Group A Streptococcus NAD-Glycohydrolase Inhibits Caveolin 1-Mediated Internalization Into Human Epithelial Cells.
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ABSTRACT:
SUBMITTER: Toh H
PROVIDER: S-EPMC6893971 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:A global increase in invasive infections due to group A Streptococcus (S. pyogenes or GAS) has been observed since the 1980s, associated with emergence of a clonal group of strains of the M1T1 serotype. Among other virulence attributes, the M1T1 clone secretes NAD+-glycohydrolase (NADase). When GAS binds to epithelial cells in vitro, NADase is translocated into the cytosol in a process mediated by streptolysin O (SLO), and expression of these two toxins is associated with enhanced GAS intracellular survival. Because SLO is required for NADase translocation, it has been difficult to distinguish pathogenic effects of NADase from those of SLO. To resolve the effects of the two proteins, we made use of anthrax toxin as an alternative means to deliver NADase to host cells, independently of SLO. We developed a novel method for purification of enzymatically active NADase fused to an amino-terminal fragment of anthrax toxin lethal factor (LFn-NADase) that exploits the avid, reversible binding of NADase to its endogenous inhibitor. LFn-NADase was translocated across a synthetic lipid bilayer in vitro in the presence of anthrax toxin protective antigen in a pH-dependent manner. Exposure of human oropharyngeal keratinocytes to LFn-NADase in the presence of protective antigen resulted in cytosolic delivery of NADase activity, inhibition of protein synthesis, and cell death, whereas a similar construct of an enzymatically inactive point mutant had no effect. Anthrax toxin-mediated delivery of NADase in an amount comparable to that observed during in vitro infection with live GAS rescued the defective intracellular survival of NADase-deficient GAS and increased the survival of SLO-deficient GAS. Confocal microscopy demonstrated that delivery of LFn-NADase prevented intracellular trafficking of NADase-deficient GAS to lysosomes. We conclude that NADase mediates cytotoxicity and promotes intracellular survival of GAS in host cells.
| S-EPMC4777570 | biostudies-literature
Project description:Group A Streptococcus (GAS) is a human pathogen causing a wide spectrum of diseases, from mild pharyngitis to life-threatening necrotizing fasciitis. GAS has been shown to evade host immune killing by invading host cells. However, how GAS resists intracellular killing by endothelial cells is still unclear. In this study, we found that strains NZ131 and A20 have higher activities of NADase and intracellular multiplication than strain SF370 in human endothelial cells (HMEC-1). Moreover, nga mutants of NZ131 (SW957 and SW976) were generated to demonstrate that NADase activity is required for the intracellular growth of GAS in endothelial cells. We also found that intracellular levels of NAD+ and the NAD+/NADH ratio of NZ131-infected HMEC-1 cells were both lower than in cells infected by the nga mutant. Although both NZ131 and its nga mutant were trapped by LC3-positive vacuoles, only nga mutant vacuoles were highly co-localized with acidified lysosomes. On the other hand, intracellular multiplication of the nga mutant was increased by bafilomycin A1 treatment. These results indicate that NADase causes intracellular NAD+ imbalance and impairs acidification of autophagosomes to escape autophagocytic killing and enhance multiplication of GAS in endothelial cells.
| S-EPMC6085451 | biostudies-literature
Project description:Streptococcus pyogenes uses the cytolysin streptolysin O (SLO) to translocate an enzyme, the S. pyogenes NAD(+) glycohydrolase (SPN), into the host cell cytosol. However, the function of SPN in this compartment is not known. As a complication, many S. pyogenes strains express a SPN variant lacking NAD(+) glycohydrolase (NADase) activity. Here, we show that SPN modifies several SLO- and NAD(+) -dependent host cell responses in patterns that correlate with NADase activity. SLO pore formation results in hyperactivation of the cellular enzyme poly-ADP-ribose polymerase-1 (PARP-1) and production of polymers of poly-ADP-ribose (PAR). However, while SPN NADase activity moderates PARP-1 activation and blocks accumulation of PAR, these processes continued unabated in the presence of NADase-inactive SPN. Temporal analyses revealed that while PAR production is initially independent of NADase activity, PAR rapidly disappears in the presence of NADase-active SPN, host cell ATP is depleted and the pro-inflammatory mediator high-mobility group box-1 (HMGB1) protein is released from the nucleus by a PARP-1-dependent mechanism. In contrast, HMGB1 is not released in response to NADase-inactive SPN and instead the cells release elevated levels of interleukin-8 and tumour necrosis factor-α. Thus, SPN and SLO combine to induce cellular responses subsequently influenced by the presence or absence of NADase activity.
