Randall Division of Cell and Molecular Biophysics, King's College London, London, UK.
Oncogene. 2013 Apr 18;32(16):2114-20. doi: 10.1038/onc.2012.233. Epub 2012 Jun 11.
Hepatocyte growth factor (HGF) and its receptor (c-Met) are associated with cancer cell motility and invasiveness. p21-activated kinase 4 (PAK4), a potential therapeutic target, is recruited to and activated by c-Met. In response, PAK4 phosphorylates LIM kinase 1 (LIMK1) in an HGF-dependent manner in metastatic prostate carcinoma cells. PAK4 overexpression is known to induce increased cell migration speed but the requirement for kinase activity has not been established. We have used a panel of PAK4 truncations and mutations in a combination of overexpression and RNAi rescue experiments to determine the requirement for PAK4 kinase activity during carcinoma cell motility downstream of HGF. We find that neither the kinase domain alone nor a PAK4 mutant unable to bind Cdc42 is able to fully rescue cell motility in a PAK4-deficient background. Nevertheless, we find that PAK4 kinase activity and associated LIMK1 activity are essential for carcinoma cell motility, highlighting PAK4 as a potential anti-metastatic therapeutic target. We also show here that overexpression of PAK4 harbouring a somatic mutation, E329K, increased the HGF-driven motility of metastatic prostate carcinoma cells. E329 lies within the glycine-rich loop region of the kinase. Our data suggest that E329K mutation leads to a modest increase in kinase activity, conferring resistance to competitive ATP inhibitors in addition to promoting cell migration. The existence of such a mutation may have implications for the development of PAK4-specific competitive ATP inhibitors should PAK4 be further explored for clinical inhibition.
肝细胞生长因子 (HGF) 及其受体 (c-Met) 与癌细胞的运动性和侵袭性有关。p21 激活激酶 4 (PAK4) 是一种潜在的治疗靶点,它被 c-Met 募集并激活。作为回应,PAK4 以 HGF 依赖的方式磷酸化 LIM 激酶 1 (LIMK1) 在转移性前列腺癌细胞中。已知 PAK4 的过表达会诱导细胞迁移速度增加,但激酶活性的需求尚未确定。我们使用了一组 PAK4 截断和突变体,结合过表达和 RNAi 挽救实验,以确定 HGF 下游癌细运动过程中 PAK4 激酶活性的要求。我们发现,激酶结构域本身或不能结合 Cdc42 的 PAK4 突变体都不能在 PAK4 缺陷背景下完全挽救细胞运动性。尽管如此,我们发现 PAK4 激酶活性和相关的 LIMK1 活性对于癌细胞的运动性至关重要,这突显了 PAK4 作为一种潜在的抗转移治疗靶点。我们还在这里表明,过表达具有体细胞突变 E329K 的 PAK4 会增加转移性前列腺癌细胞的 HGF 驱动的运动性。E329 位于激酶的甘氨酸丰富环区域内。我们的数据表明,E329K 突变导致激酶活性略有增加,除了促进细胞迁移外,还对竞争性 ATP 抑制剂产生抗性。如果进一步探索 PAK4 用于临床抑制,那么存在这种突变可能会对开发 PAK4 特异性竞争性 ATP 抑制剂产生影响。