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Alam SR, Mahadevan MS, Periasamy A. Detecting RNA-Protein Interactions With EGFP-Cy3 FRET by Acceptor Photobleaching. Curr Protoc 2023; 3:e689. [PMID: 36821783 DOI: 10.1002/cpz1.689] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
Abstract
Förster Resonance Energy Transfer (FRET) is a great tool for cell biologists to investigate molecular interactions in live specimens. FRET is a distance-dependent phenomenon which can detect molecular interactions at distances between 1-10 nm. Several FRET approaches are reported in the literature for live and fixed cells to study protein-protein interactions; this protocol provides details of acceptor photobleaching as a FRET method to study RNA-Protein interactions. Cy3-labeled RNA foci (FRET acceptors) are photobleached at the intra-cellular site of interest (the nuclei) and the intensity of the EGFP-tagged proteins (FRET donors) at that same site are measured pre- and post- photobleaching. In principle, FRET is detected if the intensity of EGFP increases after photobleaching of Cy3. This protocol describes necessary steps and appropriate controls to conduct FRET measurements by the acceptor photobleaching method. Successful applications of this protocol will provide data to support the conclusion that EGFP-labeled proteins directly interact with Cy3-labeled RNA at the site of photobleaching. © 2023 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol: FRET in fixed cells Alternate Protocol: FRET in live cells.
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Affiliation(s)
- Shagufta Rehman Alam
- W. M. Keck Center for Cellular Imaging, University of Virginia, Charlottesville, Virginia
| | - Mani S Mahadevan
- Department of Pathology, University of Virginia, Charlottesville, Virginia
| | - Ammasi Periasamy
- W. M. Keck Center for Cellular Imaging, University of Virginia, Charlottesville, Virginia.,Departments of Biology and Biomedical Engineering, University of Virginia, Charlottesville, Virginia
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2
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Menaesse A, Sumetsky D, Emanuely N, Stein JL, Gates EM, Hoffman BD, Boustany NN. Simplified Instrument Calibration for Wide-Field Fluorescence Resonance Energy Transfer (FRET) Measured by the Sensitized Emission Method. Cytometry A 2020; 99:407-416. [PMID: 32700451 DOI: 10.1002/cyto.a.24194] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Revised: 06/30/2020] [Accepted: 07/17/2020] [Indexed: 12/21/2022]
Abstract
Fӧrster (or fluorescence) resonance energy transfer (FRET) is a quantifiable energy transfer in which a donor fluorophore nonradiatively transfers its excitation energy to an acceptor fluorophore. A change in FRET efficiency indicates a change of proximity and environment of these fluorophores, which enables the study of intermolecular interactions. Measurement of FRET efficiency using the sensitized emission method requires a donor-acceptor calibrated system. One of these calibration factors named the G factor, which depends on instrument parameters related to the donor and acceptor measurement channels and on the fluorophores quantum efficiencies, can be determined in several different ways and allows for conversion of the raw donor and acceptor emission signals to FRET efficiency. However, the calculated value of the G factor from experimental data can fluctuate significantly depending on the chosen experimental method and the size of the sample. In this technical note, we extend the results of Gates et al. (Cytometry Part A 95A (2018) 201-213) by refining the calibration method used for calibration of FRET from image pixel data. Instead of using the pixel histograms of two constructs with high and low FRET efficiency to determine the G factor, we use pixel histogram data from one construct of known efficiency. We validate this method by determining the G factor with the same constructs developed and used by Gates et al. and comparing the results from the two approaches. While the two approaches are equivalent theoretically, we demonstrate that the use of a single construct with known efficiency provides a more precise experimental measurement of the G factor that can be attained by collecting a smaller number of images. © 2020 International Society for Advancement of Cytometry.
