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Updated: Mar 22, 2026

Assays for the Degradation of Misfolded Proteins in Cells
Published on: August 28, 2016
Expanded polyglutamine embedded in the endoplasmic reticulum causes membrane distortion and coincides with Bax
Masashi Ueda1, Shimo Li1, Masanori Itoh1
1Department of Neurobiology, Gifu University Graduate School of Medicine, 1-1 Yanagido, Gifu 501-1194, Japan.
Polyglutamine causes endoplasmic reticulum (ER) membrane distortion, impacting cellular functions and potentially leading to neuronal cell death. This study reveals the ER membrane as a target, triggering cell death via Bax.
Area of Science:
- Cell Biology
- Neuroscience
- Molecular Biology
Background:
- The endoplasmic reticulum (ER) is vital for protein synthesis, lipid metabolism, and calcium homeostasis.
- ER stress and membrane distortion are implicated in neurodegenerative diseases like Huntington's disease.
- Polyglutamine's role in nuclear envelope distortion and neuronal cell death is known, but the underlying mechanism is unclear.
Purpose of the Study:
- To elucidate the mechanism by which polyglutamine induces ER membrane distortion.
- To investigate the localization and effects of polyglutamine within cellular membranes.
- To identify the cellular targets and pathways involved in polyglutamine-induced cell death.
Main Methods:
- Electron microscopy to visualize cellular structures.
- Fluorescence protease protection assay to determine protein localization.
- Alkaline treatment to analyze membrane interactions.
Main Results:
- Polyglutamine was found embedded within the ER membrane.
- ER membrane morphology was altered, showing luminal dilation and elongated ER-mitochondria contacts.
- Nuclear envelope distortion was observed concurrently with polyglutamine embedding in the ER membrane.
- Polyglutamine embedding in the ER membrane coincided with Bax insertion.
Conclusions:
- The ER membrane is a direct target of polyglutamine.
- Polyglutamine-induced ER membrane distortion contributes to cellular dysfunction.
- Polyglutamine triggers cell death pathways, involving Bax, through ER membrane targeting.
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