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Fluorescent Proteins for Investigating Biological Events in Acidic Environments

Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita 565-0871, Japan
The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki 567-0047, Japan
Author to whom correspondence should be addressed.
Int. J. Mol. Sci. 2018, 19(6), 1548;
Received: 2 May 2018 / Revised: 18 May 2018 / Accepted: 19 May 2018 / Published: 23 May 2018
(This article belongs to the Special Issue Fluorescent Proteins)
PDF [2271 KB, uploaded 23 May 2018]


The interior lumen of acidic organelles (e.g., endosomes, secretory granules, lysosomes and plant vacuoles) is an important platform for modification, transport and degradation of biomolecules as well as signal transduction, which remains challenging to investigate using conventional fluorescent proteins (FPs). Due to the highly acidic luminal environment (pH ~ 4.5–6.0), most FPs and related sensors are apt to lose their fluorescence. To address the need to image in acidic environments, several research groups have developed acid-tolerant FPs in a wide color range. Furthermore, the engineering of pH insensitive sensors, and their concomitant use with pH sensitive sensors for the purpose of pH-calibration has enabled characterization of the role of luminal ions. In this short review, we summarize the recent development of acid-tolerant FPs and related functional sensors and discuss the future prospects for this field. View Full-Text
Keywords: fluorescent protein; GFP; acidic organelle; lysosome; secretory granule; endosome; pH; pH-sensitivity; Ca2+; FRET fluorescent protein; GFP; acidic organelle; lysosome; secretory granule; endosome; pH; pH-sensitivity; Ca2+; FRET

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Shinoda, H.; Shannon, M.; Nagai, T. Fluorescent Proteins for Investigating Biological Events in Acidic Environments. Int. J. Mol. Sci. 2018, 19, 1548.

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