A novel Leydig cell cDNA-derived protein is a relaxin-like factor

Area of Science:

• Endocrinology and Reproductive Biology
• Molecular Endocrinology
• Protein Chemistry

Background:

• Leydig cells, crucial for testosterone production, express a gene for a novel protein within the insulin/relaxin family.
• This protein, termed Leydig cell insulin-like protein (LEY I-L), was identified based on its genetic message.
• Understanding LEY I-L's function is key to comprehending Leydig cell biology and potential endocrine roles.

Purpose of the Study:

• To synthesize human Leydig cell insulin-like protein (LEY I-L) based on its cDNA sequence.
• To investigate the potential target organs and biological activity of the synthesized LEY I-L.
• To determine if LEY I-L interacts with insulin or relaxin receptors and modulates their activity.

Main Methods:

• Chemical synthesis of human LEY I-L using the deduced amino acid sequence from published cDNA.
• Binding assays using crude membrane preparations from mouse uterus and brain.
• Receptor cross-reactivity studies with insulin and relaxin receptors.
• In vivo assessment of LEY I-L's effect on relaxin-mediated symphysis pubis widening in mice.

Main Results:

• Synthesized human LEY I-L specifically binds to membrane preparations of mouse uterus and brain.
• LEY I-L exhibits cross-reactivity with the relaxin receptor but not the insulin receptor.
• LEY I-L alone has no discernible effect, but it significantly potentiates relaxin-induced symphysis pubis widening.

Conclusions:

• Leydig cell insulin-like protein (LEY I-L) functions as a relaxin-like factor, not an insulin-like factor.
• LEY I-L's specific binding and interaction with the relaxin receptor suggest a role in relaxin signaling pathways.
• The potentiating effect of LEY I-L on relaxin activity indicates a novel mechanism for modulating reproductive tissue responses.