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Affiliation(s)
- Audrey Menaesse
- Department of Biomedical Engineering, Rutgers University, Piscataway, New Jersey, USA.,School of Life Sciences Engineering, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland
| | - Daniel Sumetsky
- Department of Biomedical Engineering, Rutgers University, Piscataway, New Jersey, USA
| | - Nicolas Emanuely
- Department of Biomedical Engineering, Rutgers University, Piscataway, New Jersey, USA.,Institut d'Optique Graduate School, Palaiseau, France
| | - Jeremy L Stein
- Department of Biomedical Engineering, Rutgers University, Piscataway, New Jersey, USA
| | - Evan M Gates
- Department of Biomedical Engineering, Duke University, Durham, North Carolina, USA
| | - Brenton D Hoffman
- Department of Biomedical Engineering, Duke University, Durham, North Carolina, USA
| | - Nada N Boustany
- Department of Biomedical Engineering, Rutgers University, Piscataway, New Jersey, USA
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3
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Chen X, Yu Y, Zheng P, Jin T, He M, Zheng M, Song X, Jones A, Huang XF. Olanzapine increases AMPK-NPY orexigenic signaling by disrupting H1R-GHSR1a interaction in the hypothalamic neurons of mice. Psychoneuroendocrinology 2020; 114:104594. [PMID: 32007669 DOI: 10.1016/j.psyneuen.2020.104594] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 12/22/2019] [Accepted: 01/17/2020] [Indexed: 12/11/2022]
Abstract
Second generation antipsychotics, particularly olanzapine, induce severe obesity, which is associated with their antagonistic effect on the histamine H1 receptor (H1R). We have previously demonstrated that oral administration of olanzapine increases the concentration of neuropeptide Y (NPY) in the hypothalamus of rats, accompanied by hyperphagia and weight gain. However, it is unclear if the increased NPY after olanzapine administration is due to its direct effect on hypothalamic neurons and its H1R antagonistic property. In the present study, we showed that with an inverted U-shape dose-response curve, olanzapine increased NPY expression in the NPY-GFP hypothalamic neurons; however, this was not the case in the hypothalamic neurons of H1R knockout mice. Olanzapine inhibited the interaction of H1R and GHSR1a (ghrelin receptor) in the primary mouse hypothalamic neurons and NPY-GFP neurons examined by confocal fluorescence resonance energy transfer (FRET) technology. Furthermore, an H1R agonist, FMPH inhibited olanzapine activation of GHSR1a downstream signaling pAMPK and transcription factors of NPY (pFOXO1 and pCREB) in the hypothalamic NPY-GFP cell. However, an olanzapine analogue (E-Olan) with lower affinity to H1R presented negligible enhancement of pCREB within the nucleus of NPY neurons. These findings suggest that the H1R antagonist property of olanzapine inhibits the interaction of H1R and GHSR1a, activates GHSR1a downstream signaling pAMPK-FOXO1/pCREB and increases hypothalamic NPY: this could be one of the important molecular mechanisms of H1R antagonism of olanzapine-induced obesity in antipsychotic management of psychiatric disorders.
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Affiliation(s)
- Xiaoqi Chen
- Department of Endocrinology and Rheumatology, Zhongnan Hospital of Wuhan University, Wuhan 430071, China; Illawarra Health and Medical Research Institute and Molecular Horizons, School of Medicine, University of Wollongong, NSW, 2522, Australia
| | - Yinghua Yu
- Department of Pathogen Biology and Immunology, Xuzhou Medical University and Jiangsu Key Laboratory of Immunity and Metabolism, Xuzhou, Jiangsu 221004, China.
| | - Peng Zheng
- Illawarra Health and Medical Research Institute and Molecular Horizons, School of Medicine, University of Wollongong, NSW, 2522, Australia
| | - Tiantian Jin
- Illawarra Health and Medical Research Institute and Molecular Horizons, School of Medicine, University of Wollongong, NSW, 2522, Australia
| | - Meng He
- School of Chemistry, Wuhan University of Technology, Wuhan, China
| | - Mingxuan Zheng
- Department of Pathogen Biology and Immunology, Xuzhou Medical University and Jiangsu Key Laboratory of Immunity and Metabolism, Xuzhou, Jiangsu 221004, China
| | - Xueqin Song
- School of Psychiatry, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Alison Jones
- Illawarra Health and Medical Research Institute and Molecular Horizons, School of Medicine, University of Wollongong, NSW, 2522, Australia
| | - Xu-Feng Huang
- Illawarra Health and Medical Research Institute and Molecular Horizons, School of Medicine, University of Wollongong, NSW, 2522, Australia.
