1
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Haghdoust F, Molakarimi M, Mirshahi M, Sajedi RH. Engineering aequorin to improve thermostability through rigidifying flexible sites. J Mol Struct 2021. [DOI: 10.1016/j.molstruc.2021.130575] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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2
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Nemati R, Molakarimi M, Mohseni A, Taghdir M, Khalifeh K, H. Sajedi R. Thermostability of Ctenophore and Coelenterate Ca 2+-Regulated Apo-photoproteins: A Comparative Study. ACS Chem Biol 2021; 16:1538-1545. [PMID: 34181382 DOI: 10.1021/acschembio.1c00401] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The stabilities of Ca2+-regulated ctenophore and coelenterate apo-photoproteins, apo-mnemiopsin (apo-Mne) and apo-aequorin (apo-Aeq), respectively, were compared biochemically, biophysically, and structurally. Despite high degrees of structural and functional conservation, drastic variations in stability and structural dynamics were found between the two proteins. Irreversible thermoinactivation experiments were performed upon incubation of apo-photoproteins at representative temperatures. The inactivation rate constants (kinact) at 50 °C were determined to be 0.001 and 0.004 min-1 for apo-Mne and apo-Aeq, respectively. Detailed analysis of the inactivation process suggests that the higher thermostability of apo-Mne is due to the higher activation energy (Ea) and subsequently higher values of ΔH* and ΔG* at a given temperature. According to molecular dynamics simulation studies, the higher hydrogen bond, electrostatic, and van der Waals energies in apo-Mne can validate the relationship between the thermal adaptation of apo-Mne and the energy barrier for the inactivation process. Our results show that favorable residues for protein thermostability such as hydrophobic, charged, and adopted α-helical structure residues are more frequent in the apo-Mne structure. Although the effect of acrylamide on fluorescence quenching suggests that the local flexibility in regions around Trp and Tyr residues of apo-Aeq is higher than that of apo-Mne, which results in it having a better ability to penetrate acrylamide molecules, the root-mean-square fluctuation of helix A in apo-Mne is higher than that in apo-Aeq. It seems that the greater flexibility of apo-Mne in these regions may be considered as a determining factor, affecting the thermal stability of apo-Mne through a balance between structural rigidity and flexibility.
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Affiliation(s)
- Robabeh Nemati
- Department of Biochemistry, Faculty of Biological Sciences, Tarbiat Modares University, Tehran 14115-154, Iran
| | - Maryam Molakarimi
- Department of Biochemistry, Faculty of Biological Sciences, Tarbiat Modares University, Tehran 14115-154, Iran
| | - Ammar Mohseni
- Department of Biochemistry, Faculty of Biological Sciences, Tarbiat Modares University, Tehran 14115-154, Iran
| | - Majid Taghdir
- Department of Biophysics, Faculty of Biological Sciences, Tarbiat Modares University, Tehran 14115-154, Iran
| | - Khosrow Khalifeh
- Department of Biology, Faculty of Sciences, University of Zanjan, Zanjan 45371-38791, Iran
| | - Reza H. Sajedi
- Department of Biochemistry, Faculty of Biological Sciences, Tarbiat Modares University, Tehran 14115-154, Iran
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RedquorinXS Mutants with Enhanced Calcium Sensitivity and Bioluminescence Output Efficiently Report Cellular and Neuronal Network Activities. Int J Mol Sci 2020; 21:ijms21217846. [PMID: 33105848 PMCID: PMC7660078 DOI: 10.3390/ijms21217846] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 10/16/2020] [Accepted: 10/19/2020] [Indexed: 01/14/2023] Open
Abstract
Considerable efforts have been focused on shifting the wavelength of aequorin Ca2+-dependent blue bioluminescence through fusion with fluorescent proteins. This approach has notably yielded the widely used GFP-aequorin (GA) Ca2+ sensor emitting green light, and tdTomato-aequorin (Redquorin), whose bioluminescence is completely shifted to red, but whose Ca2+ sensitivity is low. In the present study, the screening of aequorin mutants generated at twenty-four amino acid positions in and around EF-hand Ca2+-binding domains resulted in the isolation of six aequorin single or double mutants (AequorinXS) in EF2, EF3, and C-terminal tail, which exhibited markedly higher Ca2+ sensitivity than wild-type aequorin in vitro. The corresponding Redquorin mutants all showed higher Ca2+ sensitivity than wild-type Redquorin, and four of them (RedquorinXS) matched the Ca2+ sensitivity of GA in vitro. RedquorinXS mutants exhibited unaltered thermostability and peak emission wavelengths. Upon stable expression in mammalian cell line, all RedquorinXS mutants reported the activation of the P2Y2 receptor by ATP with higher sensitivity and assay robustness than wt-Redquorin, and one, RedquorinXS-Q159T, outperformed GA. Finally, wide-field bioluminescence imaging in mouse neocortical slices showed that RedquorinXS-Q159T and GA similarly reported neuronal network activities elicited by the removal of extracellular Mg2+. Our results indicate that RedquorinXS-Q159T is a red light-emitting Ca2+ sensor suitable for the monitoring of intracellular signaling in a variety of applications in cells and tissues, and is a promising candidate for the transcranial monitoring of brain activities in living mice.
