Heparin-binding growth factor-1 (HBGF-1) is an angiogenic polypeptide mitogen for mesoderm- and neuroectoderm-derived cells in vitro and remains biologically active after truncation of the amino-terminal domain (HBGF-1 alpha) of the HBGF-1 beta precursor. Polymerase chain reaction mutagenesis and prokaryotic expression systems were used to prepare a mutant of HBGF-1 alpha lacking a putative nuclear translocation sequence (amino acid residues 21 to 27; HBGF-1U). Although HBGF-1U retains its ability to bind to heparin, HBGF-1U fails to induce DNA synthesis and cell proliferation at concentrations sufficient to induce intracellular receptor-mediated tyrosine phosphorylation and c-fos expression. Attachment of the nuclear translocation sequence from yeast histone 2B at the amino terminus of HBGF-1U yields a chimeric polypeptide (HBGF-1U2) with mitogenic activity in vitro and indicates that nuclear translocation is important for this biological response.

Fibroblast growth factor 1 (FGF-1) is a potent angiogenic and neurotrophic factor whose structure lacks a classical signal sequence for secretion. Although the initiation of these biological activities involves the interaction between FGF-1 and cell surface receptors, the mechanism responsible for the regulation of FGF-1 secretion is unknown. We report that murine NIH 3T3 cells transfected with a synthetic gene encoding FGF-1 secrete FGF-1 into their conditioned medium in response to heat shock. The form of FGF-1 released by NIH 3T3 cells in response to increased temperature (42C, 2 hr) in vitro is not biologically active and does not associate with either heparin or the extracellular NIH 3T3 monolayer matrix. However, it was possible to derive biologically active FGF-1 from the conditioned medium of heat-shocked NIH 3T3 cell transfectants by ammonium sulfate fractionation. The form of FGF-1 exposed by ammonium sulfate fractionation is similar in size to cytosolic FGF-1 and can bind and be eluted from immobilized heparin similarly to the recombinant human FGF-1 polypeptide. Further, the release of FGF-1 by NIH 3T3 cell transfectants in response to heat shock is reduced signifi.-cantly by both actinomycin D and cycloheximide. These data indicate that increased temperature may upregulate the expression of a factor responsible for the secretion of FGF-1 as a biologically inactive complex that requires an activation step to exhibit the biological activity of the extracellular polypeptide mitogen.structures, and tightly regulated activation mechanism (reviewed in ref. 9). Indeed, members of the HSP70 family have many functions (9), including the ability to associate with polypeptides known to be directed to specific cellular organelles such as the nucleus (10), nucleolus (11), mitochondria (12,13,14), microsomes (15), endoplasmic reticulum (13) (22), and polyoma middle T antigen (23,24). While the expression and translocation of HSP70 between organelles is cell cycle-specific (25) and has been reported to be associated with physiologic vascular stress (26-28), the function of these stress proteins in diseases associated with fever, inflammation, cellular hypertrophy, or programmed cell death (29-32) remains unknown. Because (i) the expression of FGF-1 is exaggerated in inflamed cartilage in vivo (33), (ii) FGF-1 is a potent regulator of cellular hypertrophy (34), and (iii) programmed cell death has been proposed as a mechanism for the release ofcytosolic FGF-1 (1-3, 8), we examined the role of heat-induced stress as a potential mechanism for the secretion ofFGF-1 in vitro and report here that the release of cytosolic FGF-1 is regulated by temperature in vitro.The fibroblast growth factor (FGF) family of heparin-binding proteins is composed of two prototype members, FGF-1 (acidic) and FGF-2 (basic), and five related proteins (1). The FGF prototype structures are unique among the members of the FGF family because, unlike the majority of FGF-related polypeptides, the FGF prototypes lack a classical signal peptid...

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The goals of this study were 2-fold: 1) to determine whether stimulation of Eph B4 receptors promotes microvascular endothelial cell migration and/or proliferation, and 2) to elucidate signaling pathways involved in these responses. The human endothelial cells used possessed abundant Eph B4 receptors with no endogenous ephrin B2 expression. Stimulation of these receptors with ephrin B2/Fc chimera resulted in dose-and timedependent phosphorylation of Akt. These responses were inhibited by LY294002 and ML-9, blockers of phosphatidylinositol 3-kinase (PI3K) and Akt, respectively. Eph B4 receptor activation increased proliferation by 38%, which was prevented by prior blockade with LY294002, ML-9, and inhibitors of protein kinase G (KT5823) and MEK (PD98059). Nitrite levels increased over 170% after Eph B4 stimulation, indicating increased nitric oxide production. Signaling of endothelial cell proliferation appears to be mediated by a PI3K/ Akt/endothelial nitric-oxide synthase/protein kinase G/mitogen-activated protein kinase cascade. Stimulation with ephrin B2 also increased migration by 63% versus controls. This effect was inhibited by blockade with PP2 (Src inhibitor), LY294002 or ML-9 but was unaffected by the PKG and MEK blockers. Eph B4 receptor stimulation increased activation of both matrix metalloproteinase-2 and -9. The results from these studies indicate that Eph B4 stimulates migration and proliferation and may play a role in angiogenesis.

The prototype members of the heparin-binding fibroblast growth factor (FGF) family, acidic FGF (FGF-1) and basic FGF (FGF-2), are among the growth factors that act directly on vascular cells to induce endothelial cell growth and angiogenesis. In vivo, the role of the FGF prototypes in vascular pathology has been difficult to determine. We report here the introduction, by direct gene transfer into porcine arteries, of a eukaryotic expression vector encoding a secreted form of FGF-1. This somatic transgenic model defines gene function in the arterial wall in vivo. FGF-1 expression induced intimal thickening in porcine arteries 21 days after gene transfer, in contrast to control arteries transduced with an Escherichia coli beta-galactosidase gene. Where there was substantial intimal hyperplasia, neocapillary formation was detected in the expanded intima. These findings suggest that FGF-1 induces intimal hyperplasia in the arterial wall in vivo and, through its ability to stimulate angiogenesis in the neointima, FGF-1 could stimulate neovascularization of atherosclerotic plaques. Potentially, gene transfer of FGF-1 could also be used as a genetic intervention to improve blood flow to ischaemic tissues in selected clinical settings.