Neuronal death in pneumococcal meningitis is triggered by pneumolysin and RrgA interactions with β-actin

PLoS Pathog. 2021 Mar 24;17(3):e1009432. doi: 10.1371/journal.ppat.1009432. eCollection 2021 Mar.

Abstract

Neuronal damage is a major consequence of bacterial meningitis, but little is known about mechanisms of bacterial interaction with neurons leading to neuronal cell death. Streptococcus pneumoniae (pneumococcus) is a leading cause of bacterial meningitis and many survivors develop neurological sequelae after the acute infection has resolved, possibly due to neuronal damage. Here, we studied mechanisms for pneumococcal interactions with neurons. Using human primary neurons, pull-down experiments and mass spectrometry, we show that pneumococci interact with the cytoskeleton protein β-actin through the pilus-1 adhesin RrgA and the cytotoxin pneumolysin (Ply), thereby promoting adhesion and invasion of neurons, and neuronal death. Using our bacteremia-derived meningitis mouse model, we observe that RrgA- and Ply-expressing pneumococci co-localize with neuronal β-actin. Using purified proteins, we show that Ply, through its cholesterol-binding domain 4, interacts with the neuronal plasma membrane, thereby increasing the exposure on the outer surface of β-actin filaments, leading to more β-actin binding sites available for RrgA binding, and thus enhanced pneumococcal interactions with neurons. Pneumococcal infection promotes neuronal death possibly due to increased intracellular Ca2+ levels depending on presence of Ply, as well as on actin cytoskeleton disassembly. STED super-resolution microscopy showed disruption of β-actin filaments in neurons infected with pneumococci expressing RrgA and Ply. Finally, neuronal death caused by pneumococcal infection could be inhibited using antibodies against β-actin. The generated data potentially helps explaining mechanisms for why pneumococci frequently cause neurological sequelae.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism*
  • Animals
  • Bacterial Proteins / metabolism
  • Cell Death / physiology
  • Fimbriae Proteins / metabolism*
  • Humans
  • Meningitis, Pneumococcal / metabolism
  • Meningitis, Pneumococcal / pathology*
  • Mice
  • Neurons / metabolism
  • Neurons / pathology*
  • Streptolysins / metabolism*
  • Virulence Factors / metabolism*

Substances

  • Actins
  • Bacterial Proteins
  • RrgA protein, Streptococcus pneumoniae
  • Streptolysins
  • Virulence Factors
  • plY protein, Streptococcus pneumoniae
  • Fimbriae Proteins

Grants and funding

We thank all the major funding that has supported this study: Petrus and Augusta Hedlund Foundation, Jeansson Foundation, Åke Wiberg Foundation, SFO StratNeuro Start-up grant, Clas Groschinsky Foundation, Karolinska Institutet Faculty Board, and the Karolinska Institutet Research Foundation Grants to FI, as well as the Swedish Research Council, the Knut and Alice Wallenberg Foundation, Stockholm County Council, and the Swedish foundation for Strategic research (SSF) to BHN. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.