Host Cell Vimentin Restrains Toxoplasma gondii Invasion and Phosphorylation of Vimentin is Partially Regulated by Interaction with TgROP18

He, Cheng; Kong, Ling; Zhou, Lijuan; Xia, Jing; Wei, Haixia; Liu, Min; Peng, Hongjuan

To explore the function of host cell vimentin during T. gondii infection, the effect of vimentin on T. gondii invasion, growth, and egress were evaluated in HBMEC and HBMEC ΔVim cells. When vimentin was knocked out, the efficiency of T. gondii invasion increased significantly ( Figure 4B and C), while no significant difference was found in the number of parasites per vacuole between the two groups ( Figure 4D and E). T. gondii proliferation assays were also performed in HFF cells with or without vimentin knockdown, and the results were consistent with the findings of the tests in HBMEC ΔVim and wild type cells ( Figure S2 ). To further investigate the functions of vimentin in the lytic cycle of T. gondii, parasite egress, triggered by the Ca 2+ ionophore A23187, was assayed. No significant difference was identified in the percentage of egressed vacuoles between HBMEC and HBMEC ∆Vim, infected with RH/GFP ( Figure 4F and G). Together, these results suggest that host cell vimentin inhibited the invasion of T. gondii into HBMEC, but had no significant influence on T. gondii proliferation or egress. gondii (as described above) were detected by WB. Dynamic expression levels were observed after infection with T. gondii for different periods of time. These results suggest that the solubility, phosphorylation, and expression levels of vimentin were regulated by T. gondii infection, and that the higher phosphorylation level of vimentin may correlate with a decrease in its solubility. Statistical differences were evaluated by t-test, means ± SD combined from three independent experiments.