PERK Protein
<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">PERK Protein</th>
</tr>
<tr>
<td class="label">Interactor</td>
<td>Relationship</td>
</tr>
<tr>
<td class="label">BiP/GRP78</td>
<td>Inhibitory binding partner</td>
</tr>
<tr>
<td class="label">[eIF2α](/proteins/eif2a)</td>
<td>Phosphorylation substrate</td>
</tr>
<tr>
<td class="label">ATF4</td>
<td>Downstream transcription factor</td>
</tr>
<tr>
<td class="label">CHOP</td>
<td>ATF4 target</td>
</tr>
<tr>
<td class="label">GADD34</td>
<td>Phosphatase regulator</td>
</tr>
<tr>
<td class="label">Nrf2</td>
<td>PERK phosphorylates</td>
</tr>
<tr>
<td class="label">FoxO1</td>
<td>PERK phosphorylates</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/ad" style="color:#ef9a9a">AD</a>, <a href="/wiki/ali" style="color:#ef9a9a">ALI</a>, <a href="/wiki/als" style="color:#ef9a9a">ALS</a>, <a href="/wiki/aging" style="color:#ef9a9a">Aging</a>, <a href="/wiki/als" style="color:#ef9a9a">Als</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">390 edges</a></td>
</tr>
</table>
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<strong>PERK</strong><br>
<i>Protein Kinase R-like ER Kinase</i>
<hr>
<strong>Symbol:</strong> EIF2AK3 / PEK<br>
<strong>UniProt:</strong> [Q9NZJ5](https://www.uniprot.org/uniprot/Q9NZJ5)<br>
<strong>Gene:</strong> [EIF2AK3](/entities/eif2ak3)<br>
<strong>Molecular Weight:</strong> 125 kDa<br>
<strong>Location:</strong> ER membrane (Type I transmembrane)<br>
<strong>PDB:</strong> [3QD2](https://www.rcsb.org/structure/3QD2), [5YVA](https://www.rcsb.org/structure/5YVA)
</div>
Overview
Protein kinase R-like endoplasmic reticulum kinase (PERK, also known as EIF2AK3 or PEK) is a type I transmembrane protein kinase localized to the ER membrane. As one of the three major sensors of the [unfolded protein response (UPR)](/mechanisms/er-stress-upr), PERK couples ER stress to translational attenuation through phosphorylation of [eIF2α](/proteins/eif2a) at Ser51[@harding2000].
PERK activation represents a critical adaptive mechanism during protein misfolding stress, but chronic PERK signaling contributes to neurodegeneration in Alzheimer's disease, Parkinson's disease, ALS, Huntington's disease, and prion disorders[@mercado2020].
Structure and Domains
PERK contains:
- N-terminal luminal domain (1-576): Senses misfolded proteins in the ER lumen; interacts with BiP/GRP78
- Transmembrane domain (577-597): Anchors PERK to ER membrane
- Cytosolic kinase domain (666-1114): Serine/threonine kinase activity; phosphorylates eIF2α
Activation mechanism: Under normal conditions, BiP binds the luminal domain, maintaining PERK monomeric and inactive. ER stress causes BiP release, allowing PERK dimerization, trans-autophosphorylation, and activation[@carrara2015].
Normal Function
Unfolded Protein Response
PERK is one of three ER stress sensors (along with [IRE1](/proteins/ire1) and ATF6):
Stress sensing: Accumulation of unfolded proteins in the ER lumen
BiP release: Competition between misfolded proteins and PERK for BiP binding
Dimerization: Luminal domains interact, bringing kinase domains together
Autophosphorylation: Trans-phosphorylation at activation loop residues
eIF2α phosphorylation: Converts eIF2α to a potent inhibitor of eIF2BIntegrated Stress Response
PERK is one of four eIF2α kinases (with GCN2, PKR, HRI), integrating diverse stress signals into a common translational response[@wek2006]:
- Global translation inhibition: Reduces protein load on stressed ER
- Selective ATF4 translation: Activates stress-adaptive gene expression
- Redox homeostasis: ATF4 induces antioxidant genes
- Amino acid metabolism: Upregulates amino acid transporters and biosynthesis
Physiological Roles
- Pancreatic β-cells: Essential for high secretory demand
- Plasma cells: Supports antibody production
- Osteoblasts: Bone matrix secretion
- Development: PERK mutations cause Wolcott-Rallison syndrome
Role in Neurodegeneration
Alzheimer's Disease
In AD, PERK activation occurs early and intensifies with disease progression[@hoozemans2005]:
- [Aβ](/proteins/amyloid-beta) oligomers: Activate PERK in cultured [neurons](/entities/neurons)
- [Tau](/proteins/tau) aggregates: Trigger ER stress and PERK activation
- Hippocampal neurons: Elevated p-PERK and p-eIF2α in AD brains
- [BACE1](/entities/bace1) paradox: PERK signaling increases BACE1 translation via uORF bypass, accelerating Aβ production
- Synaptic dysfunction: Impaired [LTP](/mechanisms/long-term-potentiation) and memory consolidation
Evidence: Post-mortem AD brains show p-PERK immunoreactivity in neurons with neurofibrillary tangles[@hoozemans2007].
Parkinson's Disease
- [α-synuclein](/proteins/alpha-synuclein): Overexpression or aggregation activates PERK
- Dopaminergic vulnerability: Substantia nigra neurons show elevated p-PERK
- MPTP models: PERK activation in nigrostriatal pathway
- LRRK2: Pathogenic variants may enhance ER stress susceptibility
Clinical correlation: p-PERK levels correlate with Lewy body density in PD patients[@baek2022].
