Dataset Information

FLIM-FRET Imaging of Caspase-3 Activity in Live Cells Using Pair of Red Fluorescent Proteins.

ABSTRACT: We report a new technique to detect enzyme activity inside cells. The method based on Fluorescence Lifetime Imaging (FLIM) technology allows one to follow sensor cleavage by proteolytic enzyme caspase-3. Specifically, we use the FLIM FRET of living cells via the confocal fluorescence microscopy. A specially designed lentivector pLVT with the DNA fragment of TagRFP-23-KFP was applied for transduction of A549 cell lines. Computer simulations are carried out to estimate FRET efficiency and to analyze possible steric restrictions of the reaction between the substrate TagRFP-23-KFP and caspase-3 dimer. Successful use of the fuse protein TagRFP-23-KFP to register the caspase-3 activation based on average life-time measurements is demonstrated. We show that the average life-time distribution is dramatically changed for cells with the modified morphology that is typical for apoptosis. Namely, the short-lived component at 1.8-2.1 ns completely disappears and the long-lived component appears at 2.4-2.6 ns. The latter is a fingerprint of the TagRFP molecule released after cleavage of the TagRFP-23-KFP complex by caspase-3. Analysis of life-time distributions for population of cells allows us to discriminate apoptotic and surviving cells within single frame and to peform statistical analysis of drug efficiency. This system can be adjusted for HTS by using special readers oriented on measurements of fluorescence life-time.

SUBMITTER: Savitsky AP

PROVIDER: S-EPMC3287422 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Publications

FLIM-FRET Imaging of Caspase-3 Activity in Live Cells Using Pair of Red Fluorescent Proteins.

Savitsky Alexander P AP Rusanov Alexander L AL Zherdeva Victoria V VV Gorodnicheva Tatiana V TV Khrenova Maria G MG Nemukhin Alexander V AV

Theranostics 20120215 2

We report a new technique to detect enzyme activity inside cells. The method based on Fluorescence Lifetime Imaging (FLIM) technology allows one to follow sensor cleavage by proteolytic enzyme caspase-3. Specifically, we use the FLIM FRET of living cells via the confocal fluorescence microscopy. A specially designed lentivector pLVT with the DNA fragment of TagRFP-23-KFP was applied for transduction of A549 cell lines. Computer simulations are carried out to estimate FRET efficiency and to analy ...[more]

PMID: 22375160

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Project description:The fluorescent-protein based fluorescence resonance energy transfer (FRET) approach is a powerful method for quantifying protein-protein interactions in living cells, especially when combined with fluorescence lifetime imaging microscopy (FLIM). To compare the performance of different FRET couples for FRET-FLIM experiments, we first tested enhanced green fluorescent protein (EGFP) linked to different red acceptors (mRFP1-EGFP, mStrawberry-EGFP, HaloTag (TMR)-EGFP, and mCherry-EGFP). We obtained a fraction of donor engaged in FRET (f(D)) that was far from the ideal case of one, using different mathematical models assuming a double species model (i.e., discrete double exponential fixing the donor lifetime and double exponential stretched for the FRET lifetime). We show that the relatively low f(D) percentages obtained with these models may be due to spectroscopic heterogeneity of the acceptor population, which is partially caused by different maturation rates for the donor and the acceptor. In an attempt to improve the amount of donor protein engaged in FRET, we tested mTFP1 as a donor coupled to mOrange and EYFP, respectively. mTFP1 turned out to be at least as good as EGFP for donor FRET-FLIM experiments because 1), its lifetime remained constant during light-induced fluorescent changes; 2), its fluorescence decay profile was best fitted with a single exponential model; and 3), no photoconversion was detected. The f(D) value when combined with EYFP as an acceptor was the highest of all tandems tested (0.7). Moreover, in the context of fast acquisitions, we obtained a minimal f(D) (mf(D)) for mTFP1-EYFP that was almost two times greater than that for mCherry-EGFP (0.65 vs. 0.35). Finally, we compared EGFP and mTFP1 in a biological situation in which the fusion proteins were highly immobile, and EGFP and mTFP1 were linked to the histone H4 (EGFP-H4 and mTFP1-H4) in fast FLIM acquisitions. In this particular case, the fluorescence intensity was more stable for EGFP-H4 than for mTFP1-H4. Nevertheless, we show that mTFP1/EYFP stands alone as the best FRET-FLIM couple in terms of f(D) analysis.

Dataset Information

FLIM-FRET Imaging of Caspase-3 Activity in Live Cells Using Pair of Red Fluorescent Proteins.

Publications

FLIM-FRET Imaging of Caspase-3 Activity in Live Cells Using Pair of Red Fluorescent Proteins.

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