Cytolysin-dependent evasion of lysosomal killing

Abstract

Local host defenses limit proliferation and systemic spread of pathogenic bacteria from sites of mucosal colonization. For pathogens such as streptococci that fail to grow intracellularly, internalization and killing by epithelial cells contribute to the control of bacterial growth and dissemination. Here, we show that group A Streptococcus (GAS), the agent of streptococcal sore throat and invasive soft tissue infections, evades internalization and intracellular killing by pharyngeal epithelial cells. Production of the cholesterol-binding cytotoxin streptolysin O (SLO) prevented internalization of GAS into lysosomes. In striking contrast, GAS rendered defective in production of SLO were internalized directly or rapidly transported into lysosomes, where they were killed by a pH-dependent mechanism. Because SLO is the prototype of cholesterol-dependent cytolysins produced by many Grampositive bacteria, cytolysin-mediated evasion of lysosomal killing may be a general mechanism to protect such pathogens from clearance by host epithelial cells.Streptococcus pyogenes ͉ streptolysin O ͉ virulence E pithelial cells of mucosal surfaces constitute an early line of defense against infecting microorganisms. These cells protect the host not only by acting as a physical barrier but also by secreting antimicrobial molecules and by recruiting professional immune cells to the site of infection (1-5). Also, epithelial cells have the capacity to internalize and kill bacteria. Extracellular pathogens such as streptococci, Staphylococcus aureus, and Pseudomonas aeruginosa can be internalized by epithelial cells but do not appear to multiply in the intracellular environment (6-11). Rather, internalized bacteria are killed over time. Therefore, to persist at the mucosal surface, extracellular bacterial pathogens must evade internalization and killing by epithelial cells.In this study, we investigated the effects of streptolysin O (SLO) on the interactions of group A Streptococcus (GAS), the agent of streptococcal sore throat and severe, invasive, or ''flesh-eating'' infections, with human oropharyngeal epithelial cells. SLO is the prototype of a family of cholesterol-binding cytotoxins produced by many pathogenic Gram-positive bacteria including Streptococcus pneumoniae (pneumolysin), Listeria monocytogenes (listeriolysin O), Clostridium perfringens (perfringolysin O), and Bacillus anthracis (anthrolysin) (12-14). The cholesterol-binding cytotoxins share the property of poreforming activity for a broad range of cholesterol-containing cell membranes (12, 15). However, it remains unknown whether they serve a common functional role in pathogen-host biology for the diverse species that produce them. Here, we report that SLO is a critical modulator of GAS internalization, intracellular trafficking, and bacterial killing by human oropharyngeal keratinocytes. We found that SLO prevented direct uptake of GAS into lysosomes and efficient pH-dependent intracellular killing. On the basis of these findings, we propose that SLO enhances GAS surviv...

A Role for Synaptotagmin VII-Regulated Exocytosis of Lysosomes in Neurite Outgrowth from Primary Sympathetic Neurons

“…Thus, these results demonstrate that in primary sympathetic neurons, VAMP7-containing compartments completely overlap with Lamp1-positive late endosomes/lysosomes, as shown previously in other cell types (Advani et al, 1999;Rao et al, 2004). , keratinocytes (Hakansson et al, 2005), and the neuroendocrine cell line PC12 (Fukuda et al, 2004;Wang et al, 2005). To determine whether the same occurred in primary neurons, we performed immunolocalization of Syt VII in isolated SCG neurons.…”

Group A Streptococcus Activates Type I Interferon Production and MyD88-dependent Signaling without Involvement of TLR2, TLR4, and TLR9

“…Although GAS is a prototype extracellular pathogen, it can be efficiently internalized by many phagocytic and nonphagocytic cells. However, GAS survives only for a short period of time in host cells due to degradation in lysosomal and autophagosomal compartments (5,6). Interestingly, Bacillus subtilis engineered to express streptococcal SLO was not able to survive or multiply in infected cells, as opposed to listeriolysin O-expressing B. subtilis (74).…”

StreptococcusAdherence and Colonization

“…SLO is a human-specific cytolysin (Table 2) with a range of properties, including the ability to form pores through which effector proteins, e.g., NAD ϩ glycohydrolase (SN), may be injected into the host cell cytoplasm (184). An important property of SLO in colonization is that it prevents the internalization of GAS by lysosomes, thus enhancing the intracellular survival of GAS within epithelial cells (208). This is believed to be a feature involved in the long-term carriage of not only GAS but also commensal oral streptococci (514), which may potentially survive for long periods within epithelial cells, partially protected from immune defenses and from antibiotics.…”