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Updated: Nov 15, 2025
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Published on: August 25, 2020
Measuring Small-molecule Inhibition of Protein Interactions in Live Cells Using FLIM-FRET
James M Pemberton1,2, Qian Liu1, David W Andrews1,2
1Biological Sciences, Sunnybrook Research Institute, Toronto, Ontario, Canada, M4N 3M5.
Abstract:
This protocol was designed to quantitatively measure small-molecule displacement of proteins in live mammalian cells using fluorescence lifetime imaging microscopy-Förster resonance energy transfer (FLIM-FRET). Tumour cell survival is often dependent on anti-apoptotic proteins, which bind to and inhibit pro-apoptotic proteins, thus preventing apoptosis. Small-molecule inhibitors that selectively target these proteins (termed BH3-mimetics) are therefore a promising avenue for the treatment of several cancers. Previous techniques used to study the efficacy of these drugs often use truncated versions of both pro- and anti-apoptotic proteins, as they are membrane bound and hydrophobic in nature. As a result, the true efficacy of these drugs to displace full-length pro-apoptotic proteins in their native environment within a cell is poorly understood. This protocol describes FLIM-FRET methods to directly measure the displacement (or lack of displacement) of full-length Bcl-2 family proteins in live mammalian cells.
Insights
This study introduces a new method using fluorescence lifetime imaging microscopy-Förster resonance energy transfer (FLIM-FRET) to measure how small molecules displace proteins in live cells. This technique assesses the efficacy of cancer drugs targeting apoptosis-regulating proteins.
Area of Science:
- Biochemistry
- Cell Biology
- Pharmacology
Background:
- Tumor cell survival relies on anti-apoptotic proteins that inhibit pro-apoptotic proteins, preventing programmed cell death.
- Small-molecule drugs, known as BH3-mimetics, target these proteins and show promise for cancer treatment.
- Current methods often use truncated protein versions, limiting understanding of drug efficacy on full-length proteins in their native cellular environment.
Purpose of the Study:
- To develop and present a protocol for quantitatively measuring small-molecule displacement of proteins in live mammalian cells.
- To overcome limitations of previous techniques by studying full-length proteins in their native cellular context.
- To directly assess the efficacy of BH3-mimetics in displacing full-length Bcl-2 family proteins.
Main Methods:
- Utilizing fluorescence lifetime imaging microscopy-Förster resonance energy transfer (FLIM-FRET) for quantitative measurements.
- Applying the protocol to live mammalian cells to observe protein interactions in real-time.
- Focusing on the displacement of full-length Bcl-2 family proteins.
Main Results:
- The protocol enables direct measurement of small-molecule-induced displacement of full-length Bcl-2 family proteins.
- FLIM-FRET provides a quantitative assessment of drug efficacy in a native cellular environment.
- The study establishes a method to understand the true impact of BH3-mimetics on apoptosis regulation.
Conclusions:
- The described FLIM-FRET protocol is a powerful tool for evaluating BH3-mimetic drugs.
- This method offers a more accurate assessment of drug efficacy compared to previous techniques.
- Understanding protein displacement in live cells is crucial for developing effective cancer therapies.
