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Martinez KN, Gerstner NC, Yang SJ, Miller EW. Extended voltage imaging in cardiomyocytes with a triplet state quencher-stabilized silicon rhodamine. Bioorg Med Chem Lett 2024; 109:129842. [PMID: 38844174 DOI: 10.1016/j.bmcl.2024.129842] [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: 09/29/2023] [Revised: 05/17/2024] [Accepted: 06/02/2024] [Indexed: 06/18/2024]
Abstract
Voltage imaging of cardiac electrophysiology with voltage-sensitive dyes has long been a powerful complement to traditional methods like patch-clamp electrophysiology. Chemically synthesized voltage sensitive fluorophores offer flexibility for imaging in sensitive samples like human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs), since they do not require genetic transformation of the sample. One serious concern for any fluorescent voltage indicator, whether chemically synthesized or genetically encoded, is phototoxicity. We have been exploring self-healing fluorophores that use triplet state quenchers (TSQs) as a means to reduce the already low phototoxicity of VoltageFluor dyes developed in our lab. We previously showed that conjugation of the TSQ cyclooctatetraene (COT) to a fluorescein based VoltageFluor dye substantially reduced phototoxicity. Here, we show that this approach can be applied to far-red Silicon rhodamine dyes. COT-conjugated Si-rhodamines show improved photostability and reduced phototoxicity in hiPSC-CMs compared to the unmodified dye. This enables imaging of hiPSC-CMs for up to 30 min with continuous illumination. We show that this effect is mediated by a combination of reduced singlet oxygen production and lower loading in the cellular membrane. We discuss future applications and avenues of improvement for TSQ-stabilized VoltageFluor dyes.
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Affiliation(s)
- Kayli N Martinez
- Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720-1460, USA
| | - Nels C Gerstner
- Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720-1460, USA
| | - Samantha J Yang
- Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720-1460, USA
| | - Evan W Miller
- Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720-1460, USA; Department of Molecular & Cell Biology, University of California, Berkeley, Berkeley, CA 94720-1460, USA; Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720-1460, USA.
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Minoshima M, Reja SI, Hashimoto R, Iijima K, Kikuchi K. Hybrid Small-Molecule/Protein Fluorescent Probes. Chem Rev 2024; 124:6198-6270. [PMID: 38717865 DOI: 10.1021/acs.chemrev.3c00549] [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: 05/23/2024]
Abstract
Hybrid small-molecule/protein fluorescent probes are powerful tools for visualizing protein localization and function in living cells. These hybrid probes are constructed by diverse site-specific chemical protein labeling approaches through chemical reactions to exogenous peptide/small protein tags, enzymatic post-translational modifications, bioorthogonal reactions for genetically incorporated unnatural amino acids, and ligand-directed chemical reactions. The hybrid small-molecule/protein fluorescent probes are employed for imaging protein trafficking, conformational changes, and bioanalytes surrounding proteins. In addition, fluorescent hybrid probes facilitate visualization of protein dynamics at the single-molecule level and the defined structure with super-resolution imaging. In this review, we discuss development and the bioimaging applications of fluorescent probes based on small-molecule/protein hybrids.
