Cloning and characterization of fiber type-specific ryanodine receptor isoforms in skeletal muscles of fish

• Published in: American Journal of Physiology: Cell Physiology 1998-08, Vol.275 (2), p.C401
• Main Authors: Franck, Jens P C, Morrissette, Jeffery, Keen, John E, Londraville, Richard L, Beamsley, Mark, Block, Barbara A
• Format: Article
• Language: English
• ISSN: 1522-1563

We have cloned a group of cDNAs that encodes the skeletal ryanodine receptor isoform (RyR1) of fish from a blue marlin extraocular muscle library. The cDNAs encode a protein of 5,081 amino acids with a calculated molecular mass of 576,302 Da. The deduced amino acid sequence shows strong sequence identity to previously characterized RyR1 isoforms. An RNA probe derived from a clone of the full-length marlin RyR1 isoform hybridizes to RNA preparations from extraocular muscle and slow-twitch skeletal muscle but not to RNA preparations from fast-twitch skeletal or cardiac muscle. We have also isolated a partial RyR clone from marlin and toadfish fast-twitch muscles that shares 80% sequence identity with the corresponding region of the full-length RyR1 isoform, and a RNA probe derived from this clone hybridizes to RNA preparations from fast-twitch muscle but not to slow-twitch muscle preparations. Western blot analysis of slow-twitch muscles in fish indicates the presence of only a single high-molecular-mass RyR protein corresponding to RyR1. [ H]ryanodine binding assays revealed the fish slow-twitch muscle RyR1 had a greater sensitivity for Ca than the fast-twitch muscle RyR1. The results indicate that, in fish muscle, fiber type-specific RyR1 isoforms are expressed and the two proteins are physiologically distinct.