L-type Ca²⁺ channel, VGCC, voltage-dependent, β4-subunit, CACNB4, of 520 aas and possibly 0 TMSs.  The α1 subunit, comprises the ion-permeable channel, and there are three auxiliary subunits: β, α₂δ, and γ. β is necessary for forward trafficking of the α1 subunit to the plasma membrane.  It increases peak calcium current, shifting the voltage dependencies of activation and inactivation, modulating G protein inhibition and controlling the alpha-1 subunit membrane targeting (Helton and Horne 2002).  Subunit β1b is enriched in the β4 interactome of male relative to female mice, and thus may have served to mitigate VGCC overexpression-mediated spine loss in male mice (Parker et al. 2024).