The Lytic Transglycosylases of<i>Neisseria gonorrhoeae</i>

Chan, Yolande A.; Hackett, Kathleen T.; Dillard, Joseph P.

doi:10.1089/mdr.2012.0001

Cited by 47 publications

(50 citation statements)

References 62 publications

(110 reference statements)

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“…It is also unknown whether PG-degrading enzymes work together in a complex to remodel the PG layer and whether such complexes colocalize or interact with AmpG to ensure efficient recycling. Lytic transglycosylases are PG-degrading enzymes that cleave the glycan backbone to generate PG monomers (20). N. gonorrhoeae has two lytic transglycosylases, LtgA and LtgD, that generate all or nearly all the PG monomers released by the bacterium.…”

Section: Discussionmentioning

confidence: 99%

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Neisseria gonorrhoeae Crippled Its Peptidoglycan Fragment Permease To Facilitate Toxic Peptidoglycan Monomer Release

Chan

Dillard

2016

J Bacteriol

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Neisseria gonorrhoeae (gonococci) and Neisseria meningitidis (meningococci) are human pathogens that cause gonorrhea and meningococcal meningitis, respectively. Both N. gonorrhoeae and N. meningitidis release a number of small peptidoglycan (PG) fragments, including proinflammatory PG monomers, although N. meningitidis releases fewer PG monomers. The PG fragments released by N. gonorrhoeae and N. meningitidis are generated in the periplasm during cell wall remodeling, and a majority of these fragments are transported into the cytoplasm by an inner membrane permease, AmpG; however, a portion of the PG fragments are released into the extracellular environment through unknown mechanisms. We previously reported that the expression of meningococcal ampG in N. gonorrhoeae reduced PG monomer release by gonococci. This finding suggested that the efficiency of AmpG-mediated PG fragment recycling regulates the amount of PG fragments released into the extracellular milieu. We determined that three AmpG residues near the C-terminal end of the protein modulate AmpG's efficiency. We also investigated the association between PG fragment recycling and release in two species of human-associated nonpathogenic Neisseria: N. sicca and N. mucosa. Both N. sicca and N. mucosa release lower levels of PG fragments and are more efficient at recycling PG fragments than N. gonorrhoeae. Our results suggest that N. gonorrhoeae has evolved to increase the amounts of toxic PG fragments released by reducing its PG recycling efficiency. IMPORTANCENeisseria gonorrhoeae and Neisseria meningitidis are human pathogens that cause highly inflammatory diseases, although N. meningitidis is also frequently found as a normal member of the nasopharyngeal microbiota. Nonpathogenic Neisseria, such as N. sicca and N. mucosa, also colonize the nasopharynx without causing disease. Although all four species release peptidoglycan fragments, N. gonorrhoeae is the least efficient at recycling and releases the largest amount of proinflammatory peptidoglycan monomers, partly due to differences in the recycling permease AmpG. Studying the interplay between bacterial physiology (peptidoglycan metabolism) and pathogenesis (release of toxic monomers) leads to an increased understanding of how different bacterial species maintain asymptomatic colonization or cause disease and may contribute to efforts to mitigate disease. T en species in the genus Neisseria are associated with humans. Neisseria gonorrhoeae (gonococci [GC]) and Neisseria meningitidis (meningococci [MC]) are considered human-restricted pathogens, whereas N. cinerea, N. elongata, N. flavescens, N. lactamica, N. mucosa, N. polysaccharea, N. sicca, and N. subflava are considered nonpathogenic. The nonpathogenic species colonize the nasopharynges and oral cavities of healthy people (1-3). In rare cases, these species disseminate to cause endocarditis or septic infection in immunocompromised individuals or trauma patients (4). N. gonorrhoeae and N. meningitidis share many infection-related factors with ...

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Section: Discussionmentioning

confidence: 99%

“…The PG monomers are generated by lytic transglycosylases, which in Neisseria species, are predicted outer membrane lipoproteins (19,20). As the bacteria grow and divide, they must degrade PG strands to make space for the incorporation of additional PG strands and remodel the cell wall to build and then split the septum for cell division and separation.…”

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confidence: 99%

Neisseria gonorrhoeae Crippled Its Peptidoglycan Fragment Permease To Facilitate Toxic Peptidoglycan Monomer Release

Chan

Dillard

2016

J Bacteriol

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“…Many of the cytoplasmic proteins co-purify as components of large protein complexes that are localized to the membrane, whereas others are likely present as a function of cell lysis occurring during culture (63). We reasoned that the latter group might be higher in autolytic bacteria like GC (13). To analyze the subcellular distribution of identified proteins, a combination of bioinformatics tools was used including PSORTb, CELLO 2.5, and SOSUIGramN (43)(44)(45)(46).…”

Section: Strategy For Rigorous Proteomic Profiling Of the Gc Cell Envmentioning

confidence: 99%

“…The small fraction of known components of the GC cell envelope (outer membrane, periplasm, cytoplasmic membrane) plays a fundamental role in establishing infection by enabling the microbes to adhere to and invade host cells, facilitating nutrient acquisition, host tissue destruction, and suppression of immune responses (3,(13)(14)(15). Further, GC, like many other Gram-negative bacteria, produces membrane vesicles (MVs), which are nano-sized bilayered proteolipids (16).…”

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Quantitative Proteomics of the Neisseria Gonorrhoeae Cell Envelope and Membrane Vesicles for the Discovery of Potential Therapeutic Targets

