Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCA211

Poster Communications

Characterization of the membrane progesterone receptor betta (mPRβ) using the Xenopus laevis oocyte model

N. Nader1, M. Dib1, R. Hodeify1, K. Machaca1

1. Research, Weill Cornell Medicine - Qatar, Doha, Doha, Qatar.

Membrane progesterone receptors (mPRs) are 7-transmembranes integral membrane proteins that belong to the progestin and AdipoQ receptor (PAQR) family. Upon progesterone (P4) binding, mPRs rapidly alter cell signaling via non-genomic modulation of intracellular signaling cascades, including cAMP, MAPK, and Ca2+ signals. Emerging physiological roles for mPRs have been documented in different tissues, including oocytes, testis, uterus, placenta, breast, brain and immune cells. This raises the profile of mPRs as potential therapeutic targets for different diseases; however, the immediate mechanisms of action downstream of mPRs remain in question. One of the best-studied models of P4-mPR non-genomic action is the activation of oocyte maturation in the Xenopus laevis specie. In this study, we used mPRβ overexpression in Chinese Hamster Ovary (CHO) cells and P4-dependent release of meiotic arrest in Xenopus oocytes to characterize mPRβ (PAQR8) structure and function. We show that mPRβ has an extracellular C-terminus and a cytosolic N-terminus, a topology that is opposite to the typical G-protein-coupled receptors (GPCRs). We further show through deletions of the N- or C-terminus domain that the N-terminal domain is essential for mPRβ signaling, whereas the C-terminal domain is crucial for mPRβ trafficking and plasma membrane residence. Since mPRβ shares sequence similarity with alkaline ceramidase, we initiated studies to test whether mPRβ in the oocytes has ceramidase activity. We used pharmacological and metabolomics approaches and showed that the ceramidase inhibitor, ceranib1, negatively regulates P4-induced oocyte maturation, whereas preliminary metabolomics data revealed changes in free fatty acids in response to P4 treatment. Taking together, these results supports the hypothesis that XmPR might possesses an intrinsic ceramidase activity. Collectively, our data provide new insights into the structure-function of mPRβ non-genomic P4-dependent signaling, that will pave the way to a more in depth studies to uncover fully its mechanisms of action.

Where applicable, experiments conform with Society ethical requirements