STIMULUS-INDUCED acetylcholine (ACh) exocytosis from presynaptic nerve
terminals involves two important steps: fusion of ACh loaded vesicles
at presynaptic release sites, followed by release into the synaptic c
left. We studied the role of the putative vesicle fusion protein SNAP-
25 in this process. The nerve growth factor-differentiated PC12 cell l
ine was used as an experimental model. A bee venom tetradecapeptide (I
NLKA-LAALAKKIL-NH2) phospholipase A(2) (PLA(2)) activator, mastoparan,
was used to induce ACh release. Treatment of PC12 cells with appropri
ate antisense oligonucleotides blocked SNAP-25 expression, as judged b
y Western blot protein analysis with a specific monoclonal antibody. D
espite apparent elimination of SNAP-25, treatment of differentiated PC
12 cells with mastoparan and high (80 mM) K+ induced ACh exocytosis. T
he results indicate that in PC12 cells, ACh exocytosis due to mastopar
an plus K+ can occur in the absence of SNAP-25.