Induction of calcium currents by the expression of the α1-subunit of the dihydropyridine receptor from skeletal muscle

Abstract

THE dihydropyridine (DHP) receptor purified from skeletal muscle comprises five protein subunits (α1, α2, β, γ and δ) and produces Ca2+ currents that are blocked by DHPs1. Cloning of the α1- and α2-subunits2,3, the former affinity-labelled by DHP, has shown that the α1-subunit is expressed in skeletal muscle alone, whereas the α2- and δ-subunits are also expressed in othertissues2,4,5. Although the transient expression of the α1-subunit in myoblasts from dysgenic mice (but not in oocytes) has been demonstrated6, the use of these expression systems to determine the function of the α1-subunit is complicated by the presence of endogenous Ca2+ currents7,8, which may reflect the constitutive expression of proteins similar to the α2-, β-, γ- and/or γ-subunits. We therefore selected a cell line which has no Ca2+ currents or α2-subunit, and probably no γ-subunit for stable transformation with complementary DNA of the α1-subunit. The transformed cells express DHP-sensitive, voltage-gated Ca2+ channels, indicating that the minimum structure of these channels is at most an α1βγ complex and possibly an α1-subunit alone.