Molecular cloning, phylogenetic analysis and expression of a MAPEG superfamily gene from the pufferfish Takifugu obscurus

The microsomal glutathione S-transferases (MGSTs) of membrane-associated proteins in eicosanoid and glutathione metabolism (MAPEG) superfamily play an important role in xenobiotics detoxification. Compared to mammals, there is limited information on MAPEGS from fish. We cloned a full length of cDNA sequence of a MGST gene from the river pufferfish (Takifugu obscurus), studied its phylogenetic relationship, and measured its expression in different tissues and in liver of fish exposed to cadmium. Phylogenetic analysis revealed that the identified gene encoded for MGST3. Liver showed the highest expression of MGST3 transcripts. When MSGT expression was compared with the expression of other GSTs (GST-Alpha, GST-Mu and GST-Theta), a similar pattern of highest expression was observed in the liver. Upon Cd exposure (5 ppm) for 96 h, the highest expression of MGST was observed at 24 h. GST-Mu also showed highest expression at 24 h. These findings indicate that MGSTs may be playing a role in detoxification of xenobiotics or free radicals generated by Cd-induced oxidative stress in fish.