title: TSG-6, an arthritis-associated hyaluronan binding protein, forms a stable complex with the serum protein inter-alpha-inhibitor.
abstract: TSG-6 is a secreted 35-kDa glycoprotein, inducible by TNF and IL-1. The N-terminal portion of TSG-6 shows sequence homology to members of the cartilage link protein family of hyaluronan binding proteins. The C-terminal half of TSG-6 contains a so-called CUB domain, characteristic for developmentally regulated proteins. High levels of TSG-6 protein are found in the synovial fluid of patients with rheumatoid arthritis and some other arthritic diseases. Here we show that TSG-6 readily formed a complex with a protein present in human, bovine, rabbit, and mouse serum. This complex was stable during SDS-PAGE under reducing conditions, and in the presence of 8 M urea. The protein that binds TSG-6 was purified from human serum and identified as inter-alpha-inhibitor (I alpha I) by N-terminal microsequencing. Microsequencing of the complex itself revealed the presence of TSG-6 and two of the three polypeptide chains of I alpha I (bikunin and HC2). Experiments with recombinant TSG-6 and I alpha I purified from human serum showed that the TSG-6/I alpha I complex is rapidly formed even in the apparent absence of other proteins at 37 degrees C, but not at 4 degrees C. The TSG-6/I alpha I complex was cleaved by chondroitin sulfate ABC lyase, suggesting that cross-linking by chondroitin sulfate is required for the stability of the complex.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Microbiology, New York University Medical Center, New York 10016.
authors.forename: H G
authors.initials: HG
authors.lastname: Wisniewski
authors.forename: W H
authors.initials: WH
authors.lastname: Burgess
authors.forename: J D
authors.initials: JD
authors.lastname: Oppenheim
authors.forename: J
authors.initials: J
authors.lastname: Vilcek
mesh_terms: D000510:Alpha-Globulins / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001168:Arthritis / Q000378:metabolism; D015153:Blotting, Western; D002417:Cattle; D015815:Cell Adhesion Molecules / Q000097:blood / Q000302:isolation & purification / Q000378:metabolism*; D002478:Cells, Cultured; D002809:Chondroitin Sulfates / Q000378:metabolism; D002846:Chromatography, Affinity; D003432:Cross-Linking Reagents; D006023:Glycoproteins / Q000378:metabolism*; D006025:Glycosaminoglycans / Q000378:metabolism; D006801:Humans; D006820:Hyaluronic Acid / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D011233:Precipitin Tests; D011817:Rabbits; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D014361:Trypsin Inhibitors / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D000510:Alpha-Globulins; D015815:Cell Adhesion Molecules; D003432:Cross-Linking Reagents; D006023:Glycoproteins; D006025:Glycosaminoglycans; D011994:Recombinant Proteins; C072273:TNFAIP6 protein, human; C513057:Tnfaip6 protein, mouse; D014361:Trypsin Inhibitors; C011877:inter-alpha-inhibitor; D006820:Hyaluronic Acid; D002809:Chondroitin Sulfates