Characterisation of Ca(2+)-dependent inwardly rectifying K+ currents in HeLa cells

Area of Science:

• Cellular electrophysiology
• Ion channel biophysics
• Molecular pharmacology

Background:

• Potassium (K+) currents play crucial roles in cellular function.
• Understanding K+ current characteristics in cell lines like HeLa is vital for basic research.
• Modulation of ion currents by intracellular and extracellular factors requires detailed investigation.

Purpose of the Study:

• To characterize the properties of K+ currents in HeLa cells.
• To investigate the ionic selectivity and voltage dependence of these currents.
• To identify modulators and blockers of K+ currents in HeLa cells.

Main Methods:

• Whole-cell patch-clamp technique was employed to record K+ currents.
• Ionic gradients were manipulated to assess K+ selectivity and permeability.
• Pharmacological agents, including scorpion toxins and other blockers, were used to probe current mechanisms.

Main Results:

• HeLa cells exhibit large inwardly rectifying K+ currents, largely independent of voltage.
• K+ conductance is highly sensitive to intracellular free calcium concentration (KD = 70 nmol/l).
• Charybdotoxin, a component of Leiurus quinquestriatus venom, effectively blocks these K+ currents in a voltage-dependent manner.

Conclusions:

• HeLa cells possess a distinct inwardly rectifying K+ current modulated by intracellular calcium.
• This current displays specific permeability and conductance properties to various monovalent cations.
• Charybdotoxin is a potent and voltage-dependent blocker, elucidating the effects of scorpion venom on these currents.