| First Author | Rodriguez DA | Year | 2022 |
| Journal | Proc Natl Acad Sci U S A | Volume | 119 |
| Issue | 41 | Pages | e2207240119 |
| PubMed ID | 36191211 | Mgi Jnum | J:353327 |
| Mgi Id | MGI:7461066 | Doi | 10.1073/pnas.2207240119 |
| Citation | Rodriguez DA, et al. (2022) Caspase-8 and FADD prevent spontaneous ZBP1 expression and necroptosis. Proc Natl Acad Sci U S A 119(41):e2207240119 |
| abstractText | The absence of Caspase-8 or its adapter, Fas-associated death domain (FADD), results in activation of receptor interacting protein kinase-3 (RIPK3)- and mixed-lineage kinase-like (MLKL)-dependent necroptosis in vivo. Here, we show that spontaneous activation of RIPK3, phosphorylation of MLKL, and necroptosis in Caspase-8- or FADD-deficient cells was dependent on the nucleic acid sensor, Z-DNA binding protein-1 (ZBP1). We genetically engineered a mouse model by a single insertion of FLAG tag onto the N terminus of endogenous MLKL (Mlkl(FLAG/FLAG)), creating an inactive form of MLKL that permits monitoring of phosphorylated MLKL without activating necroptotic cell death. Casp8(-/-)Mlkl(FLAG/FLAG) mice were viable and displayed phosphorylated MLKL in a variety of tissues, together with dramatically increased expression of ZBP1 compared to Casp8(+/+) mice. Studies in vitro revealed an increased expression of ZBP1 in cells lacking FADD or Caspase-8, which was suppressed by reconstitution of Caspase-8 or FADD. Ablation of ZBP1 in Casp8(-/-)Mlkl(FLAG/FLAG) mice suppressed spontaneous MLKL phosphorylation in vivo. ZBP1 expression and downstream activation of RIPK3 and MLKL in cells lacking Caspase-8 or FADD relied on a positive feedback mechanism requiring the nucleic acid sensors cyclic GMP-AMP synthase (cGAS), stimulator of interferon genes (STING), and TBK1 signaling pathways. Our study identifies a molecular mechanism whereby Caspase-8 and FADD suppress spontaneous necroptotic cell death. |
