:Neurites / Q000187:drug effects*; D009498:Neurotoxins / Q000633:toxicity*; D010741:Phospholipases A / Q000633:toxicity*; D054467:Phospholipases A2; D010791:Phrenic Nerve / Q000166:cytology / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D012910:Snake Venoms / Q000737:chemistry*; D013572:Synaptic Vesicles / Q000187:drug effects*
D009498:Neurotoxins; D012910:Snake Venoms; D018698:Glutamic Acid; D010741:Phospholipases A; D054467:Phospholipases A2