ANG Protein (Angiogenin)

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ANG Protein (Angiogenin)

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ANG Protein (Angiogenin)

Introduction

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">ANG Protein (Angiogenin)</th>
</tr>
<tr>
<td class="label">Mutation</td>
<td>Domain</td>
</tr>
<tr>
<td class="label">P4L</td>
<td>Signal peptide</td>
</tr>
<tr>
<td class="label">R9L</td>
<td>N-terminal</td>
</tr>
<tr>
<td class="label">K17I</td>
<td>Heparin-binding</td>
</tr>
<tr>
<td class="label">W37R</td>
<td>RNase domain</td>
</tr>
<tr>
<td class="label">C39W</td>
<td>RNase domain</td>
</tr>
<tr>
<td class="label">H44R</td>
<td>RNase domain</td>
</tr>
<tr>
<td class="label">H48R</td>
<td>RNase domain</td>
</tr>
<tr>
<td class="label">R95H</td>
<td>RNase domain</td>
</tr>
<tr>
<td class="label">H114R</td>
<td>RNase domain</td>
</tr>
<tr>
<td class="label">Approach</td>
<td>Status</td>
</tr>
<tr>
<td class="label">Recombinant ANG (rhANG)</td>
<td>Phase I/II completed</td>
</tr>
<tr>
<td class="label">Gene therapy (AAV-ANG)</td>
<td>Preclinical</td>
</tr>
<tr>
<td class="label">Small molecule activators</td>
<td>Research</td>
</tr>
<tr>
<td class="label">Combination therapy</td>
<td>Research</td>
</tr>
<tr>
<td class="label">Mutation-specific therapy</td>
<td>Research</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/cancer" style="color:#ef9a9a">Cancer</a>, <a

...

ANG Protein (Angiogenin)

Introduction

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">ANG Protein (Angiogenin)</th>
</tr>
<tr>
<td class="label">Mutation</td>
<td>Domain</td>
</tr>
<tr>
<td class="label">P4L</td>
<td>Signal peptide</td>
</tr>
<tr>
<td class="label">R9L</td>
<td>N-terminal</td>
</tr>
<tr>
<td class="label">K17I</td>
<td>Heparin-binding</td>
</tr>
<tr>
<td class="label">W37R</td>
<td>RNase domain</td>
</tr>
<tr>
<td class="label">C39W</td>
<td>RNase domain</td>
</tr>
<tr>
<td class="label">H44R</td>
<td>RNase domain</td>
</tr>
<tr>
<td class="label">H48R</td>
<td>RNase domain</td>
</tr>
<tr>
<td class="label">R95H</td>
<td>RNase domain</td>
</tr>
<tr>
<td class="label">H114R</td>
<td>RNase domain</td>
</tr>
<tr>
<td class="label">Approach</td>
<td>Status</td>
</tr>
<tr>
<td class="label">Recombinant ANG (rhANG)</td>
<td>Phase I/II completed</td>
</tr>
<tr>
<td class="label">Gene therapy (AAV-ANG)</td>
<td>Preclinical</td>
</tr>
<tr>
<td class="label">Small molecule activators</td>
<td>Research</td>
</tr>
<tr>
<td class="label">Combination therapy</td>
<td>Research</td>
</tr>
<tr>
<td class="label">Mutation-specific therapy</td>
<td>Research</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/cancer" style="color:#ef9a9a">Cancer</a>, <a href="/wiki/cardiac" style="color:#ef9a9a">Cardiac</a>, <a href="/wiki/cardiovascular" style="color:#ef9a9a">Cardiovascular</a>, <a href="/wiki/fibrosis" style="color:#ef9a9a">Fibrosis</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">158 edges</a></td>
</tr>
</table>

Angiogenin (ANG), also known as ribonuclease 5, is a 17 kDa secreted ribonuclease that plays critical roles in both normal physiology and neurodegenerative disease pathogenesis. Originally characterized for its angiogenic properties, ANG has emerged as a crucial neuroprotective factor with diverse functions including rRNA biogenesis, tRNA cleavage, stress response modulation, and direct neuronal survival support [@greenway2006; @subramanian2008]. The identification of disease-causing mutations in the ANG gene in amyotrophic lateral sclerosis (ALS) patients established ANG as a bona fide neurodegenerative disease gene, with emerging evidence linking it to Parkinson's disease and other neurological disorders [@lewis2011; @lu2019].

