1
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Shang A, Shao S, Zhao L, Liu B. Far-Red Fluorescent Proteins: Tools for Advancing In Vivo Imaging. BIOSENSORS 2024; 14:359. [PMID: 39194588 DOI: 10.3390/bios14080359] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2024] [Revised: 07/17/2024] [Accepted: 07/22/2024] [Indexed: 08/29/2024]
Abstract
Far-red fluorescent proteins (FPs) have emerged as indispensable tools in in vivo imaging, playing a pivotal role in elucidating fundamental mechanisms and addressing application issues in biotechnology and biomedical fields. Their ability for deep penetration, coupled with reduced light scattering and absorption, robust resistance to autofluorescence, and diminished phototoxicity, has positioned far-red biosensors at the forefront of non-invasive visualization techniques for observing intracellular activities and intercellular behaviors. In this review, far-red FPs and their applications in living systems are mainly discussed. Firstly, various far-red FPs, characterized by emission peaks spanning from 600 nm to 650 nm, are introduced. This is followed by a detailed presentation of the fundamental principles enabling far-red biosensors to detect biomolecules and environmental changes. Furthermore, the review accentuates the superiority of far-red FPs in multi-color imaging. In addition, significant emphasis is placed on the value of far-red FPs in improving imaging resolution, highlighting their great contribution to the advancement of in vivo imaging.
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Affiliation(s)
- Angyang Shang
- Cancer Hospital of Dalian University of Technology, Shenyang 110042, China
- Liaoning Key Lab of Integrated Circuit and Biomedical Electronic System, Faculty of Medicine, Dalian University of Technology, Dalian 116024, China
| | - Shuai Shao
- Cancer Hospital of Dalian University of Technology, Shenyang 110042, China
- Liaoning Key Lab of Integrated Circuit and Biomedical Electronic System, Faculty of Medicine, Dalian University of Technology, Dalian 116024, China
| | - Luming Zhao
- Cancer Hospital of Dalian University of Technology, Shenyang 110042, China
- Liaoning Key Lab of Integrated Circuit and Biomedical Electronic System, Faculty of Medicine, Dalian University of Technology, Dalian 116024, China
| | - Bo Liu
- Cancer Hospital of Dalian University of Technology, Shenyang 110042, China
- Liaoning Key Lab of Integrated Circuit and Biomedical Electronic System, Faculty of Medicine, Dalian University of Technology, Dalian 116024, China
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2
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Koveal D. Functional principles of genetically encoded fluorescent biosensors for metabolism and their quantitative use. J Neurochem 2024; 168:496-505. [PMID: 37314388 DOI: 10.1111/jnc.15878] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 05/26/2023] [Accepted: 05/30/2023] [Indexed: 06/15/2023]
Abstract
Genetically encoded fluorescent biosensors provide an attractive means of measuring chemical changes in single cells on fast timescales (milliseconds to seconds). While their most prominent application has been in tracking neural activity and neurotransmitter release, there has been growing interest in developing and deploying new versions of these tools to study brain metabolism. However, the careful use of these tools and the interpretation of the data they provide remain challenging. Many biosensors are subject to interferences that can alter sensor responses within a single cell or between cells, producing ambiguous results. This presents a challenge for quantitation and for our ability to accurately interpret sensor responses. This review describes current methods of sensor quantitation, with a focus on cellular interferences that commonly affect sensor performance, ways to avoid false inferences, and recent advances in sensor optimization to make them more robust.
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Affiliation(s)
- Dorothy Koveal
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University School of Medicine, Atlanta, Georgia, USA
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3
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Mukherjee S, Douglas N, Jimenez R. Influence of Fluorescence Lifetime Selections and Conformational Flexibility on Brightness of FusionRed Variants. J Phys Chem Lett 2024; 15:1644-1651. [PMID: 38315162 DOI: 10.1021/acs.jpclett.3c02765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2024]
Abstract
Fluorescent proteins (FPs) for bioimaging are typically developed by screening mutant libraries for clones with improved photophysical properties. This approach has resulted in FPs with high brightness, but the mechanistic origins of the improvements are often unclear. We focused on improving the molecular brightness in the FusionRed family of FPs with fluorescence lifetime selections on targeted libraries, with the aim of reducing nonradiative decay rates. Our new variants show fluorescence quantum yields of up to 75% and lifetimes >3.5 ns. We present a comprehensive analysis of these new FPs, including trends in spectral shifts, photophysical data, photostability, and cellular brightness resulting from codon optimization. We also performed all-atom molecular dynamics simulations to investigate the impact of side chain mutations. The trajectories reveal that individual mutations reduce the flexibility of the chromophore and side chains, leading to an overall reduction in nonradiative rates.
