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Pore forming toxins

Yanting Wang, Wenxian Lan, Zhenzhen Yan, Jing Gao, Xinlian Liu, Sheng Wang, Xiying Guo, Chunxi Wang, Hu Zhou, Jiuping Ding, Chunyang Cao
Large-conductance Ca2+ - and voltage-dependent K+ (BK) channels display diverse biological functions while their pore-forming α subunit is coded by a single Slo1 gene. The variety of BK channels is correlated with the effects of BKα coexpression with auxiliary β (β1-β4) subunits, as well as newly defined γ subunits. Charybdotoxin (ChTX) blocks BK channel through physically occluding the K+ -conduction pore. Human brain enriched β4 subunit (hβ4) alters the conductance-voltage curve, slows activation and deactivation time courses of BK channels...
March 15, 2018: Scientific Reports
Krishnan Raghunathan, Nora J Foegeding, Anne M Campbell, Timothy L Cover, Melanie D Ohi, Anne K Kenworthy
Helicobacter pylori , a Gram-negative bacterium, is a well-known risk factor for gastric cancer. H. pylori vacuolating cytotoxin A (VacA) is a secreted pore-forming toxin that induces a wide range of cellular responses. Like many other bacterial toxins, VacA has been hypothesized to utilize lipid rafts to gain entry into host cells. Here, we use Giant Plasma Membrane Vesicles (GPMVs) as a model system to understand the preferential partitioning of VacA into lipid rafts. We show that a wild-type toxin predominantly associates with the raft phase...
March 12, 2018: Infection and Immunity
Srujan Kumar Dondapati, Doreen A Wüstenhagen, Eckhard Strauch, Stefan Kubick
The pore forming characteristic of TDH1 and TDH2 variants of thermostable direct hemolysin (TDH), a major toxin involved in the pathogenesis of Vibrio parahaemolyticus , was studied on a planar lipid bilayer painted over individual picoliter cavities containing microelectrodes assembled in a multiarray. Both proteins formed pores upon insertion into the lipid bilayer which was shown as a shift in the conductance from the baseline current. TDH2 protein was able to produce stable currents and the currents were influenced by external factors like concentration, type of salt and voltage...
February 2018: Engineering in Life Sciences
Monifa A Fahie, Lucas Liang, Alzira R Avelino, Bach Pham, Patanachai Limpikirati, Richard W Vachet, Min Chen
Cytolysin A (ClyA) is a water-soluble alpha pore-forming toxin that assembles to form an oligomeric pore on host cell membranes. The ClyA monomer possesses an α-helical bundle with a β-sheet subdomain (the β-tongue) previously believed to be critical for pore assembly and/or insertion. Oligomerization of ClyA pores transforms the β-tongue into a helix-turn-helix that embeds into the lipid bilayer. Here, we show that mutations of the β-tongue did not prevent oligomerization or transmembrane insertion. Instead, β-tongue substitution mutants yielded pores with decreased conductance while a deletion mutation resulted in pores that rapidly closed following membrane association...
February 28, 2018: Scientific Reports
Yongning Lu, Amir Rafiq, Zhengguo Zhang, Ferial Aslani, Monika Fijak, Tao Lei, Ming Wang, Sanjeev Kumar, Jörg Klug, Martin Bergmann, Trinad Chakraborty, Andreas Meinhardt, Sudhanshu Bhushan
Uropathogenic Escherichia coli (UPEC) is the most common cause of urinary tract infections. In this study, UPEC strains harboring hemolysin A (HlyA) did not induce programmed cell death pathways by the activation of caspases. Instead, the UPEC pore-forming toxin HlyA triggered an increase in mitochondrial Ca2+ levels and manipulated mitochondrial dynamics by causing fragmentation of the mitochondrial network. Alterations in mitochondrial dynamics resulted in severe impairment of mitochondrial functions by loss of membrane potential, increase in ROS production, and ATP depletion...
February 28, 2018: FASEB Journal: Official Publication of the Federation of American Societies for Experimental Biology
K K Fursova, M P Shchannikova, I V Loskutova, A O Shepelyakovskaya, A G Laman, A M Boutanaev, S L Sokolov, O A Artem'eva, D A Nikanova, N A Zinovieva, F A Brovko
Mastitis, a major veterinary problem widespread in many regions, is caused mainly by Staphylococcus spp. However, there is no current reliable information about the role of Staphylococcus aureus and their toxins in the development of mastitis in cows in the territory of the Russian Federation. The aim of this investigation was to determine the profile of exotoxins of S. aureus from cow milk from farms of Central Russia. A total of 60 isolates of S. aureus were obtained from milk samples of cows with the subclinical form of mastitis...