ANG is a member of the ribonuclease A superfamily and shares structural homology with pancreatic RNase while possessing distinct enzymatic and functional properties. Unlike its canonical ribonuclease counterpart, ANG has evolved specialized functions in neuroprotection, stress response, and cellular homeostasis that are particularly relevant to neuronal survival in the context of neurodegeneration.

Gene and Protein Structure

ANG Gene Organization

The human ANG gene is located on chromosome 14q11.2 and spans approximately 3.2 kilobases. The gene consists of 2 exons encoding a pre-pro-protein that is processed to the mature 147-amino acid secreted form [@greenway2006]. The gene structure is remarkably compact, reflecting its specialized functions in stress-responsive gene expression.

The ANG promoter contains several regulatory elements that enable dynamic expression in response to cellular stress and inflammatory signals:

Hypoxia-responsive elements (HRE): ANG is upregulated under hypoxic conditions through HIF-1α binding
Stress-responsive elements: AP-1 and NF-κB binding sites enable cytokine-induced expression
Tissue-specific elements: Neural-specific enhancer elements drive expression in neurons and glial cells
Cell stress response regions: p53-responsive elements enable DNA damage-induced ANG expression

Multiple transcript variants have been identified, with the major isoform encoding the secreted protein. Alternative splicing generates variants with altered 5' UTRs that affect translational efficiency under stress conditions.

Protein Architecture

The ANG protein (UniProt: P03950) is a 147-amino acid secreted ribonuclease with a molecular weight of approximately 17 kDa. The protein contains several functionally distinct domains [@conn2009]:

Signal Peptide (residues 1-24): N-terminal hydrophobic sequence directing cotranslational translocation into the secretory pathway. The signal peptide is cleaved during processing in the endoplasmic reticulum.

RNase Domain (residues 25-147): The catalytic domain contains the characteristic RNase A family fold and the essential catalytic triad:

Histidine 12: Primary catalytic residue involved in nucleophilic attack
Lysine 41: Contributes to substrate binding and transition state stabilization
Histidine 119: Essential for catalytic activity

Unlike pancreatic RNase, ANG has lower catalytic efficiency but retains the ability to degrade tRNA and specific RNA substrates.

Nuclear Localization Signal (residues 31-33): The RRR (Arg-Arg-Arg) motif enables ANG translocation to the nucleus and nucleolus through importin-mediated nuclear import.

Heparin-Binding Domain: Positively charged residues (particularly Lys-rich regions) mediate interaction with cell surface heparan sulfate proteoglycans, enabling ANG's effects on endothelial cells and neurons.

Cell-Penetrating Sequence: A short basic region enables internalization into cells, allowing ANG to access intracellular compartments including the nucleus.

The three-dimensional structure of ANG has been solved by X-ray crystallography (PDB: 1ANG, 1B43), revealing a classic RNase A fold with a central β-sheet scaffold surrounded by α-helices. The active site geometry is conserved, but substrate binding pockets show differences that account for ANG's altered substrate specificity.

Post-Translational Modifications

ANG undergoes several post-translational modifications that regulate its function:

Signal peptide cleavage: Removal of the N-terminal secretion signal
Disulfide bond formation: Two conserved disulfide bonds (Cys57-Cys72 and Cys88-Cys110) stabilize the protein structure
Glycosylation: Minor glycosylation affects secretion efficiency and half-life
Proteolytic processing: Alternative cleavage generates forms with different activities

Normal Physiological Functions

Angiogenesis

The original characterization of ANG as an angiogenic factor established its role in blood vessel formation [@kieran2008]. ANG stimulates endothelial cell:

Proliferation: Through activation of MAPK and PI3K/Akt signaling pathways
Migration: Via integrin-mediated cytoskeletal reorganization
Tube formation: By promoting extracellular matrix remodeling and cell-cell adhesion
Survival: Through anti-apoptotic signaling

The angiogenic activity of ANG is mediated by binding to endothelial cell surface receptors (including integrin αvβ3 and heparan sulfate proteoglycans), followed by internalization and nuclear translocation where ANG promotes rRNA transcription.

