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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.


Related in: MedlinePlus

Differences between hLH bound homology models of LHCGR hinge region and LHCGR hinge-delExon10. For LHCGR, the sulfated sTyr (yellow) of the hinge region (lilac) fits deep into the binding pocket of bound hLH between alpha- (surface blue) and beta-subunit (green, red adapted conformation for 70PPLP). For clarity, exon10-helix (orange) of LHCGR is cut open and the adjacent helix is omitted (dotted line). By contrast, the deletion in LHCGR-delExon10 (pale pink) causes displacement of the residues in the middle of the hinge region after the deletion position (red triangle). Subsequently sTyr331 is displaced and thus the interaction of the sulfation group with the hLH binding pocket is impaired. However, the deletion of 27 residues in LHCGR-delEx10 (contains exon10-helix) causes the polypeptide chain to contract, so that the adjacent helix (gray) is arranged in the same place as the exon10-helix (orange). Upon hormone binding, the signal is conveyed via the hinge region (lilac) through a hormone-induced movement of the pivot helix, the disulfide linked agonistic unit and the area prior to the exon10-helix, both of which are probably embedded (dashed box) in between the loops of the transmembrane domain of LHCGR.
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Figure 8: Differences between hLH bound homology models of LHCGR hinge region and LHCGR hinge-delExon10. For LHCGR, the sulfated sTyr (yellow) of the hinge region (lilac) fits deep into the binding pocket of bound hLH between alpha- (surface blue) and beta-subunit (green, red adapted conformation for 70PPLP). For clarity, exon10-helix (orange) of LHCGR is cut open and the adjacent helix is omitted (dotted line). By contrast, the deletion in LHCGR-delExon10 (pale pink) causes displacement of the residues in the middle of the hinge region after the deletion position (red triangle). Subsequently sTyr331 is displaced and thus the interaction of the sulfation group with the hLH binding pocket is impaired. However, the deletion of 27 residues in LHCGR-delEx10 (contains exon10-helix) causes the polypeptide chain to contract, so that the adjacent helix (gray) is arranged in the same place as the exon10-helix (orange). Upon hormone binding, the signal is conveyed via the hinge region (lilac) through a hormone-induced movement of the pivot helix, the disulfide linked agonistic unit and the area prior to the exon10-helix, both of which are probably embedded (dashed box) in between the loops of the transmembrane domain of LHCGR.

Mentions: Thus, we initially built the first LHCGR model especially for the middle segment of the hinge region, not only since this section of 34 residues (I296-Y330) is not resolved in the FSHR structure (27), but also because molecular details of the interactions between the respective hormone and the receptor’s hinge region evidently differ in this part of the LHCGR. The resulting LHCGR models share coincident spatial locations for LRRD and a pair of two cysteines from cysteine box 2 (Cb-2) and 3 (Cb-3) which form cysteine bridges between Cys279–Cys343 and Cys280–Cys353 (Figures 1 and 8). This is consistent with the reported spatial proximity of Cb-2 and Cb-3, due to the disulfide bridges for LHCGR (23) and also for TSHR (39).


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)

Differences between hLH bound homology models of LHCGR hinge region and LHCGR hinge-delExon10. For LHCGR, the sulfated sTyr (yellow) of the hinge region (lilac) fits deep into the binding pocket of bound hLH between alpha- (surface blue) and beta-subunit (green, red adapted conformation for 70PPLP). For clarity, exon10-helix (orange) of LHCGR is cut open and the adjacent helix is omitted (dotted line). By contrast, the deletion in LHCGR-delExon10 (pale pink) causes displacement of the residues in the middle of the hinge region after the deletion position (red triangle). Subsequently sTyr331 is displaced and thus the interaction of the sulfation group with the hLH binding pocket is impaired. However, the deletion of 27 residues in LHCGR-delEx10 (contains exon10-helix) causes the polypeptide chain to contract, so that the adjacent helix (gray) is arranged in the same place as the exon10-helix (orange). Upon hormone binding, the signal is conveyed via the hinge region (lilac) through a hormone-induced movement of the pivot helix, the disulfide linked agonistic unit and the area prior to the exon10-helix, both of which are probably embedded (dashed box) in between the loops of the transmembrane domain of LHCGR.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 8: Differences between hLH bound homology models of LHCGR hinge region and LHCGR hinge-delExon10. For LHCGR, the sulfated sTyr (yellow) of the hinge region (lilac) fits deep into the binding pocket of bound hLH between alpha- (surface blue) and beta-subunit (green, red adapted conformation for 70PPLP). For clarity, exon10-helix (orange) of LHCGR is cut open and the adjacent helix is omitted (dotted line). By contrast, the deletion in LHCGR-delExon10 (pale pink) causes displacement of the residues in the middle of the hinge region after the deletion position (red triangle). Subsequently sTyr331 is displaced and thus the interaction of the sulfation group with the hLH binding pocket is impaired. However, the deletion of 27 residues in LHCGR-delEx10 (contains exon10-helix) causes the polypeptide chain to contract, so that the adjacent helix (gray) is arranged in the same place as the exon10-helix (orange). Upon hormone binding, the signal is conveyed via the hinge region (lilac) through a hormone-induced movement of the pivot helix, the disulfide linked agonistic unit and the area prior to the exon10-helix, both of which are probably embedded (dashed box) in between the loops of the transmembrane domain of LHCGR.
Mentions: Thus, we initially built the first LHCGR model especially for the middle segment of the hinge region, not only since this section of 34 residues (I296-Y330) is not resolved in the FSHR structure (27), but also because molecular details of the interactions between the respective hormone and the receptor’s hinge region evidently differ in this part of the LHCGR. The resulting LHCGR models share coincident spatial locations for LRRD and a pair of two cysteines from cysteine box 2 (Cb-2) and 3 (Cb-3) which form cysteine bridges between Cys279–Cys343 and Cys280–Cys353 (Figures 1 and 8). This is consistent with the reported spatial proximity of Cb-2 and Cb-3, due to the disulfide bridges for LHCGR (23) and also for TSHR (39).

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.


Related in: MedlinePlus