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Atomic Force Microscopy of Biomembranes
Published in Qiu-Xing Jiang, New Techniques for Studying Biomembranes, 2020
Yi Ruan, Lorena Redondo-Morata, Simon Scheuring
Given the advantage of high spatial and temporal resolution of HS-AFM, the mechanism of Listeriolysin-O (LLO) action on SLBs have been studies in real time. LLO is a soluble protein of 56 kDa in mass and belongs to a family of cholesterol-dependent cytolysin (CDCs) proteins. It plays a crucial role during infection by Listeria monocytogenes. Ruan et al.50 discovered that LLO-SLB interaction is pH-dependent. LLO is able to form arc pores and can damage lipid membranes as a lineactant. Lineactants are molecules that tend to accumulate in 1D in the phase boundaries, that is, adsorbing at the contact line which separate two 2D phases. This process leads to large-scale membrane defects that can help bacteria to escape from phagocytic vacuoles. The dynamic imaging of HS-AFM revealed a detailed understanding of the molecular action of LLO as depicted in Figure 5.8.
Bacillus
Published in Dongyou Liu, Laboratory Models for Foodborne Infections, 2017
Jessica Minnaard, Ivanna S. Rolny, Pablo F. Pérez
Members of the B. cereus group are able to produce other pore-forming toxins such as cereolysin O, hemolysin III, and three phospholipases C.95,100–102 Cereolysin O (or Hemolysin I), a heat-labile protein toxin, is a member of the cholesterol-dependent cytolysin family; its best known members are listeriolysin O and perfringolysin O. They are able to form large pores in the cell membrane.103 Concerning hemolysin III, it was first reported by Baida and Kuzmin in 1995.100 This is a heat-labile factor that is not inhibited by cholesterol, but no further reports were found. Sphingomyelinase, phosphatidylcholine–phospholipase C, and phosphatidylinositol–phospholipase C (PI-PLC) have cytolytic activity.42,46,104–107 Interestingly, PI-PLC from B. anthracis inhibits the activation of murine dendritic cells.108
Physiological and pathophysiological roles of hepoxilins and their analogs
Published in Drug Metabolism Reviews, 2023
Sara A. Helal, Fadumo Ahmed Isse, Samar H. Gerges, Ayman O. S. El-Kadi
In many cases, the ability to control the polymorphonuclear neutrophils (PMNs) infiltration during the lung infection could attenuate the inflammatory damage and improve lung function (Grudzinska and Sapey 2018). Albeit the recruitment of neutrophils into the lung tissue during bacterial infection is necessary to stimulate the host defense, the unregulated release of neutrophils can damage the host tissues due to the liberation of some oxidants, proteinases, and cationic peptides into the extracellular space (Grommes and Soehnlein 2011) The regulation of this neutrophilic activity could be a possible therapeutic approach in some diseases. The potential role of HxA3 in neutrophil transepithelial migration was investigated in a model of lung epithelial barriers infected with Pseudomonas aeruginosa (Tamang et al. 2012) or Streptococcus pneumoniae (Table 2) (Bhowmick et al. 2011; Bhowmick et al. 2013; Zukauskas et al. 2018) HxA3 was formed when the lung is infected with pathogenic bacteria and when produced it causes the neutrophils to move across the epithelial barriers. One important factor in stimulating HxA3–dependent neutrophil recruitment across the pulmonary epithelium is the production of pneumolysin (PLY). PLY is a member of the cholesterol-dependent cytolysin family and a major S. pneumoniae virulence factor that provokes pore formation in eukaryotic membranes and promotes acute inflammation, bacteremia, and tissue damage (Adams et al. 2020). It was found that neutrophil transepithelial migration was interfered with by the inhibition of PLA2 and/or 12-LOX, which are essential enzymes for HxA3 formation (Hurley et al. 2004). Thus, new compounds with inhibitory structural analogs of HxA3 may have the ability to impede neutrophil transepithelial migration induced by bacterial infection of the lung.
