Identification of a novel gill-specific calpain from rainbow trout (Oncorhynchus mykiss)

Abstract

Calpains are calcium-dependent neutral proteases responsible for many cellular functions. The two forms of calpain ubiquitously expressed in mammalian tissues are known as mu-calpain and m-calpain. We report here the identification of a novel calpain that is similar to but distinct from the mu- and m-calpains in rainbow trout. The cDNA of the novel gene is 2623 bp in length with a single open reading frame. The predicted protein (676 amino acids) contains the conserved calpain characteristic domains that include: domain I (pro peptide), II (cysteine catalytic site), III (electrostatic switch), and IV (calmodulin-like) with five Ca(2+)-binding EF hands. Northern blot and RT-PCR analyses demonstrated that the novel calpain gene is predominantly expressed in rainbow trout gills. Comparison of the novel protein with the ubiquitously expressed calpains and several mammalian tissue-specific calpains revealed that the novel calpain is an orthologue of the mammalian digestive tract specific calpain (calpain 9).

Phylogenetic Analysis and Taste Cell Expression of Calpain 9 in Catfish (<i>Ictalurus punctatus</i>)

“…In this report, we described the isolation of a tissue-specific calpain cDNA out of a catfish barbell epithelium cDNA library. Calpains have been reported in other non-mammalian species including CAPN1 & CAPN2 in carp muscle [25], those in trout muscle [26] and gill-specific calpain of rainbow trout [27]. The calpain reported on here encodes a 687 amino acid protein with a predicted molecular weight of 78,345 Da.…”

“…Salem et al showed that rainbow trout gill-specific calpain, closely related to calpain 9, was not expressed in the small intestine. Different detecting probes used in the northern blot analysis may explain this difference [27].…”

Characterization of rainbow trout gonad, brain and gill deep cDNA repertoires using a Roche 454-Titanium sequencing approach

“…As expected, several of these genes are known to be specifically or predominantly expressed in the gills (Table 6). Included in the gill-specific genes is a new calpain, which was reported to be expressed in the trout gill by Salem et al (2006). Additionally, we identified several ion transporters such as Na/K-ATPaseα1a, which was previously shown to be overexpressed in gill tissue by Richards et al (Richards et al, 2003).…”