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Mol Cell Biol. 2017 Feb 15;37(5). pii: e00497-16. doi: 10.1128/MCB.00497-16. Print 2017 Mar 1.

The MLKL Channel in Necroptosis Is an Octamer Formed by Tetramers in a Dyadic Process.

Author information

1
State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Signaling Network, School of Life Sciences, Xiamen University, Xiamen, Fujian, China.
2
Life Sciences Institute and Innovation Center for Cell Signaling Network, Zhejiang University, Hangzhou, Zhejiang, China.
3
State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Signaling Network, School of Life Sciences, Xiamen University, Xiamen, Fujian, China jhan@xmu.edu.cn.

Abstract

Oligomerization of the mixed-lineage kinase domain-like protein (MLKL) is essential for its cation channel function in necroptosis. Here we show that the MLKL channel is an octamer comprising two previously identified tetramers most likely in their side-by-side position. Intermolecule disulfide bonds are present in the tetramer but are not required for octamer assembly and necroptosis. MLKL forms oligomers in the necrosome and is then released from the necrosome before or during its membrane translocation. We identified two MLKL mutants that could not oligomerize into octamers, although they formed a tetramer, and also, one MLKL mutant could spontaneously form a disulfide bond-linked octamer. Subsequent analysis revealed that the tetramers fail to translocate to the plasma membrane and that the MLKL octamer formation depends on α-helices 4 and 5. While MLKL could be detected from outside the cells, its N- and C-terminal ends could not be detected, indicating that the MLKL octamer spans across the plasma membrane, leaving its N and C termini inside the cell. These data allowed us to propose a 180° symmetry model of the MLKL octamer and conclude that the fully assembled MLKL octamers, but not the previously described tetramers, act as effectors of necroptosis.

KEYWORDS:

MLKL; channel; necroptosis; octamer

PMID:
27920255
PMCID:
PMC5311246
DOI:
10.1128/MCB.00497-16
[Indexed for MEDLINE]
Free PMC Article

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