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Yu X, Scott D, Dikici E, Joel S, Deo S, Daunert S. Multiplexing cytokine analysis: towards reducing sample volume needs in clinical diagnostics. Analyst 2019; 144:3250-3259. [DOI: 10.1039/c9an00297a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Our work demonstrates the use of both spatial and temporal resolution to quantify multiple analytes based on bioluminescent labels.
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Affiliation(s)
- Xiaowen Yu
- Department of Biochemistry and Molecular Biology
- Miller School of Medicine
- University of Miami
- Miami
- USA
| | - Daniel Scott
- Department of Chemistry
- University of Kentucky
- Lexington
- USA
| | - Emre Dikici
- Department of Biochemistry and Molecular Biology
- Miller School of Medicine
- University of Miami
- Miami
- USA
| | - Smita Joel
- Department of Biochemistry and Molecular Biology
- Miller School of Medicine
- University of Miami
- Miami
- USA
| | - Sapna Deo
- Department of Biochemistry and Molecular Biology
- Miller School of Medicine
- University of Miami
- Miami
- USA
| | - Sylvia Daunert
- Department of Biochemistry and Molecular Biology
- Miller School of Medicine
- University of Miami
- Miami
- USA
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5
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Eremeeva EV, Vysotski ES. Exploring Bioluminescence Function of the Ca2+
-regulated Photoproteins with Site-directed Mutagenesis. Photochem Photobiol 2018; 95:8-23. [DOI: 10.1111/php.12945] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2018] [Accepted: 05/25/2018] [Indexed: 11/29/2022]
Affiliation(s)
- Elena V. Eremeeva
- Photobiology Laboratory; Institute of Biophysics SB RAS; Federal Research Center “Krasnoyarsk Science Center SB RAS”; Krasnoyarsk Russia
| | - Eugene S. Vysotski
- Photobiology Laboratory; Institute of Biophysics SB RAS; Federal Research Center “Krasnoyarsk Science Center SB RAS”; Krasnoyarsk Russia
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6
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Bioluminescence and kinetic aspects of double mutated aequorin variants. Int J Biol Macromol 2018; 112:163-168. [DOI: 10.1016/j.ijbiomac.2018.01.170] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Revised: 01/24/2018] [Accepted: 01/25/2018] [Indexed: 11/21/2022]
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7
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Ebrahimi M, Mohseni A, Khalifeh K, Ranjbar B, Sajedi RH. Evolutionary conservation of EF-hand ΙΙ loop in aequorin: Priority of intensity to decay rate in bioluminescence emission. Arch Biochem Biophys 2017; 634:29-37. [PMID: 28970088 DOI: 10.1016/j.abb.2017.09.018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2017] [Revised: 09/15/2017] [Accepted: 09/28/2017] [Indexed: 12/15/2022]
Abstract
As a Ca2+-regulated photoprotein, aequorin (Aeq) contains four EF-hand motifs, the second one lacks the standard sequence for Ca2+ coordination and doesn't bind to Ca2+. Here, we replaced this loop with a functional loop. According to structural studies, although the global stability of modified aequorin (4EFAeq) is higher than that of Aeq; increasing the local flexibility accompanied by internal structural rearrangements in 4EFAeq result in its penetrability to urea and acrylamide. A fast decay rate was observed for 4EFAeq. Assuming the presence of intermediate states in the luminescent reaction, this observation indicate that the loop replacement leads to the lowering of the half-life of intermediate states which results in increasing the rate of conformational switching of 4EFAeq to light emitting form. However, considerable reduction in initial luminescence intensity of 4EFAeq suggests that the number of functional complexes is reduced. Our findings demonstrate that the conformational effects of the second loop in Aeq elicit a delicate balance between local flexibility and global stability which may be considered as an important functional parameter in photoproteins. It was also concluded that evolutionary conservation of EF-hand ΙΙ in the current form is a consequence of priority of intensity to decay rate in bioluminescent organisms.
