Nuclease-sensitive binding of an Actinobacillus actinomycetemcomitans leukotoxin to the bacterial cell surface

Ohta, Hiroyuki; Kato, Kimiko; Kokeguchi, Susumu; Hara, Hiroaki; Fukui, Kiichi; Murayama, Yoji

doi:10.1128/iai.59.12.4599-4605.1991

Cited by 49 publications

(53 citation statements)

References 25 publications

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“…Considering the present results and those previously reported (21)(22)(23)(24), the following possibilities are suggested for the association of leukotoxin to A. actinomycetemcomitans. Leukotoxin is bound to bacterial and vesicle surfaces by weak interactions mediated by electrostatic forces or by hydrophobic protein epitopes, this amount of toxin being removed with 0.3 m NaCl, serum ( £ 20%), or low (< 1 m) urea concentrations.…”

Section: Discussionsupporting

confidence: 75%

“…In addition to its membrane-destabilizing action, NaCl also displaces electrostatic interactions that could mediate binding of leukotoxin to charged molecules, such as LPS and nucleic acids. The latter association mechanism was suggested by Ohta et al (21,22) who showed release of the toxin from the bacteria upon treatment with nucleases. However, the portion of leukotoxin released by this treatment is less than that removed by NaCl (data not shown).…”

Section: Discussionmentioning

confidence: 83%

“…The process may enable the diffusion of the toxin from the bacterial biofilm into the surrounding tissues, where it can exert its biological effect. membrane bound nucleic acids (21,22). The binding probably depends on electrostatic forces between the positively charged leukotoxin (pI 8.8) and the nucleic acids.…”

mentioning

confidence: 99%

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Serum‐mediated release of leukotoxin from the cell surface of the periodontal pathogen Actinobacillus actinomycetemcomitans

Johansson

Claesson

Hänström

et al. 2003

European J Oral Sciences

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The leukotoxin of the periodontopathogen Actinobacillus actinomycetemcomitans is an important virulence factor that lyses human neutrophils and monocytes and thus, it may enable the bacterium to evade the local host defense. The toxin also induces degranulation of neutrophils and cytokine release in monocytes. To trigger these biological activities, leukotoxin has to be released from the bacterium and diffuse into the periodontal tissues. To date, the conditions found to cause toxin release have been artificial and have included high ion concentration and alkaline conditions. To study the release of the toxin under conditions mimicking the natural environment of the periodontium the ability of human serum to enable leukotoxin release from the bacterial surface was examined. Suspensions of leukotoxic A. actinomycetemcomitans strains were incubated with various concentrations of human serum or serum albumin. The suspensions were centrifuged and the leukotoxin in the supernatants or the cell pellets was detected by gel electrophoresis and immunoblotting. Serum was found to cause the rapid release of leukotoxin from the bacteria in a concentration-dependent manner. Pure albumin exhibited a similar effect. The leukotoxin released was active against human neutrophils. Only a minor proportion of it was associated with membranous vesicles produced by the bacteria. The results indicate that serum, a fluid closely related to the exudate in inflamed periodontal pockets, releases leukotoxin from the cell surface of A. actinomycetemcomitans. The process may enable the diffusion of the toxin from the bacterial biofilm into the surrounding tissues, where it can exert its biological effect.

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Section: Discussionsupporting

confidence: 75%

Section: Discussionmentioning

confidence: 83%

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Serum‐mediated release of leukotoxin from the cell surface of the periodontal pathogen Actinobacillus actinomycetemcomitans

Johansson

Claesson

Hänström

et al. 2003

European J Oral Sciences

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“…Thus, any toxic eect against PMNL requires contact of the bacteria with the cell membrane of PMNL. Though certain conditions such as presence of nucleases and increased ionic strength of the surrounding medium cause leukotoxin release from the bacteria (21,34), it is possible that in vivo the bacteria keep the leukotoxin bound to the cell surface. Carriage of leukotoxin on its surface could thus confer a particular advantage to A. actinomycetemcomitans upon challenge with PMNL.…”

Section: Discussionmentioning

confidence: 99%

Anaerobic neutrophil‐dependent killing of Actinobacillus actinomycetemcomitans in relation to the bacterial leukotoxicity

Johansson¹,

Sandström²,

Claesson³

et al. 2000

European J Oral Sciences

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The effect of leukotoxin on the interaction of Actinobacillus actinomycetemcomitans with human polymorphonuclear leukocytes (PMNL) was studied under anaerobic conditions with strains able to produce high or low amounts of leukotoxin. PMNL morphology, phagocytosis and killing were examined by transmission electron microscopy and bioassays, respectively. At ratios of > or =25 bacteria/PMNL, a highly toxic A. actinomycetemcomitans strain completely destroyed the PMNL within 7 min, resulting in bacterial survival. Lowering the bacteria/PMNL-ratio enabled phagocytosis and killing of this highly toxic strain. A. actinomycetemcomitans strains with low leukotoxicity were effectively killed by PMNL under any condition. Presence of specific antibodies against A. actinomycetemcomitans or of anti-leukotoxin serum protected PMNL from being injured and allowed phagocytosis to occur. Pre-incubation of the leukotoxic strain with Porphyromonas gingivalis, a bacterium that destroys leukotoxin, abolished lysis of PMNL and inhibited phagocytosis of A. actinomycetemcomitans. The results show that leukotoxin may protect A. actinomycetemcomitans against phagocytosis by human PMNL. The protection occurs at a population level and in relation to the bacterial load. The size of the bacterial population required to counteract phagocytosis is dependent on the leukotoxin production of the strain.

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“…When the anaerobic fructose-limited chemostat culture was in a steady state, the amount of cell surface DNA was estimated to be about 20% of the total cellular DNA (26). The mechanism for the extracellular localization of DNA is unknown, but bacterial autolysis does not seem to be involved in the process (28).…”

mentioning

confidence: 99%

Cell Surface‐Associated Enolase in Actinobacillus actinomycetemcomitans

Hara

Ohta

Inoue

et al. 2000

Microbiology and Immunology

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Cell surface-associated materials of Actinobacillus actinomycetemcomitans were extracted by a short incubation of the cell suspension in a Tris-buffered saline in the presence and absence of a restriction enzyme, EcoRI. The supernatants (which we termed EcoRI extract and surface extract, respectively) contained a number of extracellularly released proteins. Of these proteins, four major proteins were identified by N-terminal sequencing to be the 34 and 39 kDa outer membrane proteins, the GroEL-like protein, and a 47 kDa protein homologous to Haemophilus influenzae enolase. Enolase activity was found in the extracts and its relative amount of activity in the EcoRI extract from a culture of the mid-exponential growth phase was estimated as 5.7 % of total enzyme activity. In contrast, the relative amount of activity of another cytosolic enzyme, lactate dehydrogenase, was extremely low in the extracts and also in the culture supernatant. These results suggest the external localization of enolase in this bacterium.

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Nuclease-sensitive binding of an Actinobacillus actinomycetemcomitans leukotoxin to the bacterial cell surface

Cited by 49 publications

References 25 publications

Serum‐mediated release of leukotoxin from the cell surface of the periodontal pathogen Actinobacillus actinomycetemcomitans

Serum‐mediated release of leukotoxin from the cell surface of the periodontal pathogen Actinobacillus actinomycetemcomitans

Anaerobic neutrophil‐dependent killing of Actinobacillus actinomycetemcomitans in relation to the bacterial leukotoxicity

Cell Surface‐Associated Enolase in Actinobacillus actinomycetemcomitans

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