Genetically encoded fluorescent indicators for imaging intracellular potassium ion concentration

Commun Biol. 2019 Jan 14;2:18. doi: 10.1038/s42003-018-0269-2. eCollection 2019.


Potassium ion (K+) homeostasis and dynamics play critical roles in biological activities. Here we describe three genetically encoded K+ indicators. KIRIN1 (potassium (K) ion ratiometric indicator) and KIRIN1-GR are Förster resonance energy transfer (FRET)-based indicators with a bacterial K+ binding protein (Kbp) inserting between the fluorescent protein FRET pairs mCerulean3/cp173Venus and Clover/mRuby2, respectively. GINKO1 (green indicator of K+ for optical imaging) is a single fluorescent protein-based K+ indicator constructed by insertion of Kbp into enhanced green fluorescent protein (EGFP). These indicators are suitable for detecting K+ at physiologically relevant concentrations in vitro and in cells. KIRIN1 enabled imaging of cytosolic K+ depletion in live cells and K+ efflux and reuptake in cultured neurons. GINKO1, in conjunction with red fluorescent Ca2+ indicator, enable dual-color imaging of K+ and Ca2+ dynamics in neurons and glial cells. These results demonstrate that KIRIN1 and GINKO1 are useful tools for imaging intracellular K+ dynamics.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calcium / metabolism
  • Carrier Proteins / genetics
  • Cations, Monovalent / metabolism*
  • Cytosol / metabolism*
  • Escherichia coli / metabolism
  • Escherichia coli Proteins / genetics
  • Fluorescence Resonance Energy Transfer / methods
  • Fluorescent Dyes / metabolism
  • Green Fluorescent Proteins / genetics*
  • Green Fluorescent Proteins / metabolism*
  • HeLa Cells
  • Humans
  • Ions
  • Luminescent Proteins / metabolism
  • Microscopy, Fluorescence / methods
  • Osmolar Concentration
  • Plasmids / genetics
  • Potassium / metabolism*


  • Carrier Proteins
  • Cations, Monovalent
  • Escherichia coli Proteins
  • Fluorescent Dyes
  • Ions
  • Luminescent Proteins
  • enhanced green fluorescent protein
  • red fluorescent protein
  • Green Fluorescent Proteins
  • Potassium
  • Calcium