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4
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Segmented cell analyses to measure redox states of autofluorescent NAD(P)H, FAD & Trp in cancer cells by FLIM. Sci Rep 2018; 8:79. [PMID: 29311591 PMCID: PMC5758727 DOI: 10.1038/s41598-017-18634-x] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Accepted: 12/13/2017] [Indexed: 01/07/2023] Open
Abstract
Multiphoton FLIM microscopy offers many opportunities to investigate processes in live cells, tissue and animal model systems. For redox measurements, FLIM data is mostly published by cell mean values and intensity-based redox ratios. Our method is based entirely on FLIM parameters generated by 3-detector time domain microscopy capturing autofluorescent signals of NAD(P)H, FAD and novel FLIM-FRET application of Tryptophan and NAD(P)H-a2%/FAD-a1% redox ratio. Furthermore, image data is analyzed in segmented cells thresholded by 2 × 2 pixel Regions of Interest (ROIs) to separate mitochondrial oxidative phosphorylation from cytosolic glycolysis in a prostate cancer cell line. Hundreds of data points allow demonstration of heterogeneity in response to intervention, identity of cell responders to treatment, creating thereby different sub-populations. Histograms and bar charts visualize differences between cells, analyzing whole cell versus mitochondrial morphology data, all based on discrete ROIs. This assay method allows to detect subtle differences in cellular and tissue responses, suggesting an advancement over means-based analyses.
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5
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Wallrabe H, Sun Y, Fang X, Periasamy A, Bloom GS. Three-color confocal Förster (or fluorescence) resonance energy transfer microscopy: Quantitative analysis of protein interactions in the nucleation of actin filaments in live cells. Cytometry A 2015; 87:580-8. [PMID: 25755111 PMCID: PMC4452401 DOI: 10.1002/cyto.a.22651] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 01/24/2015] [Accepted: 02/10/2015] [Indexed: 11/07/2022]
Abstract
Experiments using live cell 3-color Förster (or fluorescence) resonance energy transfer (FRET) microscopy and corresponding in vitro biochemical reconstitution of the same proteins were conducted to evaluate actin filament nucleation. A novel application of 3-color FRET data is demonstrated, extending the analysis beyond the customary energy-transfer efficiency (E%) calculations. MDCK cells were transfected for coexpression of Teal-N-WASP/Venus-IQGAP1/mRFP1-Rac1, Teal-N-WASP/Venus-IQGAP1/mRFP1-Cdc42, CFP-Rac1/Venus-IQGAP1/mCherry-actin, or CFP-Cdc42/Venus-IQGAP1/mCherry-actin, and with single-label equivalents for spectral bleedthrough correction. Using confirmed E% as an entry point, fluorescence levels and related ratios were correlated at discrete accumulating levels at cell peripheries. Rising ratios of CFP-Rac1:Venus-IQGAP1 were correlated with lower overall actin fluorescence, whereas the CFP-Cdc42:Venus-IQGAP1 ratio correlated with increased actin fluorescence at low ratios, but was neutral at higher ratios. The new FRET analyses also indicated that rising levels of mRFP1-Cdc42 or mRFP1-Rac1, respectively, promoted or suppressed the association of Teal-N-WASP with Venus-IQGAP1. These 3-color FRET assays further support our in vitro results about the role of IQGAP1, Rac1, and Cdc42 in actin nucleation, and the differential impact of Rac1 and Cdc42 on the association of N-WASP with IQGAP1. In addition, this study emphasizes the power of 3-color FRET as a systems biology strategy for simultaneous evaluation of multiple interacting proteins in individual live cells.