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Affiliation(s)
- Srijit Mukherjee
- JILA, University of Colorado, Boulder, and National Institute of Standards and Technology, 440 UCB, Boulder, Colorado 80309, United States
- Department of Chemistry, University of Colorado, Boulder, 215 UCB, Boulder, Colorado 80309, United States
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Nancy Douglas
- Department of Chemistry, University of Colorado, Boulder, 215 UCB, Boulder, Colorado 80309, United States
| | - Ralph Jimenez
- JILA, University of Colorado, Boulder, and National Institute of Standards and Technology, 440 UCB, Boulder, Colorado 80309, United States
- Department of Chemistry, University of Colorado, Boulder, 215 UCB, Boulder, Colorado 80309, United States
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4
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Ishikawa K, Kobayashi M, Kusano M, Numata K, Kodama Y. Using the organelle glue technique to engineer the plant cell metabolome. PLANT CELL REPORTS 2023; 42:599-607. [PMID: 36705704 DOI: 10.1007/s00299-023-02982-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2022] [Accepted: 01/11/2023] [Indexed: 06/18/2023]
Abstract
By using the organelle glue technique, we artificially manipulated organelle interactions and controlled the plant metabolome at the pathway level. Plant cell metabolic activity changes with fluctuating environmental conditions, in part via adjustments in the arrangement and interaction of organelles. This hints at the potential for designing plants with desirable metabolic activities for food and pharmaceutical industries by artificially controlling the interaction of organelles through genetic modification. We previously developed a method called the organelle glue technique, in which chloroplast-chloroplast adhesion is induced in plant cells using the multimerization properties of split fluorescent proteins. Here, we generated transgenic Arabidopsis (Arabidopsis thaliana) plants in which chloroplasts adhere to each other and performed metabolome analysis to examine the metabolic changes in these lines. In plant cells expressing a construct encoding the red fluorescent protein mCherry targeted to the chloroplast outer envelope by fusion with a signal sequence (cTP-mCherry), chloroplasts adhered to each other and formed chloroplast aggregations. Mitochondria and peroxisomes were embedded in the aggregates, suggesting that normal interactions between chloroplasts and these organelles were also affected. Metabolome analysis of the cTP-mCherry-expressing Arabidopsis shoots revealed significantly higher levels of glycine, serine, and glycerate compared to control plants. Notably, these are photorespiratory metabolites that are normally transported between chloroplasts, mitochondria, and peroxisomes. Together, our data indicate that chloroplast-chloroplast adhesion alters organellar interactions with mitochondria and peroxisomes and disrupts photorespiratory metabolite transport. These results highlight the possibility of controlling plant metabolism at the pathway level by manipulating organelle interactions.
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Affiliation(s)
- Kazuya Ishikawa
- Center for Bioscience Research and Education, Utsunomiya University, Utsunomiya, Tochigi, Japan
- Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama University, Okayama, Japan
| | - Makoto Kobayashi
- RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa, Japan
| | - Miyako Kusano
- RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa, Japan
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan
- Tsukuba-Plant Innovation Research Center, University of Tsukuba, Tsukuba, Ibaraki, Japan
| | - Keiji Numata
- Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, Japan
- Biomacromolecules Research Team, Center for Sustainable Resource Science, RIKEN, Wako, Saitama, Japan
| | - Yutaka Kodama
- Center for Bioscience Research and Education, Utsunomiya University, Utsunomiya, Tochigi, Japan.
- Biomacromolecules Research Team, Center for Sustainable Resource Science, RIKEN, Wako, Saitama, Japan.
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5
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Lee J, Campillo B, Hamidian S, Liu Z, Shorey M, St-Pierre F. Automating the High-Throughput Screening of Protein-Based Optical Indicators and Actuators. Biochemistry 2023; 62:169-177. [PMID: 36315460 PMCID: PMC9852035 DOI: 10.1021/acs.biochem.2c00357] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Over the last 25 years, protein engineers have developed an impressive collection of optical tools to interface with biological systems: indicators to eavesdrop on cellular activity and actuators to poke and prod native processes. To reach the performance level required for their downstream applications, protein-based tools are usually sculpted by iterative rounds of mutagenesis. In each round, libraries of variants are made and evaluated, and the most promising hits are then retrieved, sequenced, and further characterized. Early efforts to engineer protein-based optical tools were largely manual, suffering from low throughput, human error, and tedium. Here, we describe approaches to automating the screening of libraries generated as colonies on agar, multiwell plates, and pooled populations of single-cell variants. We also briefly discuss emerging approaches for screening, including cell-free systems and machine learning.
