MLKL Requires the Inositol Phosphate Code to Execute Necroptosis.

Area of Science:

• Cellular Biology
• Biochemistry
• Immunology

Background:

• Necroptosis is a critical lytic cell death pathway activated by injury and infection.
• The precise role of mixed lineage kinase domain-like (MLKL) in executing necroptosis remains incompletely understood.

Purpose of the Study:

• To investigate the sufficiency of MLKL in driving necroptosis.
• To identify genetic factors regulating MLKL-dependent necroptosis.

Main Methods:

• Genetic screening in human cells to identify mutants defective in MLKL-dependent necroptosis.
• Analysis of inositol phosphate (IP) kinase function in regulating necroptosis.
• Investigating MLKL oligomerization, membrane localization, and phosphorylation in IP kinase mutant cells.

Main Results:

• Mutations in inositol phosphate (IP) kinases (IPMK and ITPK1) were found to impair MLKL-dependent necroptosis.
• IP kinases are essential for necroptosis induced by various stimuli, including death receptor activation and viral infection.
• In IP kinase-deficient cells, MLKL failed to oligomerize and localize to membranes, despite correct phosphorylation by RIPK3.
• Necroptosis is dependent on IP-specific kinase activity, with a highly phosphorylated product displacing MLKL's auto-inhibitory region.

Conclusions:

• Metabolites, specifically inositol phosphates regulated by IP kinases, play a crucial role in controlling MLKL-mediated necroptosis.
• This study elucidates a key molecular mechanism by which regulated cell death is controlled through metabolic regulation of MLKL activation.