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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.


Sketch (A) and homology model (B) of the full length LHCG-receptor with heterodimeric hormone (α and β subunit) bound to the extracellular leucine-rich-repeat domain (LRRD) and the hinge region. The hinge region that harbors exon10 and the second hormone binding site (sTyr) provides a structural and functional link between the LRRD and the heptahelical transmembrane domain.
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Figure 1: Sketch (A) and homology model (B) of the full length LHCG-receptor with heterodimeric hormone (α and β subunit) bound to the extracellular leucine-rich-repeat domain (LRRD) and the hinge region. The hinge region that harbors exon10 and the second hormone binding site (sTyr) provides a structural and functional link between the LRRD and the heptahelical transmembrane domain.

Mentions: The G protein-coupled receptors (GPCR) comprise a large superfamily of signal-mediating membrane bound proteins. The human lutropin (hLH)/choriogonadotropin (hCG) receptor (LHCGR) is evolutionary linked with the follitropin receptor (FSHR) and the thyrotropin receptor (TSHR). These three receptors belong to the group of glycoprotein-hormone receptors (GPHR), a subfamily of the rhodopsin-like GPCR (1). The structural topology of the GPHR is characterized by a large N-terminal extracellular region, which can be subdivided into the leucine-rich-repeat domain (LRRD) and the hinge region. The LRRD is responsible for the initial interaction with its corresponding hormone; the hinge region (LHCGR: L285-E354), harbors a second hormone binding site. It acts as a structural and functional link with the transmembrane region and thus assumes a key role in signal initiation and transduction (2). The transmembrane spanning region consists of seven transmembrane helices (TMH), connected by intra-cellular loops (ICLs) and extracellular loops (ECLs) and a cytoplasmic tail (Figure 1). Conformational changes in the TMH region during the activation lead to interaction and release of the intracellular signaling proteins (3).


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)

Sketch (A) and homology model (B) of the full length LHCG-receptor with heterodimeric hormone (α and β subunit) bound to the extracellular leucine-rich-repeat domain (LRRD) and the hinge region. The hinge region that harbors exon10 and the second hormone binding site (sTyr) provides a structural and functional link between the LRRD and the heptahelical transmembrane domain.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 1: Sketch (A) and homology model (B) of the full length LHCG-receptor with heterodimeric hormone (α and β subunit) bound to the extracellular leucine-rich-repeat domain (LRRD) and the hinge region. The hinge region that harbors exon10 and the second hormone binding site (sTyr) provides a structural and functional link between the LRRD and the heptahelical transmembrane domain.
Mentions: The G protein-coupled receptors (GPCR) comprise a large superfamily of signal-mediating membrane bound proteins. The human lutropin (hLH)/choriogonadotropin (hCG) receptor (LHCGR) is evolutionary linked with the follitropin receptor (FSHR) and the thyrotropin receptor (TSHR). These three receptors belong to the group of glycoprotein-hormone receptors (GPHR), a subfamily of the rhodopsin-like GPCR (1). The structural topology of the GPHR is characterized by a large N-terminal extracellular region, which can be subdivided into the leucine-rich-repeat domain (LRRD) and the hinge region. The LRRD is responsible for the initial interaction with its corresponding hormone; the hinge region (LHCGR: L285-E354), harbors a second hormone binding site. It acts as a structural and functional link with the transmembrane region and thus assumes a key role in signal initiation and transduction (2). The transmembrane spanning region consists of seven transmembrane helices (TMH), connected by intra-cellular loops (ICLs) and extracellular loops (ECLs) and a cytoplasmic tail (Figure 1). Conformational changes in the TMH region during the activation lead to interaction and release of the intracellular signaling proteins (3).

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.