Mixed Lineage Kinase 3 (MLK3) activates mammalian MAPK signaling pathways in response to cytokines and stress stimuli. MLK3 is important for proliferation, migration and invasion of different types of human tumor cells. We observed that endogenous MLK3 was localized to both the cytoplasm and the nucleus in immortalized ovarian epithelial (T80) and ovarian cancer cells; and mutation of arginines 474 and 475 within a putative MLK3 nuclear localization sequence (NLS) resulted in exclusion of MLK3 from the nucleus. The Large Tumor Suppressor (LATS) Ser/Thr kinase regulates cell proliferation, morphology, apoptosis and mitotic exit in response to cell-cell contact. RNAi-mediated knockdown of LATS1 increased nuclear, endogenous MLK3 in T80 cells. LATS1 phosphorylated MLK3 on Thr477 which is within the putative NLS, and LATS1 expression enhanced the association between MLK3 and the adapter protein, 14-3-3ζ. Thr477 is essential for MLK3-14-3-3ζ association and MLK3 retention in the cytoplasm; and a T477A MLK3 mutant had predominantly nuclear localization and significantly increased invasiveness of SKOV3 ovarian cancer cells. This study identifies a novel link between the MAPK and Hippo/LATS1 signaling pathways. Our results reveal LATS1 as a novel regulator of MLK3 that controls MLK3 nuclear/cytoplasmic localization and MLK3-dependent ovarian cancer cell invasion.

中文翻译：

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LATS1 调节 MLK3 亚细胞定位和 MLK3 介导的卵巢上皮细胞侵袭

混合谱系激酶 3 (MLK​​3) 激活哺乳动物 MAPK 信号通路以响应细胞因子和压力刺激。MLK3 对不同类型的人类肿瘤细胞的增殖、迁移和侵袭很重要。我们观察到内源性 MLK3 位于永生化卵巢上皮 (T80) 和卵巢癌细胞的细胞质和细胞核中；推定的 MLK3 核定位序列 (NLS) 中精氨酸 474 和 475 的突变和突变导致 MLK3 从细胞核中排除。大肿瘤抑制因子 (LATS) Ser/Thr 激酶响应细胞间接触调节细胞增殖、形态学、凋亡和有丝分裂退出。RNAi 介导的 LATS1 敲低增加了 T80 细胞中核内源性 MLK3。LATS1 磷酸化 Thr477 上的 MLK3，它在推定的 NLS 内，ζ . Thr477 对于 MLK3-14-3-3 ζ结合和 MLK3 在细胞质中的保留至关重要；和 T477A MLK3 突变体主要具有核定位并显着增加 SKOV3 卵巢癌细胞的侵袭性。这项研究确定了 MAPK 和 Hippo/LATS1 信号通路之间的新联系。我们的研究结果表明 LATS1 作为 MLK3 的新型调节剂，可控制 MLK3 核/细胞质定位和 MLK3 依赖性卵巢癌细胞侵袭。