Pore-forming, alpha-1C subunit of the voltage-gated calcium channel that gives rise to L-type calcium currents. Mediates influx of calcium ions into the cytoplasm, and thereby triggers calcium release from the sarcoplasm. Plays an important role in excitation-contraction coupling in the heart. Required for normal heart development and normal regulation of heart rhythm (By similarity). Required for normal contraction of smooth muscle cells in blood vessels and in the intestine. Essential for normal blood pressure regulation via its role in the contraction of arterial smooth muscle cells (By similarity). Long-lasting (L-type) calcium channels belong to the 'high-voltage activated' (HVA) group (By similarity). Inhibited by dihydropyridines (DHP), such as isradipine. Channel activity is regulated by Ca(2+) and calmodulin. Component of a calcium channel complex consisting of a pore-forming alpha subunit (CACNA1C) and ancillary beta, gamma and delta subunits. The channel complex contains alpha, beta, gamma and delta subunits in a 1:1:1:1 ratio, i.e. it contains only one of each type of subunit. CACNA1C channel activity is modulated by ancillary subunits, such as CACNB2, CACNB3, CACNA2D1 and CACNA2D4. The interaction between RRAD and CACNB2 promotes the expression of CACNA1C at the cell membrane. Each of the four internal repeats contains five hydrophobic transmembrane segments (S1, S2, S3, S5, S6) and one positively charged transmembrane segment (S4). S4 segments probably represent the voltage-sensor and are characterized by a series of positively charged amino acids at every third position. Binding of intracellular calcium through the EF-hand motif inhibits the opening of the channel. Phosphorylation by PKA activates the channel. Belongs to the calcium channel alpha-1 subunit (TC 1.A.1.11) family. CACNA1C subfamily.