Cloning, Distribution, and Colocalization of MNAR/PELP1 with Glucocorticoid Receptors in Primate and Nonprimate Brain

MNAR/PELP1 (see text) is a newly identified scaffold protein/coactivator initially thought to modulate nongenomic and genomic actions of the estrogen receptor; however, it has been recently shown to interact with multiple steroid receptors, including androgen and glucocorticoid receptors. In the present study, we cloned the monkey MNAR/PELP1 gene, deduced its domain structure, examined its localization pattern and colocalization with glucocorticoid receptor in monkey brain, and determined its subcellular localization. PCR-based cloning of MNAR/PELP1 from monkey brain produced a transcript of ∼3.4 kb which showed high homology to the human and rat MNAR/PELP1 gene. Domain analysis showed that all the key steroid-receptor-interacting (LXXLL) domains, SH3-interacting (PXXP) domains and several C-terminal glutamic-acid-rich clusters, as well as various kinase domains are conserved in the monkey MNAR/PELP1 gene. Anatomical mapping of MNAR/PELP1 immunoreactivity in several regions of the monkey brain showed a similar pattern of MNAR/PELP1 distribution as previously observed in rat and mouse brains. MNAR/PELP1 also showed an absolute colocalization with glucocorticoid receptors in both primate and nonprimate brain, including those regions of the brain, where other steroid receptors are not significantly expressed, such as hippocampus, striatum, and thalamus – suggesting that MNAR/PELP1 may modulate glucocorticoid actions in the brain. Finally, ultrastructural electron microscopic studies showed that MNAR/PELP1-reactive gold particles are located within nucleus, cytoplasm, dendritic/synaptic terminals, and astrocytic processes. As a whole, the studies demonstrate that MNAR/PELP1 is expressed and colocalizes with glucocorticoid receptors in monkey and rat brains and may have multiple cellular functions based on its subcellular localizations.