Modelling mechanosensitivity in membranes: effects of lateral tension on ionic pores in a microcystin toxin-containing membrane

Lipid bilayers of diphytanoyl lecithin (DPhL) in which a cyanobacterial toxin, microcystin-LR (MC-LR) was incorporated, were found to be a convenient model of natural mechanosensitive membranes. The effects of pressure difference, leading to lateral membrane tension, on artificial membranes formed on the tips of glass micropipettes were investigated using patch-clamp methodology. Emplacement of MC-LR from the bathing solution was enhanced by transmembrane voltage and/or pressure difference. MC-LR pores could be recorded over a wide voltage range, their opening probability being first increased and then reduced at high membrane potential. The pores exhibited several open pore conductance levels, the higher conductance states being more probable at greater lateral tensions. Ion gradient experiments established that the MC-LR pores are cation selective, but discriminate only weakly between K and Na. These results suggest that a lipid liquid crystal matrix containing monomers of multimeric pore-forming molecules could be used as a mechanical sensor and molecular switch.