Inflammasome sensor NLRP1 disease variant M1184V promotes autoproteolysis and DPP9 complex formation by stabilizing...

Area of Science:

• Immunology
• Molecular Biology
• Structural Biology

Background:

• The inflammasome sensor NLRP1 (nucleotide-binding oligomerization domain-like receptor containing a pyrin domain 1) is crucial for innate immunity, initiating inflammatory responses via pyroptosis and cytokine release.
• NLRP1 mutations are linked to autoinflammatory diseases, highlighting the importance of understanding its regulation.
• The common NLRP1 M1184V variant is associated with asthma, inflammatory bowel disease, and diabetes.

Purpose of the Study:

• To investigate the functional impact of the common NLRP1 M1184V variant on protein stability and interactions.
• To elucidate the molecular mechanisms underlying the association of NLRP1 M1184V with various autoinflammatory conditions.

Main Methods:

• Size-exclusion chromatography to assess protein conformation.
• Molecular dynamics simulations to analyze domain flexibility.
• Surface plasmon resonance and immunoprecipitation assays to determine binding affinities.
• Enzyme activity assays to evaluate complex formation.

Main Results:

• The M1184V variant stabilizes the FIIND domain in a monomeric state, independent of autoproteolysis.
• Valine at position 1184 reduces ZU5 domain flexibility, potentially stabilizing the catalytic triad.
• Monomeric FIIND domain promotes full-length NLRP1 multimerization.
• The M1184V variant enhances binding affinity for dipeptidyl peptidase 9 (DPP9) to both FIIND and full-length NLRP1.
• Increased DPP9 binding was confirmed in cellular models, indicating improved formation of an autoinhibited complex.

Conclusions:

• The M1184V variant's stabilization of the FIIND domain and enhanced DPP9 binding provide a molecular basis for its involvement in autoimmune syndromes.
• Understanding NLRP1 variant function is critical for deciphering the pathogenesis of autoinflammatory diseases.