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Sun H, Zhang C, Yuan Y, Gao L, Zhai S, Chen H, Tang Q, Zhuang Z, Chen T. Automated ExEm-spFRET Microscope. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2022; 28:1-8. [PMID: 35184790 DOI: 10.1017/s1431927621013891] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Excitation–emission-spectral unmixing-based fluorescence resonance energy transfer (ExEm-spFRET) microscopy exhibits excellent robustness in living cells. We here develop an automatic ExEm-spFRET microscope with 3.04 s of time resolution for a quantitative FRET imaging. The user-friendly interface software has been designed to operate in two modes: administrator and user. Automatic background recognition, subtraction, and cell segmentation were integrated into the software, which enables FRET calibration or measurement in a one-click operation manner. In administrator mode, both correction factors and spectral fingerprints are only calibrated periodically for a stable system. In user mode, quantitative ExEm-spFRET imaging is directly implemented for FRET samples. We implemented quantitative ExEm-spFRET imaging for living cells expressing different tandem constructs (C80Y, C40Y, C10Y, and C4Y, respectively) and obtained consistent results for at least 3 months, demonstrating the stability of our microscope. Next, we investigated Bcl-xL-Bad interaction by using ExEm-spFRET imaging and FRET two-hybrid assay and found that the Bcl-xL-Bad complexes exist mainly in Bad-Bcl-xL trimers in healthy cells and Bad-Bcl-xL2 trimers in apoptotic cells. We also performed time-lapse FRET imaging on our system for living cells expressing Yellow Cameleon 3.6 (YC3.6) to monitor ionomycin-induced rapid extracellular Ca2+ influx with a time interval of 5 s for total 250 s.
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Affiliation(s)
- Han Sun
- Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou510631, China
- Guangdong Provincial Key Laboratory of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou510631, China
| | - Chenshuang Zhang
- Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou510631, China
- Guangdong Provincial Key Laboratory of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou510631, China
| | - Ye Yuan
- Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou510631, China
- Guangdong Provincial Key Laboratory of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou510631, China
| | - Lu Gao
- Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou510631, China
- Guangdong Provincial Key Laboratory of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou510631, China
| | - Shixian Zhai
- Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou510631, China
- Guangdong Provincial Key Laboratory of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou510631, China
| | - Hongce Chen
- Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou510631, China
- Guangdong Provincial Key Laboratory of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou510631, China
| | - Qilin Tang
- Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou510631, China
- Guangdong Provincial Key Laboratory of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou510631, China
| | - Zhengfei Zhuang
- Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou510631, China
- Guangdong Provincial Key Laboratory of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou510631, China
- SCNU Qingyuan Institutes of Science and Technology Innovation Co., Ltd., Qingyuan511517, China
| | - Tongsheng Chen
- Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou510631, China
- Guangdong Provincial Key Laboratory of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou510631, China
- SCNU Qingyuan Institutes of Science and Technology Innovation Co., Ltd., Qingyuan511517, China
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Farnesylthiosalicylic acid sensitizes hepatocarcinoma cells to artemisinin derivatives. PLoS One 2017; 12:e0171840. [PMID: 28182780 PMCID: PMC5300221 DOI: 10.1371/journal.pone.0171840] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 01/26/2017] [Indexed: 01/03/2023] Open
Abstract
Dihydroartemisinin (DHA) and artesunate (ARS), two artemisinin derivatives, have efficacious anticancer activities against human hepatocarcinoma (HCC) cells. This study aims to study the anticancer action of the combination treatment of DHA/ARS and farnesylthiosalicylic acid (FTS), a Ras inhibitor, in HCC cells (Huh-7 and HepG2 cell lines). FTS pretreatment significantly enhanced DHA/ARS-induced phosphatidylserine (PS) externalization, Bak/Bax activation, mitochondrial membrane depolarization, cytochrome c release, and caspase-8 and -9 activations, characteristics of the extrinsic and intrinsic apoptosis. Pretreatment with Z-IETD-FMK (caspase-8 inhibitor) potently prevented the cytotoxicity of the combination treatment of DHA/ARS and FTS, and pretreatment with Z-VAD-FMK (pan-caspase inhibitor) significantly inhibited the loss of ΔΨm induced by DHA/ARS treatment or the combination treatment of DHA/ARS and FTS in HCC cells. Furthermore, silencing Bak/Bax modestly but significantly inhibited the cytotoxicity of the combination treatment of DHA/ARS and FTS. Interestingly, pretreatment with an antioxidant N-Acetyle-Cysteine (NAC) significantly prevented the cytotoxicity of the combination treatment of DHA and FTS instead of the combination treatment of ARS and FTS, suggesting that reactive oxygen species (ROS) played a key role in the anticancer action of the combination treatment of DHA and FTS. Similar to FTS, DHA/ARS also significantly prevented Ras activation. Collectively, our data demonstrate that FTS potently sensitizes Huh-7 and HepG2 cells to artemisinin derivatives via accelerating the extrinsic and intrinsic apoptotic pathways.
