Heparin protects basic and acidic FGF from inactivation

Abstract

The ability of heparin or that of hexuronyl hexosaminoglycan sulfate (HHS-4) to protect basic or acidic fibroblast growth factor (FGF) from acid or heat inactivation has been analyzed. Both freshly prepared basic and acidic FGF stimulate the growth of baby hamster kidney (BHK-21) cells exposed to medium supplemented with transferrin and insulin. Freshly prepared basic FGF was 10 fold more potent than acidic FGF. The addition of heparin to the medium decreased the potency of basic FGF while it potentiated that of acidic FGF. Upon storage of FGF at -80 degrees C, a decline in potency of both basic and acidic FGF was observed. Heparin, when added to the medium, potentiated their activities, which became similar to that of freshly prepared basic FGF. In order to test whether heparin could protect basic or acidic FGF from inactivation, both mitogens were exposed to acid conditions (1% trifluoroacetic acid, pH 1.08, 2 h) or heat (65 degrees C, 5 min) which inactivate basic or acidic FGF. When exposed to such treatment in the presence of heparin or HHS-4, basic and acidic FGF retained their potency. The effect of heparin and HHS-4 on the bioactivity of basic and acidic FGF is truly of a protective nature, since they had no effect when added after inactivation of the mitogens. Potentiation of the bioactivity of the protected mitogens or of the inactivated one could only be observed when cells were exposed to high heparin or HHS-4 concentrations. This indicates that heparin and HHS-4, in addition to protecting FGF from inactivation, also acts at another locus, as yet unidentified.

Experimental support for the foldability–function tradeoff hypothesis: Segregation of the folding nucleus and functional regions in fibroblast growth factor‐1

“…[37][38][39] Furthermore, the competent signal transduction complex of FGF-1 involves a ternary interaction between FGF-1, FGF receptor, and HSPG. [30][31][32][33] The addition of soluble heparin to FGF-1 confers resistance to thermal denaturation, chemical denaturation, and proteolysis, 28,40,41 and inclusion of heparin in the formulation of FGF-1 greatly improves its potency, stability, storage, and reconstitution properties. 28 Thus, heparin binding represents a key functionality that regulates the tissue distribution, pharmacokinetics, and receptor signaling of FGF-1.…”

The extracellular regulation of growth factor action.

“…The interaction of growth factors with matrix molecules can also stabilize the growth factor. For example, heparin protects aFGF and bFGF from inactivation by heat or acid (Gospodarowicz and Cheng, 1986) and proteases (Rosengart et al, 1988;Saksela et al, 1988;Sommer and Rifkin, 1989). The half-life of aFGF is increased 100-fold in the presence of heparin (Damon et al, 1989;Ortega et al, 1991).…”

Nanomechanics on FGF-2 and Heparin Reveal Slip Bond Characteristics with pH Dependency

“…7 It is for this mechanism that the activity of FGF-2 is linked to ECM remodeling, degradation and turnover. 8 As potent mitogenic growth factor, FGF-2 is spatially and temporarily tightly regulated during embryonal development and in tissue repair [9][10] , showing proliferative effects on a large number of cell types derived from mesodermal and ectodermal origin, including fibroblasts, mesenchymal stem cells and endothelial cells. 11 Cell stimulation requires the formation of a ternary complex composed of FGF-2, FGF-receptor, and HS co-receptor located on the cell surface.…”