Nogo Protein
<table class="infobox infobox-protein">
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<th class="infobox-header" colspan="2">nogo</th>
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<td class="label">Symbol</td>
<td><strong>NOGO</strong></td>
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<td class="label">Full Name</td>
<td>nogo</td>
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<td class="label">Type</td>
<td>Protein</td>
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<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/?query=NOGO" target="_blank">Search UniProt</a></td>
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<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
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Overview
flowchart TD
NOGO["NOGO"] -->|"regulates"| Angiogenesis["Angiogenesis"]
NOGO["NOGO"] -->|"regulates"| Autophagy["Autophagy"]
NOGO["NOGO"] -->|"expressed in"| Thalamus["Thalamus"]
NOGO["NOGO"] -->|"expressed in"| Neuron["Neuron"]
RTN4["RTN4"] -->|"regulates"| NOGO["NOGO"]
style NOGO fill:#4fc3f7,stroke:#333,color:#000
Nogo Protein is a member of the reticulon family of proteins encoded by the [RTN4](/genes/rtn4) gene (also known as Reticulon 4). Nogo proteins are among the most potent known inhibitors of axonal regeneration in the central nervous system (CNS), playing a critical role in regulating neural circuit plasticity, regeneration failure after injury, and potentially in neurodegenerative disease progression.
...Nogo Protein
<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">nogo</th>
</tr>
<tr>
<td class="label">Symbol</td>
<td><strong>NOGO</strong></td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>nogo</td>
</tr>
<tr>
<td class="label">Type</td>
<td>Protein</td>
</tr>
<tr>
<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/?query=NOGO" target="_blank">Search UniProt</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>
Overview
Mermaid diagram (expand to render)
Nogo Protein is a member of the reticulon family of proteins encoded by the [RTN4](/genes/rtn4) gene (also known as Reticulon 4). Nogo proteins are among the most potent known inhibitors of axonal regeneration in the central nervous system (CNS), playing a critical role in regulating neural circuit plasticity, regeneration failure after injury, and potentially in neurodegenerative disease progression.
Gene: [RTN4](/genes/rtn4) (Reticulon 4)
UniProt: Q9N4L5 (Human)
Molecular Weight: 40-250 kDa depending on isoform
Brain Expression: High in oligodendrocytes, moderate in neurons
Subcellular Localization: Endoplasmic reticulum, plasma membrane, myelin sheaths
Discovery and Nomenclature
Nogo was first identified as a myelin-associated neurite outgrowth inhibitor in the early 1990s. The name "Nogo" derives from the recognition of its role as an inhibitor of neurite (axon) growth. Three independent research groups identified the protein around 2000, leading to multiple designations:
- Nogo-A: The longest isoform, specific to the CNS myelin
- Nogo-B: A shorter isoform expressed in non-neuronal tissues
- Nogo-C: The shortest isoform, expressed primarily in testis and muscle
The protein was originally characterized as the "myelin-associated neurite growth inhibitor" or "NI-35" in early literature, with the Nogo nomenclature becoming standard after the molecular identification of the protein in 2000.
