Regulation of endometrial proliferation by the PGRMC family

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Project Summary/Abstract Progesterone receptor membrane component (PGRMC) 1 and PGRMC2 are thought to mediate progesterone actions. Our lab recently floxed the murine Pgrmc1 and Pgrmc2 genes in an effort to evaluate the function of these genes in the context of female fertility. Mutagenesis studies using Pgr-Cre mice revealed that Pgrmc1 and Pgrmc2 are essential for female fertility in that conditional ablation of each gene results in subfertility that progresses to premature reproductive senescence. Despite being a purported progesterone receptor, endometrial PGRMC1 expression is actually highest during the proliferative, estradiol (E2)-dominated phase of the menstrual cycle in humans and primates. The evolutionary origin of the PGRMC family predates the appearance of sterols as signaling molecules by at least 300 million years. As such, it is now becoming clear that PGRMCs have both progesterone-dependent and progesterone-independent functions. An evaluation of estrogenic responses in Pgrmc1d/d, Pgrmc2d/d, and Pgrmc1/2d/d mice revealed that PGRMC proteins are fundamentally required for E2-induced endometrial epithelial cell proliferation. Furthermore, we determined that PGRMC1 expression is elevated in human endometrial cancer. Consistent with these findings, human endometrial xenograft tumors derived from PGRMC1 over-expressing cells grow faster and are more resistant to chemotherapy treatment. Recent proteomic efforts in our lab have established that PGRMC1 interacts with three principal groups of proteins, and these include glycolytic enzymes, RNA-binding proteins and proteins involved in the initiation of translation. Estrogen is known to induce an endometrial Warburg-like glycolytic effect. Our central hypothesis is that PGRMC family members help coordinate E2-induced endometrial cell proliferation through their interactions with RNA-binding proteins and by establishing a Warburg-like aerobic glycolytic state to ensure that sufficient anabolic carbon-based building materials are available for proliferation and expansion of the tissue during the proliferative phase of the menstrual/estrous cycle. A linked component of this hypothesis is that PGRMC family members regulate mRNA processing that favors Warburg-like glycolysis. Through the use of proteomics, primary cell cultures, mouse models designed for evaluating endometrial epithelial cell proliferation in vivo, development of a novel transgenic mouse, and RNA-seq/CLIP-seq analysis, this hypothesis will be tested in the following Specific Aims: 1) evaluate the consequences of PGRMC1 over-expression on female fertility and development of endometrial hyperplasia and cancer; 2) demonstrate that PGRMC1 contributes to E2-induced proliferation by establishing a Warburg-like glycolytic effect in endometrial epithelial cells; and 3) demonstrate that PGRMC1 mediates at least some of the proliferative actions of E2 in endometrial epithelial cells through its interactions with RNA-binding proteins that coordinate post-transcriptional mRNA processing and translocation to the polyribosome. The outcome of these mechanistic studies will provide novel information about the molecular details of PGRMC1 functions that may be useful in the development of countermeasures that could reduce the prevalence and/or severity of E2-driven endometrial diseases.