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Affiliation(s)
- Jihwan Lee
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA
| | - Beatriz Campillo
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA
| | - Shaminta Hamidian
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA
| | - Zhuohe Liu
- Department of Electrical and Computer Engineering, Rice University, Houston, TX 77005, USA
| | - Matthew Shorey
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA
| | - François St-Pierre
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA
- Systems, Synthetic, and Physical Biology Program, Rice University, Houston, TX 77005, USA
- Department of Electrical and Computer Engineering, Rice University, Houston, TX 77005, USA
- Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX, USA
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6
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Mukherjee S, Manna P, Douglas N, Chapagain PP, Jimenez R. Conformational Dynamics of mCherry Variants: A Link between Side-Chain Motions and Fluorescence Brightness. J Phys Chem B 2023; 127:52-61. [PMID: 36574626 DOI: 10.1021/acs.jpcb.2c05584] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The 3-fold higher brightness of the recently developed mCherry-XL red fluorescent protein (FP) compared to its progenitor, mCherry, is due to a significant decrease in the nonradiative decay rate underlying its increased fluorescence quantum yield. To examine the structural and dynamic role of the four mutations that distinguish the two FPs and closely related variants, we employed microsecond time scale, all-atom molecular dynamics simulations. The simulations revealed that the I197R mutation leads to the formation of multiple hydrogen-bonded contacts and increased rigidity of the β-barrel. In particular, mCherryXL showed reduced nanosecond time scale breathing of the gap between the β7 and β10-strands, which was previously shown to be the most flexible region of mCherry. Together with experimental results, the simulations also reveal steric interactions of residue 161 and a network of hydrogen-bonding interactions of the chromophore with residues at positions 59, 143, and 163 that are critical in perturbing the chromophore electronic structure. Finally, we shed light on the conformational dynamics of the conserved residues R95 and S146, which are hydrogen-bonded to the chromophore, and provide physical insights into the observed photophysics. To the best of our knowledge, this is the first study that evaluates the conformational space for a set of closely related FPs generated by directed evolution.
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Affiliation(s)
- Srijit Mukherjee
- JILA, University of Colorado, Boulder and National Institute of Standards and Technology, 440 UCB, Boulder, Colorado 80309, United States.,Department of Chemistry, University of Colorado, Boulder, 215 UCB, Boulder, Colorado 80309, United States
| | - Premashis Manna
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Nancy Douglas
- Department of Chemistry, University of Colorado, Boulder, 215 UCB, Boulder, Colorado 80309, United States
| | - Prem P Chapagain
- Department of Physics, Florida International University, 11200 SW Eighth Street, CP204, Miami, Florida 33199, United States
| | - Ralph Jimenez
- JILA, University of Colorado, Boulder and National Institute of Standards and Technology, 440 UCB, Boulder, Colorado 80309, United States.,Department of Chemistry, University of Colorado, Boulder, 215 UCB, Boulder, Colorado 80309, United States
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7
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Balasubramanian H, Sankaran J, Pandey S, Goh CJH, Wohland T. The dependence of EGFR oligomerization on environment and structure: A camera-based N&B study. Biophys J 2022; 121:4452-4466. [PMID: 36335429 PMCID: PMC9748371 DOI: 10.1016/j.bpj.2022.11.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 09/30/2022] [Accepted: 11/01/2022] [Indexed: 11/06/2022] Open
Abstract
Number and brightness (N&B) analysis is a fluorescence spectroscopy technique to quantify oligomerization of the mobile fraction of proteins. Accurate results, however, rely on a good knowledge of nonfluorescent states of the fluorescent labels, especially of fluorescent proteins, which are widely used in biology. Fluorescent proteins have been characterized for confocal, but not camera-based, N&B, which allows, in principle, faster measurements over larger areas. Here, we calibrate camera-based N&B implemented on a total internal reflection fluorescence microscope for various fluorescent proteins by determining their propensity to be fluorescent. We then apply camera-based N&B in live CHO-K1 cells to determine the oligomerization state of the epidermal growth factor receptor (EGFR), a transmembrane receptor tyrosine kinase that is a crucial regulator of cell proliferation and survival with implications in many cancers. EGFR oligomerization in resting cells and its regulation by the plasma membrane microenvironment are still under debate. Therefore, we investigate the effects of extrinsic factors, including membrane organization, cytoskeletal structure, and ligand stimulation, and intrinsic factors, including mutations in various EGFR domains, on the receptor's oligomerization. Our results demonstrate that EGFR oligomerization increases with removal of cholesterol or sphingolipids or the disruption of GM3-EGFR interactions, indicating raft association. However, oligomerization is not significantly influenced by the cytoskeleton. Mutations in either I706/V948 residues or E685/E687/E690 residues in the kinase and juxtamembrane domains, respectively, lead to a decrease in oligomerization, indicating their necessity for EGFR dimerization. Finally, EGFR phosphorylation is oligomerization dependent, involving the extracellular domain (550-580 residues). Coupled with biochemical investigations, camera-based N&B indicates that EGFR oligomerization and phosphorylation are the outcomes of several molecular interactions involving the lipid content and structure of the cell membrane and multiple residues in the kinase, juxtamembrane, and extracellular domains.
