scholarly journals Heparin and heparan sulfate increase the radius of diffusion and action of basic fibroblast growth factor.

1990 ◽  
Vol 111 (4) ◽  
pp. 1651-1659 ◽  
Author(s):  
R Flaumenhaft ◽  
D Moscatelli ◽  
D B Rifkin
Keyword(s):  
Extracellular Matrix ◽  
Growth Factor ◽  
Heparan Sulfate ◽  
Fibroblast Growth Factor ◽  
Morphological Changes ◽  
Fibroblast Growth ◽  
Soluble Phase ◽  
Heparan Sulfates ◽  
Sulfate Complexes

The radius of diffusion of basic FGF (bFGF) in the presence and in the absence of the glycosaminoglycans heparin and heparan sulfate was measured. Iodinated 125I-bFGF diffuses further in agarose, fibrin, and on a monolayer of bovine aortic endothelial (BAE) cells in the presence of heparin than in its absence. Heparan sulfates affected the diffusion of 125I-bFGF in a manner similar to, though less pronounced than, heparin. When applied at the center of a monolayer of BAE cells, bFGF plus heparin stimulated morphological changes at a 10-fold greater radius than bFGF alone. These results suggest that bFGF-heparin and/or heparan sulfate complexes may be more effective than bFGF alone in stimulating cells located away from the bFGF source because the bFGF-glycosaminoglycan complex partitions into the soluble phase rather than binding to insoluble glycosaminoglycans in the extracellular matrix. Thus, the complex of bFGF and glycosaminoglycan may represent one of the active forms of bFGF in vivo.

scholarly journals Homodimerization Controls the Fibroblast Growth Factor 9 Subfamily's Receptor Binding and Heparan Sulfate-Dependent Diffusion in the Extracellular Matrix

2009 ◽  
Vol 29 (17) ◽  
pp. 4663-4678 ◽  
Author(s):  
Juliya Kalinina ◽  
Sara A. Byron ◽  
Helen P. Makarenkova ◽  
Shaun K. Olsen ◽  
Anna V. Eliseenkova ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Growth Factor ◽  
Heparan Sulfate ◽  
Fibroblast Growth Factor ◽  
Receptor Binding ◽  
Ex Vivo ◽  
Regulatory Control ◽  
Control Mechanisms ◽  
Fibroblast Growth ◽  
Heparin Binding

ABSTRACT Uncontrolled fibroblast growth factor (FGF) signaling can lead to human diseases, necessitating multiple layers of self-regulatory control mechanisms to keep its activity in check. Herein, we demonstrate that FGF9 and FGF20 ligands undergo a reversible homodimerization, occluding their key receptor binding sites. To test the role of dimerization in ligand autoinhibition, we introduced structure-based mutations into the dimer interfaces of FGF9 and FGF20. The mutations weakened the ability of the ligands to dimerize, effectively increasing the concentrations of monomeric ligands capable of binding and activating their cognate FGF receptor in vitro and in living cells. Interestingly, the monomeric ligands exhibit reduced heparin binding, resulting in their increased radii of heparan sulfate-dependent diffusion and biologic action, as evidenced by the wider dilation area of ex vivo lung cultures in response to implanted mutant FGF9-loaded beads. Hence, our data demonstrate that homodimerization autoregulates FGF9 and FGF20's receptor binding and concentration gradients in the extracellular matrix. Our study is the first to implicate ligand dimerization as an autoregulatory mechanism for growth factor bioactivity and sets the stage for engineering modified FGF9 subfamily ligands, with desired activity for use in both basic and translational research.

scholarly journals Ras Family GTPases Control Growth of Astrocyte Processes

1999 ◽  
Vol 10 (5) ◽  
pp. 1665-1683 ◽  
Author(s):  
Daniel Kalman ◽  
Stephen N. Gomperts ◽  
Stephen Hardy ◽  
Marina Kitamura ◽  
J. Michael Bishop
Keyword(s):  
Growth Factor ◽  
Fibroblast Growth Factor ◽  
Morphological Changes ◽  
Brain Slices ◽  
Dominant Negative ◽  
Fibroblast Growth ◽  
Control Growth ◽  
Cultured Astrocytes ◽  
Ras Family

Astrocytes in neuron-free cultures typically lack processes, although they are highly process-bearing in vivo. We show that basic fibroblast growth factor (bFGF) induces cultured astrocytes to grow processes and that Ras family GTPases mediate these morphological changes. Activated alleles of rac1 andrhoA blocked and reversed bFGF effects when introduced into astrocytes in dissociated culture and in brain slices using recombinant adenoviruses. By contrast, dominant negative (DN) alleles of both GTPases mimicked bFGF effects. A DN allele of Ha-ras blocked bFGF effects but not those of Rac1-DN or RhoA-DN. Our results show that bFGF acting through c-Ha-Ras inhibits endogenous Rac1 and RhoA GTPases thereby triggering astrocyte process growth, and they provide evidence for the regulation of this cascade in vivo by a yet undetermined neuron-derived factor.

