LRP1 influences trafficking of N-type calcium channels via interaction with the auxiliary α(2)δ-1 subunit

Voltage-gated Ca(2+) (Ca(V)) channels consist of a pore-forming α1 subunit, which determines the main functional and pharmacological attributes of the channel. The Ca(V)1 and Ca(V)2 channels are associated with auxiliary β- and α(2)δ-subunits. The molecular mechanisms involved in α(2)δ subunit trafficking, and the effect of α(2)δ subunits on trafficking calcium channel complexes remain poorly understood. Here we show that α(2)δ-1 is a ligand for the Low Density Lipoprotein (LDL) Receptor-related Protein-1 (LRP1), a multifunctional receptor which mediates trafficking of cargoes. This interaction with LRP1 is direct, and is modulated by the LRP chaperone, Receptor-Associated Protein (RAP). LRP1 regulates α(2)δ binding to gabapentin, and influences calcium channel trafficking and function. Whereas LRP1 alone reduces α(2)δ-1 trafficking to the cell-surface, the LRP1/RAP combination enhances mature glycosylation, proteolytic processing and cell-surface expression of α(2)δ-1, and also increase plasma-membrane expression and function of Ca(V)2.2 when co-expressed with α(2)δ-1. Furthermore RAP alone produced a small increase in cell-surface expression of Ca(V)2.2, α(2)δ-1 and the associated calcium currents. It is likely to be interacting with an endogenous member of the LDL receptor family to have these effects. Our findings now provide a key insight and new tools to investigate the trafficking of calcium channel α(2)δ subunits.