Cyclodextrins increase membrane tension and are universal activators of mechanosensitive channels

Abstract

The bacterial mechanosensitive channel of small conductance, MscS, has been extensively studied to understand how mechanical forces are converted into the conformational changes that underlie mechanosensitive (MS) channel gating. We showed that lipid removal by {beta}-cyclodextrin can mimic membrane tension. Here, we show that all cyclodextrins (CDs) can activate reconstituted E. coli MscS, that MscS activation by CDs depends on CD-mediated lipid removal, and that the CD amount required to gate MscS scales with the channels sensitivity to membrane tension. CD-mediated lipid removal ultimately causes MscS desensitization, which we show is affected by the lipid environment. CDs can also activate the structurally unrelated MscL. While many MS channels respond to membrane forces, generalized by the force-from-lipids principle, their different molecular architectures suggest that they use unique ways to convert mechanical forces into conformational changes. CDs emerge as a universal tool for the structural and functional characterization of unrelated MS channels.