title: Active release of pneumolysin prepores and pores by mammalian cells undergoing a Streptococcus pneumoniae attack.
abstract: Streptococcus pneumoniae is a potent human pathogen. Its pore-forming exotoxin pneumolysin is instrumental for breaching the host's epithelial barrier and for the incapacitation of the immune system.
  
  
  
  Using a combination of life imaging and cryo-electron microscopy we show that pneumolysin, released by cultured bacteria, is capable of permeabilizing the plasmalemma of host cells. However, such permeabilization does not lead to cell lysis since pneumolysin is actively removed by the host cells. The process of pore elimination starts with the formation of pore-bearing plasmalemmal nanotubes and proceeds by the shedding of pores that are embedded in the membrane of released microvesicles. Pneumolysin prepores are likewise removed. The protein composition of the toxin-induced microvesicles, assessed by mass spectrometry, is suggestive of a Ca(2+)-triggered mechanism encompassing the proteins of the annexin family and members of the endosomal sorting complex required for transport (ESCRT) complex.
  
  
  
  S. pneumoniae releases sufficient amounts of pneumolysin to perforate the plasmalemma of host cells, however, the immediate cell lysis, which is frequently reported as a result of treatment with purified and artificially concentrated toxin, appears to be an unlikely event in vivo since the toxin pores are efficiently eliminated by microvesicle shedding. Therefore the dysregulation of cellular homeostasis occurring as a result of transient pore formation/elimination should be held responsible for the damaging toxin action.
  
  
  
  We have achieved a comprehensive view of a general plasma membrane repair mechanism after injury by a major bacterial toxin.
authors.affiliation: Institute of Anatomy, University of Bern, Baltzerstrasse 2, 3000 Bern 9, Switzerland.
authors.forename: Heidi
authors.initials: H
authors.lastname: Wolfmeier
authors.affiliation: Institute of Anatomy, University of Bern, Baltzerstrasse 2, 3000 Bern 9, Switzerland; Graduate School for Cellular and Biomedical Sciences, University of Bern, Freiestrasse 1, 3000 Bern 9, Switzerland.
authors.forename: Julika
authors.initials: J
authors.lastname: Radecke
authors.affiliation: Institute of Anatomy, University of Bern, Baltzerstrasse 2, 3000 Bern 9, Switzerland.
authors.forename: Roman
authors.initials: R
authors.lastname: Schoenauer
authors.affiliation: Institute of Anatomy, University of Bern, Baltzerstrasse 2, 3000 Bern 9, Switzerland.
authors.forename: René
authors.initials: R
authors.lastname: Koeffel
authors.affiliation: Institute of Anatomy, University of Bern, Baltzerstrasse 2, 3000 Bern 9, Switzerland.
authors.forename: Viktoria S
authors.initials: VS
authors.lastname: Babiychuk
authors.affiliation: Institute of Anatomy, University of Bern, Baltzerstrasse 2, 3000 Bern 9, Switzerland.
authors.forename: Patrick
authors.initials: P
authors.lastname: Drücker
authors.affiliation: Institute for Infectious Diseases, University of Bern, Friedbühlstrasse 51, Postfach, 3001, Bern, Switzerland.
authors.forename: Lucy J
authors.initials: LJ
authors.lastname: Hathaway
authors.affiliation: Institute of Microbiology and Infection, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdom.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Mitchell
authors.affiliation: Institute of Anatomy, University of Bern, Baltzerstrasse 2, 3000 Bern 9, Switzerland. Electronic address: benoit.zuber@ana.unibe.ch.
authors.forename: Benoît
authors.initials: B
authors.lastname: Zuber
authors.affiliation: Institute of Anatomy, University of Bern, Baltzerstrasse 2, 3000 Bern 9, Switzerland.
authors.forename: Annette
authors.initials: A
authors.lastname: Draeger
authors.affiliation: Institute of Anatomy, University of Bern, Baltzerstrasse 2, 3000 Bern 9, Switzerland. Electronic address: edik@ana.unibe.ch.
authors.forename: Eduard B
authors.initials: EB
authors.lastname: Babiychuk
mesh_terms: D001426:Bacterial Proteins / Q000494:pharmacology / Q000633:toxicity; D002462:Cell Membrane / Q000187:drug effects / Q000382:microbiology / Q000648:ultrastructure*; D002463:Cell Membrane Permeability; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D013296:Streptococcus pneumoniae / Q000472:pathogenicity*; D013301:Streptolysins / Q000494:pharmacology* / Q000633:toxicity
chemical_list: D001426:Bacterial Proteins; D013301:Streptolysins; C032290:plY protein, Streptococcus pneumoniae
keywords: Annexin; Bacterial toxin; Microvesicle; PLY; Plasmalemmal repair; Shedding