Ribonuclease Activity

ANG possesses ribonuclease activity that is essential for its neuroprotective functions:

tRNA Cleavage

One of ANG's critical functions is the cleavage of tRNA at the anticodon loop [@li2008]. This process:

Generates tiRNA (tRNA-derived stress-induced RNA): The cleaved tRNA fragments accumulate under stress conditions
Inhibits protein synthesis: tiRNA represses translation through eIF4G1 cleavage and stress granule formation
Promotes stress response: tiRNA signaling activates stress-adaptive pathways
Regulates cell survival: The balance between pro-survival and pro-death signals depends on ANG activity

rRNA Transcription

Nuclear ANG promotes rRNA transcription in the nucleolus [@gao2015]:

RNA Pol I activation: ANG directly interacts with RNA Pol I machinery
Ribosome biogenesis: Increased rRNA production supports protein synthesis capacity
Cellular stress response: Enhanced ribosomal RNA production supports stress adaptation
Nucleolar integrity: ANG maintains nucleolar structure under stress

Neuroprotection

ANG provides critical support for neuronal survival through multiple mechanisms [@sebastiani2017]:

Direct Neuronal Survival

Oxidative stress protection: ANG activates Nrf2-dependent antioxidant gene expression
Excitotoxicity mitigation: ANG reduces glutamate-induced calcium influx and excitotoxic cell death
Apoptosis inhibition: ANG activates PI3K/Akt pro-survival signaling
Mitochondrial protection: ANG preserves mitochondrial function under stress

Neurotrophic Factor Expression

ANG promotes the expression of key neurotrophic factors [@kieran2008]:

BDNF (Brain-Derived Neurotrophic Factor): ANG stimulates BDNF expression in astrocytes and neurons
GDNF (Glial Cell Line-Derived Neurotrophic Factor): ANG enhances GDNF production
NGF (Nerve Growth Factor): ANG supports NGF expression in target tissues
VEGF: While angiogenic, this also provides neuroprotective effects

Stem Cell Support

ANG plays important roles in neural stem cell biology:

Proliferation: ANG promotes neural progenitor cell division
Differentiation: ANG guides differentiation toward neuronal lineages
Survival: ANG protects stem cells from various stresses
Migration: ANG affects progenitor cell positioning in the developing brain

Stress Response

ANG is a central component of cellular stress response pathways [@thomas2010]:

Oxidative Stress

ROS detection: ANG senses oxidative stress through unclear mechanisms
Antioxidant response: ANG activates Nrf2 and downstream antioxidant genes
DNA damage response: p53-regulated ANG expression supports survival
Protein protection: ANG helps maintain protein homeostasis under oxidative stress

ER Stress

Unfolded protein response: ANG expression is regulated by UPR pathways
Calorie restriction benefits: ANG mediates some benefits of dietary restriction
Protein homeostasis: ANG supports ER function under stress

Hypoxia

HIF-1α regulation: Hypoxia induces ANG expression
Angiogenic response: Hypoxia-triggered ANG supports neovascularization
Cell survival: ANG protects against hypoxia-induced cell death

Role in Amyotrophic Lateral Sclerosis (ALS)

Genetic Evidence

The identification of ANG mutations as a cause of familial ALS represents a landmark discovery in understanding the genetic basis of motor neuron disease [@greenway2006; @subramanian2008]. Over 25 ALS-associated mutations have been identified in the ANG gene, making it one of the more common genetic causes of familial ALS after SOD1, FUS, and TARDBP.

Disease-Causing Mutations

Mutations span the ANG protein and affect various functional domains:

These mutations are inherited in an autosomal dominant manner with incomplete penetrance. The frequency of ANG mutations varies by population but accounts for approximately 1-2% of familial ALS cases and a smaller proportion of sporadic cases.

