The deubiquitinase OTUD1 deubiquitinates TIPE2 and plays a protective role in sepsis-induced lung injury by targeting TAK1-mediated MAPK and NF-κB signaling

Ovarian tumor domain-containing protease 1 (OTUD1) is a critical negative regulator that promotes innate immune homeostasis and is extensively involved in the pathogenesis of sepsis. In this study, we performed a powerful integration of multiomics analysis and an experimental mechanistic investigation to elucidate the immunoregulatory role of OTUD1 in sepsis at the clinical, animal and cellular levels. Our study revealed the upregulation of OTUD1 expression and the related distinctive alterations observed via multiomics profiling in clinical and experimental sepsis. Importantly, in vivo and in vitro, OTUD1 was shown to negatively regulate inflammatory responses and play a protective role in sepsis-induced pathological lung injury by mechanistically inhibiting the activation of the transforming growth factor-beta-activated kinase 1 (TAK1)-mediated mitogen-activated protein kinase (MAPK) and nuclear factor kappa-B (NF-κB) signaling pathways in the present study. Subsequently, we probed the molecular mechanisms underlying OTUD1's regulation of NF-κB and MAPK pathways by pinpointing the target proteins that OTUD1 can deubiquitinate. Drawing upon prior research conducted in our laboratory, it has been demonstrated that tumor necrosis factor-α-induced protein 8-like 2 (TIPE2) performs a protective function in septic lung injury and septic encephalopathy by suppressing the NF-κB and MAPK pathways. Hence, we hypothesized that TIPE2 might be a target protein of OTUD1. Additional experiments, including Co-IP, immunofluorescence co-localization, and Western blotting, revealed that OTUD1 indeed has the ability to deubiquitinate TIPE2. In summary, OTUD1 holds potential as an immunoregulatory and inflammatory checkpoint agent, and could serve as a promising therapeutic target for sepsis-induced lung injury.