Spatial triple-correlation spectroscopy reveals heterotrimer dynamics in live cells

Area of Science:

• Cellular Biology
• Biophysics
• Molecular Imaging

Background:

• Heterotrimeric protein complexes are crucial for intracellular signaling.
• Understanding their dynamic assembly and transport in live cells is challenging.

Purpose of the Study:

• To develop a method for directly detecting and tracking fluorescent heterotrimers in living cells.
• To map the movement of these complexes relative to subcellular architecture.

Main Methods:

• Spatial triple-correlation spectroscopy (S3CS), a fluorescence fluctuation method.
• Integration of three-channel line-scan microscopy with spatial triple-correlation functions.
• Live-cell experiments validating the method's specificity.

Main Results:

• S3CS quantitatively captures heterotrimer formation, diffusion, and transport.
• Successfully tracked Importin-α/Importin-β/NLS cargo complex during nuclear import.
• Demonstrated heterotrimer assembly precedes chromatin engagement for the NF-Y transcription factor.

Conclusions:

• S3CS enables direct resolution of fluorescent ternary assembly dynamics at intracellular boundaries.
• Provides a versatile platform to study how heterotrimeric signaling complexes navigate cellular structures.
• Offers insights into molecular interactions governing complex transport in living cells.