Human Luteinizing Hormone and Chorionic Gonadotropin Display Biased Agonism at the LH and LH/CG Receptors

Laura Riccetti,Manuela Simoni,Livio Casarini,Nathalie Gallay,Eric Reiter,Mohammed Akli Ayoub,Romain Yvinec,Danièle Klett,Yves Combarnous

doi:10.1038/s41598-017-01078-8

Abstract

Human luteinizing hormone (LH) and chorionic gonadotropin (hCG) have been considered biologically equivalent because of their structural similarities and their binding to the same receptor; the LH/CGR. However, accumulating evidence suggest that LH/CGR differentially responds to the two hormones triggering differential intracellular signaling and steroidogenesis. The mechanistic basis of such differential responses remains mostly unknown. Here, we compared the abilities of recombinant rhLH and rhCG to elicit cAMP, β-arrestin 2 activation, and steroidogenesis in HEK293 cells and mouse Leydig tumor cells (mLTC-1). For this, BRET and FRET technologies were used allowing quantitative analyses of hormone activities in real-time and in living cells. Our data indicate that rhLH and rhCG differentially promote cell responses mediated by LH/CGR revealing interesting divergences in their potencies, efficacies and kinetics: rhCG was more potent than rhLH in both HEK293 and mLTC-1 cells. Interestingly, partial effects of rhLH were found on β-arrestin recruitment and on progesterone production compared to rhCG. Such a link was further supported by knockdown experiments. These pharmacological differences demonstrate that rhLH and rhCG act as natural biased agonists. The discovery of novel mechanisms associated with gonadotropin-specific action may ultimately help improve and personalize assisted reproduction technologies.

Highlights

Leading to both adenylyl cyclase and phospholipase C activation through functional coupling to Gαs and Gαq, respectively[6, 7]
The canonical Gαs/cAMP pathway as well as β-arrestin 2 recruitment were analyzed upon the activation of human luteinizing hormone (LH)/CGR transiently expressed in HEK293 cells or LHR endogenously expressed in murine Leydig tumor cell line[11, 36]
We investigated the differential activity exerted by rhCG and rhLH upon binding to their common receptor, human LH/CGR transiently expressed in HEK293 cells or mouse LHR endogenously expressed in mLTC-1 cells

Summary

Introduction

Leading to both adenylyl cyclase and phospholipase C activation through functional coupling to Gαs and Gαq, respectively[6, 7]. It is worth noting that consistent with HEK293 cell data, rhCG and rhLH promoted similar maximal cAMP responses in mLTC-1 cells despite the differences in their potencies confirming that both are full agonists for cAMP pathway (Fig. 1C and D) (Table 2).

Results

Conclusion