Bak and Bax are crucial for Gbp2-mediated pyroptosis during Vibrio and Salmonella infections.

Abstract

Pyroptosis a lytic form of programmed cell death, is a crucial host defense mechanism against bacterial pathogens. While caspase-mediated pathways are central to pyroptosis, the involvement of apoptotic regulators such as Bak, Bax, and MCL-1 in bacterial infection-induced pyroptosis remains unclear. Here, we investigated how these BCL-2 family proteins modulate pyroptosis induced by Vibrio vulnificus and Salmonella enterica serovar Typhimurium in murine cells. In mouse embryonic fibroblasts (MEFs), both pathogens strongly induced Gbp2 expression and activated caspase‑11, whereas activation of caspase‑1 occurred only in macrophages, indicating engagement of both non-canonical and canonical pyroptosis pathways. Importantly, Bak-/- and Bax-/- MEFs exhibited significantly reduced Gbp2 upregulation and caspase-11 activation-an effect most pronounced in Bak-deficient cells leading to attenuated pyroptotic cell death. These data suggest that pro-apoptotic proteins, Bak and Bax, act as positive regulators that amplify the Gbp2-caspase-11 axis. Conversely, overexpression of the anti-apoptotic protein MCL‑1 had no significant impact on Gbp2 expression, caspase activation, membrane integrity, or LDH release, indicating that pyroptosis proceeds independently of MCL‑1 regulation. Collectively, our findings uncover a novel role for Bak and Bax in promoting Gbp2-driven pyroptosis during Gram-negative bacterial infections, while MCL‑1 does not impede this process. This work expands our understanding of the crosstalk between apoptotic and pyroptotic pathways in innate immune responses.