Ability of different chemically modified heparins to potentiate the biological activity of heparin-binding growth factor 1: lack of correlation with growth factor binding.
A range of chemically modified heparins was examined for their ability to bind heparin-binding growth factor 1 (HBGF-1; acidic fibroblast growth factor) and potentiate the in vitro mitogenic and neurotrophic activity of HBGF-1. It was found that carboxyl-reduced heparin bound HBGF-1 as effectively as the native heparin molecule. Totally desulfated heparin and N-desulfated heparin lack HBGF-1-binding capacity, and substitution of the exposed amino group with acetyl or acetoacetyl groups only partially restored binding capacity, indicating that N-sulfates only play a limited role in growth factor binding. However, the failure of totally desulfated, N-resulfated heparin to interact with HBGF-1 demonstrated that N-sulfates alone are insufficient and ester sulfates are absolutely essential for HBGF-1 binding. In contrast, the ability of the modified heparins to potentiate the mitogenic activity of HBGF-1 correlated only to a limited extent with their affinity for HBGF-1. Thus, the carboxyl-reduced molecule which displayed similar affinity for HBGF-1 as native heparin was consistently less potent in augmenting mitogenesis. Similarly, the N-acetylated and the N-acetoacetylated species, which had much lower affinity for HBGF-1 than the carboxyl-reduced molecule, conferred similar biological activity to HBGF-1 whereas N-desulfated heparin, which was unable to bind growth factor, potentiated the mitogenic activity of HBGF-1 for both 3T3 and HUVE cells. In contrast, the neurotrophic activity of HBGF-1 was potentiated by modified heparin species which failed to bind HBGF-1 and were without activity in the mitogenic assays.(ABSTRACT TRUNCATED AT 250 WORDS)
Belford
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DA
Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra.
Hendry
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IA
Parish
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CR
D016475:3T3 Cells; D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002642:Chick Embryo; D004357:Drug Synergism; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects; D016220:Fibroblast Growth Factor 1 / Q000008:administration & dosage* / Q000378:metabolism; D006493:Heparin / Q000008:administration & dosage* / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D051379:Mice; D011485:Protein Binding; D013329:Structure-Activity Relationship
D016220:Fibroblast Growth Factor 1; D006493:Heparin