MAP2K5

MAP2K5 (MEK5)

Gene Overview

<div class="infobox infobox-gene">
<div class="infobox-header">Gene Information</div>

<table>
<tr><th>Symbol</th><td>MAP2K5</td></tr>
<tr><th>Full Name</th><td>Mitogen-Activated Protein Kinase Kinase 5</td></tr>
<tr><th>Alias</th><td>MEK5</td></tr>
<tr><th>Chromosome</th><td>15q23</td></tr>
<tr><th>NCBI Gene ID</th><td>5608</td></tr>
<tr><th>UniProt ID</td><td>Q13131</td></tr>
<tr><th>Ensembl ID</th><td>ENSG00000108691</td></tr>
<tr><th>Protein Family</th><td>MAP kinase kinase (MEK) family</td></tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/amyotrophic-lateral-sclerosis" style="color:#ef9a9a">Amyotrophic Lateral Sclerosis</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">6 edges</a></td>
</tr>
</table>
</div>

Introduction

MAP2K5 (also known as MEK5) encodes mitogen-activated protein kinase kinase 5, a dual-specificity protein kinase that serves as the specific upstream activator of ERK5 (also known as Big MAP Kinase 1, BMK1). The MAP2K5-ERK5 signaling axis represents a distinct MAPK cascade that plays critical roles in neuronal development, synaptic plasticity, cell survival, and stress responses. Unlike other MAP kinase pathways, the MEK5-ERK5 pathway has unique functions in the nervous system that are particularly relevant to neurodegenerative disease pathogenesis and neuroprotection.

MAP2K5 (MEK5)

Gene Overview

<div class="infobox infobox-gene">
<div class="infobox-header">Gene Information</div>

<table>
<tr><th>Symbol</th><td>MAP2K5</td></tr>
<tr><th>Full Name</th><td>Mitogen-Activated Protein Kinase Kinase 5</td></tr>
<tr><th>Alias</th><td>MEK5</td></tr>
<tr><th>Chromosome</th><td>15q23</td></tr>
<tr><th>NCBI Gene ID</th><td>5608</td></tr>
<tr><th>UniProt ID</td><td>Q13131</td></tr>
<tr><th>Ensembl ID</th><td>ENSG00000108691</td></tr>
<tr><th>Protein Family</th><td>MAP kinase kinase (MEK) family</td></tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/amyotrophic-lateral-sclerosis" style="color:#ef9a9a">Amyotrophic Lateral Sclerosis</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">6 edges</a></td>
</tr>
</table>
</div>

Introduction

MAP2K5 (also known as MEK5) encodes mitogen-activated protein kinase kinase 5, a dual-specificity protein kinase that serves as the specific upstream activator of ERK5 (also known as Big MAP Kinase 1, BMK1). The MAP2K5-ERK5 signaling axis represents a distinct MAPK cascade that plays critical roles in neuronal development, synaptic plasticity, cell survival, and stress responses. Unlike other MAP kinase pathways, the MEK5-ERK5 pathway has unique functions in the nervous system that are particularly relevant to neurodegenerative disease pathogenesis and neuroprotection.

The MEK5 protein consists of 471 amino acids and contains a kinase domain with characteristic motifs required for dual-specificity phosphorylation. MEK5 is distinguished from other MAP2K family members (MEK1/2, MEK3/6, MEK4/7) by its highly specific substrate specificity for ERK5, as it does not efficiently phosphorylate other MAPKs. This specificity makes MEK5 a critical regulator of ERK5-mediated signaling in neurons and glia.

The MAPK/ERK5 Signaling Pathway

Pathway Architecture

The MAP2K5-ERK5 pathway constitutes one of five major MAPK cascades in mammalian cells:[@cavalli2023]

Upstream Regulators

MAP2K5 is activated by MAPKKK proteins, primarily MEKK2 (MAP3K2) and MEKK3 (MAP3K3), which respond to various extracellular signals:[@nithianandarajahjones2022]

• Growth factors: BDNF, NGF, EGF
• Cellular stress: Oxidative stress, endoplasmic reticulum stress
• Synaptic activity: Glutamate receptor activation
• Inflammatory signals: Cytokine signaling in glia

Downstream Targets

Activated ERK5 phosphorylates multiple transcription factors and effectors:[@lim2022]

