JNK (c-Jun N-terminal Kinase) Protein

📖 Wiki Page

protein1129 wordssynced 2026-04-02

JNK (c-Jun N-terminal Kinase) Protein

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">JNK (c-Jun N-terminal Kinase) Protein</th>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>MAPK8 (JNK1), MAPK9 (JNK2), MAPK10 (JNK3)</td>
</tr>
<tr>
<td class="label">Chromosomal Location</td>
<td>MAPK8: 10q11.22, MAPK9: 5q35.1, MAPK10: 4q21.3</td>
</tr>
<tr>
<td class="label">UniProt IDs</td>
<td>P45983 (JNK1), P45984 (JNK2), P53779 (JNK3)</td>
</tr>
<tr>
<td class="label">Molecular Weight</td>
<td>~46-48 kDa per isoform</td>
</tr>
<tr>
<td class="label">Compound</td>
<td>Selectivity</td>
</tr>
<tr>
<td class="label">SP600125</td>
<td>Broad JNK inhibitor</td>
</tr>
<tr>
<td class="label">JNK-IN-8</td>
<td>Selective JNK inhibitor</td>
</tr>
<tr>
<td class="label">CC-401 (CC-930)</td>
<td>JNK inhibitor</td>
</tr>
<tr>
<td class="label">D-JNKI1</td>
<td>Peptide inhibitor</td>
</tr>
<tr>
<td class="label">Partner</td>
<td>Interaction Type</td>
</tr>
<tr>
<td class="label">MKK4</td>
<td>Phosphorylation</td>
</tr>
<tr>
<td class="label">MKK7</td>
<td>Phosphorylation</td>
</tr>
<tr>
<td class="label">c-Jun</td>
<td>Phosphorylation</td>
</tr>
<tr>
<td class="label">Bim (BCL2L11)</td>
<td>Phosphorylation</td>
</tr>
<tr>
<td class="label">Bcl-2</td>
<td>Phosphorylation</td>
</tr>
<tr>
<td class="label">Tau (MAPT)</td>
<td>Phosphorylation</td>
</tr>
<tr>
<td

...

JNK (c-Jun N-terminal Kinase) Protein

JNK (c-Jun N-terminal kinase, also known as MAPK8) is a stress-activated serine/threonine protein kinase belonging to the MAPK family. It is activated by cellular stress, inflammatory cytokines, and excitotoxicity, playing complex and context-dependent roles in neuronal survival and death. JNK is particularly implicated in [Alzheimer's disease](/diseases/alzheimers-disease), [Parkinson's disease](/diseases/parkinsons-disease), and other neurodegenerative disorders. [@bhujbal2025]

Pathway Diagram

Mermaid diagram (expand to render)

Gene and Isoforms

JNK exists as three isoforms: JNK1 and JNK2 are ubiquitously expressed, while JNK3 is predominantly neuronal and is the major isoform implicated in neurodegeneration. [@moro2023]

Structure

JNK proteins share a central kinase domain flanked by N- and C-terminal regions. The kinase domain adopts a typical bilobal structure characteristic of protein kinases. JNK is activated by dual phosphorylation on a Thr-X-Tyr (TXY) motif within its activation loop, catalyzed by upstream MKK4 and MKK7 kinases. The JNK3 isoform contains a unique 30-amino acid C-terminal extension that may confer neuronal specificity. [@reijnders2020]

Normal Function

Activation Mechanisms

JNK is activated through a canonical three-tier kinase cascade:

Upstream activation: Stress signals (UV radiation, oxidative stress, inflammatory cytokines) activate MAPKKKs such as MEKK1, MLK3, and TAK1

Intermediate phosphorylation: MAPKKs (MKK4/MKK7) phosphorylate JNK on Thr183 and Tyr185

Downstream signaling: Activated JNK translocates to the nucleus and phosphorylates transcription factors

Key Targets

c-Jun: Primary transcription factor substrate; phosphorylation at Ser63/Ser73 promotes AP-1-mediated gene transcription
Bim (BCL2L11): Pro-apoptotic BH3-only protein; JNK-mediated phosphorylation activates Bim
BAD: Pro-apoptotic protein; phosphorylation promotes cell death
[Tau](/proteins/tau): JNK phosphorylates tau at multiple sites including Ser396, Thr181, and Ser202 -- sites also targeted by other stress kinases in Alzheimer's disease [@yoshikawa2023]
ATF2: Stress-responsive transcription factor
Bcl-2: JNK can phosphorylate anti-apoptotic Bcl-2, reducing its protective function

Physiological Roles

In the healthy brain, JNK regulates:

Stress response and cellular adaptation to environmental insults
Neuronal development and differentiation
Synaptic plasticity and dendritic spine morphology
Regulation of neuronal excitability

Role in Alzheimer's Disease

JNK is strongly activated in [Alzheimer's disease](/diseases/alzheimers-disease) brains, particularly in regions vulnerable to neurodegeneration such as the hippocampus and prefrontal cortex. [@manoharan2023]

Neuronal Death Pathways

c-Jun activation: JNK-mediated phosphorylation of c-Jun promotes expression of pro-apoptotic genes
Bim activation: JNK phosphorylates Bim, relieving it from inhibition by Bcl-2/Bcl-xL, leading to mitochondrial outer membrane permeabilization (MOMP)
Caspase activation: JNK contributes to caspase-3 and caspase-9 activation through both intrinsic (mitochondrial) and extrinsic (death receptor) pathways

Tau Pathology

JNK directly phosphorylates [tau](/proteins/tau) at multiple pathological sites. In AD brains, p-JNK colocalizes with neurofibrillary tangles, and JNK activity correlates with Braak staging. JNK also phosphorylates the microtubule-associated protein tau (MAPT) gene promoter, potentially altering tau expression levels. [@yoshikawa2023]

