Submitted to: Comparative Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/14/2004
Publication Date: 6/1/2005
Citation: Salem, M., Nath, J., Rexroad III, C.E., Killefer, J., Yao, J. 2005. Identification and molecular characterization of the rainbow trout calpains (capn1 and capn2)their expression in muscle wasting during starvation. Comparative Biochemistry and Physiology 140:63-71. Interpretive Summary: The genetic improvement of species for production efficiency is facilitated by identification of genes controlling traits of interest. Calpains are intracellular proteins involved in many important cellular functions and have been identified as candidate genes potentially affecting carcass quality traits. To understand the role of these genes in protein catabolism, we characterized their functions during muscle wasting resulting from starvation. This information has aided scientists in our understating of protein catabolism in fishes at the molecular level.
Technical Abstract: Calpains are intracellular proteases involved in many important cellular functions that are regulated by calcium. Among these functions is muscle proteolysis both ante- and post- mortem. Here we describe the identification and molecular characterization of the ubiquitously expressed Capn1 and Capn2 catalytic subunits of the µ- and m-calpains, respectively. The amino acid composition of Capn1 revealed 704 residues with a calculated molecular weigh 79.9 KDa. It showed 66% and 85% sequence identity with mouse and zebrafish Capn1, respectively. The amino acid composition of Capn2 revealed 701 residues with a calculated molecular weigh 78.2 KDa. It showed 64% sequence identity with both mouse and chicken Capn2. The two isozymes of the rainbow trout showed the characteristic domains: I (pro peptide), II (cysteine catalytic site), III ('electrostatic switch'), and IV (calmodulin-like calcium binding sites) which binds Ca2+ at several EF hands. Calpains have been hypothesized to play a role in skeletal muscle protein degradation. Because starvation has previously been shown to induce muscle wasting, the working hypothesis of this study was that starvation could influence regulation of the calpain system in muscle. Starvation of rainbow trout fingerlings (9-13 cm) for 35 days stimulated up-regulation of Capn2 expression (P<0.0001) but not Capn1 as measured by semi- quantitative RT-PCR. This suggests a potential role of m-calpain in protein mobilization for the purpose of muscle fuelling under fasting condition.