• MEF2 family: Myocyte enhancer factor 2 (MEF2A-D)
• CREB: cAMP response element-binding protein
• c-Fos: Immediate early gene product
• SGK: Serum- and glucocorticoid-induced kinase
• BIM: Pro-apoptotic Bcl-2 family protein

Biological Functions in the Nervous System

Neuronal Development

MAP2K5-ERK5 signaling is essential for multiple aspects of brain development:[@peyrachel2019]

Axon Growth and Guidance:

• Regulates axonal extension and branching
• Controls growth cone dynamics
• Mediates guidance cue responses
• Essential for proper circuit formation

• Promotes neuronal fate specification
• Controls dendritic arborization
• Regulates synapse formation
• Essential for cortical development

Synaptic Plasticity

The MEK5-ERK5 pathway plays critical roles in learning and memory:[@harada2021][@tang2021]

Long-Term Potentiation (LTP):

• Required for LTP induction in hippocampal neurons
• Controls AMPA receptor trafficking
• Regulates spine morphogenesis
• Mediates activity-dependent gene expression

• ERK5 activation in hippocampus during memory tasks
• CREB phosphorylation and gene transcription
• Consolidation of synaptic changes
• Long-term memory stability

Neuroprotection

MEK5-ERK5 signaling mediates neuroprotective responses:[@finegan2021][@sun2023]

Oxidative Stress Response:

• Activation of antioxidant gene expression
• Protection against ROS-induced cell death
• Maintenance of mitochondrial function
• Upregulation of survival proteins

• ERK5 is downstream of TrkB receptor
• Mediates BDNF's neuroprotective effects
• Promotes neuronal survival in injury models[@zhao2023]
• Essential for trophic factor signaling

• Phosphorylation and inhibition of pro-apoptotic BIM
• Activation of MEF2-dependent survival genes
• Cross-talk with PI3K/Akt pathway
• Regulation of caspase activity

Mitochondrial Function

ERK5 regulates mitochondrial biology in neurons:[@yan2019]

• Controls mitochondrial biogenesis
• Regulates mitochondrial dynamics (fusion/fission)
• Maintains mitochondrial membrane potential
• Protects against mitochondrial apoptosis

Disease Associations

Alzheimer's Disease

The MEK5-ERK5 pathway is implicated in multiple aspects of AD pathogenesis:[@wang2022][@johnson2019]

Amyloid-Beta Effects:

• Aβ induces ERK5 activation in neurons
• Paradoxically, ERK5 activation can be both protective and detrimental
• MEK5-ERK5 signaling in microglial activation
• Regulation of inflammatory responses

• ERK5 can phosphorylate tau at multiple sites
• GSK-3β and ERK5 collaboration in tau hyperphosphorylation
• Role in tau aggregation and spread
• Therapeutic targeting considerations

• ERK5 is required for synaptic plasticity deficits in AD models
• Memory consolidation impairments
• dendritic spine loss mechanisms

• MEK5 inhibitors as AD therapeutic strategy
• Targeting ERK5 activation to reduce neuroinflammation
• Modulating tau pathology through ERK5

Parkinson's Disease

MAP2K5-ERK5 signaling is relevant to PD pathophysiology:[@chen2020]

Dopaminergic Neuron Survival:

• ERK5 activation protects dopaminergic neurons
• Neuroprotective effects against oxidative stress
• Response to mitochondrial toxins (MPTP, 6-OHDA)
• Role in L-DOPA-induced dyskinesia

• ERK5 activation in response to α-synuclein aggregation
• Potential role in protein clearance pathways
• Involvement in cellular stress responses

• MEK5-ERK5 modulators for PD treatment
• Neuroprotection strategies

Amyotrophic Lateral Sclerosis

Recent research has identified MEK5-ERK5 in ALS:[@zhang2023]

Motor Neuron Survival:

• MEK5 is protective in SOD1 models
• ERK5 activation promotes survival
• Cross-talk with other survival pathways

• Targeting MEK5 as ALS therapeutic strategy

Other Neurodegenerative Conditions

Huntington's Disease:

• ERK5 dysregulation in HD models
• Role in mutant huntingtin toxicity
• Therapeutic targeting potential

• ERK5 activation in ischemic preconditioning
• Neuroprotection in stroke models
• Recovery and plasticity mechanisms

Expression Patterns

Brain Expression

MAP2K5 is widely expressed in the brain:

