Basic fibroblast growth factor is internalized through both receptor-mediated and heparan sulfate-mediated mechanisms

• Published in: The Journal of biological chemistry Vol. 267; no. 31; pp. 22156 - 22162
• Main Authors: ROGHANI, M, MOSCATELLI, D
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Biochemistry and Molecular Biology 05-11-1992
• Subjects: Analytical, structural and metabolic biochemistry; Animals; Binding, Competitive; Biological and medical sciences; Cattle; Down-Regulation; Endocytosis; Endothelium, Vascular - metabolism; Fibroblast Growth Factor 2 - metabolism; Fundamental and applied biological sciences. Psychology; Heparin - metabolism; Heparin Lyase; Heparitin Sulfate - metabolism; In Vitro Techniques; Polysaccharide-Lyases - pharmacology; Protein hormones. Growth factors. Cytokines; Proteins; Receptors, Fibroblast Growth Factor - metabolism; Fibroblast growth factor; Vertebrata; Membrane receptor; Mammalia; Radiolabelling; Internalization; Rodentia; Heparitin sulfate; Hamster; CHO cell line; Growth factor
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/s0021-9258(18)41648-1

Basic fibroblast growth factor (bFGF) was internalized at a rapid rate by Chinese hamster ovary (CHO) cells that do not express
significant numbers of high affinity receptors for bFGF as well as CHO cells that have been transfected with cDNA encoding
FGF receptor-1 or FGF receptor-2. Internalization of bFGF was completely blocked by the addition of 10 micrograms/ml heparin
in the parental CHO cells but only partially inhibited in cells expressing transfected FGF receptors. Bovine aortic endothelial
cells also exhibit heparin-sensitive and heparin-resistant internalization of bFGF. The internalization of bFGF through the
heparin-resistant pathway in CHO cells was efficiently competed by addition of unlabeled bFGF, was proportional to the number
of receptors expressed, and approached saturation, suggesting that the heparin-resistant internalization was due to high affinity
receptors. Internalization of bFGF through the heparin-sensitive pathway was not efficiently competed by unlabeled bFGF and
did not approach saturation at concentrations of bFGF up to 50 ng/ml, properties similar to the interaction of bFGF with low
affinity heparan sulfate binding sites on the cell surface. Internalization of bFGF in CHO cells not expressing FGF receptors
was inhibited by heparin, heparan sulfate, and dermatan sulfate, the same glycosaminoglycans that block binding to cell-surface
heparin sulfates. Internalization of bFGF in the parental CHO cells was inhibited at the same concentrations of heparin that
block binding to cell-surface heparan sulfates. Finally, inhibition of the sulfation of CHO cell heparan sulfates by the addition
of chlorate or digestion of CHO cell heparan sulfates with heparinase inhibited bFGF internalization in the parental CHO cells.
These results demonstrate that bFGF can be internalized through a direct interaction with cell-surface heparan sulfates. Thus,
there are two pathways for internalization of bFGF: high affinity receptor-mediated and heparan sulfate-mediated.