Intracellular compartmentalization of potassium

Area of Science:

• Biochemistry and Biophysics
• Cellular Physiology

Background:

• Evidence suggests potassium ions (K+) are compartmentalized within cells, but this has been indirectly demonstrated.
• Various techniques, including intracellular electrode measurements, radioisotope studies (42K), and 39K nuclear magnetic resonance (NMR), support intracellular K+ compartmentalization.

Purpose of the Study:

• To review the diverse indirect evidence supporting intracellular potassium compartmentalization.
• To discuss the potential (patho)physiological significance of K+ compartmentalization.
• To highlight the utility of 39K NMR in further exploring K+ compartmentalization.

Main Methods:

• Review of existing literature employing intracellular electrode measurements.
• Analysis of studies utilizing 42K radioisotope tracers.
• Examination of data from 39K nuclear magnetic resonance (NMR) spectroscopy.
• Consideration of experiments using rubidium (Rb+) to probe K+ binding sites.

Main Results:

• Diverse indirect evidence supports intracellular potassium compartmentalization.
• Rubidium studies provide strong evidence by demonstrating shifts in K+ between NMR-distinguishable sites.
• 39K NMR shows apparent magnetic field dependence, offering a novel approach to study compartmentalization.

Conclusions:

• Intracellular potassium compartmentalization is supported by multiple indirect lines of evidence.
• Compartmentalization may be crucial for regulating intracellular K+ activity, impacting enzyme function, protein synthesis, and cell growth.
• Potassium compartmentalization may contribute to cellular homeostasis following potassium overload.
• 39K NMR presents a promising avenue for further investigation into the mechanisms and significance of intracellular potassium compartmentalization.