Chronic stress antagonizes formation of Stress Granules

Yuichiro Adachi, Allison M. Williams, Masashi Masuda, Yutaka Taketani, Paul J. Anderson, Pavel Ivanov

Posted on: 8 April 2025 , updated on: 9 April 2025

Preprint posted on 3 November 2024

Stalling the stress response: chronic low-level stress inhibits stress granule formation via translation elongation impairment

Selected by Mohammed JALLOH

Categories: biochemistry, cell biology, molecular biology

Why I chose this preprint: As an RNA biologist studying stress granules, I chose to highlight this preprint by Adachi and colleagues because it provides important mechanistic insight into how chronic stress disrupts stress granule formation through eEF2 phosphorylation and ribosome stalling, offering a fresh perspective on translation dynamics and stress responses that could reshape our understanding of stress granules.

Background: Under acute stress, cells halt global translation, triggering rapid disassembly of polysomes and the assembly of stress granules (SGs)—membrane-less ribonucleoprotein (RNP) condensates enriched in untranslated mRNAs, 40S ribosomal subunits, and key RNA-binding proteins (RBPs) such as G3BP1, eIF3b, and eIF4G^1-2. This sequestration is thought to protect mRNAs from degradation and modulate cell survival pathways. Traditionally, SG formation is tightly linked to eIF2α phosphorylation that suppresses translation initiation³. However, less is known about how cells respond when the stress is chronic rather than acute.

Study overview: In this preprint, Adachi and colleagues investigated how chronic stress, as opposed to acute stress, modulates cellular translation and the formation of stress granules (SGs).

Chronic Stress Pre-conditioning Prevents Stress Granule Assembly During Acute Stress.

To determine whether cells pre-conditioned with various low-dose chronic stresses fail to form SGs upon acute stress, the authors pre-conditioned cells with chronic low doses of several stress inducers (e.g., 10 µM sodium arsenite, thapsigargin, CCCP, starvation media) for 24 hours. Acute stress was then applied using higher doses of sodium arsenite (e.g., 100 µM or 500 µM) to induce SG assembly. The authors used IF microscopy to visualize canonical SG-markers for SG formation. Quantification of SG-positive cells across different time points and stress doses indicated that low-dose SA (10 μM) over 24 hours did not induce SGs, while higher doses (e.g., 500 μM) did, indicating a threshold effect (see preprint Fig1A). Cells pre-treated with low-dose SA (or other stressors) exhibited a dramatic reduction in SG formation upon acute SA exposure indicating that chronic stress pre-conditioning renders cells incompetent to assemble SGs despite the presence of acute stress signals (see preprint Fig.1B-D).

Translation Dynamics Implicated in Stress Granule Inhibition.

The dynamics of SGs are closely tied to the regulation of translation, particularly during translation initiation and elongation. To investigate how translation is affected by chronic stress conditions, the authors examined the roles of translation initiation (via eIF2α phosphorylation) and elongation (via eEF2 phosphorylation) using polysome profiling. This technique allowed them to assess the state of mRNA translation in cells with or without chronic stress pre-conditioning. They found that in control cells, acute SA treatment rapidly disassembled polysomes. However, in cells pre-conditioned with chronic stress, polysomes remained partially intact. Western blot analysis confirmed that eIF2α phosphorylation, which indicates inhibition of translation initiation, occurred similarly in both conditions. The incomplete disassembly of polysomes in chronically stressed cells was associated with a failure to form SGs. This suggests that the persistence of 80S ribosomes on mRNAs under chronic stress conditions prevents the nucleation of SGs.

Translation Elongation Slowdown Prevents Stress Granule Formation.

As a final stroke, the researchers decided to use multiple stress inducers and translation inhibitors such as puromycin (which induces premature termination and ribosome splitting) and harringtonine (which blocks the initial elongation step). This approach was employed to distinguish between translation initiation inhibition and elongation slowing. In control cells, puromycin induced SG formation along with complete polysome disassembly; however, in pre-conditioned cells, puromycin failed to disassemble polysomes and did not trigger SG assembly. This further supports that chronic stress “freezes” ribosomes on mRNAs, obstructing the pathway required for SG formation. Chronic stress pre-conditioning significantly delayed polysome disassembly after harringtonine treatment. Elevated levels of phosphorylated eEF2 were detected in chronically stressed cells, correlating with the failure of SG assembly. These results indicate that chronic stress causes a slowdown in translation elongation by inducing eEF2 phosphorylation, leading to ribosome stalling that prevents proper disassembly of polysomes.

Together, the authors propose a model arguing that acute stress normally induces eIF2α phosphorylation, rapid ribosome splitting, and SG assembly. In contrast, chronic stress causes eEF2 phosphorylation and ribosome stalling, which maintains polysomes in a “frozen” state and precludes SG formation even during subsequent acute stress.

Kedersha, N. L., Gupta, M., Li, W., Miller, I. & Anderson, P. RNA-binding proteins TIA-1 and TIAR link the phosphorylation of eIF-2 alpha to the assembly mammalian stress granules. J Cell Biol 147, 1431-1442 (1999).
Hofmann, S., Kedersha, N., Anderson, P. & Ivanov, P. Molecular mechanisms of stress granule assembly and disassembly. Biochim Biophys Acta Mol Cell Res 1868, 118876 (2021). https://doi.org/10.1016/j.bbamcr.2020.118876
Aulas, A. et al. Stress-specific differences in assembly and composition of stress granules and related foci. J Cell Sci 130, 927-937 (2017). https://doi.org/10.1242/jcs.199240

Tags: chronic stress, stress granules, translation regulation

doi: https://doi.org/10.1242/prelights.40124

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