The activity of the pore-forming toxin lysenin is regulated by crowding

Publisher's notice concerning Nacho L.B. Munguira, Alfonso Barbas and Ignacio Casuso 2019 NanotechnologyWe are issuing an Expression of Concern to raise awareness of a potential problem in this article.It has been brought to our attention that some of the data used in the study may be unsound. There is also an ongoing dispute regarding the authorship of this paper. These matters are currently under investigation. If required, the publication record will be corrected as soon as possible. (28 January 2020)The β pore-forming toxins (β-PFTs) are cytotoxic proteins produced as soluble monomers, which cluster and oligomerize at the membrane of the target host cells. Their initial oligomeric state, the prepore, is not cytotoxic. The β-PFTs undergo a large structural transition to a second oligomeric state, the pore, which pierces the membrane of the host cell and is cytotoxic. Data from electrophysiology and vesicle permeabilization experiments have suggested the possibility of a correlation between the transition rate from prepore state to pore state and the levels of local crowding in the cluster of β-PFT oligomers. Nevertheless, to this date, visualization and understanding at the molecular level are missing. We have addressed this issue using a panel of Atomic Force Microscopy (AFM) techniques and simulations. We describe the mechanism by which the rates of formation of the transmembrane pores correlate with the local levels of crowding for the β-PFT lysenin and discuss possible biological and medical implications.