SopE and SopE2 from Salmonella typhimurium activate different sets of RhoGTPases of the host cell.
The bacterial enteropathogen Salmonella typhimurium employs a specialized type III secretion system to inject toxins into host cells, which trigger signaling cascades leading to cell death in macrophages, secretion of pro-inflammatory cytokines, or rearrangements of the host cell cytoskeleton and thus to bacterial invasion. Two of the injected toxins, SopE and the 69% identical protein SopE2, are highly efficient guanine nucleotide exchange factors for the RhoGTPase Cdc42 of the host cell. However, it has been a puzzle why S. typhimurium might employ two toxins with redundant function. We hypothesized that SopE and SopE2 might have different specificities for certain host cellular RhoGTPases. In vitro guanine nucleotide exchange assays and surface plasmon resonance measurements revealed that SopE is an efficient guanine nucleotide exchange factor for Cdc42 and Rac1, whereas SopE2 was interacting efficiently only with Cdc42, but not with Rac1. Affinity precipitation of Cdc42.GTP and Rac1.GTP from lysates and characteristic cytoskeletal rearrangements of infected tissue culture cells confirmed that SopE is highly efficient at activating Cdc42 and Rac1 in vivo, whereas SopE2 was efficiently activating Cdc42, but not Rac1. We conclude that the translocated effector proteins SopE and SopE2 allow S. typhimurium to specifically activate different sets of RhoGTPase signaling cascades.
Friebel
A
A
Max von Pettenkofer-Institut, Ludwig Maximilians Universität, Pettenkoferstrasse 9a, 80336 München, Germany.
Ilchmann
H
H
Aepfelbacher
M
M
Ehrbar
K
K
Machleidt
W
W
Hardt
W D
WD
D001426:Bacterial Proteins / Q000502:physiology*; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000166:cytology; D004789:Enzyme Activation; D005982:Glutathione Transferase / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D008264:Macrophages / Q000382:microbiology; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000378:metabolism; D012486:Salmonella typhimurium / Q000737:chemistry*; D015398:Signal Transduction; D013050:Spectrometry, Fluorescence; D020349:Surface Plasmon Resonance; D013997:Time Factors; D014471:Umbilical Veins / Q000166:cytology; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000737:chemistry*
D001426:Bacterial Proteins; D020662:Guanine Nucleotide Exchange Factors; D011994:Recombinant Proteins; C103987:SopE protein, Salmonella; C436324:SopE2 protein, Salmonella typhimurium; D005982:Glutathione Transferase; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein; D020741:rho GTP-Binding Proteins