Voltage-dependent calcium channel, gamma-4 subunit (IPR005423)

Short name: VDCC_g4su

Overlapping homologous superfamilies


Family relationships


Ca2+ ions are unique in that they not only carry charge but they are also the most widely used of diffusible second messengers. Voltage-dependent Ca2+ channels (VDCC) are a family of molecules that allow cells to couple electrical activity to intracellular Ca2+ signalling. The opening and closing of these channels by depolarizing stimuli, such as action potentials, allows Ca2+ ions to enter neurons down a steep electrochemical gradient, producing transient intracellular Ca2+ signals. Many of the processes that occur in neurons, including transmitter release, gene transcription and metabolism are controlled by Ca2+ influx occurring simultaneously at different cellular locales. The pore is formed by the alpha-1 subunit which incorporates the conduction pore, the voltage sensor and gating apparatus, and the known sites of channel regulation by second messengers, drugs, and toxins [PMID: 14657414]. The activity of this pore is modulated by four tightly-coupled subunits: an intracellular beta subunit; a transmembrane gamma subunit; and a disulphide-linked complex of alpha-2 and delta subunits, which are proteolytically cleaved from the same gene product. Properties of the protein including gating voltage-dependence, G protein modulation and kinase susceptibility can be influenced by these subunits.

Voltage-gated calcium 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, the voltage-gated calcium classes can be further divided into two broad groups: the low (T-type) and high (L, N, P, Q and R-type) threshold-activated channels.

The voltage-dependent calcium channel gamma (VDCCG) subunit family consists of at least 8 members, which share a number of common structural features [PMID: 11170751]. Each member is predicted to possess 4 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 residues. The C-terminal 7 residues of VDCCG-2, -3, -4 and -8 are also conserved and contain a consensus site for phosphorylation by cAMP and cGMP-dependent protein kinases, and a target site for binding by PDZ domain proteins [PMID: 11170751].

The VDCCG-4 subunit is predominantly expressed in neuronal tissue, although there is some evidence for expression in lung and prostate [PMID: 11170751, PMID: 10734232]. The modulatory properties of the subunit have been investigated using heterologous expression systems. Coexpression of the VDCGG-4 subunit with P/Q-type channels shifts the steady-state inactivation curve of these channels to more hyperpolarised potentials [PMID: 10734232, PMID: 11313431].

GO terms

Biological Process

GO:0070588 calcium ion transmembrane transport

Molecular Function

GO:0005245 voltage-gated calcium channel activity

Cellular Component

GO:0005891 voltage-gated calcium channel complex

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.