The PIM family kinases promote cancer cell survival and motility as well as metastatic growth in various types of cancer. We have previously identified several PIM substrates, which support cancer cell migration and invasiveness. However, none of them are known to regulate cellular movements by directly interacting with the actin cytoskeleton. Here we have studied the phosphorylation-dependent effects of PIM1 on actin capping proteins, which bind as heterodimers to the fast-growing actin filament ends and stabilize them. Based on a phosphoproteomics screen for novel PIM substrates, we have used kinase assays and fluorescence-based imaging techniques to validate actin capping proteins as PIM1 substrates and interaction partners. We have analysed the functional consequences of capping protein phosphorylation on cell migration and adhesion by using wound healing and real-time impedance-based assays. We have also investigated phosphorylation-dependent effects on actin polymerization by analysing the protective role of capping protein phosphomutants in actin disassembly assays. We have identified capping proteins CAPZA1 and CAPZB2 as PIM1 substrates, and shown that phosphorylation of either of them leads to increased adhesion and migration of human prostate cancer cells. Phosphorylation also reduces the ability of the capping proteins to protect polymerized actin from disassembly. Our data suggest that PIM kinases are able to induce changes in actin dynamics to support cell adhesion and movement. Thus, we have identified a novel mechanism through which PIM kinases enhance motility and metastatic behaviour of cancer cells.

中文翻译：

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PIM1 通过磷酸化肌动蛋白帽蛋白来加速前列​​腺癌细胞的运动。

PIM 家族激酶促进癌细胞存活和运动以及各种类型癌症的转移生长。我们之前已经确定了几种 PIM 底物，它们支持癌细胞迁移和侵袭。然而，已知它们中没有一个通过直接与肌动蛋白细胞骨架相互作用来调节细胞运动。在这里，我们研究了 PIM1 对肌动蛋白帽蛋白的磷酸化依赖性影响，这些蛋白作为异源二聚体与快速生长的肌动蛋白丝末端结合并稳定它们。基于对新型 PIM 底物的磷酸化蛋白质组学筛选，我们使用激酶测定和基于荧光的成像技术来验证肌动蛋白封端蛋白作为 PIM1 底物和相互作用伙伴。我们已经通过使用伤口愈合和基于实时阻抗的测定分析了封端蛋白磷酸化对细胞迁移和粘附的功能影响。我们还通过分析肌动蛋白分解试验中加帽蛋白磷酸突变体的保护作用，研究了磷酸化依赖性对肌动蛋白聚合的影响。我们已将加帽蛋白 CAPZA1 和 CAPZB2 鉴定为 PIM1 底物，并表明它们中的任何一个的磷酸化都会导致人前列腺癌细胞的粘附和迁移增加。磷酸化还降低了加帽蛋白保护聚合肌动蛋白免于分解的能力。我们的数据表明 PIM 激酶能够诱导肌动蛋白动力学的变化以支持细胞粘附和运动。因此，