The Extra Domain A of Fibronectin Activates Toll-like Receptor 4

• Published in: The Journal of biological chemistry Vol. 276; no. 13; pp. 10229 - 10233
• Main Authors: Okamura, Yoshinori, Watari, Michiko, Jerud, Elliot S., Young, Donna W., Ishizaka, Sally T., Rose, Jeffrey, Chow, Jesse C., Strauss, Jerome F.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 30.03.2001; American Society for Biochemistry and Molecular Biology
• Subjects: Animals; Anti-Bacterial Agents - pharmacology; Antigens, Surface - metabolism; Blotting, Western; Cell Line; Dose-Response Relationship, Drug; Drosophila Proteins; Enzyme Activation; Exons; Fibronectins - chemistry; Fibronectins - metabolism; Hot Temperature; Humans; Inflammation; Interleukin-10 - biosynthesis; Lipid A - analogs & derivatives; Lipid A - pharmacology; Lipopolysaccharides - antagonists & inhibitors; Lipopolysaccharides - pharmacology; Lymphocyte Antigen 96; Matrix Metalloproteinase 9 - metabolism; Membrane Glycoproteins - metabolism; Mice; Mice, Inbred C3H; Plasmids - metabolism; Polymyxin B - pharmacology; Protein Structure, Tertiary; Receptors, Cell Surface - metabolism; Recombinant Proteins - chemistry; Recombinant Proteins - metabolism; Reverse Transcriptase Polymerase Chain Reaction; Signal Transduction; Spleen - cytology; Time Factors; Toll-Like Receptor 4; Toll-Like Receptors; Transfection
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M100099200

Cellular fibronectin, which contains an alternatively spliced exon encoding type III repeat extra domain A (EDA), is produced in response to tissue injury. Fragments of fibronectin have been implicated in physiological and pathological processes, especially tissue remodeling associated with inflammation. Because EDA-containing fibronectin fragments produce cellular responses similar to those provoked by bacterial lipopolysaccharide (LPS), we examined the ability of recombinant EDA to activate Toll-like receptor 4 (TLR4), the signaling receptor stimulated by LPS. We found that recombinant EDA, but not other recombinant fibronectin domains, activates human TLR4 expressed in a cell type (HEK 293 cells) that normally lacks this Toll-like receptor. EDA stimulation of TLR4 was dependent upon co-expression of MD-2, a TLR4 accessory protein. Unlike LPS, the activity of EDA was heat-sensitive and persisted in the presence of the LPS-binding antibiotic polymyxin B and a potent LPS antagonist, E5564, which completely suppressed LPS activation of TLR4. These observations provided a mechanism by which EDA-containing fibronectin fragments promote expression of genes involved in the inflammatory response.