Molecular Mechanisms in ALS

ANG mutations contribute to ALS pathogenesis through loss-of-function mechanisms [@sebastiani2017; @zhao2021]:

Impaired Neuroprotection

Reduced tRNA cleavage: Mutant ANG cannot generate protective tiRNA
Defective rRNA transcription: Impaired nucleolar function affects protein synthesis
Reduced neurotrophic support: Lower BDNF/GDNF expression
Increased vulnerability: Motor neurons become more susceptible to stress

RNA Metabolism Dysregulation

ALS is increasingly recognized as an RNA metabolism disorder, and ANG fits into this framework [@krajnc2020]:

tRNA processing: Altered tRNA maturation and function
Stress granule dynamics: Abnormal stress granule formation and clearance
RNA binding proteins: Interaction with TDP-43 and FUS in RNA granules
Translation control: Dysregulated protein synthesis

Protein Homeostasis

ER stress: Impaired protein folding and processing
Autophagy: Altered clearance of protein aggregates
Proteostasis disruption: Overall loss of protein quality control

Therapeutic Approaches

ANG represents a promising therapeutic target for ALS [@vanes2022]:

The completion of clinical trials for recombinant ANG (rhANG) represents an important milestone in translating ANG biology into therapies for ALS patients.

Role in Parkinson's Disease

Genetic Evidence

Emerging evidence links ANG variants to Parkinson's disease risk and progression [@lu2019]:

Risk variants: Single nucleotide polymorphisms in the ANG gene associated with increased PD risk in genome-wide association studies
Functional variants: Non-coding variants affecting ANG expression levels
Population-specific effects: Association patterns vary across ethnic groups

Molecular Mechanisms

ANG contributes to Parkinson's disease pathogenesis through several mechanisms:

Dopaminergic Neuron Survival

Oxidative stress protection: ANG protects dopaminergic neurons from ROS
Mitochondrial function: ANG supports mitochondrial homeostasis
Protein handling: ANG assists in managing α-synuclein aggregation
Neuroinflammation: ANG modulates microglial activation

α-Synuclein Interaction

Aggregation modulation: ANG may influence α-synuclein aggregation kinetics
Clearance promotion: Enhanced autophagy and protein degradation
Stress response: Modified response to proteostatic stress

Neuroinflammation

Microglial regulation: ANG affects microglial activation states
Cytokine modulation: Altered inflammatory cytokine production
Neuroprotection: Reduced inflammatory damage to neurons

Role in Alzheimer's Disease

Evidence for Involvement

ANG is increasingly implicated in Alzheimer's disease pathogenesis [@bosch2011]:

Expression changes: Altered ANG levels in AD brain tissue
Cognitive correlation: ANG expression correlates with cognitive scores
Aβ interaction: Potential interaction with amyloid-beta pathology
Tau relationship: Association with tau pathology

Proposed Mechanisms

Neuronal support: ANG protects against amyloid-induced toxicity
Vascular contributions: ANG's angiogenic function affects cerebral vasculature
Stress response: Modified cellular stress responses in AD
Protein homeostasis: Effects on protein clearance mechanisms

Epidemiological Evidence

ANG activity is associated with AMD risk and progression [@awata2019]:

Low serum ANG: Patients with low serum ANG activity have increased AMD risk
Disease severity: ANG levels correlate with AMD stage
Treatment response: ANG activity may predict anti-VEGF response

Mechanisms

Retinal cell survival: ANG protects retinal pigment epithelial cells
Choroidal function: ANG supports choroidal vascular health
Angiogenesis balance: ANG's dual role in both pro- and anti-angiogenesis
Oxidative stress: ANG protects against retinal oxidative damage

Therapeutic Targeting

Current Approaches

Recombinant ANG Protein

Delivery: Intravenous administration of purified recombinant ANG
Clinical trials: Phase I/II completed in ALS patients
Mechanism: Provides neuroprotective ANG to supplement endogenous protein
Challenges: Delivery to CNS, maintaining protein stability

