Necroptosis signalling is tuned by phosphorylation of MLKL residues outside the pseudokinase domain activation loop.
The pseudokinase MLKL (mixed lineage kinase domain-like), has recently emerged as a critical component of the necroptosis cell death pathway. Although it is clear that phosphorylation of the activation loop in the MLKL pseudokinase domain by the upstream protein kinase RIPK3 (receptor-interacting protein kinase-3), is crucial to trigger MLKL activation, it has remained unclear whether other phosphorylation events modulate MLKL function. By reconstituting Mlkl(-/-), Ripk3(-/-) and Mlkl(-/-)Ripk3(-/-) cells with MLKL phospho-site mutants, we compared the function of known MLKL phosphorylation sites in regulating necroptosis with three phospho-sites that we identified by MS, Ser(158), Ser(228) and Ser(248). Expression of a phosphomimetic S345D MLKL activation loop mutant-induced stimulus-independent cell death in all knockout cells, demonstrating that RIPK3 phosphorylation of the activation loop of MLKL is sufficient to induce cell death. Cell death was also induced by S228A, S228E and S158A MLKL mutants in the absence of death stimuli, but was most profound in Mlkl(-/-)Ripk3(-/-) double knockout fibroblasts. These data reveal a potential role for RIPK3 as a suppressor of MLKL activation and indicate that phosphorylation can fine-tune the ability of MLKL to induce necroptosis.
The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia Department of Medical Biology, University of Melbourne, Parkville, Victoria 3050, Australia.
Maria C
MC
Tanzer
The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia Department of Medical Biology, University of Melbourne, Parkville, Victoria 3050, Australia.
Anne
A
Tripaydonis
The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia Department of Medical Biology, University of Melbourne, Parkville, Victoria 3050, Australia.
Andrew I
AI
Webb
The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia.
Samuel N
SN
Young
The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia Department of Medical Biology, University of Melbourne, Parkville, Victoria 3050, Australia.
Leila N
LN
Varghese
The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia.
Cathrine
C
Hall
The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia Department of Medical Biology, University of Melbourne, Parkville, Victoria 3050, Australia.
Warren S
WS
Alexander
The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia Department of Medical Biology, University of Melbourne, Parkville, Victoria 3050, Australia.
Joanne M
JM
Hildebrand
The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia Department of Medical Biology, University of Melbourne, Parkville, Victoria 3050, Australia silke@wehi.edu.au jamesm@wehi.edu.au.
John
J
Silke
The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia Department of Medical Biology, University of Melbourne, Parkville, Victoria 3050, Australia silke@wehi.edu.au jamesm@wehi.edu.au.
James M
JM
Murphy
D019943:Amino Acid Substitution; D000818:Animals; D004789:Enzyme Activation / Q000502:physiology; D055786:Gene Knockout Techniques; D006801:Humans; D051379:Mice; D020125:Mutation, Missense; D010766:Phosphorylation / Q000502:physiology; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D053422:Receptor-Interacting Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D020298:U937 Cells
C570693:MLKL protein, human; C570694:MLKL protein, mouse; D011494:Protein Kinases; C119705:RIPK3 protein, human; D053422:Receptor-Interacting Protein Serine-Threonine Kinases; C485615:Ripk3 protein, mouse
cell death; four-helix bundle domain; phosphomimetic; programmed necrosis; pseudoenzyme; receptor-interacting protein kinase-3 (RIPK3)