Trek-2 Has An Asymmetrical Response To Force Changes In The Membrane

Perception of force is a key component in our sensation of touch, hearing and pain as well as in regulation of blood and osmotic pressures, but unlike the well-described nature of taste and odorant receptors and the photoreceptors in the eye, we have not yet a clear idea of how this sense operate at the molecular level. Fundamental to the concept is that force must be translated into electrical conductance, that is perceived by the nervous system, and we believe this translation occur through the action of mechanosensitive ion channels. Recently it has been demonstrated that eukaryotic mechanosensitive channels, just like their prokaryotic counterparts, directly sense force changes in the lipid bilayers, so now the important question is: how does membrane modulation couple to channel activity? To address this question we use purified mechanosensitive TREK-2 channels, which we reconstitute into planar lipid patches at a concentration that allow us to study channel activity at the single molecule level. We find that the reconstituted channels have a random orientation, and that we can clearly distinguish between the two possible orientations by analyzing electrophysiological characteristics as conductance and open dwell times. To investigate the sensitivity of the channels to mechanical modulation, we apply different degrees of negative or positive pressure to the patches, and analyze how such stimulations affect the activity of differently oriented channels. With this approach we can demonstrate that mechanical activation of TREK-2 depends on the direction of the pressure pulse, i.e. one orientation is activated only by negative pressure while the other orientation is activated only by positive pressure. We carefully suggest that these results demonstrate that TREK-2 channels are sensitive to the direction of membrane curvature. Furthermore we are in the process of deducing a kinetic model that describes TREK-2 activation by pressure.