Voltage-gated sodium channels

Voltage-gated sodium channels (VGSCs; pronounced: Vol-tage-gated so-dium chan-nels) are a class of transmembrane proteins that are responsible for the generation and propagation of action potentials in excitable cells such as neurons and muscle cells.

Etymology

The term "voltage-gated" refers to the mechanism by which these channels open and close in response to changes in the membrane potential. "Sodium" refers to the type of ions that these channels selectively allow to pass through the cell membrane.

Structure

Voltage-gated sodium channels are composed of a large α subunit that forms the channel pore and one or two smaller β subunits that have regulatory functions. The α subunit has four homologous domains (I-IV), each containing six transmembrane segments (S1-S6). The S4 segment in each domain contains positively charged residues that are involved in voltage sensing.

Function

Voltage-gated sodium channels play a key role in the initiation and propagation of action potentials. They are responsible for the rapid depolarization phase of the action potential, which results in the influx of sodium ions into the cell and the generation of an electrical signal.

Clinical significance

Mutations in the genes encoding voltage-gated sodium channels can lead to a variety of neurological disorders, including epilepsy, migraine, neuropathic pain, and cardiac arrhythmias. Several drugs that target these channels, such as local anesthetics, antiarrhythmic drugs, and antiepileptic drugs, are used in the treatment of these conditions.

Related terms

• Ion channel
• Potassium channel
• Calcium channel
• Action potential
• Neuron
• Muscle cell
• Membrane potential
• Transmembrane protein

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