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Affiliation(s)
- Harikrushnan Balasubramanian
- Department of Biological Sciences and NUS Centre for Bio-Imaging Sciences, National University of Singapore, Singapore, Singapore
| | - Jagadish Sankaran
- Department of Biological Sciences and NUS Centre for Bio-Imaging Sciences, National University of Singapore, Singapore, Singapore
| | - Shambhavi Pandey
- Department of Biological Sciences and NUS Centre for Bio-Imaging Sciences, National University of Singapore, Singapore, Singapore
| | - Corinna Jie Hui Goh
- Department of Biological Sciences and NUS Centre for Bio-Imaging Sciences, National University of Singapore, Singapore, Singapore
| | - Thorsten Wohland
- Department of Biological Sciences and NUS Centre for Bio-Imaging Sciences, National University of Singapore, Singapore, Singapore; Department of Chemistry, National University of Singapore, Singapore, Singapore.
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8
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Mukherjee S, Manna P, Hung ST, Vietmeyer F, Friis P, Palmer AE, Jimenez R. Directed Evolution of a Bright Variant of mCherry: Suppression of Nonradiative Decay by Fluorescence Lifetime Selections. J Phys Chem B 2022; 126:4659-4668. [PMID: 35709514 DOI: 10.1021/acs.jpcb.2c01956] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The approximately linear scaling of fluorescence quantum yield (ϕ) with fluorescence lifetime (τ) in fluorescent proteins (FPs) has inspired engineering of brighter fluorophores based on screening for increased lifetimes. Several recently developed FPs such as mTurquoise2, mScarlet, and FusionRed-MQV which have become useful for live cell imaging are products of lifetime selection strategies. However, the underlying photophysical basis of the improved brightness has not been scrutinized. In this study, we focused on understanding the outcome of lifetime-based directed evolution of mCherry, which is a popular red-FP (RFP). We identified four positions (W143, I161, Q163, and I197) near the FP chromophore that can be mutated to create mCherry-XL (eXtended Lifetime: ϕ = 0.70; τ = 3.9 ns). The 3-fold higher quantum yield of mCherry-XL is on par with that of the brightest RFP to date, mScarlet. We examined selected variants within the evolution trajectory and found a near-linear scaling of lifetime with quantum yield and consistent blue-shifts of the absorption and emission spectra. We find that the improvement in brightness is primarily due to a decrease in the nonradiative decay of the excited state. In addition, our analysis revealed the decrease in nonradiative rate is not limited to the blue-shift of the energy gap and changes in the excited state reorganization energy. Our findings suggest that nonradiative mechanisms beyond the scope of energy-gap models such the Englman-Jortner model are suppressed in this lifetime evolution trajectory.
