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A dominant autoinflammatory disease caused by non-cleavable variants of RIPK1
Panfeng Tao1, Jinqiao Sun2, Zheming Wu3
1The MOE Key Laboratory of Biosystems Homeostasis & Protection, Life Sciences Institute, Zhejiang University, Hangzhou, China.
Abstract:
Activation of RIPK1 controls TNF-mediated apoptosis, necroptosis and inflammatory pathways1. Cleavage of human and mouse RIPK1 after residues D324 and D325, respectively, by caspase-8 separates the RIPK1 kinase domain from the intermediate and death domains. The D325A mutation in mouse RIPK1 leads to embryonic lethality during mouse development2,3. However, the functional importance of blocking caspase-8-mediated cleavage of RIPK1 on RIPK1 activation in humans is unknown. Here we identify two families with variants in RIPK1 (D324V and D324H) that lead to distinct symptoms of recurrent fevers and lymphadenopathy in an autosomal-dominant manner. Impaired cleavage of RIPK1 D324 variants by caspase-8 sensitized patients' peripheral blood mononuclear cells to RIPK1 activation, apoptosis and necroptosis induced by TNF. The patients showed strong RIPK1-dependent activation of inflammatory signalling pathways and overproduction of inflammatory cytokines and chemokines compared with unaffected controls. Furthermore, we show that expression of the RIPK1 mutants D325V or D325H in mouse embryonic fibroblasts confers not only increased sensitivity to RIPK1 activation-mediated apoptosis and necroptosis, but also induction of pro-inflammatory cytokines such as IL-6 and TNF. By contrast, patient-derived fibroblasts showed reduced expression of RIPK1 and downregulated production of reactive oxygen species, resulting in resistance to necroptosis and ferroptosis. Together, these data suggest that human non-cleavable RIPK1 variants promote activation of RIPK1, and lead to an autoinflammatory disease characterized by hypersensitivity to apoptosis and necroptosis and increased inflammatory response in peripheral blood mononuclear cells, as well as a compensatory mechanism to protect against several pro-death stimuli in fibroblasts.
Insights
Genetic variants in RIPK1 (Receptor-Interacting Protein Kinase 1) impairing caspase-8 cleavage cause autoinflammatory disease. This leads to increased RIPK1 activation, hypersensitivity to cell death, and heightened inflammatory responses.
Area of Science:
- Cellular Biology
- Immunology
- Genetics
Background:
- Receptor-Interacting Protein Kinase 1 (RIPK1) activation regulates TNF-mediated apoptosis, necroptosis, and inflammation.
- Caspase-8 cleavage of RIPK1 separates its kinase domain from other functional domains.
- The role of impaired RIPK1 cleavage in human autoinflammatory diseases was previously unknown.
Purpose of the Study:
- To investigate the functional consequences of impaired caspase-8-mediated RIPK1 cleavage in humans.
- To identify genetic variants in RIPK1 associated with autoinflammatory conditions.
- To elucidate the molecular mechanisms underlying RIPK1-driven inflammation and cell death.
Main Methods:
- Genetic analysis of families with recurrent fevers and lymphadenopathy.
- Functional assays using patient-derived peripheral blood mononuclear cells and fibroblasts.
- In vitro studies involving RIPK1 mutant expression in mouse embryonic fibroblasts.
- Analysis of RIPK1 activation, apoptosis, necroptosis, and inflammatory cytokine production.
Main Results:
- Identified RIPK1 variants (D324V, D324H) causing autosomal-dominant autoinflammatory disease due to impaired caspase-8 cleavage.
- Patient cells exhibited increased RIPK1 activation, hypersensitivity to TNF-induced apoptosis and necroptosis, and elevated inflammatory cytokine/chemokine production.
- RIPK1 mutants in mouse cells showed increased sensitivity to apoptosis/necroptosis and induced pro-inflammatory cytokines.
- Patient fibroblasts displayed reduced RIPK1 expression and ROS production, conferring resistance to necroptosis and ferroptosis.
Conclusions:
- Human non-cleavable RIPK1 variants promote RIPK1 activation, leading to autoinflammatory disease.
- The disease is characterized by hypersensitivity to apoptosis and necroptosis and heightened inflammatory responses.
- A compensatory mechanism in patient fibroblasts protects against certain pro-death stimuli.
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