%0 Journal Article %1 Iliev2007 %A Iliev, A. I. %A Djannatian, J. R. %A Nau, R. %A Mitchell, T. J. %A Wouters, F. S. %D 2007 %J Proc Natl Acad Sci U S A %K Actins/*metabolism Activation/drug Bacterial Calcium/metabolism Cell Cholesterol/*pharmacology Cytoplasmic Death/drug Enzyme Exchange Factors/metabolism Fibers/drug GTP-Binding Guanine Humans Nucleotide Phenotype Protein/*metabolism Proteins/pharmacology Pseudopodia/drug Shape/drug Streptolysins/*pharmacology Stress Survival/drug Vesicles/drug effects rac1 rhoA %N 8 %P 2897-902 %T Cholesterol-dependent actin remodeling via RhoA and Rac1 activation by the Streptococcus pneumoniae toxin pneumolysin %U http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=17301241 %V 104 %X The Streptococcus pneumoniae toxin pneumolysin belongs to the group of cholesterol-dependent cytolysins. It produces rapid cell lysis at higher concentrations or apoptosis at lower concentrations. In cell membranes, it forms prepores and pores. Here, we show that sublytic concentrations of pneumolysin produce rapid activation of Rho and Rac GTPases and formation of actin stress fibers, filopodia, and lamellipodia. That Rac1-specific and Rho-associated kinase (ROCK)-specific inhibitors reverted the formation of lamellipodia and stress fibers, respectively, identifies RhoA and Rac1 as key toxin effectors. Live imaging excluded macropore formation (as judged by membrane impermeability toward calcein) but indicated very early membrane depolarization as judged by bis-(1,3-dibutylbarbituric acid)trimethine oxanol staining, indicative of formation of micropores with ion channel properties. That Rac1-dependent lamellipodia formation was reverted by the voltage-gated calcium channel inhibitor SKF96365 and by toxin exposure in calcium-free medium suggests a role for calcium influx via endogenous calcium channels in the Rac1 activation. Cellular cholesterol depletion by methyl-beta-cyclodextrin or incubation of the toxin with cholesterol before cell treatment eliminated its membrane binding and the subsequent GTPase activation. Thus, that our experiments show small GTPase activation by a cholesterol-dependent cytolysin suggests a membrane cholesterol-dependent activation mechanism.

@article{Iliev2007, abstract = {The Streptococcus pneumoniae toxin pneumolysin belongs to the group of cholesterol-dependent cytolysins. It produces rapid cell lysis at higher concentrations or apoptosis at lower concentrations. In cell membranes, it forms prepores and pores. Here, we show that sublytic concentrations of pneumolysin produce rapid activation of Rho and Rac GTPases and formation of actin stress fibers, filopodia, and lamellipodia. That Rac1-specific and Rho-associated kinase (ROCK)-specific inhibitors reverted the formation of lamellipodia and stress fibers, respectively, identifies RhoA and Rac1 as key toxin effectors. Live imaging excluded macropore formation (as judged by membrane impermeability toward calcein) but indicated very early membrane depolarization [as judged by bis-(1,3-dibutylbarbituric acid)trimethine oxanol staining], indicative of formation of micropores with ion channel properties. That Rac1-dependent lamellipodia formation was reverted by the voltage-gated calcium channel inhibitor SKF96365 and by toxin exposure in calcium-free medium suggests a role for calcium influx via endogenous calcium channels in the Rac1 activation. Cellular cholesterol depletion by methyl-beta-cyclodextrin or incubation of the toxin with cholesterol before cell treatment eliminated its membrane binding and the subsequent GTPase activation. Thus, that our experiments show small GTPase activation by a cholesterol-dependent cytolysin suggests a membrane cholesterol-dependent activation mechanism.}, added-at = {2010-12-14T18:12:02.000+0100}, author = {Iliev, A. I. and Djannatian, J. R. and Nau, R. and Mitchell, T. J. and Wouters, F. S.}, biburl = {https://www.bibsonomy.org/bibtex/2e88da3b683142e4523254f4f39a2ac93/pharmawuerz}, endnotereftype = {Journal Article}, interhash = {99ac31ad6fd228732750c3ee2a9a5682}, intrahash = {e88da3b683142e4523254f4f39a2ac93}, issn = {0027-8424 (Print) 0027-8424 (Linking)}, journal = {Proc Natl Acad Sci U S A}, keywords = {Actins/*metabolism Activation/drug Bacterial Calcium/metabolism Cell Cholesterol/*pharmacology Cytoplasmic Death/drug Enzyme Exchange Factors/metabolism Fibers/drug GTP-Binding Guanine Humans Nucleotide Phenotype Protein/*metabolism Proteins/pharmacology Pseudopodia/drug Shape/drug Streptolysins/*pharmacology Stress Survival/drug Vesicles/drug effects rac1 rhoA}, month = {Feb 20}, note = {Iliev, Asparouh I Djannatian, Jasmin Roya Nau, Roland Mitchell, Timothy J Wouters, Fred S Wellcome Trust/United Kingdom Research Support, Non-U.S. Gov't United States Proceedings of the National Academy of Sciences of the United States of America Proc Natl Acad Sci U S A. 2007 Feb 20;104(8):2897-902. Epub 2007 Feb 14.}, number = 8, pages = {2897-902}, shorttitle = {Cholesterol-dependent actin remodeling via RhoA and Rac1 activation by the Streptococcus pneumoniae toxin pneumolysin}, timestamp = {2010-12-14T18:12:15.000+0100}, title = {Cholesterol-dependent actin remodeling via RhoA and Rac1 activation by the Streptococcus pneumoniae toxin pneumolysin}, url = {http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=17301241}, volume = 104, year = 2007 }