Chang Jay H, Vuppalanchi Deepika, van Niekerk Erna, Trepel Jane B, Schanen N Carolyn, Twiss Jeffery L
Cellular and Molecular Pathology Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, California, USA.
J Neurochem. 2006 Dec;99(6):1517-30. doi: 10.1111/j.1471-4159.2006.04196.x. Epub 2006 Oct 24.
Both cyclic AMP (cAMP) and nerve growth factor (NGF) have been shown to cause rapid activation of cAMP response element-binding protein (CREB) by phosphorylation of serine 133, but additional regulatory events contribute to CREB-targeted gene expression. Here, we have used stable transfection with a simple cAMP response element (CRE)-driven reporter to address the kinetics of CRE-dependent transcription during neuronal differentiation of PC12 cells. In naive cells, dibutyryl cAMP (dbcAMP) generated a rapid increase in CRE-driven luciferase activity by 5 h that returned to naive levels by 24 h. Luciferase induction after NGF treatment was delayed until 48 h when CRE-driven luciferase expression became TrkA dependent. Blocking histone deacetylase (HDAC) activity accelerated NGF-dependent CRE-driven luciferase expression by at least 24 h and resulted in a sustained cAMP-dependent expression of CRE-driven luciferase beyond 24 h. Inhibition of protein synthesis before stimulation with NGF or dbcAMP indicated that both stimuli induce expression of a transcriptional repressor that delays NGF-dependent and attenuates cAMP-dependent CRE-driven transcription. NGF caused a rapid but transient HDAC-dependent increase in inducible cAMP element repressor (ICER) expression, but ICER expression was sustained with increased cAMP. Depletion of ICER from PC12 cells indicated that HDAC-dependent ICER induction is responsible for the delay in CRE-dependent transcription after NGF treatment.
环磷酸腺苷（cAMP）和神经生长因子（NGF）均已被证明可通过丝氨酸133的磷酸化导致环磷酸腺苷反应元件结合蛋白（CREB）的快速激活，但其他调控事件也有助于CREB靶向基因的表达。在此，我们使用了一种简单的由环磷酸腺苷反应元件（CRE）驱动的报告基因进行稳定转染，以研究PC12细胞神经元分化过程中CRE依赖性转录的动力学。在未分化的细胞中，二丁酰环磷酸腺苷（dbcAMP）在5小时内使CRE驱动的荧光素酶活性迅速增加，到24小时时又恢复到未处理时的水平。NGF处理后的荧光素酶诱导延迟至48小时，此时CRE驱动的荧光素酶表达变得依赖于酪氨酸激酶A（TrkA）。抑制组蛋白脱乙酰酶（HDAC）活性可使NGF依赖性CRE驱动的荧光素酶表达至少提前24小时，并导致CRE驱动的荧光素酶在24小时后持续依赖于cAMP表达。在用NGF或dbcAMP刺激之前抑制蛋白质合成表明，两种刺激均诱导了一种转录抑制因子的表达，该抑制因子延迟了NGF依赖性并减弱了cAMP依赖性CRE驱动的转录。NGF导致诱导型环磷酸腺苷元件阻遏物（ICER）表达迅速但短暂地依赖于HDAC增加，而ICER表达随着cAMP增加而持续。从PC12细胞中去除ICER表明，HDAC依赖性ICER诱导是NGF处理后CRE依赖性转录延迟的原因。
