Dimerization of the kinase ARAF promotes MAPK pathway activation and cell migration
Dimerization of the kinase ARAF promotes MAPK pathway activation and cell migration
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DOI：
10.1126/scisignal.2005484
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发表时间：
2014-08-05
影响因子：
7.3
通讯作者：
Rajalingam, Krishnaraj
中科院分区：
文献类型：
--
作者：
Mooz, Juliane;Oberoi-Khanuja, Tripat Kaur;Rajalingam, Krishnaraj
RAF激酶家族介导RAS信号传导，并且RAF抑制剂可有效用于治疗具有BRAF（V600 E）突变蛋白的肿瘤。然而，RAF抑制剂自相矛盾地加速RAS突变型肿瘤的转移，并且由于下游丝裂原活化蛋白激酶（MAPK）信号传导的再活化而在BRAF（V600 E）肿瘤中变得无效。我们发现，RAF亚型ARAF有一个强制性的作用，促进MAPK活性和细胞迁移的细胞类型依赖性的方式。敲低ARAF可阻止MAPK激酶1（MEK 1）和细胞外信号调节激酶1和2（ERK 1/2）的激活，并减少BRAF（V600 E）特异性或BRAF/CRAF抑制剂（分别为GDC-0879和索拉非尼）诱导的三维培养中肿瘤细胞球状体突起的数量。RAF抑制剂诱导ARAF的同源二聚化和BRAF与CRAF和支架蛋白KSR 1的异源二聚化。在纯化的蛋白质溶液中，三种RAF同种型的重组蛋白质竞争结合MEK 1。在培养的细胞中，不能同源二聚化的ARAF的过表达突变体损害了ARAF和内源性MEK 1之间的相互作用，从而阻止了随后的MEK 1和ERK 1/2的激活。我们的研究结果揭示了ARAF在直接激活MAPK级联反应和促进肿瘤细胞侵袭中的新作用，并为RAS和RAF介导的癌症提供了新的治疗靶点。
The RAF family of kinases mediates RAS signaling, and RAF inhibitors can be effective for treating tumors with BRAF(V600E) mutant protein. However, RAF inhibitors paradoxically accelerate metastasis in RAS-mutant tumors and become ineffective in BRAF(V600E) tumors because of reactivation of downstream mitogen-activated protein kinase (MAPK) signaling. We found that the RAF isoform ARAF has an obligatory role in promoting MAPK activity and cell migration in a cell type-dependent manner. Knocking down ARAF prevented the activation of MAPK kinase 1 (MEK1) and extracellular signal-regulated kinase 1 and 2 (ERK1/2) and decreased the number of protrusions from tumor cell spheroids in three-dimensional culture that were induced by BRAF(V600E)-specific or BRAF/CRAF inhibitors (GDC-0879 and sorafenib, respectively). RAF inhibitors induced the homodimerization of ARAF and the heterodimerization of BRAF with CRAF and the scaffolding protein KSR1. In a purified protein solution, recombinant proteins of the three RAF isoforms competed for binding to MEK1. In cells in culture, over-expressing mutants of ARAF that could not homodimerize impaired the interaction between ARAF and endogenous MEK1 and thus prevented the subsequent activation of MEK1 and ERK1/2. Our findings reveal a new role for ARAF in directly activating the MAPK cascade and promoting tumor cell invasion and suggest a new therapeutic target for RAS- and RAF-mediated cancers.