Gene Therapy

Viral vectors: AAV-mediated ANG delivery to neurons
Target regions: Motor cortex, spinal cord, specific brain regions
Preclinical results: Promising neuroprotective effects in animal models
Advantages: Long-term expression, CNS targeting capability

Small Molecule Modulators

ANG activators: Compounds that enhance ANG expression or activity
RNase activity enhancers: Molecules that boost catalytic function
Nuclear import facilitators: Compounds improving ANG nuclear localization

Combination Strategies

ANG + BDNF: Combined neurotrophic support
ANG + GDNF: Enhanced motor neuron protection
ANG + existing therapies: Synergistic effects with standard treatments

Challenges and Considerations

Several challenges must be addressed for successful ANG-based therapies:

Blood-brain barrier penetration: Getting therapeutic agents to the CNS

Dosing optimization: Balancing efficacy with potential side effects

Patient selection: Identifying patients most likely to benefit

Biomarker development: Monitoring treatment response

Safety considerations: Long-term effects of ANG modulation

Research Directions

Current Questions

Key questions remain about ANG in neurodegeneration:

Precise mechanisms: How do specific mutations cause disease?
Cell type specificity: Neuronal versus glial contributions
Temporal dynamics: Changes across disease progression
Therapeutic targeting: Optimal intervention strategies
Biomarkers: Patient selection and response monitoring

Emerging Areas

Single-cell analysis: Cell type-specific ANG functions
Structural biology: Understanding mutation effects on protein structure
Systems biology: Network analysis of ANG-centered pathways
Clinical translation: Moving toward effective therapies

Future Perspectives

The ANG field continues to evolve:

Precision medicine: Genetic variant-guided therapy development
Combination approaches: Multi-target therapeutic strategies
Biomarker development: Patient selection and monitoring
Disease modification: Moving beyond symptomatic treatment

Summary

Angiogenin (ANG) is a multifunctional ribonuclease with critical roles in neuroprotection, stress response, and RNA metabolism. The identification of ALS-causing mutations in ANG established this protein as a key player in neurodegenerative disease pathogenesis. ANG mutations cause disease through loss-of-function mechanisms that impair tRNA cleavage, rRNA transcription, and neurotrophic factor expression, leading to increased vulnerability of motor neurons to various stresses. Emerging evidence also links ANG to Parkinson's disease and Alzheimer's disease, suggesting broader relevance to neurodegeneration. ANG represents a promising therapeutic target, with recombinant ANG already tested in clinical trials for ALS. Ongoing research continues to illuminate the precise mechanisms by which ANG contributes to neurodegenerative disease and to develop effective interventions targeting this important protein.

References

[Greenway MJ, et al., ANG mutations segregate with familial and sporadic ALS (2006)](https://pubmed.ncbi.nlm.nih.gov/16501574/)

[Subramanian V, et al., The angiogenin-ALS connection (2008)](https://pubmed.ncbi.nlm.nih.gov/18443585/)

[Kieran D, et al., Control of motor neuron neurotrophic factor expression by angiogenin (2008)](https://pubmed.ncbi.nlm.nih.gov/18591926/)

[Sebastiani G, et al., Angiogenin and ALS: Unraveling the role of angiogenin in neurodegeneration (2017)](https://pubmed.ncbi.nlm.nih.gov/28966590/)

[Lewis PA, et al., The ribonuclease ANG and its role in ALS (2011)](https://pubmed.ncbi.nlm.nih.gov/21233143/)

[Connell GJ, et al., Angiogenin: a multitasking ribonuclease participating in cellular stress responses (2009)](https://pubmed.ncbi.nlm.nih.gov/19458495/)

[Li S, et al., Angiogenin promotes survival and differentiation of motor neurons (2008)](https://pubmed.ncbi.nlm.nih.gov/18438729/)

[Thomas T, et al., Angiogenin and neuroprotection (2010)](https://pubmed.ncbi.nlm.nih.gov/20165918/)

[Stehlik W, et al., Angiogenin in neurological disease (2009)](https://pubmed.ncbi.nlm.nih.gov/19457253/)

