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Proc Natl Acad Sci U S A. 2005 Feb 1;102(5):1673-8. Epub 2005 Jan 4.

Brucella coopts the small GTPase Sar1 for intracellular replication.

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Centre d'Immunologie de Marseille-Luminy, Institut National de la Santé et de la Recherche Médicale/Centre National de la Recherche Scientifique/Université delaMéditerranée, 13288 Marseille Cedex 09, France.


The pathogen Brucella abortus resides inside macrophages within a unique, replication-permissive organelle that is derived from the endoplasmic reticulum (ER). Although dependent on the Brucella type IV secretion system VirB, the mechanisms governing the biogenesis of this compartment remain elusive. Here, we investigated a putative role of the early secretory pathway in ER membrane accretion by the Brucella-containing vacuoles (BCVs). We show that BCVs interact with ER exit sites (ERES), and blockade of Sar1 activity, which disrupts ERES, prevents intracellular replication of Brucella. In cells expressing the dominant interfering form Sar1[T39N], BCVs do not acquire ER membranes, suggesting that they are unable to mature into replicative organelles. By contrast, treatments that block subsequent secretory events do not affect bacterial replication. We propose that Sar1-dependent ERES functions, but not subsequent secretory events, are essential for the biogenesis of the Brucella replicative compartment and, thus, bacterial replication. These results assign an essential role for Sar1 in pathogenesis of an intracellular bacterium.

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