Shimizu K, Kuroda S, Yamamori B, Matsuda S, Kaibuchi K, Yamauchi T, Isobe T, Irie K, Matsumoto K, Takai Y
Department of Molecular Biology and Biochemistry, Osaka University Medical School, Japan.
J Biol Chem. 1994 Sep 16;269(37):22917-20.
We have identified, in Xenopus oocyte cytosol, a protein kinase named REKS (Ras-dependent extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase kinase (MEK) stimulator), which phosphorylates and activates recombinant ERK2 through recombinant MEK in a recombinant GTP gamma S (guanosine 5'-(3-O-thio)triphosphate)-Ras-dependent manner. We show here that this REKS activity is synergistically enhanced by a combination of mammalian recombinant GTP gamma S-KiRas and 14-3-3 protein purified from rat brain. 14-3-3 protein is known to activate tyrosine and tryptophan hydroxylases, to modulate the protein kinase C activity, to stimulate secretion, and to show phospholipase A2 activity per se. 14-3-3 protein did not affect the MEK activity. 14-3-3 protein neither interacted with Ki-Ras nor affected the neurofibromin activity to stimulate the GTPase activity of Ki-Ras under the conditions where the recombinant N-terminal fragment of c-Raf-1 inhibited it. These results suggest that 14-3-3 protein has an additional function in the regulation of the Ras-MEK-ERK cascade pathway through the activation of REKS.
我们在非洲爪蟾卵母细胞胞质溶胶中鉴定出一种名为REKS（Ras依赖性细胞外信号调节激酶（ERK）/丝裂原活化蛋白激酶激酶（MEK）刺激因子）的蛋白激酶，它能以重组GTPγS（鸟苷5'-（3-O-硫代）三磷酸）-Ras依赖性方式通过重组MEK磷酸化并激活重组ERK2。我们在此表明，哺乳动物重组GTPγS-KiRas与从大鼠脑中纯化的14-3-3蛋白的组合可协同增强这种REKS活性。已知14-3-3蛋白可激活酪氨酸和色氨酸羟化酶、调节蛋白激酶C活性、刺激分泌并本身具有磷脂酶A2活性。14-3-3蛋白不影响MEK活性。在c-Raf-1的重组N端片段抑制Ki-Ras的GTP酶活性的条件下，14-3-3蛋白既不与Ki-Ras相互作用，也不影响神经纤维瘤蛋白刺激Ki-Ras的GTP酶活性的能力。这些结果表明，14-3-3蛋白在通过激活REKS调节Ras-MEK-ERK级联途径中具有额外功能。
