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S. aureus alpha-toxin monomer binding and heptamer formation in host cell membranes – Do they determine sensitivity of airway epithelial cells toward the toxin?

ABSTRACT: Alpha-toxin (Hla) is a major virulence factor of Staphylococcus aureus (S. aureus) and plays an important role in S. aureus -induced pneumonia. It binds as a monomer to the cell surface of eukaryotic host cells and forms heptameric transmembrane pores. Sensitivities toward the toxin of various types of potential host cells have been shown to vary substantially, and the reasons for these differences are unclear. We used three human model airway epithelial cell lines (16HBE14o-, S9, A549) to correlate cell sensitivity (measured as rate of paracellular gap formation in the cell layers) with Hla monomer binding, presence of the potential Hla receptors ADAM10 or alpha5beta1 integrin, presence of the toxin-stabilizing factor caveolin-1 as well as plasma membrane lipid composition (phosphatidylserine/choline, sphingomyelin). The abundance of ADAM10 correlated best with gap formation or cell sensitivities, respectively, when the three cell types were compared. Caveolin-1 or alpha5beta1 integrin did not correlate with toxin sensitivity. The relative abundance of sphingomyelin in plasma membranes may also be used as a proxi for cellular sensitivity against alpha-toxin as sphingomyelin abundances correlated well with the intensities of alpha-toxin mediated gap formation in the cell layers.

SUBMITTER: Nils Möller

PROVIDER: S-BSST397 | bioimages |

REPOSITORIES: bioimages

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S. aureus alpha-toxin monomer binding and heptamer formation in host cell membranes - Do they determine sensitivity of airway epithelial cells toward the toxin?

Project description:Alpha-toxin (Hla) is a major virulence factor of Staphylococcus aureus (S. aureus) and plays an important role in S. aureus-induced pneumonia. It binds as a monomer to the cell surface of eukaryotic host cells and forms heptameric transmembrane pores. Sensitivities toward the toxin of various types of potential host cells have been shown to vary substantially, and the reasons for these differences are unclear. We used three human model airway epithelial cell lines (16HBE14o-, S9, A549) to correlate cell sensitivity (measured as rate of paracellular gap formation in the cell layers) with Hla monomer binding, presence of the potential Hla receptors ADAM10 or α5β1 integrin, presence of the toxin-stabilizing factor caveolin-1 as well as plasma membrane lipid composition (phosphatidylserine/choline, sphingomyelin). The abundance of ADAM10 correlated best with gap formation or cell sensitivities, respectively, when the three cell types were compared. Caveolin-1 or α5β1 integrin did not correlate with toxin sensitivity. The relative abundance of sphingomyelin in plasma membranes may also be used as a proxi for cellular sensitivity against alpha-toxin as sphingomyelin abundances correlated well with the intensities of alpha-toxin mediated gap formation in the cell layers.

| S-EPMC7259691 | biostudies-literature

Major Determinants of Airway Epithelial Cell Sensitivity to <i>S. aureus</i> Alpha-Toxin: Disposal of Toxin Heptamers by Extracellular Vesicle Formation and Lysosomal Degradation.

Project description:Alpha-toxin is a major virulence factor of Staphylococcus aureus. Monomer binding to host cell membranes results in the formation of heptameric transmembrane pores. Among human model airway epithelial cell lines, A549 cells were most sensitive toward the toxin followed by 16HBE14o- and S9 cells. In this study we investigated the processes of internalization of pore-containing plasma membrane areas as well as potential pathways for heptamer degradation (lysosomal, proteasomal) or disposal (formation of exosomes/micro-vesicles). The abundance of toxin heptamers upon applying an alpha-toxin pulse to the cells declined both in extracts of whole cells and of cellular membranes of S9 cells, but not in those of 16HBE14o- or A549 cells. Comparisons of heptamer degradation rates under inhibition of lysosomal or proteasomal degradation revealed that an important route of heptamer degradation, at least in S9 cells, seems to be the lysosomal pathway, while proteasomal degradation appears to be irrelevant. Exosomes prepared from culture supernatants of toxin-exposed S9 cells contained alpha-toxin as well as low amounts of exosome and micro-vesicle markers. These results indicate that lysosomal degradation of internalized toxin heptamers may be the most important determinant of toxin-resistance of some types of airway epithelial cells.

| S-EPMC7996177 | biostudies-literature

Overexpression of thioredoxin-binding protein 2 increases oxidation sensitivity and apoptosis in human lens epithelial cells.

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Major determinants of airway epithelial cell sensitivity to S. aureus alpha-toxin: Disposition of toxin heptamers by extracellular vesicle formation and lysosomal degradation

Project description:Alpha-toxin is a major virulence factor of Staphylococcus aureus and plays an important role in S. aureus-induced pneumonia. Different sensitivities toward the toxin of various host cell types have been observed. In this study we investigated internalization of pore-containing areas of the plasma membrane in these cell types as well as potential pathways for heptamer degradation (lysosomal, proteasomal) or disposal (formation of exosomes/microvesicles containing toxin pores). Comparisons of heptamer degradation rates under inhibition of lysosomal or proteasomal degradation revealed that an important route of heptamer degradation at least in S9 cells seemed to be the lysosomal pathway while proteasomal degradation did not seem to be relevant. Exosomes prepared from culture supernatants of toxin-exposed S9 cells, contained alpha-toxin as well as low amounts of marker proteins of exosomes and microvesicles. These results indicate that the ability of lysosomal degradation of internalized toxin heptamers may be the most important determinant of toxin-resistance of some types of airway epithelial cells. In this study, we compared the proteomes of rHla treated (90 min), 8 h starvation and, 48 h starvation for the S9 cells by mass spectrometry.

