Project description:Among the diseases caused by Toll-like receptor 4 (TLR4) abnormal activation by bacterial endotoxin, sepsis is the most dangerous one. The reprogramming of macrophages plays a crucial role in orchestrating the pathogenesis of sepsis. However, the precise mechanism underlying TLR4 activation in macrophages remained incompletely understood. Our studies revealed that upon lipopolysaccharide (LPS) stimulation, CREB-binding protein (CBP) was recruited to the TLR4 signalosome complex and resulted in pronounced acetylation in the TIR domains of TLR4, Myeloid differentiation factor 88 (MyD88) and MyD88 adapter-like (MAL), which significantly enhanced the activation of the NF-κB signaling pathway and polarization of M1 macrophages. In sepsis patients, significantly elevated TLR4-TIR acetylation was detected in CD16+ monocytes combined with elevated expression of M1 macrophage markers and production of pro-inflammatory cytokines. In contrast, histone deacetylase 1 (HDAC1) served as a key deacetylase in the deacetylation of the TIR domain complex. The inhibition of HDAC1 accelerated sepsis-associated syndromes, while the inhibition of CBP alleviated this process. Overall, our findings highlighted the crucial role of TIR domain complex acetylation in the regulation of inflammatory immune response and suggested that the reversible acetylation of the complex emerged as a promising therapeutic target for M1 macrophages during the progression of sepsis.
Project description:Among the diseases caused by Toll-like receptor 4 (TLR4) abnormal activation by bacterial endotoxin, sepsis is the most dangerous one. The reprogramming of macrophages plays a crucial role in orchestrating the pathogenesis of sepsis. However, the precise mechanism underlying TLR4 activation in macrophages remained incompletely understood. Our studies revealed that upon lipopolysaccharide (LPS) stimulation, CREB-binding protein (CBP) was recruited to the TLR4 signalosome complex and resulted in pronounced acetylation in the TIR domains of TLR4, Myeloid differentiation factor 88 (MyD88) and MyD88 adapter-like (MAL), which significantly enhanced the activation of the NF-κB signaling pathway and polarization of M1 macrophages. In sepsis patients, significantly elevated TLR4-TIR acetylation was detected in CD16+ monocytes combined with elevated expression of M1 macrophage markers and production of pro-inflammatory cytokines. In contrast, histone deacetylase 1 (HDAC1) served as a key deacetylase in the deacetylation of the TIR domain complex. The inhibition of HDAC1 accelerated sepsis-associated syndromes, while the inhibition of CBP alleviated this process. Overall, our findings highlighted the crucial role of TIR domain complex acetylation in the regulation of inflammatory immune response and suggested that the reversible acetylation of the complex emerged as a promising therapeutic target for M1 macrophages during the progression of sepsis.
Project description:Among the diseases caused by Toll-like receptor 4 (TLR4) abnormal activation by bacterial endotoxin, sepsis is the most dangerous one. The reprogramming of macrophages plays a crucial role in orchestrating the pathogenesis of sepsis. However, the precise mechanism underlying TLR4 activation in macrophages remained incompletely understood. Our studies revealed that upon lipopolysaccharide (LPS) stimulation, CREB-binding protein (CBP) was recruited to the TLR4 signalosome complex and resulted in pronounced acetylation in the TIR domains of TLR4, Myeloid differentiation factor 88 (MyD88) and MyD88 adapter-like (MAL), which significantly enhanced the activation of the NF-κB signaling pathway and polarization of M1 macrophages. In sepsis patients, significantly elevated TLR4-TIR acetylation was detected in CD16+ monocytes combined with elevated expression of M1 macrophage markers and production of pro-inflammatory cytokines. In contrast, histone deacetylase 1 (HDAC1) served as a key deacetylase in the deacetylation of the TIR domain complex. The inhibition of HDAC1 accelerated sepsis-associated syndromes, while the inhibition of CBP alleviated this process. Overall, our findings highlighted the crucial role of TIR domain complex acetylation in the regulation of inflammatory immune response and suggested that the reversible acetylation of the complex emerged as a promising therapeutic target for M1 macrophages during the progression of sepsis.