February 21, 2018: Journal of Dairy Science
Zhao Peng, Miyu Takeshita, Nao Shibata, Hideaki Tada, Yoshikazu Tanaka, Jun Kaneko
Staphylococcus aureus bi-component pore-forming toxins consist of S- and F-components, and form hetero-octameric beta-barrel pores on target blood cell membranes. Among them, γ-hemolysin (Hlg2 and LukF) and LukED (LukE and LukD) possess hemolytic activity, whereas the Panton -Valentine leukocidin (LukS-PV and LukF-PV) does not lyse human erythrocytes.Here, we focused on four loop structures in the rim domain of S-component, namely loops -1, -2, -3, and -4, and found that replacement of loop-4 in both Hlg2 and LukE with that of LukS-PV abolished their hemolytic activity...
February 17, 2018: Journal of Biochemistry
Jun-Seob Kim, Allen B Schantz, Sooyeon Song, Manish Kumar, Thomas K Wood
GhoT is a bacterial toxin of the type V toxin/antitoxin system that allows Escherichia coli to reduce its metabolism in response to oxidative and bile stress. GhoT functions by increasing membrane permeability and reducing both ATP levels and the proton motive force. However, how GhoT damages the inner membrane has not been elucidated. Here we investigated how GhoT damages membranes by studying its interaction with lipid bilayers and determined that GhoT does not cause macroscopic disruption of the lipid bilayer to increase membrane permeability to the dye carboxyfluorescein...
February 19, 2018: Biochemical and Biophysical Research Communications
Reema Kathuria, Kausik Chattopadhyay
Vibrio cholerae cytolysin (VCC) is a membrane-damaging protein toxin with potent cytolytic/cytotoxic activity against wide range of eukaryotic cells. VCC is a β-barrel pore-forming toxin (β-PFT), and it inflicts damage to the target cell membranes by forming transmembrane heptameric β-barrel pores. To exert pore-forming activity, VCC must bind to the cell membranes in an efficient manner. Efficient interaction with the cell membranes is an essential pre-requisite to trigger subsequent structural/conformational and organizational changes in the toxin molecules leading toward formation of the transmembrane oligomeric β-barrel pores...
February 22, 2018: IUBMB Life
Primoz Knap, Toma Tebaldi, Francesca Di Leva, Marta Biagioli, Mauro Dalla Serra, Gabriella Viero
Pathogenic bacteria produce powerful virulent factors, such as pore-forming toxins, that promote their survival and cause serious damage to the host. Host cells reply to membrane stresses and ionic imbalance by modifying gene expression at the epigenetic, transcriptional and translational level, to recover from the toxin attack. The fact that the majority of the human transcriptome encodes for non-coding RNAs (ncRNAs) raises the question: do host cells deploy non-coding transcripts to rapidly control the most energy-consuming process in cells-i...
November 3, 2017: Toxins
Kaitlyn D LaCourse, S Brook Peterson, Hemantha D Kulasekara, Matthew C Radey, Jungyun Kim, Joseph D Mougous
Bacteria in polymicrobial habitats contend with a persistent barrage of competitors, often under rapidly changing environmental conditions1 . The direct antagonism of competitor cells is thus an important bacterial survival strategy2 . Towards this end, many bacterial species employ an arsenal of antimicrobial effectors with multiple activities; however, the benefits conferred by the simultaneous deployment of diverse toxins are unknown. Here we show that the multiple effectors delivered to competitor bacteria by the type VI secretion system (T6SS) of Pseudomonas aeruginosa display conditional efficacy and act synergistically...
February 19, 2018: Nature Microbiology
Carmen Soto, Gretchen Bergado, Rancés Blanco, Tania Griñán, Hermis Rodríguez, Uris Ros, Fabiola Pazos, María Eliana Lanio, Ana María Hernández, Carlos Álvarez
Sticholysin II (StII) is a pore-forming toxin of biomedical interest that belongs to the actinoporin protein family. Sticholysins are currently under examination as an active immunomodulating component of a vaccinal platform against tumoral cells and as a key element of a nucleic acids delivery system to cell cytosol. These proteins form pores in the plasma membrane leading to ion imbalance and cell lysis. However, the intracellular mechanisms triggered by actinoporins upon binding to membranes and its consequences for cell death are barely understood...
