Spatial targeting of the prostaglandin receptor EP2 to very early endosomes co-ordinates PGE2-mediated cAMP signaling in decidualizing human endometrium

Summary Decidualization denotes the differentiation of endometrial stromal cells into specialized decidual cells, essential for embryo implantation and pregnancy. The process requires coordinated activation of both progesterone and cAMP signaling pathways, which converge on downstream transcription factors. PGE2 and relaxin, acting respectively through their Gαs-coupled GPCRs EP2 and RXFP1, are putative candidates responsible for generating cAMP in differentiating stromal cells. Here, we show that PGE2 is less efficacious than relaxin in elevating intracellular cAMP levels in primary stromal cells but more effective at driving the expression of canonical decidual genes. Both PGE2- and relaxin-induced cAMP generation involves receptor internalization, but EP2 is endocytosed into very early endosomes (VEEs). Perturbation of the VEE machinery dysregulates PGE2-dependent cAMP profiles and disrupts key decidual signaling pathways, resulting in a disordered differentiation response. We demonstrate that the spatial location of EP2 is essential for coordinated activation of the downstream signaling cascades that govern decidualization.