cDNA Characterization and Expression of Selenium-Dependent Isoforms in the Crayfish under High Temperature and Hypoxia.

Glutathione peroxidase 3 (GPx3) is the only extracellular selenoprotein (Sel) that enzymatically reduces HO to HO and O. Two GPx3 () cDNAs were characterized from crayfish . The nerve cord isoform encodes for a preprotein containing an N-terminal signal peptide of 32 amino acid residues, with the mature Sel region of 192 residues and a dispensable phosphorylation domain of 36 residues. In contrast, the pereiopods codes for a precursor protein with 19 residues in the N-terminal signal peptide, then the mature 184 amino acid residues protein and finally a Pro-rich peptide of 42 residues. are expressed in cerebral ganglia, pereiopods and nerve cord. is expressed mainly in cerebral ganglia, antennulae and nerve cord, while was detected mainly in pereiopods. expression increases with high temperature and hypoxia; meanwhile, is not affected. We report the presence and differential expression of isoforms in crustacean tissues in normal conditions and under stress for high temperature and hypoxia. The two isoforms are tissue specific and condition specific, which could indicate an important role of in the central nervous system and in exposed tissues, both involved in different responses to environmental stressors.