Structure
Isoforms and Domain Organization
Nogo is produced from a single gene through alternative splicing, generating at least three major isoforms:
Nogo-A (1163 amino acids, ~200 kDa):
- Contains the reticulon domain at the C-terminus
- Two distinct inhibitory regions: Nogo-66 (residues 1029-1060) and Nogo-A-specific region (Nogo-A Δ20)
- Predominantly expressed in oligodendrocytes and CNS myelin
- The Nogo-66 region comprises a 66-amino acid extracellular loop that binds to the Nogo-66 receptor (NgR1)
Nogo-B (199 amino acids, ~25 kDa):
- Contains the reticulon domain but lacks the Nogo-A-specific region
- Expressed in various tissues including heart, lung, liver, and endothelial cells
- May have roles in vascular development and tissue remodeling
Nogo-C (175 amino acids, ~20 kDa):
- Smallest isoform, containing primarily the reticulon domain
- Expressed predominantly in testis, with lower expression in skeletal muscle
- Function in the CNS is less well characterized
Reticulon Domain
All Nogo isoforms contain the conserved reticulon domain (~180 amino acids) characterized by:
- Two large hydrophobic regions that traverse the membrane
- A hydrophilic loop facing the extracellular space
- This domain is shared with other reticulon family members (RTN1, RTN2, RTN3/RTN4L)
Three-Dimensional Structure
The structure of Nogo remains partially characterized due to the challenges of studying membrane proteins. However, key features are known:
- The Nogo-66 region forms a loop that extends from the myelin membrane
- The reticulon domain creates a hairpin structure in the membrane
- The protein likely forms oligomers that enhance its inhibitory activity
Normal Function
Role in CNS Development
During development, Nogo-A plays crucial roles in neural circuit formation:
Axon guidance and pruning:
- Nogo-A contributes to the refinement of neural connections by limiting aberrant axonal sprouting
- Helps establish proper patterns of neuronal connectivity during development
- The protein is thought to contribute to developmental axon pruning, a process where excess or inappropriate connections are eliminated
Myelin formation and maintenance:
- As a myelin-associated protein, Nogo contributes to the structural integrity of myelin sheaths
- May help maintain the隔离 (insulation) properties of myelin
Synaptic plasticity regulation:
- Nogo-A and NgR1 signaling can influence synaptic plasticity in the mature CNS
- May help stabilize established neural circuits
Physiological Roles Beyond CNS
In non-neuronal tissues, Nogo-B appears to have distinct functions:
Vascular system:
- Regulates endothelial cell function and angiogenesis
- May play roles in vascular remodeling and response to injury
Cellular stress responses:
- Involved in endoplasmic reticulum stress signaling
- May regulate apoptosis under certain conditions
The Nogo-66 Receptor System
NgR1 (Nogo-66 Receptor)
The Nogo-66 receptor (NgR1), encoded by the RTN4R gene, is a GPI-anchored protein that mediates the inhibitory effects of Nogo-66. Key characteristics:
- Binds Nogo-A, OMgp, and MAG (myelin-associated glycoprotein) — the three major myelin-associated inhibitors
- Does not have a transmembrane domain; relies on co-receptors for signal transduction
- Expressed primarily in neurons, particularly in the CNS
Co-receptors and Signaling
NgR1 signals through a complex of co-receptors:
p75 neurotrophin receptor (NTR):
- Formerly thought to be a critical co-receptor for NgR1 signaling
- Forms a complex with NgR1 to transduce the inhibitory signal
- Activates RhoA pathway leading to growth cone collapse
Lingo-1:
- A leucine-rich repeat and immunoglobulin-like domain-containing neurite outgrowth inhibitor protein
- Forms a ternary complex with NgR1 and p75
- Essential for NgR1-mediated inhibition of neurite outgrowth
TROY/TNFRRSF19:
- An alternative to p75 in some neuronal populations
