title: MAP2K3 - Mitogen-Activated Protein Kinase Kinase 3
category: gene
MAP2K3 — Mitogen-Activated Protein Kinase Kinase 3
<div class="infobox infobox-gene">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">Mitogen-Activated Protein Kinase Kinase 3</th></tr>
<tr><td><strong>Gene Symbol</strong></td><td>MAP2K3</td></tr>
<tr><td><strong>Full Name</strong></td><td>Mitogen-Activated Protein Kinase Kinase 3</td></tr>
<tr><td><strong>Chromosome</strong></td><td>6p21.3</td></tr>
<tr><td><strong>NCBI Gene ID</strong></td><td>[5606](https://www.ncbi.nlm.nih.gov/gene/5606)</td></tr>
<tr><td><strong>OMIM</strong></td><td>[602314](https://www.omim.org/entry/602314)</td></tr>
<tr><td><strong>Ensembl ID</strong></td><td>ENSG00000099695</td></tr>
<tr><td><strong>UniProt ID</strong></td><td>[P46734](https://www.uniprot.org/uniprot/P46734)</td></tr>
<tr><td><strong>Associated Diseases</strong></td><td>Alzheimer's Disease, Parkinson's Disease, ALS, Cancer</td></tr>
</table>
</div>
Overview
MAP2K3 (Mitogen-Activated Protein Kinase Kinase 3), also known as MEK3, is a dual-specificity protein kinase that serves as a critical upstream activator of the p38 MAPK signaling pathway.<sup>[1]</sup> It phosphorylates and activates p38 alpha, beta, and gamma MAP kinases in response to cellular stresses including oxidative stress, inflammatory cytokines, UV radiation, and ischemic injury.<sup>[2]</sup> The MAP2K3/p38 pathway plays pivotal roles in regulating cellular processes such as proliferation, differentiation, [apoptosis](/entities/apoptosis), and inflammatory responses, all of which are dysregulated in neurodegenerative diseases.<sup>[3]</sup> In the brain, MAP2K3 is expressed in both [neurons](/entities/neurons) and glial cells, where its activation contributes to neuroinflammation, [tau](/proteins/tau) pathology, and synaptic dysfunction in Alzheimer's disease (AD), dopaminergic neuron death in Parkinson's disease (PD), and motor neuron degeneration in amyotrophic lateral sclerosis (ALS).<sup>[4]</sup>
Molecular Mechanism
MAP2K3 (MEK3) is a mitogen-activated protein kinase kinase that activates p38 MAP kinase signaling pathways. It is a dual-specificity kinase that phosphorylates and activates MAP kinase 14 (p38-alpha), MAP kinase 11 (p38-beta), and MAP kinase 12 (p38-gamma). MAP2K3 is activated by various cellular stresses including oxidative stress, inflammatory cytokines, and UV radiation. It plays important roles in cell proliferation, differentiation, apoptosis, and inflammatory responses. MAP2K3 is itself activated by MAP3Ks including MEKK1-4 and TAK1.
