Co-Localization and Interaction of Pax5 with Iba1 in Brain of Mice.

The Pax5, a B-cell-Specific Activator Protein (BSAP) and redox-sensitive transcription factor, is expressed in the immune-privileged brain, B-lymphocytes, lymph nodes and spleen. PAX5-mediated immune pathway has also been described in the progression of Glioblastoma multiforme. However, the status of Pax5 and its role in brain immunity are not yet elucidated. In silico analysis of Pax5 interacting proteins predicts its interaction with proteins of cell proliferation, differentiation of hematopoietic cells, neurogenesis and several cell signalling pathways. Promoter analysis shows multiple binding sites for Pax5 in promoter of ionized calcium-binding adapter molecule 1 (Iba1). Like Iba1, Pax5 is also associated with inflammatory and immune response, activation of leukocyte and remodelling of actin cytoskeleton. Therefore, localization and interaction of Pax5 with Iba1 in brain of mice were studied using Chromatin Immunoprecipitation (ChIP), Co-Immunoprecipitation (Co-IP) and Immuno-fluorescence assay. The Pax5- and Iba1-positive cells were observed in cerebral cortex, cerebellum, olfactory bulb, hippocampus, and ventricles of brain. The co-localization of Pax5 and Iba1 was evident in microglia in almost all evaluated regions of brain. In some regions, Pax5- and Iba1-positive were distinctly compartmentalized. The Pax5a/b interacts with Iba1 and binds to its regulatory sequences. Results indicate Pax5-associated activities of Iba1 in microglia in brain of mice.