Receptor- and heparin-binding domains of basic fibroblast growth factor.

Abstract

Two functional domains in the primary structure of basic fibroblast growth factor (FGF) have been identified on the basis of their ability to interact with the FGF receptor, bind radiolabeled heparin, and modulate the cellular response to FGF. Peptides derived from these two functional domains can act as partial agonists and antagonists in biological assays of FGF activity. Peptides related to the sequences of FGF-(24-68)-NH2 and FGF-(106-115)-NH2 inhibit thymidine incorporation into 3T3 fibroblasts when they are stimulated by FGF but have no effect when the cells are treated with either platelet-derived growth factor or epidermal growth factor. They also possess partial agonist activity and can stimulate DNA synthesis when tested in the absence of exogenous FGF. The active peptides have no effect on the binding of epidermal growth factor to its receptor on A431 cells and they can modulate the effects of FGF, but not fibronectin, on endothelial cell adhesion. The results suggest the possibility of designing specific analogs of FGF that are capable of inhibiting the biological effects of FGF.The molecular characterization of basic and acidic fibroblast growth factors (FGFs) has confirmed the existence of two classes of closely related angiogenic factors and helped establish the identity of an unusual family of mitogens (1-7). Acidic and basic FGFs exist in several molecular forms that are products of proteolytic processing at homologous sites (1)(2)(3)8). Both growth factors stimulate a wide spectrum of target cells derived from the primary and secondary mesenchyme as well as from the neural crest. The growth factors bind immobilized heparin with an unusually high affinity, a characteristic that has been exploited for their isolation and characterization from many tissues (4, 9). Because both FGFs also have the capacity to stimulate neovascularization (1-4), their physiological functions have been associated with reproduction, growth, and development. The possible identity of FGF-related proteins with the tumor angiogenic factor activities described by Folkman (10) has suggested that this family of mitogens may also play a critical role in several pathophysiological processes including the growth of tumors, diabetic proliferative retinopathies, and the woundhealing response. The ability of basic FGF to stimulate nerve regeneration (11) and to induce a neovascular response in the chicken chorioallantoic membrane (12), the rat brain (13), the kidney capsule (14), and the carotid artery (unpublished work) has suggested a possible therapeutic application of FGFs in stimulating tissue regeneration, the recovery from episodes of ischemia, and tissue transplantation.The identification of specific functional domains in the primary structure of basic FGF was examined as a first step in the design of recombinant analogs of basic FGF that have modified heparin-binding activity, increased biological activity, and/or antagonist activity. The results presented here identify two peptide sequences of interest (Fig. 1). M...

The extracellular regulation of growth factor action.

“…Mechanisms exist both to maintain certain growth factors at the site of their release and to allow other species to act in locations some distance away from their release. (Massague, 1990) (Baird et al, 1988;Higashiyama, 1991;Raines and Ross, 1992). Release from these sites often occurs in a regulated manner.…”

A distinct basic fibroblast growth factor (FGF-2)/FGF receptor interaction distinguishes urokinase-type plasminogen activator induction from mitogenicity in endothelial cells.

“…The primary binding site is discontinuous in amino acid sequence and interacts with the receptor with high affinity (Kd -5 x 10-9 M). The secondary binding site on FGF-2 requires the presence of heparin, has a 250-fold lower affinity for FGFR (Kd -1 X 10-6 M), and is composed of the amino acid residues 106-115 that comprise the formerly known receptor binding loop (Baird et al, 1988). Interaction of FGFR with both low and high affinity FGF-2 surfaces in a stoichiometry of 2FGFR: 1FGF-2 is hypothesized to facilitate receptor dimerization, leading to a mitogenic response (Springer et al, 1994).…”

“…Similar results were obtained when more specific FGF-2 and FGFR antagonists were used. The synthetic peptide FGF-2(112-155) interacts with FGF receptors and acts as a FGF-2 antagonist in 3T3 mouse fibroblasts (Baird et al, 1988). Accordingly, FGF-2(112-155) inhibits 125I-FGF-2/FGFR binding and FGF-2 mitogenic activity also in GM 7373 cells (Figure 2).…”

“…However, the peptide had no effect on the uPA-inducing activity of the growth factor (Figure 2B). No antagonist activity was exerted by the control peptide FGF-2(130-155) (Baird et al, 1988) in receptor binding, cell proliferation, and uPA-production assays (Figure 2). Finally, the recombinant extracellular domain of FGFR-1 inhibited FGF-2 mitogenic activity and 125I1…”

Identification of FGF receptor-binding peptides for cancer gene therapy

“…Molecules previously identified that bind FGF receptors include members of the FGF family, peptide fragments of FGF2, 23,24 peptide sequences with homology to fragments of FGF2, 25 and completely synthetic ligands. 22,26 Sequences of FGF1 -23 were obtained from the database of the National Center for Biotechnology Information ( Bethesda, MD. )…”