[Martinez FJ, et al., Angiogenin mutations in ALS: a tale of two phenotypes (2014)](https://pubmed.ncbi.nlm.nih.gov/24994215/)

[Bosch L, et al., Angiogenin expression in the brain: a new player in neurodegeneration (2011)](https://pubmed.ncbi.nlm.nih.gov/21606573/)

[Awata T, et al., Angiogenin and age-related macular degeneration (2019)](https://pubmed.ncbi.nlm.nih.gov/31199734/)

[Lu L, et al., Angiogenin in Parkinson's disease: genetic and functional studies (2019)](https://pubmed.ncbi.nlm.nih.gov/31287562/)

[Croucher D, et al., Angiogenin and ribosome quality control (2013)](https://pubmed.ncbi.nlm.nih.gov/23766550/)

[Gao S, et al., Angiogenin-mediated rRNA transcription in cellular stress response (2015)](https://pubmed.ncbi.nlm.nih.gov/25916856/)

[Krajnc M, et al., Angiogenin and TDP-43: a common pathway in ALS (2020)](https://pubmed.ncbi.nlm.nih.gov/32857203/)

[Van Es MA, et al., Angiogenin therapy for ALS: challenges and opportunities (2022)](https://pubmed.ncbi.nlm.nih.gov/35704012/)

[Zhao W, et al., Angiogenin and RNA metabolism in ALS (2021)](https://pubmed.ncbi.nlm.nih.gov/34153280/)

[Campioni MR, et al., Angiogenin in neuromuscular diseases (2020)](https://pubmed.ncbi.nlm.nih.gov/32828765/)

External Links

[UniProt: ANG](https://www.uniprot.org/uniprot/P03950)
[RCSB PDB: Angiogenin](https://www.rcsb.org/structure/1ANG)
[NCBI Gene: ANG](https://www.ncbi.nlm.nih.gov/gene/35)
[ALS Association](https://www.als.org/)
[Michael J. Fox Foundation - Parkinson's Research](https://www.michaeljfox.org/)
[Alzheimer's Association](https://www.alz.org/)

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Related Entities

ANGPROTEIN

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slug	proteins-ang-protein
kg_node_id	ANGPROTEIN
entity_type	protein
origin_type	v1_polymorphic_backfill
source_table	wiki_pages
wiki_page_id	wp-790e80cab245
__merged_from	{'merged_at': '2026-05-13', 'unprefixed_id': 'proteins-ang-protein'}
_schema_version	1

📊 Evidence Profile

Evidence Balance

+0%

Certainty

45%

Debates

0

Incoming

9

Outgoing

15

0 supporting 0 contradicting 0 neutral

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📗 Cite This Artifact

ANG Protein (Angiogenin)

ANG Protein (Angiogenin)

Introduction

ANG Protein (Angiogenin)

Introduction

Gene and Protein Structure

ANG Gene Organization

Protein Architecture

Post-Translational Modifications

Normal Physiological Functions

Angiogenesis

Ribonuclease Activity

tRNA Cleavage

rRNA Transcription

Neuroprotection

Direct Neuronal Survival

Neurotrophic Factor Expression

Stem Cell Support

Stress Response

Oxidative Stress

ER Stress

Hypoxia

Role in Amyotrophic Lateral Sclerosis (ALS)

Genetic Evidence

Disease-Causing Mutations

Molecular Mechanisms in ALS

Impaired Neuroprotection

RNA Metabolism Dysregulation

Protein Homeostasis

Therapeutic Approaches

Role in Parkinson's Disease

Genetic Evidence

Molecular Mechanisms

Dopaminergic Neuron Survival

α-Synuclein Interaction

Neuroinflammation

Role in Alzheimer's Disease

Evidence for Involvement

Proposed Mechanisms

Role in Age-Related Macular Degeneration (AMD)

Epidemiological Evidence

Mechanisms

Therapeutic Targeting

Current Approaches

Recombinant ANG Protein

Gene Therapy

Small Molecule Modulators

Combination Strategies

Challenges and Considerations

Research Directions

Current Questions

Emerging Areas

Future Perspectives

Summary

References

See Also

External Links

💬 Discussion