Rat brain thioltransferase: Regional distribution, immunological characterization, and localization by fluorescent in situ hybridization

Thioltransferase (TTase) is a member of the family of thiol-disulfide oxido reductases that are involved in the maintenance of sulfhydryl homeostasis i n cells by catalyzing thiol-disulfide interchange reactions. One of the maj or consequences of oxidative stress in brain is the formation of protein-gl utathione mixed disulfides (through oxidation of protein thiols), which can be reversed by TTase during the recovery of brain from oxidative stress. W e therefore examined the presence of TTase in brain regions from rat. In th e rat, TTase activity in the whole brain was comparable with the correspond ing activity in liver, but significantly higher in hippocampus. The enzyme activity was significantly lower in striatum and cerebellum compared with a ctivity in whole brain. Rat brain TTase shared immunological similarity wit h the human red blood cell enzyme, but not with the pig liver enzyme. The c onstitutive expression of the mRNA to TTase was demonstrable by northern bl otting. Localization of the TTase mRNA in rat brain by fluorescent in situ hybridization showed the presence of high amounts of mRNA in the olfactory bulb, cortex, and hippocampus and its predominant localization in the neuro ns. TTase mRNA was also present in Purkinje cells in the cerebellum, in gia nt reticular neurons in the midbrain, and in the striatal and thalamic neur ons. This study demonstrates the constitutive presence of a functional TTas e system in brain and delineates the regional and cellular localization of the enzyme in rat brain.