A novel region in the Ca V 2.1 α 1 subunit C-terminus regulates fast synaptic vesicle fusion and vesicle docking at the mammalian presynaptic active zone.

In central nervous system (CNS) synapses, action potential-evoked neurotransmitter release is principally mediated by Ca _V 2.1 calcium channels (Ca _V 2.1) and is highly dependent on the physical distance between Ca _V 2.1 and synaptic vesicles (coupling). Although various active zone proteins are proposed to control coupling and abundance of Ca _V 2.1 through direct interactions with the Ca _V 2.1 α1 subunit C-terminus at the active zone, the role of these interaction partners is controversial. To define the intrinsic motifs that regulate coupling, we expressed mutant Ca _V 2.1 α ₁ subunits on a Ca _V 2.1 null background at the calyx of Held presynaptic terminal. Our results identified a region that directly controlled fast synaptic vesicle release and vesicle docking at the active zone independent of Ca _V 2.1 abundance. In addition, proposed individual direct interactions with active zone proteins are insufficient for Ca _V 2.1 abundance and coupling. Therefore, our work advances our molecular understanding of Ca _V 2.1 regulation of neurotransmitter release in mammalian CNS synapses.