Lazarovici P, Oshima M, Shavit D, Shibutani M, Jiang H, Monshipouri M, Fink D, Movsesyan V, Guroff G
Section on Growth Factors, NICHD, National Institutes of Health, Bethesda, Maryland 20892, USA.
J Biol Chem. 1997 Apr 25;272(17):11026-34. doi: 10.1074/jbc.272.17.11026.
Nerve growth factor (NGF) treatment causes a profound down-regulation of epidermal growth factor receptors during the differentiation of PC12 cells. This process is characterized by a progressive decrease in epidermal growth factor (EGF) receptor level measured by 125I-EGF binding, tyrosine phosphorylation, and Western blotting. Treatment of the cells with NGF for 5 days produces a 95% reduction in the amount of [35S]methionine-labeled EGF receptors. This down-regulation does not occur in PC12nnr5 cells, which lack the p140(trk) NGF receptor. However, in PC12nnr5 cells stably transfected with p140(trk), the NGF-induced heterologous down-regulation of EGF receptors is reconstituted in part. NGF-induced heterologous down-regulation, but not EGF-induced homologous down-regulation of EGF receptors, is blocked in Ras- and Src-dominant-negative PC12 cells. Treatment with either pituitary adenylate cyclase-activating peptide (PACAP) or staurosporine stimulates neurite outgrowth in PC12 cell variants, but neither induces down-regulation of EGF receptors. NGF treatment of PC12 cells in suspension induces down-regulation of EGF receptors in the absence of neurite outgrowth. These results strongly suggest a p140(trk)-, Ras- and Src-dependent mechanism of NGF-induced down-regulation of EGF receptors and separate this process from NGF-induced neurite outgrowth in PC12 cells.
在PC12细胞分化过程中，神经生长因子（NGF）处理会导致表皮生长因子受体显著下调。这一过程的特征是，通过¹²⁵I-EGF结合、酪氨酸磷酸化和蛋白质印迹法测定的表皮生长因子（EGF）受体水平逐渐降低。用NGF处理细胞5天，会使[³⁵S]甲硫氨酸标记的EGF受体数量减少95%。这种下调在缺乏p140(trk) NGF受体的PC12nnr5细胞中不会发生。然而，在稳定转染了p140(trk)的PC12nnr5细胞中，NGF诱导的EGF受体异源下调部分得到恢复。在Ras和Src显性阴性的PC12细胞中，NGF诱导的EGF受体异源下调被阻断，但EGF诱导的同源下调未被阻断。用垂体腺苷酸环化酶激活肽（PACAP）或星形孢菌素处理可刺激PC12细胞变体中的神经突生长，但两者均未诱导EGF受体下调。在悬浮状态下用NGF处理PC12细胞，在没有神经突生长的情况下也会诱导EGF受体下调。这些结果强烈提示了一种依赖p140(trk)、Ras和Src的NGF诱导EGF受体下调的机制，并将这一过程与PC12细胞中NGF诱导的神经突生长区分开来。