scholarly journals Thrombin-induced release of active basic fibroblast growth factor- heparan sulfate complexes from subendothelial extracellular matrix

Blood ◽  
1993 ◽  
Vol 81 (12) ◽  
pp. 3324-3331 ◽  
Author(s):  
M Benezra ◽  
I Vlodavsky ◽  
R Ishai-Michaeli ◽  
G Neufeld ◽  
R Bar-Shavit
Keyword(s):  
Extracellular Matrix ◽  
Growth Factor ◽  
Heparan Sulfate ◽  
Fibroblast Growth Factor ◽  
Basic Fibroblast Growth Factor ◽  
Mitogenic Activity ◽  
Angiogenic Factor ◽  
Fibroblast Growth ◽  
Tgf Beta ◽  
Large Reservoir

Abstract The angiogenic factor, basic fibroblast growth factor (bFGF), is sequestered and protected by binding to heparan sulfate proteoglycans (HSPG) in the subendothelial extracellular matrix (ECM). Release of ECM- bound bFGF provides a novel mechanism for regulation of cell proliferation and neovascularization in normal and pathologic situations. Exposure of ECM to thrombin, the final activation product of the clotting cascade, resulted in release of high molecular weight HSPG-bFGF complex, as indicated by its immunoprecipitation with anti- bFGF antibodies, susceptibility to degradation by bacterial heparinase, and inhibition of its mitogenic activity in the presence of neutralizing anti-bFGF antibodies. The ECM-resident bFGF-HSPG complex was not released by thrombin in the presence of hirudin or antithrombin III, or by catalytically blocked thrombin preparations. A threefold to fivefold higher mitogenic activity was released by thrombin from ECM that was preheated (1 hour, 80 degrees C), as compared with native ECM. This difference is attributed to heat stable bFGF-HSPG complexes that are more readily released after heat treatment of the ECM and to activation and release of ECM-resident transforming growth factor-beta (TGF-beta) activity. Our results indicate that the large reservoir of proteolytic activity present in plasma in the form of prothrombin may participate in release from the subendothelial ECM of biologically active bFGF and TGF-beta, depending on the accessibility of thrombin. Thrombin may gain access to the subendothelium on clot formation after tissue injury and as a result of the conversion of prothrombin to thrombin induced by the ECM itself.

scholarly journals Thrombin-induced release of active basic fibroblast growth factor- heparan sulfate complexes from subendothelial extracellular matrix

Blood ◽  
1993 ◽  
Vol 81 (12) ◽  
pp. 3324-3331 ◽  
Author(s):  
M Benezra ◽  
I Vlodavsky ◽  
R Ishai-Michaeli ◽  
G Neufeld ◽  
R Bar-Shavit
Keyword(s):  
Extracellular Matrix ◽  
Growth Factor ◽  
Heparan Sulfate ◽  
Fibroblast Growth Factor ◽  
Basic Fibroblast Growth Factor ◽  
Mitogenic Activity ◽  
Angiogenic Factor ◽  
Fibroblast Growth ◽  
Tgf Beta ◽  
Large Reservoir

The angiogenic factor, basic fibroblast growth factor (bFGF), is sequestered and protected by binding to heparan sulfate proteoglycans (HSPG) in the subendothelial extracellular matrix (ECM). Release of ECM- bound bFGF provides a novel mechanism for regulation of cell proliferation and neovascularization in normal and pathologic situations. Exposure of ECM to thrombin, the final activation product of the clotting cascade, resulted in release of high molecular weight HSPG-bFGF complex, as indicated by its immunoprecipitation with anti- bFGF antibodies, susceptibility to degradation by bacterial heparinase, and inhibition of its mitogenic activity in the presence of neutralizing anti-bFGF antibodies. The ECM-resident bFGF-HSPG complex was not released by thrombin in the presence of hirudin or antithrombin III, or by catalytically blocked thrombin preparations. A threefold to fivefold higher mitogenic activity was released by thrombin from ECM that was preheated (1 hour, 80 degrees C), as compared with native ECM. This difference is attributed to heat stable bFGF-HSPG complexes that are more readily released after heat treatment of the ECM and to activation and release of ECM-resident transforming growth factor-beta (TGF-beta) activity. Our results indicate that the large reservoir of proteolytic activity present in plasma in the form of prothrombin may participate in release from the subendothelial ECM of biologically active bFGF and TGF-beta, depending on the accessibility of thrombin. Thrombin may gain access to the subendothelium on clot formation after tissue injury and as a result of the conversion of prothrombin to thrombin induced by the ECM itself.

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