REGULATED SECRETION IS IMPAIRED IN ATT-20 ENDOCRINE-CELLS STABLY TRANSFECTED WITH BOTULINUM NEUROTOXIN TYPE-A LIGHT-CHAIN

Botulinum neurotoxin type A (BoNT/A) inhibits neurotransmitter release by specific cleavage of SNAP-25, a synaptosome-associated protein als o expressed in the ACTH secretory cell line AtT-20. Expression of ligh t chain BoNT/A (L-BoNT/A) gene transfected into AtT-20 cells resulted in a cleaved form of SNAP-25 indistinguishable from that generated by bona fide BoNT/A. LBoNT/A-transfected cells showed no difference in re plication rate, viability, or phenotype, compared with control AtT-20 cells. In contrast, L-BoNT/A-transfected cells could not be induced to secrete ACTH upon stimulation by 8-bromo-cAMP or KCl. In addition, al pha-latrotoxin induced ACTH release from control cells, but not from L -BoNT/A-transfected cells. These experiments suggest an important role for SNAP-25 in regulated secretion from AtT-20 cells and underline th e usefulness of this cell system as a tool for the study of the molecu lar mechanism of peptide hormone secretion.