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Affiliation(s)
- Horst Wallrabe
- W. M. Keck Center for Cellular Imaging, University of Virginia, Charlottesville, VA, USA
- Department of Biology, University of Virginia, Charlottesville, VA, USA
| | - Yuansheng Sun
- W. M. Keck Center for Cellular Imaging, University of Virginia, Charlottesville, VA, USA
| | - Xiaolan Fang
- Department of Biology, University of Virginia, Charlottesville, VA, USA
| | - Ammasi Periasamy
- W. M. Keck Center for Cellular Imaging, University of Virginia, Charlottesville, VA, USA
- Department of Biology, University of Virginia, Charlottesville, VA, USA
| | - George S. Bloom
- Department of Biology, University of Virginia, Charlottesville, VA, USA
- Department of Cell Biology, University of Virginia, Charlottesville, VA, USA
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6
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Wallrabe H, Cai Y, Sun Y, Periasamy A, Luzes R, Fang X, Kan HM, Cameron LC, Schafer DA, Bloom GS. IQGAP1 interactome analysis by in vitro reconstitution and live cell 3-color FRET microscopy. Cytoskeleton (Hoboken) 2013; 70:819-36. [PMID: 24124181 DOI: 10.1002/cm.21146] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Accepted: 09/17/2013] [Indexed: 11/10/2022]
Abstract
IQGAP1 stimulates branched actin filament nucleation by activating N-WASP, which then activates the Arp2/3 complex. N-WASP can be activated by other factors, including GTP-bound Cdc42 or Rac1, which also bind IQGAP1. Here we report the use of purified proteins for in vitro binding and actin polymerization assays, and Förster (or fluorescence) resonance energy transfer (FRET) microscopy of cultured cells to illuminate functional interactions among IQGAP1, N-WASP, actin, and either Cdc42 or Rac1. In pyrene-actin assembly assays containing N-WASP and Arp2/3 complex, IQGAP1 plus either small G protein cooperatively stimulated actin filament nucleation by reducing the lag time before 50% maximum actin polymerization was reached. Similarly, Cdc42 and Rac1 modulated the binding of IQGAP1 to N-WASP in a dose-dependent manner, with Cdc42 enhancing the interaction and Rac1 reducing the interaction. These in vitro reconstitution results suggested that IQGAP1 interacts by similar, yet distinct mechanisms with Cdc42 versus Rac1 to regulate actin filament assembly through N-WASP in vivo. The physiological relevance of these multi-protein interactions was substantiated by 3-color FRET microscopy of live MDCK cells expressing various combinations of fluorescent N-WASP, IQGAP1, Cdc42, Rac1, and actin. This study also establishes 3-color FRET microscopy as a powerful tool for studying dynamic intermolecular interactions in live cells.
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Affiliation(s)
- Horst Wallrabe
- Department of Biology, University of Virginia, Charlottesville, Virginia; Keck Center for Cellular Imaging; University of Virginia, Charlottesville, Virginia
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7
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Khan SN, Danishuddin M, Varshney B, Lal SK, Khan AU. Inhibition of N-terminal lysines acetylation and transcription factor assembly by epirubicin induced deranged cell homeostasis. PLoS One 2012; 7:e51850. [PMID: 23251640 PMCID: PMC3522591 DOI: 10.1371/journal.pone.0051850] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2012] [Accepted: 11/07/2012] [Indexed: 01/07/2023] Open
Abstract
Epirubicin (EPI), an anthracycline antitumour antibiotic, is a known intercalating and DNA damaging agent. Here, we study the molecular interaction of EPI with histones and other cellular targets. EPI binding with histone core protein was predicted with spectroscopic and computational techniques. The molecular distance r, between donor (histone H3) and acceptor (EPI) was estimated using Förster’s theory of non-radiation energy transfer and the detailed binding phenomenon is expounded. Interestingly, the concentration dependent reduction in the acetylated states of histone H3 K9/K14 was observed suggesting more repressed chromatin state on EPI treatment. Its binding site near N-terminal lysines is further characterized by thermodynamic determinants and molecular docking studies. Specific DNA binding and inhibition of transcription factor (Tf)-DNA complex formation implicates EPI induced transcriptional inhibition. EPI also showed significant cell cycle arrest in drug treated cells. Chromatin fragmentation and loss of membrane integrity in EPI treated cells is suggestive of their commitment to cell death. This study provides an analysis of nucleosome dynamics during EPI treatment and provides a novel insight into its action.
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Affiliation(s)
- Shahper N Khan
- Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, India.
