Damon D H, Lobb R R, D'Amore P A, Wagner J A
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts.
J Cell Physiol. 1989 Feb;138(2):221-6. doi: 10.1002/jcp.1041380202.
The mechanism(s) by which heparin influences the biological activities of acidic and basic fibroblast growth factors (aFGF and bFGF) is not completely understood. One mechanism by which heparin could alter the biological activities of aFGF and bFGF is by altering their biological half-lives. We investigated the possibility that heparin potentiates aFGF-induced neurite outgrowth from PC12 cells by prolonging its biological half-life. Under conditions where heparin potentiated aFGF-induced neurite outgrowth, we observed that heparin increased the biological half-life of aFGF from 7 to 39 hr. We determined that greater than 25 hr of exposure to active aFGF was required for induction of neurite outgrowth. If aFGF activity was maintained for greater than 25 hr by periodic readdition of factor, heparin no longer potentiated aFGF-induced neurite outgrowth. These observations strongly suggest that heparin potentiates the activity of aFGF by prolonging its biological half-life. The protease inhibitors hirudin, leupeptin, and pepstatin A did not potentiate aFGF-induced neurite outgrowth, indicating that proteases inhibited by these inhibitors are not responsible for the loss of aFGF activity that we observed. However, aprotinin potentiated aFGF neurite-promoting activity approximately sevenfold, indicating that proteases that are inhibited by aprotinin are at least partially responsible for aFGF inactivation. These observations suggest that heparin regulates the activity of aFGF by regulating its proteolytic degradation, thereby regulating its biological half-life.
肝素影响酸性和碱性成纤维细胞生长因子（aFGF和bFGF）生物学活性的机制尚未完全明确。肝素改变aFGF和bFGF生物学活性的一种机制可能是改变它们的生物半衰期。我们研究了肝素通过延长aFGF的生物半衰期来增强其诱导PC12细胞神经突生长的可能性。在肝素增强aFGF诱导神经突生长的条件下，我们观察到肝素将aFGF的生物半衰期从7小时延长至39小时。我们确定诱导神经突生长需要暴露于活性aFGF超过25小时。如果通过定期重新添加因子使aFGF活性维持超过25小时，肝素就不再增强aFGF诱导的神经突生长。这些观察结果强烈表明，肝素通过延长aFGF的生物半衰期来增强其活性。蛋白酶抑制剂水蛭素、亮抑酶肽和胃蛋白酶抑制剂A不能增强aFGF诱导的神经突生长，这表明这些抑制剂所抑制的蛋白酶并非我们所观察到的aFGF活性丧失的原因。然而，抑肽酶可使aFGF的神经突促进活性增强约7倍，这表明抑肽酶所抑制的蛋白酶至少部分参与了aFGF的失活过程。这些观察结果提示，肝素通过调节aFGF的蛋白水解降解来调控其活性，从而调节其生物半衰期。
