Biophysical Society Thematic Meeting | Ascona, Switzerland

Liposomes, Exosomes, and Virosomes: From Modeling Complex Membrane Processes to Medical Diagnostics and Drug Delivery

Poster Abstracts

44-POS Board 22 Directly Observing the Lipid-Dependent Self-Assembly and Pore-Forming Mechanism of the Cytolytic Toxin Listeriolysin O Estefania Mulvihill 1 , Katharina Van Pee 2 , Stefania Mari 1 , Ozkan Yildiz 2 , Daniel Müller 1 . 1 ETH Zürich, Basel, Switzerland, 2 Max-Planck Institut, Frankfurt, Germany. Listeriolysin O (LLO) is the major virulence factor of Listeria monocytogenes and a member of the cholesterol-dependent cytolysin (CDC) family. Gram-positive pathogenic bacteria produce water-soluble CDC monomers that bind cholesterol-dependent to the lipid membrane of the attacked cell or of the phagosome, oligomerize and insert into the membrane to form transmembrane pores. Although different models have been proposed to explain how CDCs bind and form pores into the membranes, this process is still not well understood. Using electron microscopy and time-lapse atomic force microscopy, we show that wild-type LLO binds to membranes, depending on the presence of cholesterol and phospholipids composition. LLO oligomerizes into arc- or slit-shaped assemblies, which merge into complete rings. With increasing cholesterol content of the membrane, the number of transmembrane pores increases. The dynamic fusion of arcs, slits and rings into larger rings and pores does not involve a height difference between prepore and pore. Our results reveal new insights into the pore-forming mechanism and introduce a dynamic model of pore formation by LLO.

87