A Molecular Sensor Reveals Differences in Macromolecular Crowding between the Cytoplasm and Nucleoplasm

Area of Science:

• Molecular Biology
• Biophysics
• Cell Biology

Background:

• Macromolecular crowding significantly influences cellular processes by altering molecular interactions and reaction kinetics.
• Understanding the spatial distribution of crowding is crucial for deciphering cellular mechanisms.
• Existing methods for measuring intracellular crowding are limited in scope or applicability.

Purpose of the Study:

• To develop and validate a novel molecular sensor for quantifying macromolecular crowding in live cells.
• To investigate the differential crowding environments between the cytosol and nucleus.
• To explore the potential of this sensor in probing nuclear organization and cellular responses.

Main Methods:

• Design and synthesis of an oligonucleotide-based sensor utilizing Förster Resonance Energy Transfer (FRET).
• In vitro characterization of sensor sensitivity to macromolecular volume fraction.
• Introduction of the sensor into cultured cells for real-time imaging of intracellular crowding.
• Modulation of cellular crowding via osmotic stress and pharmacological agents.

Main Results:

• The FRET-based sensor accurately reports macromolecular crowding over a broad dynamic range in vitro.
• Upon cellular introduction, the sensor rapidly equilibrates and exhibits a significant crowding contrast between the cytosol and nucleus.
• Osmotic stress and drugs affecting chromatin organization modulate the observed nuclear-cytosolic crowding contrast.
• The sensor successfully visualizes differences in macromolecular density within cellular compartments.

Conclusions:

• The developed FRET sensor is a sensitive tool for measuring macromolecular crowding in distinct cellular compartments.
• Significant differences in macromolecular crowding exist between the cytoplasm and nucleoplasm, impacting molecular function.
• This sensor provides a new avenue for investigating chromosome organization and the functional consequences of cellular crowding.