Hondermarck H, McLaughlin C S, Patterson S D, Bradshaw R A
Department of Biological Chemistry, College of Medicine, University of California, Irvine 92717.
Proc Natl Acad Sci U S A. 1994 Sep 27;91(20):9377-81. doi: 10.1073/pnas.91.20.9377.
Nerve growth factor (NGF) and basic fibroblast growth factor (bFGF) stimulate neuronal differentiation, whereas epidermal growth factor (EGF) promotes only mitogenic responses in PC12 pheochromocytoma cells. The early changes in protein synthesis induced by bFGF, NGF, and EGF in these cells have been determined by two-dimensional PAGE of [35S]methionine-labeled proteins and computerized image analysis. The rate of synthesis of only 29 proteins (out of approximately 1500 identified) was found to be modulated during the first several hours of growth factor stimulation. Individually, 12 were affected by EGF, 23 were affected by bFGF, and 20 were affected by NGF. Eight of these were regulated by all three growth factors, while 10 proteins were commonly induced by bFGF and NGF, in accordance with the essentially identical morphological responses induced by these two factors. In addition, the effects of bFGF and NGF were about equally divided between increases and decreases in the rate of synthesis of individual proteins, whereas EGF caused significantly more positive (increased) responses. All proteins modulated by NGF or FGF alone were negative in their response and those induced by only EGF were positive. Of particular interest, the rate of synthesis of two proteins of 55 kDa and pI 5.45 and 5.50 was dramatically and transiently induced during the first 2 hr of bFGF and NGF treatment and was not affected by EGF. This study indicates that all three factors elicit early increases and decreases in the synthesis of a quite limited number of proteins and provides molecular evidence for the specificity of a differentiative vs. a proliferative growth factor-induced signaling pathway in these cells.
神经生长因子（NGF）和碱性成纤维细胞生长因子（bFGF）可刺激神经元分化，而表皮生长因子（EGF）仅能促进PC12嗜铬细胞瘤细胞的有丝分裂反应。通过对[35S]甲硫氨酸标记的蛋白质进行二维聚丙烯酰胺凝胶电泳（PAGE）和计算机图像分析，已确定了bFGF、NGF和EGF在这些细胞中诱导的蛋白质合成早期变化。在生长因子刺激的最初几个小时内，仅发现约1500种已鉴定蛋白质中的29种蛋白质的合成速率受到调节。其中，12种受EGF影响，23种受bFGF影响，20种受NGF影响。其中8种受所有三种生长因子调节，而10种蛋白质由bFGF和NGF共同诱导，这与这两种因子诱导的基本相同的形态学反应一致。此外，bFGF和NGF的作用在单个蛋白质合成速率的增加和减少之间大致相等，而EGF引起的阳性（增加）反应明显更多。仅由NGF或FGF调节的所有蛋白质反应均为阴性，仅由EGF诱导的蛋白质反应为阳性。特别有趣的是，在bFGF和NGF处理的最初2小时内，两种分子量为55 kDa、等电点为5.45和5.50的蛋白质的合成速率急剧且短暂地诱导，且不受EGF影响。这项研究表明，所有三种因子在相当有限数量的蛋白质合成中均引起早期增加和减少，并为这些细胞中分化与增殖生长因子诱导的信号通路的特异性提供了分子证据。
