LAUSR

The lipid composition of biological membranes modulates the acti vity of integral membrane proteins (Cantor, 1998; Andersen & Koeppe, 2007). This is particularly important for mechanosensiti v channels, regardless of their gating paradigm. Here we use the surf ace acti ve agent 2,2,2-trifluoroethanol (TFE) as a pharmacological tool to study the effect of surface tension perturbations on an array of bacterial and mammalian MS channels including MscL, Piezo1 and TREK-1. W e chose TFE (a general anaesthetic) due to the fact that its ef fect on the bacterial channel MscS has already been studied. In particular TFE facilitates MscS activation from the periplasmic side, while it abolishes MscS current from the cytoplasmic side (Akitak e et al., 2007; Nomuraet al., 2015). Here, we demonstrate that 2 % v/v TFE can also facilitate the acti vation of: MscL if TFE is added to either bilayer leaflet, Piezo1 only if added to the cytoplasmic side and TREK-1 only from the extracellular side. Our molecular dynamics simulations re vealed TFEincreases the surf ace tension and the first moment of the pressure profile mark edly and hence facilitates acti vation of MscL. Using our molecular dynamics, energetic analysis and collecti ve experimental data, we postulate there is a close relationship between MS channel shape and its acti va on mechanism by surface tension perturbations. The acti vation curve of MscL, which is a cylindrical protein, was shifted to the left (acti vated easier) upon addition of TFE from either side. MscS and TREK on the other hand, which are conical, were only facilitated from the e xtracellular side. The activation curve of Piezo1 was also shifted to left only when TFE was added to the cytoplasmic side. Gi ven surface acti ve drugs are adsorbed onto cell membranes, these findings provide a mechanistic understanding of their non-specific impact on the function of different membrane proteins, particularly MS ion channels.