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Zhang J, Lin F, Chai L, Wei L, Chen T. IIem-spFRET: improved Iem-spFRET method for robust FRET measurement. JOURNAL OF BIOMEDICAL OPTICS 2016; 21:105003. [PMID: 27735016 DOI: 10.1117/1.jbo.21.10.105003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2016] [Accepted: 09/22/2016] [Indexed: 06/06/2023]
Abstract
We recently developed a quantitative Förster resonance energy transfer (FRET) measurement method based on emission-spectral unmixing (Iem-spFRET). We here developed an improved Iem-spFRET method (termed as IIem-spFRET) for more robust FRET measurement in living cells. First, two background (BG) spectral fingerprints measured from blank living cells are introduced to remove BG and autofluorescence. Second, we introduce a ? factor denoting the ratio of two molar extinction coefficient ratios (?) of acceptor to donor at two excitations into IIem-spFRET for direct measurement of the ? values using a tandem construct with unknown FRET efficiency (E). We performed IIem-spFRET on our microscope–spectrometer platform to measure the ? values of Venus (V) to Cerulean (C) and the E values of C32V, CVC, VCV, and VCVV constructs, respectively, in living Huh7 cells. For the C32V or CVC cells, the Iem-spFRET and IIem-spFRET methods measured consistent E values. However, for the cells especially with low expressing levels of VCV or VCVV, the E values measured by Iem-spFRET showed large deviations and fluctuations, whereas the IIem-spFRET method greatly improved the measured E values. Collectively, IIem-spFRET is a powerful and robust tool for quantitatively measuring FRET signal in living cells.
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Affiliation(s)
- Jiang Zhang
- South China Normal University, College of Life Science, MOE Key Laboratory of Laser Life Science and Institute of Laser Life Science, Guangzhou 510631, China
| | - Fangrui Lin
- South China Normal University, College of Life Science, MOE Key Laboratory of Laser Life Science and Institute of Laser Life Science, Guangzhou 510631, China
| | - Liuying Chai
- South China Normal University, College of Life Science, MOE Key Laboratory of Laser Life Science and Institute of Laser Life Science, Guangzhou 510631, China
| | - Lichun Wei
- South China Normal University, College of Life Science, MOE Key Laboratory of Laser Life Science and Institute of Laser Life Science, Guangzhou 510631, China
| | - Tongsheng Chen
- South China Normal University, College of Life Science, MOE Key Laboratory of Laser Life Science and Institute of Laser Life Science, Guangzhou 510631, China
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Chai L, Zhang J, Zhang L, Chen T. Miniature fiber optic spectrometer-based quantitative fluorescence resonance energy transfer measurement in single living cells. JOURNAL OF BIOMEDICAL OPTICS 2015; 20:037008. [PMID: 25793494 DOI: 10.1117/1.jbo.20.3.037008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Accepted: 02/16/2015] [Indexed: 05/05/2023]
Abstract
Spectral measurement of fluorescence resonance energy transfer (FRET), spFRET, is a widely used FRET quantification method in living cells today. We set up a spectrometer-microscope platform that consists of a miniature fiber optic spectrometer and a widefield fluorescence microscope for the spectral measurement of absolute FRET efficiency (E) and acceptor-to-donor concentration ratio (R(C)) in single living cells. The microscope was used for guiding cells and the spectra were simultaneously detected by the miniature fiber optic spectrometer. Moreover, our platform has independent excitation and emission controllers, so different excitations can share the same emission channel. In addition, we developed a modified spectral FRET quantification method (mlux-FRET) for the multiple donors and multiple acceptors FRET construct (mD∼nA) sample, and we also developed a spectra-based 2-channel acceptor-sensitized FRET quantification method (spE-FRET). We implemented these modified FRET quantification methods on our platform to measure the absolute E and R(C) values of tandem constructs with different acceptor/donor stoichiometries in single living Huh-7 cells.
