perk-protein

perk-protein
Symbol	PERK
Full Name	perk-protein
Type	Protein
UniProt	Search UniProt
Associated Diseases	AD, ALI, ALS, Aging, Als
KG Connections	390 edges

Introduction

Perk (Protein Kinase R Like Er Kinase) is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

Overview

PERK (Protein Kinase R-like ER Kinase, also known as EIF2AK3) is a key sensor of endoplasmic reticulum (ER) stress and a critical regulator of the unfolded protein response) (UPR). PERK is a type I transmembrane protein localized to the ER membrane that activates the Integrated Stress Response (ISR) when misfolded proteins accumulate in the ER lumen (Hetz & Glimour, 2009; Wang & Kaufman, 2016). PERK activation has been implicated in Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis, and Huntington’s disease, making it an important therapeutic target (Kim et al., 2020; Liu et al., 2019). ^{1Citation2016 · DOI 10.1038/nrm.2016.81Open reference}

--- ^{2Citation2020 · DOI 10.1016/j.tcb.2020.02.006Open reference}

Gene and Protein Structure

EIF2AK3 Gene

The EIF2AK3 gene (ENSG00000168207) is located on chromosome 2p22.2 and consists of 18 exons. It encodes the PERK protein, a large type I transmembrane kinase. ^{3Citation2019 · DOI 10.1016/j.tips.2019.08.003Open reference}

Protein Domain Architecture

PERK is a 1254-amino acid protein with the following structural features: ^{4Citation2000 · DOI 10.1038/35021049Open reference}

• Luminal stress-sensing domain (residues 1-568): Binds unfolded proteins through its interaction with the chaperone BiP (GRP78)

• Transmembrane helix (residues 569-591): Anchors PERK to the ER membrane

• Cytoplasmic serine/threonine kinase domain (residues 592-1254): Contains the active site and undergoes autophosphorylation upon activation

• eIF2α phosphorylation site: PERK phosphorylates eIF2α at Ser^51 to attenuate global translation

Activation Mechanism

Under normal conditions, PERK’s luminal domain is bound by BiP (GRP78), which prevents dimerization and kinase activation. During ER stress, BiP dissociates to bind misfolded proteins, allowing PERK to dimerize and autophosphorylate (Bertolotti et al., 2000; Kimata et al., 2008). ^{5Citation2008 · DOI 10.1016/j.tcb.2008.01.003Open reference}

--- ^{6Citation2012 · DOI 10.1016/j.neurobiolaging.2011.09.030Open reference}

Normal Biological Functions

Integrated Stress Response (ISR)

PERK is one of four eIF2α kinases that activate the Integrated Stress Response (ISR). The ISR coordinates cellular adaptation to various stressors: ^{7Citation2019 · DOI 10.1074/jbc.REV119.007790Open reference}

• PERK: Activated by ER stress (misfolded proteins, calcium depletion, hypoxia)

• GCN2: Activated by amino acid deprivation

• PKR: Activated by viral infection

• HRI: Activated by heme deficiency

Translational Control

PERK-mediated eIF2α phosphorylation causes: ^{8Citation2011 · DOI 10.1016/j.neurobiolaging.2010.12.016Open reference}

• Global translation attenuation: Reduces protein load on the stressed ER

• Selective translation of stress-response proteins: ATF4, CHOP, GADD34, XBP1

Apoptosis Regulation

Prolonged PERK activation leads to apoptosis through:

• CHOP upregulation: Pro-apoptotic transcription factor

• Bcl-2 family modulation: Decreased anti-apoptotic proteins

• Calcium homeostasis disruption: Mitochondrial apoptosis pathway

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Role in Neurodegenerative Diseases

Alzheimer’s Disease

PERK activation is a hallmark of AD brain pathology:

ER Stress:

• Amyloid-beta (Aβ) oligomers induce PERK activation in neurons (Costa et al., 2012)

• PERK is hyperactivated in AD hippocampus and frontal cortex

• PERK activation correlates with tau pathology

Translational Dysregulation:

• Global translation is impaired in AD brain

• PERK-mediated eIF2α phosphorylation contributes to synaptic protein loss

• Restoring translation with ISR inhibitors improves synaptic function in AD models

Synaptic Dysfunction:

• PERK activation contributes to synaptic loss in AD

• Inhibiting PERK protects against Aβ-induced synaptic damage

Parkinson’s Disease

PERK plays complex roles in PD:

ER Stress:

• Alpha-synuclein aggregation triggers PERK activation in dopaminergic neurons (Colla et al., 2019)

• PERK activation is elevated in substantia nigra of PD patients

Dopaminergic Neuron Vulnerability:

• PERK-mediated translational attenuation impairs protein homeostasis

• Chronic PERK activation leads to apoptosis of dopaminergic neurons

Therapeutic Potential:

• PERK inhibition protects against α-syn-induced toxicity (Bellucci et al., 2011)

• However, complete PERK loss may be detrimental due to loss of adaptive UPR

Amyotrophic Lateral Sclerosis (ALS)

• PERK is activated in ALS motor neurons and glia

• Mutations in SOD1, FUS, and C9orf72 all induce ER stress and PERK activation

• PERK activation contributes to motor neuron death in ALS models

• However, PERK also attempts adaptive responses, complicating therapeutic targeting

Huntington’s Disease

• Mutant huntingtin protein induces ER stress

• PERK activation is increased in HD models and patient tissue

• PERK-mediated translational repression contributes to neuronal dysfunction

• ISR modulators show promise in HD preclinical models

Ischemia and Stroke

• PERK is rapidly activated following cerebral ischemia

• Contributes to both adaptive responses and excitotoxic cell death

• PERK inhibition may reduce post-ischemic brain damage

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Therapeutic Strategies

PERK Inhibitors

Small molecule PERK inhibitors are under development:

• GSK2656157: First-generation PERK inhibitor, showed efficacy in cancer models but limited BBB penetration

• AMG 47: More brain-penetrant PERK inhibitor

• Compound 43: Selective PERK inhibitor with improved CNS penetration

Challenges

• PERK has both protective and harmful effects depending on context and duration

• Complete PERK inhibition may impair adaptive UPR

• Timing of intervention is critical (early vs. late disease)

• Selectivity over other eIF2α kinases is important

ISR Modulators

Rather than direct PERK inhibition, alternative approaches include:

• ISRIB (Integrated Stress Response Inhibitor): Stabilizes eIF2B to bypass eIF2α phosphorylation effects

• eIF2α phosphatase inhibitors: Maintain translational recovery

• Modulators of upstream ER stress: Target misfolded protein handling

Combination Approaches

• PERK inhibition combined with other ER stress modulators

• Targeting downstream effectors (CHOP, ATF4)

• Combined modulation of UPR branches (PERK, IRE1, ATF6)

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See Also

• Proteins Index

• Genes Index

  • EIF2AK3 Gene

• Diseases Index

  • Alzheimer’s Disease

  • Parkinson’s Disease

  • Amyotrophic Lateral Sclerosis

  • Huntington’s Disease

• Mechanisms Index

  • ER Stressmechanisms/er-stress-neurodegeneration)

  • Unfolded Protein Responsemechanisms/er-stress-unfolded-protein-response)

  • Integrated Stress Response

  • Apoptosis

• Treatments Index

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External Links

External Links

• EIF2AK3 Gene (NCBI)

• PERK Protein (UniProt)

• PERK Structure (PDB)

• PERK in Neurodegeneration (PubMed)

• ER Stress and UPR (Reviews)

Background

The study of Perk (Protein Kinase R Like Er Kinase) has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.

Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.