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Affiliation(s)
- Mahsa Ebrahimi
- Department of Biology, Faculty of Sciences, University of Zanjan, Zanjan, Iran
| | - Ammar Mohseni
- Department of Biochemistry, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran
| | - Khosrow Khalifeh
- Department of Biology, Faculty of Sciences, University of Zanjan, Zanjan, Iran.
| | - Bijan Ranjbar
- Department of Biophysics, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran
| | - Reza H Sajedi
- Department of Biochemistry, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran.
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8
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Bakayan A, Domingo B, Vaquero CF, Peyriéras N, Llopis J. Fluorescent Protein-photoprotein Fusions and Their Applications in Calcium Imaging. Photochem Photobiol 2017; 93:448-465. [PMID: 27925224 DOI: 10.1111/php.12682] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Accepted: 09/19/2016] [Indexed: 12/21/2022]
Abstract
Calcium-activated photoproteins, such as aequorin, have been used as luminescent Ca2+ indicators since 1967. After the cloning of aequorin in 1985, microinjection was substituted by its heterologous expression, which opened the way for a widespread use. Molecular fusion of green fluorescent protein (GFP) to aequorin recapitulated the nonradiative energy transfer process that occurs in the jellyfish Aequorea victoria, from which these two proteins were obtained, resulting in an increase of light emission and a shift to longer wavelength. The abundance and location of the chimera are seen by fluorescence, whereas its luminescence reports Ca2+ levels. GFP-aequorin is broadly used in an increasing number of studies, from organelles and cells to intact organisms. By fusing other fluorescent proteins to aequorin, the available luminescence color palette has been expanded for multiplexing assays and for in vivo measurements. In this report, we will attempt to review the various photoproteins available, their reported fusions with fluorescent proteins and their biological applications to image Ca2+ dynamics in organelles, cells, tissue explants and in live organisms.
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Affiliation(s)
- Adil Bakayan
- BioEmergences Unit (CNRS, USR3695), Université Paris-Saclay, Gif-sur-Yvette, France
| | - Beatriz Domingo
- Centro Regional de Investigaciones Biomédicas (CRIB) and Facultad de Medicina de Albacete, Universidad de Castilla-La Mancha, Albacete, Spain
| | - Cecilia F Vaquero
- Centro Regional de Investigaciones Biomédicas (CRIB) and Facultad de Medicina de Albacete, Universidad de Castilla-La Mancha, Albacete, Spain
| | - Nadine Peyriéras
- BioEmergences Unit (CNRS, USR3695), Université Paris-Saclay, Gif-sur-Yvette, France
| | - Juan Llopis
- Centro Regional de Investigaciones Biomédicas (CRIB) and Facultad de Medicina de Albacete, Universidad de Castilla-La Mancha, Albacete, Spain
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9
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CdTe quantum dots with green fluorescence generated by bioluminescence resonance energy transfer from aequorin. Mikrochim Acta 2016. [DOI: 10.1007/s00604-016-2057-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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10
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Zare-Shahabadi A, Ataei A, Rezaei N. Proteins brighten the brain. Life Sci 2016; 167:1-5. [DOI: 10.1016/j.lfs.2016.10.024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Revised: 10/09/2016] [Accepted: 10/21/2016] [Indexed: 01/04/2023]
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11
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Grinstead KM, Rowe L, Ensor CM, Joel S, Daftarian P, Dikici E, Zingg JM, Daunert S. Red-Shifted Aequorin Variants Incorporating Non-Canonical Amino Acids: Applications in In Vivo Imaging. PLoS One 2016; 11:e0158579. [PMID: 27367859 PMCID: PMC4930207 DOI: 10.1371/journal.pone.0158579] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Accepted: 06/17/2016] [Indexed: 11/18/2022] Open
Abstract
The increased importance of in vivo diagnostics has posed new demands for imaging technologies. In that regard, there is a need for imaging molecules capable of expanding the applications of current state-of-the-art imaging in vivo diagnostics. To that end, there is a desire for new reporter molecules capable of providing strong signals, are non-toxic, and can be tailored to diagnose or monitor the progression of a number of diseases. Aequorin is a non-toxic photoprotein that can be used as a sensitive marker for bioluminescence in vivo imaging. The sensitivity of aequorin is due to the fact that bioluminescence is a rare phenomenon in nature and, therefore, it does not suffer from autofluorescence, which contributes to background emission. Emission of bioluminescence in the blue-region of the spectrum by aequorin only occurs when calcium, and its luciferin coelenterazine, are bound to the protein and trigger a biochemical reaction that results in light generation. It is this reaction that endows aequorin with unique characteristics, making it ideally suited for a number of applications in bioanalysis and imaging. Herein we report the site-specific incorporation of non-canonical or non-natural amino acids and several coelenterazine analogues, resulting in a catalog of 72 cysteine-free, aequorin variants which expand the potential applications of these photoproteins by providing several red-shifted mutants better suited to use in vivo. In vivo studies in mouse models using the transparent tissue of the eye confirmed the activity of the aequorin variants incorporating L-4-iodophehylalanine and L-4-methoxyphenylalanine after injection into the eye and topical addition of coelenterazine. The signal also remained localized within the eye. This is the first time that aequorin variants incorporating non-canonical amino acids have shown to be active in vivo and useful as reporters in bioluminescence imaging.
