Oral Communications Autoinflammation

CLEAVAGE-RESISTANT RIPK1 MUTATIONS CAUSE AUTOINFLAMMATION

Lecture Time
11:10 - 11:20
Presenter
  • Hirotsugu Oda, United States of America
Room
Gold
Date
20.09.2019, Friday
Session Time
11:00 - 12:40
Presentation Topic
Autoinflammation

Abstract

Background and Aims

Receptor interacting protein kinase 1 (RIPK1) is a critical regulator of immune signaling pathways. Human RIPK1 deficiency has been associated with periodic fever, recurrent infections, arthritis and inflammatory bowel disease, and its pathogenesis has been attributed to attenuated NF-κB activity, dysregulated cell death pathways and increased inflammasome activity. Human RIPK1 is cleaved by caspase protease at p.D324 in vitro; however, the physiological relevance of this cleavage remains to be unclear.

Methods

By whole exome sequencing, we studied the genetic cause of seven individuals from three pedigrees with infantile-onset periodic fever and systemic lymphadenopathy, but without immunodeficiency.

Results

We identified novel heterozygous missense variants (p.D324N, p.D324H and p.D324Y) affecting the caspase cleavage site in affected individuals. In vitrostudies confirmed that these RIPK1 mutations are resistant to cleavage by caspase-6 and caspase-8. Patient derived PBMCs were hyper-responsive to LPS stimulation ex vivo. To further study the mechanism of this disease we generated a cleavage-resistant Rikp1D325A mutant mouse strain. Rikp1D325A/ D325Amice demonstrated embryonic lethality, due to vasculature formation. Embryonic lethality was rescued by combined loss of Casp8 and Ripk3 implicating cell death program in lethality. Rikp1D325A/ D325A and Rikp1D325A/+ MEFs and BMDMs demonstrated enhanced TNF-induced apoptosis and necroptosis. Importantly, similar to our patients heterozygous Rikp1D325A/+mice were viable and demonstrated hyper-responsiveness to inflammatory stimuli in vivo.

Conclusions

Our results reveal the importance of caspase-mediated RIPK1 cleavage for maintenance of inflammation in humans and mice. We designated this novel human disease as ‘Cleavage-resistant RIPK1-Induced Autoinflammatory syndrome’ (CRIA syndrome).

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