Calcium channel, voltage-dependent, L type, alpha 1C subunit

Calcium channel, voltage-dependent, L type, alpha 1C subunit (CACNA1C) is a protein that in humans is encoded by the CACNA1C gene. This subunit forms part of the L-type calcium channel complex, which plays a critical role in electrophysiological processes in cardiac muscle, smooth muscle, and neurons. The L-type channels are distinguished by their long-lasting current and sensitivity to dihydropyridines, and they are crucial for the regulation of muscle contraction, neurotransmitter release, and gene expression.

Structure

The CACNA1C protein is a major component of the L-type calcium channel, which consists of several subunits: the alpha-1C subunit, which forms the pore through which calcium ions pass; the beta subunit; the alpha-2/delta subunit; and sometimes a gamma subunit. The alpha-1C subunit is responsible for the channel's voltage-dependent activation and drug sensitivity. It is composed of four homologous domains, each containing six transmembrane segments, with a pore-forming loop between segments 5 and 6.

Function

L-type calcium channels are activated by depolarization of the cell membrane, allowing calcium ions to enter the cell. This influx of calcium ions triggers various cellular processes, including muscle contraction in the heart and smooth muscle, hormone secretion, and synaptic transmission in neurons. In the heart, the influx of calcium ions during the action potential leads to the contraction of cardiac muscle cells, a process known as excitation-contraction coupling.

Clinical Significance

Mutations in the CACNA1C gene have been associated with several cardiovascular diseases, including Timothy syndrome, a rare multisystem disorder characterized by cardiac arrhythmias, webbing of fingers and toes, and developmental delays. Additionally, variations in this gene have been linked to psychiatric disorders such as bipolar disorder, schizophrenia, and major depressive disorder, highlighting the importance of calcium signaling in both the cardiovascular and nervous systems.

Pharmacology

L-type calcium channels are the target of various pharmacological agents, including dihydropyridines (e.g., nifedipine), which act as channel blockers. These medications are used to treat hypertension, angina pectoris, and certain types of arrhythmias. By inhibiting the influx of calcium ions, these drugs lead to the relaxation of smooth muscle cells in the blood vessels, reducing blood pressure and cardiac workload.

Research Directions

Research on the CACNA1C subunit continues to explore its role in disease and its potential as a therapeutic target. Studies are investigating the mechanisms by which mutations in the CACNA1C gene contribute to disease phenotypes and how modulation of L-type calcium channels can be used to treat various cardiovascular and psychiatric conditions.

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