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Affiliation(s)
- Kristen M. Grinstead
- Department of Biochemistry and Molecular Biology, R. Bunn Gautier Bldg., 1011 NW 15th Street, Miller School of Medicine, University of Miami, Miami, FL, 33136, United States of America
| | - Laura Rowe
- Department of Chemistry, 1610 Campus Drive East, Valparaiso University, Valparaiso, IN, 46385, United States of America
| | - Charles M. Ensor
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, KY, 40536, United States of America
| | - Smita Joel
- Department of Biochemistry and Molecular Biology, R. Bunn Gautier Bldg., 1011 NW 15th Street, Miller School of Medicine, University of Miami, Miami, FL, 33136, United States of America
| | - Pirouz Daftarian
- Department of Biochemistry and Molecular Biology, R. Bunn Gautier Bldg., 1011 NW 15th Street, Miller School of Medicine, University of Miami, Miami, FL, 33136, United States of America
| | - Emre Dikici
- Department of Biochemistry and Molecular Biology, R. Bunn Gautier Bldg., 1011 NW 15th Street, Miller School of Medicine, University of Miami, Miami, FL, 33136, United States of America
| | - Jean-Marc Zingg
- Department of Biochemistry and Molecular Biology, R. Bunn Gautier Bldg., 1011 NW 15th Street, Miller School of Medicine, University of Miami, Miami, FL, 33136, United States of America
| | - Sylvia Daunert
- Department of Biochemistry and Molecular Biology, R. Bunn Gautier Bldg., 1011 NW 15th Street, Miller School of Medicine, University of Miami, Miami, FL, 33136, United States of America
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12
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Improving the luminescence properties of aequorin by conjugating to CdSe/ZnS quantum dot nanoparticles: Red shift and slowing decay rate. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2016; 162:153-161. [PMID: 27371914 DOI: 10.1016/j.jphotobiol.2016.06.038] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Accepted: 06/22/2016] [Indexed: 12/11/2022]
Abstract
Changing the properties of photoprotein aequorin such as the wavelength emission and decay half-life by using bioluminescence resonance energy transfer (BRET) phenomenon is the main aim in this paper. BRET system was set up with CdSe/ZnS quantum dot nanoparticles as an acceptor molecule and photoprotein as an energy donor molecule. Quantum dots are semiconductor nanoparticles with very interesting optical properties, including broad excitation spectra, narrow and the symmetric band width emission spectra, tunable by their sizes, compositions, negligible photo-bleaching and good chemical and photo-stability. In this QD-BRET system, aequorin is conjugated to the carboxyl groups on quantum dot surface by EDC/NHS chemistry as cross linker. Bioluminescence energy generates by aequorin upon adding Ca(2+) and transfers to the quantum dots in a radiationless manner and emits at a longer wavelength. The determined bioluminescent parameters for this method included aequorin activity, emission spectra and decay half-life time. In fact, this spectrum tuning strategy resulted in a change in bioluminescent properties of photoprotein, therefore, the maximum emission wavelength shifted from 455 to 540nm and the decay time increased from 3.76 to 12.11s. Nowadays, photoproteins with different characteristics are capable of being employed as a reporter in multi-analyte detections and in vivo imaging.