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Affiliation(s)
- Srijit Mukherjee
- JILA, University of Colorado, Boulder and National Institute of Standards and Technology, 440 UCB, Boulder, Colorado 80309, United States.,Department of Chemistry, University of Colorado, Boulder, 215 UCB, Boulder, Colorado 80309, United States
| | - Premashis Manna
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Sheng-Ting Hung
- Department of Physics, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
| | - Felix Vietmeyer
- JILA, University of Colorado, Boulder and National Institute of Standards and Technology, 440 UCB, Boulder, Colorado 80309, United States
| | - Pia Friis
- JILA, University of Colorado, Boulder and National Institute of Standards and Technology, 440 UCB, Boulder, Colorado 80309, United States
| | - Amy E Palmer
- Department of Biochemistry, University of Colorado at Boulder, 596 UCB, Boulder, Colorado 80309, United States.,BioFrontiers Institute, University of Colorado, Boulder, 596 UCB, Boulder, Colorado 80309, United States
| | - Ralph Jimenez
- JILA, University of Colorado, Boulder and National Institute of Standards and Technology, 440 UCB, Boulder, Colorado 80309, United States.,Department of Chemistry, University of Colorado, Boulder, 215 UCB, Boulder, Colorado 80309, United States
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9
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Koveal D, Rosen PC, Meyer DJ, Díaz-García CM, Wang Y, Cai LH, Chou PJ, Weitz DA, Yellen G. A high-throughput multiparameter screen for accelerated development and optimization of soluble genetically encoded fluorescent biosensors. Nat Commun 2022; 13:2919. [PMID: 35614105 PMCID: PMC9133083 DOI: 10.1038/s41467-022-30685-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Accepted: 05/11/2022] [Indexed: 12/30/2022] Open
Abstract
Genetically encoded fluorescent biosensors are powerful tools used to track chemical processes in intact biological systems. However, the development and optimization of biosensors remains a challenging and labor-intensive process, primarily due to technical limitations of methods for screening candidate biosensors. Here we describe a screening modality that combines droplet microfluidics and automated fluorescence imaging to provide an order of magnitude increase in screening throughput. Moreover, unlike current techniques that are limited to screening for a single biosensor feature at a time (e.g. brightness), our method enables evaluation of multiple features (e.g. contrast, affinity, specificity) in parallel. Because biosensor features can covary, this capability is essential for rapid optimization. We use this system to generate a high-performance biosensor for lactate that can be used to quantify intracellular lactate concentrations. This biosensor, named LiLac, constitutes a significant advance in metabolite sensing and demonstrates the power of our screening approach.
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Affiliation(s)
- Dorothy Koveal
- Department of Neurobiology, Harvard Medical School, Boston, MA, USA
| | - Paul C Rosen
- Department of Neurobiology, Harvard Medical School, Boston, MA, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Dylan J Meyer
- Department of Neurobiology, Harvard Medical School, Boston, MA, USA
| | - Carlos Manlio Díaz-García
- Department of Neurobiology, Harvard Medical School, Boston, MA, USA
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Yongcheng Wang
- Department of Physics and John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
- Liangzhu Laboratory, Zhejiang University Medical Center, 1369 West Wenyi Road, Hangzhou, 311121, China
| | - Li-Heng Cai
- Department of Physics and John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
- Department of Materials Science and Engineering, University of Virginia, Charlottesville, VA, USA
| | - Peter J Chou
- Department of Neurobiology, Harvard Medical School, Boston, MA, USA
- Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, USA
| | - David A Weitz
- Department of Physics and John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Gary Yellen
- Department of Neurobiology, Harvard Medical School, Boston, MA, USA.
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10
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Lin CY, Romei MG, Mathews II, Boxer SG. Energetic Basis and Design of Enzyme Function Demonstrated Using GFP, an Excited-State Enzyme. J Am Chem Soc 2022; 144:3968-3978. [PMID: 35200017 PMCID: PMC9014791 DOI: 10.1021/jacs.1c12305] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The past decades have witnessed an explosion of de novo protein designs with a remarkable range of scaffolds. It remains challenging, however, to design catalytic functions that are competitive with naturally occurring counterparts as well as biomimetic or nonbiological catalysts. Although directed evolution often offers efficient solutions, the fitness landscape remains opaque. Green fluorescent protein (GFP), which has revolutionized biological imaging and assays, is one of the most redesigned proteins. While not an enzyme in the conventional sense, GFPs feature competing excited-state decay pathways with the same steric and electrostatic origins as conventional ground-state catalysts, and they exert exquisite control over multiple reaction outcomes through the same principles. Thus, GFP is an "excited-state enzyme". Herein we show that rationally designed mutants and hybrids that contain environmental mutations and substituted chromophores provide the basis for a quantitative model and prediction that describes the influence of sterics and electrostatics on excited-state catalysis of GFPs. As both perturbations can selectively bias photoisomerization pathways, GFPs with fluorescence quantum yields (FQYs) and photoswitching characteristics tailored for specific applications could be predicted and then demonstrated. The underlying energetic landscape, readily accessible via spectroscopy for GFPs, offers an important missing link in the design of protein function that is generalizable to catalyst design.
