Endoplasmic reticulum (ER) stress and activation of the unfolded protein response (UPR) are common pathological features across Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and other neurodegenerative disorders. The ER is responsible for protein folding, lipid synthesis, and calcium storage. When protein folding is impaired or calcium homeostasis is disrupted, the UPR is activated to restore ER homeostasis. However, chronic ER stress leads to apoptotic signaling and neuronal death 1. [1]
This integration page examines the mechanisms of ER stress in neurodegeneration, the signaling pathways involved in the UPR, and therapeutic strategies targeting ER homeostasis. [2]
The endoplasmic reticulum maintains a specialized environment for protein folding: [3]
The UPR is mediated by three ER transmembrane sensors: [4]
IRE1 (inositol-requiring enzyme 1) [5]
PERK (PKR-like ER kinase) [6]
ATF6 (activating transcription factor 6) [7]
ER stress is an early event in AD pathogenesis: [8]
Aβ and ER stress: Aβ directly induces ER stress in neurons and glia. The amyloid precursor protein (APP) and its processing enzymes reside in the ER-Golgi compartments.
Presenilin mutations: PSEN1 and PSEN2 mutations affect ER calcium homeostasis and induce chronic ER stress. iPSC models show that neurons with PSEN1 mutations have baseline ER stress.
Tau pathology: Hyperphosphorylated tau impairs ER-Golgi trafficking, contributing to ER stress.
Synaptic vulnerability: ER stress preferentially affects synaptic function before causing cell death.
Key markers elevated in AD:
See Protein Aggregation Comparison for detailed information.
ER stress is a prominent feature in PD pathogenesis:
α-Synuclein and ER stress: Mutant and wild-type α-synuclein accumulate in the ER, causing ER stress. Oligomeric α-synuclein is particularly toxic to the ER.
Environmental toxins: MPTP, 6-OHDA, and rotenone induce ER stress in dopaminergic neurons.
Calcium dysregulation: ER-calcium depletion triggers ER stress pathways.
PD gene interactions: LRRK2 mutations and GBA1 deficiency exacerbate ER stress.
Key markers in PD:
Key genes in PD ER stress:
ER stress is a major contributor to motor neuron degeneration:
Mutant SOD1: Accumulates in the ER, causing ER stress. Mutant SOD1 directly interacts with ER chaperones.
TDP-43 pathology: TDP-43 mislocalization to the cytoplasm disrupts ER homeostasis.
C9orf72: Dipeptide repeat proteins from hexanucleotide repeat expansion cause ER stress.
ER Calcium dysregulation: Impaired calcium handling contributes to ER stress.
Key markers in ALS:
See TDP-43 Proteinopathy for detailed information.
Key genes in ALS ER stress:
The ER is a major calcium storage organelle. Disruption of ER calcium homeostasis triggers ER stress:
ER stress and oxidative stress form a vicious cycle:
See Oxidative Stress in Neurodegeneration for detailed information.
Accumulated misfolded proteins in the ER trigger UPR:
See Protein Aggregation Comparison for detailed information.
Chemical chaperones:
Chaperone inducers:
IRE1 modulators:
PERK modulators:
ATF6 modulators:
SERCA activators:
See Oxidative Stress in Neurodegeneration for detailed information.
Hetz & Mollereau, ER Stress in Neurodegeneration (2014). 2014. ↩︎
Duran-Aniotz et al. ER Stress in AD (2019). 2019. ↩︎
Belbin et al. ER Stress in PD (2018). 2018. ↩︎
Shi et al. ER Stress in ALS (2018). 2018. ↩︎
Kim et al. UPR Signaling in Neurodegeneration (2018). 2018. ↩︎
MERCkx et al. Calcium and ER Stress (2019). 2019. ↩︎