Role of MAP Kinase Cascade in the Regulation of Diverse Cellular Fuctions.

(1)通过用MEK的特异性抑制剂PD 98059处理阻断ERK-MAP激酶通路，完全抑制了其中通路被组成性激活的肿瘤细胞的生长。在<Klp1>PD 98059处理这些肿瘤细胞后观察到p27 α的选择性上调。p27 β的上调<Klp1>与p27 β与细胞<Klp1>周期蛋白E-CDK 2复合物的结合增加、细胞周期蛋白E-CDK 2激酶活性的伴随抑制以及RB磷酸化状态的随之降低相关，这将导致在这些肿瘤细胞中观察到的显著的G1细胞周期停滞。这些结果表明，在ERK-MAP激酶途径被组成型激活的肿瘤细胞中，特异性阻断ERK-MAP激酶途径后的完全生长抑制是由p27 α的上调介导的<Klp1>。(2)HGF可诱导MDCK细胞的铺展、解离和分散。HGF诱导细胞中ERK-MAP激酶的持续激活。我们有考试 关于我们 艾德是否需要在细胞核中的ERK-MAP激酶活性的HGF诱导的MDCK细胞的散射。为了进行分析，我们通过表达无活性形式的MKP-3细胞质磷酸酶来迫使细胞内ERK-MAP激酶保留。激活的ERK-MAP激酶的胞浆滞留明显抑制了MDCK细胞对HGF的散射反应，这些结果表明细胞核中的ERK-MAP激酶活性是HGF诱导MDCK细胞运动反应所必需的。(3)NGF具有诱导PC 12细胞向神经元分化的能力。NGF可诱导p38 MAP激酶通路和ERK-MAP激酶通路的持续激活。用SB 203580（p38 MAP激酶的特异性抑制剂）或PD 98059预处理PC 12细胞部分抑制了NGF诱导的神经突起生长，而用PD 98059和SB 203580组合预处理细胞导致几乎完全抑制NGF诱导的神经突起生长。这些结果表明，在NGF刺激的PC 12细胞中，ERK-MAP激酶通路的激活和p38 MAP激酶通路的激活是神经突起生长的诱导过程，ERK-MAP激酶参与神经丝蛋白（NF）的磷酸化，而p38 MAP激酶参与NF基因的表达。少

(1) Blockade of the ERK-MAP kinase pathway by treatment with PD98059, a specific inhibitor of MEK, completely suppressed the growth of tumor cells in which the pathway is constitutively activated. Selective up-regulation of p27^<Klp1> was observed after PD98059 treatment of these tumor cells. The up-regulation of p27^<Klp1> correlated with increased association of p27^<Klp1> with cyclin E-CDK2 complexes, a concomitant inhibition of cyclin E-CDK2 kinase activity, and consequent decrease in the phosphorylation state of RB, which would culminate in the marked G1 cell cycle arrest observed in these tumor cells. These results suggest that the complete growth suppression that follows specific blockade of the ERK-MAP kinase pathway in tumor cells in which the pathway is constitutively activated is mediated by up-regulation of p27^<Klp1>.(2) HGF induced the spreading, dissociation and scattering of MDCK cells. HGF induced the sustained activation of ERK-MAP kinases in the cells. We have examin … More ed whether or not the ERK-MAP kinase activity in the nucleus is required for HGF-induced scattering of MDCK cells. For the analysis, we forced cytoplasmic retention of ERK-MAP kinases in the cells by expressing an inactive form of the MKP-3 cytoplasmic phosphatase. The enforced cytoplasmic retention of the activated ERK-MAP kinases apparently inhibited the scattering response of MDCK cells in response to HGF.These results indicate that the ERK-MAP kinase activity in the nucleus is required for the motility response of MDCKcells induced by HGF.(3) NGF has the capacity to induce the neuronal differentiation of PC12 cells. NGF induced the sustained activation of p38 MAP kinase pathway as well as of ERK-MAP kinase pathway. Pretreatment of PC12 cells with SB203580 (a specific inhibitor of p38 MAP kinase) or PD98059 partially inhibited the NGF-induced neurite outgrowth formation, while pretreatment of the cells with a combination of PD98059 and SB203580 resulted in almost complete inhibition of NGF-induced neurite outgrowth. These results suggest that activation of the ERK-MAP kinase pathway together with activation of p38 MAP kinase pathway are required for full induction of neurite outgrowth following stimulation of PC12 cells with NGF.ERK-MAP kinases are suggestively involved in the phosphorylation of neurofilament proteins (NFs), while p38 MAP kinase is involved in the expression of NF genes. Less