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Nucleic Acid-Rich Stress Granules Are Not Merely Crowded Condensates: A Quantitative Raman Imaging Study
Ren Shibuya1, Shinji Kajimoto1,2, Hideyuki Yaginuma3,4
1Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba-ku, Sendai 980-8578, Japan.
Analytical Chemistry
|October 15, 2024
Summary
Intracellular droplets, or membraneless organelles, form via liquid-liquid phase separation (LLPS). This study quantifies their chemical composition, revealing variable internal environments crucial for cellular function and disease.
Area of Science:
- Cell Biology
- Biophysics
- Biochemistry
Background:
- Membraneless organelles form through intracellular liquid-liquid phase separation (LLPS).
- These dynamic structures maintain cellular homeostasis but can aggregate in neurodegenerative diseases.
- Quantifying droplet composition is key to understanding their function and pathology.
Purpose of the Study:
- To quantify the chemical components within stress granules (SGs) formed by LLPS in living cells.
- To elucidate the role of intracellular droplet composition in cellular function and stress response.
- To investigate the relationship between LLPS droplet environments and cellular stress types.
Main Methods:
- Near-infrared fluorescence and Raman imaging were employed for chemical analysis.
- Quantitative Raman intensity analysis, using water as an internal standard, determined in situ concentrations.
- Biomolecular C-H band intensity relative to water quantified the crowding environment.
Main Results:
- Nucleic acid concentration within SGs was over 20% higher than in the cytoplasm; lipid concentration was lower.
- The internal environment of SGs varied with stress type: near-cytoplasmic density under oxidative stress, sparser under hyperosmotic stress.
- High nucleic acid concentrations appear critical for maintaining SG internal environments.
Conclusions:
- Intracellular droplets (membraneless organelles) exhibit variable internal environments, not always highly condensed.
- LLPS droplet composition is dynamically regulated by cellular stress.
- Understanding these chemical dynamics is vital for cellular homeostasis and disease research.
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