Current Perspective on the Membrane-Damaging Action of Thermostable Direct Hemolysin, an Atypical Bacterial Pore-forming Toxin

Frontiers in Molecular Biosciences ◽

10.3389/fmolb.2021.717147 ◽

2021 ◽

Vol 8 ◽

Author(s):

Pratima Verma ◽

Kausik Chattopadhyay

Keyword(s):

Vibrio Parahaemolyticus ◽

Pore Formation ◽

Bacterial Pathogen ◽

Structural Similarity ◽

Sea Anemones ◽

Membrane Pore ◽

Current Perspective ◽

Thermostable Direct Hemolysin ◽

Specific Membrane

Thermostable direct hemolysin (TDH) is the major virulence determinant of the gastroenteric bacterial pathogen Vibrio parahaemolyticus. TDH is a membrane-damaging pore-forming toxin (PFT). TDH shares remarkable structural similarity with the actinoporin family of eukaryotic PFTs produced by the sea anemones. Unlike most of the PFTs, it exists as tetramer in solution, and such assembly state is crucial for its functionality. Although the structure of the tetrameric assembly of TDH in solution is known, membrane pore structure is not available yet. Also, the specific membrane-interaction mechanisms of TDH, and the exact role of any receptor(s) in such process, still remain unclear. In this mini review, we discuss some of the unique structural and physicochemical properties of TDH, and their implications for the membrane-damaging action of the toxin. We also present our current understanding regarding the membrane pore-formation mechanism of this atypical bacterial PFT.

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Association of Vibrio parahaemolyticus Thermostable Direct Hemolysin with Lipid Rafts Is Essential for Cytotoxicity but Not Hemolytic Activity

Infection and Immunity ◽

10.1128/iai.00946-09 ◽

2009 ◽

Vol 78 (2) ◽

pp. 603-610 ◽

Cited By ~ 38

Author(s):

Shigeaki Matsuda ◽

Toshio Kodama ◽

Natsumi Okada ◽

Kanna Okayama ◽

Takeshi Honda ◽

...

Keyword(s):

Lipid Rafts ◽

Hemolytic Activity ◽

Vibrio Parahaemolyticus ◽

Cultured Cells ◽

Direct Interaction ◽

Caveolin 1 ◽

Marker Proteins ◽

Thermostable Direct Hemolysin ◽

Target Molecules

ABSTRACT Thermostable direct hemolysin (TDH), a major virulence factor of Vibrio parahaemolyticus, induces cytotoxicity in cultured cells. However, the mechanism of TDH's cytotoxic effect including its target molecules on the plasma membrane of eukaryotic cells remains unclear. In this study, we identified the role of lipid rafts, cholesterol- and sphingolipid-enriched microdomains, in TDH cytotoxicity. Treatment of cells with methyl-β-cyclodextrin (MβCD), a raft-disrupting agent, inhibited TDH cytotoxicity. TDH was associated with detergent-resistant membranes (DRMs), and MβCD eliminated this association. In contrast, there was no such association between a nontoxic TDH mutant and DRMs. The disruption of lipid rafts neither affected hemolysis nor inhibited Ca2+ influx into HeLa cells induced by TDH. These findings indicate that the cytotoxicity but not the hemolytic activity of TDH is dependent on lipid rafts. The exogenous and endogenous depletion of cellular sphingomyelin also prevented TDH cytotoxicity, but a direct interaction between TDH and sphingomyelin was not detected with either a lipid overlay assay or a liposome absorption test. Treatment with sphingomyelinase (SMase) at 100 mU/ml disrupted the association of TDH with DRMs but did not affect the localization of lipid raft marker proteins (caveolin-1 and flotillin-1) with DRMs. These results suggest that sphingomyelin is important for the association of TDH with lipid rafts but is not a molecular target of TDH. We hypothesize that TDH may target a certain group of rafts that are sensitive to SMase at a certain concentration, which does not affect other types of rafts.

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Hydrophilic nanoparticles that kill bacteria while sparing mammalian cells reveal the antibiotic role of nanostructures

Nature Communications ◽

10.1038/s41467-021-27193-9 ◽

2022 ◽

Vol 13 (1) ◽

Author(s):

Yunjiang Jiang ◽

Wan Zheng ◽

Keith Tran ◽

Elizabeth Kamilar ◽

Jitender Bariwal ◽

...

