Mitra G, Weber M, Stacey D
Department of Molecular Biology, Cleveland Clinic Foundation, OH.
Cell Mol Biol Res. 1993;39(5):517-23.
p42/Mitogen activated protein kinase (MAPK) and MAP Kinase Kinase (MAPKK) activities are constitutively elevated in v-raf transformed NIH3T3 cells, which correlates with increased tyrosine phosphorylation of p42mapk protein. These activities can be further enhanced to a moderate extent by treatment of raf-transformed cells with either serum, tetradecanoyl phorbol acetate (TPA), or aluminium fluoride. A similar activation of MAPK is observed in a cell line (M17raf) coexpressing a dominant inhibitory ras mutant (N-17 ras) along with v-raf. However, in this cell line, both the serum and TPA stimulated response of MAPK activity is reduced compared to similarly treated raf-transformed cells, while aluminium fluoride is equally potent in all the cell lines tested. These studies indicate that in addition to c-Raf-1, serine/threonine kinase, which is an upstream activator of MAPK, other c-ras dependent as well as c-ras independent pathways also can contribute to MAPK activation.
在v-raf转化的NIH3T3细胞中，p42/丝裂原活化蛋白激酶（MAPK）和MAP激酶激酶（MAPKK）的活性持续升高，这与p42mapk蛋白酪氨酸磷酸化增加相关。用血清、十四烷酰佛波醇乙酸酯（TPA）或氟化铝处理raf转化细胞，这些活性可在一定程度上进一步增强。在共表达显性抑制性ras突变体（N-17 ras）和v-raf的细胞系（M17raf）中观察到类似的MAPK激活。然而，在该细胞系中，与经类似处理的raf转化细胞相比，血清和TPA刺激的MAPK活性反应均降低，而氟化铝在所有测试细胞系中效力相同。这些研究表明，除了作为MAPK上游激活剂的丝氨酸/苏氨酸激酶c-Raf-1外，其他c-ras依赖性以及c-ras非依赖性途径也可导致MAPK激活。
