Voltage-dependent Ca²⁺ channels are a family of membrane proteins that allow cells to couple electrical activity to intracellular Ca²⁺ signaling¹. Voltage-gated Ca²⁺ channels are classified as T, L, N, P, Q and R, and are distinguished by their sensitivity to pharmacological blocks, single-channel conductance kinetics, and voltage-dependence.

On the basis of their voltage activation properties, voltage-gated Ca²⁺ subtypes can be further divided into two broad groups: the low (T-type) and high (L, N, P, Q and R-type) threshold-activated channels². The activity of the channel pore is modulated by 4 tightly-coupled subunits: an intracellular β subunit; a transmembrane γ subunit; and a disulphide-linked complex of α2 and δ subunits³. There are four distinct β subunits: β1, β2, β3 and β4⁴. There are 4 splice variants of the β2 subunit: β2a, β2b, β2c and β2d. β2a and β2b are expressed in heart, aorta and brain, and are 606- and 632-residue proteins, respectively. β2c and β2d (655 and 604 residues, respectively) are expressed in brain, and recent studies show beta-2c to be also expressed in heart. All splice variants differ in their N-terminal regions⁵.