Localization and signaling of the prolactin receptor in the uterus of the common marmoset monkey

This study investigated the expression and signaling pathway of PRL and its receptor in the non-pregnant uterus of the common marmoset monkey. Immunoh istochemistry localized PRL expression to the stromal compartment of the en dometrium. Expression was minimal during the proliferative phase and was up -regulated during the mid to late secretory phase of the ovulatory cycle. I n situ hybridization and immunohistochemistry localized expression of the P RL receptor to the glandular epithelium of the endometrium. Similar to that of PRL, PRL receptor expression was minimal during the proliferative phase and was dramatically up-regulated during the secretory phase. The temporal pattern of PRL receptor gene expression in the marmoset uterus across the cycle was further confirmed by ribonuclease protection assay. The roles of Janus kinase-a (JAK2) and signal transducer and activator of transcription- 1 (STAT1) in the intracellular signaling pathway of PRL were also assessed in the mid to late secretory phase. JAK2/STAT1 proteins were localized in t he glandular epithelial compartment, and both proteins were temporally phos phorylated in response to PRL. Finally, the pattern of expression of the in terferon regulatory factor-1 (IRF-1) gene and the effect of PRL on transcri ption of IRF-1 were investigated during the mid to late secretory phase. IR F-1 expression in the marmoset uterus was encoded by a protein of 48 kDa an d was localized to the glandular epithelial compartment, as was observed fo r the PRL receptor and JAK2/STAT1 proteins. Moreover, incubation of mid to late secretory uterine tissue with PRL for 1 and 3 h resulted in 0.4 +/- 0. 2- and 2.4 +/- 0.5-fold (P < 0.05) inductions of the IRF-1 gene, respective ly. These studies confirm the expression of both PRL and its receptor in th e uterus of the marmoset monkey. Expression of both genes is upregulated du ring the mid to late secretory phase of the ovulatory cycle. PRL function i n the marmoset uterus is linked to the JAK/STAT signaling pathway, leading to the regulation of expression of PRL-responsive genes such as IRF-1. The site of expression of PRL, PRL receptors, and IRF-1 in the marmoset uterus suggest that PRL may influence glandular epithelial function and direct gen e transcription in these cells in a paracrine fashion.