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13
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Grinstead K, Joel S, Zingg JM, Dikici E, Daunert S. Enabling Aequorin for Biotechnology Applications Through Genetic Engineering. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2015:149-179. [PMID: 26475468 DOI: 10.1007/10_2015_336] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
In recent years, luminescent proteins have been studied for their potential application in a variety of detection systems. Bioluminescent proteins, which do not require an external excitation source, are especially well-suited as reporters in analytical detection. The photoprotein aequorin is a bioluminescent protein that can be engineered for use as a molecular reporter under a wide range of conditions while maintaining its sensitivity. Herein, the characteristics of aequorin as well as the engineering and production of aequorin variants and their impact on signal detection in biological systems are presented. The structural features and activity of aequorin, its benefits as a label for sensing and applications in highly sensitive detection, as well as in gaining insight into biological processes are discussed. Among those, focus has been placed on the highly sensitive calcium detection in vivo, in vitro DNA and small molecule sensing, and development of in vivo imaging technologies. Graphical Abstract.
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Affiliation(s)
- Kristen Grinstead
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL, 33136, USA
| | - Smita Joel
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL, 33136, USA
| | - Jean-Marc Zingg
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL, 33136, USA
| | - Emre Dikici
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL, 33136, USA
| | - Sylvia Daunert
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL, 33136, USA.
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14
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Bakayan A, Domingo B, Miyawaki A, Llopis J. Imaging Ca(2+) activity in mammalian cells and zebrafish with a novel red-emitting aequorin variant. Pflugers Arch 2014; 467:2031-42. [PMID: 25355614 PMCID: PMC4537489 DOI: 10.1007/s00424-014-1639-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 10/15/2014] [Accepted: 10/21/2014] [Indexed: 02/04/2023]
Abstract
Ca2+ monitoring with aequorin is an established bioluminescence technique, whereby the photoprotein emits blue light when it binds to Ca2+. However, aequorin’s blue emission and low quantum yield limit its application for in vivo imaging because blue-green light is greatly attenuated in animal tissues. In earlier work, aequorin was molecularly fused with green, yellow, and red fluorescent proteins, producing an emission shift through bioluminescence resonance energy transfer (BRET). We have previously shown that the chimera tandem dimer Tomato-aequorin (tdTA) emits red light in mammalian cells and across the skin and other tissues of mice [1]. In this work, we varied the configuration of the linker in tdTA to maximize energy transfer. One variant, named Redquorin, improved BRET from aequorin to tdTomato to almost a maximum value, and the emission above 575 nm exceeded 73 % of total counts. By pairing Redquorin with appropriate synthetic coelenterazines, agonist-induced and spontaneous Ca2+ oscillations in single HEK-293 cells were imaged. In addition, we also imaged Ca2+ transients associated with twitching behavior in developing zebrafish embryos expressing Redquorin during the segmentation period. Furthermore, the emission profile of Redquorin resulted in significant luminescence crossing a blood sample, a highly absorbing tissue. This new tool will facilitate in vivo imaging of Ca2+ from deep tissues of animals.
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Affiliation(s)
- Adil Bakayan
- Centro Regional de Investigaciones Biomédicas (CRIB) and Facultad de Medicina de Albacete, Universidad Castilla-La Mancha, C/ Almansa 14, 02008, Albacete, Spain
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15
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Qu X, Rowe L, Dikici E, Ensor M, Daunert S. Aequorin mutants with increased thermostability. Anal Bioanal Chem 2014; 406:5639-43. [PMID: 25084737 DOI: 10.1007/s00216-014-8039-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Revised: 06/27/2014] [Accepted: 07/16/2014] [Indexed: 12/01/2022]
Abstract
Bioluminescent labels can be especially useful for in vivo and live animal studies due to the negligible bioluminescence background in cells and most animals, and the non-toxicity of bioluminescent reporter systems. Significant thermal stability of bioluminescent labels is essential, however, due to the longitudinal nature and physiological temperature conditions of many bioluminescent-based studies. To improve the thermostability of the bioluminescent protein aequorin, we employed random and rational mutagenesis strategies to create two thermostable double mutants, S32T/E156V and M36I/E146K, and a particularly thermostable quadruple mutant, S32T/E156V/Q168R/L170I. The double aequorin mutants, S32T/E156V and M36I/E146K, retained 4 and 2.75 times more of their initial bioluminescence activity than wild-type aequorin during thermostability studies at 37 °C. Moreover, the quadruple aequorin mutant, S32T/E156V/Q168R/L170I, exhibited more thermostability at a variety of temperatures than either double mutant alone, producing the most thermostable aequorin mutant identified thus far.
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Affiliation(s)
- Xiaoge Qu
- Department of Chemistry, University of Kentucky, Lexington, KY, 40506, USA
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16
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Abstract
Bioluminescence of Ca2+-binding photoprotein (aequorin, AEQ) is largely enhanced by the co-presence of titanate nanosheets that peptize AEQ agglomerates via a weak electrostatic interaction.
