Regulation of glioblastoma cell invasion by PKCι and RhoB
Regulation of glioblastoma cell invasion by PKCι and RhoB
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DOI：
10.1038/sj.onc.1211027
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发表时间：
2008-06-05
期刊：
影响因子：
8
通讯作者：
Lorimer, I. A. J.
中科院分区：
文献类型：
--
作者：
Baldwin, R. M.;Parolin, D. A. E.;Lorimer, I. A. J.
多形性胶质母细胞瘤是最具侵袭性的原发脑肿瘤，由于其高度侵袭性，在很大程度上仍是无法治愈的。在这些肿瘤中，由于表皮生长因子受体的激活突变或肿瘤抑制基因PTEN的缺失/丧失，磷脂酰肌醇(PI)3-激酶途径通常是结构性活跃的。蛋白激酶C型IOTA(PKC IOTA)是非典型蛋白激酶C家族中的一员，由PI 3-激酶途径激活，是一种重要的下游调节因子。在这里，我们评估了PKC IOTA在胶质母细胞瘤细胞侵袭中的作用。RNA干扰使PKC IOTA耗尽，肌动蛋白应激纤维增多，细胞运动和侵袭能力下降。对U87 MG细胞的基因表达芯片分析表明，PKC IOTA抑制了RhoB的mRNA表达，此前已证明RhoB在肌动蛋白应激纤维的形成中起作用。Western印迹分析表明，PKC IOTA的耗竭和药物抑制均可引起RhoB蛋白水平的升高，PI3-K的抑制也可引起RhoB蛋白水平的升高。来自构成启动子的RhoB的表达引起肌动蛋白应激纤维和细胞侵袭的变化，这与PKC IOTA耗竭时看到的情况类似。这些数据表明，PKC IOTA是上游PI 3-K信号异常激活的结果，它介导了胶质母细胞瘤细胞的运动和侵袭，而抑制RhoB是PKC IOTA信号导致细胞运动增强的关键下游事件。此外，RhoB的结构性表达抑制了PKC IOTA的活性，通过其在Thr555上的磷酸化状态进行评估。因此，PKC IOTA和RhoB是相互拮抗的，潜在地在侵袭性和非侵袭性表型之间创造了敏感的切换。
Glioblastoma multiforme is the most aggressive form of primary brain tumor and remains largely incurable, in large part, due to its highly invasive nature. The phosphoinositide (PI) 3-kinase pathway is often constitutively active in these tumors due to activating mutations in the epidermal growth factor receptor, or deletion/loss of function of the tumor suppressor PTEN. Protein kinase C type iota (PKC iota), a member of the atypical protein kinase C family, is activated by the PI 3-kinase pathway and is an important downstream mediator. Here, we have assessed the role of PKC iota in glioblastoma cell invasion. Depletion of PKC iota with RNA interference caused an increase in actin stress fibers and a decrease in cell motility and invasion. Gene expression microarray analysis of U87MG cells showed that PKC iota repressed expression of mRNA for RhoB, which has previously been shown to have a role in actin stress fiber formation. Western blot analysis showed that both PKC iota depletion and pharmacological inhibition of PKC iota caused an increase in the protein levels of RhoB, as did inhibition of PI 3-kinase. Expression of RhoB from a constitutive promoter caused changes in actin stress fibers and cell invasion that were similar to those seen with PKC iota depletion. These data show that PKC iota, activated as a consequence of aberrant upstream PI 3-kinase signaling, mediates glioblastoma cell motility and invasion, and that repression of RhoB is key downstream event in PKC iota signaling leading to enhanced cell motility. In addition, constitutive expression of RhoB repressed PKC iota activity, as assessed by its phosphorylation status on Thr555. PKC iota and RhoB are, therefore, mutually antagonistic, potentially creating a sensitive switch between invasive and non-invasive phenotypes.