Pathways for creation and annihilation of nanoscale biomembrane domains reveal alpha and beta-toxin nanopore formation processes

Abstract

Raft-like functional domains with putative sizes of 20–200 nm and which are evolving dynamically are believed to be the most crucial regions in cellular membranes which determine cell signaling and various functions of cells.

Correlated protein conformational states and membrane dynamics during attack by pore-forming toxins

“…3 were only obtained from the L d phase of the vesicles where the LLO predominantly binds (SI Appendix, Fig. S3 D-G), consistent with our recent study (8). The most probable D values were found to be slightly higher for LVs, while a significant reduction was observed for ULVs, compared with the pristine GUVs.…”

“…Understanding the mechanistic pathways for PFTs has relied largely on structural data gleaned from cryo-electron microscopy (cryo-EM) and X-ray crystallography, where detergents induce oligomerization to stabilize pore structures (5,6). Since CDCs and LLO in particular act by binding to membrane cholesterol, model lipid membranes have been used to ascertain the presence of prepore and pore structures with atomic force microscopy (AFM) (7)(8)(9)(10). The LLO pore states can exist either as partially oligomerized arcs or complete pores, with sizes ranging from 40 to 80 nm (9) and selective influx of dyes into giant unilamellar vesicles (GUVs) exposed to LLO confirm the presence of functional oligomeric intermediates (10).…”

Assessing the Extent of Structural and Dynamic Modulation of Membrane Lipids due to Pore Forming Toxins: Insights from Molecular Dynamics Simulations

“…Recent super-resolution stimulated emission depletion coupled with fluorescence correlation spectroscopy (STED-FCS) spectroscopy on supported lipid bilayers have been used to study the inherent dynamic heterogeneity and non-Brownian dynamics associated with lipids in the vicinity of the PFTs. 21,22 Indeed, increased fluidity away from the pore complex has been observed due to cholesterol depletion with LLO ( a cholesterol dependent cytolysin) binding, suggesting a more complex modulation mechanism in multicomponent membranes. 18 Advances in techniques such as neutron and X-ray scattering experiments can provide both lateral and in-plane variations in lipid order and dynamics at the atomic scale.…”

“…STED-FCS experiments with ClyA in three component membranes show that the binding of ClyA to sphingomyelin and cholesterol rich domains reduces phase segregation in these raft forming membranes. 21 Molecular dynamics simulations of transmembrane proteins in multicomponent membranes reveal segregation of specific lipid types to the protein surface needed for specific functions of the transmembrane domains. 25,71 It would be interesting to study the local compositional changes in the case of assembled PFTs which do not have any specific function other than membrane perforation.…”

“…[16][17][18][19][20] STED-FCS experiments capture a cross-over at smaller length scales (< 200 nm) from Brownian to non-Brownian dynamics with increasing cholesterol content in supported lipid bilayers exposed to LLO a cholesterol dependent cytolysin 18 as well as increased fluidization in three component raft forming membranes upon ClyA binding. 21 In a recent study with listeriolysin O, the dynamics of lipids on giant unilamellar vesicles were found to be intrinsically coupled to the state of the membrane bound protein. 22 The role of lipids and their interactions with transmembrane proteins have also been investigated using MD simulations.…”