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Affiliation(s)
- Masafumi Minoshima
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1, Yamadaoka, Suita, Osaka 5650871, Japan
| | - Shahi Imam Reja
- Immunology Frontier Research Center, Osaka University, 2-1, Yamadaoka, Suita, Osaka 5650871, Japan
| | - Ryu Hashimoto
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1, Yamadaoka, Suita, Osaka 5650871, Japan
| | - Kohei Iijima
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1, Yamadaoka, Suita, Osaka 5650871, Japan
| | - Kazuya Kikuchi
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1, Yamadaoka, Suita, Osaka 5650871, Japan
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Gest AM, Grenier V, Miller EW. Optical Estimation of Membrane Potential Values Using Fluorescence Lifetime Imaging Microscopy and Hybrid Chemical-Genetic Voltage Indicators. Bioelectricity 2024; 6:34-41. [PMID: 38516638 PMCID: PMC10951690 DOI: 10.1089/bioe.2023.0027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/23/2024] Open
Abstract
Introduction Membrane potential (Vm), the voltage across a cell membrane, is an important biophysical phenomenon, central to the physiology of cells, tissues, and organisms. Voltage-sensitive fluorescent indicators are a powerful method for interrogating membrane potential in living systems, but most indicators are best suited for detecting changes in membrane potential rather than measuring values of the membrane potential. One promising approach is to use fluorescence lifetime imaging microscopy (FLIM) in combination of chemically synthesized dyes to estimate a value of membrane potential. However, a drawback is that chemically synthesized dyes show poor specificity of staining. Objectives To address this problem, we applied a chemical-genetic voltage imaging approach to FLIM to enable optical estimation of membrane potential values from genetically defined cells. Results In this report, we detail the characterization and evaluation of two of these systems in mammalian cells. We further validate the use of a FLIM-based chemical genetic voltage indicator in mammalian neurons. Conclusions Finally, we discuss opportunities for future improvements to chemical-genetic FLIM-based voltage indicators.
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Affiliation(s)
- Anneliese M.M. Gest
- Department of Chemistry, University of California, Berkeley, California, USA
| | - Vincent Grenier
- Department of Chemistry, University of California, Berkeley, California, USA
| | - Evan W. Miller
- Department of Chemistry, University of California, Berkeley, California, USA
- Department of Molecular & Cell Biology, University of California, Berkeley, California, USA
- Helen Wills Neuroscience Institute, University of California, Berkeley, California, USA
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Fiala T, Mosharov EV, Wang J, Mendieta AM, Choi SJ, Fialova E, Hwu C, Sulzer D, Sames D. Chemical Targeting of Rhodol Voltage-Sensitive Dyes to Dopaminergic Neurons. ACS Chem Neurosci 2022; 13:1251-1262. [PMID: 35400149 DOI: 10.1021/acschemneuro.1c00862] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Optical imaging of changes in the membrane potential of living cells can be achieved by means of fluorescent voltage-sensitive dyes (VSDs). A particularly challenging task is to efficiently deliver these highly lipophilic probes to specific neuronal subpopulations in brain tissue. We have tackled this task by designing a solubilizing, hydrophilic polymer platform that carries a high-affinity ligand for a membrane protein marker of interest and a fluorescent VSD. Here, we disclose an improved design of polymer-supported probes for chemical, nongenetic targeting of voltage sensors to axons natively expressing the dopamine transporter in ex vivo mouse brain tissue. We first show that for negatively charged rhodol VSDs functioning on the photoinduced electron transfer principle, poly(ethylene glycol) as a carrier enables targeting with higher selectivity than the polysaccharide dextran in HEK cell culture. In the same experimental setting, we also demonstrate that incorporation of an azetidine ring into the rhodol chromophore substantially increases the brightness and voltage sensitivity of the respective VSD. We show that the superior properties of the optimized sensor are transferable to recording of electrically evoked activity from dopaminergic axons in mouse striatal slices after averaging of multiple trials. Finally, we suggest the next milestones for the field to achieve single-scan recordings with nongenetically targeted VSDs in native brain tissue.
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Affiliation(s)
- Tomas Fiala
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Eugene V. Mosharov
- Department of Neurology, Columbia University Irving Medical Center, New York, New York 10032, United States
| | - Jihang Wang
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Adriana M. Mendieta
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Se Joon Choi
- Department of Psychiatry, Columbia University Irving Medical Center, New York, New York 10032, United States
| | - Eva Fialova
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Christopher Hwu
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - David Sulzer
- Department of Neurology, Columbia University Irving Medical Center, New York, New York 10032, United States
- Department of Psychiatry, Columbia University Irving Medical Center, New York, New York 10032, United States
- Department of Pharmacology, Columbia University Irving Medical Center, New York, New York 10032, United States
- Department of Molecular Therapeutics, New York State Psychiatric Institute, New York, New York 10032, United States
| | - Dalibor Sames
- Department of Chemistry, Columbia University, New York, New York 10027, United States
- NeuroTechnology Center at Columbia University, New York, New York 10027, United States
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