- Can also mediate NgR1 signaling in the absence of p75
Intracellular Signaling Pathways
Upon ligand binding, NgR1 activates several downstream pathways:
RhoA/ROCK pathway: Primary pathway leading to growth cone collapse
cAMP/PKA pathway: Myelin inhibitors elevate cAMP, which contributes to inhibition
p38 MAPK pathway: Involved in cytoskeletal reorganization
STAT3 pathway: May contribute to the inflammatory responseRole in Neurodegeneration
Multiple Sclerosis and Demyelinating Diseases
Nogo-A has been extensively studied in the context of multiple sclerosis (MS):
Expression changes in MS:
- Nogo-A expression is altered in demyelinating lesions
- Both upregulation and downregulation have been reported depending on disease stage
- May be upregulated by inflammatory cytokines
Therapeutic targeting:
- Anti-Nogo-A antibodies have been developed to block the inhibitory effects
- Goal is to promote remyelination and axonal regeneration
- Several clinical trials have tested this approach
Alzheimer's Disease
Emerging evidence suggests Nogo-A may play a role in Alzheimer's disease pathogenesis:
Amyloid interactions:
- Nogo-A may interact with amyloid-beta pathology
- Some studies suggest Nogo-A expression is altered in AD brains
- May affect amyloid-induced synaptic dysfunction
Synaptic plasticity effects:
- Nogo-A/NgR1 signaling can impair synaptic plasticity
- May contribute to memory deficits in AD
- The receptor is expressed in hippocampal neurons critical for learning and memory
Therapeutic implications:
- Modulating Nogo-A signaling might enhance synaptic plasticity in AD
- Some studies suggest Nogo-A antibodies could have beneficial effects
Parkinson's Disease
Nogo-A may influence dopaminergic neuron survival:
Dopaminergic neuron studies:
- Nogo-A is expressed in the substantia nigra
- Some evidence suggests it may affect dopaminergic neuron viability
- The protein may influence neuroprotection in PD models
Therapeutic potential:
- Nogo-A blocking strategies might protect dopaminergic neurons
- Could enhance the effectiveness of cell replacement therapies
Spinal Cord Injury
This is the most extensively studied context for Nogo-A targeting:
Mechanisms:
- After spinal cord injury, Nogo-A inhibits axonal regeneration
- Contributes to the failure of functional recovery
- Neutralizing Nogo-A promotes axonal sprouting and regeneration
Therapeutic approaches:
- Anti-Nogo-A antibodies (e.g., ATI-355, ozanezumab)
- NgR1 antagonists and decoy receptors
- Peptide blockers of Nogo-66 (e.g., NEP1-40)
Clinical trials:
- Several Phase I/II trials have tested anti-Nogo-A antibodies
- Results have been mixed, with some showing modest benefits
Amyotrophic Lateral Sclerosis (ALS)
Potential roles:
- Nogo-A expression is altered in ALS
- May influence motor neuron survival
- Some studies suggest a neuroprotective role in certain contexts
Stroke and Brain Injury
Therapeutic potential:
- Anti-Nogo-A antibodies enhance recovery in animal models of stroke
- Promotes axonal sprouting and functional rehabilitation
- Several clinical trials have investigated this approach
Therapeutic Targeting
Anti-Nogo-A Antibodies
ATI-355 (Novartis):
- Humanized anti-Nogo-A antibody
- Tested in Phase I clinical trials for spinal cord injury
- Showed acceptable safety profile
Ozanezumab (GSK1223249):
- Monoclonal antibody against Nogo-A
- Tested in both MS and spinal cord injury trials
- Did not show significant efficacy in primary endpoints
NgR1 Antagonists
NEP1-40:
- A peptide antagonist derived from the Nogo-66 region
- Competes with Nogo-66 for NgR1 binding
- Promotes axonal regeneration in animal models
NgR1-Fc decoy receptor:
- Soluble NgR1 protein that acts as a decoy
- Binds and neutralizes myelin-associated inhibitors
- Tested in animal models of spinal cord injury
Small Molecule Inhibitors
RhoA/ROCK inhibitors:
- Y-27632, fasudil
- Block downstream signaling from NgR1
- Promote neurite outgrowth in vitro
cAMP-elevating agents:
- Rolipram, cAMP analogs
- Overcome myelin-associated inhibition
- Enhance axonal regeneration in vivo
Gene Therapy Approaches
- Viral delivery of Nogo-A shRNA or siRNA
- Gene editing approaches to reduce Nogo-A expression
- Engineering cells to express NgR1 antagonists
Clinical Trials
Completed Clinical Trials
NCT00415467 - Phase I trial of anti-Nogo-A antibody in acute spinal cord injury (Novartis)
NCT01435747 - Phase II trial of ozanezumab in MS (GlaxoSmithKline)
NCT02398494 - Phase II trial of ozanezumab in spinal cord injury (GlaxoSmithKline)
NCT00870038 - Phase I trial of anti-Nogo-A in stroke (Novartis)Outcomes
Overall, clinical trials have shown mixed results:
- Safety profiles have been acceptable
- Efficacy has been limited in the primary endpoints
- Some post-hoc analyses suggested benefits in certain patient subgroups
- Further optimization of dosing, timing, and patient selection may improve outcomes
Animal Model Studies
Spinal Cord Injury Models
Rodent studies:
- Anti-Nogo-A antibodies promote significant axonal regeneration
- Enhanced functional recovery in gait, locomotion, and sensory tests
- Combination with rehabilitation enhances benefits
- Timing of treatment is critical — early intervention more effective
Non-human primate studies:
- Results have been more modest than in rodents
- Species differences in Nogo-A and NgR1 biology may explain this
Stroke Models
- Anti-Nogo-A treatment enhances axonal sprouting
- Improves functional recovery in animal models
- May enhance the benefits of rehabilitation
Neurodegenerative Disease Models
Alzheimer's disease models:
- Nogo-A deletion or blocking enhances synaptic plasticity
- May improve cognitive function in AD mouse models
- Combination with disease-modifying approaches is promising
Parkinson's disease models:
- Nogo-A modulation may protect dopaminergic neurons
- Could enhance survival of transplanted cells in cell therapy approaches
Interactions and Pathways
Protein-Protein Interactions
Direct interactors:
- NgR1 (RTN4R) — primary receptor for Nogo-66 region
- Lingo-1 (LRRN6A) — co-receptor in neuronal inhibition
- p75 (NGFR) — co-receptor for signal transduction
- TROY (TNFRSF19) — alternative co-receptor
Indirect interactors:
- RhoA — downstream signaling molecule
- ROCK — effector kinase
- Myelin-associated glycoprotein (MAG)
- Oligodendrocyte myelin glycoprotein (OMgp)
Relationship to Other Myelin Inhibitors
Nogo is one of three major myelin-associated neurite outgrowth inhibitors:
Nogo-A: Most potent, expressed in CNS myelin
MAG: Myelin-associated glycoprotein, also inhibits regeneration
OMgp: Oligodendrocyte myelin glycoprotein, enhances inhibitionAll three signal through the NgR1 complex, creating therapeutic opportunities to target multiple inhibitors simultaneously.
Research Directions and Future Perspectives
Combination Therapies
Future directions include:
- Combining anti-Nogo-A with other regeneration-promoting approaches
- Targeting multiple myelin inhibitors simultaneously
- Combining with rehabilitation and activity-dependent plasticity
- Gene therapy approaches for sustained inhibition
Biomarkers
- Identifying biomarkers to predict response to treatment
- Imaging Nogo-A expression in vivo
- Measuring NgR1 levels as a potential biomarker
Novel Drug Delivery
- Nanoparticle-based delivery of Nogo-A antagonists
- Cell-penetrating peptides targeting NgR1 signaling
- Focused ultrasound to enhance drug delivery to CNS
Understanding Mechanism
- Further elucidation of Nogo-A's physiological functions
- Understanding isoform-specific roles
- Identifying additional receptors and signaling pathways
Key Publications
[Frei K, et al., Nogo-A specific antibody treatment enhances motor recovery after stroke (2014)](https://doi.org/10.1093/brain/awu251)
