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Elife. 2019 Sep 23;8. pii: e44522. doi: 10.7554/eLife.44522. [Epub ahead of print]

Optical estimation of absolute membrane potential using fluorescence lifetime imaging.

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Department of Chemistry, University of California, Berkeley, Berkeley, United States.


All cells maintain ionic gradients across their plasma membranes, producing transmembrane potentials (Vmem). Mounting evidence suggests a relationship between resting Vmem and the physiology of non-excitable cells with implications in diverse areas, including cancer, cellular differentiation, and body patterning. A lack of non-invasive methods to record absolute Vmem limits our understanding of this fundamental signal. To address this need, we developed a fluorescence lifetime-based approach (VF-FLIM) to visualize and optically quantify Vmem with single-cell resolution in mammalian cell culture. Using VF-FLIM, we report Vmem distributions over thousands of cells, a 100-fold improvement relative to electrophysiological approaches. In human carcinoma cells, we visualize the voltage response to growth factor stimulation, stably recording a 10-15 mV hyperpolarization over minutes. Using pharmacological inhibitors, we identify the source of the hyperpolarization as the Ca2+-activated K+ channel KCa3.1. The ability to optically quantify absolute Vmem with cellular resolution will allow a re-examination of its signaling roles.


biochemistry; chemical biology; human; physics of living systems

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Conflict of interest statement

JL, AG The other authors declare that no competing interests exist. EM Evan W Miller, is listed as an inventor on a patent describing voltage-sensitive fluorophores. This patent (US20170315059) is owned by the Regents of the University of California.

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