EIF2AK2 — Eukaryotic Translation Initiation Factor 2 Alpha Kinase 2
Overview
Mermaid diagram (expand to render)
EIF2AK2 (Eukaryotic Translation Initiation Factor 2 Alpha Kinase 2), more commonly known as PKR (Protein Kinase R), is a serine/threonine kinase that serves as a critical sensor of cellular stress and a key activator of the integrated stress response (ISR). Originally characterized for its role in antiviral defense, where it is activated by double-stranded RNA to inhibit viral protein synthesis, PKR has emerged as an important player in neurodegenerative disease pathogenesis. The kinase is activated in Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis, where it contributes to synaptic dysfunction, protein aggregation, and neuronal cell death.
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<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">PKR (EIF2AK2) Kinase</th></tr>
<tr><td><strong>Gene Symbol</strong></td><td>EIF2AK2</td></tr>
<tr><td><strong>Protein Name</strong></td><td>Protein Kinase R (PKR)</td></tr>
<tr><td><strong>Chromosome</strong></td><td>2p22.2</td></tr>
<tr><td><strong>NCBI Gene ID</strong></td><td>[2025](https://www.ncbi.nlm.nih.gov/gene/2025)</td></tr>
<tr><td><strong>OMIM</strong></td><td>603013</td></tr>
<tr><td><strong>Ensembl ID</strong></td><td>ENSG00000055332</td></tr>
<tr><td><strong>UniProt ID</strong></td><td>[P19589](https://www.uniprot.org/uniprot/P19589)</td></tr>
<tr><td><strong>Protein Family</strong></td><td>eIF2alpha kinase family</td></tr>
<tr><td><strong>Subcellular Location</strong></td><td>Cytoplasm, nucleus (upon activation)</td></tr>
<tr><td><strong>Associated Diseases</strong></td><td>Alzheimer's Disease, Parkinson's Disease, Huntington's Disease, ALS, Viral Encephalitis</td></tr>
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Gene Structure and Evolution
Genomic Organization
The EIF2AK2 gene is located on chromosome 2 (2p22.2), spanning approximately 50 kb of genomic DNA. The gene consists of 16 exons that encode a protein of 551 amino acids. The promoter contains interferon-stimulated response elements (ISRE), NF-κB binding sites, and p53 response elements.
Evolutionary Conservation
EIF2AK2 shows strong evolutionary conservation:
- Mammalian orthologs share >90% amino acid identity
- The kinase domain is highly conserved
- The dsRNA-binding domain is conserved across species
Protein Structure and Function
Domain Architecture
EIF2AK2 contains several functional domains:
N-terminal dsRNA-binding domain (dsRBD): Recognizes viral and cellular dsRNA
Regulatory domain: Contains autophosphorylation sites
Kinase domain (C-terminal): Catalytic serine/threonine kinase activityCatalytic Mechanism
EIF2AK2 catalyzes eIF2α phosphorylation:
Activation: dsRNA binding causes conformational change
Autophosphorylation: Trans-autophosphorylation on multiple sites
Substrate recognition: Binds eIF2α through specific interactions
Catalysis: Transfers phosphate to Ser51 of eIF2αFunctions in Cellular Stress
PKR serves multiple cellular functions:
Translation regulation:
- eIF2α phosphorylation attenuates general translation
- Selective translation of stress response genes (ATF4, CHOP, GADD34)
Apoptosis regulation:
- Prolonged activation leads to apoptosis
- Direct activation of caspase pathways
Expression and Localization
Tissue Distribution
EIF2AK2 shows ubiquitous expression:
High expression:
- Brain: Neurons, astrocytes, microglia (region-specific)
- Lung: Epithelial cells, alveolar macrophages
- Spleen: Lymphocytes, macrophages
Subcellular Localization
EIF2AK2 localizes primarily to the cytoplasm:
- Cytoplasmic distribution: Resting state
- Nuclear translocation: Upon activation
Role in Neurodegeneration
Integrated Stress Response
PKR is a key activator of the integrated stress response (ISR):
Stress sensing: Multiple stress modalities activate PKR
eIF2α phosphorylation: Central ISR mechanism
Translational reprogramming: Adaptation to stressAlzheimer's Disease (AD)
PKR contributes to AD through multiple mechanisms:
Protein aggregation:
- eIF2α phosphorylation affects amyloid processing
- Translation attenuation disrupts protein homeostasis
Synaptic dysfunction:
- Reduced synaptic protein synthesis
- Impaired memory consolidation
Parkinson's Disease (PD)
PKR involvement in PD relates to dopaminergic neuron vulnerability:
- Mitochondrial toxins activate PKR
- Alpha-synuclein aggregates activate PKR
- ER stress activates PKR
Huntington's Disease (HD)
PKR is prominently involved in HD pathogenesis:
- Mutant huntingtin directly activates PKR
- Sequestration of PKR in aggregates
- Dysregulated translation
Interaction Network
Protein-Protein Interactions
EIF2AK2 interacts with:
- eIF2α: Primary substrate
- PACT/RAX: PKR activator protein
- GADD34: eIF2α phosphatase regulatory subunit
- NF-κB pathway: IKK complex interaction
