Regulatory Roles for GTP-Binding Proteins in Nerve Terminals

During the past few years, some roles of GTP-binding proteins in the presynaptic terminal have started to be elucidated. Small GTP-binding proteins, such as rab3a and dynamin, are essential for controlling distinct steps in the cycling of synaptic vesicles, while heterotrimeric G proteins regulate calcium channels, potassium channels, and the secretory machinery either directly or through second messenger pathways. The recent demonstration that G protein-mediated modulation of N-type calcium channels of the presynaptic terminal requires intact syntaxin suggests that G protein regulation of neurotransmitter release may also show an interesting context dependence. Interesting new twists in the G protein story are just emerging.