title: Changes in astrocyte shape induced by sublytic concentrations of the cholesterol-dependent cytolysin pneumolysin still require pore-forming capacity.
abstract: Streptococcus pneumoniae is a common pathogen that causes various infections, such as sepsis and meningitis. A major pathogenic factor of S. pneumoniae is the cholesterol-dependent cytolysin, pneumolysin. It produces cell lysis at high concentrations and apoptosis at lower concentrations. We have shown that sublytic amounts of pneumolysin induce small GTPase-dependent actin cytoskeleton reorganization and microtubule stabilization in human neuroblastoma cells that are manifested by cell retraction and changes in cell shape. In this study, we utilized a live imaging approach to analyze the role of pneumolysin's pore-forming capacity in the actin-dependent cell shape changes in primary astrocytes. After the initial challenge with the wild-type toxin, a permeabilized cell population was rapidly established within 20-40 minutes. After the initial rapid permeabilization, the size of the permeabilized population remained unchanged and reached a plateau. Thus, we analyzed the non-permeabilized (non-lytic) population, which demonstrated retraction and shape changes that were inhibited by actin depolymerization. Despite the non-lytic nature of pneumolysin treatment, the toxin's lytic capacity remained critical for the initiation of cell shape changes. The non-lytic pneumolysin mutants W433F-pneumolysin and delta6-pneumolysin, which bind the cell membrane with affinities similar to that of the wild-type toxin, were not able to induce shape changes. The initiation of cell shape changes and cell retraction by the wild-type toxin were independent of calcium and sodium influx and membrane depolarization, which are known to occur following cellular challenge and suggested to result from the ion channel-like properties of the pneumolysin pores. Excluding the major pore-related phenomena as the initiation mechanism of cell shape changes, the existence of a more complex relationship between the pore-forming capacity of pneumolysin and the actin cytoskeleton reorganization is suggested.
authors: DFG Membrane, Cytoskeleton Interaction Group, Institute of Pharmacology and Toxicology & Rudolf Virchow Center for Experimental Medicine, University of Würzburg, Versbacherstr. 9, 97078 Würzburg, Germany. foertsch@toxi.uni-wuerzburg.de
authors: Christina
authors: C
authors: Förtsch
authors: Sabrina
authors: S
authors: Hupp
authors: Jiangtao
authors: J
authors: Ma
authors: Timothy J
authors: TJ
authors: Mitchell
authors: Elke
authors: E
authors: Maier
authors: Roland
authors: R
authors: Benz
authors: Asparouh I
authors: AI
authors: Iliev
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000187:drug effects* / Q000473:pathology; D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects* / Q000473:pathology; D002463:Cell Membrane Permeability / Q000187:drug effects; D048430:Cell Shape / Q000187:drug effects*; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D018920:Coculture Techniques; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000235:genetics; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D016062:Porosity; D051381:Rats; D017207:Rats, Sprague-Dawley; D013050:Spectrometry, Fluorescence; D013296:Streptococcus pneumoniae / Q000378:metabolism* / Q000472:pathogenicity; D013301:Streptolysins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology*; D037521:Virulence Factors / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D013301:Streptolysins; D037521:Virulence Factors; C032290:plY protein, Streptococcus pneumoniae; D002784:Cholesterol