Assembly of<i>Staphylococcus aureus</i>Leukocidin into a Pore-Forming Ring-Shaped Oligomer on Human Polymorphonuclear Leukocytes and Rabbit Erythrocytes

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Staphylococcal γ-hemolysin is a bicomponent pore-forming toxin composed of LukF and Hlg2. These proteins are expressed as watersoluble monomers and then assemble into the oligomeric pore form on the target cell. Here, we report the crystal structure of the octameric pore form of γ-hemolysin at 2.5 Å resolution, which is the first high-resolution structure of a β-barrel transmembrane protein composed of two proteins reported to date. The octameric assembly consists of four molecules of LukF and Hlg2 located alternately in a circular pattern, which explains the biochemical data accumulated over the past two decades. The structure, in combination with the monomeric forms, demonstrates the elaborate molecular machinery involved in pore formation by two different molecules, in which interprotomer electrostatic interactions using loops connecting β2 and β3 (loop A: Asp43-Lys48 of LukF and Lys37-Lys43 of Hlg2) play pivotal roles as the structural determinants for assembly through unwinding of the N-terminal β-strands (aminolatch) of the adjacent protomer, releasing the transmembrane stem domain folded into a β-sheet in the monomer (prestem), and interaction with the adjacent protomer.

Section: Discussionsupporting

confidence: 92%

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confidence: 99%

Crystal structure of the octameric pore of staphylococcal γ-hemolysin reveals the β-barrel pore formation mechanism by two components

Yamashita

Kawai

Tanaka

et al. 2011

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154

210

“…LukAB specifically targets phagocytes such as polymorphonuclear cells (PMNs or neutrophils) (9)(10)(11)(12), which are an integral part of the host innate immune response to S. aureus (13). The capacity to kill PMNs is conserved among all leukocidins (4,5), although the actions of LukED (14) and Hlg (15) are not limited to phagocytes (5). Despite their common cellular target, the leukocidins diverge in their potency toward PMNs of different species.…”

mentioning

confidence: 99%

Staphylococcus aureusLukAB cytotoxin kills human neutrophils by targeting the CD11b subunit of the integrin Mac-1

DuMont

Yoong

Day

et al. 2013

193

279

Staphylococcus aureus causes diseases ranging from superficial wound infections to more invasive manifestations like osteomyelitis and endocarditis. The evasion of host phagocytes recruited to the site of infection is essential to the success of S. aureus as a pathogen. A single S. aureus strain can produce up to five different bicomponent pore-forming leukotoxins that lyse immune cells by forming pores in the cellular plasma membrane. Although these leukotoxins have been considered redundant due to their cytotoxic activity toward human neutrophils, each toxin displays varied species and celltype specificities. This suggests that cellular factors may influence which cells each toxin targets. Here we describe the identification of CD11b, the α subunit of the αM/β2 integrin (CD11b/CD18), macrophage-1 antigen, or complement receptor 3, as a cellular receptor for leukocidin A/B (LukAB), an important toxin that contributes to S. aureus killing of human neutrophils. We demonstrate that CD11b renders human neutrophils susceptible to LukAB-mediated killing by purified LukAB as well as during S. aureus infection ex vivo. LukAB directly interacts with human CD11b by binding to the I domain, a property that determines the species specificity exhibited by this toxin. Identification of a LukAB cellular target has broad implications for the use of animal models to study the role of LukAB in S. aureus pathogenesis, explains the toxin's tropism toward human neutrophils and other phagocytes, and provides a cellular therapeutic target to block the effect of LukAB toward human neutrophils.toxin receptor | pore-forming cytotoxin

“…One of the toxins, Panton-Valentine leukocidin (PVL) is associated with human pyogenic necrotizing skin infections such as furuncles, cellulitis, and abscesses, and more severe septic infections such as osteomyelitis, bacteremia, purpura fulminans, and necrotizing pneumonia (1)(2)(3)(4)(5)(6)(7)(8). PVL with γ-hemolysins (HlgA/HlgB and HlgC/ HlgB) and LukE/LukD belongs to the bicomponent pore-forming leukotoxin family (9)(10)(11)(12)(13)(14), which are thought to contribute to virulence in various infection models (15)(16)(17)(18), although some groups disagree (19,20). A class S and class F component interact sequentially and synergistically, inducing the activation and permeabilization of target cells and leading to their lysis.…”

mentioning

confidence: 99%

Heavy chain-only antibodies and tetravalent bispecific antibody neutralizing Staphylococcus aureus leukotoxins

Laventie

Rademaker

Saleh

et al. 2011

Panton-Valentine leukocidin (PVL) is a pore-forming toxin associated with current outbreaks of community-associated methicillin-resistant strains and implicated directly in the pathophysiology of Staphylococcus aureus-related diseases. Humanized heavy chain-only antibodies (HCAb) were generated against S. aureus PVL from immunized transgenic mice to neutralize toxin activity. The active form of PVL consists of the two components, LukS-PV and LukF-PV, which induce osmotic lysis following pore formation in host defense cells. One anti-LukS-PV HCAb, three anti-LukF-PV HCAbs with affinities in the nanomolar range, and one engineered tetravalent bispecific HCAb were tested in vitro and in vivo, and all prevented toxin binding and pore formation. Anti-LukS-PV HCAb also binds to γ-hemolysin C (HlgC) and inhibits HlgC/HlgB pore formation. Experiments in vivo in a toxin-induced rabbit endophthalmitis model showed that these HCAbs inhibit inflammatory reactions and tissue destruction, with the tetravalent bispecific HCAb performing best. Our findings show the therapeutic potential of HCAbs, and in particular, bispecific antibodies.