Insertion of the full-length calcium channel alpha(1S) subunit into triadsof 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 exci tation-contraction coupling apparatus. A fusion protein of als with the gre en 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 tri ad junctions and restored calcium currents and excitation-contraction coupl ing. GFP remained colocalized with als, indicating that intact alpha(1S)-GF P was inserted into triads and that the C-terminus remained associated with the excitation-contraction coupling apparatus. (C) 2000 Federation of Euro pean Biochemical Societies.