| S-EPMC4624300 | biostudies-literature
Project description:Group A Streptococcus (Streptococcus pyogenes or GAS) causes pharyngitis, severe invasive infections, and the post-infectious syndromes of glomerulonephritis and rheumatic fever. GAS can be internalized and killed by epithelial cells in vitro, a process that may contribute to local innate defense against pharyngeal infection. Secretion of the pore-forming toxin streptolysin O (SLO) by GAS has been reported to stimulate targeted autophagy (xenophagy) upon internalization of the bacteria by epithelial cells. Whereas this process was associated with killing of GAS in HeLa cells, studies in human keratinocytes found SLO production enhanced intracellular survival. To reconcile these conflicting observations, we now report in-depth investigation of xenophagy in response to GAS infection of human oropharyngeal keratinocytes, the predominant cell type of the pharyngeal epithelium. We found that SLO expression was associated with prolonged intracellular survival; unexpectedly, expression of the co-toxin NADase was required for this effect. Enhanced intracellular survival was lost upon deletion of NADase or inactivation of its enzymatic activity. Shortly after internalization of GAS by keratinocytes, SLO-mediated damage to the bacteria-containing vacuole resulted in exposure to the cytosol, ubiquitination of GAS and/or associated vacuolar membrane remnants, and engulfment of GAS in LC3-positive vacuoles. We also found that production of streptolysin S could mediate targeting of GAS to autophagosomes in the absence of SLO, a process accompanied by galectin 8 binding to damaged GAS-containing endosomes. Maturation of GAS-containing autophagosome-like vacuoles to degradative autolysosomes was prevented by SLO pore-formation and by SLO-mediated translocation of enzymatically active NADase into the keratinocyte cytosol. We conclude that SLO stimulates xenophagy in pharyngeal keratinocytes, but the coordinated action of SLO and NADase prevent maturation of GAS-containing autophagosomes, thereby prolonging GAS intracellular survival. This novel activity of NADase to block autophagic killing of GAS in pharyngeal cells may contribute to pharyngitis treatment failure, relapse, and chronic carriage.
| S-EPMC3675196 | biostudies-literature
Project description:UnlabelledGroup A Streptococcus (GAS, Streptococcus pyogenes) is an ongoing threat to human health as the agent of streptococcal pharyngitis, skin and soft tissue infections, and life-threatening conditions such as necrotizing fasciitis and streptococcal toxic shock syndrome. In animal models of infection, macrophages have been shown to contribute to host defense against GAS infection. However, as GAS can resist killing by macrophages in vitro and induce macrophage cell death, it has been suggested that GAS intracellular survival in macrophages may enable persistent infection. Using isogenic mutants, we now show that the GAS pore-forming toxin streptolysin O (SLO) and its cotoxin NAD-glycohydrolase (NADase) mediate GAS intracellular survival and cytotoxicity for macrophages. Unexpectedly, the two toxins did not inhibit fusion of GAS-containing phagosomes with lysosomes but rather prevented phagolysosome acidification. SLO served two essential functions, poration of the phagolysosomal membrane and translocation of NADase into the macrophage cytosol, both of which were necessary for maximal GAS intracellular survival. Whereas NADase delivery to epithelial cells is mediated by SLO secreted from GAS bound to the cell surface, in macrophages, the source of SLO and NADase is GAS contained within phagolysosomes. We found that transfer of NADase from the phagolysosome to the macrophage cytosol occurs not by simple diffusion through SLO pores but rather by a specific translocation mechanism that requires the N-terminal translocation domain of NADase. These results illuminate the mechanisms through which SLO and NADase enable GAS to defeat macrophage-mediated killing and provide new insight into the virulence of a major human pathogen.ImportanceMacrophages constitute an important element of the innate immune response to mucosal pathogens. They ingest and kill microbes by phagocytosis and secrete inflammatory cytokines to recruit and activate other effector cells. Group A Streptococcus (GAS, Streptococcus pyogenes), an important cause of pharyngitis and invasive infections, has been shown to resist killing by macrophages. We find that GAS resistance to macrophage killing depends on the GAS pore-forming toxin streptolysin O (SLO) and its cotoxin NAD-glycohydrolase (NADase). GAS bacteria are internalized by macrophage phagocytosis but resist killing by secreting SLO, which damages the phagolysosome membrane, prevents phagolysosome acidification, and translocates NADase from the phagolysosome into the macrophage cytosol. NADase augments SLO-mediated cytotoxicity by depleting cellular energy stores. These findings may explain the nearly universal production of SLO by GAS clinical isolates and the association of NADase with the global spread of a GAS clone implicated in invasive infections.
