Colloid osmotic parameterization and measurement of subcellular crowding

Area of Science:

• Biophysics
• Cell Biology
• Biochemistry

Background:

• Macromolecular crowding influences subcellular reactions like protein aggregation and phase separation.
• Quantifying cellular crowding is crucial for understanding these processes.
• Colloid osmotic pressure is proposed as a relevant metric for cellular crowding.

Purpose of the Study:

• To review colloid osmotic pressure as a metric for cellular crowding.
• To discuss methods for measuring intracellular colloid osmotic pressure.
• To evaluate the implications of measured crowding levels for cellular biology.

Main Methods:

• Review of colloid osmotic pressure as a crowding metric.
• Measurement of intracellular colloid osmotic pressure using the nucleus, cytoplasmic gel, and FRET biosensors.
• Analysis of pressure-tension models for nuclear shape.

Main Results:

• Colloid osmotic pressure is generated by macromolecule solutions and drives depletion forces.
• Intracellular colloid osmotic pressure measurements range from 1 to 20 kPa.
• A low value of 1-2 kPa is suggested for frog eggs and potentially other cells.

Conclusions:

• Low intracellular crowding (1-2 kPa) may be prevalent, affecting phase separation biology.
• This finding has implications for buffer design and proteome evolution.
• Colloid osmotic pressure contributes to nuclear shape regulation via a pressure-tension model.