Jackson A, Friedman S, Zhan X, Engleka K A, Forough R, Maciag T
Department of Molecular Biology, Jerome H. Holland Laboratory for the Biomedical Sciences, American Red Cross, Rockville, MD 20855.
Proc Natl Acad Sci U S A. 1992 Nov 15;89(22):10691-5. doi: 10.1073/pnas.89.22.10691.
Fibroblast growth factor 1 (FGF-1) is a potent angiogenic and neurotrophic factor whose structure lacks a classical signal sequence for secretion. Although the initiation of these biological activities involves the interaction between FGF-1 and cell surface receptors, the mechanism responsible for the regulation of FGF-1 secretion is unknown. We report that murine NIH 3T3 cells transfected with a synthetic gene encoding FGF-1 secrete FGF-1 into their conditioned medium in response to heat shock. The form of FGF-1 released by NIH 3T3 cells in response to increased temperature (42 degrees C, 2 hr) in vitro is not biologically active and does not associate with either heparin or the extracellular NIH 3T3 monolayer matrix. However, it was possible to derive biologically active FGF-1 from the conditioned medium of heat-shocked NIH 3T3 cell transfectants by ammonium sulfate fractionation. The form of FGF-1 exposed by ammonium sulfate fractionation is similar in size to cytosolic FGF-1 and can bind and be eluted from immobilized heparin similarly to the recombinant human FGF-1 polypeptide. Further, the release of FGF-1 by NIH 3T3 cell transfectants in response to heat shock is reduced significantly by both actinomycin D and cycloheximide. These data indicate that increased temperature may upregulate the expression of a factor responsible for the secretion of FGF-1 as a biologically inactive complex that requires an activation step to exhibit the biological activity of the extracellular polypeptide mitogen.
成纤维细胞生长因子1（FGF - 1）是一种强效的血管生成和神经营养因子，其结构缺乏用于分泌的经典信号序列。尽管这些生物活性的启动涉及FGF - 1与细胞表面受体之间的相互作用，但负责调节FGF - 1分泌的机制尚不清楚。我们报告，用编码FGF - 1的合成基因转染的小鼠NIH 3T3细胞在热休克刺激下将FGF - 1分泌到其条件培养基中。NIH 3T3细胞在体外对温度升高（42摄氏度，2小时）作出反应而释放的FGF - 1形式没有生物活性，并且不与肝素或细胞外NIH 3T3单层基质结合。然而，通过硫酸铵分级分离可以从热休克的NIH 3T3细胞转染子的条件培养基中获得具有生物活性的FGF - 1。通过硫酸铵分级分离暴露的FGF - 1形式在大小上与胞质FGF - 1相似，并且可以与重组人FGF - 1多肽类似地结合固定化肝素并从其洗脱。此外，放线菌素D和环己酰亚胺均显著降低了NIH 3T3细胞转染子在热休克刺激下FGF - 1的释放。这些数据表明，温度升高可能上调负责分泌FGF - 1的因子的表达，该因子以无生物活性的复合物形式存在，需要一个激活步骤才能展现细胞外多肽有丝分裂原的生物活性。
