USP9X deubiquitinates JAK1, driving copper-induced CASP9/CASP3/GSDME-dependent pyroptosis and liver injury in Wilson disease.

Wilson disease (WD) is a severe autosomal recessive disorder characterized by toxic copper accumulation, primarily causing hepatic injury. Despite existing treatments, the precise molecular mechanisms driving liver damage, particularly the role of programmed cell death like pyroptosis, remain poorly understood. Current standard-of-care focuses on copper chelation, but persistent liver injury can occur. This study addresses the gap by investigating if copper overload triggers pyroptosis in WD and how the USP9X/JAK1 axis regulates this process, offering new insights into disease pathogenesis.

Researchers performed integrated transcriptomic, proteomic, and ubiquitinomic analyses on liver tissues from Wilson disease patients and ATP7B-knockout cellular models to identify key pathways. The involvement of the JAK1/STAT1 signaling pathway, the CASP9/CASP3/GSDME axis, and USP9X-mediated deubiquitination was further investigated. This involved pharmacological inhibition, gene knockout, and knockdown approaches. Findings were subsequently validated in Atp7b-/- mouse models, confirming the mechanistic insights in an in vivo setting relevant to the disease.

Copper overload profoundly activated the JAK1/STAT1 signaling pathway and significantly enhanced reactive oxygen species (ROS) production. This cascade triggered the activation of CASP9 and CASP3, leading to GSDME cleavage. This cleavage ultimately caused a switch from hepatocyte apoptosis to a more inflammatory form of cell death, pyroptosis. Mechanistically, copper exposure upregulated USP9X expression, which then mediated the deubiquitination of JAK1 at lysine 249. This deubiquitination event stabilized JAK1, thereby enhancing its downstream signaling cascade and exacerbating cellular damage. > Pharmacological or genetic inhibition of the JAK1/STAT1 pathway or GSDME significantly attenuated pyroptosis and alleviated liver injury in Wilson disease mouse models, even in the presence of persistent copper accumulation.