Genetically encoded fluorescent indicators for imaging intracellular potassium ion concentration

Area of Science:

• Biochemistry
• Cell Biology
• Neuroscience

Background:

• Potassium ion (K+) homeostasis is vital for cellular functions.
• Existing methods for measuring intracellular K+ have limitations.

Purpose of the Study:

• To develop novel genetically encoded indicators for real-time imaging of intracellular K+ dynamics.
• To validate the utility of these indicators in various biological contexts.

Main Methods:

• Development of Förster resonance energy transfer (FRET)-based indicators (KIRIN1, KIRIN1-GR) using a bacterial K+ binding protein (Kbp).
• Construction of a single fluorescent protein-based indicator (GINKO1) by inserting Kbp into enhanced green fluorescent protein (EGFP).
• Application of indicators for in vitro and live-cell imaging of K+ concentrations and dynamics.

Main Results:

• KIRIN1 and KIRIN1-GR successfully detected K+ at physiologically relevant concentrations.
• KIRIN1 enabled imaging of cytosolic K+ depletion and neuronal K+ dynamics.
• GINKO1 facilitated dual-color imaging of K+ and Ca2+ in neurons and glial cells.

Conclusions:

• KIRIN1 and GINKO1 are effective tools for imaging intracellular K+ dynamics.
• These indicators offer new possibilities for studying cellular physiology and neuroscience.
• The developed indicators are suitable for detecting K+ in diverse cellular environments.