Abstract
CpG-DNA or its synthetic analog CpG-ODN activates innate immunity through Toll-like receptor 9 (TLR9). However, the mechanism of TLR9 activation by CpG-DNA remains elusive. Here we have identified HMGB1 as a CpG-ODN-binding protein. HMGB1 interacts and preassociates with TLR9 in the endoplasmic reticulum-Golgi intermediate compartment (ERGIC), and hastens TLR9's redistribution to early endosomes in response to CpG-ODN. CpG-ODN stimulates macrophages and dendritic cells to secrete HMGB1; in turn, extracellular HMGB1 accelerates the delivery of CpG-ODNs to its receptor, leading to a TLR9-dependent augmentation of IL-6, IL-12, and TNFalpha secretion. Loss of HMGB1 leads to a defect in the IL-6, IL-12, TNFalpha, and iNOS response to CpG-ODN. However, lack of intracellular TLR9-associated HMGB1 can be compensated by extracellular HMGB1. Thus, the DNA-binding protein HMGB1 shuttles in and out of immune cells and regulates inflammatory responses to CpG-DNA.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Animals
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Calnexin / metabolism
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Cell Nucleus / metabolism
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CpG Islands
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Endoplasmic Reticulum / drug effects
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Endoplasmic Reticulum / metabolism
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Enzyme-Linked Immunosorbent Assay
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Extracellular Matrix / metabolism
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Flow Cytometry
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Golgi Apparatus / drug effects
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Golgi Apparatus / metabolism
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HMGB1 Protein / genetics
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HMGB1 Protein / physiology*
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Immunoblotting
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Immunoprecipitation
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Interleukin-12 / metabolism*
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Interleukin-6 / metabolism*
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Lysosomes / metabolism
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Macrophages / cytology
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Macrophages / drug effects
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Macrophages / metabolism
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Mannose-Binding Lectins / metabolism
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Membrane Proteins / metabolism
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Mice
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Mice, Knockout
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Nitric Oxide Synthase Type II / metabolism
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Oligodeoxyribonucleotides / pharmacology*
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Secretory Vesicles / drug effects
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Secretory Vesicles / metabolism
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Toll-Like Receptor 9 / genetics
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Toll-Like Receptor 9 / physiology*
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Tumor Necrosis Factor-alpha / metabolism*
Substances
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CPG-oligonucleotide
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ERGIC-53 protein, mouse
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HMGB1 Protein
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Interleukin-6
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Mannose-Binding Lectins
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Membrane Proteins
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Oligodeoxyribonucleotides
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Tlr9 protein, mouse
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Toll-Like Receptor 9
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Tumor Necrosis Factor-alpha
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Calnexin
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Interleukin-12
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Nitric Oxide Synthase Type II
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Nos2 protein, mouse