title: Cations modulate polysaccharide structure to determine FGF-FGFR signaling: a comparison of signaling and inhibitory polysaccharide interactions with FGF-1 in solution.
abstract: For heparan sulfate (HS) to bind and regulate the activity of proteins, the polysaccharide must present an appropriate sequence and adopt a suitable conformation. The conformations of heparin derivatives, as models of HS, are altered via a change in the associated cations, and this can drastically modify their FGF signaling activities. Here, we report that changing the cations associated with an N-acetyl-enriched heparin polysaccharide, from sodium to copper(II), converted it from supporting signaling through the fibroblast growth factor receptor (FGF-1-FGFR1c) tyrosine kinase signaling system to being inhibitory in a cell-based BaF3 assay. Nuclear magnetic resonance and synchrotron radiation circular dichroism (SRCD) spectroscopy demonstrated that the polysaccharide conformation differed in the presence of sodium or copper(II) cations. Electron paramagnetic resonance confirmed the environment of the copper(II) ion on the N-acetyl-enriched polysaccharide was distinct from that previously observed with intact heparin, which supported signaling. Secondary structures in solution complexes of polysaccharides with FGF-1 (which either supported signaling through FGFR1c or were inhibitory) were determined by SRCD. This allowed direct comparison of the two FGF-1-polysaccharide complexes in solution, containing identical molecular components and differing only in their cation content. Subtle structural differences were revealed, including a reduction in the level of disordered structure in the inhibitory complex.
authors.affiliation: School of Biological Sciences, University of Liverpool, Liverpool L69 7ZB, England.
authors.forename: Scott E
authors.initials: SE
authors.lastname: Guimond
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Rudd
authors.forename: Mark A
authors.initials: MA
authors.lastname: Skidmore
authors.forename: Alessandro
authors.initials: A
authors.lastname: Ori
authors.forename: Davide
authors.initials: D
authors.lastname: Gaudesi
authors.forename: Cesare
authors.initials: C
authors.lastname: Cosentino
authors.forename: Marco
authors.initials: M
authors.lastname: Guerrini
authors.forename: Ruth
authors.initials: R
authors.lastname: Edge
authors.forename: David
authors.initials: D
authors.lastname: Collison
authors.forename: Eric
authors.initials: E
authors.lastname: McInnes
authors.forename: Giangiacomo
authors.initials: G
authors.lastname: Torri
authors.forename: Jeremy E
authors.initials: JE
authors.lastname: Turnbull
authors.forename: David G
authors.initials: DG
authors.lastname: Fernig
authors.forename: Edwin A
authors.initials: EA
authors.lastname: Yates
mesh_terms: D000818:Animals; D002460:Cell Line; D003300:Copper / Q000737:chemistry* / Q000502:physiology; D016220:Fibroblast Growth Factor 1 / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000502:physiology*; D006497:Heparan Sulfate / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D051379:Mice; D017433:Protein Structure, Secondary; D051496:Receptor, Fibroblast Growth Factor, Type 1 / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D012964:Sodium / Q000737:chemistry* / Q000502:physiology; D012996:Solutions; D013329:Structure-Activity Relationship
chemical_list: D003300:Copper; D016220:Fibroblast Growth Factor 1; D006497:Heparan Sulfate; D051496:Receptor, Fibroblast Growth Factor, Type 1; D012964:Sodium; D012996:Solutions; C496349:Fgfr1 protein, mouse