Voltage-gated Ca²⁺ (Ca_V) channels are ubiquitously expressed and function as Ca²⁺ conducting pores in the plasma membrane¹. On the basis of their voltage activation properties, the voltage-gated Ca²⁺ channels can be further divided into two broad groups: the low (T-type) and high (L, N, P, Q and R-type) threshold-activated channels.². Ca_V channels are heteromultimers composed of four independently encoded proteins, the pore-forming α1 subunit, which triggers Ca²⁺ flow across the membrane, and the auxiliary subunits α2δ, γ, and β³.

Ca_Vγ subunits inhibit Ca_V channel activity and modulate its activation and inactivation kinetics. Ca_Vγ subunits have little effect on Ca_V channel trafficking⁴. The γ subunit is an integral membrane protein. The γ subunit family consists of at least 8 members, which share a number of common structural features. Each member is predicted to possess four transmembrane domains, with intracellular N- and C-termini. The first extracellular loop contains a highly conserved N-glycosylation site and a pair of conserved cysteine residues⁵.

The Ca_Vγ5 subunit is highly expressed in the liver, kidney, heart, lung, skeletal muscles, and, with a lower abundance, in testes⁵. The close association of epilepsy and ataxia with mutations in other neuronal voltage-dependent Ca²⁺ channels suggests these are potential candidate phenotypes for defects in the Ca_Vγ5 (CACNG5) gene⁶.