title: CD44, a cell surface chondroitin sulfate proteoglycan, mediates binding of interferon-gamma and some of its biological effects on human vascular smooth muscle cells.
abstract: Several cytokines and growth factors act on cells after their association with the glycosaminoglycan (GAG) moiety of cell surface proteoglycans (PGs). Interferon-gamma (IFN-gamma) binds to GAG; however, the relevance of this interaction for the biological activity of IFN-gamma on human cells remains to be established. Human arterial smooth muscle cells (HASMC), the main cells synthesizing PG in the vascular wall, respond markedly to IFN-gamma. We found that treatment of HASMC with chondroitinase ABC, an enzyme that degrades chondroitin sulfate GAG, reduced IFN-gamma binding by more than 50%. This treatment increased the affinity of 125I-IFN-gamma for cells from a Kd value of about 93 nM to a Kd value of about 33 nM. However, the total binding was reduced from 9. 3 +/- 0.77 pmol/microg to 3.0 +/- 0.23 pmol/mg (n = 4). Interestingly, pretreatment with chondroitinase ABC reduced significantly the cellular response toward IFN-gamma. The interaction of IFN-gamma with chondroitin sulfate GAG was confirmed by affinity chromatography of isolated cell-associated 35S-, 3H-labeled PG on a column with immobilized IFN-gamma. The cell-associated PG that binds to IFN-gamma was a chondroitin sulfate PG (CSPG). This CSPG had a core protein of approximately 110 kDa that was recognized by anti-CD44 antibodies on Western blots. High molecular weight complexes between IFN-gamma and chondroitin 6-sulfate were observed in gel exclusion chromatography. Additions of chondroitin 6-sulfate to cultured HASMC antagonized the antiproliferative effect and expression of major histocompatibility complex II antigens induced by IFN-gamma. These results indicate that IFN-gamma binds with low affinity to the chondroitin sulfate GAG moiety of the cell surface CSPG receptor CD44. This interaction may increase the local concentration of IFN-gamma at the cell surface, thus facilitating its binding to high affinity receptors and modulating the ability of IFN-gamma to signal a cellular response.
authors.affiliation: Wallenberg Laboratory for Cardiovascular Research, Göteborg University, Göteborg 413 45, Sweden. Eva.Hurt@wlab.wall.gu.se
authors.forename: E
authors.initials: E
authors.lastname: Hurt-Camejo
authors.forename: B
authors.initials: B
authors.lastname: Rosengren
authors.forename: P
authors.initials: P
authors.lastname: Sartipy
authors.forename: K
authors.initials: K
authors.lastname: Elfsberg
authors.forename: G
authors.initials: G
authors.lastname: Camejo
authors.forename: L
authors.initials: L
authors.lastname: Svensson
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D002809:Chondroitin Sulfates / Q000494:pharmacology; D002846:Chromatography, Affinity; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D018960:Hyaluronan Receptors / Q000378:metabolism*; D007371:Interferon-gamma / Q000378:metabolism*; D007700:Kinetics; D051379:Mice; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D011817:Rabbits; D012995:Solubility; D013499:Surface Properties
chemical_list: D018960:Hyaluronan Receptors; D007371:Interferon-gamma; D002809:Chondroitin Sulfates