Insertion of the full-length calcium channel α1S subunit into triads of skeletal muscle in vitro

A full-length and a C-terminally truncated form of the calcium channel als subunit can be isolated from skeletal muscle. Here we studied whether full-length alpha(1S) is functionally incorporated into the skeletal muscle excitation-contraction coupling apparatus. A fusion protein of als with the green fluorescent protein attached to its C-terminus (alpha(1S)-GFP) or alpha(1S) and GFP separately (alpha(1S)+GFP) were expressed in dysgenic myotubes, which lack endogenous als. Full-length alpha(1S)-GFP was targeted into triad junctions and restored calcium currents and excitation-contraction coupling. GFP remained colocalized with als, indicating that intact alpha(1S)-GFP was inserted into triads and that the C-terminus remained associated with the excitation-contraction coupling apparatus. (C) 2000 Federation of European Biochemical Societies.