nPKCε Mediates SNAP-25 Phosphorylation of Ser-187 in Basal Conditions and After Synaptic Activity at the Neuromuscular Junction.

Protein kinase C and substrates like SNAP-25 regulate neurotransmission. At the neuromuscular junction (NMJ), promotes neurotransmitter release during synaptic activity. Thirty minutes of muscle contraction enhances presynaptic duanyu1531 isoform levels, specifically and through retrograde BDNF/TrkB signaling. This establishes a larger pool of these duanyu1531 isoforms ready to promote neuromuscular transmission. The duanyu1531 phosphorylation site in SNAP-25 has been mapped to the serine 187 (Ser-187), which is known to enhance calcium-dependent neurotransmitter release in vitro. Here, we localize SNAP-25 at the NMJ and investigate whether cduanyu1531βI and/or regulate SNAP-25 phosphorylation. We also investigate whether nerve and muscle cell activities regulate differently SNAP-25 phosphorylation and the involvement of BDNF/TrkB signaling. Our results demonstrate that nduanyu1531ε isoform is essential to positively regulate SNAP-25 phosphorylation on Ser-187 and that muscle contraction prevents it. TrkB and cduanyu1531βI do not regulate SNAP-25 protein level or its phosphorylation during neuromuscular activity. The results provide evidence that nerve terminals need both pre- and postsynaptic activities to modulate SNAP-25 phosphorylation and ensure an accurate neurotransmission process.

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