Unsworth Kate E, Way Michael, McNiven Mark, Machesky Laura, Holden David W
Centre for Molecular Microbiology and Infection, Department of Infectious Diseases, Imperial College London, Armstrong Road, London SW7 2AZ, UK.
Cell Microbiol. 2004 Nov;6(11):1041-55. doi: 10.1111/j.1462-5822.2004.00417.x.
Salmonella enterica serovar Typhimurium (S. typhimurium) induces actin assembly both during invasion of host cells and during the course of intracellular bacterial replication. In this study, we investigated the involvement in these processes of host cell signalling pathways that are frequently utilized by bacterial pathogens to manipulate the eukaryotic actin cytoskeleton. We confirmed that Cdc42, Rac, and Arp3 are involved in S. typhimurium invasion of HeLa cells, and found that N-WASP and Scar/WAVE also play a role in this process. However, we found no evidence for the involvement of these proteins in actin assembly during intracellular replication. Cortactin was recruited by Salmonella during both invasion and intracellular replication. However, RNA interference directed against cortactin did not inhibit either invasion or intracellular actin assembly, although it resulted in increased cell spreading and a greater number of lamellipodia. We also found no role for either the GTPase dynamin or the formin family member mDia1 in actin assembly by intracellular bacteria. Collectively, these data provide evidence that signalling pathways leading to Arp2/3-dependent actin nucleation play an important role in S. typhimurium invasion, but are not involved in intracellular Salmonella-induced actin assembly, and suggest that actin assembly by intracellular S. typhimurium may proceed by a novel mechanism.
鼠伤寒沙门氏菌（Salmonella enterica serovar Typhimurium，简称鼠伤寒沙门菌）在侵入宿主细胞以及细胞内细菌复制过程中都会诱导肌动蛋白组装。在本研究中，我们调查了宿主细胞信号通路在这些过程中的参与情况，这些信号通路常被细菌病原体用于操纵真核细胞的肌动蛋白细胞骨架。我们证实Cdc42、Rac和Arp3参与了鼠伤寒沙门菌对HeLa细胞的侵袭，并发现N-WASP和Scar/WAVE在此过程中也发挥作用。然而，我们没有发现这些蛋白质参与细胞内复制过程中肌动蛋白组装的证据。在侵袭和细胞内复制过程中，鼠伤寒沙门菌都会招募皮层肌动蛋白（Cortactin）。然而，针对皮层肌动蛋白的RNA干扰既没有抑制侵袭也没有抑制细胞内肌动蛋白组装，尽管它导致细胞铺展增加和丝状伪足数量增多。我们还发现GTP酶发动蛋白（dynamin）或formin家族成员mDia1在细胞内细菌诱导的肌动蛋白组装中均不起作用。总的来说，这些数据表明，导致Arp2/3依赖性肌动蛋白成核的信号通路在鼠伤寒沙门菌侵袭中起重要作用，但不参与细胞内鼠伤寒沙门菌诱导的肌动蛋白组装，并提示细胞内鼠伤寒沙门菌诱导的肌动蛋白组装可能通过一种新机制进行。