Dual functions of discoidinolysin, a cholesterol-dependent cytolysin with N-terminal discoidin domain produced from Streptococcus mitis strain Nm-76
Published in Journal of Oral Microbiology, 2022
Atsushi Tabata, Airi Matsumoto, Ai Fujimoto, Kazuto Ohkura, Takuya Ikeda, Hiroki Oda, Shuto Yokohata, Miho Kobayashi, Toshifumi Tomoyasu, Ayuko Takao, Hisashi Ohkuni, Hideaki Nagamune
Cholesterol-dependent cytolysin (CDC) is a pore-forming toxin secreted from both human-pathogenic and human-opportunistic Gram-positive bacteria. A CDC termed intermedilysin (ILY) was discovered in the human-opportunistic species Streptococcus intermedius belonging to the Anginosus group streptococci [35]. ILY is important for the pathogenicity of S. intermedius in humans [36]. In addition, investigations on the pathogenicity of other opportunistic streptococci that inhabit the oral cavity of humans revealed that a group of S. mitis strains displayed obvious β-hemolysis on blood agar [37]. The first reported β-hemolytic factor produced by S. mitis, mitilysin (MLY), is a typical CDC composed of four domains with extensive homology to pneumolysin (PLY) [38]. Subsequently, S. mitis-derived human platelet aggregation factor (Sm-hPAF), originally identified as a platelet aggregation factor [39], was shown to function as a hemolysin [40]. Sm-hPAF is a CDC with a remarkable structural characteristic of an additional N-terminal domain attached to the four-domain structure of typical CDCs. The name lectinolysin (LLY) was proposed for this CDC based on the results of the functional analysis of the N-terminal additional domain of the Sm-hPAF homolog from S. mitis strain SK597 [41]. Genes encoding PLY-like proteins, including the F5_F8_type_C domain, also known as the discoidin domain or C2-like domain – a major domain of many blood coagulation factors [42] – were also found in the genome of S. pseudopneumoniae IS7493 [SPPN_02090 (present locus tag is SPPN_RS02030) and SPPN_04220] [29]. In addition, different subfamilies of SPPN_02090 orthologous genes, designated llyA2, were found in S. mitis strains [29]. However, the expression of the llyA2 transcription product and its molecular functions have not yet been investigated.
Calcium Signaling Commands Phagosome Maturation Process
Published in International Reviews of Immunology, 2019
Gourango Pradhan, Philip Raj Abraham, Rohini Shrivastava, Sangita Mukhopadhyay
Listeria monocytogenes, Burkholderia pseudomallei, Francisella tularensis, Shigella flexneri, and members of Rickettsia family are known to escape from phagosomes and complete their life cycle in the cytosol [97,98]. Most of them have shown to infect macrophages, though macrophages are not the primary cells for Rickettsia sp. and S. flexneri [99]. L. monocytogenes exploits the host actin polymerization machinery to move within the cytosol and spreads from cell to cell [98]. In L. monocytogenes, the virulence factors involved in phagosomal escape and cell to cell spread are well characterized. Listeria sp. secretes two PLC (phosopholipase C), PlcA and PlcB [100] as well as cholesterol dependent cytolysin LLO (Listeriolysin O) [101]. When pH of the internalized vacuole acidifies, LLO form pores in the vacuolar membrane to destabilize it, thus Listeria sp. escapes from phagocytic vacuoles to cytosol [102–104]. LLO causes a massive increase in cytosolic calcium due to an influx of extracellular Ca2+via pores in plasma membrane [105] and also releases stored calcium from ER into cytosol upon infection due to activation of PLC by InlB (Internalin B) and LLO [106] (Figure 2a). Perhaps the acidic environment caused by these factors facilitates the formation of initial pore that permeabilize the membrane and allows Listeria sp. to escape from phagosome to cytosol. Ca2+ signaling also induces recruitment and assembly of NOX and recruitment of vacuolar ATPases during phagosomal maturation to rapidly reduce the pH of phagosome lumen and helps in survival of L. monocytogenes by allowing them to escape from phagosomes [107,108]. Enhanced ROS production in phagosome lumen again hints at positive regulation of P–L fusion (Figure 2a). Since P–L fusion has not been blocked, Listeria sp. has adopted strategies to escape from phagosome to cytosol by enhancing the acidic behavior of phagosomes at early stage that helps in rupturing the phagosomal membrane so it can easily come out of phagosomes before it fuses with lysosomes.