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Control of PERK eIF2alpha kinase activity by the endoplasmic reticulum stress-induced molecular chaperone P58IPK
Wei Yan1, Christopher L Frank, Marcus J Korth
1Departments of Microbiology and Laboratory Medicine, School of Medicine, and Washington National Primate Research Center, University of Washington, Seattle, WA 98195, USA. wyan96@u.washington.edu
Abstract:
P58(IPK) is an Hsp40 family member known to inhibit the interferon (IFN)-induced, double-stranded RNA-activated, eukaryotic initiation factor 2alpha (eIF2alpha) protein kinase R (PKR) by binding to its kinase domain. We find that the stress of unfolded proteins in the endoplasmic reticulum (ER) activates P58(IPK) gene transcription through an ER stress-response element in its promoter region. P58(IPK) interacts with and inhibits the PKR-like ER-localized eIF2alpha kinase PERK, which is normally activated during the ER-stress response to protect cells from ER stress by attenuating protein synthesis and reducing ER client protein load. Levels of phosphorylated eIF2alpha were lower in ER-stressed P58(IPK)-overexpressing cells and were enhanced in P58(IPK) mutant cells. In the ER-stress response, PKR-like ER kinase (PERK)-mediated translational repression is transient and is followed by translational recovery and enhanced expression of genes that increase the capacity of the ER to process client proteins. The absence of P58(IPK) resulted in increased expression levels of two ER stress-inducible genes, BiP and Chop, consistent with the enhanced eIF2alpha phosphorylation in the P58(IPK) deletion cells. Our studies suggest that P58(IPK) induction during the ER-stress response represses PERK activity and plays a functional role in the expression of downstream markers of PERK activity in the later phase of the ER-stress response.
Insights
Endoplasmic reticulum (ER) stress activates P58(IPK) to inhibit PERK, a key kinase. This regulation impacts protein synthesis and ER stress response markers like BiP and Chop.
Area of Science:
- Cellular Biology
- Molecular Biology
- Stress Response
Background:
- P58(IPK) is an Hsp40 protein that inhibits the interferon-induced kinase PKR.
- Endoplasmic reticulum (ER) stress, caused by unfolded proteins, triggers cellular defense mechanisms.
Purpose of the Study:
- To investigate the role of P58(IPK) in the ER stress response.
- To determine how P58(IPK) interacts with and affects the PKR-like ER-localized eIF2alpha kinase (PERK).
Main Methods:
- Analysis of P58(IPK) gene transcription activation by ER stress.
- Investigating the interaction between P58(IPK) and PERK.
- Measuring levels of phosphorylated eukaryotic initiation factor 2alpha (eIF2alpha).
- Assessing the expression of ER stress-inducible genes (BiP and Chop) in P58(IPK) manipulated cells.
Main Results:
- ER stress induces P58(IPK) gene transcription.
- P58(IPK) interacts with and inhibits PERK activity.
- Reduced phosphorylated eIF2alpha in cells overexpressing P58(IPK), and enhanced phosphorylation in P58(IPK) mutant cells.
- Absence of P58(IPK) led to increased expression of ER stress markers BiP and Chop.
Conclusions:
- P58(IPK) is induced by ER stress and functions to repress PERK activity.
- P58(IPK) plays a role in the later phase of the ER stress response, influencing downstream PERK activity markers.