Robert Amélie, Smadja-Lamère Nicolas, Landry Marie-Claude, Champagne Claudia, Petrie Ryan, Lamarche-Vane Nathalie, Hosoya Hiroshi, Lavoie Josée N
Centre de Recherche en Cancérologie de l'Université Laval, L'Hôtel-Dieu de Québec, Centre de Recherche du Centre Hospitalier Universitaire de Québec, Québec, Québec G1R 2J6, Canada.
Mol Biol Cell. 2006 Jul;17(7):3329-44. doi: 10.1091/mbc.e05-12-1146. Epub 2006 May 10.
The adenovirus early region 4 ORF4 protein (E4orf4) triggers a novel death program that bypasses classical apoptotic pathways in human cancer cells. Deregulation of the cell cytoskeleton is a hallmark of E4orf4 killing that relies on Src family kinases and E4orf4 phosphorylation. However, the cytoskeletal targets of E4orf4 and their role in the death process are unknown. Here, we show that E4orf4 translocates to cytoplasmic sites and triggers the assembly of a peculiar juxtanuclear actin-myosin network that drives polarized blebbing and nuclear shrinkage. We found that E4orf4 activates the myosin II motor and triggers de novo actin polymerization in the perinuclear region, promoting endosomes recruitment to the sites of actin assembly. E4orf4-induced actin dynamics requires interaction with Src family kinases and involves a spatial regulation of the Rho GTPases pathways Cdc42/N-Wasp, RhoA/Rho kinase, and Rac1, which make distinct contributions. Remarkably, activation of the Rho GTPases is required for induction of apoptotic-like cell death. Furthermore, inhibition of actin dynamics per se dramatically impairs E4orf4 killing. This work provides strong support for a causal role for endosome-associated actin dynamics in E4orf4 killing and in the regulation of cancer cell fate.
腺病毒早期区域4开放阅读框4蛋白（E4orf4）触发一种新型死亡程序，该程序绕过人类癌细胞中的经典凋亡途径。细胞骨架失调是E4orf4杀伤作用的一个标志，这依赖于Src家族激酶和E4orf4磷酸化。然而，E4orf4的细胞骨架靶点及其在死亡过程中的作用尚不清楚。在这里，我们表明E4orf4易位至细胞质位点，并触发一种特殊的近核肌动蛋白-肌球蛋白网络的组装，该网络驱动极化气泡形成和核收缩。我们发现E4orf4激活肌球蛋白II马达，并在核周区域触发肌动蛋白的从头聚合，促进内体募集至肌动蛋白组装位点。E4orf4诱导的肌动蛋白动力学需要与Src家族激酶相互作用，并涉及Rho GTP酶途径Cdc42/N-Wasp、RhoA/Rho激酶和Rac1的空间调节，它们发挥着不同的作用。值得注意的是，Rho GTP酶的激活是诱导凋亡样细胞死亡所必需的。此外，肌动蛋白动力学的抑制本身会显著损害E4orf4的杀伤作用。这项工作为内体相关的肌动蛋白动力学在E4orf4杀伤作用和癌细胞命运调控中的因果作用提供了有力支持。
