Expression of kynurenine aminotransferase-2 in different mouse brain-derived cells: A comprehensive study in cell...

The kynurenine pathway is the principal route of tryptophan metabolism in the brain, generating several neuroactive metabolites, including kynurenic acid (KYNA). KYNA functions as both a neuromodulator and a neuroprotective compound, and its dysregulation has been associated with numerous neurological and psychiatric disorders. Kynurenine aminotransferase-2 (KAT-2) is the key enzyme responsible for KYNA synthesis, yet its precise cellular localization in the mouse brain remains insufficiently characterized. In this study, we systematically compared KAT-2 expression in primary astrocytic, microglial, and neuronal cultures derived from mouse brain, complemented by in situ immunolabeling of brain sections. Immunocytochemistry combined with quantitative colocalization analysis revealed that KAT-2 is expressed in all three major brain cell types, with significant overlap with cell type-specific markers. Furthermore, KAT-2 immunoreactivity was largely restricted to the soma, showing a perinuclear distribution in glial cells and partial extension into dendritic compartments in neurons. These findings provide the first parallel characterization of KAT-2 distribution across astrocytes, microglia, and neurons in the mouse brain. Overall, our results indicate that KAT-2 is widely expressed in neural cells, a finding that supports the hypothesis that KAT-2 contributes broadly to kynurenine metabolism. Taken together, our findings provide a foundation for future studies aimed at defining the cell type-specific functional roles of KAT-2.