No abstract

No abstract

Fibroblast growth factors are key proteins in many intercellular signaling networks. They normally remain attached to the extracellular matrix, which confers on them a considerable stability. The unrestrained accumulation of fibroblast growth factors in the extracellular milieu, either due to uncontrolled synthesis or enzymatic release, contributes to the pathology of many diseases. Consequently, the neutralization of improperly mobilized fibroblast growth factors is of clear therapeutic interest. In pursuing described rules to identify potential inhibitors of these proteins, gentisic acid, a plant pest-controlling compound, an aspirin and vegetarian diet common catabolite, and a component of many traditional liquors and herbal remedies, was singled out as a powerful inhibitor of fibroblast growth factors. Gentisic acid was used as a lead to identify additional compounds with better inhibitory characteristics generating a new chemical class of fibroblast growth factor inhibitors that includes the agent responsible for alkaptonuria. Through low and high resolution approaches, using representative members of the fibroblast growth factor family and their cell receptors, it was shown that this class of inhibitors may employ two different mechanisms to interfere with the assembly of the signaling complexes that trigger fibroblast growth factor-driven mitogenesis. In addition, we obtained evidence from in vivo disease models that this group of inhibitors may be of interest to treat cancer and angiogenesis-dependent diseases.The fibroblast growth factors (FGFs) 4 constitute one of the largest families of polypeptide growth factors. There are 22FGFs in humans and mice that differ significantly in both size (17-20 kDa) and sequence, although each contains a core homology region encompassing 120 -130 residues. Phylogenetic analyses suggest that the FGF genes can be arranged into seven subfamilies. All FGFs bind to heparin with high affinity (K d between 1-2 nM), except for the members of the FGF-19 subfamily (i.e.: FGF-15, -19, -21, and -23) that have little or no affinity for these glycosaminoglycans (1). Apart from the family comprising FGF-11 to FGF-14, FGFs exert their diverse biological actions by binding to a series of membrane tyrosine kinase receptors (FGFRs) that are encoded by four genes (2-4). For this reason the FGF family is currently considered to be constituted by 18 members.FGFs were first isolated in the 1980s from bovine brain extracts due to their mitogenic and angiogenic activities (5). The affinity of FGFs for heparin was recognized very soon after their discovery (6), although the physiological substrate for FGF in normal conditions is heparan sulfate, a proteoglycan whose glycoside moiety is a glycosaminoglycan like heparin. Although initially conceived as FGF traps and protectors, it was later shown that these proteoglycans also participate in FGF signaling, although they are not absolutely required (4,7,8).In addition to the effects on cell replication and angiogenesis observed initially, FGFs r...

Thioredoxin, a ubiquitous 12-kDa regulatory disulfide protein, was found to reduce disulfide bonds of allergens (convert SOS to 2 SH) and thereby mitigate the allergenicity of commercial wheat preparations. Allergenic strength was determined by skin tests with a canine model for food allergy. Statistically significant mitigation was observed with 15 of 16 wheat-sensitive animals. The allergenicity of the protein fractions extracted from wheat f lour with the indicated solvent was also assessed: the gliadins (ethanol) were the strongest allergens, followed by glutenins (acetic acid), albumins (water), and globulins (salt water). Of the gliadins, the ␣ and ␤ fractions were most potent, followed by the ␥ and types. Thioredoxin mitigated the allergenicity associated with the major protein fractions-i.e, the gliadins (including the ␣, ␤, and ␥ types) and the glutenins-but gave less consistent results with the minor fractions, the albumins and globulins. In all cases, mitigation was specific to thioredoxin that had been reduced either enzymically by NADPH and NADPthioredoxin reductase or chemically by dithiothreitol; reduced glutathione was without significant effect. As in previous studies, thioredoxin was particularly effective in the reduction of intramolecular (intrachain) disulfide bonds. The present results demonstrate that the reduction of these disulfide bonds is accompanied by a statistically significant decrease in allergenicity of the active proteins. This decrease occurs alongside the changes identified previously-i.e., increased susceptibility to proteolysis and heat, and altered biochemical activity. The findings open the door to the testing of the thioredoxin system in the production of hypoallergenic, moredigestible foods.

No abstract

The 3D structure of a complex formed by the acidic fibroblast growth factor (FGF‐1) and a specifically designed synthetic heparin hexasaccharide has been determined by NMR spectroscopy. This hexasaccharide can substitute natural heparins in FGF‐1 mitogenesis assays, in spite of not inducing any apparent dimerization of the growth factor. The use of this well defined synthetic heparin analogue has allowed us to perform a detailed NMR structural analysis of the heparin–FGF interaction, overcoming the limitations of NMR to deal with the high molecular mass and heterogeneity of the FGF‐1 oligomers formed in the presence of natural heparin fragments. Our results confirm that glycosaminoglycans induced FGF‐1 dimerization either in a cis or trans disposition with respect to the heparin chain is not an absolute requirement for biological activity.

No abstract

An effective strategy has been designed for the synthesis of oligosaccharides of different sizes structurally related to the regular region of heparin; this is illustrated by the preparation of hexasaccharide 1 and octasaccharide 2. This synthetic strategy provides the oligosaccharide sequence containing a D-glucosamine unit at the nonreducing end that is not available either by enzymatic or chemical degradation of heparin. It may permit, after slight modifications, the preparation of oligosaccharide fragments with different charge distribution as well. NMR spectroscopy and molecular dynamics simulations have shown that the overall structure of 1 in solution is a stable right-hand helix with four residues per turn. Hexasaccharide 1 and, most likely, octasaccharide 2 are, therefore, chemically well-defined structural models of naturally occurring heparin-like oligosaccharides for use in binding and biological activity studies. Both compounds 1 and 2 induce the mitogenic activity of acid fibroblast growth factor (FGF1), with the half-maximum activating concentration of 2 being equivalent to that of heparin. Sedimentation equilibrium analysis with compound 2 suggests that heparin-induced FGF1 dimerization is not an absolute requirement for biological activity.