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Affiliation(s)
- Kai Kamada
- Department of Materials Science and Engineering
- Faculty of Engineering
- Nagasaki University
- Nagasaki 852-8521, Japan
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17
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Tricoire L, Lambolez B. Neuronal network imaging in acute slices using Ca2+ sensitive bioluminescent reporter. Methods Mol Biol 2014; 1098:33-45. [PMID: 24166366 DOI: 10.1007/978-1-62703-718-1_3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Genetically encoded indicators are valuable tools to study intracellular signaling cascades in real time using fluorescent or bioluminescent imaging techniques. Imaging of Ca(2+) indicators is widely used to record transient intracellular Ca(2+) increases associated with bioelectrical activity. The natural bioluminescent Ca(2+) sensor aequorin has been historically the first Ca(2+) indicator used to address biological questions. Aequorin imaging offers several advantages over fluorescent reporters: it is virtually devoid of background signal; it does not require light excitation and interferes little with intracellular processes. Genetically encoded sensors such as aequorin are commonly used in dissociated cultured cells; however it becomes more challenging to express them in differentiated intact specimen such as brain tissue. Here we describe a method to express a GFP-aequorin (GA) fusion protein in pyramidal cells of neocortical acute slices using recombinant Sindbis virus. This technique allows expressing GA in several hundreds of neurons on the same slice and to perform the bioluminescence recording of Ca(2+) transients in single neurons or multiple neurons simultaneously.
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Affiliation(s)
- Ludovic Tricoire
- Neurobiologie des processus adaptatifs, UMR7102, Université Pierre et Marie Curie, Paris, France
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18
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Eremeeva EV, Markova SV, Frank LA, Visser AJWG, van Berkel WJH, Vysotski ES. Bioluminescent and spectroscopic properties of His-Trp-Tyr triad mutants of obelin and aequorin. Photochem Photobiol Sci 2013; 12:1016-24. [PMID: 23525241 DOI: 10.1039/c3pp00002h] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ca(2+)-regulated photoproteins are responsible for the bioluminescence of a variety of marine organisms, mostly coelenterates. The photoproteins consist of a single polypeptide chain to which an imidazopyrazinone derivative (2-hydroperoxycoelenterazine) is tightly bound. According to photoprotein spatial structures the side chains of His175, Trp179, and Tyr190 in obelin and His169, Trp173, Tyr184 in aequorin are at distances that allow hydrogen bonding with the peroxide and carbonyl groups of the 2-hydroperoxycoelenterazine ligand. We replaced these amino acids in both photoproteins by residues with different hydrogen bond donor-acceptor capacity. All mutants exhibited luciferase-like bioluminescence activity, hardly present in the wild-type photoproteins, and showed low or no photoprotein activity, except for aeqH169Q (24% of wild-type activity), obeW179Y (23%), obeW179F (67%), obeY190F (14%), and aeqY184F (22%). The results clearly support the supposition made from photoprotein spatial structures that the hydrogen bond network formed by His-Trp-Tyr triad participates in stabilizing the 2-hydroperoxy adduct of coelenterazine. These residues are also essential for the positioning of the 2-hydroperoxycoelenterazine intermediate, light emitting reaction, and for the formation of active photoprotein. In addition, we demonstrate that although the positions of His-Trp-Tyr residues in aequorin and obelin spatial structures are almost identical the substitution effects might be noticeably different.
