CAV2 Knockout Cell Line (HEK293)

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 mechanisms that target voltage-gated Ca channels (Cas) to distinct subcellular compartments. In hippocampal neurons, Ca2s trigger neurotransmitter release at the presynaptic active zone, and Ca1s localize somatodendritically. After knockout of all three Ca2s, expression of Ca2.1, but not Ca1.3, restores neurotransmitter release. We find that chimeric Ca1.3s with Ca2.1 intracellular C-termini localize to the active zone, mediate synaptic vesicle exocytosis, and render release sensitive to Ca1 blockers. This dominant targeting function of the Ca2.1 C-terminus requires the first EF hand in its proximal segment, and replacement of the Ca2.1 C-terminus with that of Ca1.3 abolishes Ca2.1 active zone localization and function. We conclude that Ca intracellular C-termini mediate compartment-specific targeting.

GABA receptors (GBRs), the G protein-coupled receptors for GABA, regulate synaptic transmission throughout the brain. A main synaptic function of GBRs is the gating of Cav2.2-type Ca channels. However, the cellular compartment where stable GBR/Cav2.2 signaling complexes form remains unknown. In this study, we demonstrate that the vesicular protein synaptotagmin-11 (Syt11) binds to both the auxiliary GBR subunit KCTD16 and Cav2.2 channels. Through these dual interactions, Syt11 recruits GBRs and Cav2.2 channels to post-Golgi vesicles, thus facilitating assembly of GBR/Cav2.2 signaling complexes. In addition, Syt11 stabilizes GBRs and Cav2.2 channels at the neuronal plasma membrane by inhibiting constitutive internalization. Neurons of Syt11 knockout mice exhibit deficits in presynaptic GBRs and Cav2.2 channels, reduced neurotransmitter release, and decreased GBR-mediated presynaptic inhibition, highlighting the critical role of Syt11 in the assembly and stable expression of GBR/Cav2.2 complexes. These findings support that Syt11 acts as a vesicular scaffold protein, aiding in the assembly of signaling complexes from low-abundance components within transport vesicles. This mechanism enables insertion of pre-assembled functional signaling units into the synaptic membrane.