Keyword(s):

Polymer Brushes ◽

Mammalian Cells ◽

Pore Formation ◽

Multidrug Resistant ◽

Membrane Pore ◽

Threshold Size ◽

Resistant Strains ◽

Viable Approach ◽

Nanoparticle Sizes

AbstractTo dissect the antibiotic role of nanostructures from chemical moieties belligerent to both bacterial and mammalian cells, here we show the antimicrobial activity and cytotoxicity of nanoparticle-pinched polymer brushes (NPPBs) consisting of chemically inert silica nanospheres of systematically varied diameters covalently grafted with hydrophilic polymer brushes that are non-toxic and non-bactericidal. Assembly of the hydrophilic polymers into nanostructured NPPBs doesn’t alter their amicability with mammalian cells, but it incurs a transformation of their antimicrobial potential against bacteria, including clinical multidrug-resistant strains, that depends critically on the nanoparticle sizes. The acquired antimicrobial potency intensifies with small nanoparticles but subsides quickly with large ones. We identify a threshold size (dsilica ~ 50 nm) only beneath which NPPBs remodel bacteria-mimicking membrane into 2D columnar phase, the epitome of membrane pore formation. This study illuminates nanoengineering as a viable approach to develop nanoantibiotics that kill bacteria upon contact yet remain nontoxic when engulfed by mammalian cells.

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Faculty Opinions recommendation of Development and evaluation of a rapid, simple, and sensitive immunochromatographic assay to detect thermostable direct hemolysin produced by Vibrio parahaemolyticus in enrichment cultures of stool specimens.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1057716.509629 ◽

2006 ◽

Author(s):

Nitaya Thammapalerd

Keyword(s):

Vibrio Parahaemolyticus ◽

Immunochromatographic Assay ◽

Enrichment Cultures ◽

Thermostable Direct Hemolysin ◽

Stool Specimens

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ADP-ribosylation of the specific membrane protein by islet-activating protein, pertussis toxin, associated with inhibition of a chemotactic peptide-induced arachidonate release in neutrophils. A possible role of the toxin substrate in Ca2+-mobilizing biosignaling.

Journal of Biological Chemistry ◽

10.1016/s0021-9258(18)89826-x ◽

1984 ◽

Vol 259 (22) ◽

pp. 13863-13871 ◽

Cited By ~ 20

Author(s):

F Okajima ◽

M Ui

Keyword(s):

Membrane Protein ◽

Pertussis Toxin ◽

Chemotactic Peptide ◽

Adp Ribosylation ◽

Arachidonate Release ◽

Specific Membrane

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Amino Acid Transporter LAT1 (SLC7A5) Mediates MeHg-Induced Oxidative Stress Defense in the Human Placental Cell Line HTR-8/SVneo

International Journal of Molecular Sciences ◽

10.3390/ijms22041707 ◽

2021 ◽

Vol 22 (4) ◽

pp. 1707

Author(s):

Sebastian Granitzer ◽

Raimund Widhalm ◽

Martin Forsthuber ◽

Isabella Ellinger ◽

Gernot Desoye ◽

...

Keyword(s):

Oxidative Stress ◽

Amino Acid ◽

De Novo ◽

Structural Similarity ◽

Amino Acid Transporter ◽

Cell Number ◽

Mehg Exposure ◽

Acid Transporter ◽

And Oxidative Stress

The placental barrier can protect the fetus from contact with harmful substances. The potent neurotoxin methylmercury (MeHg), however, is very efficiently transported across the placenta. Our previous data suggested that L-type amino acid transporter (LAT)1 is involved in placental MeHg uptake, accepting MeHg-L-cysteine conjugates as substrate due to structural similarity to methionine. The aim of the present study was to investigate the antioxidant defense of placental cells to MeHg exposure and the role of LAT1 in this response. When trophoblast-derived HTR-8/SVneo cells were LAT1 depleted by siRNA-mediated knockdown, they accumulated less MeHg. However, they were more susceptible to MeHg-induced toxicity. This was evidenced in decreased cell viability at a usually noncytotoxic concentration of 0.03 µM MeHg (~6 µg/L). Treatment with ≥0.3 µM MeHg increased cytotoxicity, apoptosis rate, and oxidative stress of HTR-8/SVneo cells. These effects were enhanced under LAT1 knockdown. Reduced cell number was seen when MeHg-exposed cells were cultured in medium low in cysteine, a constituent of the tripeptide glutathione (GSH). Because LAT1-deficient HTR-8/SVneo cells have lower GSH levels than control cells (independent of MeHg treatment), we conclude that LAT1 is essential for de novo synthesis of GSH, required to counteract oxidative stress. Genetic predisposition to decreased LAT1 function combined with MeHg exposure could increase the risk of placental damage.

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