Julien Catherine, Coulombe Philippe, Meloche Sylvain
Institut de Recherches Cliniques de Montréal, Université de Montréal, 110 Pine Avenue West, Montréal, Québec H2W 1R7, Canada.
J Biol Chem. 2003 Oct 24;278(43):42615-24. doi: 10.1074/jbc.M302724200. Epub 2003 Aug 12.
Extracellular signal-regulated kinase 3 (ERK3) is an atypical member of the mitogen-activated protein kinase family of serine/threonine kinases. Little is known on the regulation of ERK3 function. Here, we report that ERK3 is constitutively localized in the cytoplasmic and nuclear compartments. In contrast to other mitogen-activated protein kinases, the cellular distribution of ERK3 remains unchanged in response to common mitogenic or stress stimuli and is independent of the enzymatic activity or phosphorylation of the kinase. The cytoplasmic localization of ERK3 is directed by a CRM1-dependent nuclear export mechanism. Treatment of cells with leptomycin B causes the nuclear accumulation of ERK3 in a high percentage of cells. Moreover, ectopic expression of CRM1 promotes the cytoplasmic relocalization of ERK3, whereas overexpression of snurportin 1, which binds CRM1 with high affinity, inhibits the nuclear export of ERK3. We also show that CRM1 binds to ERK3 in vitro. Importantly, we show that enforced localization of ERK3 in the nucleus or cytoplasm markedly attenuates the ability of the kinase to induce cell cycle arrest in fibroblasts. Our results suggest that nucleocytoplasmic shuttling of ERK3 is required for its negative regulatory effect on cell cycle progression.
细胞外信号调节激酶3（ERK3）是丝氨酸/苏氨酸激酶的丝裂原活化蛋白激酶家族中的一个非典型成员。关于ERK3功能的调节知之甚少。在此，我们报道ERK3组成性地定位于细胞质和细胞核区室。与其他丝裂原活化蛋白激酶不同，ERK3的细胞分布在常见的促有丝分裂或应激刺激下保持不变，并且独立于激酶的酶活性或磷酸化。ERK3的细胞质定位由依赖CRM1的核输出机制引导。用雷帕霉素B处理细胞会导致ERK3在高比例细胞中发生核积累。此外，CRM1的异位表达促进ERK3的细胞质重新定位，而与CRM1具有高亲和力结合的核转运蛋白1的过表达则抑制ERK3的核输出。我们还表明CRM1在体外与ERK3结合。重要的是，我们表明ERK3在细胞核或细胞质中的强制定位显著减弱了该激酶诱导成纤维细胞细胞周期停滞的能力。我们的结果表明，ERK3的核质穿梭是其对细胞周期进程产生负调节作用所必需的。
