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Cellular prion protein promotes Brucella infection into macrophages.

Watarai M, Kim S, Erdenebaatar J, Makino S, Horiuchi M, Shirahata T, Sakaguchi S, Katamine S - J. Exp. Med. (2003)

Bottom Line: Hsp60 reacted strongly with serum from human brucellosis patients and was exposed on the bacterial surface via a VirB complex-associated process.Under in vitro and in vivo conditions, Hsp60 of B. abortus bound to PrPC.These results indicate that signal transduction induced by the interaction between bacterial Hsp60 and PrPC on macrophages contributes to the establishment of B. abortus infection.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Veterinary Science, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro-shi, Hokkaido 080-8555, Japan. watarai@obihiro.ac.jp

ABSTRACT
The products of the Brucella abortus virB gene locus, which are highly similar to conjugative DNA transfer system, enable the bacterium to replicate within macrophage vacuoles. The replicative phagosome is thought to be established by the interaction of a substrate of the VirB complex with macrophages, although the substrate and its host cellular target have not yet been identified. We report here that Hsp60, a member of the GroEL family of chaperonins, of B. abortus is capable of interacting directly or indirectly with cellular prion protein (PrPC) on host cells. Aggregation of PrPC tail-like formation was observed during bacterial swimming internalization into macrophages and PrPC was selectively incorporated into macropinosomes containing B. abortus. Hsp60 reacted strongly with serum from human brucellosis patients and was exposed on the bacterial surface via a VirB complex-associated process. Under in vitro and in vivo conditions, Hsp60 of B. abortus bound to PrPC. Hsp60 of B. abortus, expressed on the surface of Lactococcus lactis, promoted the aggregation of PrPC but not PrPC tail formation on macrophages. The PrPC deficiency prevented swimming internalization and intracellular replication of B. abortus, with the result that phagosomes bearing the bacteria were targeted into the endocytic network. These results indicate that signal transduction induced by the interaction between bacterial Hsp60 and PrPC on macrophages contributes to the establishment of B. abortus infection.

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PrPC-regulated swimming internalization of B. abortus. (A and B) Selected time lapse videomicroscopic images of wild-type B. abortus entry into macrophages from normal (A) or PrPC-deficient C57BL/6 mice (B). Elapsed time in minutes is indicated at the bottom of each frame. Arrows point to bacteria. (C) Generalized actin polymerization after contact of macrophages with B. abortus. Bacteria were deposited onto macrophages from normal (top) or PrPC-deficient mice (bottom) and then incubated for 5 min, fixed, and stained for actin filaments. Phase contrast microscopy of the corresponding microscopic fields are shown. Arrows point to bacteria.
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fig6: PrPC-regulated swimming internalization of B. abortus. (A and B) Selected time lapse videomicroscopic images of wild-type B. abortus entry into macrophages from normal (A) or PrPC-deficient C57BL/6 mice (B). Elapsed time in minutes is indicated at the bottom of each frame. Arrows point to bacteria. (C) Generalized actin polymerization after contact of macrophages with B. abortus. Bacteria were deposited onto macrophages from normal (top) or PrPC-deficient mice (bottom) and then incubated for 5 min, fixed, and stained for actin filaments. Phase contrast microscopy of the corresponding microscopic fields are shown. Arrows point to bacteria.

Mentions: To investigate the role of PrPC on B. abortus infection, several phenotypes of B. abortus virulence were tested by using macrophages from Ngsk PrPC-deficient mice (16). Time lapse videomicroscopy was used to follow the internalization of B. abortus by macrophages from parent or Ngsk PrPC-deficient C57BL/6 mice. After contact of macrophages with B. abortus, bacteria showed swimming internalization in macrophages from parent mice (Fig. 6 A). The swimming of the bacteria on the macrophage surface lasted for several minutes with generalized plasma membrane ruffling before eventual enclosure in macropinosomes (Fig. 6 A). Contact of B. abortus with macrophages from Ngsk PrPC-deficient mice, in contrast, resulted in much smaller ruffling that was restricted to the area near the bacteria. The ruffles associated with internalization of bacteria resulted in a more rapid uptake than observed for macrophages from parent mice (Fig. 6 B). 5 min after deposition on the macrophages from parent mice, B. abortus showed generalized actin polymerization around the site of bacterial binding, which could be observed by either phalloidin staining or phase contrast microscopy (Fig. 6 C). Macrophages from Ngsk PrPC-deficient mice showed primarily small regions of phalloidin staining at sites of bacterial binding (Fig. 6 C).


Cellular prion protein promotes Brucella infection into macrophages.

