Calcium channels

Lee, Wooyong

Abstract

Calcium channels are ion channels formed by membrane spanning proteins that have a calciumselective pore. There are some types of calcium channels. One type is calcium channel whose gating is controlled by voltage in the cell membrane. The others are controlled by binding of ligands in membranes of intracellular organelles and plasma membranes. Calcium channels whose gating is controlled by voltage are called voltage-gated calcium channels(VGCC). VGCC's are present in all excitable cells, but also in many non-excitable cells. VGCC's are distinguished by differences in voltage dependence, kinetics, and sensitivity to a variety of blockers. One distinction is by the voltage amount to open the channel. Channels requiring smaller depolarizations are called low voltage activated(LVA) channels and channels requiring lager depolarizations are called high voltage activated(HVA) channels. More recently, VGCC's have been classified by their amino acid sequence identity. VGCC's are composed of several subunits. Among them, alpha1 subunit has the main function. It has voltage sensor and ionic selectivity. VGCC's are activated by voltage but also inactivated by voltage. Calcium entry can also inactivate some VGCC's. VGCC's play very important roles in the heart, skeletal muscle, neurons and are modulated by some mechanisms such as phosphorylation.