Nicotinic acetylcholine receptors (nAcChoRs) of skeletal muscle are heterosubunit ligand-gated channels that mediate signal transmission from motor nerves to muscle. While cloning murine nAcChoR subunits, to gain an insight into the receptor diversity across species, we detected two forms of γ subunits in the myogenic C2C12 cell line. Both forms are functional when expressed in Xenopus oocytes. One γ subunit [long γ (γ(i))] was almost identical to that previously cloned in the murine BC3H-1 tumor cell line. The second form of γ subunit [short γ (γ(s)) lacked 156 bp (52 amino acids) in the extracellular N terminus, adjoining the hydrophobic segment M1, which corresponds to the fifth exon of the γ-subunit gene. The two forms of γ subunit coexist during myogenesis in vitro and in 17-day embryonic and denervated adult muscle fibers in vivo. However, the γ(s) variant was the only form of γ subunit in newborn muscle. In dissociated muscle fibers of newborn mice, AcCho-evoked channel openings were more prolonged when compared with C2C12 myotubes or denervated adult muscle fibers. The γ(s) subunit may, thus, contribute to the structural and functional diversity of nAcChoRs in muscle cells.
|Number of pages||5|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|Publication status||Published - Mar 28 1995|
- γ-subunit variant
- channel duration
- disulfide-bonded loop
ASJC Scopus subject areas