Ligand Binding Prolongs Androgen Receptor Protein Half-Life by Reducing its Degradation

Area of Science:

• Reproductive Biology
• Molecular Endocrinology
• Cellular Signaling

Background:

• Androgens play a role in female reproduction, but their molecular mechanisms in reproductive tissues are unclear.
• The gene-regulatory function of the androgen receptor (AR) in granulosa cells (GCs) is largely unknown.

Purpose of the Study:

• To investigate the extranuclear actions of the androgen receptor (AR) in human and mouse granulosa cells (GCs).
• To elucidate the mechanism by which dihydrotestosterone (DHT) affects AR protein stability.

Main Methods:

• Investigated androgen-responsive gene expression in human and mouse GCs.
• Utilized human granulosa-like KGN cells to study AR protein half-life.
• Performed immunofluorescence, proteasome inhibition, and gene knockdown (PTEN, importin 7) experiments.

Main Results:

• AR's gene-regulatory activity in GCs is negligible.
• DHT significantly increases AR protein half-life in GCs and prostate cancer cells.
• Nuclear AR is protected from degradation in a DHT-dependent manner, independent of DNA binding and importin 7.
• PTEN knockdown did not affect DHT-induced AR accumulation.

Conclusions:

• Ligand binding sequesters AR in the nucleus, protecting it from cytoplasmic degradation.
• This mechanism enhances AR stability and may establish a positive feedback loop for androgen signaling in reproductive tissues.
• AR stabilization is distinct from other steroid receptors and has potential physiological significance.