PDIA1 promotes androgen receptor activation and prostate cancer cell survival through enhancing HMMR stability

To sustain rapid proliferation, cancer cells increase protein synthesis, intensifying reliance on protein disulfide isomerase A1 (PDIA1). It is largely unknown whether disulfide bond formation of PDIA1 substrates is driven by one or both CGHC motifs. Using active‐site trapping mutants in prostate cancer cells combined with mass spectrometry, we identified 29 proteins uniquely bound to the C 53 GHC 56 domain and 20 proteins uniquely bound to the C 397 GHC 400 domain. Hyaluronan‐mediated motility receptor (HMMR) was validated as a PDIA1 C 397 GHC 400 ‐specific substrate, with PDIA1 catalysing disulfide bond formation between Cys242 and Cys293. PDIA1 knockdown induced HMMR ubiquitination, blocked androgen receptor nuclear translocation, and suppressed prostate cancer cell growth, survival, and migration. These findings reveal a previously unknown role of PDIA1 in prostate cancer biology.