Serotonin controls various behavioral states across several species including the nematode C. elegans, where it inhibits locomotion. Just how serotonin regulates movement has not been clear. Nurrish et al. now report that serotonin inhibits synaptic transmission at neuromuscular junctions of C. elegans by inhibiting the release of acetylcholine. In a genetic screen, the authors identified a required role for diacylglycerol kinase (DAGK) in the serotonin-mediated inhibition of acetylcholine release. The presence of DAG in the presynaptic nerve terminal was regulated by both DAGK and a Gαo subunit that was already implicated in serotonin signaling. A decrease in DAG in nerve terminals correlated with a decrease INC-13, a DAG-binding protein that stimulates synaptic vesicle release. The authors propose that a signaling cascade involving Gαo, DAGK, DAG, and UNC-13 can modulate synaptic transmission by controlling neurotransmitter release.
Nurrish, S., Segalat, L., and Kaplan, J.M. (1999) Serotonin inhibition of synaptic transmission: Gαo decreases the abundance of UNC-13 at release sites. Neuron 24: 231-242. Online Journal