title: Rapid microtubule bundling and stabilization by the Streptococcus pneumoniae neurotoxin pneumolysin in a cholesterol-dependent, non-lytic and Src-kinase dependent manner inhibits intracellular trafficking.
abstract: Streptococcus pneumoniae is the most frequent cause of bacterial meningitis, leading to permanent neurological damage in 30% and lethal outcome in 25% of patients. The cholesterol-dependent cytolysin pneumolysin is a major virulence factor of S. pneumoniae. It produces rapid cell lysis at higher concentrations or apoptosis at lower concentrations. Here, we show that sublytic amounts of pneumolysin produce rapid bundling and increased acetylation of microtubules (signs of excessive microtubule stabilization) in various types of cells--neuroblastoma cells, fibroblasts and primary astrocytes. The bundling started perinuclearly and extended peripherally towards the membrane. The effect was not connected to pneumolysin's capacity to mediate calcium influx, macropore formation, apoptosis, or RhoA and Rac1 activation. Cellular cholesterol depletion and neutralization of the toxin by pre-incubation with cholesterol completely inhibited the microtubule phenotype. Pharmacological inhibition of Src-family kinases diminished microtubule bundling, suggesting their involvement in the process. The relevance of microtubule stabilization to meningitis was confirmed in an experimental pneumococcal meningitis animal model, where increased acetylation was observed. Live imaging experiments demonstrated a decrease in organelle motility after toxin challenge in a manner comparable to the microtubule-stabilizing agent taxol, thus proposing a possible pathogenic mechanism that might contribute to the CNS damage in pneumococcal meningitis.
authors.affiliation: Laboratory for Molecular and Cellular Systems, Department of Neuro- and Sensory Physiology, Instutute for Physiology and Pathophysiology, University Medicine Göttingen, 37073 Göttingen, Germany. iliev@toxi.uni-wuerzburg.de
authors.forename: Asparouh I
authors.initials: AI
authors.lastname: Iliev
authors.forename: Jasmin Roya
authors.initials: JR
authors.lastname: Djannatian
authors.forename: Felipe
authors.initials: F
authors.lastname: Opazo
authors.forename: Joachim
authors.initials: J
authors.lastname: Gerber
authors.forename: Roland
authors.initials: R
authors.lastname: Nau
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Mitchell
authors.forename: Fred S
authors.initials: FS
authors.lastname: Wouters
mesh_terms: D000107:Acetylation; D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism*; D016466:CHO Cells; D045744:Cell Line, Tumor; D002784:Cholesterol / Q000378:metabolism*; D006224:Cricetinae; D003412:Cricetulus; D006801:Humans; D051379:Mice; D008870:Microtubules / Q000378:metabolism*; D017397:Prefrontal Cortex / Q000382:microbiology; D011817:Rabbits; D013296:Streptococcus pneumoniae / Q000378:metabolism* / Q000472:pathogenicity; D013301:Streptolysins / Q000378:metabolism*; D014404:Tubulin / Q000378:metabolism; D037521:Virulence Factors / Q000378:metabolism; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D013301:Streptolysins; D014404:Tubulin; D037521:Virulence Factors; C032290:plY protein, Streptococcus pneumoniae; D002784:Cholesterol; D019061:src-Family Kinases