Transcriptional up-regulation of disk abalone selenium dependent glutathione peroxidase by H(2)O(2) oxidative stress and Vibrio alginolyticus bacterial infection.
ABSTRACT Selenium dependent glutathione peroxidase (Se-GPx) belongs to the family of selenoprotein, which acts mainly as an antioxidant in the cellular defence system. We have identified Se-GPx full length cDNA from disk abalone (Haliotis discus discus) designated as AbSe-GPx. It has a characteristic codon at (223)TGA(225) that corresponds to selenocysteine (Sec) amino acid as U(75). The full length cDNA consists of 675 bp, an open reading frame encoding 225 amino acids. Sequence characterization revealed that AbSe-GPx contains a characteristic GPx signature motif 2 ((97)LGFPCNQF(104)), an active site motif ((183)WNFEKF(188)) and essential residues for the enzymatic function. Additionally, the eukaryotic selenocysteine insertion sequence (SECIS) is conserved in the 3' UTR. The AbSe-GPx amino acid sequence exhibited the highest level of identity (46%) with insect (Ixodes scapularis) GPx, and shares 41% with bivalve (Unio tumidus) Se-GPx. The RT-PCR analysis revealed that AbSe-GPx mRNA was expressed constitutively in gill, mantle, gonad, abductor muscle, digestive tract, and hemocytes in a tissue specific manner. AbSe-GPx mRNA expression was significantly up-regulated in gill and digestive tract tissues after H(2)O(2) injection and Vibrio alginolyticus infection. However, AbSe-GPx expression was not up-regulated after Aroclor 1,254 injection. These results indicate that AbSe-GPx mRNA is expressed at a basal level in abalone tissues, which can be up-regulated transcriptionally by H(2)O(2) oxidative stress and Vibrio alginolyticus infection. Therefore, AbSe-GPx may be involved in a protective role against H(2)O(2) oxidative stress and immune defence against bacterial infection.
Article: Selenium-dependent glutathione peroxidase gene expression during gonad development and its response to LPS and H₂O₂ challenge in Scylla paramamosain.[show abstract] [hide abstract]
ABSTRACT: A selenium-dependent glutathione peroxidase cDNA was obtained from green mud crab Scylla paramamosain (SpGPx) by homology PCR technique and rapid amplification of cDNA ends (RACE) methods. The 1135 bp full-length cDNA contains a 9 bp 5'-untranslated region (UTR), an open reading frame (ORF) of 564 bp encoded a deduced protein of 187 amino acids (aa), and a 562 bp 3'-UTR with a 100 bp conserved eukaryotic selenocysteine insertion sequence (SECIS). It involves a putative selenocysteine (Sec⁴⁰, or U⁴⁰) residue which is encoded by an opal codon, ¹²⁷TGA¹²⁹, and forms an active site with residues Q⁷⁴ and W¹⁴². Sequence characterization revealed that SpGPx contain a characteristic GPx signature motif 2 (⁶⁴LAFPCNQF⁷¹), an active site motif (¹⁵²WNFEKF¹⁵⁷), a potential N-glycosylation site (⁷⁶NTT⁷⁸), and two residues (R⁹⁰ and R¹⁶⁸) which contribute to the electrostatic architecture by directing the glutathione donor substrate. Multiple sequence alignment and phylogenetic analysis showed that SpGPx share a high level of identities and closer relationship with other selected invertebrate GPxs and vertebrate GPx1 and GPx2. Molecular modelling analysis results also supported these observations. Real time quantitative PCR analysis revealed that SpGPx was constitutively expressed in 10 selected tissues, and its expression level in gill and testis was higher than that in the other tissues (p < 0.05). The SpGPx expression increased and then declined during ovarian and testicular development implying thatnscrpits yowed that SpGPx might play an important role in gonad development by protecting them from oxidative stress. The expression of SpGPx mRNA was induced by lipopolysaccharide (LPS) and hydrogen peroxide (H₂O₂) in hepatopancreas and haemocytes. The results suggested that SpGPx was implicated in the immune response induced by LPS and H₂O₂.Fish & Shellfish Immunology 06/2012; 33(3):532-42. · 3.32 Impact Factor