NGF-Induced Neurite Outgrowth from PC12 cells and MAP Kinase

研究了神经生长因子对PC12D细胞突起生长的局部调控作用。这些结果表明，神经生长因子对神经突起的维持或延伸可能在神经突起内部控制，可能不需要细胞体的直接参与(参考文献2)。Trichostatine A(TSA)在100 nM选择性地阻断NGF和b-FGF诱导的PC12D细胞突起的生长，但不阻断abcAMP或星形孢子素诱导的突起生长。本研究还证明了NGF诱导的轴突延长不需要蛋白质的从头合成(参考文献1)。当将显性抑制Ha-ras ASN-17基因导入PC12D细胞时，突变体RAS的诱导导致了对NGF的反应而不是对ABC的反应抑制了突起的快速生长。结果表明，RAS蛋白直接参与了NGF诱导的导致PC12D细胞突起形成的信号转导(参考文献3)。我们检测了MAP激酶(MEK)的特异性抑制剂PD98059对NGF诱导的PC12D细胞突起生长的影响。用50um PD98059处理PC12D细胞，可使NGF诱导的MAPK活性增加80%，但不能阻止NGF依赖的褶皱的形成和突起的生长。加入50um的PD98059可抑制NGF诱导的PC12细胞突起生长。相反，用NGF诱导的PC12细胞突起的快速再生在相同剂量的抑制剂的存在下没有改变。似乎神经生长因子依赖的神经突起的延伸并不一定需要MAP激酶通路的激活(参考文献3，文献4)。

i.We have examined the local control by NGF of the outgrowth of neurites from PC12D cells. The observations suggest that the NGF-dependent maintenance or extension of neurites might be controlled within the neurites themselves and might not be require the direct involvement of the cell body (ref.no.2).ii.Trichostatine A (TSA) at 100 nM selectively blocked the NGF- and b-FGF-induced outgrowth of neurites from PC12D cells, but not the outgrowth induced by abcAMP or staurosporine. This study also provides proof that NGF-induced elongation of neurites does not require protein synthesis de novo (ref.no.1).iii.When PC12D cells were transfected with the dominant inhibitory Ha-ras Asn-17 gene, the induction of the mutant Ras led the suppression of the rapid outgrowth of neurites in response to NGF but not to abcAMP.The results implies a direct involvement of Ras protein in in the NGF-induced signal transduction that lead to the formation of neurites in PC12D cells (ref.no.3).iv.We examined the effects of a specific inhibitor of the MAP kinase kinase (MEK) (PD98059) on the NGF-induced outgrowth of neurites in PC12D cells. The increase of MAP kinase activity in response to NGF was reduced by 80% upon treatment of PC12D cells with 50 muM PD98059, whereas the NGF-dependent formation of ruffles and the subsequent outgrowth of neurite were not blocked. The outgrowth of neurites from conventional PC12 cells by NGF was suppressed by the addition of 50 muM PD98059. In contrast, the rapid regeneration of neurites from PC12 cells primed with NGF,was not altered in the presence of the same dose of the inhibitor. It appeared that the activation of MAP kinase pathway was not necessarily required for the NGF-dependent extension of neurites (ref.no.3, ref no.4).