2021-04-20 | PXD023678 | Pride

Appropriate tension sensitivity of α-catenin ensures rounding morphogenesis of epithelial spheroids.

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| S-EPMC10511042 | biostudies-literature

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Project description:Sjögren's syndrome is a chronic autoimmune disorder characterized by inflammation of salivary glands resulting in impaired secretory function. Our present studies indicate that chronic exposure of salivary epithelium to TNF-α and/or IFN-γ alters tight junction integrity, leading to secretory dysfunction. Resolvins of the D-series (RvDs) are endogenous lipid mediators derived from DHA that regulate excessive inflammatory responses leading to resolution and tissue homeostasis. In this study, we addressed the hypothesis that activation of the RvD1 receptor ALX/FPR2 in salivary epithelium prevents and/or resolves the TNF-α-mediated disruption of acinar organization and enhances monolayer formation. Our results indicate that 1) the RvD1 receptor ALX/FPR2 is present in fresh, isolated cells from mouse salivary glands and in cell lines of salivary origin; and 2) the agonist RvD1 (100 ng/ml) abolished tight junction and cytoskeletal disruption caused by TNF-α and enhanced cell migration and polarity in salivary epithelium. These effects were blocked by the ALX/FPR2 antagonist butyloxycarbonyl-Phe-Leu-Phe-Leu-Phe. The ALX/FPR2 receptor signals via modulation of the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathways since, in our study, blocking PI3K activation with LY294002, a potent and selective PI3K inhibitor, prevented RvD1-induced cell migration. Furthermore, Akt gene silencing with the corresponding siRNA almost completely blocked the ability of Par-C10 cells to migrate. Our findings suggest that RvD1 receptor activation promotes resolution of inflammation and tissue repair in salivary epithelium, which may have relevance in the restoration of salivary gland dysfunction associated with Sjögren's syndrome.

| S-EPMC3361948 | biostudies-literature

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Project description:Background and aimsThe gastrointestinal (GI) tract extracts nutrients from ingested meals while protecting the organism from infectious agents frequently present in meals. Consequently, most animals conduct the entire digestive process within the GI tract while keeping the luminal contents entirely outside the body, separated by the tightly sealed GI epithelium. Therefore, like the skin and oral cavity, the GI tract must sense the chemical and physical properties of the its external interface to optimize its function. Specialized sensory enteroendocrine cells (EECs) in GI epithelium interact intimately with luminal contents. A subpopulation of EECs express the mechanically gated ion channel Piezo2 and are developmentally and functionally like the skin's touch sensor- the Merkel cell. We hypothesized that Piezo2+ EECs endow the gut with intrinsic tactile sensitivity.MethodsWe generated transgenic mouse models with optogenetic activators in EECs and Piezo2 conditional knockouts. We used a range of reference standard and novel techniques from single cells to living animals, including single-cell RNA sequencing and opto-electrophysiology, opto-organ baths with luminal shear forces, and in vivo studies that assayed GI transit while manipulating the physical properties of luminal contents.ResultsPiezo2+ EECs have transcriptomic features of synaptically connected, mechanosensory epithelial cells. EEC activation by optogenetics and forces led to Piezo2-dependent alterations in colonic propagating contractions driven by intrinsic circuitry, with Piezo2+ EECs detecting the small luminal forces and physical properties of the luminal contents to regulate transit times in the small and large bowel.ConclusionsThe GI tract has intrinsic tactile sensitivity that depends on Piezo2+ EECs and allows it to detect luminal forces and physical properties of luminal contents to modulate physiology.

| S-EPMC8792331 | biostudies-literature

Epithelial Sodium Channel Alpha Subunit (αENaC) Is Associated with Inverse Salt Sensitivity of Blood Pressure.

Project description:Salt sensitivity of blood pressure (BP) refers to an increase in BP following an increase in dietary salt, which is associated with increased incidence of cardiovascular disease and early death. However, decreased sodium intake also increases mortality and morbidity. Inverse salt sensitivity (ISS), defined as a paradoxical increase in BP on a low-salt diet, about 11% of the population, may be the cause of this phenomenon. The epithelial sodium channel (ENaC) is a major regulator of sodium reabsorption in the kidney. In this study, human renal tubular epithelial cells (hRTC) were cultured from the urine of phenotyped salt study participants. αENaC expression was significantly lower in ISS than salt resistant (SR) hRTC, while ENaC-like channel activity was dramatically increased by trypsin treatment in ISS cells analyzed by patch clamp. αENaC expression was also decreased under high-salt treatment and increased by aldosterone treatment in ISS cells. Moreover, the αENaC variant, rs4764586, was more prevalent in ISS. In summary, αENaC may be associated with ISS hypertension on low salt. These findings may contribute to understanding the mechanisms of ISS and low salt effect on morbidity and mortality.

| S-EPMC9138231 | biostudies-literature

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