BIRC6 prevents GSDME-mediated pyroptosis and promotes cisplatin resistance via a non-canonical UBC domain-dependent steric hindrance

BACKGROUND: Pyroptosis, particularly gasdermin E (GSDME)-mediated programmed cell death, has emerged as a crucial determinant of chemosensitivity and antitumor immunity. Although baculoviral inhibitor of apoptosis protein (IAP) repeat-containing protein 6 (BIRC6) is a known inhibitor of apoptosis, its potential role in regulating the pyroptotic switch and cisplatin resistance in lung adenocarcinoma (LUAD) remains unclear. Therefore, in this study, we aimed to elucidate the molecular mechanism underlying BIRC6-mediated regulation of pyroptosis and cisplatin resistance in LUAD. METHODS: We integrated bioinformatics analysis, proteomics, and structural modeling with CRISPR-Cas9-mediated mutagenesis to dissect the interplay between BIRC6 and pyroptosis. Subsequently, we functionally validated the interaction between BIRC6 and pyroptosis using cisplatin-resistant LUAD cell lines and xenograft models. RESULTS: We observed that BIRC6 was aberrantly upregulated in cisplatin-resistant LUAD tissues and correlated with poor clinical prognosis. Functionally, while BIRC6 knockdown resensitized resistant LUAD cells to cisplatin by restoring GSDME-dependent pyroptosis, its overexpression in sensitive cells stifled this pathway to confer resistance. Mechanistically, rather than promoting ubiquitin-proteasomal degradation, BIRC6 physically interacted with the N-terminal pore-forming domain of GSDME via its ubiquitin-conjugating domain. Structural analysis revealed that this interaction created steric hindrance that masked the specific caspase-3 cleavage site on GSDME, thereby preventing the occurrence of pyroptosis. Disruption of the BIRC6-GSDME interface effectively restored pyroptosis and triggered robust inflammatory cell death, which subsequently enhanced cisplatin efficacy in vivo. CONCLUSION: Our findings uncovered a non-canonical mechanism wherein BIRC6 structurally locks GSDME in an inactive state to confer cisplatin resistance. Consequently, targeting the BIRC6-GSDME interface offers a novel therapeutic strategy to trigger pyroptosis and overcome chemotherapy resistance in LUAD.