Crosslinked bifunctional gonadotropin analogs with reduced efficacy

Area of Science:

• Endocrinology
• Glycobiology
• Protein Chemistry

Background:

• N-linked oligosaccharides on human choriogonadotropin (hCG) and follitropin (hFSH) alpha-subunit loop 2 (alpha2) significantly impact hormone efficacy.
• Removal of the alpha2 oligosaccharide reduces hCG efficacy to approximately 40% of the wild-type hormone.

Purpose of the Study:

• To investigate methods for further reducing the efficacy of glycoprotein hormone analogs.
• To explore the combined effects of deglycosylation and intersubunit disulfide crosslinks on hormone activity.

Main Methods:

• Creation of hCG analogs with specific N-linked oligosaccharide modifications.
• Introduction of intersubunit disulfide crosslinks in deglycosylated analogs.
• Assessment of receptor binding affinity and cyclic AMP accumulation assays to determine hormone efficacy.

Main Results:

• Certain intersubunit disulfide crosslinks reduced the efficacy of hCG analogs lacking the alpha2 oligosaccharide.
• An hCG/hFSH chimera with a specific disulfide bond exhibited significantly reduced efficacy (<10% and <5% of hCG and hFSH, respectively).
• This chimera showed altered receptor binding profiles, binding lutropin receptors better than hCG but follitropin receptors less effectively than hFSH.

Conclusions:

• Complete deglycosylation is not necessary to achieve low-efficacy glycoprotein hormone analogs.
• Targeted modifications, including specific amino acid substitutions and disulfide bond formation, can effectively attenuate hormone function.
• These findings provide a strategy for developing glycoprotein hormone analogs with tailored biological activity.