Watarai M, Kim S, Erdenebaatar J, Makino S, Horiuchi M, Shirahata T, Sakaguchi S, Katamine S - J. Exp. Med. (2003)

PrPC-regulated swimming internalization of B. abortus. (A and B) Selected time lapse videomicroscopic images of wild-type B. abortus entry into macrophages from normal (A) or PrPC-deficient C57BL/6 mice (B). Elapsed time in minutes is indicated at the bottom of each frame. Arrows point to bacteria. (C) Generalized actin polymerization after contact of macrophages with B. abortus. Bacteria were deposited onto macrophages from normal (top) or PrPC-deficient mice (bottom) and then incubated for 5 min, fixed, and stained for actin filaments. Phase contrast microscopy of the corresponding microscopic fields are shown. Arrows point to bacteria.
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Related In: Results  -  Collection

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fig6: PrPC-regulated swimming internalization of B. abortus. (A and B) Selected time lapse videomicroscopic images of wild-type B. abortus entry into macrophages from normal (A) or PrPC-deficient C57BL/6 mice (B). Elapsed time in minutes is indicated at the bottom of each frame. Arrows point to bacteria. (C) Generalized actin polymerization after contact of macrophages with B. abortus. Bacteria were deposited onto macrophages from normal (top) or PrPC-deficient mice (bottom) and then incubated for 5 min, fixed, and stained for actin filaments. Phase contrast microscopy of the corresponding microscopic fields are shown. Arrows point to bacteria.
Mentions: To investigate the role of PrPC on B. abortus infection, several phenotypes of B. abortus virulence were tested by using macrophages from Ngsk PrPC-deficient mice (16). Time lapse videomicroscopy was used to follow the internalization of B. abortus by macrophages from parent or Ngsk PrPC-deficient C57BL/6 mice. After contact of macrophages with B. abortus, bacteria showed swimming internalization in macrophages from parent mice (Fig. 6 A). The swimming of the bacteria on the macrophage surface lasted for several minutes with generalized plasma membrane ruffling before eventual enclosure in macropinosomes (Fig. 6 A). Contact of B. abortus with macrophages from Ngsk PrPC-deficient mice, in contrast, resulted in much smaller ruffling that was restricted to the area near the bacteria. The ruffles associated with internalization of bacteria resulted in a more rapid uptake than observed for macrophages from parent mice (Fig. 6 B). 5 min after deposition on the macrophages from parent mice, B. abortus showed generalized actin polymerization around the site of bacterial binding, which could be observed by either phalloidin staining or phase contrast microscopy (Fig. 6 C). Macrophages from Ngsk PrPC-deficient mice showed primarily small regions of phalloidin staining at sites of bacterial binding (Fig. 6 C).

Bottom Line: Hsp60 reacted strongly with serum from human brucellosis patients and was exposed on the bacterial surface via a VirB complex-associated process.Under in vitro and in vivo conditions, Hsp60 of B. abortus bound to PrPC.These results indicate that signal transduction induced by the interaction between bacterial Hsp60 and PrPC on macrophages contributes to the establishment of B. abortus infection.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Veterinary Science, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro-shi, Hokkaido 080-8555, Japan. watarai@obihiro.ac.jp

ABSTRACT
The products of the Brucella abortus virB gene locus, which are highly similar to conjugative DNA transfer system, enable the bacterium to replicate within macrophage vacuoles. The replicative phagosome is thought to be established by the interaction of a substrate of the VirB complex with macrophages, although the substrate and its host cellular target have not yet been identified. We report here that Hsp60, a member of the GroEL family of chaperonins, of B. abortus is capable of interacting directly or indirectly with cellular prion protein (PrPC) on host cells. Aggregation of PrPC tail-like formation was observed during bacterial swimming internalization into macrophages and PrPC was selectively incorporated into macropinosomes containing B. abortus. Hsp60 reacted strongly with serum from human brucellosis patients and was exposed on the bacterial surface via a VirB complex-associated process. Under in vitro and in vivo conditions, Hsp60 of B. abortus bound to PrPC. Hsp60 of B. abortus, expressed on the surface of Lactococcus lactis, promoted the aggregation of PrPC but not PrPC tail formation on macrophages. The PrPC deficiency prevented swimming internalization and intracellular replication of B. abortus, with the result that phagosomes bearing the bacteria were targeted into the endocytic network. These results indicate that signal transduction induced by the interaction between bacterial Hsp60 and PrPC on macrophages contributes to the establishment of B. abortus infection.

Show MeSH
Related in: MedlinePlus