Chemical thermodynamic principles and computational modeling of NOX2-mediated ROS production on cell membrane

Reactive oxygen species (ROS) play an important role in physiological processes, such as cell signaling, growth, and immunity. However, ROS overproduction leads to oxidative stress and cell injury/death, which is a major factor in a myriad of pathologies, including cardiovascular and renal diseases. The major nonmitochondrial source of ROS in many cell types is the family of NADPH oxidase (NOX) enzymes. NOX2 is the most widely expressed and well-studied NOX isoform comprising several cell membrane and cytosolic subunits, which when assembled and activated on the cell membrane facilitate electron transfer from NADPH to O2 via different redox centers of the NOX2 complex resulting in superoxide (O2•−) production. However, the field has lacked an integrated computational model for mechanistic and quantitative understanding of the kinetics of NOX2 assembly, activation, electron transfer, and O2•− production, and their regulations by pH, drugs, and other regulatory factors. Recently, we have developed two independent models: one for NOX2 assembly and activation on the cell membrane and its regulations by different regulatory factors facilitating O2•− production, and another for NOX2 complex-mediated electron transfer and O2•− production, and its regulations by pH and drugs. However, these models separately are not able to relate changes in NOX2 assembly and activation to changes in NOX2 complex-mediated electron transfer and O2•− production and vice versa. Here, we describe an integrated computational model enabling analysis of the crosstalk between NOX2 assembly and activation with NOX2 complex-mediated electron transfer and O2•− production. The resulting model provides a mechanistic and quantitative framework for an integrated understanding of the kinetics and regulations of NOX2 assembly, activation, electron transfer, and O2•− production, enabling the simulation of diverse experimental data under physiological and pathological conditions.