Different Domains of Pseudomonas aeruginosa Exoenzyme S Activate Distinct TLRs

• Published in: The Journal of immunology (1950) Vol. 173; no. 3; pp. 2031 - 2040
• Main Authors: Epelman, Slava, Stack, Danuta, Bell, Chris, Wong, Erica, Neely, Graham G, Krutzik, Stephan, Miyake, Kensuke, Kubes, Paul, Zbytnuik, Lori D, Ma, Ling Ling, Xie, Xiaobin, Woods, Donald E, Mody, Christopher H
• Format: Journal Article
• Language: English
• Published: United States Am Assoc Immnol 01.08.2004
• Subjects: Actin Cytoskeleton - drug effects; Actin Cytoskeleton - physiology; Adaptor Proteins, Signal Transducing; ADP Ribose Transferases - chemistry; ADP Ribose Transferases - physiology; Antigens, Differentiation - physiology; Antigens, Surface - physiology; Bacterial Toxins - chemistry; Cell Line - drug effects; Cell Line - metabolism; Cytochalasin D - pharmacology; Fluorescent Dyes; Humans; Lipopolysaccharide Receptors - physiology; Lipopolysaccharides - pharmacology; Lymphocyte Antigen 96; Macromolecular Substances; Membrane Glycoproteins - agonists; Monocytes - drug effects; Monocytes - metabolism; Myeloid Differentiation Factor 88; Peptidoglycan - pharmacology; Protein Structure, Tertiary; Pseudomonas aeruginosa; Pseudomonas aeruginosa - enzymology; Receptors, Cell Surface - agonists; Receptors, Immunologic - antagonists & inhibitors; Receptors, Immunologic - physiology; Recombinant Fusion Proteins - pharmacology; Toll-Like Receptor 2; Toll-Like Receptor 4; Toll-Like Receptors; Tumor Necrosis Factor-alpha - biosynthesis
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.173.3.2031

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.