LaRochelle W J, Sakaguchi K, Atabey N, Cheon H G, Takagi Y, Kinaia T, Day R M, Miki T, Burgess W H, Bottaro D P
Laboratory of Cellular and Molecular Biology, Division of Basic Sciences, National Cancer Institute, Bethesda, Maryland 20892, USA.
Biochemistry. 1999 Feb 9;38(6):1765-71. doi: 10.1021/bi982092z.
Keratinocyte growth factor (KGF) is an unusual fibroblast growth factor (FGF) family member in that its activity is largely restricted to epithelial cells, and added heparin/heparan sulfate inhibits its activity in most cell types. The effects of heparan sulfate proteoglycan (HSPG) on binding and signaling by acidic FGF (aFGF) and KGF via the KGFR were studied using surface-bound and soluble receptor isoforms expressed in wild type and mutant Chinese hamster ovary (CHO) cells lacking HSPG. Low concentrations of added heparin (1 microgram/mL) enhanced the affinity of ligand binding to surface-bound KGFR in CHO mutants, as well as ligand-stimulated MAP kinase activation and c-fos induction, but had little effect on binding or signaling in wild type CHO cells. Higher heparin concentrations inhibited KGF, but not aFGF, binding and signaling. In addition to the known interaction between HSPG and KGF, we found that the KGFR also bound heparin. The biphasic effect of heparin on KGF, but not aFGF, binding and signaling suggests that occupancy of the HSPG binding site on the KGFR may specifically inhibit KGF signaling. In contrast to events on the cell surface, added heparin was not required for high-affinity soluble KGF-KGFR interaction. These results suggest that high-affinity ligand binding is an intrinsic property of the receptor, and that the difference between the HSPG-dependent ligand binding to receptor on cell surfaces and the HSPG-independent binding to soluble receptor may be due to other molecule(s) present on cell surfaces.
角质形成细胞生长因子（KGF）是成纤维细胞生长因子（FGF）家族中一种不同寻常的成员，因为其活性在很大程度上局限于上皮细胞，并且添加的肝素/硫酸乙酰肝素会抑制其在大多数细胞类型中的活性。利用在缺乏硫酸乙酰肝素蛋白聚糖（HSPG）的野生型和突变型中国仓鼠卵巢（CHO）细胞中表达的表面结合型和可溶性受体亚型，研究了硫酸乙酰肝素蛋白聚糖（HSPG）对酸性FGF（aFGF）和KGF通过角质形成细胞生长因子受体（KGFR）进行的结合和信号传导的影响。低浓度添加的肝素（1微克/毫升）增强了配体与CHO突变体中表面结合的KGFR的结合亲和力，以及配体刺激的丝裂原活化蛋白激酶（MAP激酶）激活和c-fos诱导，但对野生型CHO细胞中的结合或信号传导影响很小。较高浓度的肝素抑制KGF，但不抑制aFGF的结合和信号传导。除了已知的HSPG与KGF之间的相互作用外，我们还发现KGFR也结合肝素。肝素对KGF而非aFGF的结合和信号传导的双相作用表明，KGFR上HSPG结合位点的占据可能特异性抑制KGF信号传导。与细胞表面的情况相反，高亲和力的可溶性KGF-KGFR相互作用不需要添加肝素。这些结果表明，高亲和力配体结合是受体的固有特性，并且细胞表面上HSPG依赖的配体与受体的结合和与可溶性受体的HSPG非依赖的结合之间的差异可能是由于细胞表面存在的其他分子。
