RESUMEN
Kisspeptin receptor (Kiss1R) is an important receptor that plays central regulatory roles in reproduction by regulating hormone release in the hypothalamus. We hypothesize that the formation of heterocomplexes between Kiss1R and other hypothalamus G protein-coupled receptors (GPCRs) affects their cellular signaling. Through screening of potential interactions between Kiss1R and hypothalamus GPCRs, we identified G protein-coupled estrogen receptor (GPER) as one interaction partner of Kiss1R. Based on the recognised function of kisspeptin and estrogen in regulating the reproductive system, we investigated the Kiss1R/GPER heterocomplex in more detail and revealed that complex formation significantly reduced Kiss1R-mediated signaling. GPER did not directly antagonize Kiss1R conformational changes upon ligand binding, but it rather reduced the cell surface expression of Kiss1R. These results therefore demonstrate a regulatory mechanism of hypothalamic hormone receptors via receptor cooperation in the reproductive system and modulation of receptor sensitivity.
Asunto(s)
Hipotálamo/metabolismo , Complejos Multiproteicos/genética , Receptores de Estrógenos/genética , Receptores Acoplados a Proteínas G/genética , Receptores de Kisspeptina-1/genética , Animales , Hormonas/biosíntesis , Hormonas/genética , Humanos , Complejos Multiproteicos/ultraestructura , Unión Proteica/genética , Receptores de Superficie Celular/genética , Receptores de Estrógenos/ultraestructura , Receptores Acoplados a Proteínas G/ultraestructura , Receptores de Kisspeptina-1/ultraestructura , Transducción de Señal/genéticaRESUMEN
Most estrogen receptor α (ERα) ligands target the ligand binding domain (LBD). Agonist 17ß-estradiol (E2) and tamoxifen (TM, known SERM), bind to the same site within the LBD. However, structures of ligand-bound complexes show that E2 and TM induce different conformations of helix 12 (H12). During the molecular modelling studies of some naturally occurring flavonoids such as quercetin, luteolin, myricetin, kaempferol, naringin, hesperidin, galangin, baicalein and epicatechin with human ERα (3ERT and 1GWR), we observed that most of the ligands bound to the active site pocket of both 3ERT and 1GWR. The docking scores, interaction analyses, and conformation of H12 provided the data to support for the estrogenic or antiestrogenic potential of these flavonoids to a limited degree. Explicit molecular dynamics for 50 ns was performed to identify the stability and compatibility pattern of protein-ligand complex and RMSD were obtained. Baicalein, epicatechin, and kaempferol with 1GWR complex showed similar RMSD trend with minor deviations in the protein backbone RMSD against 1GWR-E2 complex that provided clear indications that ligands were stable throughout the explicit molecular simulations in the protein and outcome of naringin-3ERT complex had an upward trend but stable throughout the simulations and all molecular dynamics showed stability with less than overall 1 Å deviation throughout the simulations. To examine their estrogenic or antiestrogenic potential, we studied the effect of the flavonoids on viability, progesterone receptor expression and 3xERE/3XERRE-driven reporter gene expression in ERα positive and estrogen responsive MCF-7 breast cancer cells. Epicatechin, myricetin, and kaempferol showed estrogenic potential at 5 µM concentration.