Publication Date:
2014-04-01
Description:
Intramacrophage pathogen Leishmania donovani escapes host immune response by subverting Toll-like receptor (TLR) signaling, which is critically regulated by protein ubiquitination. In the present study, we identified tumor necrosis factor receptor-associated factor (TRAF) 3, degradative ubiquitination of which is essential for TLR4 activation, as a target for Leishmania to deactivate LPS-mediated TLR4 signaling. We used LPS-treated RAW 264.7 cells and compared the TLR4-mediated immune response in these cells with L. donovani and L. donovani + LPS costimulated macrophages. TRAF3, which was ubiquitinated (2.1-fold over control) at lys 48 position and subsequently degraded following LPS treatment, persisted in L. donovani and L. donovani + LPS costimulated cells due to defective lys 48 ubiquitination. Lys 63-linked ubiquitination of upstream proteins in the cascade (cIAP1/2 and TRAF6), mandatory for TRAF3 degradation, was also reduced postinfection. This may be attributed to reduced association between ubiquitin-conjugating enzyme Ubc13 and TRAF6 during infection. Inhibition of TRAF3 before infection by shRNA in Balb/c mice showed enhanced IL-12 and TNF-α (10.8- and 8.1-fold over infected control) and decreased spleen parasite burden (61.3% suppression, P 〈0.001), thereby marking reduction in disease progression. Our findings identified TRAF3 as a novel molecular regulator exploited by Leishmania for successful infection.—Gupta, P., Giri, J., Srivastav, S., Chande, A. G., Mukhopadhyaya, R., Das, P. K., Ukil, A. Leishmania donovani targets tumor necrosis factor receptor-associated factor (TRAF) 3 for impairing TLR4-mediated host response.
Print ISSN:
0892-6638
Electronic ISSN:
1530-6860
Topics:
Biology
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