Gonadotropin-Releasing Hormone (GnRH) Receptor Structure and GnRH Binding

Area of Science:

• Molecular Biology
• Endocrinology
• Structural Biology

Background:

• The human gonadotropin-releasing hormone (GnRH) receptor, a class A G protein-coupled receptor (GPCR), lacks a cytoplasmic tail but possesses key structural motifs.
• Understanding GPCRs, including the GnRH receptor, is crucial for reproductive regulation.
• Recent X-ray crystallographic structures of GPCRs offer insights into their inactive and active conformations.

Purpose of the Study:

• To review how GPCR crystal structures inform GnRH receptor structure, activation mechanisms, and ligand binding.
• To explore the role of conserved and conformation-specific interactions in GnRH receptor function and signaling.
• To correlate GnRH receptor mutations with congenital hypogonadotropic hypogonadism and their structural basis.

Main Methods:

• Analysis of X-ray crystallographic structures of GPCRs in inactive and active states.
• Identification and comparison of conserved and conformation-specific interhelical contacts within GPCRs.
• Correlation of mutation data from GnRH receptor studies with structural findings.

Main Results:

• Ligands bind to extracellular surfaces, while transmembrane helices transmit signals to the cytoplasmic side for G protein activation.
• Forty conserved non-covalent interactions stabilize class A GPCR structures, including the GnRH receptor, with mutations affecting expression.
• Approximately half of intramolecular interactions differ between inactive and active GPCR states, with specific contacts stabilizing each conformation.

Conclusions:

• Conserved interhelical contacts are vital for maintaining GnRH receptor structure and function, with mutations linked to hypogonadotropic hypogonadism.
• Conformation-specific interactions dictate receptor activation and G protein binding, explaining differential effects of mutations on receptor efficiency.
• GPCR structural analysis provides a framework for understanding GnRH receptor binding and activation, including interactions with GnRH peptides.