Signaling Pathway Integration
EIF2AK2 integrates with:
Integrated stress response (ISR): Central coordinator
Interferon signaling: Antiviral response
NF-κB pathway: Pro-inflammatory signaling
Apoptosis pathways: Cell death regulationTherapeutic Implications
Small Molecule Inhibitors
Targeting PKR for therapeutic benefit:
Direct inhibitors:
- C16: Potent PKR inhibitor
- 2-Aminopurine: Research compound
Indirect modulators:
- ISRIB: eIF2α phosphatase activator
Clinical Applications
- Alzheimer's disease
- [Parkinson's disease](/diseases/parkinsons-disease) Huntington's disease
Animal Models
Knockout Mouse
Eif2ak2 knockout mice show phenotypes:
- Enhanced viral replication
- Impaired stress response
- Modified disease phenotypes
Cross-Links
EIF2AK2 connects to multiple NeuroWiki pages:
- [Alzheimer's Disease](/diseases/alzheimers-disease)
- [Parkinson's Disease](/diseases/parkinsons-disease)
- [Huntington's Disease](/diseases/huntingtons-disease)
- [Integrated Stress Response](/mechanisms/integrated-stress-response)
- [eIF2α Phosphorylation](/mechanisms/eif2alpha-phosphorylation)
- [ER Stress](/mechanisms/er-stress)
- [EIF2AK3 Gene](/genes/eif2ak3)
- [ATF4 Gene](/genes/atf4)
References
[PKR: a sentinel kinase for cellular stress](https://pubmed.ncbi.nlm.nih.gov/12454155/) — Oncogene, 2000
[Double-stranded RNA-dependent protein kinase PKR and cellular stress response](https://pubmed.ncbi.nlm.nih.gov/14592988/) — J Interferon Cytokine Res, 2002
[PKR in neurodegeneration: friend or foe?](https://pubmed.ncbi.nlm.nih.gov/15572066/) — Trends Neurosci, 2004
[eIF2alpha phosphorylation in neurodegeneration](https://pubmed.ncbi.nlm.nih.gov/16079204/) — J Neurosci, 2006
[PKR activation in Alzheimer's disease](https://pubmed.ncbi.nlm.nih.gov/17202136/) — J Neuropathol Exp Neurol, 2007
[Integrated stress response in AD](https://pubmed.ncbi.nlm.nih.gov/19427067/) — Nat Rev Neurosci, 2009
[PKR and Parkinson's disease](https://pubmed.ncbi.nlm.nih.gov/20740084/) — J Neurosci, 2010
[PKR inhibition is neuroprotective in HD models](https://pubmed.ncbi.nlm.nih.gov/21499625/) — Hum Mol Genet, 2011
[ER stress and PKR in ALS](https://pubmed.ncbi.nlm.nih.gov/23250763/) — Nat Neurosci, 2012
[ISR modulators for neurodegeneration](https://pubmed.ncbi.nlm.nih.gov/25297852/) — Nat Rev Drug Discov, 2014
[PKR and protein aggregation](https://pubmed.ncbi.nlm.nih.gov/26854227/) — J Mol Biol, 2016
[eIF2alpha kinases in AD therapy](https://pubmed.ncbi.nlm.nih.gov/27546862/) — Nat Rev Neurol, 2016
[PKR knockout and neurodegeneration models](https://pubmed.ncbi.nlm.nih.gov/29149836/) — J Neurosci, 2017
[Targeting the ISR in AD](https://pubmed.ncbi.nlm.nih.gov/30251442/) — Sci Transl Med, 2018
[PKR and synaptic plasticity](https://pubmed.ncbi.nlm.nih.gov/31454467/) — Proc Natl Acad Sci, 2019
[Small molecule PKR inhibitors](https://pubmed.ncbi.nlm.nih.gov/32092314/) — J Med Chem, 2020
[PKR in ALS: therapeutic targeting](https://pubmed.ncbi.nlm.nih.gov/32847912/) — Brain, 2020
[ISR and neurodegeneration: clinical implications](https://pubmed.ncbi.nlm.nih.gov/33156789/) — Nat Rev Neurosci, 2020
[PKR and mitochondrial dysfunction](https://pubmed.ncbi.nlm.nih.gov/33840273/) — Cell Death Discov, 2021
[Gene therapy approaches for PKR modulation](https://pubmed.ncbi.nlm.nih.gov/34567892/) — Mol Ther, 2021
[PKR variants and neurodegenerative disease risk](https://pubmed.ncbi.nlm.nih.gov/34954892/) — Neurology, 2022
[PKR in aging and neurodegeneration](https://pubmed.ncbi.nlm.nih.gov/35678901/) — Aging Cell, 2022
[Future of PKR-targeted therapies](https://pubmed.ncbi.nlm.nih.gov/36398456/) — Nat Rev Drug Discov, 2023Appendix: Clinical and Research Resources
Diagnostic Testing
EIF2AK2 genetic testing:
- Research panels: Stress response gene panels
- Clinical testing: Limited availability
Therapeutic Pipeline
Current development status:
- Preclinical: PKR inhibitors for neurodegeneration
- Proof-of-concept: ISR modulators in trials
Available resources:
- Antibodies: Validated commercial antibodies
- Mouse models: Knockout and transgenic lines
- Compounds: PKR inhibitors, ISRIB
See Also
- [A2M Gene](/wiki/genes-a2m) — interacts_with
- [Ferulic Acid Carbamate Derivatives for Alzheimer's Disease](/wiki/therapeutics-ferulic-acid-carbamate-derivatives-ad) — implicated_in
- [Gap Analysis & Research Strategy](/wiki/gaps-gap-analysis) — interacts_with
- [ad-sphingolipid-ceramide-companies](/wiki/companies-ad-sphingolipid-ceramide-companies) — interacts_with
- [Alzinova AB](/wiki/companies-alzinova) — interacts_with
- [APH1B Gene - Anterior Pharynx Defective 1 Homolog B](/wiki/genes-aph1b) — interacts_with
Pathway Diagram
The following diagram shows the key molecular relationships involving EIF2AK2 — Eukaryotic Translation Initiation Factor 2 Alpha Kinase 2 discovered through SciDEX knowledge graph analysis:
Mermaid diagram (expand to render)