Uncovering Aberrant Mutant PKA Function with Flow Cytometric FRET

Area of Science:

• Biochemistry
• Cell Biology
• Molecular Biology

Background:

• Protein-protein interactions (PPIs) are crucial for biological processes.
• Förster resonance energy transfer (FRET) enables quantitative PPI studies in living cells.
• Flow cytometry offers a platform for high-throughput cellular analysis.

Purpose of the Study:

• To develop a rapid, live-cell FRET-based method for constructing binding curves using flow cytometry.
• To validate the flow cytometry FRET assay against isothermal calorimetry (ITC).
• To investigate the impact of a Cushing syndrome-associated mutation (L206R) on PKA catalytic subunit interactions and function.

Main Methods:

• Development of a flow cytometry-based FRET assay for live-cell PPI analysis.
• Absolute calibration of the flow cytometer for quantitative FRET measurements.
• Validation of the FRET assay using isothermal calorimetry (ITC).
• Application of the assay to study a mutation in PKA's catalytic subunit.

Main Results:

• Successful rapid construction of live-cell FRET-based binding curves.
• Validation of flow cytometric FRET assay against the gold standard ITC.
• Demonstration that the L206R mutation differentially affects PKAcat binding to partners.
• Discovery that the L206R mutation impacts PKAcat's catalytic rate.

Conclusions:

• Flow cytometry-based FRET is a simple, broadly applicable, and powerful tool for quantitative PPI analysis in living cells.
• The Cushing syndrome-causing L206R mutation has complex effects on PKAcat's interactions and enzymatic activity.
• This study enhances mechanistic understanding of the disease-causing mutation.