title: Leishmania donovani targets tumor necrosis factor receptor-associated factor (TRAF) 3 for impairing TLR4-mediated host response.
abstract: 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.
authors.affiliation: 2Department of Biochemistry, University of Calcutta, 35, Ballygunge Circular Rd., Kolkata-700019, India. aninditau@yahoo.com.
authors.forename: Purnima
authors.initials: P
authors.lastname: Gupta
authors.forename: Jayeeta
authors.initials: J
authors.lastname: Giri
authors.forename: Supriya
authors.initials: S
authors.lastname: Srivastav
authors.forename: Ajit G
authors.initials: AG
authors.lastname: Chande
authors.forename: Robin
authors.initials: R
authors.lastname: Mukhopadhyaya
authors.forename: Pijush K
authors.initials: PK
authors.lastname: Das
authors.forename: Anindita
authors.initials: A
authors.lastname: Ukil
mesh_terms: D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D015870:Gene Expression / Q000276:immunology; D006790:Host-Parasite Interactions / Q000276:immunology; D015151:Immunoblotting; D018664:Interleukin-12 / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D007893:Leishmania donovani / Q000276:immunology* / Q000502:physiology; D007898:Leishmaniasis, Visceral / Q000235:genetics / Q000276:immunology / Q000469:parasitology; D008070:Lipopolysaccharides / Q000276:immunology / Q000494:pharmacology; D008239:Lysine / Q000276:immunology / Q000378:metabolism; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism / Q000469:parasitology; D051379:Mice; D008807:Mice, Inbred BALB C; D018448:Models, Immunological; D016328:NF-kappa B / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000276:immunology*; D048008:TNF Receptor-Associated Factor 3 / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D054875:Ubiquitination / Q000187:drug effects / Q000276:immunology
chemical_list: D008070:Lipopolysaccharides; D016328:NF-kappa B; D048008:TNF Receptor-Associated Factor 3; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; D018664:Interleukin-12; D008239:Lysine
keywords: macrophage; signalosome; ubiquitination