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Bischof, Helmut; Rehberg, Markus; Stryeck, Sarah; Artinger, Katharina; Eroglu, Emrah; Waldeck-Weiermair, Markus; Gottschalk, Benjamin; Rost, Rene; Deak, Andras T.; Niedrist, Tobias; Vujic, Nemanja; Lindermuth, Hanna; Prassl, Ruth; Pelzmann, Brigitte; Groschner, Klaus; Kratky, Dagmar; Eller, Kathrin; Rosenkranz, Alexander R.; Madl, Tobias; Plesnila, Nikolaus; Graier, Wolfgang F.; Malli, Roland (2017): Novel genetically encoded fluorescent probes enable real-time detection of potassium in vitro and in vivo. In: Nature Communications, Vol. 8, 1422


Changes in intra-and extracellular potassium ion (K+) concentrations control many important cellular processes and related biological functions. However, our current understanding of the spatiotemporal patterns of physiological and pathological K+ changes is severely limited by the lack of practicable detection methods. We developed K+-sensitive genetically encoded, Forster resonance energy transfer-(FRET) based probes, called GEPIIs, which enable quantitative real-time imaging of K+ dynamics. GEPIIs as purified biosensors are suitable to directly and precisely quantify K+ levels in different body fluids and cell growth media. GEPIIs expressed in cells enable time-lapse and real-time recordings of global and local intracellular K+ signals. Hitherto unknown Ca2+-triggered, organelle-specific K+ changes were detected in pancreatic beta cells. Recombinant GEPIIs also enabled visualization of extracellular K+ fluctuations in vivo with 2-photon microscopy. Therefore, GEPIIs are relevant for diverse K+ assays and open new avenues for live-cell K+ imaging.