The Salmonella spvB virulence gene encodes an enzyme that ADP‐ribosylates actin and destabilizes the cytoskeleton of eukaryotic cells

Abstract

SummaryADP-ribosylating enzymes, such as cholera and diphtheria toxins, are key virulence factors for a variety of extracellular bacterial pathogens but have not been implicated previously during intracellular pathogenesis. Salmonella strains are capable of invading epithelial cells and localizing in macrophages during infection. The spvB virulence gene of Salmonella is required for human macrophage cytotoxicity in vitro and for enhancing intracellular bacterial proliferation during infection. Here, we present evidence that spvB encodes an ADP-ribosylating enzyme that uses actin as a substrate and depolymerizes actin filaments when expressed in CHO cells. Furthermore, site-directed mutagenesis demonstrates that the ADPribosylating activity of SpvB is essential for Salmonella virulence in mice. As spvB is expressed by Salmonella strains after invasion of epithelial cells or phagocytosis by macrophages, these results suggest that SpvB functions as an intracellular ADP-ribosylating toxin critical for the pathogenesis of Salmonella infections.

Functional high-throughput screening identifies the miR-15 microRNA family as cellular restriction factors for Salmonella infection

“…The SpvB protein, an effector encoded by the Salmonella virulence plasmid, is delivered into the host cytosol via the SPI-2 T3SS and has been shown to induce actin depolymerization via its ADP-ribosyltransferase activity [46][47][48] . Considering that compounds that interfere with actin polymerization have been shown to induce G2/M arrest 49,50 , it is conceivable that the effect of SpvB on cell cycle progression is connected to its actin depolymerization activity.…”

Cell invasion of poultry-associated Salmonella enterica serovar Enteritidis isolates is associated with pathogenicity, motility and proteins secreted by the type III secretion system

“…For instance, differences in the virulence potential between S. Enteritidis isolates within the same phage types and even within the same clonal lineages have been reported (Olsen Field isolates of S. Enteritidis contain a serovar-specific high-molecular-mass plasmid (pSEV) that encodes spvRABCD (Salmonella plasmid virulence) genes (Rychlík et al, 2006;Rotger & Casadesú s, 1999). pSEV contributes to systemic infection of mice but not chickens (Bakshi et al, 2003;Nakamura et al, 1985), and spvB, in particular, plays a role in the pathogenesis by ribosylating actin of the macrophages and destabilizing the cytoskeleton (Lesnick et al, 2001;Otto et al, 2000;Tezcan-Merdol et al, 2001). Thus, identification of individual genes of the spv operon from S. Enteritidis is commonly used as a marker to assess the status of pSEV in field isolates (Rodríguez et al, 1998;Rychlík et al, 2008;Soto et al, 2003Soto et al, , 2006.…”

Effectors of Salmonella Pathogenicity Island 2: An Island crucial to the life of Salmonella

“…For example, the plasmid encoded SPI2 effector SpvB aids in vacuole-associated actin polymerization and destabilizes host cell cytoskeleton by ADP ribosylating actin and finally results in cytotoxicity. 20 SteC is a kinase that causes the assembly of F-actin meshwork around SCV. 21 Contrastingly, SspH2 is involved in actin dissociation by binding to actin cross-linking protein filamin and G-actin binding protein, profilin.…”