Single and combined silencing of ERK1 and ERK2 reveals their positive contribution to growth signaling depending on their expression levels
Single and combined silencing of ERK1 and ERK2 reveals their positive contribution to growth signaling depending on their expression levels
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DOI：
10.1128/mcb.00800-07
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发表时间：
2008-01-01
影响因子：
5.3
通讯作者：
Lenormand, Philippe
中科院分区：
文献类型：
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作者：
Lefloch, Renaud;Pouyssegur, Jacques;Lenormand, Philippe
ERK1和ERK2蛋白高度相似，普遍表达，共享激活物和底物；然而，erk2基因失活在小鼠中是致命的，而erk1失活则不是。我们通过RNA干扰去除ERK1和/或ERK2，并探讨它们在细胞增殖和即时早期基因（IEG）表达中的相对作用。降低ERK1或ERK2的表达均可降低血清对IEG的诱导；然而，仅ERK2沉默会减慢细胞增殖。当这两种亚型同时被沉默时，ERK1/2残库的补偿性激活掩盖了对细胞增殖的更有害的影响。只有当ERK2的激活被限制在一个有限的水平时，我们才证明了ERK1对细胞增殖的积极贡献。然后我们确定了ERK同工型是不加区分地激活的，并且它们的表达比与它们的激活比完全相关。此外，我们首次确定ERK1和ERK2激酶活性在体外无法区分，erk基因剂量对小鼠的生存至关重要。我们认为ERK1和ERK2的表达水平驱动了它们明显的生物学差异。事实上，ERK1在一些脊椎动物中是可有可无的，因为它在鸡和青蛙的基因组中是缺失的，尽管迄今为止在所有哺乳动物和鱼类中都有。
The proteins ERK1 and ERK2 are highly similar, are ubiquitously expressed, and share activators and substrates; however, erk2 gene invalidation is lethal in mice, while erk1 inactivation is not. We ablated ERK1 and/or ERK2 by RNA interference and explored their relative roles in cell proliferation and immediate-early gene (IEG) expression. Reducing expression of either ERK1 or ERK2 lowered IEG induction by serum; however, silencing of only ERK2 slowed down cell proliferation. When both isoforms were silenced simultaneously, compensating activation of the residual pool of ERK1/2 masked a more deleterious effect on cell proliferation. It was only when ERK2 activation was clamped at a limiting level that we demonstrated the positive contribution of ERK1 to cell proliferation. We then established that ERK isoforms are activated indiscriminately and that their expression ratio correlated exactly with their activation ratio. Furthermore, we determined for the first time that ERK1 and ERK2 kinase activities are indistinguishable in vitro and that erk gene dosage is essential for survival of mice. We propose that the expression levels of ERK1 and ERK2 drive their apparent biological differences. Indeed, ERK1 is dispensable in some vertebrates, since it is absent from chicken and frog genomes despite being present in all mammals and fishes sequenced so far.