NGF-Induced Neurite Outgrowth from PC12 cells and MAP Kinase

i.我们已经检查了NGF对来自PC 12 D细胞的神经突生长的局部控制。观察结果表明，神经突的NGF依赖性维持或延伸可能在神经突本身内被控制，并且可能不需要细胞体的直接参与（参考文献2）。ii. 100 nM的曲古抑菌素A（TSA）选择性地阻断NGF和b-FGF诱导的神经突从PC 12 D细胞的生长，但不阻断由abcAMP或星形孢菌素诱导的生长。这项研究也提供了证据，神经生长因子诱导的神经突起的延长不需要蛋白质合成从头开始iii.当用显性抑制性Ha-ras Asn-17基因转染PC 12 D细胞时，突变Ras的诱导导致了对NGF的反应而不是对abcAMP的反应的神经突的快速生长的抑制。iv.我们检测了MAP激酶激酶（MEK）的特异性抑制剂（PD 98059）对NGF诱导的PC 12 D细胞中神经突生长的影响。在用50 μ M PD 98059处理PC 12 D细胞后，响应于NGF的MAP激酶活性的增加减少了80%，而NGF依赖的皱褶形成和随后的神经突生长没有被阻断。通过添加50 μ M PD 98059，NGF抑制了来自常规PC 12细胞的神经突的生长。相反，在相同剂量的抑制剂存在下，NGF引发的PC 12细胞的神经突的快速再生没有改变。看来MAP激酶通路的激活对于神经突的NGF依赖性延伸不是必需的（参考文献3，参考文献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).