Voltage-dependent calcium channels

Voltage-dependent calcium channels (VDCCs) are a group of voltage-gated ion channels found in the membrane of excitable cells (e.g., muscle, glial cells, neurons, etc.) with a permeability to the calcium ion Ca2+. These channels are slightly permeable to sodium ions, so they are also often referred to as Ca2+-Na+ channels, but their permeability to calcium is about 1000-fold greater than to sodium under normal physiological conditions.

Structure

VDCCs are formed as a complex of several different subunits: α1, α2δ, β1-4 and γ. The α1 subunit forms the ion conduction pathway, while associated subunits have several functions including the regulation of gating and ion selectivity. The α1 subunit forms the pore through which ions pass into the cell. The α1 subunit is composed of four homologous domains (I, II, III, IV), each containing six transmembrane segments (S1 to S6) for a total of 24 transmembrane segments.

Function

The opening and closing of the calcium channels are regulated by the electrical membrane potential, calcium concentration, and second messengers. VDCCs are involved in calcium signaling, which is important for several functions such as muscle contraction, neurotransmitter release, gene expression, and cell death.

Types

There are several types of VDCCs, each with distinct properties, distribution, and pharmacology. These include L-type calcium channels, P/Q-type calcium channels, N-type calcium channels, R-type calcium channels, and T-type calcium channels.

Clinical significance

VDCCs are involved in several diseases such as hypertension, cardiac arrhythmia, and neuropathic pain. They are also the target of several drugs used to treat these conditions.

See also

• Ion channel
• Calcium channel blocker
• Calcium signaling