• High expression: Hippocampus (CA1-3, dentate gyrus), cerebral cortex, cerebellum
• Cellular localization: Neurons (soma, dendrites, synapses), some glial cells
• Developmental regulation: Higher expression during development
• Activity-dependent: Synaptic activity modulates expression

Cell Type Specificity

• Neurons: Primary expression in excitatory and inhibitory neurons
• Astrocytes: Lower expression, upregulated in injury
• Microglia: Inducible expression in activated states
• Oligodendrocytes: Present in myelin-producing cells

Genetic Variants

Known Variants

MAP2K5 genetic variants have been associated with:

• Psychiatric disorders: Depression, antidepressant response[@stuart2021]
• Neurological conditions: Stroke susceptibility
• Cancer: Some somatic mutations in tumors
• Development: Rare developmental disorders

Clinical Significance

• Pharmacogenomics of MEK inhibitors
• Predictors of treatment response
• Potential biomarker applications

Therapeutic Implications

MEK5 as Drug Target

The specificity of MEK5 for ERK5 makes it an attractive target:[@li2022]

Small Molecule Inhibitors:

• BIX02188: Selective MEK5 inhibitor
• BIX02189: MEK5 inhibitor
• Compound 43: ERK5 inhibitor

• Neurodegeneration prevention
• Cancer therapy (brain penetrant versions)
• Inflammatory conditions

Challenges

• Blood-brain barrier penetration
• Optimal timing of intervention
• Pathway compensation mechanisms

Research Directions

Unresolved Questions

Emerging Areas

• Single-cell studies: Cell-type specific ERK5 functions
• Optogenetics: Light-controlled ERK5 activation
• Biomarkers: ERK5 activity as disease biomarker
• Combination therapy: MEK5 modulation with other targets

Protein Structure and Function

Structural Features

The MEK5 protein contains several key structural features essential for its function:

Kinase Domain:

• Dual-specificity protein kinase domain (residues 50-300)
• ATP-binding site in the active site cleft
• Phosphorylation sites for activation (S218, T222)
• DFG motif for substrate recognition

• N-terminal docking domain for ERK5 interaction
• C-terminal region for protein-protein interactions
• Nuclear localization signals
• Nuclear export signals

• MEK5α: Full-length isoform (471 aa)
• MEK5β: Truncated isoform lacking N-terminal region
• Different tissue distribution and function

Catalytic Mechanism

MEK5 phosphorylates ERK5 through a canonical kinase mechanism:

Protein-Protein Interactions

MEK5 interacts with multiple proteins to execute its functions:

• MEKK2/3: Upstream MAPKKK activators
• ERK5: Primary substrate
• ERK5 nuclear carriers: Chaperones for nuclear import
• Phosphatases: MKP5, MKP7 for pathway termination
• Scaffold proteins: KSR for pathway optimization

Animal Models

Knockout Studies

MAP2K5 knockout mice have provided insights into its functions:

MEK5 Knockout:

• Embryonic lethality around E9.5-10.5
• Defects in heart development
• Impaired neuronal development
• Vascular abnormalities

• Neuron-specific deletion: Learning and memory deficits
• Glia-specific deletion: Altered inflammatory responses
• Muscle-specific deletion: Metabolic phenotypes

Transgenic Models

Transgenic and knock-in models have been developed:

ERK5 Transgenic:

• Neuronal ERK5 overexpression: Enhanced LTP
• Constitutive ERK5: Developmental abnormalities
• Dominant-negative ERK5: Impaired memory

• AD models with MEK5 modulation: Altered pathology
• PD models with MEK5 manipulation: Changed outcomes
• Stroke models: Ischemic preconditioning effects

Behavioral Studies

MEK5-ERK5 signaling in behavior:

Learning and Memory:

• MEK5/ERK5 knockouts: Impaired spatial memory
• Constitutive activation: Enhanced memory
• Specific brain region manipulation: Distinct effects

• Cerebellar MEK5: Motor coordination
• Basal ganglia: Habit formation
• Motor neuron ERK5: Function in ALS models

• Depression-related behaviors
• Anxiety-like behaviors
• Response to stress

Signaling Pathway Integration

Cross-talk with Other MAPK Pathways

MEK5-ERK5 interacts with other MAPK cascades:

ERK1/2 Pathway:

• Parallel activation by growth factors
• Shared downstream targets (CREB)
• Distinct temporal patterns
• Different cellular outcomes

• Often opposing functions
• Stress-activated vs growth factor activated
• Cell fate decisions: survival vs death
• Coordination in development

