title: IRAK-M regulates the inhibition of TLR-mediated macrophage immune response during late in vitro Leishmania donovani infection.
abstract: Intramacrophage protozoan parasite Leishmania donovani, causative agent of visceral leishmaniasis, escapes Toll-like receptor (TLR) dependent early host immune response by inducing the deubiquitinating enzyme A20, which is sustained up to 6 h postinfection only. Therefore, Leishmania must apply other means to deactivate late host responses. Here, we elucidated the role of IL-1 receptor-associated kinase M (IRAK-M), a negative regulator of TLR signaling, in downregulating macrophage proinflammatory response during late hours of in vitro infection. Our data reveal a sharp decline in IRAK1 and IRAK4 phosphorylation at 24 h postinfection along with markedly reduced association of IRAK1-TNF receptor associated factor 6, which is mandatory for TLR activation. In contrast, IRAK-M was induced after A20 levels decreased and reached a maximum at 24 h postinfection. IRAK-M induction coincided with increased stimulation of TGF-β, a hallmark cytokine of visceral infection. TGF-β-dependent signaling-mediated induction of SMAD family of proteins, 2, 3, and 4 plays important roles in transcriptional upregulation of IRAK-M. In infected macrophages, siRNA-mediated silencing of IRAK-M displayed enhanced IRAK1 and IRAK4 phosphorylation with a concomitant increase in downstream NF-κB activity and reduced parasite survival. Taken together, the results suggest that IRAK-M may be targeted by L. donovani to inhibit TLR-mediated proinflammatory response late during in vitro infection.
authors.affiliation: Infectious Diseases and Immunology Division, CSIR-Indian Institute of Chemical Biology, Kolkata, India.
authors.forename: Supriya
authors.initials: S
authors.lastname: Srivastav
authors.affiliation: Department of Biochemistry, University of Calcutta, Kolkata, India.
authors.forename: Amrita
authors.initials: A
authors.lastname: Saha
authors.affiliation: Department of Biochemistry, University of Calcutta, Kolkata, India.
authors.forename: Jayita
authors.initials: J
authors.lastname: Barua
authors.affiliation: Department of Biochemistry, University of Calcutta, Kolkata, India.
authors.forename: Anindita
authors.initials: A
authors.lastname: Ukil
authors.affiliation: Infectious Diseases and Immunology Division, CSIR-Indian Institute of Chemical Biology, Kolkata, India.
authors.forename: Pijush K
authors.initials: PK
authors.lastname: Das
mesh_terms: D000818:Animals; D002460:Cell Line; D053592:Interleukin-1 Receptor-Associated Kinases / Q000276:immunology*; D007893:Leishmania donovani / Q000276:immunology*; D007898:Leishmaniasis, Visceral / Q000276:immunology* / Q000473:pathology; D008264:Macrophages / Q000276:immunology* / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D016328:NF-kappa B / Q000276:immunology; D010766:Phosphorylation / Q000276:immunology; D051193:Toll-Like Receptors / Q000276:immunology*; D016212:Transforming Growth Factor beta / Q000276:immunology
chemical_list: D016328:NF-kappa B; D051193:Toll-Like Receptors; D016212:Transforming Growth Factor beta; D053592:Interleukin-1 Receptor-Associated Kinases; C507769:Irak1 protein, mouse; C507772:Irak3 protein, mouse; C507774:Irak4 protein, mouse
keywords: Host defense; IRAK-M; Leishmania; Macrophage; Toll-like receptors