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Updated: Dec 31, 2025
Quantifying the Cytotoxicity of Staphylococcus aureus Against Human Polymorphonuclear Leukocytes
Published on: January 3, 2020
Staphylococcus aureus PSMα3 Cross-α Fibril Polymorphism and Determinants of Cytotoxicity
Einav Tayeb-Fligelman1, Nir Salinas1, Orly Tabachnikov1
1Department of Biology, Technion-Israel Institute of Technology, Haifa 3200003, Israel.
Abstract:
The phenol-soluble modulin (PSM) peptide family, secreted by Staphylococcus aureus, performs various virulence activities, some mediated by the formation of amyloid fibrils of diverse architectures. Specifically, PSMα1 and PSMα4 structure the S. aureus biofilm by assembling into robust cross-β amyloid fibrils. PSMα3, the most cytotoxic member of the family, assembles into cross-α fibrils in which α helices stack into tightly mated sheets, mimicking the cross-β architecture. Here we demonstrate that massive T cell deformation and death are linked with PSMα3 aggregation and co-localization with cell membranes. Our extensive mutagenesis analyses support the role of positive charges, and especially Lys17, in interactions with the membrane and suggest their regulation by inter- and intra-helical electrostatic interactions within the cross-α fibril. We hypothesize that PSMα3 cytotoxicity is governed by the ability to form cross-α fibrils and involves a dynamic process of co-aggregation with the cell membrane, rupturing it.
Insights
Phenol-soluble modulin alpha 3 (PSMα3) from Staphylococcus aureus forms unique cross-α amyloid fibrils. These fibrils aggregate with cell membranes, causing T cell deformation and death, revealing a novel mechanism of bacterial cytotoxicity.
Area of Science:
- Microbiology
- Biochemistry
- Cell Biology
Background:
- Staphylococcus aureus secretes phenol-soluble modulin (PSM) peptides involved in virulence.
- Some PSMs form amyloid fibrils, including cross-β structures by PSMα1 and PSMα4, which organize S. aureus biofilms.
- PSMα3, a highly cytotoxic PSM, forms distinct cross-α amyloid fibrils.
Purpose of the Study:
- To investigate the mechanism underlying PSMα3-mediated cytotoxicity.
- To explore the structural basis of PSMα3 aggregation and its interaction with cell membranes.
- To elucidate the role of specific amino acid residues in PSMα3's cytotoxic activity.
Main Methods:
- Extensive mutagenesis of the PSMα3 peptide.
- Analysis of PSMα3 aggregation into cross-α fibrils.
- Microscopy to observe PSMα3 co-localization with cell membranes.
- Assays to measure T cell deformation and death.
Main Results:
- PSMα3 aggregation and co-localization with cell membranes correlate with T cell deformation and death.
- Mutagenesis studies identified positive charges, particularly Lys17, as crucial for membrane interaction.
- Electrostatic interactions within the cross-α fibril regulate these membrane-binding properties.
Conclusions:
- PSMα3 cytotoxicity is dependent on its ability to form cross-α fibrils.
- The mechanism involves dynamic co-aggregation with the cell membrane, leading to membrane rupture.
- Lys17 and electrostatic interactions are key determinants of PSMα3's membrane-disrupting activity.
