Membrane perforation by the pore-forming toxin pneumolysin

Abstract

Pneumolysin (PLY), a major virulence factor of Streptococcus pneumoniae, perforates cholesterol-rich lipid membranes. PLY protomers oligomerize as rings on the membrane and then undergo a structural transition that triggers the formation of membrane pores. Structures of PLY rings in prepore and pore conformations define the beginning and end of this transition, but the detailed mechanism of pore formation remains unclear. With atomistic and coarse-grained molecular dynamics simulations, we resolve key steps during PLY pore formation. Our simulations confirm critical PLY membrane-binding sites identified previously by mutagenesis. The transmembrane β-hairpins of the PLY pore conformation are stable only for oligomers, forming a curtain-like membrane-spanning β-sheet. Its hydrophilic inner face draws water into the protein–lipid interface, forcing lipids to recede. For PLY rings, this zone of lipid clearance expands into a cylindrical membrane pore. The lipid plug caught inside the PLY ring can escape by lipid efflux via the lower leaflet. If this path is too slow or blocked, the pore opens by membrane buckling, driven by the line tension acting on the detached rim of the lipid plug. Interestingly, PLY rings are just wide enough for the plug to buckle spontaneously in mammalian membranes. In a survey of electron cryo-microscopy (cryo-EM) and atomic force microscopy images, we identify key intermediates along both the efflux and buckling pathways to pore formation, as seen in the simulations.

Evaluation of the Potency of Two Pyolysin-Derived Recombinant Proteins as Vaccine Candidates of Trueperella Pyogenes in a Mouse Model: Pyolysin Oligomerization and Structural Change Affect the Efficacy of Pyolysin-Based Vaccines

“…As a member of the CDC family, PLO can bind and form pores on cholesterol-containing membranes. In pore formation, CDC monomers assemble into large oligomers and undergo an extensive structural change [18]. This oligomerization and structural change might have led to the loss of some conformational epitopes of the PLO monomer molecule and the decrease of accessibility of some linear epitopes in PLO monomers.…”

“…CDCs are expressed as soluble monomers, which adhere to cholesterol-rich membranes by their D4, organize into closed rings as mediated by their D2 and D3, and form a prepore membrane protein complex. This event results in an extensive structural remodeling in which the D3 converses to transmembrane hairpins, the D2 structurally collapses, and the CDC's prepore complex forms a large oligomeric β-barrel and perforates the plasma membrane [18]. The role of D1 in pore forming remains unclear; however, the replacement of some amino acids impairs the hemolytic activity of PLO molecules [19][20][21].…”

Mitochondrial DNA: A Key Regulator of Anti-Microbial Innate Immunity

“…Furthermore, pneumolysin, a pore-forming toxin is the key virulence factor of Gram-positive bacteria (Streptococcus pneumoniae) and is considered to influence alveolar epithelial cells to stimulate the immune system by the release of danger-associated molecular patterns [136,137]. Nerlich et al [138] demonstrated that bacterially released pore-forming toxin pneumolysin could remarkably alter the ATP homeostasis of cells and lead to morphologic changes of mitochondria in alveolar epithelial cells of human in vitro.…”

Opening the OPK Assay Gatekeeper: Harnessing Multi-Modal Protection by Pneumococcal Vaccines

“…Pneumolysin is a pore-forming toxin produced by all clinical strains of S. pneumoniae [44]. It is thought to be responsible for much of the inflammation observed during pneumonia and the organ damage observed during disseminated infections.…”