Insulin regulation of mitogen-activated protein kinase kinase (MEK), mitogen-activated protein kinase and casein kinase in the cell nucleus: A possible role in the regulation of gene expression
Insulin regulation of mitogen-activated protein kinase kinase (MEK), mitogen-activated protein kinase and casein kinase in the cell nucleus: A possible role in the regulation of gene expression
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DOI：
10.1042/bj3230621
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发表时间：
1997-05-01
影响因子：
4.1
通讯作者：
Kahn, CR
中科院分区：
文献类型：
--
作者：
Kim, SJ;Kahn, CR
胰岛素受体激活后，许多细胞质酶，包括丝裂原活化蛋白激酶（MAP）激酶、MAP激酶激酶（MEK）和酪蛋白激酶II （CKII）被激活，但胰岛素信号传导到细胞核的确切过程尚不清楚。在过表达人胰岛素受体[CHO(Hirc)]的中国仓鼠卵巢细胞中，在未受刺激状态下，细胞核和细胞质中均可检测到MEK、CKII和MAP激酶ERK I和ERK II。MAP激酶在3T3-F442A脂肪细胞、NIH-3T3细胞和Fao肝癌细胞中也存在核定位，而MEK仅在Fao和CHO细胞中存在核定位。胰岛素治疗5-30分钟可诱导MEK从细胞质转移到细胞核，而MAP激酶和CKII在此期间不会因胰岛素而转移到细胞核。然而，核MAP激酶和CKII活性在胰岛素刺激后1-10分钟内增加2-3倍。通过凝胶转移实验，胰岛素也刺激核蛋白结合到AP-1位点，其动力学类似于MEK易位和MAP激酶和CKII激活。体外用蛋白磷酸酶2A处理提取物或完整细胞用5,6-二氯-1- β -d -核糖呋喃基苯并咪唑（CKII的细胞渗透性抑制剂）处理，几乎完全阻断胰岛素诱导的dna结合活性，而用MEK抑制剂孵育的细胞只产生轻微的降低。这些结果表明，胰岛素信号通过两种途径导致细胞核中丝氨酸激酶的激活：(1)胰岛素刺激一些激酶的核易位，如MEK，这些激酶可能直接磷酸化核蛋白底物或激活其他核激酶；(2)胰岛素激活核激酶而不易位。后者在CKII中是正确的，它似乎调节核蛋白与AP-1位点的结合，可能是通过AP-1转录因子的磷酸化。
After insulin receptor activation, many cytoplasmic enzymes, including mitogen-activated protein (MAP) kinase, MAP kinase kinase (MEK) and casein kinase II (CKII) are activated, but exactly how insulin signalling progresses to the nucleus remains poorly understood. In Chinese hamster ovary cells overexpressing human insulin receptors [CHO(Hirc)], MEK, CKII and the MAP kinases ERK I and ERK II can be detected by immunoblotting in the nucleus, as well as in the cytoplasm, in the unstimulated state. Nuclear localization of MAP kinase is also observed in 3T3-F442A adipocytes, NIH-3T3 cells and Fao hepatoma cells, whereas MEK is found in the nucleus only in Fao and CHO cells. Insulin treatment for 5-30 min induces a translocation of MEK from the cytoplasm to the nucleus, whereas the MAP kinases and CKII are not translocated into the nucleus in response to insulin during this period. However, nuclear MAP kinase and CKII activities increase by 2-3-fold within 1-10 min after stimulation with insulin. By using gel-shift assays, it has been shown that insulin also stimulates nuclear protein binding to an AP-1 site with kinetics similar to MEK translocation and MAP kinase and CKII activation. Treatment of the extracts in vitro with protein phosphatase 2A or treatment of the intact cells with 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole, a cell-permeable inhibitor of CKII, almost completely blocks the insulin-induced DNA-binding activity, whereas incubation of cells with a MEK inhibitor produces only a slight decrease. These results suggest that insulin signalling results in the activation of serine kinases in the nucleus via two pathways: (1) insulin stimulates the nuclear translocation of some kinases, such as MEK, which might directly phosphorylate nuclear protein substrates or activate other nuclear kinases, and (2) insulin activates nuclear kinases without translocation. The latter is true of CKII, which seems to regulate the binding of nuclear proteins to the AP-1 site, possibly by phosphorylation of AP-1 transcription factors.