PSMNano · Probing the fibrillation of Staphylococcal amyloids and their interactions with Membranes at the Nanoscale

Probing the fibrillation of Staphylococcal amyloids and their interactions with Membranes at the Nanoscale

Staphylococcus aureus is a human commensal of the microbiota and the human epithelia, which can turn into an opportunistic pathogen, eventually causing life-threatening diseases. Due to its key role in nosocomial infections and its resistance to many antibiotics, S. aureus constitutes major political and clinical issues worldwide. To elicit less antibioresistance, current drug development strategies focus on targeting virulence determinants of S. aureus, and require, first and foremost, a comprehensive understanding of the molecular mechanisms S. aureus has developed to passively or actively evade host elimination. In this context, S. aureus virulence has been shown to critically depend on the production of the phenol-soluble modulins α3 (PSMα3) peptides, that have recently drawn much attention due to their key roles in invasion and infection. Overproduced by multiresistant strains, those amphipathic peptides not only exhibit cytolytic activities towards human cells but also eventually trigger pro-inflammation processes in a receptor (FPR2)-dependent manner. Such diverse functions rely on specific mechanisms of interaction, either recognition and/or perturbation, with cell membranes. Interestingly, PSMα3 can self-assemble into insoluble fibrils, characterized by the unique cross-α structure, reminiscent of the cross-β scaffold of pathogenic amyloids studied in light of neurodegenerative disorders. Based on recent controversial data, the cross-α fibrillation would be required for PSMα3 to exert its functions. Yet, most of the current knowledge arises from ensemble techniques, only providing average behavior of all PSMα3 entities formed along the fibrillation, and thus partially ignoring the complex interplay between the structural polymorphism of PSMα3, and their interactions with cells. This project thus aims at providing insights into the structure-function relationship of the virulent factors PSMα3, by investigating, at the cellular and molecular levels, their underestimated dynamic interactions with cell membranes, the first key steps towards their physiological functions in S. aureus. To reach this objective, Combination of in vitro and in cellulo experiments, based on Atomic Force Microscopy (AFM)-related techniques, combined with complementary biophysical approaches, will be performed to: (1) unravel the fibrillation kinetics and structures of PSMα3 interacting with membranes, (2) decipher the mechanisms governing the interaction of PSMα3 and membranes, and (3) unveil the receptor-mediated processes turning PSMα3 into proinflammatory agents.

Data: CORDIS, © European Union