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9
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Alfonso Pecchio AR, Cardozo Gizzi AM, Renner ML, Molina-Calavita M, Caputto BL. c-Fos activates and physically interacts with specific enzymes of the pathway of synthesis of polyphosphoinositides. Mol Biol Cell 2011; 22:4716-25. [PMID: 21998197 PMCID: PMC3237616 DOI: 10.1091/mbc.e11-03-0259] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
c-Fos increases the overall synthesis of polyphosphoinositides by an AP-1–independent mechanism involving activation of CDP-diacylglycerol synthase and phosphatidylinositol (PtdIns) 4-kinase II α but not of PtdIns synthase or PtdIns 4-kinase II β. Coimmunoprecipitation and FRET experiments show that c-Fos physically associates only with the enzymes it activates. The oncoprotein c-Fos is a well-recognized AP-1 transcription factor. In addition, this protein associates with the endoplasmic reticulum and activates the synthesis of phospholipids. However, the mechanism by which c-Fos stimulates the synthesis of phospholipids in general and the specific lipid pathways activated are unknown. Here we show that induction of quiescent cells to reenter growth promotes an increase in the labeling of polyphosphoinositides that depends on the expression of c-Fos. We also investigated whether stimulation by c-Fos of the synthesis of phosphatidylinositol and its phosphorylated derivatives depends on the activation of enzymes of the phosphatidylinositolphosphate biosynthetic pathway. We found that c-Fos activates CDP-diacylglycerol synthase and phosphatidylinositol (PtdIns) 4-kinase II α in vitro, whereas no activation of phosphatidylinositol synthase or of PtdIns 4-kinase II β was observed. Both coimmunoprecipitation and fluorescence resonance energy transfer experiments consistently showed a physical interaction between the N-terminal domain of c-Fos and the enzymes it activates.
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Affiliation(s)
- Adolfo R Alfonso Pecchio
- Centro de Investigaciones en Química Biológica de Córdoba (Consejo Nacional de Investigaciones Científicas y Técnicas), Departamento de Química Biológica, Universidad Nacional de Córdoba, Ciudad Universitaria, X5000HUA Córdoba, Argentina
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Mitoxantrone Induced Impediment of Histone Acetylation and Structural Flexibility of the Protein. Cell Biochem Biophys 2010; 60:209-18. [DOI: 10.1007/s12013-010-9141-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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11
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Shao H, Zhang W, Hu Q, Wu F, Shen H, Huang S. TCR mispairing in genetically modified T cells was detected by fluorescence resonance energy transfer. Mol Biol Rep 2010; 37:3951-6. [PMID: 20373027 DOI: 10.1007/s11033-010-0053-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2009] [Accepted: 03/05/2010] [Indexed: 02/08/2023]
Abstract
Adoptive transfer of T lymphocytes genetically modified with antigen-specific T cell receptor (TCR) constitutes a promising approach for the treatment of malignant tumors and virus infections. One of the challenges in this field of TCR gene therapy is TCR mispairing defining the incorrect pairing between an introduced TCR α or β chain and an endogenous TCR β or α chain, which results in diluted surface expression of the therapeutic TCR αβ. Although there is currently no clinical evidence for TCR mispairing-induced autoreactivity, the generation of autoreactive TCRs upon TCR mispairing cannot be excluded. So it is important to detect TCR mispairing to evaluate the efficiency of TCR gene therapy. Currently there is no available quantitative assay for the measurement of TCR mispairing. Fluorescence resonance energy transfer (FRET) is a powerful approach for identifying biologically relevant molecular interactions with high spatiotemporal resolution. In this study, we described the method of FRET for the measurement of TCR mispairing. It was found that the average FRET efficiency was 12.2 ± 7.5% in HeLa cells and 8.4 ± 3.3% in Jurkat cells (P = 0.026605). The reduction of FRET efficiency in lymphocytes reflected the presence of mispaired TCRs, indicating there were ~30% TCR mispairing in lymphocytes. This study provides a quantitative intracellular assay that can be used to detect TCR mispairing in genetically modified T lymphocytes.
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Affiliation(s)
- Hongwei Shao
- School of Life Science and Biopharmaceutics, Guangdong Pharmaceutical University, Guangzhou, 510006, People's Republic of China
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12
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Calcium signaling cascade links dopamine D1-D2 receptor heteromer to striatal BDNF production and neuronal growth. Proc Natl Acad Sci U S A 2009; 106:21377-82. [PMID: 19948956 DOI: 10.1073/pnas.0903676106] [Citation(s) in RCA: 204] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Although the perturbation of either the dopaminergic system or brain-derived neurotrophic factor (BDNF) levels has been linked to important neurological and neuropsychiatric disorders, there is no known signaling pathway linking these two major players. We found that the exclusive stimulation of the dopamine D1-D2 receptor heteromer, which we identified in striatal neurons and adult rat brain by using confocal FRET, led to the activation of a signaling cascade that links dopamine signaling to BDNF production and neuronal growth through a cascade of four steps: (i) mobilization of intracellular calcium through Gq, phospholipase C, and inositol trisphosphate, (ii) rapid activation of cytosolic and nuclear calcium/calmodulin-dependent kinase IIalpha, (iii) increased BDNF expression, and (iv) accelerated morphological maturation and differentiation of striatal neurons, marked by increased microtubule-associated protein 2 production. These effects, although robust in striatal neurons from D5(-/-) mice, were absent in neurons from D1(-/-) mice. We also demonstrated that this signaling cascade was activated in adult rat brain, although with regional specificity, being largely limited to the nucleus accumbens. This dopaminergic pathway regulating neuronal growth and maturation through BDNF may have considerable significance in disorders such as drug addiction, schizophrenia, and depression.
