Phosphoinositide-Mediated Adaptor Recruitment Controls Toll-like Receptor Signaling
ABSTRACT Toll-like receptors (TLRs) play a critical role in the immune system as sensors of microbial infection. Signaling downstream from TLRs is initiated by the recruitment of adaptor proteins, including MyD88 and TIRAP. These adaptors play essential roles in TLR signaling, but the mechanism of their function is currently unknown. Here we demonstrate that TIRAP and MyD88 have distinct functions and describe a mechanism of recruitment of TIRAP and MyD88 to TLR4. We find that TIRAP contains a phosphatidylinositol 4,5-bisphosphate (PIP2) binding domain, which mediates TIRAP recruitment to the plasma membrane. TIRAP then functions to facilitate MyD88 delivery to activated TLR4 to initiate signal transduction. These results establish that phosphoinositide-mediated adaptor recruitment initiates a specific signal-transduction pathway.
SourceAvailable from: PubMed Central[Show abstract] [Hide abstract]
ABSTRACT: Banhasasim-tang (BHSST) is a Korean traditional herbal formula comprising eight medicinal herbs. The aim of the present study was to investigate the anti-inflammatory effect of BHSST using macrophage and keratinocyte cell lines. First, we evaluated the effects of BHSST on inflammatory mediator and cytokine production in lipopolysaccharide- (LPS-) stimulated RAW 264.7 macrophages. BHSST markedly inhibited the production of nitric oxide (NO), prostaglandin E2 (PGE2), and interleukin- (IL-) 6. BHSST significantly suppressed the protein expression of toll-like receptor 4 (TLR4) and phosphorylated nuclear factor-kappa B (NF-κB) p65 in RAW 264.7 cells. Second, we examined whether BHSST influences the production of chemokines and STAT1 phosphorylation in tumor necrosis factor-α/interferon-γ TI-stimulated HaCaT keratinocytes. BHSST significantly suppressed the production of RANTES/CCL5, TARC/CCL17, MDC/CCL22, and IL-8 in TI-stimulated HaCaT cells. BHSST also suppressed TI-induced phosphorylation of STAT1 in HaCaT cells. These results suggest that BHSST may be useful as an anti-inflammatory agent, especially for inflammatory skin diseases.Evidence-based Complementary and Alternative Medicine 01/2015; 2015:728380. DOI:10.1155/2015/728380 · 2.18 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: Diphlorethohydroxycarmalol (DPHC) is a phlorotannin compound isolated from Ishige okamuarae, a brown alga. This study was conducted to investigate the anti-inflammatory effect and action mechanism of DPHC in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. We found that DPHC strongly reduces the production of interleukin 6 (IL-6), but not that of tumor necrosis factor-alpha (TNF-α) induced by LPS. DPHC (12.5 and 100 μM) suppressed the phosphorylation and the nuclear translocation of NF-kappaB (NF-κB), a central signaling molecule in the inflammation process induced by LPS. The suppressor of cytokine signaling 1 (SOCS1) is a negative feedback regulator of Janus kinase (Jak)-signal transducer and activator of transcription (STAT) signaling. In this study, DPHC inhibited STAT5 expression and upregulated that of SOCS1 at a concentration of 100 μM. Furthermore, N-tosyl-L-phenylalanine chloromethyl ketone (TPCK) (a specific NF-κB inhibitor) and JI (a specific Jak2 inhibitor) reduced the production of IL-6, but not that of tumor necrosis factor-alpha (TNF-α) in LPS-stimulated RAW 264.7 macrophages. These findings demonstrate that DPHC inhibits IL-6 production via the downregulation of NF-κB and Jak2-STAT5 pathway and upregulation of SOCS1. Keywords: diphlorethohydroxycarmalol (DPHC); IL-6; NF-κB; Jak-STAT; SOCS; LPS; inflammationMarine Drugs 03/2015; 13(4). DOI:10.3390/md13042141 · 3.51 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: Families of innate immune receptors serve as the bodies primary defence system by recognising and rapidly responding to infection by microorganisms or to endogenous danger signals and initiating inflammatory processes. Whilst Toll-like receptors (TLRs) were the first family to be discovered, important and exciting discoveries continue to emerge into the molecular mechanisms that control their activation and regulation. Herein, I will provide an overview of TLR activation and their downstream signalling cascades, and discuss some of the recent findings concerning the assembly of a TLR oligomeric signalling platform, known as the Myddosome. Further, a brief examination of the importance of crosstalk between multiple TLRs or between TLRs and other innate immune receptors for appropriate and coordinated immune responses will be presented. Finally, I will discuss the importance of mechanisms that regulate TLRs with a focus on the role of activating transcription factor 3 (ATF3) in modulating transcriptional responses downstream of TLRs. Copyright © 2015 Elsevier Ltd. All rights reserved.Cytokine 04/2015; DOI:10.1016/j.cyto.2015.02.025 · 2.87 Impact Factor