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Affiliation(s)
- Chi-Yun Lin
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Matthew G Romei
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Irimpan I Mathews
- Stanford Synchrotron Radiation Lightsource, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Steven G Boxer
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
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11
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Babakhanova S, Jung EE, Namikawa K, Zhang H, Wang Y, Subach OM, Korzhenevskiy DA, Rakitina TV, Xiao X, Wang W, Shi J, Drobizhev M, Park D, Eisenhard L, Tang H, Köster RW, Subach FV, Boyden ES, Piatkevich KD. Rapid directed molecular evolution of fluorescent proteins in mammalian cells. Protein Sci 2022; 31:728-751. [PMID: 34913537 PMCID: PMC8862398 DOI: 10.1002/pro.4261] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2021] [Revised: 11/24/2021] [Accepted: 12/14/2021] [Indexed: 12/31/2022]
Abstract
In vivo imaging of model organisms is heavily reliant on fluorescent proteins with high intracellular brightness. Here we describe a practical method for rapid optimization of fluorescent proteins via directed molecular evolution in cultured mammalian cells. Using this method, we were able to perform screening of large gene libraries containing up to 2 × 107 independent random genes of fluorescent proteins expressed in HEK cells, completing one iteration of directed evolution in a course of 8 days. We employed this approach to develop a set of green and near-infrared fluorescent proteins with enhanced intracellular brightness. The developed near-infrared fluorescent proteins demonstrated high performance for fluorescent labeling of neurons in culture and in vivo in model organisms such as Caenorhabditis elegans, Drosophila, zebrafish, and mice. Spectral properties of the optimized near-infrared fluorescent proteins enabled crosstalk-free multicolor imaging in combination with common green and red fluorescent proteins, as well as dual-color near-infrared fluorescence imaging. The described method has a great potential to be adopted by protein engineers due to its simplicity and practicality. We also believe that the new enhanced fluorescent proteins will find wide application for in vivo multicolor imaging of small model organisms.
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12
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Mukherjee S, Jimenez R. Photophysical Engineering of Fluorescent Proteins: Accomplishments and Challenges of Physical Chemistry Strategies. J Phys Chem B 2022; 126:735-750. [DOI: 10.1021/acs.jpcb.1c05629] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Srijit Mukherjee
- JILA, University of Colorado at Boulder and National Institute of Standards and Technology, 440 UCB, Boulder, Colorado 80309, United States
- Department of Chemistry, University of Colorado at Boulder, 215 UCB, Boulder, Colorado 80309, United States
| | - Ralph Jimenez
- JILA, University of Colorado at Boulder and National Institute of Standards and Technology, 440 UCB, Boulder, Colorado 80309, United States
- Department of Chemistry, University of Colorado at Boulder, 215 UCB, Boulder, Colorado 80309, United States
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13
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Mukherjee S, Thomas C, Wilson R, Simmerman E, Hung ST, Jimenez R. Characterizing Dark State Kinetics and Single Molecule Fluorescence of FusionRed and FusionRed-MQ at Low Irradiances. Phys Chem Chem Phys 2022; 24:14310-14323. [DOI: 10.1039/d2cp00889k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The presence of dark states causes fluorescence intermittency of single molecules due to transitions between “on” and “off” states. Genetically encodable markers such as fluorescent proteins (FPs) exhibit dark states...
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14
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Peng B, Dikdan R, Hill SE, Patterson-Orazem AC, Lieberman RL, Fahrni CJ, Dickson RM. Optically Modulated and Optically Activated Delayed Fluorescent Proteins through Dark State Engineering. J Phys Chem B 2021; 125:5200-5209. [PMID: 33978414 DOI: 10.1021/acs.jpcb.1c00649] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Modulating fluorescent protein emission holds great potential for increasing readout sensitivity for applications in biological imaging and detection. Here, we identify and engineer optically modulated yellow fluorescent proteins (EYFP, originally 10C, but renamed EYFP later, and mVenus) to yield new emitters with distinct modulation profiles and unique, optically gated, delayed fluorescence. The parent YFPs are individually modulatable through secondary illumination, depopulating a long-lived dark state to dynamically increase fluorescence. A single point mutation introduced near the chromophore in each of these YFPs provides access to a second, even longer-lived modulatable dark state, while a different double mutant renders EYFP unmodulatable. The naturally occurring dark state in the parent YFPs yields strong fluorescence modulation upon long-wavelength-induced dark state depopulation, allowing selective detection at the frequency at which the long wavelength secondary laser is intensity modulated. Distinct from photoswitches, however, this near IR secondary coexcitation repumps the emissive S1 level from the long-lived triplet state, resulting in optically activated delayed fluorescence (OADF). This OADF results from secondary laser-induced, reverse intersystem crossing (RISC), producing additional nanosecond-lived, visible fluorescence that is delayed by many microseconds after the primary excitation has turned off. Mutation of the parent chromophore environment opens an additional modulation pathway that avoids the OADF-producing triplet state, resulting in a second, much longer-lived, modulatable dark state. These Optically Modulated and Optically Activated Delayed Fluorescent Proteins (OMFPs and OADFPs) are thus excellent for background- and reference-free, high sensitivity cellular imaging, but time-gated OADF offers a second modality for true background-free detection. Our combined structural and spectroscopic data not only gives additional mechanistic details for designing optically modulated fluorescent proteins but also provides the opportunity to distinguish similarly emitting OMFPs through OADF and through their unique modulation spectra.
