Partially Deglycosylated Equine LH Preferentially Activates β-Arrestin-Dependent Signaling at the Follicle-Stimulating Hormone Receptor

• Published in: Molecular endocrinology (Baltimore, Md.) Md.), 2010-03, Vol.24 (3), p.561-573
• Main Authors: Wehbi, Vanessa, Tranchant, Thibaud, Durand, Guillaume, Musnier, Astrid, Decourtye, Jérémy, Piketty, Vincent, Butnev, Vladimir Y, Bousfield, George R, Crépieux, Pascale, Maurel, Marie-Christine, Reiter, Eric
• Format: Article
• Language: English
• Subjects: Animals; Arrestins - metabolism; beta-Arrestins; Blotting, Western; Cattle; Cell Line; Cyclic AMP-Dependent Protein Kinases - metabolism; Enzyme Activation - drug effects; Female; Horses; Humans; Immunoprecipitation; Life Sciences; Luteinizing Hormone - analogs & derivatives; Luteinizing Hormone - chemistry; Luteinizing Hormone - metabolism; Luteinizing Hormone - pharmacology; Mice; Other; Phosphorylation - drug effects; Protein Binding; Protein Transport - drug effects; Receptors, FSH - agonists; Receptors, FSH - antagonists & inhibitors; Receptors, FSH - metabolism; Ribosomal Protein S6 - metabolism; RNA, Small Interfering; Signal Transduction - drug effects; Swine
• ISSN: 0888-8809; 1944-9917
• DOI: 10.1210/me.2009-0347

Deglycosylated FSH is known to trigger poor Gαs coupling while efficiently binding its receptor. In the present study, we tested the possibility that a deglycosylated equine LH (eLHdg) might be able to selectively activate β-arrestin-dependent signaling. We compared native eLH to an eLH derivative [i.e. truncated eLHβ (Δ121-149) combined with asparagine56-deglycosylated eLHα (eLHdg)] previously reported as an antagonist of cAMP accumulation at the FSH receptor (FSH-R). We confirmed that, when used in conjunction with FSH, eLHdg acted as an antagonist for cAMP accumulation in HEK-293 cells stably expressing the FSH-R. Furthermore, when used alone at concentrations up to 1 nm, eLHdg had no detectable agonistic activity on cAMP accumulation, protein kinase A activity or cAMP-responsive element-dependent transcriptional activity. At higher concentrations, however, a weak agonistic action was observed with eLHdg, whereas eLH led to robust responses whatever the concentration. Both eLH and eLHdg triggered receptor internalization and led to β-arrestin recruitment. Both eLH and eLHdg triggered ERK and ribosomal protein (rp) S6 phosphorylation at 1 nm. The depletion of endogenous β-arrestins had only a partial effect on eLH-induced ERK and rpS6 phosphorylation. In contrast, ERK and rpS6 phosphorylation was completely abolished at all time points in β-arrestin-depleted cells. Together, these results show that eLHdg has the ability to preferentially activate β-arrestin-dependent signaling at the FSH-R. This finding provides a new conceptual and experimental framework to revisit the physiological meaning of gonadotropin structural heterogeneity. Importantly, it also opens a field of possibilities for the development of selective modulators of gonadotropin receptors. A partially deglycosylated equine LH exerts a biased agonist activity at the FSH receptor, selectively activating beta-arrestin-dependent signaling when compared to native eLH.