Lipid nanopores can form a stable, ion channel-like conduction pathway in cell membrane

Cell permeabilization by electric pulses (EPs), or electroporation, has been well established as a tool to indiscriminately increase membrane flows of water solutes down the concentration and voltage gradients. However, we found that EPs of nanosecond duration (nsEPs) trigger formation of voltage-sensitive and inward-rectifying membrane pores. NsEP-treated cells remain mostly impermeable to propidium, suggesting that the maximum pore size is similar to 1 nm. The ion-channel-like properties of nsEP-opened nanopores vanish if they break into larger, propidium-permeable conventional pores. However, nanopores can be stable for many minutes and significantly impact cell electrolyte and water balance. Multiple nsEPs cause fast cell swelling and blebbing, whereas opening of larger pores with digitonin abolishes swelling and causes blebs to implode. The lipid nature of nsEP-opened nanopores is confirmed by fast externalization of phosphatidylserine residues. Nanopores constitute a previously unexplored ion transport Pathway that supplements classic ion channels but is distinctly different from them. (C) 2009 Elsevier Inc. All rights reserved.