hCG activates Epac-Erk1/2 signaling regulating Progesterone Receptor expression and function in human endometrial stromal cells.

Study Question: How does hCG signal in human endometrial stromal cells (ESCs) and what is its role in regulating ESC function?

Summary Answer: hCG signaling in ESCs activates the extracellular signal-regulated protein kinases 1 and 2 (Erk1/2) pathway through exchange protein activated by cyclic AMP (cAMP) (Epac) and transiently increases progesterone receptor (PR) transcript and protein expression and its transcriptional function.

What Is Known Already: hCG is one of the earliest embryo-derived secreted signals in the endometrium, which abundantly expresses LH/hCG receptors. hCG signals through cAMP/protein kinase A (PKA) in gonadal cells, but in endometrial epithelial cells, hCG induces Erk1/2 activation independent of the cAMP/PKA pathway.