Limits...
Differences in Signal Activation by LH and hCG are Mediated by the LH/CG Receptor's Extracellular Hinge Region.

Grzesik P, Kreuchwig A, Rutz C, Furkert J, Wiesner B, Schuelein R, Kleinau G, Gromoll J, Krause G - Front Endocrinol (Lausanne) (2015)

Bottom Line: These helix preserving modifications showed no effect on hormone-induced 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.

View Article: PubMed Central - PubMed

Affiliation: Leibniz Institut für Molekulare Pharmakologie (FMP) , Berlin , Germany.

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.

No MeSH data available.


Extension of the hinge region in the homology model of the ectodomain of LHCGR with hLH bound to both the leucine-rich-repeat domain (LRRD) (wheat) and to this extension of the hinge region (lilac). The two predicted helices within the middle of hinge region, the exon10-helix (orange) and the adjacent helix (gray), interact with the alpha-subunit of hLH. The following sulfation group of sTyr331 (yellow) binds in a binding pocket between the alpha-subunit (blue) and beta-subunit (green) of hLH. The specific conformation of the hLH beta-subunit in the L2-beta loop caused by 70PPLP (colored in red) that differs from hCG (see also fig 2 colored in green) performs more productive H-bond interactions (insert upper right panel) than hCG.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4585211&req=5

Figure 4: Extension of the hinge region in the homology model of the ectodomain of LHCGR with hLH bound to both the leucine-rich-repeat domain (LRRD) (wheat) and to this extension of the hinge region (lilac). The two predicted helices within the middle of hinge region, the exon10-helix (orange) and the adjacent helix (gray), interact with the alpha-subunit of hLH. The following sulfation group of sTyr331 (yellow) binds in a binding pocket between the alpha-subunit (blue) and beta-subunit (green) of hLH. The specific conformation of the hLH beta-subunit in the L2-beta loop caused by 70PPLP (colored in red) that differs from hCG (see also fig 2 colored in green) performs more productive H-bond interactions (insert upper right panel) than hCG.

Mentions: The IntFold2 fragment matches the experimental data best. The initial homologous interaction model for the extracellular domain of LHCGR with bound hormones lacked the sequence in the middle of the hinge region, as this segment was unresolved in the crystal structure of FSH/FSHR (dashed orange line in Figure 3A). Thus, we inserted our predicted fragment for this missing part and generated an hLH/hLHCGR interaction model of the extracellular domain containing a complete hinge region for the first time. This resulted in an LHCGR/hLH interaction model, where – apart from the sTyr331 interaction with the binding pocket between alpha and beta-subunits of hLH (insert Figure 4) – the predicted exon10-helix and adjacent helix of LHCGR interact with the alpha-subunit of the hormone (zoomed in box, Figure 4).


Differences in Signal Activation by LH and hCG are Mediated by the LH/CG Receptor's Extracellular Hinge Region.

Grzesik P, Kreuchwig A, Rutz C, Furkert J, Wiesner B, Schuelein R, Kleinau G, Gromoll J, Krause G - Front Endocrinol (Lausanne) (2015)

Extension of the hinge region in the homology model of the ectodomain of LHCGR with hLH bound to both the leucine-rich-repeat domain (LRRD) (wheat) and to this extension of the hinge region (lilac). The two predicted helices within the middle of hinge region, the exon10-helix (orange) and the adjacent helix (gray), interact with the alpha-subunit of hLH. The following sulfation group of sTyr331 (yellow) binds in a binding pocket between the alpha-subunit (blue) and beta-subunit (green) of hLH. The specific conformation of the hLH beta-subunit in the L2-beta loop caused by 70PPLP (colored in red) that differs from hCG (see also fig 2 colored in green) performs more productive H-bond interactions (insert upper right panel) than hCG.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4585211&req=5

Figure 4: Extension of the hinge region in the homology model of the ectodomain of LHCGR with hLH bound to both the leucine-rich-repeat domain (LRRD) (wheat) and to this extension of the hinge region (lilac). The two predicted helices within the middle of hinge region, the exon10-helix (orange) and the adjacent helix (gray), interact with the alpha-subunit of hLH. The following sulfation group of sTyr331 (yellow) binds in a binding pocket between the alpha-subunit (blue) and beta-subunit (green) of hLH. The specific conformation of the hLH beta-subunit in the L2-beta loop caused by 70PPLP (colored in red) that differs from hCG (see also fig 2 colored in green) performs more productive H-bond interactions (insert upper right panel) than hCG.
Mentions: The IntFold2 fragment matches the experimental data best. The initial homologous interaction model for the extracellular domain of LHCGR with bound hormones lacked the sequence in the middle of the hinge region, as this segment was unresolved in the crystal structure of FSH/FSHR (dashed orange line in Figure 3A). Thus, we inserted our predicted fragment for this missing part and generated an hLH/hLHCGR interaction model of the extracellular domain containing a complete hinge region for the first time. This resulted in an LHCGR/hLH interaction model, where – apart from the sTyr331 interaction with the binding pocket between alpha and beta-subunits of hLH (insert Figure 4) – the predicted exon10-helix and adjacent helix of LHCGR interact with the alpha-subunit of the hormone (zoomed in box, Figure 4).

Bottom Line: These helix preserving modifications showed no effect on hormone-induced 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.

View Article: PubMed Central - PubMed

Affiliation: Leibniz Institut für Molekulare Pharmakologie (FMP) , Berlin , Germany.

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.

No MeSH data available.