MLKL compromises plasma membrane integrity by binding to phosphatidylinositol phosphates

Area of Science:

• Cellular Biology
• Molecular Biology
• Biochemistry

Background:

• Mixed lineage kinase domain-like (MLKL) is a key mediator of necroptosis.
• The precise mechanism by which MLKL signals for cell death is not fully understood.

Purpose of the Study:

• To elucidate the role of MLKL's N-terminal region in necroptosis.
• To investigate how MLKL induces cell death at the molecular level.

Main Methods:

• Investigated the function of MLKL's N-terminal four-helical bundle domain (4HBD).
• Utilized biochemical assays to assess MLKL oligomerization and liposome permeabilization.
• Examined the role of positively charged amino acids in MLKL-membrane interactions.
• Studied the effect of inhibiting phosphatidylinositol phosphate (PIP) synthesis on necroptosis.

Main Results:

• The MLKL 4HBD is necessary and sufficient for MLKL oligomerization and cell death induction.
• A positively charged patch on the 4HBD surface binds to PIPs, recruiting MLKL to the plasma membrane.
• Recombinant MLKL, unlike a charge-mutant, permeabilizes PIP-containing liposomes, similar to BAX.
• Inhibiting PI(5)P and PI(4,5)P2 formation specifically blocks TNF-mediated necroptosis, not apoptosis.

Conclusions:

• MLKL directly permeabilizes the plasma membrane to induce necroptosis.
• PIP binding to MLKL is critical for its recruitment and function in necroptosis.
• Targeting PIP synthesis may offer specific therapeutic strategies for necroptosis.