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bioRxiv · 10.1101/254383

Genetically encoded ratiometric indicators for potassium ion

Shen, Y.·Wu, S.-Y.·Rancic, V.·Qian, Y.·Miyashita, S.-I.·Ballanyi, K.·Campbell, R. E.·Dong, M.
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Abstract

Potassium ion (K+) homeostasis and dynamics play critical roles in regulating various biological activities, and the ability to monitor K+ spatial-temporal dynamics is critical to understanding these biological functions. Here we report the design and characterization of a Forster resonance energy transfer (FRET)-based genetically encoded K+ indicator, KIRIN1, constructed by inserting a bacterial cytosolic K+ binding protein (Kbp) between a fluorescent protein (FP) FRET pair, mCerulean3 and cp173Venus. Binding of K+ induces a conformational change in Kbp, resulting in an increase in FRET efficiency. KIRIN1 was able to detect K+ at physiologically relevant concentrations in vitro and is highly selective toward K+ over Na+. We further demonstrated that KIRIN1 allowed real-time imaging of pharmacologically induced depletion of cytosolic K+ in live cells, and KIRIN1 also enabled optical tracing of K+ efflux and reuptake in neurons upon glutamate stimulation in cultured primary neurons. These results demonstrate that KIRIN1 is a valuable tool to detect K+ in vitro and in live cells.

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Shen, Y., Wu, S.-Y., Rancic, V., Qian, Y., Miyashita, S.-I., Ballanyi, K., Campbell, R. E., Dong, M.. 2018-01-25. Genetically encoded ratiometric indicators for potassium ion. https://doi.org/10.1101/254383

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