Different domains of Pseudomonas aeruginosa exoenzyme S activate distinct TLRs.
Some bacterial products possess multiple immunomodulatory effects and thereby complex mechanisms of action. Exogenous administration of an important Pseudomonas aeruginosa virulence factor, exoenzyme S (ExoS) induces potent monocyte activation leading to the production of numerous proinflammatory cytokines and chemokines. However, ExoS is also injected directly into target cells, inducing cell death through its multiple effects on signaling pathways. This study addresses the mechanisms used by ExoS to induce monocyte activation. Exogenous administration resulted in specific internalization of ExoS via an actin-dependent mechanism. However, ExoS-mediated cellular activation was not inhibited if internalization was blocked, suggesting an alternate mechanism of activation. ExoS bound a saturable and specific receptor on the surface of monocytic cells. ExoS, LPS, and peptidoglycan were all able to induce tolerance and cross-tolerance to each other suggesting the involvement of a TLR in ExoS-recognition. ExoS activated monocytic cells via a myeloid differentiation Ag-88 pathway, using both TLR2 and the TLR4/MD-2/CD14 complex for cellular activation. Interestingly, the TLR2 activity was localized to the C-terminal domain of ExoS while the TLR4 activity was localized to the N-terminal domain. This study provides the first example of how different domains of the same molecule activate two TLRs, and also highlights the possible overlapping pathophysiological processes possessed by microbial toxins.
Epelman
Slava
S
Department of Microbiology and Infectious Diseases, University of Calgary, Calgary, Alberta, Canada.
Stack
Danuta
D
Bell
Chris
C
Wong
Erica
E
Neely
Graham G
GG
Krutzik
Stephan
S
Miyake
Kensuke
K
Kubes
Paul
P
Zbytnuik
Lori D
LD
Ma
Ling Ling
LL
Xie
Xiaobin
X
Woods
Donald E
DE
Mody
Christopher H
CH
D036002:ADP Ribose Transferases / Q000737:chemistry* / Q000502:physiology; D008841:Actin Cytoskeleton / Q000187:drug effects / Q000502:physiology; D048868:Adaptor Proteins, Signal Transducing; D000943:Antigens, Differentiation / Q000502:physiology; D000954:Antigens, Surface / Q000502:physiology; D001427:Bacterial Toxins / Q000737:chemistry*; D002460:Cell Line / Q000187:drug effects / Q000378:metabolism; D015638:Cytochalasin D / Q000494:pharmacology; D005456:Fluorescent Dyes; D006801:Humans; D018950:Lipopolysaccharide Receptors / Q000502:physiology; D008070:Lipopolysaccharides / Q000494:pharmacology; D051218:Lymphocyte Antigen 96; D046911:Macromolecular Substances; D008562:Membrane Glycoproteins / Q000819:agonists*; D009000:Monocytes / Q000187:drug effects* / Q000378:metabolism; D053594:Myeloid Differentiation Factor 88; D010457:Peptidoglycan / Q000494:pharmacology; D017434:Protein Structure, Tertiary; D011550:Pseudomonas aeruginosa / Q000201:enzymology*; D011956:Receptors, Cell Surface / Q000819:agonists*; D011971:Receptors, Immunologic / Q000037:antagonists & inhibitors / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000494:pharmacology; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis
D048868:Adaptor Proteins, Signal Transducing; D000943:Antigens, Differentiation; D000954:Antigens, Surface; D001427:Bacterial Toxins; D005456:Fluorescent Dyes; C495377:LY96 protein, human; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D051218:Lymphocyte Antigen 96; C507779:MYD88 protein, human; D046911:Macromolecular Substances; D008562:Membrane Glycoproteins; D053594:Myeloid Differentiation Factor 88; D010457:Peptidoglycan; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic; D011993:Recombinant Fusion Proteins; C495342:TLR2 protein, human; C495345:TLR4 protein, human; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha; D015638:Cytochalasin D; D036002:ADP Ribose Transferases; C444820:exoenzyme S