Project description:Vaccinia virus immunomodulator A46 is a member of the poxviral Bcl-2-like protein family that inhibits the cellular innate immune response at the level of the TIR domain-containing TLR adaptor proteins MAL, MyD88, TRAM and TRIF. The mechanism of interaction of A46 with its targets has remained unclear. We used BS3 and EDC + sulfo-NHS to cross-link A46 to the TIR domains of MAL and MyD88 to help identify interacting residues and regions.
Project description:Activation of the Toll-like receptor 4 (TLR4) by bacterial endotoxins in macrophages plays a crucial role in the pathogenesis of sepsis. However, the mechanism underlying TLR4 activation in macrophages is still not fully understood. Here, we reveal that upon lipopolysaccharide (LPS) stimulation, lysine acetyltransferase CBP is recruited to the TLR4 signalosome complex leading to increased acetylation of the TIR domains of the TLR4 signalosome. Acetylation of the TLR4 signalosome TIR domains significantly enhances signaling activation via NF-κB rather than IRF3 pathways. Induction of NF-κB signaling is responsible for gene expression changes leading to M1 macrophage polarization. In sepsis patients, significantly elevated TLR4-TIR acetylation is observed in CD16+ monocytes combined with elevated expression of M1 macrophage markers. Pharmacological inhibition of HDAC1, which deacetylates the TIR domains, or CBP play opposite roles in sepsis. Our findings highlight an important role of TLR4-TIR domain acetylation in the regulation of the immune responses in sepsis, and we propose this reversible acetylation of TLR4 signalosomes as a potential therapeutic target for M1 macrophages during the progression of sepsis.
Project description:This study shows that the TLR4/MyD88 pathway in intestinal mesenchymal cells promotes intestinal carcinogenesis in the APCmin mouse model.
Project description:Toll-like receptor (TLR) signaling is a key innate immunity response to pathogens. Recruitment of signaling adapters such as MAL (TIRAP) and MyD88 to the TLRs requires Toll/interleukin-1 receptor (TIR)-domain interactions, which remain structurally elusive. Here we show that MAL TIR domains spontaneously and reversibly form filaments in vitro. They also form cofilaments with TLR4 TIR domains and induce formation of MyD88 assemblies. A 7-Å-resolution cryo-EM structure reveals a stable MAL protofilament consisting of two parallel strands of TIR-domain subunits in a BB-loop-mediated head-to-tail arrangement. Interface residues that are important for the interaction are conserved among different TIR domains. Although large filaments of TLR4, MAL or MyD88 are unlikely to form during cellular signaling, structure-guided mutagenesis, combined with in vivo interaction assays, demonstrated that the MAL interactions defined within the filament represent a template for a conserved mode of TIR-domain interaction involved in both TLR and interleukin-1 receptor signaling.
Project description:The adapter protein MyD88 adapter-like (Mal), encoded by TIR-domain containing adapter protein (Tirap) (MIM 606252), is the most polymorphic of the five adapter proteins involved in Toll-like receptor signaling, harboring eight non-synonymous single nucleotide polymorphisms in its coding region. We screened reported mutations of Mal for activity in reporter assays to test the hypothesis that variants of Mal existed with altered signaling potential. A TIR domain variant, Mal D96N (rs8177400), was found to be inactive. In reconstituted cell lines, Mal D96N acted as a hypomorphic mutation, with impaired cytokine production and NF-kappaB activation upon lipopolysaccharide or PAM2CSK4 stimulation. Moreover, co-immunoprecipitation studies revealed that Mal D96N is unable to interact with MyD88, a prerequisite for downstream signaling to occur. Computer modeling data suggested that residue 96 resides in the MyD88 binding site, further supporting these findings. Genotyping of Mal D96N in three different cohorts suggested that it is a rare mutation. We, thus, describe a rare variant in Mal that exerts its effect via its inability to bind MyD88.