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

(1)用MEK的特异性抑制剂PD98059阻断ERK-MAPK通路，可完全抑制该通路被结构性激活的肿瘤细胞的生长。经PD98059处理后，p27^&lt；Klp1&gt；选择性上调。P27^-lt；Klp1&gt；上调与p27^-lt；Klp1&gt；与细胞周期蛋白E-CDK2复合体的结合增加相关，伴随着细胞周期蛋白E-CDK2激酶活性的抑制，以及随之而来的Rb磷酸化状态的降低，最终导致在这些肿瘤细胞中观察到明显的G1期细胞周期停滞。这些结果表明，特异性阻断ERK-MAPK途径后，肿瘤细胞的生长受到完全抑制，其中ERK-MAPK途径被结构性激活，这是通过上调p27^&lt；Klp1&gt；介导的。(2)HGF诱导MDCK细胞的扩散、解离和散布。HGF可诱导细胞内ERK-MAP激酶的持续激活。我们有…考试HGF诱导的MDCK细胞分散是否需要核内ERK-MAPK活性。为了进行分析，我们通过表达一种非活性形式的MKP-3胞浆磷酸酶，迫使ERK-MAP激酶在细胞内保留。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，核内ERK-MAPK活性是HGF诱导MDCK细胞运动反应所必需的。(3)NGF具有诱导PC12细胞神经分化的能力。NGF可诱导p38MAP通路和ERK-MAP通路持续激活。用p38 MAPK的特异性抑制剂SB203580或PD98059部分抑制NGF诱导的PC12细胞突起生长，而PD98059和SB203580联合作用几乎完全抑制NGF诱导的突起生长。这些结果表明，在NGF刺激PC12细胞后，需要激活ERK-MAP激酶通路和激活p38 MAP激酶通路，以充分诱导神经突起生长。ERK-MAP激酶可能参与神经丝蛋白(NFs)的磷酸化，而p38 MAP激酶参与NF基因的表达。较少

(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