Quantifying pressure and ultrasound activation of the mechanosensitive K+ channel TRAAK.

Abstract

The study of mechanosensitive ion channels depends upon electrophysiological recordings coupled with mechanical stimulation by cell poking, pillar arrays, or pressure application via to excised membrane patches. In each of these environments, mechanical energy is deposited into the membrane and causes the membrane to stretch, inducing tension. Unlike other assays, pressure stimulation with simultaneous imaging of patched membranes permits tension, the relevant gating stimulus for most mechanosensitive channels, to be calculated. Here, we quantify the mechanical tuning of the mechanosensitive K+ channel TRAAK and compare it to the bacterial mechanosensitive channel MscS. We find TRAAK is activated at lower tension values and over a wider range of tension compared to MscS. We further show that ultrasound activates TRAAK and MscS in excised patches. Changes in membrane curvature induced by ultrasound or pressure stimulation resulted in the same degree of channel activation. This suggests ultrasound activation of mechanosensitive ion channels is due to increased membrane tension rather than alternative mechanisms posited for transfer of acoustic energy to channels.