The mTOR-S6 kinase pathway promotes stress granule assembly

Area of Science:

• Cell Biology
• Molecular Biology
• Signaling Pathways

Background:

• Stress granules are cytoplasmic complexes formed during translation inhibition, crucial for cell survival under stress.
• Dysregulation of stress granules is implicated in neurodegenerative diseases, cancer, and aging.

Purpose of the Study:

• To investigate the role of mTOR effector kinases, specifically S6 kinase 1 (S6K1) and S6 kinase 2 (S6K2), in the dynamics of stress granules.
• To establish a connection between mTOR signaling, translation inhibition, and cellular survival mechanisms.

Main Methods:

• Localization studies of S6K1 and S6K2 in human cells under oxidative stress.
• Functional assays to determine the requirement of S6K1 and S6K2 in stress granule assembly and maintenance.
• Investigation of S6 kinase orthologue RSKS-1 in the nematode C. elegans.

Main Results:

• S6K1 and S6K2 were found to localize to stress granules in human cells.
• S6K1 and S6K2 are essential for stress granule assembly and maintenance following oxidative stress.
• S6K1 primarily regulates stress granule formation via eIF2α phosphorylation, while S6K2 is key for their persistence.
• Loss of the C. elegans S6 kinase orthologue RSKS-1 increases stress-induced mortality.

Conclusions:

• S6 kinases are novel regulators of stress granule dynamics.
• This study reveals a new link between the mTOR signaling pathway, translation inhibition, and cellular stress responses.