[^1]
- Gene: [CYBB](/genes/cybb)
[^2]
- Aliases: gp91phox, NOX2
[^3]
- UniProt: [P04839](https://www.uniprot.org/uniprot/P04839)
- Molecular Weight: ~65 kDa
- Subcellular Location: Plasma membrane, phagosome membrane
- PDB Structures: [5OGEN](https://www.rcsb.org/structure/5OGEN), [3A1F](https://www.rcsb.org/structure/3A1F)
NOX2 (NADPH oxidase 2) is the catalytic subunit of the phagocyte NADPH oxidase complex, responsible for the respiratory burst that destroys pathogens. Beyond immune defense, NOX2 generates reactive oxygen species (ROS) as signaling molecules in various cell types. In the brain, microglial and neuronal NOX2 contribute to oxidative stress and neuroinflammation in neurodegenerative diseases.
NOX2 is a transmembrane glycoprotein requiring assembly with regulatory subunits:
- N-terminal transmembrane domain: Six membrane-spanning helices
- Heme-binding sites: Two bis-histidine-coordinated hemes
- FAD-binding domain: Binds flavin adenine dinucleotide
- NADPH-binding domain: Cytoplasmic, electron donor site
- Glycosylation sites: Multiple N-linked glycans
The active complex requires p22phox (membrane subunit) and cytosolic factors (p47phox, p67phox, p40phox, Rac).
In immune cells, NOX2 generates superoxide for pathogen killing:
NADPH + 2 O2 -> NADP+ + 2 O2- + H+
This leads to:
- Direct microbial killing: Superoxide and derivatives
- pH regulation: Alkalinization of phagosomes
- Protease activation: Optimal pH for digestive enzymes
In the CNS, NOX2 has physiological roles:
- Synaptic plasticity: ROS modulate NMDA receptor function
- Long-term potentiation: Low ROS levels enhance LTP
- Neuronal signaling: Redox-sensitive signaling pathways
- Microglial surveillance: Low-level ROS production
NOX2 expression in brain:
- Microglia: Highest expression, activated by inflammatory stimuli
- Neurons: Lower expression, activity-dependent
- Astrocytes: Inducible expression
- Endothelial cells: BBB function
NOX2 contributes to AD pathology through multiple mechanisms:
- Microglial activation: Abeta activates microglial NOX2
- ROS production: Superoxide and derived oxidants
- Neuroinflammation: ROS amplify inflammatory cascades
- Abeta aggregation: ROS promote amyloidogenic processing
- Neuronal damage: Oxidative injury to synapses
Evidence:
- Increased NOX2 expression in AD brains
- NOX2 knockout reduces pathology in AD mouse models
- Correlation between NOX2 and cognitive decline
Dopaminergic neuron vulnerability involves NOX2:
- Microglial activation: alpha-synuclein activates microglia
- Nigral ROS: High oxidative stress in substantia nigra
- Dopamine oxidation: Synergizes with NOX2-derived ROS
- Mitochondrial dysfunction: NOX2 ROS damage mitochondria
- Neuron-glia interactions: Microglial NOX2 kills dopaminergic neurons
Motor neuron disease and NOX2:
- Microglial activation: Reactive microglia in motor cortex
- SOD1 interaction: SOD1 mutants increase NOX2 activity
- Motor neuron death: ROS-mediated apoptosis/necrosis
- Disease progression: NOX2 correlates with progression rate
¶ Stroke and Ischemia
Acute brain injury:
- Reperfusion injury: NOX2-generated ROS during reperfusion
- BBB breakdown: ROS increase permeability
- Inflammatory amplification: NOX2 perpetuates inflammation
- Delayed neuronal death: ROS contribute to penumbra damage
Demyelination and oxidative stress:
- Activated microglia: NOX2 in lesions
- Oligodendrocyte damage: ROS damage myelin-producing cells
- Axonal injury: Oxidative damage to axons
- Progressive MS: NOX2 contributes to neurodegeneration
Compounds in development:
- GSK2795039: Selective NOX2 inhibitor
- Apocynin: Natural compound, NOX2 assembly inhibitor
- VAS2870: Pan-NOX inhibitor
- Peptide inhibitors: Block subunit assembly
Combination approaches:
- N-acetylcysteine: Boost glutathione
- MitoQ: Mitochondria-targeted antioxidant
- Edaravone: Free radical scavenger (FDA-approved for ALS)
Targeting upstream activation:
- Microglial modulators: Reduce NOX2 induction
- TNF inhibitors: Block inflammatory cascade
- Complement inhibitors: Reduce microglial activation
NOX2-targeted approaches in clinical testing:
- Stroke trials: NOX2 inhibitors in acute stroke
- Neurodegeneration: Preclinical efficacy demonstrated
- Biomarker development: Oxidative stress markers
| Interactor |
Relationship |
Functional Relevance |
| p22phox |
Membrane subunit |
Required for NOX2 stability |
| p47phox |
Cytosolic organizer |
Assembly and activation |
| p67phox |
Cytosolic activator |
Direct activation domain |
| Rac |
Small GTPase |
Essential for activity |
| Nrf2 |
Antioxidant response |
Counteracts NOX2 ROS |
- UniProt - Protein sequence and functional data
- PubMed - Biomedical literature
- PDB - Protein structure data