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

Abstract

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.

PELP1—A novel estrogen receptor-interacting protein

“…A similar nuclear and cytoplasm localization of PELP1 has been demonstrated in neurons by electron microscopy (Figure 3) (Khan et al, 2006). Localization of PELP1 in dendritic shafts and at synaptic sites has also been described (Figure 3) (Khan et al, 2006), which is consistent with synaptic and dendritic localization of ER-α (Milner et al, 2001). The nuclear localization of PELP1 is consistent with its purported role in mediating genomic signaling by estrogen, while its cytoplasmic localization suggests a potential role in mediating fast, nongenomic signaling by estrogen.…”

“…In hormonally responsive tissues, PELP1 has been shown to predominantly reside in the nucleus, but localization in the cytoplasm is also observed, albeit to a lesser degree than nuclear localization (Vadlamudi et al, 2001;Khan et al, 2005;Vadlamudi et al, 2005a;Khan et al, 2006). A similar nuclear and cytoplasm localization of PELP1 has been demonstrated in neurons by electron microscopy (Figure 3) (Khan et al, 2006).…”

“…Subsequent work by our laboratories led to the cloning of rat and monkey PELP1, which display 86% and 98% homology to the human PELP1 gene, respectively, and which were shown to contain the same protein domain motifs as human PELP1, e.g. glutamic acid clusters, LXXLL domain motifs, and PXXP domain motifs (Khan et al, 2005;Khan et al, 2006).…”

“…PELP1 contains a central consensus nuclear localization site and exhibits both nuclear and cytoplasmic localization in a variety of cells in the body (Vadlamudi et al, 2001;Nair et al, 2004;Khan et al, 2005;Khan et al, 2006). In hormonally responsive tissues, PELP1 has been shown to predominantly reside in the nucleus, but localization in the cytoplasm is also observed, albeit to a lesser degree than nuclear localization (Vadlamudi et al, 2001;Khan et al, 2005;Vadlamudi et al, 2005a;Khan et al, 2006).…”

“…In hormonally responsive tissues, PELP1 has been shown to predominantly reside in the nucleus, but localization in the cytoplasm is also observed, albeit to a lesser degree than nuclear localization (Vadlamudi et al, 2001;Khan et al, 2005;Vadlamudi et al, 2005a;Khan et al, 2006). A similar nuclear and cytoplasm localization of PELP1 has been demonstrated in neurons by electron microscopy (Figure 3) (Khan et al, 2006). Localization of PELP1 in dendritic shafts and at synaptic sites has also been described (Figure 3) (Khan et al, 2006), which is consistent with synaptic and dendritic localization of ER-α (Milner et al, 2001).…”