title: Activation of Rac, Cdc42 and other downstream signalling molecules by Bartonella bacilliformis during entry into human endothelial cells.
abstract: Bartonella bacilliformis is an intracellular bacterial pathogen of human endothelial cells. In vitro incubation of B. bacilliformis with human endothelial cells leads to the formation of filamentous actin extensions (filopodia) within 30 min, followed by formation of membrane rufflings or lamellipodia within 1 h of incubation. By immunofluorescence, F-actin phalloidin staining and anti-Rac antibodies were shown to co-localize in the membrane rufflings, indicating the recruitment of activated Rac at lamellipodia. Preincubation of endothelial cells with the Clostridial toxin, TcdB-10463, which inactivates the Rho-family GTPases, Rho, Rac and Cdc42, inhibited the entry of B. bacilliformis by 50-90%. Preincubation of endothelial cells with the Clostridial toxin, TcsL-1522, which specifically inactivates Rac and, to a lesser extent, Cdc42, but not Rho, inhibited entry by 30-40%. A 3.4-5.0-fold increase in activated (GTP-bound) -intracellular Rac and Cdc42 was observed in affinity precipitation assays. Increased kinase activity of p21-activated kinase (PAK), a specific downstream effector of activated Rac/Cdc42 was also observed during the time course of infection. Activation of SAPK/JNK-1 and 2, and p38 MAPKs in signalling pathways, was also detected during infection with Bartonella, as was increased binding activity of AP-1 transcription factor.
authors.affiliation: Department of Microbiology and Immunology, F. Edward Hébert School of Medicine, Uniformed Services University of Health Sciences, Bethesda, MD 20814-4799, USA.
authors.forename: Anita
authors.initials: A
authors.lastname: Verma
authors.forename: Garret M
authors.initials: GM
authors.lastname: Ihler
mesh_terms: D000199:Actins / Q000032:analysis / Q000378:metabolism; D001426:Bacterial Proteins; D001427:Bacterial Toxins / Q000494:pharmacology; D001473:Bartonella / Q000472:pathogenicity*; D002462:Cell Membrane / Q000201:enzymology; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism* / Q000382:microbiology*; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020935:MAP Kinase Signaling System; D048055:Mitogen-Activated Protein Kinase 8; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000032:analysis* / Q000378:metabolism; D011554:Pseudopodia / Q000378:metabolism / Q000648:ultrastructure; D015398:Signal Transduction / Q000502:physiology*; D013997:Time Factors; D018808:Transcription Factor AP-1 / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*; D054462:p21-Activated Kinases; D020744:rac GTP-Binding Proteins / Q000276:immunology / Q000378:metabolism*
chemical_list: D000199:Actins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D018808:Transcription Factor AP-1; C072292:lethal toxin LT, Clostridium sordellii; C031815:toxB protein, Clostridium difficile; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins