[Immunochemical and functional study of the latrotoxin molecule]

A panel of monoclonal antibodies (mAb) against alpha-latrotoxin (LT) has been produced and their main characteristics have been determined. The influence of mAb on the functional effects of LT in synaptosomes from rat brain and on the channel formation in bilayer lipid membrane has been investigated. These mAbs do not inhibit binding of LT to rat synaptosomes but modify LT-receptor interaction in terms of LT's channel-forming and secretogenic effects. Antibodies A6 and A24 block these effects, whereas A4 partially preserves the secretogenic action of LT and completely blocks its channel-forming action. Only antibodies A15 affect the LT ability to form cationic channels in BLM, inducing considerable decrease in the frequency of the channel formation. These data and their analysis allow to identify several functional (and, probably, structural) domains of LT responsible for: 1) toxin-receptor interaction; 2) channel-forming and related calcium-dependent secretogenic effects; 3) calcium-independent secretogenic effects; 4) formation of cationic channels in the artificial lipid bilayer.