title: Modulation of Brucella-induced macropinocytosis by lipid rafts mediates intracellular replication.
abstract: Intracellular replication of Brucella requires the VirB complex, which is highly similar to conjugative DNA transfer systems. In this study, we show that Brucella internalizes into macrophages by swimming on the cell surface with generalized membrane ruffling for several minutes, after which the bacteria are enclosed by macropinosomes. Lipid raft-associated molecules such as glycosylphosphatidylinositol (GPI)-anchored proteins, GM1 gangliosides and cholesterol were selectively incorporated into macropinosomes containing Brucella. In contrast, lysosomal glycoprotein LAMP-1 and host cell transmembrane protein CD44 were excluded from the macropinosomes. Removing GPI-anchored proteins from the macrophage surface and cholesterol sequestration markedly inhibited the VirB-dependent macropinocytosis and intracellular replication. Our results suggest that the entry route of Brucella into the macrophage determines the intracellular fate of the bacteria that is modulated by lipid raft microdomains.
authors.affiliation: Department of Veterinary Microbiology, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan. watarai@obihiro.ac.jp
authors.forename: Masahisa
authors.initials: M
authors.lastname: Watarai
authors.forename: Sou-Ichi
authors.initials: S
authors.lastname: Makino
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Fujii
authors.forename: Keinosuke
authors.initials: K
authors.lastname: Okamoto
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Shirahata
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology*; D002003:Brucella abortus / Q000502:physiology*; D002450:Cell Communication; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism; D005260:Female; D005732:Gangliosides / Q000378:metabolism; D017261:Glycosylphosphatidylinositols / Q000378:metabolism; D016952:Legionella pneumophila / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism; D008561:Membrane Fusion / Q000502:physiology; D051379:Mice; D010873:Pinocytosis; D037521:Virulence Factors
chemical_list: D001426:Bacterial Proteins; D005732:Gangliosides; D017261:Glycosylphosphatidylinositols; D037521:Virulence Factors; D002784:Cholesterol