| S-EPMC4172074 | biostudies-literature
Project description:Streptococcus pyogenes is an important pathogen that causes a variety of diseases. The most common infections involve the throat (pharyngitis) or skin (impetigo); however, the factors that determine tissue tropism and severity are incompletely understood. The S. pyogenes NAD(+) glycohydrolase (SPN) is a virulence factor that has been implicated in contributing to the pathogenesis of severe infections. However, the role of SPN in determining the bacterium's tissue tropism has not been evaluated. In this report, we examine the sequences of spn and its endogenous inhibitor ifs from a worldwide collection of S. pyogenes strains. Analysis of average pairwise nucleotide diversity, average number of nucleotide differences, and ratio of nonsynonymous to synonymous substitutions revealed significant diversity in spn and ifs. Application of established models of molecular evolution shows that SPN is evolving under positive selection and diverging into NAD(+) glycohydrolase (NADase)-active and -inactive subtypes. Additionally, the NADase-inactive SPN subtypes maintain the characteristics of a functional gene while ifs becomes a pseudogene. Thus, NADase-inactive SPN continues to evolve under functional constraint. Furthermore, NADase activity did not correlate with invasive disease in our collection but was associated with tissue tropism. The ability to cause infection at both the pharynx and the skin ("generalist" strains) is correlated with NADase-active SPN, while the preference for causing infection at either the throat or the skin ("specialist" strains) is associated with NADase-inactive SPN. These findings suggest that SPN has a NADase-independent function and prompt a reevaluation of the role of SPN in streptococcal pathogenesis.
| S-EPMC2897333 | biostudies-literature
Project description:The virulence of Gram-positive bacteria is enhanced by toxins like the Streptococcus pyogenes β-NAD(+) glycohydrolase known as SPN. SPN-producing strains of S. pyogenes additionally express the protein immunity factor for SPN (IFS), which forms an inhibitory complex with SPN. We have determined crystal structures of the SPN-IFS complex and IFS alone, revealing that SPN is structurally related to ADP-ribosyl transferases but lacks the canonical binding site for protein substrates. SPN is instead a highly efficient glycohydrolase with the potential to deplete cellular levels of β-NAD(+). The protective effect of IFS involves an extensive interaction with the SPN active site that blocks access to β-NAD(+). The conformation of IFS changes upon binding to SPN, with repacking of an extended C-terminal α helix into a compact shape. IFS is an attractive target for the development of novel bacteriocidal compounds functioning by blocking the bacterium's self-immunity to the SPN toxin.
| S-EPMC3056158 | biostudies-literature
Project description:UnlabelledVirulence factors are often multifunctional and contribute to pathogenesis through synergistic mechanisms. For the human pathogen Streptococcus pyogenes, two factors that act synergistically are the S. pyogenes NAD(+) glycohydrolase (SPN) and streptolysin O (SLO). Through distinct mechanisms, SLO forms pores in host cell membranes and translocates SPN into the host cell cytosol. Two natural variants of SPN exist, one that exhibits NADase activity and one that lacks this function, and both versions are translocated and act in concert with SLO to cause an accelerated death response in epithelial cells. While NADase(+) SPN is known to trigger a metabolic form of necrosis through the depletion of NAD(+), the mechanism by which NADase(-) SPN induces cell death was unknown. In the studies described here, we examined the pathway of NADase(-) cell death through analysis of activation patterns of mitogen-activated protein kinases (MAPKs). S. pyogenes infection resulted in activation of members of three MAPK subfamilies (p38, ERK, and JNK). However, only JNK was activated in an SLO-specific manner. NADase(-) SPN induced necrosis in HeLa epithelial cells associated with depolarization of mitochondrial membranes, activation of NF-κB, and the generation of reactive oxygen species. Remarkably, RNA interference (RNAi) silencing of JNK protected cells from NADase(-)-SPN-mediated necrosis, suggesting that NADase(-) SPN triggers a form of programmed necrosis dependent on JNK signaling. Taken together, these data demonstrate that SPN acts with SLO to elicit necrosis through two different mechanisms depending on its NADase activity, i.e., metabolic (NADase(+)) or programmed (NADase(-)), leading to distinct inflammatory profiles.ImportanceMany bacterial pathogens produce toxins that alter how infected host cells interact with the immune system. For Streptococcus pyogenes, two toxins, a NAD(+) glycohydrolase (SPN) and streptolysin O (SLO), act in combination to cause infected cells to die. However, there are two natural forms of SPN, and these variants cause dying cells to produce different types of signaling molecules. The NADase(+) form of SPN kills cells by depleting reserves of NAD(+) and cellular energy. The other form of SPN lacks this activity (NADase(-)); thus, the mechanism by which this variant induces toxicity was unknown. Here, we show that infected cells recognize NADase(-) SPN through a specific signaling molecule called JNK, which causes these cells to undergo a form of cellular suicide known as programmed necrosis. This helps us to understand how different forms of toxins alter host cell signaling to help S. pyogenes cause different types of diseases.