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Affiliation(s)
- Baijie Peng
- School of Chemistry & Biochemistry and Petit Institute for Biosciences and Bioengineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States
| | - Ryan Dikdan
- School of Chemistry & Biochemistry and Petit Institute for Biosciences and Bioengineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States
| | - Shannon E Hill
- School of Chemistry & Biochemistry and Petit Institute for Biosciences and Bioengineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States
| | - Athéna C Patterson-Orazem
- School of Chemistry & Biochemistry and Petit Institute for Biosciences and Bioengineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States
| | - Raquel L Lieberman
- School of Chemistry & Biochemistry and Petit Institute for Biosciences and Bioengineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States
| | - Christoph J Fahrni
- School of Chemistry & Biochemistry and Petit Institute for Biosciences and Bioengineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States
| | - Robert M Dickson
- School of Chemistry & Biochemistry and Petit Institute for Biosciences and Bioengineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States
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Mukherjee S, Hung ST, Douglas N, Manna P, Thomas C, Ekrem A, Palmer AE, Jimenez R. Engineering of a Brighter Variant of the FusionRed Fluorescent Protein Using Lifetime Flow Cytometry and Structure-Guided Mutations. Biochemistry 2020; 59:3669-3682. [PMID: 32914619 DOI: 10.1021/acs.biochem.0c00484] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The development of fluorescent proteins (FPs) has revolutionized biological imaging. FusionRed, a monomeric red FP (RFP), is known for its low cytotoxicity and correct localization of target fusion proteins in mammalian cells but is limited in application by low fluorescence brightness. We report a brighter variant of FusionRed, "FR-MQV," which exhibits an extended fluorescence lifetime (2.8 ns), enhanced quantum yield (0.53), higher extinction coefficient (∼140 000 M-1 cm-1), increased radiative rate constant, and reduced nonradiative rate constant with respect to its precursor. The properties of FR-MQV derive from three mutations-M42Q, C159V, and the previously identified L175M. A structure-guided approach was used to identify and mutate candidate residues around the para-hydroxyphenyl and the acylimine sites of the chromophore. The C159V mutation was identified via lifetime-based flow cytometry screening of a library in which multiple residues adjacent to the para-hydroxyphenyl site of the chromophore were mutated. The M42Q mutation is located near the acylimine moiety of the chromophore and was discovered using site-directed mutagenesis guided by X-ray crystal structures. FR-MQV exhibits a 3.4-fold higher molecular brightness and a 5-fold increase in the cellular brightness in HeLa cells [based on fluorescence-activated cell sorting (FACS)] compared to FusionRed. It also retains the low cytotoxicity and high-fidelity localization of FusionRed, as demonstrated through assays in mammalian cells. These properties make FR-MQV a promising template for further engineering into a new family of RFPs.
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Affiliation(s)
- Srijit Mukherjee
- JILA, University of Colorado at Boulder and National Institute of Standards and Technology, 440 UCB, Boulder, Colorado 80309, United States
- Department of Chemistry, University of Colorado at Boulder, 215 UCB, Boulder, Colorado 80309, United States
| | - Sheng-Ting Hung
- JILA, University of Colorado at Boulder and National Institute of Standards and Technology, 440 UCB, Boulder, Colorado 80309, United States
| | - Nancy Douglas
- JILA, University of Colorado at Boulder and National Institute of Standards and Technology, 440 UCB, Boulder, Colorado 80309, United States
| | - Premashis Manna
- Department of Chemistry, MIT, 77 Massachusetts Avenue, 18-084, Cambridge, Massachusetts 02139, United States
| | - Connor Thomas
- JILA, University of Colorado at Boulder and National Institute of Standards and Technology, 440 UCB, Boulder, Colorado 80309, United States
| | - Annika Ekrem
- JILA, University of Colorado at Boulder and National Institute of Standards and Technology, 440 UCB, Boulder, Colorado 80309, United States
| | - Amy E Palmer
- Department of Biochemistry, University of Colorado at Boulder, 596 UCB, Boulder, Colorado 80309, United States
- BioFrontiers Institute, University of Colorado, Boulder, 596 UCB, Boulder, Colorado 80309, United States
| | - Ralph Jimenez
- JILA, University of Colorado at Boulder and National Institute of Standards and Technology, 440 UCB, Boulder, Colorado 80309, United States
- Department of Chemistry, University of Colorado at Boulder, 215 UCB, Boulder, Colorado 80309, United States
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Muslinkina L, Pletnev VZ, Pletneva NV, Ruchkin DA, Kolesov DV, Bogdanov AM, Kost LA, Rakitina TV, Agapova YK, Shemyakina II, Chudakov DM, Pletnev S. Two independent routes of post-translational chemistry in fluorescent protein FusionRed. Int J Biol Macromol 2020; 155:551-559. [PMID: 32243936 DOI: 10.1016/j.ijbiomac.2020.03.244] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 03/27/2020] [Accepted: 03/29/2020] [Indexed: 10/24/2022]
