Activation of hTREK-1 by polyunsaturated fatty acids does not only involve membrane tension

TREK-1 is a mechanosensitive channel also activated by polyunsaturated fatty acids (PUFAs). In this study, we compared the effect of multiple fatty acids and ML402. First, we showed a variable TREK-1 activation by PUFAs related to the variable constitutive activity of TREK-1. Then, we observed no correlation between TREK-1 activation and acyl chain length or number of double bonds suggesting that the bilayer-couple hypothesis cannot explain by itself the activation of TREK-1 by PUFAs. The membrane fluidity measurement is not modified by PUFAs at 10 {micro}M. The spectral shift analysis in TREK-1-enriched microsomes indicates a KD,TREK1 at 44 {micro}M of C22:6 n-3. PUFAs display the same activation and reversible kinetics than the direct activator ML402 and activate TREK-1 in both whole-cell and inside-out configurations of patch-clamp suggesting that the binding site of PUFAs is accessible from both sides of the membrane, as for ML402. Finally, we proposed a two steps mechanism for TREK-1 activation by PUFAs: first, insertion into the membrane, without fluidity or curvature modifications, and then interaction with TREK-1 channel to open it.