Stable and functional expression of the calcium channel α1 subunit from smooth muscle in somatic cell lines

Voltage-activated calcium channels are membrane spanning proteins that allow the controlled entry of Ca²⁺ into the cytoplasm of cells. The principal channel forming subunit of an L-type calcium channel is the α1 subunit. Transfection of Chinese hamster ovary (CHO) cells with complementary DNA encoding the calcium channel al subunit from smooth muscle led to the expression of functional calcium channels which bind calcium channel blockers and show the voltage-dependent activation and slow inactivation and unitary current conductance characteristic of calcium channels in smooth muscle. The currents mediated by these channels are sensitive towards dihydropyridine-type blockers and agonists indicating that the calcium channel blocker receptor sites were present in functional form. The smooth muscle α1 subunit cDNA alone is sufficient for stable expression of functional calcium channels with the expected kinetic and pharmacological properties in mammalian somatic cells.