Quantitative interaction analysis permits molecular insights into functional NOX4 NADPH oxidase heterodimer assembly

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Quantifying functional assembly of multipass membrane protein complexes in their native environment remains a significant challenge.
• NADPH oxidase 4 (NOX4)-p22^phox is an integral membrane enzyme crucial for reactive oxygen species (ROS) generation, but its structure and assembly are not fully understood.

Purpose of the Study:

• To develop and apply a novel, quantitative method for probing the assembly of the NOX4-p22^phox complex.
• To identify key determinants governing the interaction between NOX4 and p22^phox and their impact on enzyme function.

Main Methods:

• Utilized a split-luciferase-based approach combined with modeling-assisted protein modification and human disease variant data.
• Investigated heterodimerization, protein trafficking, and catalytic activity of the NOX4-p22^phox complex.
• Analyzed the role of heme incorporation and specific p22^phox residues in NOX4 maturation and ROS production.

Main Results:

• Identified critical determinants for NOX4-p22^phox interaction, including heme incorporation into NOX4 and specific hot spot residues in p22^phox transmembrane domains.
• Demonstrated the method's ability to assess the impact of these interactions on NOX4 maturation and ROS generation.
• Validated the quantitative and reversible nature of the split-fragment protein-protein interaction technique.

Conclusions:

• The developed split-luciferase method provides a powerful tool for studying intricate membrane protein complex assembly, applicable to NOX research and beyond.
• Understanding NOX4-p22^phox interactions offers insights into ROS generation mechanisms and potential therapeutic strategies for NOX-associated diseases.
• This protein engineering approach facilitates the discovery of novel drug targets for managing diseases linked to NOX enzymes.