• Similar stress-activated pattern
• Common substrates
• Complementary functions

Integration with Other Signaling

MEK5-ERK5 integrates with multiple pathways:

cAMP/PKA:

• Cross-activation of CREB
• Shared target genes
• Modulation by cAMP

• Co-activation by growth factors
• Parallel survival signaling
• Intersection at BAD phosphorylation

• Activity-dependent activation
• Calmodulin interactions
• Activity-dependent transcription

Spatial Signaling

MEK5-ERK5 has distinct spatial pools:

Nuclear ERK5:

• Transcriptional regulation
• Gene expression programs
• Long-term effects

• Cytoskeletal effects
• Immediate responses
• Local signaling

• Synaptic plasticity
• Local translation
• Spine function

Clinical Perspectives

Biomarker Potential

ERK5 activity as a biomarker:

Diagnostic:

• Disease state identification
• Subtype classification
• Progression monitoring

• Outcome prediction
• Treatment response
• Survival markers

• Target engagement
• Pathway modulation
• Efficacy measures

Therapeutic Development

MEK5-ERK5 pathway targeting strategies:

Direct MEK5 Modulators:

• Agonists for neuroprotection
• Antagonists for specific contexts
• Isoform-specific compounds

• Direct ERK5 inhibitors
• Allosteric modulators
• Substrate competitors

• With other neuroprotective agents
• With anti-inflammatory drugs
• With disease-modifying therapies

Clinical Trials

Current status of MEK5-ERK5 targeted therapies:

• Preclinical validation ongoing
• CNS-penetrant compounds in development
• Biomarker development for patient selection
• Combination trial designs in planning

Biochemical Properties

Enzyme Kinetics

Substrate Specificity:

• High specificity for ERK5
• Km for ERK5: ~0.5 μM
• Vmax: ~100 pmol/min/mg

• Autophosphorylation on activation loop
• Feedback phosphorylation by ERK5
• Phosphatase-mediated deactivation

Post-Translational Modifications

Phosphorylation:

• S218 and T222: Activation loop phosphorylation
• Multiple serine/threonine sites for regulation

• Acetylation: Affects kinase activity
• Ubiquitination: Protein turnover
• Sumoylation: Localization changes

Protein Complexes

MEK5 is found in various complexes:

Signaling Complexes:

• MEKK2/3-MEK5-ERK5 modules
• Scaffold protein complexes (KSR)
• Nuclear import complexes

• Transcription factor complexes
• Mitochondrial complexes
• Synaptic complexes

Evolutionary Conservation

Species Conservation

MAP2K5 is evolutionarily conserved:

• Mammals: Highly conserved (95%+ identity)
• Birds: ~85% identity
• Fish: ~70% identity
• Drosophila: Homolog DSOR1
• C. elegans: Homolog mek-2

Functional Conservation

The MEK5-ERK5 pathway is functionally conserved across species:

• Developmental functions
• Stress responses
• Synaptic plasticity

Pathophysiological Mechanisms

Oxidative Stress

MEK5-ERK5 in oxidative stress:

Direct Effects:

• ROS activates MEKK2/3
• MEK5-ERK5 activation
• Antioxidant gene expression

• Mitochondrial protection
• DNA damage repair
• Protein homeostasis

Endoplasmic Reticulum Stress

The pathway in ER stress:

• IRE1-MEKK2-MEK5-ERK5 axis
• Unfolded protein response
• Cell survival signaling

Mitochondrial Dysfunction

ERK5 in mitochondrial health:

• Biogenesis regulation
• Dynamics control
• Quality control pathways
• Apoptosis regulation

Treatment Approaches

Pharmacological Modulation

Activators:

• Brain-penetrant MEK5 agonists
• Upstream receptor agonists
• Exercise mimetics

• Selective MEK5 inhibitors
• ERK5 inhibitors
• Combination approaches

Non-Pharmacological

Lifestyle Interventions:

• Exercise enhances ERK5
• Dietary factors
• Stress management

• Gene therapy
• Cell-based therapy
• Optogenetic stimulation

Future Directions

Research Priorities

Therapeutic Potential

• Neuroprotection in AD/PD
• Stroke prevention
• ALS treatment
• Traumatic brain injury

Interactions with Other Proteins

Kinase Interactions

MEK5 interacts with multiple kinases:

Upstream Kinases:

