SNAP-25 Ser187 does not mediate phorbol ester enhancement of hippocampal synaptic transmission

Phorbol esters, activators of protein kinase C (PKC), have been shown to enhance synaptic transmission. One potential down-stream target of PKC in the presynaptic terminal is the soluble N-ethylmaleimide sensitive factor (NSF) attachment protein receptor (SNARE) SNAP-25. which has a PKC phosphorylation site in its C-terminal coil centered at serine 187 (S187/Ser187). We examined the role of S 187 in hippocampal synaptic transmission, After proteolytic cleavage of native SNAP-25 by botulinum neurotoxin E (BoNT/E). synaptic transmission was restored in a subset of transfected CA3 pyramidal cells with a toxin-resistant form of SNAP-25 containing unaltered S 187 (Swt), S 187 mutated to alanine (SA) or S 187 mutated to glutamate (SE). We observed that phorbol-12.13-diacetate (PDAc, 10 muM) induced potentiation of neurotransmission to a similar degree for both Swt and SA (2.4-fold and 3.1-fold increase, respectively). Furthermore, basal levels of transmission mediated by SE were reduced relative to that of Swt (failure rates of 72% and 41%, respectively). Together, these data suggest that phosphorylation of SNAP-25 S187 does not mediate the observed enhancement of neurotransmission by phorbol esters at hippocampal synapses. (C) 2003 Elsevier Ltd. All rights reserved.