Comerci D J, Martínez-Lorenzo M J, Sieira R, Gorvel J P, Ugalde R A
Instituto de Investigaciones Biotecnológicas, Universidad Nacional de General San Martín, CONICET, Avenida General Paz entre Constituyentes y Albarellos, San Martín 1650, Buenos Aires, Argentina.
Cell Microbiol. 2001 Mar;3(3):159-68. doi: 10.1046/j.1462-5822.2001.00102.x.
In epithelial cells, the intracellular pathogen Brucella abortus escapes from the endocytic pathway, exploits the autophagic machinery of the host cell and establishes a unique replication niche in the endoplasmic reticulum. The molecular mechanisms underlying these processes are still poorly understood. Recently, a B. abortus type IV-related secretion system encoded by the virB operon has been described as being involved in the intracellular trafficking of the bacteria. In this study, we have analysed the intracellular pathway of B. abortus virB10 mutant strains by confocal microscopy. We demonstrate that a functional virB operon is essential for the biogenesis of the Brucella-containing vacuole. Polar mutation preventing the transcription of virB10 and downstream sequences did not allow Brucella to bypass the endocytic pathway. Consequently, polar mutant-containing vacuoles fused with lysosomes in which bacteria underwent a degradation process. In contrast, virB10 non-polar mutants were capable of avoiding interactions with the endocytic pathway but, diverging to wild-type Brucella, were unable to reach the endoplasmic reticulum to establish their intracellular replication niche and seemed to be recycled to the cell surface. Based on the two particular phenotypes described in this work, a model of maturation of the Brucella-containing vacuole is proposed.
在上皮细胞中，细胞内病原体流产布鲁氏菌可逃离内吞途径，利用宿主细胞的自噬机制，并在内质网中建立独特的复制位点。这些过程背后的分子机制仍知之甚少。最近，由virB操纵子编码的一种与IV型相关的流产布鲁氏菌分泌系统被描述为参与细菌的细胞内运输。在本研究中，我们通过共聚焦显微镜分析了流产布鲁氏菌virB10突变株的细胞内途径。我们证明，功能性virB操纵子对于含布鲁氏菌液泡的生物发生至关重要。阻止virB10及下游序列转录的极性突变不允许布鲁氏菌绕过内吞途径。因此，含极性突变体的液泡与溶酶体融合，细菌在其中经历降解过程。相比之下，virB10非极性突变体能够避免与内吞途径相互作用，但与野生型流产布鲁氏菌不同，它们无法到达内质网以建立其细胞内复制位点，似乎被循环至细胞表面。基于本研究中描述的两种特殊表型，我们提出了一个含布鲁氏菌液泡成熟的模型。
