Qu Z, Wolfraim L A, Svaren J, Ehrengruber M U, Davidson N, Milbrandt J
Department of Pathology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
J Cell Biol. 1998 Aug 24;142(4):1075-82. doi: 10.1083/jcb.142.4.1075.
The PC12 pheochromocytoma cell line responds to NGF by undergoing growth arrest and proceeding to differentiate toward a neuronal phenotype. Among the early genetic events triggered by NGF in PC12 cells are the rapid activation of the zinc finger transcription factor Egr1/NGFI-A, and a slightly delayed induction of NAB2, a corepressor that inhibits Egr1 transcriptional activity. We found that stably transfected PC12 cells expressing high levels of NAB2 do not differentiate, but rather continue to proliferate in response to NGF. Inhibition of PC12 differentiation by NAB2 overexpression was confirmed using two additional experimental approaches, transient transfection, and adenoviral infection. Early events in the NGF signaling cascade, such as activation of MAP kinase and induction of immediate-early genes, were unaltered in the NAB2-overexpressing PC12 cell lines. However, induction of delayed NGF response genes such as TGF-beta1 and MMP-3 was inhibited. Furthermore, NAB2 overexpression led to downregulation of p21(WAF1), a molecule previously shown to play a pivotal role in the ability of PC12 cells to undergo growth arrest and commit to differentiation in response to NGF. Cotransfection with p21(WAF1) restored the ability of NAB2-overexpressing PC12 cells to differentiate in response to NGF.
PC12嗜铬细胞瘤细胞系对神经生长因子（NGF）的反应是经历生长停滞并朝着神经元表型分化。在PC12细胞中，NGF触发的早期基因事件包括锌指转录因子Egr1/NGFI-A的快速激活，以及NAB2（一种抑制Egr1转录活性的共抑制因子）的诱导稍延迟。我们发现，稳定转染并表达高水平NAB2的PC12细胞不会分化，而是在对NGF的反应中继续增殖。使用另外两种实验方法，即瞬时转染和腺病毒感染，证实了NAB2过表达对PC12分化的抑制作用。在过表达NAB2的PC12细胞系中，NGF信号级联反应的早期事件，如丝裂原活化蛋白激酶（MAP激酶）的激活和立即早期基因的诱导，未发生改变。然而，延迟的NGF反应基因如转化生长因子-β1（TGF-β1）和基质金属蛋白酶-3（MMP-3）的诱导受到抑制。此外，NAB2过表达导致p21（WAF1）下调，p21（WAF1）是一种先前显示在PC12细胞响应NGF进行生长停滞和分化能力中起关键作用的分子。与p21（WAF1）共转染恢复了过表达NAB2的PC12细胞响应NGF进行分化的能力。
