1. Oligomerization‐driven MLKL ubiquitylation antagonizes necroptosis
- Author
-
Michelle Tang, Aleksandra Bankovacki, Samuel N. Young, Che A. Stafford, Sarah E Garnish, Joanne M Hildebrand, Ueli Nachbur, Cheree Fitzgibbon, Kristy Shield-Artin, John Silke, James M. Murphy, Zikou Liu, Jason Howitt, Andrew I. Webb, David Komander, Xiangyi Wang, and Laura F. Dagley
- Subjects
Proteasome Endopeptidase Complex ,Programmed cell death ,Necroptosis ,Protein aggregation ,General Biochemistry, Genetics and Molecular Biology ,Serine ,Mice ,Ubiquitin ,Animals ,Phosphorylation ,Protein kinase A ,Molecular Biology ,Mice, Knockout ,General Immunology and Microbiology ,biology ,General Neuroscience ,Cell Membrane ,Ubiquitination ,Articles ,Cell biology ,Mice, Inbred C57BL ,Proteasome ,biology.protein ,Protein Multimerization ,Protein Kinases ,Ubiquitin Thiolesterase - Abstract
Mixed lineage kinase domain‐like (MLKL) is the executioner in the caspase‐independent form of programmed cell death called necroptosis. Receptor‐interacting serine/threonine protein kinase 3 (RIPK3) phosphorylates MLKL, triggering MLKL oligomerization, membrane translocation and membrane disruption. MLKL also undergoes ubiquitylation during necroptosis, yet neither the mechanism nor the significance of this event has been demonstrated. Here, we show that necroptosis‐specific multi‐mono‐ubiquitylation of MLKL occurs following its activation and oligomerization. Ubiquitylated MLKL accumulates in a digitonin‐insoluble cell fraction comprising organellar and plasma membranes and protein aggregates. Appearance of this ubiquitylated MLKL form can be reduced by expression of a plasma membrane‐located deubiquitylating enzyme. Oligomerization‐induced MLKL ubiquitylation occurs on at least four separate lysine residues and correlates with its proteasome‐ and lysosome‐dependent turnover. Using a MLKL‐DUB fusion strategy, we show that constitutive removal of ubiquitin from MLKL licences MLKL auto‐activation independent of necroptosis signalling in mouse and human cells. Therefore, in addition to the role of ubiquitylation in the kinetic regulation of MLKL‐induced death following an exogenous necroptotic stimulus, it also contributes to restraining basal levels of activated MLKL to avoid unwanted cell death.
- Published
- 2021