Ubiquitin-binding domain in ABIN1 is critical for regulating cell death and inflammation during development

Abstract

ABIN1 is a polyubiquitin-binding protein known to regulate NF-κB activation and cell death signaling. Mutations in Abin1 can cause severe immune diseases in human, such as psoriasis, systemic lupus erythematosus, and systemic sclerosis. Here, we generated mice that disrupted the ubiquitin-binding domain of ABIN1 (Abin1^UBD/UBD) died during later embryogenesis owing to TNFR1-mediated cell death, similar to Abin1^-/- mice. Abin1^UBD/UBD cells were rendered sensitive to TNF-α-induced apoptosis and necroptosis as the inhibition of ABIN1^UBD and A20 recruitment to the TNF-RSC complex leads to attenuated RIPK1 deubiquitination. Accordingly, the embryonic lethality of Abin1^UBD/UBD mice was rescued via crossing with RIPK1 kinase-dead mice (Ripk1^K45A/K45A) or the co-deletion of Ripk3 and one allele of Fadd, but not by the loss of Ripk3 or Mlkl alone. Unexpectedly, Abin1^UBD/UBD mice with the co-deletion of Ripk3 and both Fadd alleles died at E14.5. This death was caused by spontaneous RIPK1 ubiquitination-dependent multiple inflammatory cytokines over production and could be rescued by the co-deletion of Ripk1 or Tnfr1 combined with Ifnar. Collectively, these data demonstrate the importance of the ABIN1 UBD domain, which mediates the ABIN1-A20 axis, at limiting RIPK1 activation-dependent cell death during embryonic development. Furthermore, our findings reveal a previously unappreciated ubiquitin pathway that regulates RIPK1 ubiquitination by FADD/Casp8 to suppress spontaneous IKKε/TBK1 activation.