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 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.
Vallés
S
S
Functional Genomics Group, Division of Molecular and Genetic Medicine, Royal Hallamshire Hospital, University of Sheffield, Glossop Rd., Sheffield S10 2JF, United Kingdom.
Tsoi
C
C
Huang
W Y
WY
Wyllie
D
D
Carlotti
F
F
Askari
J A
JA
Humphries
M J
MJ
Dower
S K
SK
Qwarnström
E E
EE
D000595:Amino Acid Sequence; D002478:Cells, Cultured; D005347:Fibroblasts / Q000378:metabolism; D005353:Fibronectins / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D006497:Heparan Sulfate / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007375:Interleukin-1 / Q000378:metabolism; D007457:Iodine Radioisotopes; D008164:Luminescent Proteins / Q000378:metabolism; D011485:Protein Binding; D011869:Radioligand Assay; D017472:Receptors, Interleukin-1 / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism
D005353:Fibronectins; D049452:Green Fluorescent Proteins; D006497:Heparan Sulfate; D007375:Interleukin-1; D007457:Iodine Radioisotopes; D008164:Luminescent Proteins; D017472:Receptors, Interleukin-1; D011993:Recombinant Fusion Proteins