Dataset Information

Human RIPK3 maintains MLKL in an inactive conformation prior to cell death by necroptosis.

ABSTRACT: The ancestral origins of the lytic cell death mode, necroptosis, lie in host defense. However, the dysregulation of necroptosis in inflammatory diseases has led to widespread interest in targeting the pathway therapeutically. This mode of cell death is executed by the terminal effector, the MLKL pseudokinase, which is licensed to kill following phosphorylation by its upstream regulator, RIPK3 kinase. The precise molecular details underlying MLKL activation are still emerging and, intriguingly, appear to mechanistically-diverge between species. Here, we report the structure of the human RIPK3 kinase domain alone and in complex with the MLKL pseudokinase. These structures reveal how human RIPK3 structurally differs from its mouse counterpart, and how human RIPK3 maintains MLKL in an inactive conformation prior to induction of necroptosis. Residues within the RIPK3:MLKL C-lobe interface are crucial to complex assembly and necroptotic signaling in human cells, thereby rationalizing the strict species specificity governing RIPK3 activation of MLKL.

SUBMITTER: Meng Y

PROVIDER: S-EPMC8608796 | biostudies-literature | 2021 Nov

REPOSITORIES: biostudies-literature

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Human RIPK3 maintains MLKL in an inactive conformation prior to cell death by necroptosis.

Meng Yanxiang Y Davies Katherine A KA Fitzgibbon Cheree C Young Samuel N SN Garnish Sarah E SE Horne Christopher R CR Luo Cindy C Garnier Jean-Marc JM Liang Lung-Yu LY Cowan Angus D AD Samson Andre L AL Lessene Guillaume G Sandow Jarrod J JJ Czabotar Peter E PE Murphy James M JM

Nature communications 20211122 1

The ancestral origins of the lytic cell death mode, necroptosis, lie in host defense. However, the dysregulation of necroptosis in inflammatory diseases has led to widespread interest in targeting the pathway therapeutically. This mode of cell death is executed by the terminal effector, the MLKL pseudokinase, which is licensed to kill following phosphorylation by its upstream regulator, RIPK3 kinase. The precise molecular details underlying MLKL activation are still emerging and, intriguingly, a ...[more]

PMID: 34811356

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Project description:Necroptosis is a pro-inflammatory cell death, which happens in the context of caspase-8 inhibition, allowing activation of the receptor interacting protein kinase 1-receptor interacting protein kinase 3-mixed lineage kinase domain-like (RIPK1-RIPK3-MLKL) axis. Recently, necroptosis has emerged as a key component of resistance against pathogens including infected macrophage by Leishmania infantum, the ethiologic agent of Visceral leishmaniasis (VL). VL is the most severe form of Leishmaniasis, characterized by systemic inflammation and neutropenia. However, the role of neutrophil cell death in VL has not been characterized. Here, we showed that VL patients exhibited increased lactate dehydrogenase levels in the serum, a hallmark of cell death and tissue damage. We investigated the effect of necroptosis in neutrophil infection in vitro. Human neutrophils pretreated with zVAD-fmk (pan-caspase inhibitor) and zIETD-fmk (caspase-8 inhibitor) increased reactive oxygen species (ROS) level in response to Leishmania infection, which is associated with necroptotic cell death. MLKL, an important effector molecule downstream of necroptosis pathway, was also required for Leishmania killing. Moreover, in absence of caspases-8, murine neutrophils displayed loss of membrane integrity, higher levels of ROS, and decreased L. infantum viability. Pharmacological inhibition of RIPK1 or RIPK3 increased parasite survival when caspase-8 was blocked. Electron microscopy assays revealed morphological features associated with necroptotic death in L. infantum infected-neutrophils pretreated with caspase inhibitor, whereas infected cells pretreated with RIPK1 and RIPK3 inhibitors did not show ultra-structural alterations in membrane integrity and presented viable Leishmania within parasitophorous vacuoles. Taken together, these findings suggest that inhibition of caspase-8 contributes to elimination of L. infantum in neutrophils by triggering necroptosis. Thus, targeting necroptosis may represent a new strategy to control Leishmania replication.

Dataset Information

Human RIPK3 maintains MLKL in an inactive conformation prior to cell death by necroptosis.

Publications

Human RIPK3 maintains MLKL in an inactive conformation prior to cell death by necroptosis.

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