Cellular Prion Protein PromotesBrucellaInfection into Macrophages

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.

Evidence of Brucella abortus OPS dictating uptake and restricting NF-κB activation in murine macrophages

“…Possible host cell surface receptors for Brucella have been recently identified [8][9][10], but the role of cellular prion protein in Brucella uptake remains questionable [11]. Brucella virulence factors involved in bacterial invasion have not been clearly defined.…”

Roles of Brucella abortus SpoT in morphological differentiation and intramacrophagic replication

“…Neither virulence factors that allow intracellular survival of Brucella species nor the specific factors that induce such virulence have been elucidated. B. abortus is internalized by macrophages by swimming on the cell surface with generalized membrane ruffling for several minutes, a process termed 'swimming internalization', after which the bacteria are enclosed by macropinosomes (Watarai et al, 2002a).Recently we showed that Hsp60, a member of the GroEL family of chaperonins, of B. abortus is secreted on the bacterial surface through a type IV system and can interact with the cellular prion protein (PrP G ) on macrophages (Watarai et al, 2003 vacuoles rapidly fuse with early autophagosomes that acquire vacuolar H + -ATPase and lysosome-associated membrane proteins (LAMPs), mature into late autophagosomes, inhibit fusion with lysosomes and finally become replicating vacuoles, normally associated with the endoplasmic reticulum (Comerci et al, 2001; Pizarro-Cerda et al, 1998a, b). The genetic basis of B.abortus virulence is still poorly understood.…”

“…The sub-bacteriostatic and sublethal concentrations of chloramphenicol were 1 and 25 mg ml 21 , respectively. Bacterial suspensions were incubated in a shaker at 37 uC for 9 h; the resulting cultured bacteria were heat-fixed, Gram stained and observed by phase-contrast or bright-field microscopy (Olympus; magnification 61000).Bacterial morphology within macrophages was assessed by using a modification of the method of Kim et al (2003). Infected macrophages were fixed in 4 % periodate/lysine/paraformaldehyde/sucrose for 1 h at 37 uC.…”

“…All B. abortus strains were from smooth virulent B. abortus biovar 1 strain 544 (ATCC 23448). The isogenic mutant of B. abortus 544 spoT : : Tn5Km2 has been described by Kim et al (2003). B. abortus strains were maintained as frozen glycerol stocks and were cultured in Brucella broth (Becton Dickinson) or Brucella broth containing 1?5 % agar.…”

Bartonella and Brucella--Weapons and Strategies for Stealth Attack

“…Entry is mediated by surface-exposed bacterial and host membrane complexes at cholesteroland glycosylphosphoinositide (GPI)-rich hostcell membrane domains (lipid rafts) (PizarroCerda et al 1998;Watarai et al 2002Watarai et al , 2003Kim et al 2004;Nakato et al 2012) in a phosphoinositide (PI)-3 kinase, actin, ezrin, Rho, Rac, Cdc42, and/or Toll-like receptor (TLR)4-dependent manner (Fig. 2) (Guzman-Verri et al 2001;Chaves-Olarte et al 2002;Watanabe et al 2009).…”