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Brucella coopts the small GTPase Sar1 for intracellular replication
Jean Celli1, Suzana P Salcedo, Jean-Pierre Gorvel
1Centre 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. jcelli@niaid.nih.gov
Summary
Brucella abortus uses Sar1-dependent ER exit sites for pathogen vacuole biogenesis. Blocking Sar1 prevents vacuole maturation and bacterial replication within macrophages.
Area of Science:
- Cell Biology
- Microbiology
- Pathogenesis
Background:
- Brucella abortus forms a replication-permissive organelle from the endoplasmic reticulum (ER) within host macrophages.
- The biogenesis of this Brucella-containing vacuole (BCV) depends on the VirB type IV secretion system, but the precise mechanisms are unclear.
Purpose of the Study:
- To investigate the role of the early secretory pathway, specifically ER exit sites (ERES), in the formation and maturation of the BCV.
- To determine if Sar1, a key regulator of ERES, is essential for BCV biogenesis and intracellular Brucella replication.
Main Methods:
- Studied the interaction between BCVs and ERES in infected macrophages.
- Utilized Sar1 activity blockade (using Sar1[T39N]) to disrupt ERES function.
- Assessed the impact of ERES disruption on BCV membrane acquisition and bacterial replication.
Main Results:
- BCVs were observed to interact with ERES.
- Blocking Sar1 activity prevented BCVs from acquiring ER membranes and maturing into replicative organelles.
- Disruption of ERES function led to the inhibition of intracellular Brucella replication.
Conclusions:
- Sar1-dependent ERES function is critical for the biogenesis of the Brucella replicative vacuole.
- Subsequent steps in the secretory pathway are not essential for this process.
- Sar1 plays a vital role in the pathogenesis of Brucella abortus.