Species-specific cleavage of the autophagy adaptor p62 dictates responses to TNF.

Inflammation can affect many diseases. We report here that inflammatory cytokines invoke caspase-8-mediated cleavage of the autophagy adaptor p62/SQSTM1 at aspartic acid 329 in human cells, producing a previously described truncated form, which we term tr-p62. We show that TNF-driven cell death is tr-p62 dependent and that autophagy inhibition promotes death via tr-p62 accumulation. Mechanistically, p62 cleavage is receptor-interacting serine/threonine-protein kinase 1 (RIPK1) dependent, and tr-p62 stabilizes caspase-8 activating complex-IIb. tr-p62-driven cell death downstream of TNF is also RIPK1 and caspase dependent, promoting feedforward caspase-8 activation. p62 cleavage does not, however, affect necroptosis. Surprisingly, this caspase-8 cleavage site in p62 is absent in mice, and introduction of cleavable forms of p62 into mouse cells causes sensitization to TNF-induced death. Moreover, mice with CRISPR-Cas9-generated cleavable p62 exhibit TNF hypersensitivity and intestinal inflammation in vivo. These findings provide significant insights into TNF-induced cell death and introduce a mouse model that may provide better clarity for human-related studies of inflammatory disease.