Dynamic Regulation of Synaptic Calcium Channels by Neurexins
Synapses constitute cellular interfaces between neurons that mediate the flow of information via specialized pre- and postsynaptic membrane domains. Voltage-gated calcium channels (VGCCs) are essential for this process because they trigger Ca2+-dependent release of neurotransmitter from vesicles at the presynaptic membrane. We reported earlier that Ca2+-dependent release is impaired when the synaptic cell adhesion molecules α-neurexins (αNrxns) are deleted, pointing to an intricate link between cell-cell recognition/adhesion and neurotransmission. However, regulation of the abundance and activity of VGCCs at the synaptic interface, and the possible involvement of Nrxns, are poorly understood. Here, we will investigate the mechanisms and molecular determinants of this link based on our recent observation that αNrxns may functionally interact with α2δ, an auxiliary subunit of VGCCs. Using mostly live cell imaging techniques, we will monitor Ca2+ influx and vesicle release from synapses of primary hippocampal neurons. We will obtain those cells from wild-type and genetically modified mice, in which we express normal and mutant variants of Nrxns and α2δ. To analyze the effects of Nrxns/α2δ on VGCC-mediated Ca2+ influx and neurotransmitter release, we will dissect the contribution of different classes of VGCCs, and study properties and dynamics of the regulation by Nrxns/α2δ. Since VGCCs are critical for synaptic strength, this project will improve our understanding of how neurons regulate an important function of their synaptic interfaces.