[Internalization and degradation of latrotoxin bound to rat brain synaptosomes].

The accessibility to trypsin of 125I-labeled latrotoxin bound to rat brain synaptosomes was investigated. It was shown that latrotoxin bound to synaptosomes in the cold can be practically completely removed by trypsin treatment. The resistance of latrotoxin to proteolysis increases during its incubation with synaptosomes (37 degrees C). Concanavalin A (10(-6) M) decreases toxin binding by 30%, but fully prevents internalization (incorporation). Moreover, latrotoxin is not incorporated into synaptosomal membrane fragments irrespective of duration and temperature of incubation. Latrotoxin incorporated into synaptosomal membranes undergoes degradation by endogenous proteases resulting in the formation of TCA-soluble products.