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J Neurosci. 2016 Feb 24;36(8):2458-72. doi: 10.1523/JNEUROSCI.3484-15.2016.

A Bright and Fast Red Fluorescent Protein Voltage Indicator That Reports Neuronal Activity in Organotypic Brain Slices.

Author information

1
Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada.
2
Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138.
3
Department of Physiology, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.
4
The John B. Pierce Laboratory, Inc., New Haven, Connecticut 06519, Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06520.
5
The John B. Pierce Laboratory, Inc., New Haven, Connecticut 06519, Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06520, Neurobiology, Yale University School of Medicine, New Haven, Connecticut 06510.
6
Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, Department of Physics, Harvard University, Cambridge, Massachusetts 02138, and Howard Hughes Medical Institute, Harvard University, Cambridge, Massachusetts 02138.
7
Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada, robert.e.campbell@ualberta.ca.

Abstract

Optical imaging of voltage indicators based on green fluorescent proteins (FPs) or archaerhodopsin has emerged as a powerful approach for detecting the activity of many individual neurons with high spatial and temporal resolution. Relative to green FP-based voltage indicators, a bright red-shifted FP-based voltage indicator has the intrinsic advantages of lower phototoxicity, lower autofluorescent background, and compatibility with blue-light-excitable channelrhodopsins. Here, we report a bright red fluorescent voltage indicator (fluorescent indicator for voltage imaging red; FlicR1) with properties that are comparable to the best available green indicators. To develop FlicR1, we used directed protein evolution and rational engineering to screen libraries of thousands of variants. FlicR1 faithfully reports single action potentials (∼3% ΔF/F) and tracks electrically driven voltage oscillations at 100 Hz in dissociated Sprague Dawley rat hippocampal neurons in single trial recordings. Furthermore, FlicR1 can be easily imaged with wide-field fluorescence microscopy. We demonstrate that FlicR1 can be used in conjunction with a blue-shifted channelrhodopsin for all-optical electrophysiology, although blue light photoactivation of the FlicR1 chromophore presents a challenge for applications that require spatially overlapping yellow and blue excitation.

KEYWORDS:

biosensors; fluorescence imaging; fluorescent proteins; genetically encoded indicators; protein engineering; voltage imaging

PMID:
26911693
PMCID:
PMC4764664
DOI:
10.1523/JNEUROSCI.3484-15.2016
[Indexed for MEDLINE]
Free PMC Article
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