MAP3K5 — Mitogen-Activated Protein Kinase Kinase Kinase 5
Introduction
MAP3K5 (also known as ASK1 — Apoptosis Signal-regulating Kinase 1) is a critical MAP3K that activates the JNK and p38 MAPK pathways in response to cellular stress. Located on chromosome 6q26, this gene encodes a serine/threonine protein kinase that serves as a central mediator of oxidative stress, ER stress, and inflammatory signaling in neurons. [@kadowaki2005]
<div class="infobox infobox-gene"> [@sakauchi2011]
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">MAP3K5 (ASK1)</th></tr>
<tr><td><strong>Gene Symbol</strong></td><td>MAP3K5</td></tr>
<tr><td><strong>Protein Name</strong></td><td>ASK1 (Apoptosis Signal-regulating Kinase 1)</td></tr>
<tr><td><strong>Full Name</strong></td><td>Mitogen-Activated Protein Kinase Kinase Kinase 5</td></tr>
<tr><td><strong>Chromosome</strong></td><td>6q26</td></tr>
<tr><td><strong>NCBI Gene ID</strong></td><td>[4217](https://www.ncbi.nlm.nih.gov/gene/4217)</td></tr>
<tr><td><strong>OMIM</strong></td><td>602476</td></tr>
<tr><td><strong>Ensembl ID</strong></td><td>ENSG00000197442</td></tr>
<tr><td><strong>UniProt ID</strong></td><td>[Q9UHD6](https://www.uniprot.org/uniprot/Q9UHD6)</td></tr>
<tr><td><strong>Protein Length</strong></td><td>1,374 amino acids</td></tr>
<tr><td><strong>Molecular Weight</strong></td><td>~155 kDa</td></tr>
<tr><td><strong>Associated Diseases</strong></td><td>[Alzheimer's Disease](/diseases/alzheimers-disease), [Parkinson's Disease](/diseases/parkinsons-disease), ALS, Stroke</td></tr>
</table>
</div>
Gene Structure and Expression
Genomic Organization
The MAP3K5 gene spans approximately 54 kb on chromosome 6q26 and contains multiple exons encoding the full-length protein. The gene is ubiquitously expressed with particularly high levels in the brain, heart, and liver. [@kuroda2011]
Brain Expression
In the central nervous system, ASK1 is highly expressed in:
- Cerebral cortex — pyramidal neurons
- Hippocampus — CA1-CA3 regions, dentate gyrus
- Substantia nigra — dopaminergic neurons
- Spinal cord — motor neurons
This neuronal expression pattern makes ASK1 particularly relevant to neurodegenerative processes. [@kadowaki2005]
Protein Structure and Regulation
Domain Architecture
ASK1 contains several functional domains:
N-terminal regulatory domain — Contains binding sites for thioredoxin (Trx) and 14-3-3 proteins
Kinase domain — Catalytic Ser/Thr kinase domain (aa 682-937)
C-terminal regulatory domain — Contains binding sites for TRAF proteins and negative regulatorsRegulation Mechanisms
ASK1 activity is tightly controlled through multiple mechanisms:
| Regulator | Mechanism | Effect |
|-----------|-----------|--------|
| Thioredoxin (Trx) | Covalent binding to N-terminal | Inhibits activation [@thioredoxin2005] |
| 14-3-3 proteins | Phosphorylation-dependent binding | Sequesters in cytoplasm |
| Hsp90 | Chaperone binding | Stabilizes protein |
| TRAF2/6 | K63-linked ubiquitination | Activates in response to TNF-α |
Activation Mechanism
Under non-stressed conditions, ASK1 is held in an inactive state through:
- Direct interaction with thioredoxin (Trx) at the N-terminus
- Binding to 14-3-3 proteins
- Formation of inactive complexes with negative regulators
Upon stress exposure, these inhibitory interactions are disrupted, leading to ASK1 autophosphorylation and activation. [@kuroda2011]
Signaling Pathways
Downstream Kinase Cascades
Mermaid diagram (expand to render)
JNK Pathway
ASK1 → MKK4/7 → JNK1/2/3 → c-Jun/ATF2 → AP-1 → Apoptosis
Key substrates:
- c-Jun (transcription factor)
- ATF2 (transcription factor)
- Bcl-2 family proteins (mitochondrial pathway)
- Synaptic proteins (synaptic dysfunction)
p38 Pathway
ASK1 → MKK3/6 → p38α/β/γ/δ → ATF2/CREB/MSK → Inflammation
Key functions:
- Pro-inflammatory cytokine production
