L-Type

L-Type Calcium Channel

The L-type calcium channel is a type of voltage-dependent calcium channel. Like all of the voltage-dependent calcium channels, the L-type calcium channel is activated by the depolarization of the neuronal membrane. The L-type calcium channel is responsible for the excitation-contraction coupling of skeletal, smooth, cardiac, and soft muscle. It may also be involved in exocytosis, hormone secretion, and gene expression.

Structure

L-type calcium channels are composed of five subunits. The alpha-1 subunit forms the ion pore while the associated subunits, beta-2, alpha-2/delta and gamma are located extracellularly, intracellularly, and on the plasma membrane, respectively.

Function

The main function of the L-type calcium channel is to allow for the influx of Ca2+ ions into the cell, which leads to muscle contraction. This is especially important in cardiac muscle, where it contributes to the plateau phase of the action potential.

Clinical significance

Mutations in the genes encoding the subunits of the L-type calcium channel can lead to various disorders. For example, mutations in the CACNA1C gene, which encodes the alpha-1C subunit of the L-type calcium channel, can lead to Timothy syndrome, a rare disorder characterized by cardiac arrhythmias, webbing of fingers and toes, and developmental delay.

See also

• Voltage-gated ion channel
• Calcium channel blocker
• Timothy syndrome

References

L-Type Resources
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