Cholesterol promotes Cytolysin A activity by stabilizing the intermediates during pore formation

Pore-forming toxins (PFTs) form nanoscale pores across target membranes causing cell death. Cytolysin A (ClyA) from Escherichia coli is a prototypical α-helical toxin that contributes to cytolytic phenotype of several pathogenic strains. It is produced as a monomer and, upon membrane exposure, under...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2018-07, Vol.115 (31), p.E7323-E7330
Main Authors: Sathyanarayana, Pradeep, Maurya, Satyaghosh, Behera, Amit, Ravichandran, Monisha, Visweswariah, Sandhya S., Ayappa, K. Ganapathy, Roy, Rahul
Format: Article
Language:English
Subjects:
Assembly
Biological membranes
Biological properties
Biological Sciences
Biophysics
Cell death
Cell Membrane - drug effects
Cell membranes
Cholesterol
Cholesterol - chemistry
ClyA protein
Detergents
E coli
Escherichia coli Proteins - chemistry
Escherichia coli Proteins - toxicity
Forming
Hemolysin Proteins - chemistry
Hemolysin Proteins - toxicity
Interfaces
Intermediates
Lipid Bilayers - chemistry
Membrane proteins
Membranes
Molecular dynamics
Molecular Dynamics Simulation
Oligomerization
Phenotypes
Phospholipids
Physicochemical properties
PNAS Plus
Pore formation
Protein Multimerization
Proteins
Toxins
α-Toxin
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Summary:Pore-forming toxins (PFTs) form nanoscale pores across target membranes causing cell death. Cytolysin A (ClyA) from Escherichia coli is a prototypical α-helical toxin that contributes to cytolytic phenotype of several pathogenic strains. It is produced as a monomer and, upon membrane exposure, undergoes conformational changes and finally oligomerizes to form a dodecameric pore, thereby causing ion imbalance and finally cell death. However, our current understanding of this assembly process is limited to studies in detergents, which do not capture the physicochemical properties of biological membranes. Here, using single-molecule imaging and molecular dynamics simulations, we study the ClyA assembly pathway on phospholipid bilayers. We report that cholesterol stimulates pore formation, not by enhancing initial ClyA binding to the membrane but by selectively stabilizing a protomer-like conformation. This was mediated by specific interactions by cholesterol-interacting residues in the N-terminal helix. Additionally, cholesterol stabilized the oligomeric structure using bridging interactions in the protomer–protomer interfaces, thereby resulting in enhanced ClyA oligomerization. This dual stabilization of distinct intermediates by cholesterol suggests a possible molecular mechanism by which ClyA achieves selective membrane rupture of eukaryotic cell membranes. Topological similarity to eukaryotic membrane proteins suggests evolution of a bacterial α-toxin to adopt eukaryotic motifs for its activation. Broad mechanistic correspondence between pore-forming toxins hints at a wider prevalence of similar protein membrane insertion mechanisms.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1721228115