The distance between Ca(V)2.1 voltage-gated Ca2+ channels and the Ca2+ sensor responsible for vesicle release at presynaptic terminals is critical for determining synaptic strength. Yet, the molecular mechanisms responsible for a loose coupling configuration of CaV2.1 in certain synapses or developmental periods and a tight one in others remain unknown. Here, we examine the nanoscale organization of two Ca(V)2.1 splice isoforms (Ca(V)2.1[EFa] and Ca(V)2.1[EFb]) at presynaptic terminals by superresolution structured illumination microscopy. We find that Ca(V)2.1[EFa] is more tightly co-localized with presynaptic markers than Ca(V)2.1[EFb], suggesting that alternative splicing plays a crucial role in the synaptic organization of Ca(V)2.1 channels.