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Affiliation(s)
- Elena V Eremeeva
- Photobiology Laboratory, Institute of Biophysics, Russian Academy of Sciences, Siberian Branch, Krasnoyarsk, Russia
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Heselpoth RD, Nelson DC. A new screening method for the directed evolution of thermostable bacteriolytic enzymes. J Vis Exp 2012:4216. [PMID: 23169108 PMCID: PMC3520584 DOI: 10.3791/4216] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
Abstract
Directed evolution is defined as a method to harness natural selection in order to engineer proteins to acquire particular properties that are not associated with the protein in nature. Literature has provided numerous examples regarding the implementation of directed evolution to successfully alter molecular specificity and catalysis(1). The primary advantage of utilizing directed evolution instead of more rational-based approaches for molecular engineering relates to the volume and diversity of variants that can be screened(2). One possible application of directed evolution involves improving structural stability of bacteriolytic enzymes, such as endolysins. Bacteriophage encode and express endolysins to hydrolyze a critical covalent bond in the peptidoglycan (i.e. cell wall) of bacteria, resulting in host cell lysis and liberation of progeny virions. Notably, these enzymes possess the ability to extrinsically induce lysis to susceptible bacteria in the absence of phage and furthermore have been validated both in vitro and in vivo for their therapeutic potential(3-5). The subject of our directed evolution study involves the PlyC endolysin, which is composed of PlyCA and PlyCB subunits(6). When purified and added extrinsically, the PlyC holoenzyme lyses group A streptococci (GAS) as well as other streptococcal groups in a matter of seconds and furthermore has been validated in vivo against GAS(7). Significantly, monitoring residual enzyme kinetics after elevated temperature incubation provides distinct evidence that PlyC loses lytic activity abruptly at 45 °C, suggesting a short therapeutic shelf life, which may limit additional development of this enzyme. Further studies reveal the lack of thermal stability is only observed for the PlyCA subunit, whereas the PlyCB subunit is stable up to ~90 °C (unpublished observation). In addition to PlyC, there are several examples in literature that describe the thermolabile nature of endolysins. For example, the Staphylococcus aureus endolysin LysK and Streptococcus pneumoniae endolysins Cpl-1 and Pal lose activity spontaneously at 42 °C, 43.5 °C and 50.2 °C, respectively(8-10). According to the Arrhenius equation, which relates the rate of a chemical reaction to the temperature present in the particular system, an increase in thermostability will correlate with an increase in shelf life expectancy(11). Toward this end, directed evolution has been shown to be a useful tool for altering the thermal activity of various molecules in nature, but never has this particular technology been exploited successfully for the study of bacteriolytic enzymes. Likewise, successful accounts of progressing the structural stability of this particular class of antimicrobials altogether are nonexistent. In this video, we employ a novel methodology that uses an error-prone DNA polymerase followed by an optimized screening process using a 96 well microtiter plate format to identify mutations to the PlyCA subunit of the PlyC streptococcal endolysin that correlate to an increase in enzyme kinetic stability (Figure 1). Results after just one round of random mutagenesis suggest the methodology is generating PlyC variants that retain more than twice the residual activity when compared to wild-type (WT) PlyC after elevated temperature treatment.
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Affiliation(s)
- Ryan D Heselpoth
- Institute for Bioscience and Biotechnology Research, University of Maryland, MD, USA
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Cloning, Sequencing, Expression and Structural Investigation of Mnemiopsin from Mnemiopsis leidyi: An Attempt Toward Understanding Ca2+-Regulated Photoproteins. Protein J 2011; 30:566-74. [DOI: 10.1007/s10930-011-9363-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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Drobac E, Tricoire L, Chaffotte AF, Guiot E, Lambolez B. Calcium imaging in single neurons from brain slices using bioluminescent reporters. J Neurosci Res 2010; 88:695-711. [PMID: 19798746 DOI: 10.1002/jnr.22249] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Responses of three bioluminescent Ca(2+) sensors were studied in vitro and in neurons from brain slices. These sensors consisted of tandem fusions of green fluorescent protein (GFP) with the photoproteins aequorin, obelin, or a mutant aequorin with high Ca(2+) sensitivity. Kinetics of GFP-obelin responses to a saturating Ca(2+) concentration were faster than those of GFP-aequorin at all Mg(2+) concentrations tested, whereas GFP-mutant aequorin responses were the slowest. GFP-photoproteins were efficiently expressed in pyramidal neurons following overnight incubation of acute neocortical slices with recombinant Sindbis viruses. Expression of GFP-photoproteins did not result in conspicuous modification of morphological or electrophysiological properties of layer V pyramidal cells. The three sensors allowed the detection of Ca(2+) transients associated with action potential discharge in single layer V pyramidal neurons. In these neurons, depolarizing steps of increasing amplitude elicited action potential discharge of increasing frequency. Bioluminescent responses of the three sensors were similar in several respects: detection thresholds, an exponential increase with stimulus intensity, photoprotein consumptions, and kinetic properties. These responses, which were markedly slower than kinetics measured in vitro, increased linearly during the action potential discharge and decayed exponentially at the end of the discharge. Onset slopes increased with stimulus intensity, whereas decay kinetics remained constant. Dendritic light emission contributed to whole-field responses, but the spatial resolution of bioluminescence imaging was limited to the soma and proximal apical dendrite. Nonetheless, the high signal-to-background ratio of GFP-photoproteins allowed the detection of Ca(2+) transients associated with 5 action potentials in single neurons upon whole-field bioluminescence recordings.
