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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.


Sketches of the different hLH and hCG interactions with the middle section of the hinge region with various LHCGR constructs. (A) LHCGR-wt: exon10-helix shifts the sulfated sTyr331 into an appropriate spatial position necessary to interact with hLH, while, for hCG, exon10-helix acts as a structural interface. (B) LHCGR-delExon10: deletion of exon 10 leads to displacement of the remaining residues beyond the cutting point (red triangle). Subsequently sTyr331 abrogates the interaction with hLH, However, the adjacent helix moves into the position previously occupied by the exon 10-helix and thus provides a structural interface for activation by hCG; (C) LHCGR-Q303P/E308P double proline mutation within exon10 disturbs the helical structure of exon10-helix and interferes with the hCG-induced hinge movement and signaling. However, in this case, the retained length of the middle hinge region allows the appropriate adjustment of sTyr331 for proper hLH interaction and signaling.
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Figure 7: Sketches of the different hLH and hCG interactions with the middle section of the hinge region with various LHCGR constructs. (A) LHCGR-wt: exon10-helix shifts the sulfated sTyr331 into an appropriate spatial position necessary to interact with hLH, while, for hCG, exon10-helix acts as a structural interface. (B) LHCGR-delExon10: deletion of exon 10 leads to displacement of the remaining residues beyond the cutting point (red triangle). Subsequently sTyr331 abrogates the interaction with hLH, However, the adjacent helix moves into the position previously occupied by the exon 10-helix and thus provides a structural interface for activation by hCG; (C) LHCGR-Q303P/E308P double proline mutation within exon10 disturbs the helical structure of exon10-helix and interferes with the hCG-induced hinge movement and signaling. However, in this case, the retained length of the middle hinge region allows the appropriate adjustment of sTyr331 for proper hLH interaction and signaling.

Mentions: These data suggest that the exon10-region serves for the two hormones in a different manner. For hLH-induced receptor activation, the exon10-helix is necessary as a non-specific spacer-element to adjust the sulfated Tyr331 into an appropriate location and orientation for a compatible H-Bond interaction with hLH. For hCG-induced activation, the exon10 determined helix acts as a structural interface within the hinge region (Figure 7A). Deletion of exon 10 causes shortening of the middle hinge loop, which subsequently leads to spatial delocalization of the downstream regions. The sequence forming the adjacent helix comes into the position of the previous exon10-helix (Figures 7B and 8). This might explain why hCG can induce signaling, probably because the displaced adjacent helix adopts the structural function of exon10-helix.


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)

Sketches of the different hLH and hCG interactions with the middle section of the hinge region with various LHCGR constructs. (A) LHCGR-wt: exon10-helix shifts the sulfated sTyr331 into an appropriate spatial position necessary to interact with hLH, while, for hCG, exon10-helix acts as a structural interface. (B) LHCGR-delExon10: deletion of exon 10 leads to displacement of the remaining residues beyond the cutting point (red triangle). Subsequently sTyr331 abrogates the interaction with hLH, However, the adjacent helix moves into the position previously occupied by the exon 10-helix and thus provides a structural interface for activation by hCG; (C) LHCGR-Q303P/E308P double proline mutation within exon10 disturbs the helical structure of exon10-helix and interferes with the hCG-induced hinge movement and signaling. However, in this case, the retained length of the middle hinge region allows the appropriate adjustment of sTyr331 for proper hLH interaction and signaling.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 7: Sketches of the different hLH and hCG interactions with the middle section of the hinge region with various LHCGR constructs. (A) LHCGR-wt: exon10-helix shifts the sulfated sTyr331 into an appropriate spatial position necessary to interact with hLH, while, for hCG, exon10-helix acts as a structural interface. (B) LHCGR-delExon10: deletion of exon 10 leads to displacement of the remaining residues beyond the cutting point (red triangle). Subsequently sTyr331 abrogates the interaction with hLH, However, the adjacent helix moves into the position previously occupied by the exon 10-helix and thus provides a structural interface for activation by hCG; (C) LHCGR-Q303P/E308P double proline mutation within exon10 disturbs the helical structure of exon10-helix and interferes with the hCG-induced hinge movement and signaling. However, in this case, the retained length of the middle hinge region allows the appropriate adjustment of sTyr331 for proper hLH interaction and signaling.
Mentions: These data suggest that the exon10-region serves for the two hormones in a different manner. For hLH-induced receptor activation, the exon10-helix is necessary as a non-specific spacer-element to adjust the sulfated Tyr331 into an appropriate location and orientation for a compatible H-Bond interaction with hLH. For hCG-induced activation, the exon10 determined helix acts as a structural interface within the hinge region (Figure 7A). Deletion of exon 10 causes shortening of the middle hinge loop, which subsequently leads to spatial delocalization of the downstream regions. The sequence forming the adjacent helix comes into the position of the previous exon10-helix (Figures 7B and 8). This might explain why hCG can induce signaling, probably because the displaced adjacent helix adopts the structural function of exon10-helix.

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.