title: Staphylococcal scalded skin syndrome: exfoliative toxin A (ETA) induces serine protease activity when combined with A431 cells.
abstract: Staphylococcal scalded skin syndrome is the term used for a spectrum of primarily neonatal blistering skin diseases caused by the exfoliative toxins, ETA and ETB, of Staphylococcus aureus. Despite 25 y of research, the toxins' mechanism of action is still poorly understood, although evidence suggests that they may act as serine proteases. In this study, 0.1 mg purified ETA isolated from a baby with pemphigus neonatorum was incubated with A431 cells (a human squamous cell line) at 37 degrees C for 8, 24 and 48 h and the supernatant tested for protease activity using azocasein as a non-specific substrate. Phosphate-buffered saline was also incubated as negative control. Incubation of ETA with A431 cells for 48 h resulted in a four-fold increase in supernatant azocaseinolytic activity compared with buffer and cells, ETA alone and buffer alone (p < 0.001). Furthermore, this proteolytic activity was inhibited by PMSF (p < 0.001), a specific serine protease inhibitor. These results provide further evidence for the role of the exfoliative toxins as serine proteases. Furthermore, the A431 cell assay provides a simpler, quicker, cheaper and more acceptable alternative to neonatal mouse epidermis to study the mechanism of action of the exfoliative toxins.
authors.affiliation: Division of Biomolecular Sciences, Kings College, London, UK. drshamez@aol.com
authors.forename: S
authors.initials: S
authors.lastname: Ladhani
authors.forename: S M
authors.initials: SM
authors.lastname: Poston
authors.forename: C L
authors.initials: CL
authors.lastname: Joannou
authors.forename: R W
authors.initials: RW
authors.lastname: Evans
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002364:Caseins / Q000378:metabolism; D018929:Cell Culture Techniques; D002460:Cell Line; D010450:Endopeptidases / Q000378:metabolism; D004768:Enterotoxins / Q000494:pharmacology*; D004817:Epidermis / Q000187:drug effects / Q000201:enzymology; D005083:Exfoliatins / Q000494:pharmacology*; D006801:Humans; D051379:Mice; D010447:Peptide Hydrolases / Q000378:metabolism; D012697:Serine Endopeptidases / Q000494:pharmacology*; D013206:Staphylococcal Scalded Skin Syndrome / Q000201:enzymology*; D013211:Staphylococcus aureus; D013329:Structure-Activity Relationship
chemical_list: D002364:Caseins; D004768:Enterotoxins; D005083:Exfoliatins; D010450:Endopeptidases; D010447:Peptide Hydrolases; D012697:Serine Endopeptidases