• MEKK2 (MAP3K2): Primary activator
• MEKK3 (MAP3K3): Alternative activator
• TAK1 (MAP3K7): Stress-activated

• Potential cross-talk with MEK1/2
• Shared upstream regulators
• Parallel pathway interaction

Non-Kinase Interactions

Transcription Factors:

• MEF2 family: Primary ERK5 targets
• CREB: Phosphorylation target
• c-Fos: Induction target

• KSR: Scaffold for MAPK cascade
• JIP proteins: Alternative scaffolds
• MP1: Endosomal scaffolding

• Phosphatases: MKP5, MKP7
• Ubiquitin ligases: Degradation control
• Chaperones: Protein folding

Disease Mechanisms

Neurodegeneration Initiation

MEK5-ERK5 in disease onset:

Early Events:

• Subtle synaptic changes
• Early mitochondrial dysfunction
• Initial transcriptional changes

• Sustained pathway dysregulation
• Inflammatory response activation
• Protein aggregation interaction

Cellular Vulnerability

Neuronal vulnerability factors:

Intrinsic Factors:

• High metabolic demand
• Limited regenerative capacity
• Excitable state sensitivity

• [Neuroinflammation](/mechanisms/neuroinflammation) Glial support changes
• Vascular factors

Therapeutic Target Considerations

Target Validation

Evidence supporting MEK5 as target:

• Pathway activation in disease models
• Neuroprotective effects of pathway activation
• Correlation with disease severity

Drug Development Challenges

Chemistry Challenges:

• Achieving brain penetration
• Maintaining selectivity
• Balancing agonist vs antagonist effects

• Complex temporal requirements
• Cell-type specificity needs
• Pathway compensation issues

Combination Strategies

Rationale for combinations:

• MEK5 + other neuroprotective pathways
• MEK5 + anti-inflammatory approaches
• MEK5 + disease-modifying agents

Models and Systems

In Vitro Models

Cell culture systems for studying MEK5:

Primary Neurons:

• Hippocampal neurons: Synaptic plasticity studies
• Cortical neurons: Development studies
• Dopaminergic neurons: PD models

• PC12 cells: Differentiation studies
• SH-SY5Y: Neurodegeneration models
• N2A cells: Molecular mechanisms

In Vivo Models

Animal models for MEK5-ERK5:

Mouse Models:

• Conditional knockouts
• Transgenic overexpression
• Disease model crosses

• Developmental studies
• CNS visualization
• Drug screening

Organoid Systems

Human models:

• Brain organoids: Development
• Disease-specific iPSCs
• Microfluidic devices

Measurement and Detection

Activity Assays

Measuring MEK5-ERK5 activity:

Kinase Assays:

• In vitro kinase assays
• Immunoprecipitation kinase assays
• Fluorescence-based detection

• Phospho-ERK5 antibodies
• Activity-based probes
• Reporter constructs

Expression Analysis

Measuring expression:

mRNA:

• qRT-PCR
• RNAseq
• In situ hybridization

• Western blot
• Immunohistochemistry
• ELISA

See Also

• [ERK5 Signaling Pathway](/mechanisms/erk5-signaling-pathway)
• [MAPK Signaling in Neurodegeneration](/mechanisms/mapk-signaling-neurodegeneration)
• [Neuroprotection Mechanisms](/mechanisms/neuroprotection-mechanisms)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)
• [BDNF Signaling](/mechanisms/bdnf-signaling-pathway)

Allen Brain Atlas Data

Gene Expression

• Cerebral cortex - Layer 5 pyramidal neurons
• Hippocampus - CA1 and CA3 regions
• Cerebellum - Purkinje cells
• Olfactory bulb - Mitral cells

Brain Region Expression Levels

Single-Cell Expression

• Pyramidal neurons
• Purkinje cells
• Some interneurons

External Resources

• [Allen Brain Atlas - MAP2K5 Expression](https://portal.brain-map.org/)
• [Allen Brain Cell Atlas](https://portal.brain-map.org/explore/classes/nucleus)

References

External Links

• [NCBI Gene - MAP2K5](https://www.ncbi.nlm.nih.gov/gene/5608)
• [UniProt - Q13131](https://www.uniprot.org/uniprot/Q13131)
• [Ensembl - ENSG00000108691](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000108691)
• [KEGG Pathway - MAPK signaling](https://www.genome.jp/kegg/pathway/map04010.html)
• [PubMed](https://pubmed.ncbi.nlm.nih.gov/)