- Microglial activation
- Tau phosphorylation
- Synaptic plasticity impairment
Role in Alzheimer's Disease
Aβ activates ASK1 through multiple mechanisms:
Direct oxidative stress — Aβ generates ROS that activate ASK1
Glial activation — Aβ triggers inflammatory signaling via microglia
ER stress — Aβ disrupts calcium homeostasis causing UPR activationNeuronal Apoptosis
Aβ-induced ASK1 activation mediates neuronal death through:
- JNK3-mediated pathway — Neuron-specific JNK3 phosphorylates c-Jun
- Mitochondrial apoptosis — ASK1 promotes Bax translocation
- Caspase activation — Upstream of caspase-3 activation
Synaptic Dysfunction
ASK1-JNK pathway impairs synaptic plasticity:
- Inhibits LTP in hippocampal neurons
- Promotes AMPA receptor internalization
- Disrupts dendritic spine morphology
Tau Pathology
The ASK1-p38 pathway contributes to tau hyperphosphorylation:
- p38 directly phosphorylates tau at AD-relevant sites (Thr181, Ser396)
- ASK1 deletion reduces tau pathology in animal models [@tau2022]
Therapeutic Implications
ASK1 represents a promising therapeutic target:
- Small molecule inhibitors (e.g., Selonsertib/GS-4997) in development
- Genetic deletion protects against Aβ toxicity in mice
- PET tracer [18F]ASK1-IN-6 enables visualization of ASK1 in AD brain [@ask1pet2024]
Role in Parkinson's Disease
Dopaminergic Neuron Vulnerability
SNc dopaminergic neurons show particular susceptibility to ASK1 activation:
High basal oxidative stress — Due to dopamine metabolism
Mitochondrial vulnerability — Complex I defects
Calcium influx — Pacemaker activity increases ROSToxin-Induced Models
In MPTP and 6-OHDA models:
- ASK1 is rapidly activated in dopaminergic neurons
- JNK3 mediates apoptotic cell death
- Inhibition protects against toxin-induced degeneration [@mptp2009]
α-Synuclein Toxicity
α-Syn aggregation activates ASK1-JNK pathway:
- Promotes neuronal apoptosis
- Contributes to spreading of pathology
- Synergizes with mitochondrial dysfunction
Mitochondrial Pathway
ASK1 links mitochondrial dysfunction to apoptosis:
- Directly interacts with mitochondrial proteins
- Promotes cytochrome c release
- Activates intrinsic apoptosis cascade
Therapeutic Potential
ASK1 inhibition may protect dopaminergic neurons:
- Preclinical studies show neuroprotection
- Broad therapeutic window
- Addresses multiple PD pathways
Role in ALS
Motor Neuron Vulnerability
Motor neurons are particularly susceptible to ASK1 activation:
- SOD1 mutations — Activate ASK1-JNK pathway [@sod1als2009]
- TDP-43 pathology — Triggers ER stress and ASK1
- Glutamate excitotoxicity — Activates via calcium dysregulation
Mutant SOD1 Models
In SOD1 transgenic mice:
- ASK1 activation precedes motor neuron loss
- Genetic deletion prolongs survival
- JNK3 mediates axonal degeneration
Therapeutic Targeting
ASK1 inhibitors:
- Protect motor neurons in culture
- Delay disease onset in animal models
- Could complement other therapeutic approaches
Role in Stroke/Ischemia
Ischemic Injury
ASK1 is strongly activated in ischemic brain:
- Rapid activation within hours of stroke
- Mediates neuronal death in penumbra
- Contributes to blood-brain barrier disruption
Therapeutic Window
ASK1 inhibition may provide:
- Neuroprotection if administered early
- Reduced infarct size
- Improved functional recovery
PET Imaging Tracer Development
[18F]ASK1-IN-6
A landmark development in ASK1 research is the first fluorine-18 PET radiotracer for ASK1 neuroimaging: [@ask1pet2024]
Key characteristics:
- First-in-class ASK1 radioligand
- High purity (>95%)
- Specific binding to ASK1 protein
- Higher binding in AD model mice
Preclinical results:
- Good binding specificity in vitro
- High binding across brain regions
- Potential for AD diagnosis
- Future applications in PD and MS
Clinical potential:
- Non-invasive ASK1 quantification
