Intracellular ATP does not inhibit Slo2.1 K+ channels

Area of Science:

• Molecular biology
• Ion channel physiology
• Cellular electrophysiology

Background:

• Slo2.1 K(+) channels are crucial for cellular resting potential stabilization.
• Previous studies presented conflicting data regarding the inhibitory effect of intracellular ATP on Slo2.1 channels.
• Re-evaluation of ATP's influence on human Slo2.1 channels is necessary.

Purpose of the Study:

• To definitively determine the effect of intracellular ATP on human Slo2.1 channel activity.
• To resolve discrepancies in the literature concerning ATP regulation of Slo2.1 channels.

Main Methods:

• Direct electrophysiological recordings from excised inside-out macropatches of Xenopus oocytes expressing human Slo2.1 channels.
• Whole-cell patch-clamp recordings from Xenopus oocytes with depleted intracellular ATP levels induced by NaN3.
• Site-directed mutagenesis of a conserved residue in the putative ATP-binding site of Slo2.1 channels.

Main Results:

• Application of 5 mmol/L ATP to excised patches did not inhibit niflumic acid-activated Slo2.1 currents.
• Depletion of intracellular ATP using NaN3 activated KATP channels but did not affect wild-type or mutant Slo2.1 channel currents.
• Mutation of the putative ATP-binding site did not alter Slo2.1 channel activity.

Conclusions:

• Human Slo2.1 channels are not inhibited by physiological levels of intracellular ATP.
• Intracellular ATP concentration does not modulate Slo2.1 channel function.
• These findings clarify the regulatory mechanisms of Slo2.1 channels in cellular physiology.