A mitochondrial outer membrane protein TOMM20 maintains protein stability of androgen receptor and regulates AR transcriptional activity in prostate cancer cells

Abstract

Prostate cancer (PCa) is an androgen-dependent malignancy, with HSP90 and HSP70 serving as classical molecular chaperones that maintain androgen receptor (AR) protein stability and regulate its transcriptional activation. Surprisingly, our study identified TOMM20, a mitochondrial outer membrane protein, as a potential molecular chaperone with similar roles to HSP90/HSP70. We found that TOMM20 expression is elevated in PCa tissues and cell lines and positively correlates with AR levels. RNA-seq analysis revealed that TOMM20 knockdown significantly reduced the mRNA levels of AR-regulated genes. Additionally, the protein level of KLK3 (PSA) decreased, and AR binding to the androgen response element (ARE) of the KLK3 promoter was diminished following TOMM20 knockdown, leading to decreased KLK3 gene transcription. Furthermore, TOMM20 depletion reduced both cytoplasmic and nuclear AR protein levels and facilitated AR degradation via an E3 ubiquitin ligase SKP2-mediated ubiquitin-proteasome pathway, independent of heat shock proteins (HSPs). To our knowledge, this is the first report demonstrating that TOMM20, a mitochondrial outer translocase protein, stabilizes AR protein and enhances its transcriptional activity, while its knockdown promotes AR degradation through the SKP2-mediated ubiquitin-proteasome pathway. These findings suggest that TOMM20 may serve as a potential biomarker for PCa progression and a promising therapeutic target for drug development.