CDB25:0003334 CGB5 — LHCGR
Experimentally validated in Human; Orthology-inferred in Frog, Zebrafish, Macaque, Cow, Marmoset
Title
Journal:; Year Published:
Abstract
Absence of exon 10 of the human luteinizing hormone (LH) receptor impairs LH, but not human chorionic gonadotropin action.
The Journal of clinical endocrinology and metabolism, 2003; PubMed, Homo sapiens CGB5 — Homo sapiens LHCGR
ABSTRACT: The LH receptor (LHR) mediates the actions of LH and human chorionic gonadotropin (hCG). In vivo data showed that deletion of exon 10 does not affect hCG action, whereas LH action is impaired. To investigate the role of exon 10 in LH/hCG action in vitro we created stable COS-7 cells expressing the LHR with (wt) or without (-ex10) exon 10. Binding experiments showed that the affinities of LH and hCG to the LHR wt and -ex10 were similar. Stimulation of wt with hCG or LH resulted in increased cAMP. cAMP production was significantly impaired in -ex10 stimulated with LH. This response was not altered by pertussis toxin, excluding that G(i) becomes activated in LHR -ex10. In desensitization experiments, intracellular cAMP of LHR wt and -ex10 declined to approximately 30%. No difference in intracellular cAMP was detected between LHR wt or -ex10 after recovery and restimulation with hCG or LH. These experiments show that impaired cAMP production of LHR -ex10 stimulated with LH is not due to anomalous receptor coupling or desensitization. We conclude that although exon 10 of the LHR plays no role in ligand binding, it is important for receptor activation by LH by a mechanism probably involving extracellular conformational changes.
Differences in Signal Activation by LH and hCG are Mediated by the LH/CG Receptor's Extracellular Hinge Region.
Frontiers in endocrinology, 2015; PubMed, Homo sapiens CGB5 — Homo sapiens LHCGR
ABSTRACT: The human lutropin (hLH)/choriogonadotropin (hCG) receptor (LHCGR) can be activated by binding two slightly different gonadotropic glycoprotein hormones, choriogonadotropin (CG) - secreted by the placenta, and lutropin (LH) - produced by the pituitary. They induce different signaling profiles at the LHCGR. This cannot be explained by binding to the receptor's leucine-rich-repeat domain (LRRD), as this binding is similar for the two hormones. We therefore speculate that there are previously unknown differences in the hormone/receptor interaction at the extracellular hinge region, which might help to understand functional differences between the two hormones. We have therefore performed a detailed study of the binding and action of LH and CG at the LHCGR hinge region. We focused on a primate-specific additional exon in the hinge region, which is located between LRRD and the serpentine domain. The segment of the hinge region encoded by exon10 was previously reported to be only relevant to hLH signaling, as the exon10-deletion receptor exhibits decreased hLH signaling, but unchanged hCG signaling. We designed an advanced homology model of the hormone/LHCGR complex, followed by experimental characterization of relevant fragments in the hinge region. In addition, we examined predictions of a helical exon10-encoded conformation by block-wise polyalanine (helix supporting) mutations. These helix preserving modifications showed no effect on hormone-induced signaling. However, introduction of a structure-disturbing double-proline mutant LHCGR-Q303P/E305P within the exon10-helix has, in contrast to exon10-deletion, no impact on hLH, but only on hCG signaling. This opposite effect on signaling by hLH and hCG can be explained by distinct sites of hormone interaction in the hinge region. In conclusion, our analysis provides details of the differences between hLH- and hCG-induced signaling that are mainly determined in the L2-beta loop of the hormones and in the hinge region of the receptor.