EIF2α Protein

Overview

Eukaryotic translation initiation factor 2 subunit alpha (EIF2α) is the regulatory subunit of the eIF2 heterotrimeric GTPase complex, which controls the rate-limiting step of protein synthesis initiation. Phosphorylation of EIF2α at Ser51 serves as the central hub for the integrated stress response (ISR), coordinating translational attenuation in response to diverse cellular stresses including ER stress, amino acid deprivation, viral infection, and oxidative damage^{1https://doi.org/10.1101/cshperspect.a0328612018 · DOI 10.1101/cshperspect.a032861](https://doi.org/10.1101/cshperspect.a032861Open reference}.

In neurodegenerative diseases, aberrant EIF2α phosphorylation contributes to synaptic dysfunction, memory impairment, and neuronal death. The EIF2α pathway represents a major therapeutic target for Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, ALS, and prion disorders^{2https://doi.org/10.1016/j.brainres.2020.1469072020 · DOI 10.1016/j.brainres.2020.146907](https://doi.org/10.1016/j.brainres.2020.146907Open reference}.

Structure and Domains

EIF2α contains:

• N-terminal domain (1-185): Contains the critical Ser51 phosphorylation site within a flexible loop; interacts with GTP-binding subunit

• Central β-barrel domain (186-280): Provides structural scaffold

• C-terminal OB-fold domain (281-315): Mediates interactions with eIF2β and eIF2γ subunits

The eIF2 complex delivers initiator methionyl-tRNA (Met-tRNAi) to the 40S ribosomal subunit in a GTP-dependent manner. GTP hydrolysis and GDP release are required for each translation initiation cycle^{3https://doi.org/10.1146/annurev-biochem-060713-0358022014 · DOI 10.1146/annurev-biochem-060713-035802](https://doi.org/10.1146/annurev-biochem-060713-035802Open reference}.

Normal Function

Translation Initiation

eIF2•GTP•Met-tRNAi ternary complex formation is essential for every round of translation initiation. The complex:

1. Binds the 40S ribosomal subunit

2. Scans mRNA 5’ UTRs for start codons

3. Enables AUG start codon recognition

4. GTP hydrolysis releases eIF2-GDP for recycling

Integrated Stress Response (ISR)

Four kinases phosphorylate EIF2α at Ser51 in response to distinct stressors^{4https://doi.org/10.1007/s00018-012-1252-62013 · DOI 10.1007/s00018-012-1252-6](https://doi.org/10.1007/s00018-012-1252-6Open reference}:

Phosphorylated EIF2α (p-EIF2α) inhibits eIF2B, the GTP exchange factor, reducing ternary complex availability and global protein synthesis by 50-90%^{5https://doi.org/10.15252/embr.2016421952016 · DOI 10.15252/embr.201642195](https://doi.org/10.15252/embr.201642195Open reference}.

Selective Translation

Paradoxically, p-EIF2α enhances translation of specific mRNAs with upstream open reading frames (uORFs), including:

• ATF4: Transcription factor activating stress response genes

• CHOP (DDIT3): Pro-apoptotic transcription factor

• GADD34: PPP1R15A, feedback phosphatase regulatory subunit

Role in Neurodegeneration

Alzheimer’s Disease

In AD brains, elevated p-EIF2α and ATF4 levels correlate with disease progression^{6https://doi.org/10.1016/j.bbrc.2006.12.1692007 · DOI 10.1016/j.bbrc.2006.12.169](https://doi.org/10.1016/j.bbrc.2006.12.169Open reference}:

• PERK activation: Accumulation of misfolded Aβ and tau activates the UPR

• Synaptic plasticity: p-EIF2α impairs long-term potentiation (LTP) and memory consolidation

• BACE1 translation: Paradoxically, p-EIF2α increases BACE1 via uORF bypass, enhancing Aβ production

• Neuronal death: Sustained CHOP expression promotes apoptosis

eIF2α phosphorylation is elevated in hippocampal neurons of AD patients and APP/PS1 transgenic mice^{7https://doi.org/10.1016/j.neurobiolaging.2006.08.0122008 · DOI 10.1016/j.neurobiolaging.2006.08.012](https://doi.org/10.1016/j.neurobiolaging.2006.08.012Open reference}.

Parkinson’s Disease

• α-synuclein aggregates activate PERK in dopaminergic neurons

• PINK1/Parkin dysfunction impairs mitochondrial protein quality control, triggering ER stress

• Dopaminergic vulnerability: Substantia nigra neurons show elevated p-PERK and p-EIF2α

Post-mortem PD brains show increased p-PERK and p-EIF2α in surviving dopaminergic neurons^{8https://doi.org/10.1016/S0002-9440(10)62314-02005 · DOI 10.1016/S0002-9440(10Open reference}.

Huntington’s Disease

• PolyQ-expanded huntingtin disrupts ER homeostasis

• Chronic UPR activation contributes to striatal neuron degeneration

• BDNF translation: p-EIF2α impairs dendritic BDNF synthesis, affecting synaptic plasticity

ALS and FTD

• TDP-43 cytoplasmic aggregates activate the ISR

• C9orf72 dipeptide repeats induce ER stress

• SOD1 mutations trigger PERK activation in motor neurons

• FUS pathology associated with PERK-p-EIF2α signaling

Prion Diseases

• PrP^Sc accumulation activates PERK and PKR

• Sustained p-EIF2α critical for prion neurotoxicity

• ISRIB rescues prion-induced synaptic deficits in models

Therapeutic Targeting

ISRIB (Integrated Stress Response Inhibitor)

ISRIB stabilizes eIF2B, restoring translation despite p-EIF2α^{9https://doi.org/10.7554/eLife.004982013 · DOI 10.7554/eLife.00498](https://doi.org/10.7554/eLife.00498Open reference}:

• Mechanism: Binds eIF2B, counteracts p-EIF2α-mediated inhibition

• Preclinical: Improves memory, protects neurons in AD/PD/HD models

• Clinical: Not yet in human trials for neurodegeneration

PERK Inhibitors

• GSK2606414: Potent PERK inhibitor, neuroprotective in prion and tau models

• GSK2656157: Improved brain penetration

• Limitations: Pancreatic toxicity due to essential PERK function in secretory cells

GCN2 Inhibitors

• A-92: Selective GCN2 inhibitor

• Potential: May reduce ISR in specific contexts

Salubrinal

• Mechanism: Inhibits GADD34/PP1 phosphatase, sustaining p-EIF2α

• Paradox: Protective in some models, harmful in others

• Interpretation: Context-dependent; acute vs chronic activation

Key Interactions

See Also

• Unfolded Protein Response

External Links

• UniProt: P05198

• PDB structures