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Published on: April 4, 2018
The single D380 amino acid substitution increases pneumolysin cytotoxicity toward neuronal cells
Simona Serra1, Vittorio Iannotti1, Margherita Ferrante1
1Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
Abstract:
Bacterial meningitis, frequently caused by Streptococcus pneumoniae (pneumococcus), represents a substantial global health threat leading to long-term neurological disorders. This study focused on the cholesterol-binding toxin pneumolysin (PLY) released by pneumococci, specifically examining clinical isolates from patients with meningitis and comparing them to the PLY-reference S. pneumoniae strain D39. Clinical isolates exhibit enhanced PLY release, likely due to a significantly higher expression of the autolysin LytA. Notably, the same single amino acid (aa) D380 substitution in the PLY D4 domain present in all clinical isolates significantly enhances cholesterol binding, pore-forming activity, and cytotoxicity toward SH-SY5Y-derived neuronal cells. Scanning electron microscopy of human neuronal cells and patch clamp electrophysiological recordings on mouse brain slices confirm the enhanced neurotoxicity of the PLY variant carrying the single aa substitution. This study highlights how a single aa modification enormously alters PLY cytotoxic potential, emphasizing the importance of PLY as a major cause of the neurological sequelae associated with pneumococcal meningitis.
Insights
A single amino acid change in pneumolysin (PLY), a toxin from Streptococcus pneumoniae, dramatically increases its neurotoxicity. This enhanced PLY contributes significantly to neurological damage in bacterial meningitis.
Area of Science:
- Neuroscience
- Microbiology
- Toxicology
Background:
- Bacterial meningitis, often caused by Streptococcus pneumoniae, is a major cause of neurological disorders.
- Pneumolysin (PLY) is a key toxin released by S. pneumoniae, implicated in disease pathogenesis.
Purpose of the Study:
- To investigate the role of pneumolysin (PLY) variants from clinical meningitis isolates.
- To compare the neurotoxic potential of PLY from clinical isolates versus a reference strain.
Main Methods:
- Analysis of PLY release and LytA expression in clinical S. pneumoniae isolates.
- Characterization of a specific D380 amino acid substitution in the PLY D4 domain.
- Assessment of cholesterol binding, pore-forming activity, and cytotoxicity on neuronal cells.
- Electrophysiological recordings and electron microscopy to confirm neurotoxicity.
Main Results:
- Clinical meningitis isolates showed increased PLY release, linked to higher LytA expression.
- A single D380 substitution in PLY's D4 domain enhanced cholesterol binding and pore formation.
- This PLY variant exhibited significantly increased cytotoxicity toward human neuronal cells.
- Neurotoxicity was confirmed via scanning electron microscopy and patch clamp recordings.
Conclusions:
- A single amino acid substitution in PLY profoundly enhances its cytotoxic potential.
- Enhanced PLY neurotoxicity is a key factor in neurological sequelae of pneumococcal meningitis.
- Targeting PLY activity may mitigate meningitis-related neurological damage.
