Mohapatra Nrusingh P, Balagopal Ashwin, Soni Shilpa, Schlesinger Larry S, Gunn John S
Center for Microbial Interface Biology, Department of Molecular Virology, Immunology, and Medical Genetics, and Department of Internal Medicine, Division of Infectious Diseases, The Ohio State University, Columbus, Ohio 43210, USA.
Infect Immun. 2007 Jan;75(1):390-6. doi: 10.1128/IAI.01226-06. Epub 2006 Oct 23.
AcpA of Francisella spp. is a respiratory-burst-inhibiting acid phosphatase that also exhibits phospholipase C activity. To better understand the molecular basis of AcpA in virulence, a deletion of acpA was constructed in Francisella novicida. The phosphatase and lipase activities were reduced 10-fold and 8-fold, respectively, in the acpA mutant compared to the wild type and were found mostly associated with the outer membrane. The acpA mutant was more susceptible to intracellular killing than the wild-type strain in the THP-1 human macrophage-like cell line. In addition, mice infected with the acpA mutant survived longer than the wild-type strain and were less fit than the wild-type strain in competition infection assays. Transmission electron microscopy showed that the acpA mutant was delayed in escape from macrophage phagosomes, as more than 75% of acpA mutant bacteria could still be found inside phagosomes after 12 h of infection in THP-1 cells and human monocyte-derived macrophages, whereas most of the wild-type bacteria had escaped from the phagosome by 6 h postinfection. Thus, AcpA affects intracellular trafficking and the fate of Francisella within host macrophages.
弗朗西斯菌属的AcpA是一种抑制呼吸爆发的酸性磷酸酶，同时也具有磷脂酶C活性。为了更好地理解AcpA在毒力方面的分子基础，在新凶手弗朗西斯菌中构建了acpA缺失株。与野生型相比，acpA突变株的磷酸酶和脂肪酶活性分别降低了10倍和8倍，且大多与外膜相关。在THP-1人巨噬细胞样细胞系中，acpA突变株比野生型菌株更易受到细胞内杀伤。此外，感染acpA突变株的小鼠比感染野生型菌株的小鼠存活时间更长，并且在竞争感染试验中比野生型菌株更不适应。透射电子显微镜显示，acpA突变株从巨噬细胞吞噬体中逃逸的过程延迟，因为在THP-1细胞和人单核细胞衍生的巨噬细胞感染12小时后，仍有超过75%的acpA突变株细菌可在吞噬体内被发现，而大多数野生型细菌在感染后6小时就已从吞噬体中逃逸。因此，AcpA影响弗朗西斯菌在宿主巨噬细胞内的转运和命运。
