Identification and molecular characterization of the rainbow trout calpains (Capn1 and Capn2): their expression in muscle wasting during starvation.
Calpains are calcium regulated proteases involved in cellular functions that include muscle proteolysis both ante- and postmortem. Here, we describe the molecular characterization of the rainbow trout catalytic subunits of the mu- and m-calpains, respectively. The cDNA sequence for Capn1 encodes a protein of 704 amino acids with a calculated molecular mass of 79.9 kDa. The amino acid sequence shows 66% and 86% identity with the mouse and zebrafish Capn1, respectively. The Capn2 cDNA codes for a protein consisting of 701 amino acid residues with a calculated molecular mass of 78.2 kDa. The protein shows 65% amino acid sequence identity with the mouse and chicken Capn2. The two isozymes of rainbow trout have the characteristic domains: I (propeptide), II (cysteine catalytic site), III (electrostatic switch), and IV (contains five EF-hands). Because starvation induces muscle wasting, the hypothesis of this study was that starvation could affect regulation of the calpain system in muscle. Starvation of rainbow trout fingerlings (15-20 g) for 35 days stimulated the expression of Capn1 (2.2-fold increase, P < 0.01), Capn2 (6.0-fold increase, P < 0.01), and calpastatins (1.6-fold increase, P < 0.05) as measured by quantitative real-time RT-PCR. The mRNA changes led to a 1.23-fold increase in the calpain catalytic activity. The results suggest a potential role of calpains in protein mobilization as a source of energy under fasting condition.
Salem
Mohamed
M
Division of Animal and Veterinary Sciences, West Virginia University, Morgantown, WV 26506-6108, USA.
Nath
Joginder
J
Rexroad
Caird E
CE
Killefer
John
J
Yao
Jianbo
J
D000595:Amino Acid Sequence; D000818:Animals; D002154:Calpain / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009133:Muscular Atrophy / Q000201:enzymology*; D017686:Oncorhynchus mykiss / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013217:Starvation; D014018:Tissue Distribution
D018076:DNA, Complementary; D029941:Fish Proteins; D012333:RNA, Messenger; D002154:Calpain