Human RIPK3 maintains MLKL in an inactive conformation prior to cell death by necroptosis

• Published in: Nature communications Vol. 12; no. 1; p. 6783
• Main Authors: Meng, Yanxiang, Davies, Katherine A., Fitzgibbon, Cheree, Young, Samuel N., Garnish, Sarah E., Horne, Christopher R., Luo, Cindy, Garnier, Jean-Marc, Liang, Lung-Yu, Cowan, Angus D., Samson, Andre L., Lessene, Guillaume, Sandow, Jarrod J., Czabotar, Peter E., Murphy, James M.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 22.11.2021; Nature Publishing Group; Nature Portfolio
• Subjects: 631/45/275; 631/535/1266; 631/80/82/2344; 82/80; 82/83; 96; Animals; Apoptosis; Cell death; Cell Death - genetics; Cell Death - physiology; Conformation; Crystal structure; HT29 Cells; Humanities and Social Sciences; Humans; Inflammatory diseases; Kinases; Mice; Mortality; multidisciplinary; Necroptosis; Necroptosis - genetics; Necroptosis - physiology; Phosphorylation; Protein Conformation; Protein Interaction Domains and Motifs; Protein Kinases - chemistry; Protein Kinases - genetics; Protein Kinases - metabolism; Receptor-Interacting Protein Serine-Threonine Kinases - chemistry; Receptor-Interacting Protein Serine-Threonine Kinases - genetics; Receptor-Interacting Protein Serine-Threonine Kinases - metabolism; Recombinant Proteins; Science; Science (multidisciplinary); Signal Transduction; Upstream
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-021-27032-x

The ancestral origins of the lytic cell death mode, necroptosis, lie in host defense. However, the dysregulation of necroptosis in inflammatory diseases has led to widespread interest in targeting the pathway therapeutically. This mode of cell death is executed by the terminal effector, the MLKL pseudokinase, which is licensed to kill following phosphorylation by its upstream regulator, RIPK3 kinase. The precise molecular details underlying MLKL activation are still emerging and, intriguingly, appear to mechanistically-diverge between species. Here, we report the structure of the human RIPK3 kinase domain alone and in complex with the MLKL pseudokinase. These structures reveal how human RIPK3 structurally differs from its mouse counterpart, and how human RIPK3 maintains MLKL in an inactive conformation prior to induction of necroptosis. Residues within the RIPK3:MLKL C-lobe interface are crucial to complex assembly and necroptotic signaling in human cells, thereby rationalizing the strict species specificity governing RIPK3 activation of MLKL. The pseudokinase MLKL is activated by the upstream kinase RIPK3 in the necroptotic pathway but the structural basis of MLKL activation is not well understood yet. Here, the authors present the crystal structures of the human RIPK3:MLKL complex and human RIPK3 kinase alone, which reveal structural differences between human and murine RIPK3 and they discuss mechanistic implications.