Abstract
The crystal structure of monomeric red fluorescent protein FusionRed (λex/λem 580/608 mn) has been determined at 1.09 Å resolution and revealed two alternative routes of post-translational chemistry, resulting in distinctly different products. The refinement occupancies suggest the 60:40 ratio of the mature Met63-Tyr64-Gly65 chromophore and uncyclized chromophore-forming tripeptide with the protein backbone cleaved between Met63 and the preceding Phe62 and oxidized Cα-Cβ bond of Tyr64. We analyzed the structures of FusionRed and several related red fluorescent proteins, identified structural elements causing hydrolysis of the peptide bond, and verified their impact by single point mutagenesis. These findings advance the understanding of the post-translational chemistry of GFP-like fluorescent proteins beyond the canonical cyclization-dehydration-oxidation mechanism. They also show that impaired cyclization does not prevent chromophore-forming tripeptide from further transformations enabled by the same set of catalytic residues. Our mutagenesis efforts resulted in inhibition of the peptide backbone cleavage, and a FusionRed variant with ~30% improved effective brightness.
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Affiliation(s)
- Liya Muslinkina
- Basic Science Program, Frederick National Laboratory for Cancer Research, Argonne, IL 60439, USA
| | - Vladimir Z Pletnev
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Nadya V Pletneva
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Dmitry A Ruchkin
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Danila V Kolesov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Alexey M Bogdanov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Lubov A Kost
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Tatiana V Rakitina
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Yulia K Agapova
- National Research Center "Kurchatov Institute," Moscow, Russia
| | - Irina I Shemyakina
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Dmitry M Chudakov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Sergei Pletnev
- Basic Science Program, Frederick National Laboratory for Cancer Research, Argonne, IL 60439, USA.
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Hung ST, Mukherjee S, Jimenez R. Enrichment of rare events using a multi-parameter high throughput microfluidic droplet sorter. LAB ON A CHIP 2020; 20:834-843. [PMID: 31974539 PMCID: PMC7135947 DOI: 10.1039/c9lc00790c] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
High information content analysis, enrichment, and selection of rare events from a large population are of great importance in biological and biomedical research. The fluorescence lifetime of a fluorophore, a photophysical property which is independent of and complementary to fluorescence intensity, has been incorporated into various imaging and sensing techniques through microscopy, flow cytometry and droplet microfluidics. However, the throughput of fluorescence lifetime activated droplet sorting is orders of magnitude lower than that of fluorescence activated cell sorting, making it unattractive for applications such as directed evolution of enzymes, despite its highly effective compartmentalization of library members. We developed a microfluidic sorter capable of selecting fluorophores based on fluorescence lifetime and brightness at two excitation and emission colors at a maximum droplet rate of 2.5 kHz. We also present a novel selection strategy for efficiently analyzing and/or enriching rare fluorescent members from a large population which capitalizes on the Poisson distribution of analyte encapsulation into droplets. The effectiveness of the droplet sorter and the new selection strategy are demonstrated by enriching rare populations from a ∼108-member site-directed mutagenesis library of fluorescent proteins expressed in bacteria. This selection strategy can in principle be employed on many droplet sorting platforms, and thus can potentially impact broad areas of science where analysis and enrichment of rare events is needed.
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Affiliation(s)
- Sheng-Ting Hung
- JILA, NIST and University of Colorado, Boulder, Colorado 80309, USA.
| | - Srijit Mukherjee
- JILA, NIST and University of Colorado, Boulder, Colorado 80309, USA. and Department of Chemistry, University of Colorado, Boulder, Colorado 80309, USA
| | - Ralph Jimenez
- JILA, NIST and University of Colorado, Boulder, Colorado 80309, USA. and Department of Chemistry, University of Colorado, Boulder, Colorado 80309, USA
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18
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Optimizing the fluorescent protein toolbox and its use. Curr Opin Biotechnol 2019; 58:183-191. [DOI: 10.1016/j.copbio.2019.04.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Accepted: 04/24/2019] [Indexed: 01/07/2023]
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