Flotillin scaffold activity contributes to type VII secretion system assembly in Staphylococcus aureus

PLoS Pathog. 2017 Nov 22;13(11):e1006728. doi: 10.1371/journal.ppat.1006728. eCollection 2017 Nov.

Abstract

Scaffold proteins are ubiquitous chaperones that promote efficient interactions between partners of multi-enzymatic protein complexes; although they are well studied in eukaryotes, their role in prokaryotic systems is poorly understood. Bacterial membranes have functional membrane microdomains (FMM), a structure homologous to eukaryotic lipid rafts. Similar to their eukaryotic counterparts, bacterial FMM harbor a scaffold protein termed flotillin that is thought to promote interactions between proteins spatially confined to the FMM. Here we used biochemical approaches to define the scaffold activity of the flotillin homolog FloA of the human pathogen Staphylococcus aureus, using assembly of interacting protein partners of the type VII secretion system (T7SS) as a case study. Staphylococcus aureus cells that lacked FloA showed reduced T7SS function, and thus reduced secretion of T7SS-related effectors, probably due to the supporting scaffold activity of flotillin. We found that the presence of flotillin mediates intermolecular interactions of T7SS proteins. We tested several small molecules that interfere with flotillin scaffold activity, which perturbed T7SS activity in vitro and in vivo. Our results suggest that flotillin assists in the assembly of S. aureus membrane components that participate in infection and influences the infective potential of this pathogen.

MeSH terms

  • Bacillus subtilis / metabolism
  • Bacterial Proteins / metabolism
  • Gene Expression Regulation, Bacterial
  • Humans
  • Membrane Microdomains / metabolism
  • Membrane Proteins / metabolism*
  • Staphylococcal Infections / metabolism*
  • Staphylococcus aureus*
  • Type VII Secretion Systems / metabolism*

Substances

  • Bacterial Proteins
  • Membrane Proteins
  • Type VII Secretion Systems
  • flotillins

Grants and funding

BMS was supported by a grant of the German Excellence Initiative to the Graduate School of Life Sciences of the University of Würzburg. This work was funded by European Research Council ERC335568 (European Union) and Ministerio de Economía y Competitividad BFU2014-55601P. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.