Calcium overload in nerve terminals of cultured neurons intoxicated by alpha-latrotoxin and snake PLA2 neurotoxins.
Snake presynaptic neurotoxins with phospholipase A2 (PLA2) activity cause degeneration of the neuromuscular junction. They induce depletion of synaptic vesicles and increase the membrane permeability to Ca(2+) which fluxes from the outside into the nerve terminal. Moreover, several toxins were shown to enter the nerve terminals of cultured neurons, where they may display their PLA2 activity on internal membranes. The relative contribution of these different actions in nerve terminal degeneration remains to be established. To gather information on this point, we have compared the effects of beta-bungarotoxin, taipoxin, notexin and textilotoxin with those of alpha-latrotoxin on the basis of the notion that this latter toxin is well known to cause massive Ca(2+) influx and exocytosis of synaptic vesicles. All the parameters analysed here, including calcium imaging, are very similar for the two classes of neurotoxins. This indicates that Ca(2+) overloading plays a major role in the degeneration of nerve terminals induced by the snake presynaptic neurotoxins.
Tedesco
Erik
E
Dipartimento di Scienze Biomediche Sperimentali, Università di Padova and Istituto di Neuroscienze del Consiglio Nazionale delle Ricerche, Padova, Italy.
Rigoni
Michela
M
Caccin
Paola
P
Grishin
Eugene
E
Rossetto
Ornella
O
Montecucco
Cesare
C