NOS2 - Nitric Oxide Synthase 2

NOS2 Gene

Pathway Diagram

Introduction

Nos2 Nitric Oxide Synthase 2 is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

NOS2 Gene

Pathway Diagram

Introduction

Nos2 Nitric Oxide Synthase 2 is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

<div class="infobox infobox-gene"> [@aktan2004]
<table> [@stewart2000]
<tr><th colspan="2" style="background:#f0f0f0;">Gene Overview</th></tr> [@huang2020]
<tr><td><strong>Gene Symbol</strong></td><td>NOS2</td></tr> [@xie1992]
<tr><td><strong>Full Name</strong></td><td>Nitric Oxide Synthase 2</td></tr> [@guix2021]
<tr><td><strong>Chromosomal Location</strong></td><td>17q11.2</td></tr> [@liu2023]
<tr><td><strong>Protein Product</strong></td><td>Inducible Nitric Oxide Synthase (iNOS)</td></tr> [@saha2019]
<tr><td><strong>Molecular Weight</strong></td><td>~131 kDa</td></tr>
<tr><td><strong>Gene Family</strong></td><td>Nitric oxide synthase family</td></tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/aging" style="color:#ef9a9a">Aging</a>, <a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/cancer" style="color:#ef9a9a">Cancer</a>, <a href="/wiki/carcinoma" style="color:#ef9a9a">Carcinoma</a>, <a href="/wiki/diabetes" style="color:#ef9a9a">Diabetes</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">125 edges</a></td>
</tr>
</table>
</div>

Overview

The NOS2 gene encodes inducible nitric oxide synthase (iNOS), a key enzyme responsible for producing nitric oxide (NO) in response to inflammatory stimuli. Unlike the other NOS isoforms (nNOS and eNOS), iNOS is not constitutively expressed but is induced by cytokines, bacterial lipopolysaccharides (LPS), and other inflammatory signals. Once induced, iNOS can produce large amounts of NO for extended periods, making it a critical mediator of the immune response and inflammatory diseases.

Gene Structure

The NOS2 gene spans approximately 37 kb and consists of 26 exons. The promoter region contains multiple transcription factor binding sites, including [NF-κB](/entities/nf-kb), STAT-1, AP-1, and CREB, which mediate its induction by inflammatory stimuli. Several polymorphisms in the NOS2 promoter have been associated with altered susceptibility to inflammatory and neurodegenerative diseases.

Protein Structure

iNOS is a homodimeric enzyme, with each monomer containing:

• N-terminal oxygenase domain: Binds heme (Fe-protoporphyrin IX), tetrahydrobiopterin (BH4), and L-arginine
• C-terminal reductase domain: Contains FMN, FAD, and NADPH binding sites
• Calmodulin-binding domain: iNOS is constitutively bound to calmodulin, unlike nNOS and eNOS which require calcium/calmodulin for activation

Normal Function

In the immune system, iNOS-mediated NO production serves several critical functions:

In the brain, iNOS is expressed in astrocytes, [microglia](/entities/microglia), and neurons in response to injury or disease.

Expression Pattern

iNOS expression is highly inducible in:

• Macrophages and [microglia](/cell-types/microglia-neuroinflammation): Primary immune cells expressing iNOS
• [Astrocytes](/entities/astrocytes): Reactive astrocytes in injured brain
• [Neurons](/entities/neurons): Certain neuronal populations under pathological conditions
• Endothelial cells: During inflammatory responses
• hepatocytes: In response to cytokines

Role in Disease

Alzheimer's Disease

• iNOS is upregulated in AD brain, particularly around amyloid plaques
• Excessive NO production contributes to oxidative stress and nitrative damage
• NO interacts with [Aβ](/proteins/amyloid-beta) to form toxic species
• iNOS deficiency reduces amyloid pathology in mouse models
• Therapeutic targeting: iNOS inhibitors in development

Parkinson's Disease

• Increased iNOS expression in substantia nigra of PD patients
• NO contributes to dopaminergic neuron death through:
• Mitochondrial dysfunction
• Protein nitration
• DNA damage
• Inflammation-induced iNOS exacerbates MPTP toxicity
• iNOS knockout mice show protected dopaminergic neurons

Amyotrophic Lateral Sclerosis

• iNOS elevated in ALS spinal cord and motor [cortex](/brain-regions/cortex)
• NO contributes to motor neuron injury through oxidative damage
• Astrocytic iNOS may propagate neuroinflammation
• Correlation with disease progression

Multiple Sclerosis

• iNOS critical for demyelination and axonal injury
• NO produced by activated microglia damages oligodendrocytes
• iNOS inhibition reduces disease severity in EAE model
• Therapeutic potential of iNOS modulators

Stroke and Brain Injury

• iNOS induced after ischemic injury
• NO contributes to excitotoxic damage
• Timing-dependent effects (early vs. late iNOS)
• iNOS deletion reduces infarct size

Therapeutic Implications

| Approach | Status | Notes |
|----------|--------|-------|
| iNOS inhibitors | Preclinical | L-NIL, 1400W showing promise |
| NOS isoform-selective | Research | Avoiding eNOS/nNOS inhibition |
| BH4 supplementation | Research | Co-factor availability |
| Antioxidants | Clinical | Indirectly reduce NO toxicity |
| Anti-inflammatory | Clinical | Reduce iNOS induction |

Animal Models

• NOS2 knockout mice: Used to study iNOS function in disease models
• iNOS transgenic mice: Overexpression models for neuroinflammation
• Conditioned iNOS mice: Inducible expression systems

Key Research Directions

Background

The study of Nos2 Nitric Oxide Synthase 2 has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.

Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.

See Also

• [Neuroinflammation Pathway](/mechanisms/neuroinflammation-pathway)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)
• [Multiple Sclerosis](/diseases/multiple-sclerosis)
• [Stroke](/diseases/stroke)
• Nitric Oxide Signaling
• [Microglia](/cell-types/microglia)
• [Astrocytes](/cell-types/astrocytes)

External Links

• [NCBI Gene: NOS2](https://www.ncbi.nlm.nih.gov/gene/4843)
• [UniProt: P70689](https://www.uniprot.org/uniprot/P70689)
• [Human Protein Atlas](https://www.proteinatlas.org/)

References

Pathway Diagram

The following diagram shows the key molecular relationships involving NOS2 - Nitric Oxide Synthase 2 discovered through SciDEX knowledge graph analysis: