RAF protein kinases are effectors of the GTP-bound form of small guanosine triphosphatase RAS and function by phosphorylating MEK. We showed here that the expression of ARAF activated RAS in a kinase-independent manner. Binding of ARAF to RAS displaced the GTPase-activating protein NF1 and antagonized NF1-mediated inhibition of RAS. This reduced ERK-dependent inhibition of RAS and increased RAS-GTP. By this mechanism, ARAF regulated the duration and consequences of RTK-induced RAS activation and supported the RAS output of RTK-dependent tumor cells. In human lung cancers with EGFR mutation, amplification of ARAF was associated with acquired resistance to EGFR inhibitors, which was overcome by combining EGFR inhibitors with an inhibitor of the protein tyrosine phosphatase SHP2 to enhance inhibition of nucleotide exchange and RAS activation.

RAF 蛋白激酶是小鸟苷三磷酸酶 RAS 的 GTP 结合形式的效应器，通过磷酸化 MEK 发挥作用。我们在此表明​​ ARAF 的表达以不依赖于激酶的方式激活 RAS。ARAF 与 RAS 的结合取代了 GTP 酶激活蛋白 NF1，并拮抗了 NF1 介导的 RAS 抑制。这减少了 RAS 的 ERK 依赖性抑制并增加了 RAS-GTP。通过这种机制，ARAF 调节 RTK 诱导的 RAS 激活的持续时间和后果，并支持 RTK 依赖性肿瘤细胞的 RAS 输出。在具有 EGFR 突变的人类肺癌中，ARAF扩增与 EGFR 抑制剂获得性耐药有关，通过将 EGFR 抑制剂与蛋白酪氨酸磷酸酶 SHP2 抑制剂联合使用，增强对核苷酸交换和 RAS 激活的抑制，可以克服这一耐药性。