Acidic motif responsible for plasma membrane association of the voltage-dependent calcium channel β1b subunit

Voltage-dependent calcium channels consist of a pore-forming transmembrane α1-subunit, which is known to associate with a number of accessory subunits, including α2-δ- and β-subunits. The β-subunits, of which four have been identified (β1–4), are intracellular proteins that have marked effects on calcium channel trafficking and function. In a previous study, we observed that the β1b-subunit showed selective plasma membrane association when expressed alone in COS7 cells, whereas β3 and β4 did not. In this study, we have examined the basis for this, and have identified, by making chimeric β-subunits, that the C-terminal region, which shows most diversity between β-subunits, of β1b is responsible for its plasma membrane association. Furthermore we have identified, by deletion mutations, an 11-amino acid motif present in the C terminus of β1b but not in β3 (amino acids 547–556 of β1b, WEEEEDYEEE), which when deleted, reduces membrane association of β1b. Future research aims to identify what is binding to this sequence in β1b to promote membrane association of this calcium channel subunit. It is possible that such membrane association is important for the selective localization or clustering of particular calcium channels with which β1b is associated