The MAP2K3/p38 signaling cascade:
Cellular Stress → MAP3K Activation → MAP2K3 (MEK3) Activation → p38 MAPK Phosphorylation → Cellular Responses
Key downstream effects include:
- Activation of transcription factors (ATF2, CREB, NF-κB)
- Regulation of cytokine production
- Control of cell cycle and apoptosis
- Modulation of synaptic plasticity
Role in Alzheimer's Disease
In Alzheimer's disease, MAP2K3/p38 signaling is activated in neurons surrounding amyloid plaques and contributes to disease pathogenesis through multiple mechanisms:<sup>[4]</sup><sup>[5]</sup>
- Tau pathology: p38-mediated phosphorylation of tau at multiple sites promotes tau hyperphosphorylation and NFT formation
- Synaptic dysfunction: p38 activation impairs synaptic plasticity and memory consolidation
- Neuroinflammation: Glial p38 activation drives pro-inflammatory cytokine release
- Amyloid toxicity: p38 MAPK mediates amyloid-beta-induced neuronal apoptosis
Role in Parkinson's Disease
In Parkinson's disease, MAP2K3/p38 signaling contributes to dopaminergic neuron degeneration:<sup>[6]</sup>
- Oxidative stress: p38 activation in response to mitochondrial toxins and ROS
- Neuroinflammation: Activated microglia release inflammatory mediators via p38
- Alpha-synuclein pathology: p38 promotes alpha-synuclein phosphorylation and aggregation
- Mitochondrial dysfunction: p38 signaling contributes to mitochondrial permeability transition
Role in ALS
In amyotrophic lateral sclerosis, MAP2K3/p38 activation in motor neurons and glial cells contributes to:
- Motor neuron apoptosis
- Excitotoxicity through glutamate transporter dysfunction
- Neuroinflammation in the spinal cord
- Protein aggregate handling
Therapeutic Implications
MAP2K3 and its downstream p38 MAPK represent important therapeutic targets:
Small Molecule Inhibitors
- SB203580: First-generation p38 inhibitor (limited CNS penetration)
- PH-797804: Improved selectivity and CNS penetration
- LY2228820: Clinical candidate for neuroinflammation
Challenges
- Limited CNS penetration of early inhibitors
- Side effects from systemic inflammation suppression
- Compensatory mechanisms limiting long-term efficacy
Emerging Approaches
- Brain-targeted p38 inhibitors
- Combination therapies targeting multiple MAPK pathways
- Downstream effectors rather than kinase inhibition
Expression Pattern
MAP2K3 is expressed in most tissues, with high expression in brain, heart, and skeletal muscle. In the brain, it is expressed in neurons and glia. Expression and activation are increased in various brain regions affected by neurodegenerative diseases, including:
- [Hippocampus](/brain-regions/hippocampus) (CA1, CA3 regions)
- [Substantia nigra](/brain-regions/substantia-nigra) (dopaminergic neurons)
- Motor cortex and spinal cord (motor neurons)
Genetic Associations
While MAP2K3 is not typically mutated in familial neurodegenerative diseases, polymorphisms in the MAP2K3 gene have been associated with:
- Age of onset in sporadic Parkinson's disease
- Cognitive decline trajectory in Alzheimer's disease
- Susceptibility to sporadic ALS
Biomarker Potential
MAP2K3/p38 pathway activation markers in cerebrospinal fluid (CSF) and blood are being studied as potential biomarkers:
- Phospho-p38 levels: Correlate with disease severity in AD and PD
- MAP2K3 expression: Elevated in peripheral blood mononuclear cells (PBMCs) in neurodegenerative disease
- CSF cytokine profiles: Downstream effects of MAP2K3 activation reflect neuroinflammation state
See Also
- [Alzheimer's Disease](/diseases/alzheimers-disease)
- [Parkinson's Disease](/diseases/parkinsons-disease)
- [Amyotrophic Lateral Sclerosis](/diseases/als)
- [p38 MAPK](/proteins/p38-mapk)
- [MAP2K3 Protein](/proteins/map2k3-protein)
- [Neuroinflammation](/mechanisms/neuroinflammation)
References
[Cuenda & Rousseau, p38 MAP kinases in neuronal signaling (2007)](https://doi.org/10.1016/j.tcb.2007.09.001)
[Bowling & Paxinou, Regulation of MAP kinases in neurodegenerative disease (2005)](https://pubmed.ncbi.nlm.nih.gov/15894173/)
[Kim et al., p38 MAPK in neurodegeneration (2002)](https://doi.org/10.1002/j.1552-4604.2002.tb06001.x)
[Kumar et al., MAP2K3 in neuroinflammation (2015)](https://doi.org/10.1016/j.neuropharm.2014.12.010)
[Correnti et al., p38 MAPK inhibitors for Alzheimer's disease (2022)](https://doi.org/10.1016/j.pharmthera.2022.108100)
[Munoz & Amaro, MAP2K3 in Parkinson's disease models (2023)](https://doi.org/10.1111/jnc.15789)