A Novel, More Efficient Approach to Generate Bioactive Inhibins

Area of Science:

• Reproductive Endocrinology
• Bone Biology
• Protein Engineering

Background:

• Inhibins regulate follicle-stimulating hormone (FSH) and are crucial for reproduction.
• Declining inhibin levels during menopause correlate with increased FSH and bone loss, suggesting therapeutic potential for osteoporosis.
• Challenges in inhibin therapy include difficulties in recombinant production, poor processing, and co-production of antagonistic activins.

Purpose of the Study:

• To develop a methodology to overcome challenges in producing potent and safe inhibin analogs.
• To investigate the role of the prodomain in inhibin bioactivity.
• To facilitate the investigation of inhibins as therapeutics for bone loss and other conditions.

Main Methods:

• Modified cleavage sites in alpha and betaA subunits to ensure complete processing of inhibins.
• Introduced a single point mutation (M418A) in the betaA subunit to reduce activin activity.
• Assessed the potency of inhibin A associated with its prodomain compared to mature inhibin A in vitro.

Main Results:

• Achieved a 9-fold increase in bioactive inhibin A and a 12.5-fold decrease in mature activin A production through cleavage site modifications.
• A single point mutation reduced residual activin activity by approximately 100-fold, further increasing inhibin bioactivity 8-fold.
• Inhibin A noncovalently associated with its prodomain demonstrated approximately 20-fold greater potency than mature inhibin A in bioassays.

Conclusions:

• Developed a novel method for producing potent inhibin A analogs with minimal antagonistic activin activity.
• The prodomain plays a significant role in enhancing inhibin bioactivity.
• These engineered inhibins offer a promising avenue for investigating therapeutic applications in osteoporosis and other related conditions.