Nerve Growth Factor-Induced Neurite Outgrowth and MAP Kinase

i.用NGF培养PC12D细胞时，即使RNA合成被阻断，也能促进神经突的生长。成纤维细胞生长因子（FGF）对神经突的生长也有刺激作用，表皮生长因子（EGF）对神经突的生长有轻微刺激作用。MAP激酶的激活与PC12D细胞对各种药物的神经突生长密切相关，表明该激酶的激活可能在神经突生长中起重要作用。详情载于参考文献第1.ii。当用DEAE-Sepharose色谱柱分离对照和NGF-或dbcamp处理的PC12D细胞提取物的上清部分时，发现NGF-、FGF-和egf处理的细胞提取物在磷酸化微管相关蛋白的第3峰的激酶活性增强。在dbcamp处理的细胞中，峰1的激酶活性增强。这些观察结果加强了神经突生长与ngf依赖性MAP激酶的激活之间存在更密切关系的可能性。详情载于参考文献第2.iii号。研究了不同药物对PC12D细胞形态的快速变化与随后的神经突生长的关系。PC12D细胞上的各种神经突促进剂引起细胞周围的皱褶，同时F-actin重新定位到皱褶区域。皱褶的形成可能是神经突生长的最早步骤之一，其形态变化可能是由特定蛋白激酶的激活引起的。详情载于参考文献第3.iv号。Staurosporine能使培养的鸡胚背根神经节和PC12D细胞的神经突快速生长。通过电镜和细胞化学染色检测肌动蛋白和微管蛋白，神经突的生长与NGF诱导的神经突的生长难以区分。然而，staurosporine在无血清条件下对PC12D细胞的促进作用不如NGF。详情见参考文献第4号。少

i. When PC12D cells were cultured with NGF, outgrowth was neurites was promoted even when RNA synthesis was blocked. The outgrowth of neurites was also stimulated in response to fibroblast growth factor (FGF) and was slightly stimulated in response to epidermal growth factor (EGF). The close relationship between the activation of MAP kinase and outgrowth of neurites from PC12D cells in response to various agents suggests that activation of the kinase may play an important role in the outgrowth of neurites. Detailes were published in ref.no.1.ii. When the supernatant fractions from extracts of control and NGF- or dbcAMP-treated PC12D cells were fractionated by DEAE-Sepharose column, enhancement of kinase activity in the 3rd peak that phosphorylate microtuble-associated proteins was noted in the case of the extracts from NGF-, FGF-, and of EGF-treated cells. The kinase activity in peak 1 was enhanced in the case of dbcAMP-treated cells. The observations strengthens the possibility of a c … More lose relationship between the outgrowth of neurites and and the activation of NGF-dependent MAP kinase. Detailes were published in ref. no.2.iii. Rapid changes in morphology of PC12D cells in response to various agents were studied in relation to the subsequent outgrowth of neurites. Various neurite-promoting agents on PC12D cells caused ruffling around the periphery of cells and simultaneous relocalization of F-actin to the area of ruffles. The formation of ruffles might be one of the earliest steps of the neurite outgrowth and the morphological change might ge triggered by the activation of specific protein kinases. Detailers were published in ref.no.3.iv. Staurosporine caused the rapid outgrowth of neurites from cultured dorsal root ganglia of chick embryos and from PC12D cells. the outgrowth of neurites were indistinguishable from those induced by NGF, as assessed by electron microscopy and and cytochemical staining of actin and tubulin. However, staurosporine never promoted survival of PC12D cells in serum-free conditions as that promoted by NGF.Detailes were published in ref.no.4. Less