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Chen CC. Electrophysiological Techniques on the Study of Endolysosomal Ion Channels. Handb Exp Pharmacol 2023; 278:217-233. [PMID: 36871125 DOI: 10.1007/164_2023_638] [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: 04/28/2023]
Abstract
Endolysosomal ion channels are a group of ion channel proteins that are functionally expressed on the membrane of endolysosomal vesicles. The electrophysiological properties of these ion channels in the intracellular organelle membrane cannot be observed using conventional electrophysiological techniques. This section compiles the different electrophysiological techniques utilized in recent years to study endolysosomal ion channels and describes their methodological characteristics, emphasizing the most widely used technique for whole endolysosome recordings to date. This includes the use of different pharmacological tools and genetic tools for the application of patch-clamping techniques for specific stages of endolysosomes, allowing the recording of ion channel activity in different organelles, such as recycling endosomes, early endosomes, late endosomes, and lysosomes. These electrophysiological techniques are not only cutting-edge technologies that help to investigate the biophysical properties of known and unknown intracellular ion channels but also help us to investigate the physiopathological role of these ion channels in the distribution of dynamic vesicles and to identify new therapeutic targets for precision medicine and drug screening.
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Affiliation(s)
- Cheng-Chang Chen
- Department of Clinical Laboratory Sciences and Medical Biotechnology, College of Medicine, National Taiwan University, Taipei, Taiwan.
- Department of Laboratory Medicine, National Taiwan University Hospital, Taipei, Taiwan.
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Klier PEZ, Gest AMM, Martin JG, Roo R, Navarro MX, Lesiak L, Deal PE, Dadina N, Tyson J, Schepartz A, Miller EW. Bioorthogonal, Fluorogenic Targeting of Voltage-Sensitive Fluorophores for Visualizing Membrane Potential Dynamics in Cellular Organelles. J Am Chem Soc 2022; 144:12138-12146. [PMID: 35776693 DOI: 10.1021/jacs.2c02664] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Electrical potential differences across lipid bilayers play foundational roles in cellular physiology. Plasma membrane voltage is the most widely studied; however, the bilayers of organelles like mitochondria, lysosomes, nuclei, and the endoplasmic reticulum (ER) also provide opportunities for ionic compartmentalization and the generation of transmembrane potentials. Unlike plasma membranes, organellar bilayers, cloistered within the cell, remain recalcitrant to traditional approaches like patch-clamp electrophysiology. To address the challenge of monitoring changes in organelle membrane potential, we describe the design, synthesis, and application of the LUnAR RhoVR (Ligation Unquenched for Activation and Redistribution Rhodamine-based Voltage Reporter) for optically monitoring membrane potential changes in the ER of living cells. We pair a tetrazine-quenched RhoVR for voltage sensing with a transcyclooctene (TCO)-conjugated ceramide (Cer-TCO) for targeting to the ER. Bright fluorescence is observed only at the coincidence of the LUnAR RhoVR and TCO in the ER, minimizing non-specific, off-target fluorescence. We show that the product of the LUnAR RhoVR and Cer-TCO is voltage-sensitive and that the LUnAR RhoVR can be targeted to an intact ER in living cells. Using the LUnAR RhoVR, we use two-color, ER-localized, fast voltage imaging coupled with cytosolic Ca2+ imaging to validate the electroneutrality of Ca2+ release from internal stores. Finally, we use the LUnAR RhoVR to directly visualize functional coupling between the plasma-ER membranes in patch clamped cell lines, providing the first direct evidence of the sign of the ER potential response to plasma membrane potential changes. We envision that the LUnAR RhoVR, along with other existing organelle-targeting TCO probes, could be applied widely for exploring organelle physiology.
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Affiliation(s)
- Pavel E Z Klier
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Anneliese M M Gest
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Julia G Martin
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Ryan Roo
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Marisol X Navarro
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Lauren Lesiak
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Parker E Deal
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Neville Dadina
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Jonathan Tyson
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Alanna Schepartz
- Department of Chemistry, University of California, Berkeley, California 94720, United States.,Department of Molecular & Cell Biology, University of California, Berkeley, California 94720, United States
| | - Evan W Miller
- Department of Chemistry, University of California, Berkeley, California 94720, United States.,Department of Molecular & Cell Biology, University of California, Berkeley, California 94720, United States.,Helen Wills Neuroscience Institute, University of California, Berkeley, California 94720, United States
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Saminathan A, Devany J, Veetil AT, Suresh B, Pillai KS, Schwake M, Krishnan Y. A DNA-based voltmeter for organelles. NATURE NANOTECHNOLOGY 2021; 16:96-103. [PMID: 33139937 PMCID: PMC8513801 DOI: 10.1038/s41565-020-00784-1] [Citation(s) in RCA: 72] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Accepted: 09/21/2020] [Indexed: 05/16/2023]
Abstract
The role of membrane potential in most intracellular organelles remains unexplored because of the lack of suitable tools. Here, we describe Voltair, a fluorescent DNA nanodevice that reports the absolute membrane potential and can be targeted to organelles in live cells. Voltair consists of a voltage-sensitive fluorophore and a reference fluorophore for ratiometry, and acts as an endocytic tracer. Using Voltair, we could measure the membrane potential of different organelles in situ in live cells. Voltair can potentially guide the rational design of biocompatible electronics and enhance our understanding of how membrane potential regulates organelle biology.
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Affiliation(s)
- Anand Saminathan
- Department of Chemistry, The University of Chicago, Chicago, IL, USA
- Grossman Institute of Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL, USA
| | - John Devany
- Department of Physics, The University of Chicago, Chicago, IL, USA
| | - Aneesh Tazhe Veetil
- Department of Chemistry, The University of Chicago, Chicago, IL, USA
- Grossman Institute of Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL, USA
| | - Bhavyashree Suresh
- Department of Chemistry, The University of Chicago, Chicago, IL, USA
- Grossman Institute of Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL, USA
| | | | - Michael Schwake
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
- Biochemistry III/Faculty of Chemistry, Bielefeld University, Universitätsstraße 25, Bielefeld, Germany
| | - Yamuna Krishnan
- Department of Chemistry, The University of Chicago, Chicago, IL, USA.
- Grossman Institute of Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL, USA.
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