Abstract
Human basement membrane heparan sulfate proteoglycan (HSPG) perlecan binds and activates fibroblast growth factor (FGF)-2 through its heparan sulfate (HS) chains. Here we show that perlecans immunopurified from three cellular sources possess different HS structures and subsequently different FGF-2 binding and activating capabilities. Perlecan isolated from human umbilical arterial endothelial cells (HUAEC) and a continuous endothelial cell line (C11 STH) bound similar amounts of FGF-2 either alone or complexed with FGFRalpha1-IIIc or FGFR3alpha-IIIc. Both perlecans stimulated the growth of BaF3 cell lines expressing FGFR1b/c; however, only HUAEC perlecan stimulated those cells expressing FGFR3c, suggesting that the source of perlecan confers FGF and FGFR binding specificity. Despite these differences in FGF-2 activation, the level of 2-O- and 6-O-sulfation was similar for both perlecans. Interestingly, perlecan isolated from a colon carcinoma cell line that was capable of binding FGF-2 was incapable of activating any BaF3 cell line unless the HS was removed from the protein core. The HS chains also exhibited greater bioactivity after digestion with heparinase III. Collectively, these data clearly demonstrate that the bioactivity of HS decorating a single PG is dependent on its cell source and that subtle changes in structure including secondary interactions have a profound effect on biological activity.
Highlights
Human basement membrane heparan sulfate proteoglycan (HSPG) perlecan binds and activates fibroblast growth factor (FGF)-2 through its heparan sulfate (HS) chains
Perlecans derived from either human umbilical arterial endothelial cells (HUAEC), C11 STH, or WiDr were assessed for their ability to bind soluble FGF-2 after coating wells of a 96-well microtiter plate with perlecan (Fig. 1A) or by immunoprecipitation of the complex in conditioned medium with anti-perlecan antibodies (Fig. 1B)
This paper describes the biological and biochemical differences seen in the HS chains of perlecan immunopurified from two endothelial cell lines and one colon carcinoma cell line
Summary
Human basement membrane heparan sulfate proteoglycan (HSPG) perlecan binds and activates fibroblast growth factor (FGF)-2 through its heparan sulfate (HS) chains. Domains II–V are homologous to protein motifs found in epidermal growth factor, neural cell adhesion molecule (NCAM), and laminin, domain I is unique to perlecan and contains three potential heparan sulfate (HS) chain attachment sites Each of these domains has exhibited one or more. The ability to stimulate FGF-2 activity relies on the primary sequence, structure, and organization of HS, which is dependent on cell type and differentiation state [16, 28] This has been shown conclusively using HS from different cell and tissue types [29, 30]; little work has emerged on the individual contributions to growth factor binding and signaling by specific HSPGs derived from different cell types.
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