Staphylococcus aureus α-Toxin Induces Actin Filament Remodeling in Human Airway Epithelial Model Cells

Abstract

Exposure of cultured human airway epithelial model cells (16HBE14o-, S9) to Staphylococcus aureus α-toxin (hemolysin A, Hla) induces changes in cell morphology and cell layer integrity that are due to the inability of the cells to maintain stable cell-cell or focal contacts and to properly organize their actin cytoskeletons. The aim of this study was to identify Hla-activated signaling pathways involved in regulating the phosphorylation level of the actin-depolymerizing factor cofilin. We used recombinant wild-type hemolysin A (rHla) and a variant of Hla (rHla-H35L) that is unable to form functional transmembrane pores to treat immortalized human airway epithelial cells (16HBE14o-, S9) as well as freshly isolated human nasal tissue. Our results indicate that rHla-mediated changes in cofilin phosphorylation require the formation of functional Hla pores in the host cell membrane. Formation of functional transmembrane pores induced hypophosphorylation of cofilin at Ser3, which was mediated by rHla-induced attenuation of p21-activated protein kinase and LIM kinase activities. Because dephosphorylation of pSer3-cofilin results in activation of this actin-depolymerizing factor, treatment of cells with rHla resulted in loss of actin stress fibers from the cells and destabilization of cell shape followed by the appearance of paracellular gaps in the cell layers. Activation of protein kinase A or activation of small GTPases (Rho, Rac, Cdc42) do not seem to be involved in this response.

Identification of biomarkers in common chronic lung diseases by co-expression networks and drug-target interactions analysis

“…For example, the genes of the brown module are significantly associated with the biological pathways of Tuberculosis, Staphylococcus aureus infection, Leishmaniasis, Pertussis, and Legionellosis. All these pathways play critical roles in infections and remodeling in COPD (Carette et al 2018;Tsenova et al 2014;Ziesemer et al 2018;Sabulski et al 2017). In the brown module, eight hub DEGs including CYp27A1, GM2A, LGAL59, SPI1, PARVG, LOC644189, NLRC4, CD300LF are considered as the novel genes in the COPD.…”

Das alpha‐Toxin von Staphylococcus aureus

“…Die Zellen zeigen auch eine Einschränkung der Fähigkeit, stabile fokale Kontakte zwischen Zellmembran und der extrazellulären Matrix zu bilden . Außerdem findet unter Hla‐Einwirkung eine massive Reorganisation des Aktin‐Zytoskeletts statt . Insgesamt führt dies zu deutlichen Änderungen der Zellform und der Ausbildung ▸ parazellulärer Lücken im Zellverband (Abbildung ).…”

“…Die durch Hla‐Einwirkung verursachte Lösung der Zell‐Zell‐Verbindungen (adherence junctions) erfolgt vermutlich durch eine Ca 2+ ‐vermittelte Aktivierung der Metalloprotease ADAM10 . Die Unfähigkeit, stabile ▸ fokale Kontakte zur Zellunterlage auszubilden und die Reorganisation des Aktin‐Zytoskeletts gehen auf die Hla‐vermittelte Intensivierung der Signaltransduktion durch die fokale Adhäsionskinase (FAK) sowie auf eine Hemmung der Aktivität der LIM‐Kinase zurück. In ruhenden Epithelzellen phosphoryliert die LIM‐Kinase den Aktin‐depolymerisierenden Faktor Cofilin und inaktiviert ihn dadurch, so dass die Aktin‐Stressfasern, die die Zellform stabilisieren, vor der abbauenden Aktivität des Cofilins geschützt sind.…”

“…Diese Prozesse sind vermutlich wesentlich für die Veränderung der Zellform der Atemwegsepithelzellen unter Hla‐Einwirkung und die Bildung parazellulärer Lücken im Zellverband verantwortlich (Abbildung ). Es ist bisher noch unklar, welche intrazellulären Signalwege an der Hla‐vermittelten Hypophosphorylierung der LIM‐Kinase beteiligt sind .…”

Microbiota Composition and the Integration of Exogenous and Endogenous Signals in Reactive Nasal Inflammation

“…That tissue remodeling and polyp formation may be favored in a dysbiotic microenvironment is inferred in a number of studies showing increased S. aureus colonization in the nasal cavities of patients with polyposis [ 164 ]. Recent work has shown that α -toxin, one of the major S. aureus toxins, can substantially contribute to airway remodeling via a combined effect on the epithelial cell cytoskeleton and endothelial TJ integrity, leading, respectively, to altered morphology and edema [ 165 , 166 ]. However, the main mechanism this far ascertained by which S. aureus may induce or favor nasal polyp formation is the production of such superantigens as staphylococcal enterotoxins (SAE) [ 7 , 167 ].…”