Recruitment of a heparan sulfate subunit to the interleukin-1 receptor complex. Regulation by fibronectin attachment

In this study, we identified an adhesion-regulated subunit of the interleukin-1 (IL-1) receptor complex. Transfection of fibroblasts with an IL-1 receptor-EGFP construct showed that the fusion protein was located at focal adhesions in cells attaching to fibronectin. Fibronectin attachment caused enh...

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Bibliographic Details
Published in:The Journal of biological chemistry 1999-07, Vol.274 (29), p.20103-20109
Main Authors: Vallés, S, Tsoi, C, Huang, W Y, Wyllie, D, Carlotti, F, Askari, J A, Humphries, M J, Dower, S K, Qwarnström, E E
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Cells, Cultured
Fibroblasts - metabolism
Fibronectins - metabolism
Green Fluorescent Proteins
Heparitin Sulfate - chemistry
Heparitin Sulfate - metabolism
Humans
Interleukin-1 - metabolism
Iodine Radioisotopes
Luminescent Proteins - metabolism
Protein Binding
Radioligand Assay
Receptors, Interleukin-1 - metabolism
Recombinant Fusion Proteins - metabolism
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Summary:In this study, we identified an adhesion-regulated subunit of the interleukin-1 (IL-1) receptor complex. Transfection of fibroblasts with an IL-1 receptor-EGFP construct showed that the fusion protein was located at focal adhesions in cells attaching to fibronectin. Fibronectin attachment caused enhancement in endogenous IL-1 type I receptor levels from on average 2500 to 4300 receptors/cell. In addition, matrix attachment resulted in a decrease in binding affinity (Ka) from 1.0 x 10(9) (M-1) to 5.6 x 10(8) (M-1), due to a 2-fold reduction in association rate constant. The adhesion-mediated effects were reversed by soluble heparin. Cross-linking experiments showed that in cells attached to fibronectin, 50-70% of the radiolabeled IL-1 was associated with a heparinase sensitive, high molecular mass component of about 300 kDa, with a core protein of 80-90 kDa. Formation of the complex was dependent on cell interaction with the heparin binding region in fibronectin and required IL-1/type I IL-1 receptor binding. This report demonstrates the recruitment of a heparan sulfate to the IL-1 receptor complex, following attachment to fibronectin, which correlates with alterations in receptor function. The data suggest that the heparan sulfate constitutes an attachment regulated component of the IL-1 receptor complex with the role of mediating matrix regulation of IL-1 responses.
ISSN:0021-9258
DOI:10.1074/jbc.274.29.20103