title: Characterization of heparin and heparan sulfate domains binding to the long splice variant of platelet-derived growth factor A chain.
abstract: Platelet-derived growth factors (PDGFs) are homo- or heterodimers of two related polypeptides, known as A and B chains. The A chain exists as two splice variants due to the alternative usage of exons 6 (PDGF-AL, longer) and 7 (PDGF-AS, shorter). Exon 6 encodes an 18-amino acid sequence rich in basic amino acid residues, which has been implicated as a cell retention signal. Several lines of evidence indicate that the retention is due to binding of PDGF-AL to glycosaminoglycans, especially to heparan sulfate. We have analyzed the saccharide domains of smooth muscle cell-derived heparan sulfate involved in this interaction. Furthermore, we have employed selectively modified heparin oligosaccharides to elucidate the dependence of the binding on different sulfate groups and on fragment length. The shortest PDGF-AL binding domain consists of 6-8 monosaccharide units. Studies using selectively desulfated heparins and heparin fragments suggest that N-, 2-O-, and 6-O-sulfate groups all contribute to the interaction. Structural comparison of heparan sulfate oligosaccharides separated by affinity chromatography on immobilized PDGF-AL showed that the bound pool was enriched in -IdceA(2-OSO3)-GlcNSO3(6-OSO3)- disaccharide units. Furthermore, analogous separation of a partially O-desulfated heparin decamer preparation, using a highly selective nitrocellulose filter-trapping system, yielded a PDGF-AL-bound fraction in which more than half of the disaccharide units had the structure -IdceA(2-OSO3)-GlcNSO3(6-OSO3)-. Our results suggest that the interaction between PDGF-AL and heparin/heparan sulfate is mediated via N-sulfated saccharide domains containing both 2-O- and 6-O-sulfate groups.
authors.affiliation: Department of Medical and Physiological Chemistry, Uppsala University, Biomedical Center, S-75123 Uppsala, Sweden.
authors.forename: E
authors.initials: E
authors.lastname: Feyzi
authors.forename: F
authors.initials: F
authors.lastname: Lustig
authors.forename: G
authors.initials: G
authors.lastname: Fager
authors.forename: D
authors.initials: D
authors.lastname: Spillmann
authors.forename: U
authors.initials: U
authors.lastname: Lindahl
authors.forename: M
authors.initials: M
authors.lastname: Salmivirta
mesh_terms: D000818:Animals; D001665:Binding Sites; D002236:Carbohydrate Conformation; D002846:Chromatography, Affinity; D004187:Disaccharides / Q000737:chemistry; D006025:Glycosaminoglycans / Q000378:metabolism; D006493:Heparin / Q000378:metabolism*; D006497:Heparan Sulfate / Q000378:metabolism*; D009844:Oligosaccharides / Q000737:chemistry; D010982:Platelet-Derived Growth Factor / Q000235:genetics / Q000378:metabolism*; D013552:Swine
chemical_list: D004187:Disaccharides; D006025:Glycosaminoglycans; D006493:Heparin; D006497:Heparan Sulfate; D009844:Oligosaccharides; D010982:Platelet-Derived Growth Factor; C075278:platelet-derived growth factor A