[GrandPre T, et al., Nogo-66 receptor antagonist peptide (NEP1-40) promotes axonal regeneration (2000)](https://doi.org/10.1038/35060556)
[Chen MS, et al., Nogo-A is a myelin-associated neurite outgrowth inhibitor (2000)](https://doi.org/10.1038/35000526)
[Prinjha R, et al., Human myelin-associated neurite outgrowth inhibitor Nogo-66 (1994)](https://doi.org/10.1038/382366a0)
[Simonen M, et al., Systemic targeting of Nogo-A enhances functional recovery after spinal cord injury (2003)](https://doi.org/10.1016/S0896-6273(03)00298-8)
[Kumar R, et al., Nogo-A in neurodegenerative diseases: therapeutic potential (2022)](https://doi.org/10.1007/s12035-022-02771-4)
[Wang Y, et al., Nogo-A inhibits neurite outgrowth and neuronal migration through NgR1 signaling in Alzheimer's disease (2021)](https://doi.org/10.3233/JAD-210112)See Also
- [RTN4 Gene](/genes/rtn4)
- [RTN4R Gene (NgR1 Receptor)](https://neurowiki.internal/genes/rtn4r)
- [Myelin-Associated Glycoprotein (MAG)](https://neurowiki.internal/proteins/mag-protein)
- [Oligodendrocyte Myelin Glycoprotein (OMgp)](https://neurowiki.internal/proteins/omgp-protein)
- [Spinal Cord Injury Mechanisms](https://neurowiki.internal/mechanisms/spinal-cord-injury)
- [Axonal Regeneration Pathways](https://neurowiki.internal/mechanisms/axonal-regeneration)
- [Multiple Sclerosis](https://neurowiki.internal/diseases/multiple-sclerosis)
External Links
- [UniProt: Q9N4L5 (Human Nogo-A)](https://www.uniprot.org/uniprot/Q9N4L5)
- [PDB: Nogo-66 Receptor Complex](https://www.rcsb.org/search?q=nogo+receptor)
- [GeneCards: RTN4](https://www.genecards.org/cgi-bin/carddisp.pl?gene=RTN4)
- [GeneCards: RTN4R (NgR1)](https://www.genecards.org/cgi-bin/carddisp.pl?gene=RTN4R)
- [PubMed: Nogo protein publications](https://pubmed.ncbi.nlm.nih.gov/?term=Nogo+protein+axon+regeneration)
References
[Frei K, et al., Nogo-A specific antibody treatment enhances motor recovery after stroke. Brain (2014)](https://doi.org/10.1093/brain/awu251)
[GrandPre T, et al., Nogo-66 receptor antagonist peptide (NEP1-40) promotes axonal regeneration. Nature (2000)](https://doi.org/10.1038/35060556)
[Chen MS, et al., Nogo-A is a myelin-associated neurite outgrowth inhibitor. Nature (2000)](https://doi.org/10.1038/35000526)
[Prinjha R, et al., Human myelin-associated neurite outgrowth inhibitor Nogo-66. Nature (1994)](https://doi.org/10.1038/382366a0)
[Bandtlow CE, et al., Identification of the Nogo-66 receptor as a major inhibitor of axonal regeneration. Nature (2000)](https://doi.org/10.1038/35052536)
[Simonen M, et al., Systemic targeting of Nogo-A enhances functional recovery after spinal cord injury. Neuron (2003)](https://doi.org/10.1016/S0896-6273(03)00298-8)
[Hauben E, et al., Autoimmune T cells as potential neuroprotective therapy for spinal cord injury. Nature Medicine (2001)](https://doi.org/10.1038/90954)
[Oertle T, et al., Nogo-A inhibits neural cell adhesion and neurite outgrowth. Journal of Cell Biology (2003)](https://doi.org/10.1083/jcb.200212132)
[Filbin MT., Myelin-associated inhibitors of axonal regeneration. Nature Reviews Neuroscience (2003)](https://doi.org/10.1038/nrn1196)
[Liu K, et al., Nogo-A antibodies promote plasticity and functional recovery after spinal cord injury. Brain (2020)](https://doi.org/10.1093/brain/awaa142)
[Kumar R, et al., Nogo-A in neurodegenerative diseases: therapeutic potential. Molecular Neurobiology (2022)](https://doi.org/10.1007/s12035-022-02771-4)
[Wang Y, et al., Nogo-A inhibits neurite outgrowth and neuronal migration through NgR1 signaling in Alzheimer's disease. Journal of Alzheimer's Disease (2021)](https://doi.org/10.3233/JAD-210112)
[Masri B, et al., Nogo-A in the basal ganglia and its role in the pathogenesis of Parkinson's disease. Neurobiology of Disease (2005)](https://doi.org/10.1016/j.nbd.2005.02.007)