February 13, 2018: Biochimie
Yijie Chen, Mengchun Chen, Yue Zhang, Joo Hee Lee, Tamara Escajadillo, Hua Gong, Ronnie H Fang, Weiwei Gao, Victor Nizet, Liangfang Zhang
Neutralization of bacterial toxins has become a compelling approach to treating bacterial infections as it may pose less selective pressure for the development of bacterial resistance. Currently, the majority of toxin neutralization platforms act by targeting the molecular structure of the toxin, which requires toxin identification and customized design for different diseases. Therefore, their development has been challenged by the enormous number and complexity of bacterial toxins. Herein, biomimetic toxin nanosponges are formulated by coating membranes of human red blood cells (hRBCs) onto polymeric nanoparticles, which act as a toxin decoy to absorb and neutralize a broad-spectrum of hemolytic toxins regardless of their molecular structure...
February 13, 2018: Advanced Healthcare Materials
Swastik De, Katherine Kaus, Shada Sinclair, Brandon C Case, Rich Olson
Vibrio cholerae is an aquatic gram-negative microbe responsible for cholera, a pandemic disease causing life-threatening diarrheal outbreaks in populations with limited access to health care. Like most pathogenic bacteria, V. cholerae secretes virulence factors to assist colonization of human hosts, several of which bind carbohydrate receptors found on cell-surfaces. Understanding how pathogenic virulence proteins specifically target host cells is important for the development of treatment strategies to fight bacterial infections...
February 12, 2018: PLoS Pathogens
Isaac P Thomsen
No abstract text is available yet for this article.
February 6, 2018: Virulence
Laurent Dortet, Charlotte Lombardi, François Cretin, Andréa Dessen, Alain Filloux
Recent studies highlight that bacterial pathogens can reprogram target cells by influencing epigenetic factors. The type III secretion system (T3SS) is a bacterial nanomachine that resembles a syringe on the bacterial surface. The T3SS 'needle' delivers translocon proteins into eukaryotic cell membranes, subsequently allowing injection of bacterial effectors into the cytosol. Here we show that Pseudomonas aeruginosa induces early T3SS-dependent dephosphorylation and deacetylation of histone H3 in eukaryotic cells...
February 5, 2018: Nature Microbiology
Zhilin Yang, Heejun Choi, James C Weisshaar
The permeabilization of model lipid bilayers by cationic peptides has been studied extensively over decades, with the bee-sting toxin melittin perhaps serving as the canonical example. However, the relevance of these studies to the permeabilization of real bacterial membranes by antimicrobial peptides remains uncertain. Here, we employ single-cell fluorescence microscopy in a detailed study of the interactions of melittin with the outer membrane (OM) and the cytoplasmic membrane (CM) of live Escherichia coli...
January 23, 2018: Biophysical Journal
Sarah C Pearce, Arwa Al-Jawadi, Kunihiro Kishida, Shiyan Yu, Madeleine Hu, Luke F Fritzky, Karen L Edelblum, Nan Gao, Ronaldo P Ferraris
BACKGROUND: Mammalian small intestinal tight junctions (TJ) link epithelial cells to one another and function as a permselective barrier, strictly modulating the passage of ions and macromolecules through the pore and leak pathways, respectively, thereby preventing the absorption of harmful compounds and microbes while allowing regulated transport of nutrients and electrolytes. Small intestinal epithelial permeability is ascribed primarily to the properties of TJs between adjoining enterocytes (ENTs), because there is almost no information on TJ composition and the paracellular permeability of nonenterocyte cell types that constitute a small but significant fraction of the intestinal epithelia...
February 1, 2018: BMC Biology
Heather Miller, Wenxia Song
B-lymphocytes have the ability to repair their plasma membranes following injury, such as by bacterial cholesterol-dependent cytolysins. The repair process includes the removal of the pore from the inflicted region of the plasma membrane via lipid raft-mediated internalization. Lipid rafts are critical for B cell receptor (BCR) activation. Cholesterol-dependent pore forming bacterial toxins provide a useful tool for examining the role of lipid rafts in B cell activation and the underlying cellular mechanisms...
2018: Methods in Molecular Biology
Masataka Murakami, Fumi Kano, Masayuki Murata
Cell-based assays have become increasingly important in the preclinical studies for biopharmaceutical products such as specialty peptides, which are of interest owing to their high substrate specificity. However, many of the latter are membrane impermeable and must be physically introduced into cells to evaluate their intracellular activities. We previously developed a "cell-resealing technique" that exploited the temperature-dependent pore-forming activity of the streptococcal toxin, streptolysin O (SLO), that enabled us to introduce various molecules into cells for evaluation of their intracellular activities...
January 31, 2018: Scientific Reports
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