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Roda A, Guardigli M, Michelini E, Mirasoli M. Nanobioanalytical luminescence: Förster-type energy transfer methods. Anal Bioanal Chem 2008; 393:109-23. [DOI: 10.1007/s00216-008-2435-8] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Revised: 09/22/2008] [Accepted: 09/23/2008] [Indexed: 12/21/2022]
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Periasamy A, Diaspro A. Visible fluorescent proteins. JOURNAL OF BIOMEDICAL OPTICS 2008; 13:031201. [PMID: 18601525 DOI: 10.1117/1.2939070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
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15
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Chen Y, Mauldin JP, Day RN, Periasamy A. Characterization of spectral FRET imaging microscopy for monitoring nuclear protein interactions. J Microsc 2007; 228:139-52. [PMID: 17970914 DOI: 10.1111/j.1365-2818.2007.01838.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The spectral processed Förster resonance energy transfer (psFRET) imaging method provides an effective and fast method for measuring protein-protein interactions in living specimens. The commercially available linear unmixing algorithms efficiently remove the contribution of donor spectral bleedthrough to the FRET signal. However, the acceptor contribution to spectral bleedthrough in the FRET image cannot be similarly removed, since the acceptor spectrum is identical to the FRET spectrum. Here, we describe the development of a computer algorithm that measures and removes the contaminating ASBT signal in the sFRET image. The new method is characterized in living cells that expressed FRET standards in which the donor and acceptor fluorescent proteins are tethered by amino acid linkers of specific lengths. The method is then used to detect the homo-dimerization of a transcription factor in the nucleus of living cells, and then to measure the interactions of that protein with a second transcription factor.
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Affiliation(s)
- Ye Chen
- W.M. Keck Center for Cellular Imaging, Departments of Biology and Biomedical Engineering, Gilmer Hall, University of Virginia, Charlottesville, VA 22904, USA
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16
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Cheng Z, Xiong Z, Subbarayan M, Chen X, Gambhir SS. 64Cu-labeled alpha-melanocyte-stimulating hormone analog for microPET imaging of melanocortin 1 receptor expression. Bioconjug Chem 2007; 18:765-72. [PMID: 17348700 PMCID: PMC4143155 DOI: 10.1021/bc060306g] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The alpha-melanocyte-stimulating hormone (alpha-MSH) receptor (melanocortin type 1 receptor, or MC1R) plays an important role in the development and growth of melanoma cells. It was found that MC1R was overexpressed on most murine and human melanoma, making it a promising molecular target for melanoma imaging and therapy. Radiolabeled alpha-MSH peptide and its analogs that can specifically bind with MC1R have been extensively explored for developing novel agents for melanoma detection and radionuclide therapy. The goal of this study was to evaluate a 64Cu-labeled alpha-MSH analog, Ac-Nle-Asp-His-D-Phe-Arg-Trp-Gly-Lys(DOTA)-NH2 (DOTA-NAPamide), as a potential molecular probe for microPET imaging of melanoma and MC1R expression in melanoma xenografted mouse models. 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) conjugated NAPamide was synthesized and radiolabeled with 64Cu (t1/2=12 h) in NH4OAc (0.1 M; pH 5.5) buffered solution for 60 min at 50 degrees C. Cell culture studies reveal rapid and high uptake and internalization of 64Cu-DOTA-NAPamide in B16F10 cells. Over 90% of receptor-bound tracer is internalized at 3 h incubation. A cellular retention study demonstrates that the receptor-bound 64Cu-DOTA-NAPamide is slowly released from the B16F10 cells into the medium; 66% of the radioactivity is still associated with the cells even after 3 h incubation. The biodistribution of 64Cu-DOTA-NAPamide was then investigated in C57BL/6 mice bearing subcutaneous murine B16F10 melanoma tumors with high capacity of MC1R and Fox Chase Scid mice bearing human A375M melanoma with a relatively low number of MC1R receptors. Tumor uptake values of 64Cu-DOTA-NAPamide are found to be 4.63 +/- 0.45% and 2.49 +/- 0.31% ID/g in B16F10 and A375M xenografted melanoma at 2 h postinjection (pi), respectively. The B16F10 tumor uptake at 2 h pi is further inhibited to 2.29 +/- 0.24% ID/g, while A375M tumor uptake at 2 h pi remains 2.20 +/- 0.41% ID/g with a coinjection of excess alpha-MSH peptide. MicroPET imaging of 64Cu-DOTA-NAPamide in B16F10 tumor mice clearly shows good tumor localization. However, low A375M tumor uptake and poor tumor to normal tissue contrast were observed. This study demonstrates that 64Cu-DOTA-NAPamide is a promising molecular probe for alpha-MSH receptor positive melanoma PET imaging as well as MC1R expression imaging in living mice.
