Pigment Epithelium-derived Factor (PEDF) Shares Binding Sites in Collagen with Heparin/Heparan Sulfate Proteoglycans

The fibroblast growth factor-2 (FGF-2) low-affinity binding sites, heparan sulfate proteoglycans (HSPGs), function as modulators of FGF-2 activity. It is noteworthy that HSPG binding protects FGF-2 from denaturation and proteolytic degradation, provides a matrix-bound or cell-surface reservoir of this factor for the cells and is required for the activation of FGF high-affinity receptors. In our study we investigated the biological meaning of FGF-2 internalization mediated through its low-affinity binding sites, HSPGs. Using as model system L6 myoblasts lacking endogenous FGF receptors (FGFRs), we demonstrated that these cells internalize FGF-2 efficiently through an HSPG-mediated pathway. FGF-2 internalization occurring through HSPGs was paralleled by an increase in the activity of urokinase plasminogen activator (u-PA). The u-PA-inducing activity of FGF-2 was strictly correlated to its internalization, as chlorate treatment, which causes a strong inhibition of FGF-2 internalization, abrogated the u-PA-inducing activity of FGF-2. In addition, expression of functional FGF high-affinity receptors (FGFR-1) did not enhance u-PA in L6 myoblasts upon FGF-2 stimulation. According to our results we propose that FGF-2 internalization mediated through HSPGs may transduce FGF-2 signalling such as u-PA-activity stimulation. Thus, HSPGs may act as direct transducers of FGF signalling and indeed, different FGF-signalling pathways must exist.

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Identification of Common and Specific Growth Factor Binding Sites in Heparan Sulfate Proteoglycans†

Biochemistry ◽

10.1021/bi050241p ◽

2005 ◽

Vol 44 (36) ◽

pp. 12203-12213 ◽

Cited By ~ 31

Author(s):

Chia Lin Chu ◽

Adrienne L. Goerges ◽

Matthew A. Nugent

Keyword(s):

Growth Factor ◽

Heparan Sulfate ◽

Binding Sites ◽

Specific Growth ◽

Heparan Sulfate Proteoglycans ◽

Factor Binding ◽

Specific Growth Factor

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Localization of anticoagulantly active heparan sulfate proteoglycans in vascular endothelium: antithrombin binding on cultured endothelial cells and perfused rat aorta.

The Journal of Cell Biology ◽

10.1083/jcb.111.3.1293 ◽

1990 ◽

Vol 111 (3) ◽

pp. 1293-1304 ◽

Cited By ~ 152

Author(s):

A I de Agostini ◽

S C Watkins ◽

H S Slayter ◽

H Youssoufian ◽

R D Rosenberg

Keyword(s):

Extracellular Matrix ◽

Endothelial Cells ◽

Protease Inhibitor ◽

Heparan Sulfate ◽

Binding Sites ◽

Rat Aorta ◽

Linear Increase ◽

Heparan Sulfate Proteoglycans ◽

Vasa Vasorum

We have studied the interaction of 125I-antithrombin (125I-AT) with microvascular endothelial cells (RFPEC) to localize the cellular site of anticoagulantly active heparan sulfate proteoglycans (HSPG). The radiolabeled protease inhibitor bound specifically to the above HSPG with a Kd of approximately 50 nM. Confluent monolayer RFPEC cultures exhibited a linear increase in the amount of AT bound per cell for up to 16 d, whereas suspension RFPEC cultures possessed a constant number of protease inhibitor binding sites per cell for up to 5 d. These results suggest that monolayer RFPEC cultures secrete anticoagulantly active HSPG, which then accumulate in the extracellular matrix. This hypothesis was confirmed by quantitative light and EM level autoradiography which demonstrated that the AT binding sites are predominantly located in the extracellular matrix with only small quantities of protease inhibitor complexed to the cell surface. We have also pinpointed the in vivo position of anticoagulantly active HSPG within the blood vessel wall. Rat aortas were perfused, in situ, with 125I-AT, and bound labeled protease inhibitor was localized by light and EM autoradiography. The anticoagulantly active HSPG were concentrated immediately beneath the aortic and vasa vasorum endothelium with only a very small extent of labeling noted on the luminal surface of the endothelial cells. Based upon the above data, we propose a model whereby luminal and abluminal anticoagulantly active HSPG regulate coagulation mechanism activity.

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Characterization and Localization of Pigment Epithelium-Derived Factor Binding Sites in the Bovine Retina

New Insights Into Retinal Degenerative Diseases ◽

10.1007/978-1-4615-1355-1_15 ◽

2001 ◽

pp. 127-133

Author(s):

Maria S. Aymerich ◽

Alfredo Martinez ◽

S. Patricia Becerra

Keyword(s):

Binding Sites ◽

Pigment Epithelium ◽

Factor Binding ◽

Bovine Retina ◽

Pigment Epithelium Derived Factor

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Localization of cell-surface and basement-membrane heparan-sulfate proteoglycans using the malaria circumsporozoite protein

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100169201 ◽

1994 ◽

Vol 52 ◽

pp. 294-295

Author(s):

U. Frevert ◽

S. Sinnis ◽

C. Cerami ◽

V. Nussenzweig

Keyword(s):

Heparan Sulfate ◽

Protein A ◽

Kidney Tissue ◽

Plasmodium Species ◽

Its Region ◽

Basement Membranes ◽

Heparan Sulfate Proteoglycans ◽

Infected Mosquito ◽

Complement Components ◽

Region Ii

Malaria sporozoites, which invade hepatocytes within minutes after transmission by an infected mosquito, are covered with the circumsporozoite (CS) protein, which in all Plasmodium species contains the conserved region II-plus. This region is also found as a cell-adhesive motif in a variety of host proteins like thrombospondin, properdin and the terminal complement components.The CS protein with its region II-plus specifically binds to heparan sulfate proteoglycans (HSPG) on the basolateral surface of hepatocytes in the space of Disse (FIG. 1), to certain basolateral cell membranes and basement membranes of the kidney (FIG. 2) as well as to heparin in the granules of connective tissue mast cells. The distribution of the HSPG receptors for the CS protein was examined by incubation of Lowicryl K4M or LR White sections of liver and kidney tissue with the recombinant CS ligand, whose binding sites were detected with a monoclonal anti-CS antibody and protein A gold.

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