ADAM10 Cell Surface Expression but Not Activity Is Critical for Staphylococcus aureus α-Hemolysin-Mediated Activation of the NLRP3 Inflammasome in Human Monocytes

Ezekwe, Ejiofor A.D.; Weng, Chengyu; Duncan, Joseph A.

doi:10.3390/toxins8040095

Cited by 31 publications

(28 citation statements)

References 30 publications

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“…Notably, ADAM10 and ADAM17 contain a conserved active site sequence and, according to the primary structure of their catalytic sites, they belong to the same subgroup of ADAM proteinases [37,38]. That GI254023X inhibits binding of α-toxin, although mutation of the catalytic site of ADAM10 does not, might be due to non-canonical effects of the inhibitor [68], possibly involving factors that regulate ADAM10 expression, folding, traffic or surface presentation, as has been shown for Atg16L1 [69], eukaryotic initiation factor 2α (eIF2α)…”

Section: Discussionmentioning

confidence: 95%

Dissecting the role of ADAM10 as a mediator of Staphylococcus aureus α-toxin action

Hoven

Rivas

Neukirch

et al. 2016

Biochemical Journal

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Staphylococcus aureus is a leading cause of bacterial infections in humans, including life-threatening diseases such as pneumonia and sepsis. Its small membrane-pore-forming α-toxin is considered an important virulence factor. By destroying cell-cell contacts through cleavage of cadherins, the metalloproteinase ADAM10 (a disintegrin and metalloproteinase 10) critically contributes to α-toxin-dependent pathology of experimental S. aureus infections in mice. Moreover, ADAM10 was proposed to be a receptor for α-toxin. However, it is unclear whether the catalytic activity or specific domains of ADAM10 are involved in mediating binding and/or subsequent cytotoxicity of α-toxin. Also, it is not known how α-toxin triggers ADAM10's enzymatic activity, and whether ADAM10 is invariably required for all α-toxin action on cells. In the present study, we show that efficient cleavage of the ADAM10 substrate epithelial cadherin (E-cadherin) requires supra-cytotoxic concentrations of α-toxin, leading to significant increases in intracellular [Ca(2+)]; the fall in cellular ATP levels, typically following membrane perforation, became observable at far lower concentrations. Surprisingly, ADAM10 was dispensable for α-toxin-dependent xenophagic targeting of S. aureus, whereas a role for α-toxin attack on the plasma membrane was confirmed. The catalytic site of ADAM10, furin cleavage site, cysteine switch and intracellular domain of ADAM10 were not required for α-toxin binding and subsequent cytotoxicity. In contrast, an essential role for the disintegrin domain and the prodomain emerged. Thus, co-expression of the prodomain with prodomain-deficient ADAM10 reconstituted binding of α-toxin and susceptibility of ADAM10-deficient cells. The results of the present study may help to inform structural analyses of α-toxin-ADAM10 interactions and to design novel strategies to counteract S. aureus α-toxin action.

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Section: Discussionmentioning

confidence: 95%

Dissecting the role of ADAM10 as a mediator of Staphylococcus aureus α-toxin action

Hoven

Rivas

Neukirch

et al. 2016

Biochemical Journal

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“…Binding of α-toxin to ADAM10 is necessary for α-toxin-induced cytotoxicity and the disruption of epithelial and endothelial barriers [8-11]. However, the molecular details of this process are unknown, in particular since a recent study demonstrated that the enzyme activity of ADAM10 is not required for at least some of the effects of α-toxin [12]. …”

Section: Introductionmentioning

confidence: 99%

Staphylococcus aureus α-Toxin Induces Inflammatory Cytokines via Lysosomal Acid Sphingomyelinase and Ceramides

