| Genome-Wide Expression Profiling and Mutagenesis Studies Reveal That Lipopolysaccharide Responsiveness Appears To Be Absolutely Dependent on TLR4 and MD-2 Expression and Is Dependent upon Intermolecular Ionic Interactions. | |
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MedLine Citation:
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PMID: 21865549 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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Lipid A (a hexaacylated 1,4' bisphosphate) is a potent immune stimulant for TLR4/MD-2. Upon lipid A ligation, the TLR4/MD-2 complex dimerizes and initiates signal transduction. Historically, studies also suggested the existence of TLR4/MD-2-independent LPS signaling. In this article, we define the role of TLR4 and MD-2 in LPS signaling by using genome-wide expression profiling in TLR4- and MD-2-deficient macrophages after stimulation with peptidoglycan-free LPS and synthetic Escherichia coli lipid A. Of the 1396 genes significantly induced or repressed by any one of the treatments in the wild-type macrophages, none was present in the TLR4- or MD-2-deficient macrophages, confirming that the TLR4/MD-2 complex is the only receptor for endotoxin and that both are required for responses to LPS. Using a molecular genetics approach, we investigated the mechanism of TLR4/MD-2 activation by combining the known crystal structure of TLR4/MD-2 with computer modeling. According to our murine TLR4/MD-2-activation model, the two phosphates on lipid A were predicted to interact extensively with the two positively charged patches on mouse TLR4. When either positive patch was abolished by mutagenesis into Ala, the responses to LPS and lipid A were nearly abrogated. However, the MyD88-dependent and -independent pathways were impaired to the same extent, indicating that the adjuvant activity of monophosphorylated lipid A most likely arises from its decreased potential to induce an active receptor complex and not more downstream signaling events. Hence, we concluded that ionic interactions between lipid A and TLR4 are essential for optimal LPS receptor activation. |
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Authors:
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Jianmin Meng; Mei Gong; Harry Björkbacka; Douglas T Golenbock |
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Publication Detail:
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Type: JOURNAL ARTICLE Date: 2011-8-24 |
Journal Detail:
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Title: Journal of immunology (Baltimore, Md. : 1950) Volume: - ISSN: 1550-6606 ISO Abbreviation: - Publication Date: 2011 Aug |
Date Detail:
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Created Date: 2011-8-25 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 2985117R Medline TA: J Immunol Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
Affiliation:
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Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, MA 01605. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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