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Distinct pseudokinase domain conformations underlie divergent activation mechanisms among vertebrate MLKL orthologues

Katherine A Davies1,2, Cheree Fitzgibbon1, Samuel N Young1

  • 1Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, VIC, 3052, Australia.

Nature Communications
|June 21, 2020
PubMed

Insights

The MLKL pseudokinase, a key player in necroptosis, shows species-specific activation. Mouse and human RIPK3 selectively activate their own MLKL, highlighting evolutionary differences in cell death pathways.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • The mixed lineage kinase domain-like (MLKL) pseudokinase is the terminal effector in the necroptosis pathway.
  • Activation involves phosphorylation by RIPK3, leading to MLKL oligomerization, membrane translocation, and cell permeabilization.
  • The precise mechanisms of MLKL activation and their potential species-specific differences remain incompletely understood.

Purpose of the Study:

  • To investigate the divergence of MLKL activation mechanisms across nine vertebrate orthologues.
  • To determine the species specificity of RIPK3-MLKL interactions.
  • To elucidate the structural basis for observed differences in MLKL activation.

Main Methods:

  • Comparative analysis of MLKL orthologues from nine vertebrate species.
  • Functional reconstitution assays to test MLKL activity in heterologous systems.
  • X-ray crystallography to determine the structures of MLKL pseudokinase domains.

Main Results:

  • Mouse and human RIPK3 exhibit remarkable specificity for their cognate MLKL orthologues.
  • Pig MLKL can restore necroptotic signaling in human cells.
  • Horse and pig MLKL, but not rat MLKL, can reconstitute the mouse necroptosis pathway.
  • Distinct conformations of horse and rat MLKL pseudokinase domains correlate with observed activation selectivity.

Conclusions:

  • Significant species-specific differences exist in MLKL activation mechanisms within the necroptosis pathway.
  • Divergent regulatory mechanisms may be a common feature among orthologous pseudoenzymes.
  • Understanding these species-specific differences is crucial for studying necroptosis and developing targeted therapeutics.

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