Gulbins

Edwards

et al. 2017

Cell Physiol Biochem

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Background/Aims: Staphylococcus aureus (S. aureus) infections are a major clinical problem and range from mild skin and soft-tissue infections to severe and even lethal infections such as pneumonia, endocarditis, sepsis, osteomyelitis, and toxic shock syndrome. Toxins that are released from S. aureus mediate many of these effects. Here, we aimed to identify molecular mechanisms how α-toxin, a major S. aureus toxin, induces inflammation. Methods: Macrophages were isolated from the bone marrow of wildtype and acid sphingomyelinase-deficient mice, stimulated with S. aureus α-toxin and activation of the acid sphingomyelinase was quantified. The subcellular formation of ceramides was determined by confocal microscopy. Release of cathepsins from lysosomes, activation of inflammasome proteins and formation of Interleukin-1β (IL-1β) and Tumor Necrosis Factor-α (TNF-α) were analyzed by western blotting, confocal microscopy and ELISA. Results: We demonstrate that S. aureus α-toxin activates the acid sphingomyelinase in ex vivo macrophages and triggers a release of ceramides. Ceramides induced by S. aureus α-toxin localize to lysosomes and mediate a release of cathepsin B and D from lysosomes into the cytoplasm. Cytosolic cathepsin B forms a complex with Nlrc4. Treatment of macrophages with α-toxin induces the formation of IL-1β and TNF-α. These events are reduced or abrogated, respectively, in cells lacking the acid sphingomyelinase and upon treatment of macrophages with amitriptyline, a functional inhibitor of acid sphingomyelinase. Pharmacological inhibition of cathepsin B prevented activation of the inflammasome measured as release of IL-1β, while the formation of TNF-α was independent of cathepsin B. Conclusion: We demonstrate a novel mechanism how bacterial toxins activate the inflammasome and mediate the formation and release of cytokines: S. aureus α-toxin triggers an activation of the acid sphingomyelinase and a release of ceramides resulting in the release of lysosomal cathepsin B and formation of pro-inflammatory cytokines.

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“…The localization and decreased numbers of neutrophils likely resulted in less inflammation to facilitate more rapid wound healing. Although the mechanism by which neutralizing AT led to less neutrophil recruitment is not entirely clear, it could have been due to decreasing AT activation of the NLRP3/ASC inflammasome that processes pro-interleukin-1␤ (pro-IL-1␤) to active IL-1␤ (38)(39)(40)(41)(42), which is essential for mediating neutrophil recruitment to a site of S. aureus infection in the skin (41).…”

Section: Discussionmentioning

confidence: 99%

Neutralizing Alpha-Toxin Accelerates Healing of Staphylococcus aureus-Infected Wounds in Nondiabetic and Diabetic Mice

Ortines

Liu

Cheng³

et al. 2018

Antimicrob Agents Chemother

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wound infections delay healing and result in invasive complications such as osteomyelitis, especially in the setting of diabetic foot ulcers. In preclinical animal models of skin infection, antibody neutralization of alpha-toxin (AT), an-secreted pore-forming cytolytic toxin, reduces disease severity by inhibiting skin necrosis and restoring effective host immune responses. However, whether therapeutic neutralization of alpha-toxin is effective against -infected wounds is unclear. Herein, the efficacy of prophylactic treatment with a human neutralizing anti-AT monoclonal antibody (MAb) was evaluated in an skin wound infection model in nondiabetic and diabetic mice. In both nondiabetic and diabetic mice, anti-AT MAb treatment decreased wound size and bacterial burden and enhanced reepithelialization and wound resolution compared to control MAb treatment. Anti-AT MAb had distinctive effects on the host immune response, including decreased neutrophil and increased monocyte and macrophage infiltrates in nondiabetic mice and decreased neutrophil extracellular traps (NETs) in diabetic mice. Similar therapeutic efficacy was achieved with an active vaccine targeting AT. Taken together, neutralization of AT had a therapeutic effect against -infected wounds in both nondiabetic and diabetic mice that was associated with differential effects on the host immune response.

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ADAM10 Cell Surface Expression but Not Activity Is Critical for Staphylococcus aureus α-Hemolysin-Mediated Activation of the NLRP3 Inflammasome in Human Monocytes

Cited by 31 publications

References 30 publications

Dissecting the role of ADAM10 as a mediator of Staphylococcus aureus α-toxin action

Dissecting the role of ADAM10 as a mediator of Staphylococcus aureus α-toxin action

Staphylococcus aureus α-Toxin Induces Inflammatory Cytokines via Lysosomal Acid Sphingomyelinase and Ceramides

Neutralizing Alpha-Toxin Accelerates Healing of Staphylococcus aureus-Infected Wounds in Nondiabetic and Diabetic Mice

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