Endocrine Abstracts

Polycystic ovary syndrome (PCOS) is characterised by aberrant luteinizing hormone (LH) secretion and action. A primary signalling pathway of LH receptor (LHR) to drive its steroidogenic actions is via its ability to activate Gas/cAMP. Both LHR internalization to the very early endosome (VEE) and negative regulation by the adaptor protein APPL1 play a key role in shaping LHR cAMP signal profiles. Therefore, a targeted modulation of LHR signalling at a spatial level could play an important role in designing a novel treatment for PCOS. Granulosa-lutein cells (GLCs) were obtained from women with or without PCOS as a by-product of egg collection for IVF. Cultured cells were subjected to LH stimulation (with or without treatment with an siRNA for APPL1) and the effects assessed on cyclic AMP (cAMP) production, steroidogenic gene expression, and steroid secretion. We then examined the impact of Org-42599, an LHR-selective, allosteric modulator, on LH signalling in GLCs from both groups. PCOS-derived GLCs exhibited enhanced responses following LH stimulation, without change in LHR gene or protein expression. Dose-response studies indicated higher sensitivity to LH in PCOS GLCs. Both control and PCOS-derived GLCs showed equivalent dependence on LHR internalisation for acute ligand-induced cAMP signalling. APPL1 knockdown in control GLCs resulted in enhancement of LH-induced cAMP but, in contrast, inhibition of APPL1 markedly reduced LH-mediated cAMP in PCOS GLCs, implying that the increased LH-LHR activity in PCOS involves reprogramming of APPL1 from a negative to a positive regulator of LHR-mediated cAMP signalling. The allosteric LHR inhibitor Org-42599 both decreased LH-induced cAMP signalling in PCOS-derived GLCs, and restored APPL1-dependent negative regulation. In summary, we show alteration in LHR-cAMP signalling in GLCs from PCOS involves rewiring of APPL1-dependent mechanisms. Selective targeting of LHR signalling with modulators such as Org-42599 offers a promising therapeutic approach for ‘correcting’ LH-dependent dysfunction in steroidogenic cells.