Dataset Information

Transforming growth factor-beta 1 increases internalization of basic fibroblast growth factor by smooth muscle cells: implication of cell-surface heparan sulphate proteoglycan endocytosis.

ABSTRACT: Basic fibroblast growth factor (bFGF) was internalized by smooth muscle cells (SMC) from pig aorta. Correlation between heparin inhibition of binding and late internalization (8 h) implicated low-affinity sites in bFGF internalization. Transforming growth factor-beta 1 (TGF-beta 1) induced a 38% increase in bFGF internalized between 4 and 8 h. While bFGF and/or TGF-beta 1 enhanced cell-surface proteoglycan synthesis, 35S-labelled proteoglycans of the extracellular matrix (ECM) were not affected. This might be explained by the different turnover rates displayed by the two populations of proteoglycans. Although bFGF and/or TGF-beta 1 induced a similar stimulation in cell-surface chondroitin sulphate/dermatan sulphate and heparan sulphate (HS) proteoglycan synthesis, only the turnover of HS proteoglycans was increased. Twice as much HS proteoglycan was internalized in the presence of TGF-beta 1 or bFGF. Furthermore, TGF-beta 1 induced a 43 +/- 12% increase in HS proteoglycan internalized in the presence of bFGF with a parallel 38% increase in bFGF internalization. Overall, the results indicated that bFGF bound to two HS proteoglycan populations. bFGF storage (70% of bFGF bound to SMC) was not affected by TGF-beta 1 under our conditions and involved ECM proteoglycans characterized by a low turnover. bFGF internalization up-regulated by TGF-beta 1 involved cell-surface HS proteoglycan characterized by a high turnover.

SUBMITTER: Berrou E

PROVIDER: S-EPMC1136013 | biostudies-other | 1995 Oct

REPOSITORIES: biostudies-other

ACCESS DATA

Similar Datasets

Project description:Heparan sulphate proteoglycans on cell surfaces have been shown to mediate the degradation or recycling of several ligands. Since the interaction with ligand may affect proteoglycan catabolism once the complex is internalized, this could alter the cellular pool of heparan sulphate chains, with possible consequences for heparan sulphate-mediated cellular processes. We have recently demonstrated that the specific binding of basic fibroblast growth factor (bFGF) to heparan sulphate chains prevents the glycosaminoglycan from being degraded by partially purified heparanases from Chinese hamster ovary (CHO) cells [Tumova and Bame (1997) J. Biol. Chem. 272, 9078-9085]. The present study examines the effect of bFGF on heparan sulphate catabolism in intact cells. The distribution and size of the heparan sulphate degradation products in CHO cells was analysed in the presence and absence of bFGF using pulse-chase protocols. Although heparan sulphate molecules and bFGF are internalized through the same pathway, even relatively high concentrations of the growth factor do not have any inhibitory effects on glycosaminoglycan degradation. However, the interaction with the growth factor alters the distribution of heparan sulphate-degradation products, presumably by preventing secretion of the short heparanase-derived species. Our findings show that most of the free and bFGF-bound heparan sulphate chains are destined for lysosomes, which would be consistent with a recent hypothesis that the primary role of proteoglycan-mediated internalization of the growth factor is to remove bFGF from its site of action at the cell surface. However, in the presence of bFGF, a fraction of intracellular, heparanase-degraded heparan sulphate chains is delivered to the nucleus, suggesting that the glycosaminoglycan accompanies the growth factor to the organelle. It may be important for bFGF activity that the growth factor is protected from proteolytic degradation by its interaction with heparan sulphate. This work demonstrates that the internalization of a ligand along with the proteoglycan can affect the sorting of heparan sulphate-degradation products in endosomes, and the ultimate destination of the short glycosaminoglycan. It also provides evidence that formation of heparan sulphate-ligand complexes may regulate the recycling and degradation of both ligands and heparan sulphate chains and, consequently, affect their biological activities.

Project description:RationaleAlveolar transforming growth factor (TGF)-?1 signaling and expression of TGF-?1 target genes are increased in patients with idiopathic pulmonary fibrosis (IPF) and in animal models of pulmonary fibrosis. Internalization and degradation of TGF-? receptor T?RI inhibits TGF-? signaling and could attenuate development of experimental lung fibrosis.ObjectivesTo demonstrate that after experimental lung injury, human syndecan-2 confers antifibrotic effects by inhibiting TGF-?1 signaling in alveolar epithelial cells.MethodsMicroarray assays were performed to identify genes differentially expressed in alveolar macrophages of patients with IPF versus control subjects. Transgenic mice that constitutively overexpress human syndecan-2 in macrophages were developed to test the antifibrotic properties of syndecan-2. In vitro assays were performed to determine syndecan-2-dependent changes in epithelial cell TGF-?1 signaling, TGF-?1, and T?RI internalization and apoptosis. Wild-type mice were treated with recombinant human syndecan-2 during the fibrotic phase of bleomycin-induced lung injury.Measurements and main resultsWe observed significant increases in alveolar macrophage syndecan-2 levels in patients with IPF. Macrophage-specific overexpression of human syndecan-2 in transgenic mice conferred antifibrotic effects after lung injury by inhibiting TGF-?1 signaling and downstream expression of TGF-?1 target genes, reducing extracellular matrix production and alveolar epithelial cell apoptosis. In vitro, syndecan-2 promoted caveolin-1-dependent internalization of TGF-?1 and T?RI in alveolar epithelial cells, which inhibited TGF-?1 signaling and epithelial cell apoptosis. Therapeutic administration of human syndecan-2 abrogated lung fibrosis in mice.ConclusionsAlveolar macrophage syndecan-2 exerts antifibrotic effects by promoting caveolin-1-dependent TGF-?1 and T?RI internalization and inhibiting TGF-?1 signaling in alveolar epithelial cells. Hence, molecules that facilitate T?RI degradation via endocytosis represent potential therapies for pulmonary fibrosis.

Dataset Information

Transforming growth factor-beta 1 increases internalization of basic fibroblast growth factor by smooth muscle cells: implication of cell-surface heparan sulphate proteoglycan endocytosis.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets