Pituitary adenylate cyclase-activating polypeptide (PACAP) type 1 receptor (PAC1R) co-localizes with activity-dependent neuroprotective protein (ADNP) in the mouse brains

Activity-dependent neurotrophic protein (ADNP) was discovered as a novel response gene for vasoactive intestinal polypeptide. We have reported that PACAP strongly stimulated ADNP mRNA expression in a mouse neuron/glial cell culture; however, the distribution of ADNP in the brain and its possible co-expression with the PACAP receptor (PAC1R) are unknown. In this study, the specificity of the ADNP antibody used in subsequent immunohistochemistry experiments was first characterized. Mouse brain lysates were analysed by Western blot, with an ADNP-immunopositive signal corresponding to the expected molecular weight of ADNP detected as a 124 kDa band. Immunohistochemical staining to identify ADNP and PAC1R immunoreactivity in mouse brain was then performed. ADNP immunoreactive cells were observed in the cerebral cortex, cerebellum, hippocampus, and medial septum of brain slices. ADNP-immunoreactive cells in the cerebral cortex were multi-polar-shaped and co-immunostained with the astrocyte marker, glial fibrillary acidic protein (GFAP). ADNP-immunoreactive cells in the cerebellum were found to surround Purkinje cells and showed GFAP immunoreactivity. On the other hand, ADNP-immunoreactive cells in the hippocampus and septum were round in shape and co-immunostained with the neuron marker, neuron-specific enorase. All of the ADNP-immunopositive cells co-localized with PAC1R immunoreactivity. These observations suggest that ADNP is expressed in both astrocytes and neurons, and that ADNP expression may be regulated by PACAP.