Department of Molecular Biology and Microbiology, College of Medicine, Burnett School of Biomedical Sciences, University of Central Florida, Orlando, Florida, USA.
Infect Immun. 2010 Nov;78(11):4532-41. doi: 10.1128/IAI.00802-10. Epub 2010 Sep 7.
The bacterial pathogen Listeria monocytogenes causes food-borne illnesses culminating in gastroenteritis, meningitis, or abortion. Listeria induces its internalization into some mammalian cells through binding of the bacterial surface protein InlB to the host receptor tyrosine kinase Met. Interaction of InlB with the Met receptor elicits host downstream signaling pathways that promote F-actin cytoskeletal changes responsible for pathogen engulfment. Here we show that the mammalian signaling protein ARAP2 plays a critical role in cytoskeletal remodeling and internalization of Listeria. Depletion of ARAP2 through RNA interference (RNAi) caused a marked inhibition of InlB-mediated F-actin rearrangements and bacterial entry. ARAP2 contains multiple functional domains, including a GTPase-activating protein (GAP) domain that antagonizes the GTPase Arf6 and a domain capable of binding the GTPase RhoA. Genetic data indicated roles for both the Arf GAP and RhoA binding domains in Listeria entry. Experiments involving Arf6 RNAi or a constitutively activated allele of Arf6 demonstrated that one of the ways in which ARAP2 promotes bacterial uptake is by restraining the activity of Arf6. Conversely, Rho activity was dispensable for Listeria internalization, suggesting that the RhoA binding domain in ARAP2 acts by engaging a host ligand other than Rho proteins. Collectively, our findings indicate that ARAP2 promotes InlB-mediated entry of Listeria, in part, by antagonizing the host GTPase Arf6.
细菌病原体李斯特菌会引起食源性疾病，最终导致肠胃炎、脑膜炎或流产。李斯特菌通过其表面蛋白 InlB 与宿主受体酪氨酸激酶 Met 的结合，诱导其内化进入一些哺乳动物细胞。InlB 与 Met 受体的相互作用引发宿主下游信号通路，促进负责病原体吞噬的 F-肌动蛋白细胞骨架变化。在这里，我们表明哺乳动物信号蛋白 ARAP2 在细胞骨架重塑和李斯特菌内化中发挥关键作用。通过 RNA 干扰 (RNAi) 耗尽 ARAP2 会导致 InlB 介导的 F-肌动蛋白重排和细菌进入明显抑制。ARAP2 包含多个功能域，包括拮抗 GTPase Arf6 的 GTPase 激活蛋白 (GAP) 域和能够结合 GTPase RhoA 的域。遗传数据表明，Arf GAP 和 RhoA 结合域在李斯特菌进入中都发挥作用。涉及 Arf6 RNAi 或 Arf6 组成激活等位基因的实验表明，ARAP2 促进细菌摄取的一种方式是通过抑制 Arf6 的活性。相反，Rho 活性对于李斯特菌内化是可有可无的，这表明 ARAP2 中的 RhoA 结合域通过与 Rho 蛋白以外的宿主配体结合来发挥作用。总的来说，我们的发现表明，ARAP2 通过拮抗宿主 GTPase Arf6 促进 InlB 介导的李斯特菌进入。
