Dominant negative OTULIN-related autoinflammatory syndrome

Area of Science:

• Molecular Biology
• Immunology
• Genetics

Background:

• OTU deubiquitinase with linear linkage specificity (OTULIN) is crucial for regulating inflammation and cell death by removing linear ubiquitin chains.
• OTULIN-related autoinflammatory syndrome (ORAS) is typically caused by biallelic loss-of-function mutations in OTULIN.
• OTULIN haploinsufficiency has not been previously linked to spontaneous inflammatory conditions.

Purpose of the Study:

• To investigate the role of a heterozygous OTULIN mutation (p.Cys129Ser) in two patients presenting with autoinflammatory symptoms.
• To elucidate the molecular mechanisms by which the p.Cys129Ser mutation contributes to disease pathology.
• To expand the clinical and genetic understanding of OTULIN-associated autoinflammatory disorders.

Main Methods:

• Analysis of patient-derived cells to assess linear ubiquitin chain accumulation, TNF-induced cell death sensitivity, and inflammatory signaling.
• Biochemical assays to evaluate the impact of the p.Cys129Ser mutation on OTULIN protein stability, LUBAC binding, and deubiquitinase activity.
• Investigation of LUBAC ubiquitination status and its recruitment to the TNF receptor signaling complex.

Main Results:

• Patient cells exhibited accumulation of linear ubiquitin chains, heightened sensitivity to TNF-induced cell death, and dysregulated inflammatory signaling.
• The p.Cys129Ser mutation did not affect OTULIN protein stability or its binding to LUBAC and linear ubiquitin chains.
• The mutation abolished OTULIN's deubiquitinase activity, leading to autoubiquitin chain accumulation on LUBAC.
• Altered LUBAC ubiquitination impaired its recruitment to the TNF receptor signaling complex, promoting cell death and disease.

Conclusions:

• The p.Cys129Ser mutation in OTULIN represents the first identified dominant negative mutation causing ORAS.
• This heterozygous mutation leads to autoinflammatory pathology through impaired OTULIN deubiquitinase activity and subsequent LUBAC dysregulation.
• The findings broaden the spectrum of genetic causes for ORAS and highlight the critical role of OTULIN activity in maintaining immune homeostasis.