PDF(Pubmed)
Abstract：
Ehrlichia chaffeensis infects and proliferates inside monocytes or macrophages and causes human monocytic ehrlichiosis (HME), an emerging life-threatening tick-borne zoonosis. After internalization, E. chaffeensis resides in specialized membrane-bound inclusions, E. chaffeensis-containing vesicles (ECVs), to evade from host cell innate immune responses and obtain nutrients. However, mechanisms exploited by host cells to inhibit E. chaffeensis growth in ECVs are still largely unknown. Here we demonstrate that host cells recognize E. chaffeensis Ech_1067, a penicillin-binding protein, and then upregulate the expression of PIT1, which is a phosphate transporter and transports phosphate from ECVs to the cytosol to inhibit bacterial growth. We found that host cells upregulate the PIT1 expression upon E. chaffeensis infection using transcriptome sequencing, qRT-PCR and Western blotting, and PIT1 is localized on the ECV membrane in infected THP-1 cells using confocal microscopy. Silence of PIT1 using shRNA enhances E. chaffeensis intracellular growth. Finally, we found that E. chaffeensis Ech_1067 induces the upregulation of PIT1 expression through the MyD88-NF-κB pathway using recombinant protein for stimulation and siRNA for silence. Our findings deepen the understanding of the innate immune responses of host cells to inhibit bacterial intracellular growth and facilitate the development of new therapeutics for HME.
摘要：
查菲埃里希菌在单核细胞或巨噬细胞内感染和增殖，并导致人单核细胞埃里希菌病（HME），一种正在出现的威胁生命的蜱传人畜共患病。内化后，E.Chaffeensis驻留在专门的膜结合内含物中，E.Chaffeensis-containingvesicles(ECVs),逃避宿主细胞先天免疫反应并获得营养。然而,宿主细胞在ECV中抑制Chaffeensis生长的机制仍然未知。在这里，我们证明宿主细胞识别E.chaffeensisEch_1067，一种青霉素结合蛋白，然后上调PIT1的表达，PIT1是一种磷酸盐转运蛋白，将磷酸盐从ECV转运到细胞质中以抑制细菌生长。我们发现，宿主细胞上调PIT1的表达时，使用转录组测序，qRT-PCR和蛋白质印迹，使用共聚焦显微镜将PIT1定位于感染的THP-1细胞的ECV膜上。使用shRNA的PIT1的沉默增强了查夫森大肠杆菌的细胞内生长。最后,我们发现，使用重组蛋白刺激和siRNA沉默，通过MyD88-NF-κB途径诱导PIT1表达上调。我们的发现加深了对宿主细胞抑制细菌细胞内生长的先天免疫反应的理解，并促进了HME新疗法的开发。