Huntington's Disease
- PolyQ-expanded [huntingtin](/proteins/huntingtin): Disrupts ER calcium homeostasis
- [UPR](/entities/unfolded-protein-response) activation: Chronic PERK signaling in striatal neurons
- R6/2 and HD-N171-82Q models: Elevated p-PERK and p-eIF2α
- Synaptic defects: Impaired dendritic protein synthesis
ALS and FTD
- SOD1 mutations: Mutant SOD1 activates PERK in motor neurons
- [TDP-43](/mechanisms/tdp-43-proteinopathy): Cytoplasmic aggregates trigger ER stress
- [C9orf72](/entities/c9orf72): Dipeptide repeat proteins activate PERK
- FUS: Mutant FUS induces UPR activation
Prion Diseases
- PrP^Sc accumulation: Activates all three UPR branches
- PERK dependency: Genetic PERK reduction delays prion disease
- Therapeutic window: PERK inhibition after symptom onset still effective in mice
Therapeutic Targeting
PERK Inhibitors
GSK2606414:
- Potent and selective PERK inhibitor (IC50 = 0.4 nM)
- Neuroprotective in prion disease models
- Extended survival in tauopathy mice
- Limitation: Pancreatic toxicity from β-cell dysfunction
GSK2656157:
- Improved brain penetration
- Reduced pancreatic toxicity at neuroprotective doses
- Protective in 5xFAD Alzheimer's model[@gsk2021]
AMG44:
- Next-generation PERK inhibitor
- Improved therapeutic window
ISRIB
Rather than inhibiting PERK directly, ISRIB stabilizes eIF2B to counteract p-eIF2α-mediated translational inhibition[@sidrauski2015]:
- Downstream of PERK
- Restores translation without affecting PERK signaling
- Neuroprotective in multiple neurodegeneration models
- Cognitive enhancement in healthy animals
Gene Therapy Approaches
- PERK heterozygosity: Reduces neurodegeneration in mouse models
- Conditional knockout: Temporal control to avoid developmental effects
- RNA interference: Reduce PERK expression in vulnerable neurons
Key Interactions
See Also
- [unfolded protein response (UPR)](/mechanisms/er-stress-upr)
External Links
- [UniProt: Q9NZJ5](https://www.uniprot.org/uniprot/Q9NZJ5)
- [PDB structures](https://www.rcsb.org/search?q=uniprot:Q9NZJ5)
References
[Harding HP et al. Regulated translation initiation controls stress-induced gene expression in mammalian cells. Mol Cell. 2000;6(5):1099-1108, https://doi.org/10.1016/S1097-2765(00)00108-8 (2000)](https://doi.org/10.1016/S1097-2765(00)
[Mercado G et al. ER stress and neurodegeneration: Pathogenic mechanisms and therapeutic opportunities. Curr Top Med Chem. 2020;20(18):1621-1652, https://doi.org/10.2174/1568026620666200416092946 (2020)](https://doi.org/10.2174/1568026620666200416092946](https://doi.org/10.2174/1568026620666200416092946](https://doi.org/10.2174/1568026620666200416092946)
[Carrara G et al. Characterization of the unfolded protein response in mammalian cells. Methods Mol Biol. 2015;1292:37-49, https://doi.org/10.1007/978-1-4939-2522-3_4 (2015)](https://doi.org/10.1007/978-1-4939-2522-3_4](https://doi.org/10.1007/978-1-4939-2522-3_4](https://doi.org/10.1007/978-1-4939-2522-3_4)
[Wek RC et al. Coping with stress: eIF2 kinases and translational control. Biochem Soc Trans. 2006;34(Pt 1):7-11, https://doi.org/10.1042/BST20060007 (2006)](https://doi.org/10.1042/BST20060007](https://doi.org/10.1042/BST20060007](https://doi.org/10.1042/BST20060007)
[Hoozemans JJM et al. The unfolded protein response is activated in Alzheimer's disease. Acta Neuropathol. 2005;110(2):165-172, https://doi.org/10.1007/s00401-005-1038-0 (2005)](https://doi.org/10.1007/s00401-005-1038-0](https://doi.org/10.1007/s00401-005-1038-0](https://doi.org/10.1007/s00401-005-1038-0)
[Hoozemans JJM et al. Activation of the unfolded protein response in Parkinson's disease. Biochem Biophys Res Commun. 2007;354(3):707-711, https://doi.org/10.1016/j.bbrc.2006.12.169 (2007)](https://doi.org/10.1016/j.bbrc.2006.12.169](https://doi.org/10.1016/j.bbrc.2006.12.169](https://doi.org/10.1016/j.bbrc.2006.12.169)
[Baek JH et al. The PERK signaling pathway in Alzheimer's and Parkinson's disease. Front Neurosci. 2022;16:984844, https://doi.org/10.3389/fnins.2022.984844 (2022)](https://doi.org/10.3389/fnins.2022.984844](https://doi.org/10.3389/fnins.2022.984844](https://doi.org/10.3389/fnins.2022.984844)
[GSK2656157 clinical development, https://doi.org/10.1016/j.ymthe.2021.05.014 (2021)](https://doi.org/10.1016/j.ymthe.2021.05.014](https://doi.org/10.1016/j.ymthe.2021.05.014](https://doi.org/10.1016/j.ymthe.2021.05.014)
[Sidrauski C et al. Pharmacological dimerization and blockade of the integrated stress response. Cell. 2015;162(2):446-460, https://doi.org/10.1016/j.cell.2015.06.044 (2015)](https://doi.org/10.1016/j.cell.2015.06.044](https://doi.org/10.1016/j.cell.2015.06.044](https://doi.org/10.1016/j.cell.2015.06.044)Pathway Diagram
Mermaid diagram (expand to render)
Pathway Diagram
The following diagram shows the key molecular relationships involving PERK Protein discovered through SciDEX knowledge graph analysis:
Mermaid diagram (expand to render)