Zielke

Wierzbicki

Weber

et al. 2014

Molecular & Cellular Proteomics

163

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Neisseria gonorrhoeae (GC) is a human-specific pathogen, and the agent of a sexually transmitted disease, gonorrhea. There is a critical need for new approaches to study and treat GC infections because of the growing threat of multidrug-resistant isolates and the lack of a vaccine. Despite the implied role of the GC cell envelope and membrane vesicles in colonization and infection of human tissues and cell lines, comprehensive studies have not been undertaken to elucidate their constituents. Accordingly, in pursuit of novel molecular therapeutic targets, we have applied isobaric tagging for absolute quantification coupled with liquid chromatography and mass spectrometry for proteome quantitative analyses. Mining the proteome of cell envelopes and native membrane vesicles revealed 533 and 168 common proteins, respectively, in analyzed GC strains FA1090, F62, MS11, and 1291. A total of 22 differentially abundant proteins were discovered including previously unknown proteins. Among those proteins that displayed similar abundance in four GC strains, 34 were found in both cell envelopes and membrane vesicles fractions. Focusing on one of them, a homolog of an outer membrane protein LptD, we demonstrated that its depletion caused loss of GC viability. In addition, we selected for initial characterization six predicted outer membrane proteins with unknown function, which were identified as ubiquitous in the cell envelopes derived from examined GC isolates. These studies entitled a construction of deletion mutants and analyses of their resistance to different chemical probes. Loss of NGO1985, in particular, resulted in dramatically decreased GC viability upon treatment with detergents, polymyxin B, and chloramphenicol, suggesting that this protein functions in the maintenance of the cell envelope permeability barrier. Together, these findings underscore the concept that the cell envelope and membrane vesicles contain crucial, yet under-explored determinants of GC physiology, which may represent promising targets for designing new therapeutic interventions. Molecular &

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“…Some PG fragments, such as the anhydro-muramic-tripeptides of Neisseria and Bordetella species, act as potent toxins of ciliated epithelial cells by inducing inflammatory cytokine production (19). These PG fragments are produced by bacterial PG hydrolases and lytic transglycosylases and play important roles in pathogenesis.…”

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Minimal Peptidoglycan (PG) Turnover in Wild-Type and PG Hydrolase and Cell Division Mutants of Streptococcus pneumoniae D39 Growing Planktonically and in Host-Relevant Biofilms

et al. 2015

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We determined whether there is turnover of the peptidoglycan (PG) cell wall of the ovococcus bacterial pathogen Streptococcus pneumoniae (pneumococcus). Pulse-chase experiments on serotype 2 strain D39 radiolabeled with N-acetylglucosamine revealed little turnover and release of PG breakdown products during growth compared to published reports of PG turnover in Bacillus subtilis. PG dynamics were visualized directly by long-pulse-chase-new-labeling experiments using two colors of fluorescent D-amino acid (FDAA) probes to microscopically detect regions of new PG synthesis. Consistent with minimal PG turnover, hemispherical regions of stable "old" PG persisted in D39 and TIGR4 (serotype 4) cells grown in rich brain heart infusion broth, in D39 cells grown in chemically defined medium containing glucose or galactose as the carbon source, and in D39 cells grown as biofilms on a layer of fixed human epithelial cells. In contrast, B. subtilis exhibited rapid sidewall PG turnover in similar FDAA-labeling experiments. High-performance liquid chromatography (HPLC) analysis of biochemically released peptides from S. pneumoniae PG validated that FDAAs incorporated at low levels into pentamer PG peptides and did not change the overall composition of PG peptides. PG dynamics were also visualized in mutants lacking PG hydrolases that mediate PG remodeling, cell separation, or autolysis and in cells lacking the MapZ and DivIVA division regulators. In all cases, hemispheres of stable old PG were maintained. In PG hydrolase mutants exhibiting aberrant division plane placement, FDAA labeling revealed patches of inert PG at turns and bulge points. We conclude that growing S. pneumoniae cells exhibit minimal PG turnover compared to the PG turnover in rod-shaped cells. IMPORTANCEPG cell walls are unique to eubacteria, and many bacterial species turn over and recycle their PG during growth, stress, colonization, and virulence. Consequently, PG breakdown products serve as signals for bacteria to induce antibiotic resistance and as activators of innate immune responses. S. pneumoniae is a commensal bacterium that colonizes the human nasopharynx and opportunistically causes serious respiratory and invasive diseases. The results presented here demonstrate a distinct demarcation between regions of old PG and regions of new PG synthesis and minimal turnover of PG in S. pneumoniae cells growing in culture or in host-relevant biofilms. These findings suggest that S. pneumoniae minimizes the release of PG breakdown products by turnover, which may contribute to evasion of the innate immune system. P eptidoglycan (PG) biosynthesis and placement are dynamic processes that determine the shapes, sizes, chaining, and resistance to turgor of bacterial cells (1-6). In Gram-positive bacteria, PG also serves as the scaffolding for covalent attachment of surface wall teichoic acid, capsule, and sortase-attached proteins (7-9). The seminal work of Park and Uehara demonstrated that PG is rapidly turned over and the breakdown components recycled in...

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The Lytic Transglycosylases ofNeisseria gonorrhoeae

Cited by 47 publications

References 62 publications

Neisseria gonorrhoeae Crippled Its Peptidoglycan Fragment Permease To Facilitate Toxic Peptidoglycan Monomer Release

Neisseria gonorrhoeae Crippled Its Peptidoglycan Fragment Permease To Facilitate Toxic Peptidoglycan Monomer Release

Quantitative Proteomics of the Neisseria Gonorrhoeae Cell Envelope and Membrane Vesicles for the Discovery of Potential Therapeutic Targets

Minimal Peptidoglycan (PG) Turnover in Wild-Type and PG Hydrolase and Cell Division Mutants of Streptococcus pneumoniae D39 Growing Planktonically and in Host-Relevant Biofilms

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