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Affiliation(s)
- Zhen Cheng
- Molecular Imaging Program at Stanford, Department of Radiology, Stanford University, Stanford, California 94305-5344, USA.
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Wallrabe H, Chen Y, Periasamy A, Barroso M. Issues in confocal microscopy for quantitative FRET analysis. Microsc Res Tech 2006; 69:196-206. [PMID: 16538626 DOI: 10.1002/jemt.20281] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Previously, we have carried out extensive quantitative analysis of Förster (or fluorescence) resonance energy transfer (FRET) data to show that polymeric IgA receptors and their ligands cluster in endocytic membranes in the process of sorting and trafficking in polarized cells. Here, we use a similar technique to assay the organization and distribution of another membrane-bound receptor: transferrin receptor (TFR) and its ligand, holo-transferrin (Tfn), while explaining the step-by-step measures to be taken for successful quantitative analysis of the FRET data. In particular, methodological issues in FRET quantitative imaging, such as spectral bleed-through and background correction, optimal selection of regions of interest, how to deal with outliers and pooling data and statistical analysis of FRET data, are addressed. Our results indicating a clustered organization of TFR-Tfn complexes fit the well-known homodimeric structure of TFR. These quantitative approaches can be adapted for other biological applications of FRET.
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Affiliation(s)
- Horst Wallrabe
- Keck Center for Cellular Imaging, Department of Biology, Gilmer Hall, University of Virginia, Charlottesville, Virginia 22903, USA
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Chen Y, Periasamy A. Intensity Range Based Quantitative FRET Data Analysis to Localize Protein Molecules in Live Cell Nuclei. J Fluoresc 2006; 16:95-104. [PMID: 16397825 DOI: 10.1007/s10895-005-0024-1] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2005] [Accepted: 10/14/2005] [Indexed: 11/27/2022]
Abstract
Förster (fluorescence) resonance energy transfer (FRET) is an ideal technique to estimate the distance between interacting protein molecules in live specimens using intensity-based microscopy. The spectral overlap of donor and acceptor- essential for FRET-also generates a contamination of the FRET signal. There are a number of algorithms available to remove this spectral bleedthrough (SBT) contamination and in this paper we compare two popular algorithms to estimate the SBT element and to calculate a more precise level of energy transfer efficiency, and with that a more accurate distance estimate.
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Affiliation(s)
- Ye Chen
- W.M. Keck Center for Cellular Imaging, University of Virginia, Gilmer Hall, Charlottesville, Virginia 22904, USA
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Abstract
Förster (or fluorescence) resonance energy transfer (FRET) and fluorescence lifetime imaging (FLIM) have moved center stage and are increasingly forming part of multifaceted imaging approaches. They are complementary methodologies that can be applied to advanced quantitative analyses. The widening application of FRET and FLIM has been driven by the availability of suitable fluorophores, increasingly sophisticated microscopy systems, methodologies to correct spectral bleed-through, and the ease with which FRET can be combined with other techniques. FRET and FLIM have recently found use in several applications: in the analysis of protein-protein interactions with high spatial and temporal specificity (e.g. clustering), in the study of conformational changes, in the analysis of binding sequences, and in applications such as high-throughput screening.
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Affiliation(s)
- Horst Wallrabe
- Keck Center for Cellular Imaging, Department of Biology, University of Virginia, Gilmer Hall, Charlottesville, Virginia 22904, USA
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