cytoplasmic stress granule

Definition

Target type: cellularcomponent

A dense aggregation in the cytosol composed of proteins and RNAs that appear when the cell is under stress. [GOC:ans, PMID:17284590, PMID:17601829, PMID:17967451, PMID:20368989]

Cytoplasmic stress granules (SGs) are dynamic, non-membranous RNA-protein (RNP) aggregates that form in the cytoplasm of eukaryotic cells in response to various stresses, such as heat shock, oxidative stress, viral infection, and nutrient deprivation. SGs act as cellular hubs for the sequestration and regulation of mRNAs, proteins, and other cellular components, contributing to cellular adaptation and survival under stress conditions. The core structural component of SGs is a complex network of RNA and proteins. The RNA component of SGs comprises a diverse pool of mRNAs, including mRNAs encoding proteins involved in translation, stress response, and cell cycle control. These mRNAs are typically translationally repressed within SGs, preventing their translation into proteins. The protein component of SGs is equally diverse and includes several key factors involved in mRNA metabolism, translation initiation, and stress response. These proteins include:

* **RNA-binding proteins:** These proteins, such as TIA-1, TIAR, G3BP1, and CAPRIN1, bind to mRNAs and play a role in mRNA sequestration, translation repression, and SG assembly.
* **Translation initiation factors:** These factors, such as eIF4E, eIF4G, and eIF4A, are involved in the initiation of protein synthesis. Their presence in SGs suggests a role in the regulation of translation in response to stress.
* **Stress-response proteins:** These proteins, such as HSP70, HSP90, and p53, are involved in cellular protection and adaptation to stress. Their localization to SGs suggests a role in coordinating the stress response.

The formation and dynamics of SGs are tightly regulated and involve a complex interplay of various factors, including stress signals, signaling pathways, and post-translational modifications. In response to stress, various signaling pathways, such as the MAPK pathway, the p38 pathway, and the JNK pathway, are activated, leading to phosphorylation of key proteins involved in SG assembly, including TIA-1 and TIAR. These phosphorylated proteins then recruit other proteins and mRNAs to the forming SGs.

The formation and disassembly of SGs are dynamic processes, and their composition can vary depending on the nature of the stress and the cell type. Under prolonged stress conditions, SGs can become more stable and may eventually fuse together to form larger aggregates. The fate of SGs after stress resolution depends on the severity and duration of the stress. In some cases, SGs may rapidly dissolve and the sequestered mRNAs may be released for translation. In other cases, SGs may persist for longer periods, potentially contributing to long-term adaptation and survival.

SGs play a crucial role in cellular homeostasis and stress response. Their ability to sequester and regulate mRNAs, proteins, and other cellular components allows cells to adapt to stressful conditions and maintain cellular integrity. Dysregulation of SG formation or function has been implicated in a variety of diseases, including neurodegenerative diseases, cancer, and infectious diseases. Therefore, understanding the mechanisms underlying SG formation and function is essential for developing new therapies for these diseases.

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Proteins (18)

Compounds (2,805)