ASC Pyrin Domain Self-associates and Binds NLRP3 Protein Using Equivalent Binding Interfaces

Area of Science:

• Molecular biology
• Biochemistry
• Cellular signaling

Background:

• Death domain superfamily proteins are crucial adaptors in apoptosis and inflammation.
• These proteins utilize modular domains like pyrin domains (PYD) for complex assembly.
• Homotypic interactions govern complex formation, necessitating the identification of differentiating factors.

Purpose of the Study:

• To elucidate the molecular basis of ASC and NLRP3 PYD interactions.
• To characterize the self-association of ASC PYD and its interaction with NLRP3 PYD.
• To provide structural insights into early supramolecular complex formation.

Main Methods:

• Solution NMR spectroscopy to determine protein structures and binding interactions.
• Analytical ultracentrifugation to analyze oligomerization states.
• Biophysical characterization of ASC PYD self-association and NLRP3 PYD binding.

Main Results:

• ASC PYD self-associates and binds NLRP3 PYD via equivalent protein regions.
• NLRP3 PYD exists as both monomer and large oligomers in solution.
• Higher binding affinity was observed between ASC PYD and NLRP3 PYD compared to ASC PYD self-association.
• Novel structural data enabled the proposal of molecular models for ASC·ASC and ASC·NLRP3 PYD complexes.

Conclusions:

• ASC and NLRP3 PYD interactions are mediated by distinct protein regions, enabling multimeric complex formation.
• The findings offer new molecular insights into the mechanisms of inflammasome and apoptosis signaling.
• Understanding these specific interactions is critical for deciphering the molecular basis of inflammation and cell death pathways.