Strachan-Whaley Megan R, Reilly Kate, Dobson James, Kalisch Bettina E
Department of Biomedical Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada.
Department of Biomedical Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada.
Neurosci Lett. 2015 May 19;595:54-9. doi: 10.1016/j.neulet.2015.03.032. Epub 2015 Mar 19.
The present study assessed the mechanisms by which nerve growth factor (NGF) increased the level of apolipoprotein E (apoE) in PC12 cells. NGF (50ng/mL) significantly increased apoE protein levels following 72h of treatment. Similarly NGF increased luciferase activity in cells transfected with a luciferase reporter construct containing a 500bp fragment of the apoE promoter, indicating NGF-induced apoE expression is regulated, at least in part, at the level of transcription. The non-selective nitric oxide synthase (NOS) inhibitor N(ɷ)-nitro-L-arginine methylester (L-NAME; 20mM) did not attenuate the NGF-mediated increase in luciferase activity, while the inducible NOS inhibitor s-methylisothiourea (S-MIU; 2mM) partially attenuated this action of NGF. Inhibition of MAP kinase activation with 50μM U0126 or pre-treatment with the PKC inhibitor bisindolylmaleimide 1 (BIS-1; 10μM) prevented the NGF-mediated activation of the apoE promoter. Pre-treatment with the phospholipase C (PLC) inhibitor U73122 (5μM) partially inhibited the NGF-induced increase in luciferase activity while the Akt inhibitor LY294002 (10μM) had no effect. These data suggest NGF-induced apoE transcription requires MAP kinase and PKC activation and that these TrkA signaling pathways may be modulated by NO.
本研究评估了神经生长因子（NGF）提高PC12细胞中载脂蛋白E（apoE）水平的机制。处理72小时后，NGF（50ng/mL）显著提高了apoE蛋白水平。同样，NGF增加了用含有apoE启动子500bp片段的荧光素酶报告构建体转染的细胞中的荧光素酶活性，表明NGF诱导的apoE表达至少部分在转录水平受到调控。非选择性一氧化氮合酶（NOS）抑制剂N（ω）-硝基-L-精氨酸甲酯（L-NAME；20mM）并未减弱NGF介导的荧光素酶活性增加，而诱导型NOS抑制剂s-甲基异硫脲（S-MIU；2mM）部分减弱了NGF的这一作用。用50μM U0126抑制MAP激酶激活或用PKC抑制剂双吲哚基马来酰亚胺1（BIS-1；10μM）预处理可阻止NGF介导的apoE启动子激活。用磷脂酶C（PLC）抑制剂U73122（5μM）预处理可部分抑制NGF诱导的荧光素酶活性增加，而Akt抑制剂LY294002（10μM）则无作用。这些数据表明，NGF诱导的apoE转录需要MAP激酶和PKC激活，并且这些TrkA信号通路可能受NO调节。
