Botulinum neurotoxin light chains inhibit both Ca²⁺‐induced and GTP analogue‐induced catecholamine release from permeabilised adrenal chromaffin cells

Using digitonin-permeabilised bovine adrenal chromaffin cells, the effects of botulinum neurotoxin light chains on exocytosis triggered by Ca2+ or by GppNHp were examined. Botulinum neurotoxin D light chain, prepared as a His(6)-tagged recombinant protein, cleaved VAMP and substantially inhibited catecholamine release due to Ca2+ and GppNHp. Botulinum neurotoxin C1 and E light chains produced partial inhibition of both Ca(2+)- and GppNHp-induced catecholamine release. These results suggest that Ca(2+)-dependent exocytosis and Ca(2+)-independent exocytosis triggered by a non-hydrolysable GTP analogue occurs via a SNARE-dependent mechanism in chromaffin cells.