Figure 1.

Signal transduction by voltage-gated Ca²⁺ channels. Ca²⁺ entering cells initiates numerous intracellular events, including contraction, secretion, synaptic transmission, enzyme regulation, protein phosphorylation/dephosphorylation, and gene transcription. (Inset) Subunit structure of voltage-gated Ca²⁺ channels. The five-subunit complex that forms high-voltage-activated Ca²⁺ channels is illustrated with a central pore-forming α1 subunit, a disulfide-linked glycoprotein dimer of α2 and δ subunits, an intracellular β subunit, and a transmembrane glycoprotein γ subunit (in some Ca²⁺ channel subtypes). As described in the text, this model is updated from the original description of the subunit structure of skeletal muscle Ca²⁺ channels. (Adapted from Takahashi et al. 1987).