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Affiliation(s)
- Estelle Drobac
- Université Pierre et Marie Curie-Paris 6, Neurobiologie des Processus Adaptatifs, CNRS UMR 7102, Paris, France
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Dikici E, Qu X, Rowe L, Millner L, Logue C, Deo SK, Ensor M, Daunert S. Aequorin variants with improved bioluminescence properties. Protein Eng Des Sel 2009; 22:243-8. [PMID: 19168563 DOI: 10.1093/protein/gzn083] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The photoprotein aequorin has been widely used as a bioluminescent label in immunoassays, for the determination of calcium concentrations in vivo, and as a reporter in cellular imaging. It is composed of apoaequorin (189 amino acid residues), the imidazopyrazine chromophore coelenterazine and molecular oxygen. The emission characteristics of aequorin can be changed by rational design of the protein to introduce mutations in its structure, as well as by substituting different coelenterazine analogues to yield semi-synthetic aequorins. Variants of aequorin were created by mutating residues His16, Met19, Tyr82, Trp86, Trp108, Phe113 and Tyr132. Forty-two aequorin mutants were prepared and combined with 10 different coelenterazine analogues in a search for proteins with different emission wavelengths, altered decay kinetics and improved stability. This spectral tuning strategy resulted in semi-synthetic photoprotein mutants with significantly altered bioluminescent properties.
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Affiliation(s)
- E Dikici
- Department of Chemistry, University of Kentucky, Lexington, KY 40506-0055, USA
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Tricoire L, Tsuzuki K, Courjean O, Gibelin N, Bourout G, Rossier J, Lambolez B. Calcium dependence of aequorin bioluminescence dissected by random mutagenesis. Proc Natl Acad Sci U S A 2006; 103:9500-5. [PMID: 16769886 PMCID: PMC1480436 DOI: 10.1073/pnas.0603176103] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Aequorin bioluminescence is emitted as a rapidly decaying flash upon calcium binding. Random mutagenesis and functional screening were used to isolate aequorin mutants showing slow decay rate of luminescence. Calcium sensitivity curves were shifted in all mutants, and an intrinsic link between calcium sensitivity and decay rate was suggested by the position of all mutations in or near EF-hand calcium-binding sites. From these results, a low calcium affinity was assigned to the N-terminal EF hand and a high affinity to the C-terminal EF-hand pair. In WT aequorin, the increase of the decay rate with calcium occurred at constant total photon yield and thus determined a corresponding increase of light intensity. Increase of the decay rate was underlain by variations of a fast and a slow component and required the contribution of all three EF hands. Conversely, analyses of double EF-hand mutants suggested that single EF hands are sufficient to trigger luminescence at a slow rate. Finally, a model postulating that proportions of a fast and a slow light-emitting state depend on calcium concentration adequately described the calcium dependence of aequorin bioluminescence. Our results suggest that variations of luminescence kinetics, which depend on three EF hands endowed with different calcium affinities, critically determine the amplitude of aequorin responses to biological calcium signals.
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Affiliation(s)
- Ludovic Tricoire
- Laboratoire de Neurobiologie et Diversité Cellulaire, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7637, Ecole Supérieure de Physique et de Chimie Industrielles, 10 Rue Vauquelin, 75005 Paris, France
| | - Keisuke Tsuzuki
- Laboratoire de Neurobiologie et Diversité Cellulaire, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7637, Ecole Supérieure de Physique et de Chimie Industrielles, 10 Rue Vauquelin, 75005 Paris, France
| | - Olivier Courjean
- Laboratoire de Neurobiologie et Diversité Cellulaire, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7637, Ecole Supérieure de Physique et de Chimie Industrielles, 10 Rue Vauquelin, 75005 Paris, France
| | - Nathalie Gibelin
- Laboratoire de Neurobiologie et Diversité Cellulaire, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7637, Ecole Supérieure de Physique et de Chimie Industrielles, 10 Rue Vauquelin, 75005 Paris, France
| | - Gaëlle Bourout
- Laboratoire de Neurobiologie et Diversité Cellulaire, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7637, Ecole Supérieure de Physique et de Chimie Industrielles, 10 Rue Vauquelin, 75005 Paris, France
| | - Jean Rossier
- Laboratoire de Neurobiologie et Diversité Cellulaire, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7637, Ecole Supérieure de Physique et de Chimie Industrielles, 10 Rue Vauquelin, 75005 Paris, France
| | - Bertrand Lambolez
- Laboratoire de Neurobiologie et Diversité Cellulaire, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7637, Ecole Supérieure de Physique et de Chimie Industrielles, 10 Rue Vauquelin, 75005 Paris, France
- To whom correspondence should be addressed. E-mail:
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