- Disease progression monitoring
- Therapeutic response assessment
- Patient stratification for ASK1 inhibitors
Therapeutic Targeting
Small Molecule Inhibitors
| Compound | Target | Stage | Notes |
|----------|--------|-------|-------|
| Selonsertib (GS-4997) | ASK1 | Phase II | Originally for NASH [@selonsertib2021] |
| 5Z-7-Oxozeaenol | ASK1 | Preclinical | Natural product analog |
| K811 | ASK1 | Preclinical | Selective inhibitor |
Challenges
- Achieving brain penetration
- Selectivity over other MAP3Ks
- Sustained inhibition vs. pathway modulation
Clinical Trials
Selonsertib (GS-4997) has been evaluated in:
- Non-alcoholic steatohepatitis (NASH) — Phase II/III
- Diabetic kidney disease — Phase II
- Potential for neurodegenerative disease trials
Cross-Links
- [JNK/p38 MAPK Signaling Pathway](/mechanisms/jnk-p38-mapk-neurodegeneration)
- [Apoptosis Pathway](/entities/apoptosis)
- [Oxidative Stress](/entities/oxidative-stress)
- [ER Stress/Unfolded Protein Response](/mechanisms/unfolded-protein-response)
- [Mitochondrial Dysfunction](/entities/mitochondrial-dysfunction)
- [Alzheimer's Disease](/diseases/alzheimers-disease)
- [Parkinson's Disease](/diseases/parkinsons-disease)
Disease Associations
Top DisGeNET gene-disease associations for this gene are listed below. Scores are numeric DisGeNET association scores (`score_max`) from the consolidated DisGeNET disease-gene association table; higher values indicate stronger aggregated evidence.
| Disease | DisGeNET score | Evidence sources | Supporting PMID count |
|---|---:|---|---:|
| Parkinson's disease | 0.213 | CTD_human/LHGDN | 2 |
| melanoma | 0.211 | BeFree/CTD_human | 2 |
| pancreatic cancer | 0.003 | BeFree/LHGDN | 2 |
| bone cancer | 0.003 | BeFree/LHGDN | 2 |
| type 2 diabetes mellitus | 0.003 | BeFree/GAD | 1 |
Source: DisGeNET-derived consolidated disease-gene associations (`dhimmel/disgenet`, gene symbol `MAP3K5`).
References
[Tobiume et al., ASK1 in apoptosis (2001)](https://doi.org/10.1038/sj.cdd.4400858)
[Kadowaki et al., ASK1 in neurodegeneration (2005)](https://doi.org/10.1111/j.1471-4159.2005.03248.x)
[Sakauchi et al., ASK1 in ALS (2011)](https://doi.org/10.1016/j.neuroscience.2011.04.027)
[Zhang et al., [18F]ASK1-IN-6 PET tracer (2024)](https://doi.org/10.1038/s41386-024-01990-8)
[Hayashi et al., ASK1 mediates neuronal death (2003)](https://doi.org/10.1523/jneurosci.23-22-07405.2003)
[Nagai et al., ASK1 in Parkinson's disease models (2007)](https://doi.org/10.1523/jneurosci.3110-06.2007)
[Ryu et al., ASK1 in Alzheimer's disease (2008)](https://doi.org/10.1016/j.neurobiolaging.2007.08.011)
[Kanungo et al., Inhibiting ASK1 as therapeutic strategy (2016)](https://doi.org/10.1016/j.tips.2016.07.006)
[Takeda et al., ASK1 in ER stress and neurodegeneration (2018)](https://doi.org/10.1111/bph.14423)
[Kuroda et al., ASK1 structural features and regulation (2011)](https://doi.org/10.1016/j.tibs.2011.06.005)
[Cho et al., Selonsertib in clinical trials (2021)](https://doi.org/10.1016/j.jhep.2021.01.021)
[Chambers et al., JNK3 as therapeutic target (2020)](https://doi.org/10.1016/j.tips.2020.03.002)
[Xia et al., MPTP activates ASK1-JNK pathway (2009)](https://doi.org/10.1523/jneurosci.4023-08.2009)
[Witan et al., Mutant SOD1 activates ASK1 in ALS (2009)](https://doi.org/10.1093/hmg/ddp373)
[Matsuzawa et al., Thioredoxin inhibits ASK1 (2005)](https://doi.org/10.1016/j.tcb.2005.06.003)
[Zhu et al., ASK1-p38 in tau pathology (2022)](https://doi.org/10.1038/s41386-022-01427-8)
This page was expanded with PET tracer research and comprehensive mechanistic content.Pathway Diagram
The following diagram shows the key molecular relationships involving MAP3K5 — Mitogen-Activated Protein Kinase Kinase Kinase 5 discovered through SciDEX knowledge graph analysis:
Mermaid diagram (expand to render)