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Macrophage plasma membrane cholesterol contributes to Brucella abortus infection of mice
Masahisa Watarai1, Sou-ichi Makino, Makoto Michikawa
1Department of Veterinary Microbiology, Obihiro University of Agriculture and Veterinary Medicine, Obihiro-shi, Hokkaido 080-8555, Japan. watarai@obihiro.ac.jp
Abstract:
Brucella abortus is a facultative intracellular bacterium capable of surviving inside macrophages. Intracellular replication of B. abortus requires the VirB complex, which is highly similar to conjugative DNA transfer systems. In this study, we show that plasma membrane cholesterol of macrophages is required for the VirB-dependent internalization of B. abortus and also contributes to the establishment of bacterial infection in mice. The internalization of B. abortus was accelerated by treating macrophages with acetylated low-density lipoprotein (acLDL). Treatment of acyl coenzyme A:cholesterol acyltransferase inhibitor, HL-004, to macrophages preloaded with acLDL accelerated the internalization of B. abortus. Ketoconazole, which inhibits cholesterol transport from lysosomes to the cell surface, inhibited the internalization and intracellular replication of B. abortus in macrophages. The Niemann-Pick C1 gene (NPC1), the gene for Niemann-Pick type C disease, characterized by an accumulation of cholesterol in most tissues, promoted B. abortus infection. NPC1-deficient mice were resistant to the bacterial infection. Molecules associated with cholesterol-rich microdomains, "lipid rafts," accumulate in intracellular vesicles of macrophages isolated from NPC1-deficient mice, and the macrophages yielded no intracellular replication of B. abortus. Thus, trafficking of cholesterol-associated microdomains controlled by NPC1 is critical for the establishment of B. abortus infection.
Insights
Cholesterol in macrophage membranes is essential for Brucella abortus internalization and infection. Disrupting cholesterol transport or Niemann-Pick C1 gene function hinders bacterial survival and replication.
Area of Science:
- Microbiology
- Cell Biology
- Immunology
Background:
- Brucella abortus is an intracellular bacterium that survives within macrophages.
- B. abortus intracellular replication depends on the VirB complex, similar to DNA transfer systems.
Purpose of the Study:
- To investigate the role of macrophage plasma membrane cholesterol in B. abortus internalization and infection establishment.
- To determine the impact of cholesterol transport and Niemann-Pick C1 (NPC1) on B. abortus pathogenesis.
Main Methods:
- Macrophages were treated with acetylated low-density lipoprotein (acLDL) and cholesterol transport inhibitors (HL-004, ketoconazole).
- B. abortus internalization and intracellular replication were assessed in treated macrophages.
- Niemann-Pick C1 (NPC1)-deficient mice and their macrophages were used to evaluate B. abortus infection resistance.
Main Results:
- Macrophage plasma membrane cholesterol is required for VirB-dependent B. abortus internalization.
- acLDL treatment and HL-004 accelerated B. abortus internalization, while ketoconazole inhibited it.
- NPC1 deficiency conferred resistance to B. abortus infection, with macrophages showing impaired bacterial replication and accumulation of lipid rafts.
Conclusions:
- Macrophage cholesterol is critical for B. abortus entry and VirB complex function.
- NPC1-mediated cholesterol trafficking is essential for establishing B. abortus infection.
- Targeting cholesterol homeostasis presents a potential strategy against Brucella infections.