The intracellular C-terminus confers compartment-specific targeting of voltage-gated Ca²⁺ channels

To achieve the functional polarization that underlies brain computation, neurons sort protein material into distinct compartments. Ion channel composition, for example, differs between axons and dendrites, but the molecular determinants for their polarized trafficking remain obscure. Here, we identify the mechanisms that target voltage-gated Ca²⁺ channels (Ca_Vs) to distinct subcellular compartments. In hippocampal neurons, Ca_V2s trigger neurotransmitter release at the presynaptic active zone, and Ca_V1s localize somatodendritically. After knockout of all three Ca_V2s, expression of Ca_V2.1, but not of Ca_V1.3, restores neurotransmitter release. Chimeric Ca_V1.3 channels with Ca_V2.1 intracellular C-termini localize to the active zone, mediate synaptic vesicle exocytosis, and render release fully sensitive to blockade of Ca_V1 channels. This dominant targeting function of the Ca_V2.1 C-terminus requires an EF hand in its proximal segment, and replacement of the Ca_V2.1 C-terminus with that of Ca_V1.3 abolishes Ca_V2.1 active zone localization. We conclude that the intracellular C-termini mediate compartment-specific Ca_V targeting.