High mobility group box 1 protein interacts with multiple Toll-like receptors

Abstract

High mobility group box 1 (HMGB1), originally described as a DNA-binding protein, can also be released extracellularly and functions as a late mediator of inflammatory responses. Although recent reports have indicated that the receptor for advanced glycation end products (RAGE) as well as Toll-like receptor (TLR)2 and TLR4 are involved in cellular activation by HMGB1, there has been little evidence of direct association between HMGB1 and these receptors. To examine this issue, we used fluorescence resonance energy transfer (FRET) and immunoprecipitation to directly investigate cell surface interactions of HMGB1 with TLR2, TLR4, and RAGE. FRET images in RAW264.7 macrophages demonstrated association of HMGB1 with TLR2 and TLR4 but not RAGE. Transient transfections into human embryonic kidney-293 cells showed that HMGB1 induced cellular activation and NF-Bdependent transcription through TLR2 or TLR4 but not RAGE. Coimmunoprecipitation also found interaction between HMGB1 and TLR2 as well as TLR4, but not with RAGE. These studies provide the first direct evidence that HMGB1 can interact with both TLR2 and TLR4 and also supply an explanation for the ability of HMGB1 to induce cellular activation and generate inflammatory responses that are similar to those initiated by LPS. fluorescence resonance energy transfer; receptor of advanced glycation end products HIGH MOBILITY GROUP BOX 1 (HMGB1) protein, originally described as a DNA-binding protein that stabilizes nucleosomes and facilitates transcription, can also be released extracellularly by monocytes and macrophages stimulated by LPS, TNF-␣, or IL-1 (2, 44). Extracellular HMGB1 has been demonstrated to participate in inflammatory processes, including delayed endotoxin lethality and acute lung injury (1,44,46), and also appears to be involved in pathophysiological processes associated with cellular necrosis, such as acetaminophen-induced liver injury (34).Although HMGB1 and LPS appear to initiate similar intracellular events, including activation of kinases such as p38, ERK1/2, and Akt and transcriptional factors including NF-B, that lead to production of proinflammatory cytokines, gene arrays demonstrated differences in expression profiles with each of these stimuli (12, 30). Unlike LPS, which primarily increased the activity of IKK-␤, HMGB1 exposure resulted in activation of both IKK-␣ and IKK-␤ (31). In addition, culture of neutrophils lacking Toll-like receptor (TLR)4 with HMGB1, but not with LPS, still resulted in enhanced nuclear translocation of NF-B (31). Such results suggest that the receptors interacting with HMGB1 and leading to cellular activation and gene transcription are likely to be distinct from TLR4, which is responsible for LPS-induced responses (40). Recent data indicate that HMGB1 interacts not only with TLR4 but also with TLR2 and the receptor for advanced glycation end products (RAGE) (31, 46). In particular, a decrease in NF-B-dependent reporter gene expression after transfection with dominantnegative constructs to TLR2, TLR4, or both, demonstr...

HMGB1 Develops Enhanced Proinflammatory Activity by Binding to Cytokines

“…Several studies indicated that HMGB1 could interact with multiple receptors, including TLR2, TLR4, the receptor for advanced glycation end products, and, most recently, TLR9 (10,17,19,20,26). Similarly, varying intracellular signaling pathways, involving p38 MAP, ERK, JNK, and other kinases, were reported to be activated in HMGB1-exposed cells (10, 11, 19 -22, 27-32).…”

Both TLR2 and TLR4 Are Required for the Effective Immune Response in Staphylococcus aureus-Induced Experimental Murine Brain Abscess

“…29 The function of TLRs is not limited to pathogen control, and TLR2 and TLR4 have been implicated in wound healing in a noninfectious lung injury model. 38 In addition, TLR2 and TLR4 have not only been reported to recognize "stranger signals " from bacteria but also to transduce endogenous "danger signals " like fibronectin, 39 hyaluron acid, 40 and HMGB1, 41 all of which may be found at abundance within large areas of tissue necrosis in the setting of brain abscess. Thus, in our model, TLR2 and TLR4 might be required to limit the size and to resolve the abscess.…”

Immunogenic death of colon cancer cells treated with oxaliplatin

“…Indeed, dying cells release HMGB1 into the extracellular milieu in response to most chemotherapeutic agents (Apetoh et al, 2007a, b), and neutralization or depletion of HMGB1 abolishes the immunogenicity of cell death . HMGB1 can interact with several receptors expressed on the surface of DCs (Park et al, 2006) including tolllike receptor 4 (TLR4). Mice that lack TLR4 or that bear a mutant TLR4 fail to mount an immune response against anthracyclin-treated cancer cells .…”