CaV2 channel subtype expression in rat sympathetic neurons is selectively regulated by α2δ subunits

Abstract

ABSTRACTType two voltage gated calcium (CaV2) channels are the primary mediators of neurotransmission at neuronal presynapses, but their function at neural soma is also important in regulating excitability.1 Mechanisms that regulate CaV2 channel expression at synapses have been studied extensively, which motivated us to perform similar studies in the soma. Rat sympathetic neurons from the superior cervical ganglion (SCG) natively express CaV2.2 and CaV2.3.2 We noted previously that heterologous expression of CaV2.1 but not CaV2.2 results in increased calcium current in SCG neurons.3 In the present study, we extended these observations to show that both CaV2.1 and CaV2.3 expression resulted in increased calcium currents while CaV2.2 expression did not. Further, CaV2.1 could displace native CaV2.2 channels, but CaV2.3 expression could not. Heterologous expression of the individual accessory subunits α2δ-1, α2δ-2, α2δ-3, or β4 alone failed to increase current density, suggesting that the calcium current ceiling when CaV2.2 was over-expressed was not due to lack of these subunits. Interestingly, introduction of recombinant α2δ subunits produced surprising effects on displacement of native CaV2.2 by recombinant channels. Both α2δ-1 and α2δ-2 seemed to promote CaV2.2 displacement by recombinant channel expression, while α2δ-3 appeared to protect CaV2.2 from displacement. Thus, we observe a selective prioritization of CaV channel functional expression in neurons by specific α2δ subunits. These data highlight a new function for α2δ subtypes that could shed light on subtype selectivity of CaV2 membrane expression.