Membrane Chaperone SecDF Plays a Role in the Secretion of Listeria monocytogenes Major Virulence Factors
Membrane Chaperone SecDF Plays a Role in the Secretion of Listeria monocytogenes Major Virulence Factors
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DOI：
10.1128/jb.00697-13
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发表时间：
2013-12-01
影响因子：
3.2
通讯作者：
Herskovits, Anat A.
中科院分区：
文献类型：
--
作者：
Burg-Golani, Tamar;Pozniak, Yair;Herskovits, Anat A.
单核细胞增生李斯特菌是一种革兰氏阳性人类细胞内病原体，可感染多种哺乳动物细胞。入侵后，单增李斯特菌会分泌多种针对宿主细胞过程并促进感染的毒力因子。据推测，Sec 易位系统是这种分泌的主要介质，但尚未根据经验确定。在这里，我们验证了 SecDF（Sec 系统的一个组成部分）在几种关键的单核细胞增生李斯特菌毒力因子的分泌中的重要作用。 Delta secDF 突变体被证明表现出李斯特氏菌溶血素 O (LLO)、PlcA、PlcB 和 ActA 的膜易位受损，这些因子介导单核细胞增生李斯特菌吞噬体逃逸并在细胞间传播。通过细菌膜上因子的积累和分泌时活性的降低来监测这种受损的易位。尽管在实验室培养基中生长正常，但这种分泌缺陷与巨噬细胞中 Delta secDF 突变体的严重细胞内生长缺陷以及小鼠中毒性较低的表型有关。我们进一步表明，当细菌驻留在巨噬细胞吞噬体中时，SecDF 会上调，并且它对于有效的吞噬体逃逸是必要的。总而言之，这些数据支持这样的前提：SecDF 作为伴侣，促进单核细胞增生李斯特菌毒力因子在感染过程中的易位。
Listeria monocytogenes is a Gram-positive human intracellular pathogen that infects diverse mammalian cells. Upon invasion, L. monocytogenes secretes multiple virulence factors that target host cellular processes and promote infection. It has been presumed, but was not empirically established, that the Sec translocation system is the primary mediator of this secretion. Here, we validate an important role for SecDF, a component of the Sec system, in the secretion of several critical L. monocytogenes virulence factors. A Delta secDF mutant is demonstrated to exhibit impaired membrane translocation of listeriolysin O (LLO), PlcA, PlcB, and ActA, factors that mediate L. monocytogenes phagosomal escape and spread from cell to cell. This impaired translocation was monitored by accumulation of the factors on the bacterial membrane and by reduced activity upon secretion. This defect in secretion is shown to be associated with a severe intracellular growth defect of the Delta secDF mutant in macrophages and a less virulent phenotype in mice, despite normal growth in laboratory medium. We further show that SecDF is upregulated when the bacteria reside in macrophage phagosomes and that it is necessary for efficient phagosomal escape. Taken together, these data support the premise that SecDF plays a role as a chaperone that facilitates the translocation of L. monocytogenes virulence factors during infection.