| S-EPMC4742715 | biostudies-literature
Project description:Necrotizing soft tissue infections caused by Streptococcus pyogenes (group A streptococcus [GAS]) are characterized by rapid and extensive necrosis of fascia and muscle. Molecular epidemiological studies have demonstrated a positive correlation between GAS isolates that cause invasive infections and the production of S. pyogenes NAD+-glycohydrolase (SPN), an NADase secreted by GAS, but the effect of SPN on muscle cells has not been described. Thus, using standard βNAD+ and ATP quantification assays, we investigated the effects of SPN on cultured human skeletal muscle cell (SkMC) βNAD+ and ATP with and without streptolysin O (SLO)–a secreted cholesterol-dependent cytolysin known to act synergistically with SPN. We found that culture supernatants from GAS strains producing SLO and SPN depleted intracellular βNAD+ and ATP, while exotoxins from a GAS strain producing SLO and an enzymatically-inactive form of SPN had no effect on βNAD+ or ATP. Addition of purified, enzymatically-active SPN to NADase-negative culture supernatants or sterile media reconstituted βNAD+ depletion but had no effect ATP levels. Further, SPN-mediated βNAD+ depletion could be augmented by SLO or the homologous cholesterol-dependent cytolysin, perfringolysin O (PFO). Remarkably, SPN-mediated βNAD+ depletion was SkMC-specific, as purified SPN had minimal effect on epithelial cell βNAD+. Taken together, this study identifies a previously unrecognized role for SPN as a major disruptor of skeletal muscle βNAD+. Such activity could contribute to the rapid and widespread myonecrosis characteristic of severe GAS soft tissue infections.
| S-EPMC9322677 | biostudies-literature
Project description:Bacterial pneumonia is a global health challenge that causes up to 2 million deaths each year. Purinergic signaling plays a pivotal role in healthy alveolar epithelium. Here, we used fluorophore-based analysis and live-cell calcium imaging to address the question of whether the bacterial pathogen Streptococcus pneumoniae directly interferes with purinergic signaling in alveolar epithelial cells. Disturbed purinergic signaling might result in pathophysiologic changes like edema formation and atelectasis, which are commonly seen in bacterial pneumonia. Purine receptors are mainly activated by ATP, mediating a cytosolic calcium response. We found that this purinergic receptor P2Y2-mediated response is suppressed in the presence of S. pneumoniae in A549 and isolated primary alveolar cells in a temperature-dependent manner. Downstream inositol 3-phosphate (IP3) signaling appeared to be unaffected, as calcium signaling via protease-activated receptor 2 remained unaltered. S. pneumoniae-induced suppression of the P2Y2-mediated calcium response depended on the P2Y2 phosphorylation sites Ser-243, Thr-344, and Ser-356, which are involved in receptor desensitization and internalization. Spinning-disk live-cell imaging revealed that S. pneumoniae induces P2Y2 translocation into the cytosol. In conclusion, our results show that S. pneumoniae directly inhibits purinergic signaling by inducing P2Y2 phosphorylation and internalization, resulting in the suppression of the calcium response of alveolar epithelial cells to ATP, thereby affecting cellular integrity and function.
| S-EPMC6709641 | biostudies-literature