title: In vivo rho GTPase-activating protein activity of Pseudomonas aeruginosa cytotoxin ExoS.
abstract: ExoS is a bifunctional type III cytotoxin secreted by Pseudomonas aeruginosa, which comprises a C-terminal ADP ribosyltransferase domain and an N-terminal Rho GTPase-activating protein (GAP) domain. In vitro, ExoS is a Rho GAP for Rho, Rac, and Cdc42; however, the in vivo modulation of Rho GTPases has not been addressed. Using a transient transfection system and delivery by P. aeruginosa, interactions were examined between the Rho GAP domain of ExoS and Rho GTPases in CHO cells. Rho GTPases were expressed as green fluorescent protein (GFP) fusion proteins to facilitate quantitation. GFP fusions of wild-type and dominant active Rho, Rac, and Cdc42 localized to discrete regions of CHO cells and appeared functional based upon their modulation of the actin cytoskeleton. Coexpression of the Rho GAP domain of ExoS changed the intracellular distribution of GFP-Rac and GFP-Cdc42 from a predominately membrane location to a cytosolic location. Coexpression of the Rho GAP domain of ExoS did not change the distribution of GFP-Rho, which was primarily in the cytosol. Coexpression of dominant active Rac (DARac) and DACdc42 inhibited actin reorganization by the Rho GAP domain but did not maintain the formation of actin stress fibers, which indicated that Rho had been inactivated. Similar results were observed when ExoS was delivered into CHO cells by P. aeruginosa. These data indicate that in vivo the Rho GAP activity of ExoS stimulates the reorganization of the actin cytoskeleton by inhibition of Rac and Cdc42 and stimulates actin stress fiber formation by inhibition of Rho.
authors.affiliation: Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Krall
authors.forename: Jianjun
authors.initials: J
authors.lastname: Sun
authors.forename: Kristin J
authors.initials: KJ
authors.lastname: Pederson
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Barbieri
mesh_terms: D036002:ADP Ribose Transferases / Q000235:genetics / Q000378:metabolism*; D000199:Actins / Q000378:metabolism; D000818:Animals; D001427:Bacterial Toxins; D016466:CHO Cells; D006224:Cricetinae; D003599:Cytoskeleton / Q000378:metabolism; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D049452:Green Fluorescent Proteins; D006160:Guanosine Triphosphate / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics; D011550:Pseudomonas aeruginosa / Q000201:enzymology* / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D000199:Actins; D001427:Bacterial Toxins; D020690:GTPase-Activating Proteins; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; C085379:rho GTPase-activating protein; D049452:Green Fluorescent Proteins; D006160:Guanosine Triphosphate; D036002:ADP Ribose Transferases; C444820:exoenzyme S; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein