Cations modulate polysaccharide structure to determine FGF-FGFR signaling: a comparison of signaling and inhibitory polysaccharide interactions with FGF-1 in solution.
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.
Guimond
Scott E
SE
School of Biological Sciences, University of Liverpool, Liverpool L69 7ZB, England.
Rudd
Timothy R
TR
Skidmore
Mark A
MA
Ori
Alessandro
A
Gaudesi
Davide
D
Cosentino
Cesare
C
Guerrini
Marco
M
Edge
Ruth
R
Collison
David
D
McInnes
Eric
E
Torri
Giangiacomo
G
Turnbull
Jeremy E
JE
Fernig
David G
DG
Yates
Edwin A
EA
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
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