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Zhang J, Li H, Chai L, Zhang L, Qu J, Chen T. Quantitative FRET measurement using emission-spectral unmixing with independent excitation crosstalk correction. J Microsc 2014; 257:104-16. [PMID: 25354559 DOI: 10.1111/jmi.12189] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2014] [Accepted: 09/20/2014] [Indexed: 11/26/2022]
Abstract
Quantification of fluorescence resonance energy transfer (FRET) needs at least two external samples, an acceptor-only reference and a linked FRET reference, to calibrate fluorescence signal. Furthermore, all measurements for references and FRET samples must be performed under the same instrumental conditions. Based on a novel notion to predetermine the molar extinction coefficient ratio (RC ) of acceptor-to-donor for the correction of acceptor excitation crosstalk, we present here a robust and independent emission-spectral unmixing FRET methodology, Iem-spFRET, which can simultaneously measure the E and RC of FRET sample without any external references, such that Iem-spFRET circumvents the rigorous restriction of keeping the same imaging conditions for all FRET experiments and thus can be used for the direct measurement of FRET sample. We validate Iem-spFRET by measuring the absolute E and RC values of standard constructs with different acceptor-to-donor stoichiometry expressed in living cells. Our results demonstrate that Iem-spFRET is a simple and powerful tool for real-time monitoring the dynamic intermolecular interaction within single living cells.
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Affiliation(s)
- J Zhang
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou, China
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Spectral measurement of acceptor-to-donor extinction coefficient ratio in living cells. Micron 2014; 68:98-106. [PMID: 25464147 DOI: 10.1016/j.micron.2014.09.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Revised: 08/06/2014] [Accepted: 09/24/2014] [Indexed: 01/16/2023]
Abstract
This report presents a simple method named as sp-ECR to determine the molar extinction coefficient ratio (γ(λex)) of acceptor-to-donor in living cells at excitation wavelength λex, which is closely associated with the acceptor cross-excitation, the hardest issue of FRET quantification. sp-ECR determines γ(λex) by spectrally unmixing the emission spectrum of a donor-acceptor tandem construct under λex excitation without any additional references, such that this method can be performed under optimal imaging condition. We used sp-ECR to measure the γ(458) of Venus/Cerulean in living HepG2 cells on a confocal microscope, and the measured values were consistent with those obtained by lux-FRET method. We also used sp-ECR to measure the γ(458) values of Venus/Cerulean and YFP/CFP as well as YFP/GFP, the commonly used FRET FPs pairs in other two kinds of cancer cell lines on the confocal microscope, and found that the extinction coefficients of FPs depended on cell lines. After predetermining the γ(458) of Venus to ECFP, we used sp-ECR method to monitor the staurosporine (STS)-induced dynamical caspase-3 activation in single live A549 cells expressing SCAT3 by spectrally resolving the absolute FRET efficiency of SCAT3, and found that STS-induced caspase-3 activation in single cells is a very rapid process within 20 min.
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