Amyloid-Beta Interactions

[Aβ](/proteins/amyloid-beta) oligomers activate the JNK pathway through multiple mechanisms:

Aβ binds to various neuronal receptors (e.g., NMDA receptors, RAGE) that trigger upstream kinase activation
Aβ-induced oxidative stress activates MLK3-MKK4/7-JNK cascade
JNK activation contributes to Aβ-induced synaptic dysfunction and spine loss
Inhibition of JNK protects against Aβ-induced neuronal death in cultured neurons and animal models [@manoharan2023]

Role in Parkinson's Disease

JNK3 is the predominant isoform in dopaminergic neurons of the substantia nigra pars compacta and is implicated in [Parkinson's disease](/diseases/parkinsons-disease) through multiple mechanisms. [@kumar2021]

Dopaminergic Neuron Vulnerability

Mitochondrial dysfunction: JNK is activated by mitochondrial stress and contributes to MPTP/MPTP model dopaminergic toxicity
α-Synuclein aggregation: [α-synuclein](/proteins/alpha-synuclein) oligomers activate JNK; JNK activation in turn promotes α-synuclein aggregation and spread
Inflammation: Microglial JNK activation drives production of pro-inflammatory cytokines (IL-1β, TNF-α) that damage dopaminergic neurons

Neuroprotection Studies

JNK3 knockout mice show reduced dopaminergic neuron death in MPTP models
Peptide inhibitors of JNK (e.g., D-JNKI1) protect against 6-OHDA and MPTP toxicity
Small molecule JNK inhibitors (SP600125, JNK-IN-8) reduce neurodegeneration in PD animal models

Role in Other Neurodegenerative Disorders

Huntington's Disease

Mutant [huntingtin](/proteins/huntingtin) protein activates JNK through aberrant protein interactions and transcriptional dysregulation
JNK contributes to striatal neuron death through c-Jun activation and mitochondrial dysfunction
JNK inhibition reduces toxicity in HD models

Amyotrophic Lateral Sclerosis (ALS)

JNK is activated in motor neurons in ALS models and patient samples
Both SOD1 and TDP-43 mutations activate the JNK pathway
JNK inhibition delays disease onset and extends survival in SOD1 mouse models

Stroke and Traumatic Brain Injury

Ischemia rapidly and strongly activates JNK in affected brain regions
JNK contributes to both neuronal death and glial activation in stroke
JNK inhibitors reduce infarct volume when administered within therapeutic windows

Therapeutic Targeting

Small Molecule Inhibitors

Clinical Status

JNK inhibitors have been tested in clinical trials for inflammatory diseases (rheumatoid arthritis, COPD) with acceptable safety profiles, establishing a foundation for neurodegenerative applications. However, JNK inhibitors have not yet reached Phase 2/3 trials for AD or PD. [@bhujbal2025]

Challenges

Achieving CNS penetration with small molecule JNK inhibitors
Isoform selectivity (targeting JNK3 over JNK1/2 to reduce peripheral toxicity)
Timing of intervention -- JNK has both protective and destructive roles depending on context
Biomarker development for patient selection

Protein Interactions

References

[Bhujbal SP, Hah JM, Advances in JNK inhibitor development: therapeutic prospects in neurodegenerative diseases and fibrosis. Trends in Pharmacological Sciences (2025)](https://pubmed.ncbi.nlm.nih.gov/40920304/)

[Reijnders CDAM, et al., JNK-associated stellar photocoagulation in Alzheimer's disease. Cellular and Molecular Neurobiology (2020)](https://pubmed.ncbi.nlm.nih.gov/31834567/)

[Yoshikawa K, et al., c-Jun N-terminal kinase signaling in tauopathies. Frontiers in Aging Neuroscience (2023)](https://pubmed.ncbi.nlm.nih.gov/36910903/)

[Moro L, et al., Neuroprotective role of JNK inhibitors in neurodegenerative diseases. Neuroscience and Biobehavioral Reviews (2023)](https://pubmed.ncbi.nlm.nih.gov/37253831/)

[Kumar V, et al., JNK pathway in Parkinson's disease: molecular mechanisms and therapeutic targets. Molecular Neurobiology (2021)](https://pubmed.ncbi.nlm.nih.gov/33987958/)

[Manoharan S, et al., JNK pathway in amyloid-beta-induced neurotoxicity. Molecular and Cellular Neuroscience (2023)](https://pubmed.ncbi.nlm.nih.gov/37598901/)

Pathway Diagram

The following diagram shows the key molecular relationships involving JNK (c-Jun N-terminal Kinase) Protein discovered through SciDEX knowledge graph analysis:

Mermaid diagram (expand to render)

📖 View canonical wiki page →

JNK (c-Jun N-terminal Kinase) Protein

JNK (c-Jun N-terminal Kinase) Protein

JNK (c-Jun N-terminal Kinase) Protein

Pathway Diagram

Gene and Isoforms

Structure

Normal Function

Activation Mechanisms

Key Targets

Physiological Roles

Role in Alzheimer's Disease

Neuronal Death Pathways

Tau Pathology

Amyloid-Beta Interactions

Role in Parkinson's Disease

Dopaminergic Neuron Vulnerability

Neuroprotection Studies

Role in Other Neurodegenerative Disorders

Huntington's Disease

Amyotrophic Lateral Sclerosis (ALS)

Stroke and Traumatic Brain Injury

Therapeutic Targeting

Small Molecule Inhibitors

Clinical Status

Challenges

Protein Interactions

See Also

References

Pathway Diagram